SYNTHESIS OF METAL OXIDESprr.hec.gov.pk/jspui/bitstream/123456789/8161/1/Inam...SYNTHESIS OF METAL OXIDES NANOPHOTOCATALYST FOR WASTE WATER TREATMENT By INAM ULLAH M. Phil (UAF) A

SYNTHESIS OF METAL OXIDES

NANOPHOTOCATALYST FOR WASTE

WATER TREATMENT

By

INAM ULLAH M. Phil (UAF)

A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE

REQUIREMENTS FOR THE DEGREE OF

DOCTOR OF PHILOSOPHY

IN

CHEMISTRY

DEPARTMENT OF CHEMISTRY

FACULTY OF SCIENCES

UNIVERSITY OF AGRICULTURE, FAISALABAD

PAKISTAN

2017

Declaration

I hereby declare that the contents of the thesis “Synthesis of Metal Oxides

Nanophotocatalyst for Waste Water Treatment” are the product of my own research

and no part has been occupied from any published sources (except the references,

standard mathematical or genetic model/equations/formula/ protocol etc). I further

declare that this work has not been submitted for the award of any other

diploma/degree. The university may take action if the information provided is found

inaccurate at any stage. In case of any default, the scholar will be proceeded against as

per HEC plagiarism policy.

––––––––––––––––

INAM ULLAH

2006-ag-362

M.Phil. Chemistry, UAF

T o ,

The Controller of Examinations,

University of Agriculture,

Faisalabad.

“We, the Supervisory Committee, certify that the contents and form of thesis

submitted by Mr. INAM ULLAH, Reg. No. 2006-ag-362, have been found satisfactory

and recommend that it be processed for evaluation, by the External Examiner(s) for

the award of degree”.

Supervisory Committee

1. Chairman __________________________

(Dr. Shaukat Ali)

2. Member __________________________

(Dr. Muhammad Asif Hanif)

3. Member __________________________

(Dr. Muhammad Anjum Zia)

I want to consecrate this humble effort to the gleaming tower of knowledge

Hazrat Muhammad

(May Peace and Blessings of Allah be upon Him)

&

My Affectionate Parents

Whose esteemed love enabled me to get the success and whose hearts are

always beating to wish for me maximum felicity in life.

ACKNOWLEDGEMENT

All praises to Almighty ALLAH, the creator, dominant, self-existing and sustainer, who enabled me

to accomplish this project and all respect is for his last Prophet MUHAMMAD (Peace and Blessing

of Allah Be upon Him) who is forever a torch of guidance and knowledge in our life.

I pay my humble gratitude to my worthy supervisor Dr. Shaukat Ali, Assistant Professor, Dept. of

Chemistry, University of Agriculture Faisalabad for his absorbing attitude, constant guidance, timely

suggestions, inspiration and encouragement throughout my studies.

I am greatly indebted to Dr. Muhammah Asif Hanif and Dr. Muhammad Anjum Zia for their co-

operation, valuable suggestions and guidance during my research and compilation of my thesis. I am

thankful to Dr. Lizbeth Grondahl, School of Chemistry and Molecular Biosciences, University Of

Queensland, Australia for her kind guidance and research assistance towards completing a part of my

Ph. D. research work in Australia.

I offer my cordial and profound thanks to Prof. Dr. Haq Nawaz Bhatti, Chairman, Dept. of

Chemistry, University of Agriculture Faisalabad.

Special thanks are extended to Muhammad Idrees Jilani, Asif Javid Bhatti, Waqar Azeem, Mirza

Ikram and Rana Shamshad Sahib for their prayers, moral support and sincere suggestions. Special

thanks are due to my all lab fellows for their friendly behavior and co-operation during research work.

Words always seem to shallow whenever it comes to my dear and loving Father. I am absolutely

nothing without his encouragement and especially his prayers. My appreciation and great thanks are

extended to my beloved wife Dr. Sana Sadaf, brothers and sisters for their moral support and prayers.

I want to pay thanks for School of Chemistry and Molecular Biosciences, University Of Queensland,

Australia and Centre for Microscopy and Microanalysis, The University of Queensland node of the

Australian Microscopy and Microanalysis Research Facility (AMMRF) for providing me valuable

facilities. Last but not the least thanks are extended to Higher Education Commission of Pakistan for

their financial support during this project.

INAM ULLAH

.

vii

CONTENTS

Chapter No. TITLE Page No.

1 INTRODUCTION 1

2 REVIEW OF LITERATURE 9

3 MATERIALS AND METHODS 28

4 RESULTS AND DISCUSSION 44

5 SUMMARY 139

LITERATURE CITED 141

viii

Table of contents

Chapter

No.

Title Page No.

Chapter 1 Introduction 1

Chapter 2 Review of literature 9

Chapter 3 Materials And Methods 28

3.1 Apparatus and Chemicals 28

3.1.1 Apparatus 28

3.1.2 Chemicals 28

3.2 Instruments 29

3.3 Chemical co-precipitation 30

3.3.1 Co-precipitation by mechanical stirring 30

3.3.2 Co-precipitation by ultra-sonic assisted mechanical stirring 30

3.4 Synthesis of (Al2O3)1-x(ZnO)xFe2O3 31

3.5 Synthesis of (ZrO2)1-x(ZnO)xFe2O3 32

3.6 X-Ray Diffraction Analysis 33

3.7 Scanning Electron Microscopy (SEM) 34

3.8 Energy Dispersive X-ray Spectroscopy (EDX) 34

3.9 Particles Size Analysis 35

3.10 Surface area Pore Size Analysis 36

3.11 Photocatalytic activity 36

3.11.1 Photocatalytic activity test 38

3.11.2 Optimization of pH 38

3.11.3 Optimization of photocatalyst dose 38

3.11.4 Optimization of dye concentration 39

3.13 Reusability test 39

3.12 Evaluation of Quality Assurance Parameters 39

3.12.1 Chemical Oxygen Demand (COD) 39

3.12.2 Total organic carbons (TOC) 40

ix

3.12.5 Mineralization test 41

3.12.3 Total suspended solids (TSS) 42

3.12.4 Hemolytic Activity (Toxicity) 42

3.13 Data analysis 43

Chapter 4 Results And Discussions 44

4.1 X-Ray Diffraction Analysis 44

4.1.1 X-Ray Diffraction Analysis of (Al2O3)1-x(ZnO)x(Fe2O3) 44

4.1.1.1 X-Ray Diffraction Analysis of Al2O3.Fe2O3 synthesized by

mechanically stirred co-precipitation 44

4.1.1.2 XRD Analysis of Al2O3.Fe2O3 by synthesized by ultra-sonic

assisted mechanically stirred co-precipitation. 46

4.1.1.3 X-Ray Diffraction Analysis of (Al2O3)0.75(ZnO)0.25Fe2O3 -

synthesized by mechanically stirred co-precipitation 46


synthesized by ultra-sonic assisted mechanically stirred co-

precipitation

46





precipitation

49

.1.1.7 X-Ray Diffraction Analysis of (Al2O3)0.25(ZnO)0.75Fe2O3 -




precipitation

51

4.1.1.9 X-Ray Diffraction Analysis of ZnO.Fe2O3 synthesized by


4.1.1.10 X-Ray Diffraction Analysis of ZnO.Fe2O3 synthesized by

ultra-sonic assisted mechanically stirred co-precipitation 52

x

4.1.2 X-Ray Diffraction Analysis of (ZrO2)1-x(ZnO)x(Fe2O3) 53

4.1.2.1 X-Ray Diffraction Analysis of ZrO2.Fe2O3 synthesized by


4.1.2.2 X-Ray Diffraction Analysis of ZrO2 .Fe2O3 synthesized by

ultra-sonic assisted mechanically stirred co-precipitation 54

4.1.2.3 X-Ray Diffraction Analysis of (ZrO2)0.75(ZnO)0.25 Fe2O3 -


4.1.2.4 Diffraction Analysis of (ZrO2)0.75(ZnO)0.25 Fe2O3 -


precipitation

56





precipitation

57


synthesized by mechanically stirred co-precipitation

58

4.1.2.8

Diffraction Analysis of (ZrO2)0.25(ZnO)0.75 Fe2O3 -


precipitation

58

4.1.2.9

X-Ray Diffraction Analysis of ZnO.Fe2O3 synthesized by

mechanically stirred and ultra-sonic assisted mechanically

stirred co-precipitation

60

4.2 Scanning Electron Microscopy 60

4.2.1 Scanning Electron Microscopy of (Al2O3)1-x(ZnO)xFe2O3 60

4.2.2 Scanning Electron Microscopy for (ZrO2)1-x(ZnO)xFe2O3 62

4.3 Energy Dispersive X-Ray (EDX) Analysis 65

4.3.1 Energy Dispersive X-Ray (EDX) Analysis of

(Al2O3)1-x(ZnO)xFe2O3

65

4.3.1.1 Energy Dispersive X-Ray Analysis of Al2O3 .Fe2O3 65

4.3.1.2 Energy Dispersive X-Ray Analysis of 66

xi

(Al2O3)0.75(ZnO)0.25Fe2O3

4.3.1.3 Energy Dispersive X-Ray Analysis of

(Al2O3)0.50(ZnO)0.50Fe2O3 68

4.3.1.4 Energy Dispersive X-Ray Analysis of (Al2O3)0.25(ZnO)0.75

Fe2O3

69

4.3.1.5 Energy Dispersive X-Ray Analysis of ZnO.Fe2O3 71

4.3.2 Energy Dispersive X-Ray (EDX) Analysis of (ZrO2)1-

x(ZnO)xFe2O3

72

4.3.2.1 Energy Dispersive X-Ray Analysis of ZrO2.Fe2O3 72

4.3.2.2 Energy Dispersive X-Ray Analysis of (ZrO2)0.75(ZnO)0.25

Fe2O3

73

4.3.2.3 Energy Dispersive X-Ray Analysis of

(ZrO2)0.50(ZnO)0.50Fe2O3

75

4.3.2.4 Energy Dispersive X-Ray Analysis of (ZrO2)0.25(ZnO)0.75

Fe2O3

76

4.4 Particle Size, Surface area and porosity analysis 78

4.4.1 Particle Size analysis of (Al2O3)1─x(ZnO)xFe2O3 78

4.4.2 Particle Size analysis of (ZrO2)1-x(ZnO)xFe2O3 84

4.4.3 Surface area and porosity analysis of

(Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3

90

4.5 Photocatalytic Activity 91

4.5.1 Optimization of pH for the degradation of Methyl Orange 91

4.5.2 Optimization of catalyst dose for the degradation of Methyl

Orange

94

4.5.3 Optimization of dye concentration for the degradation of

Methyl Orange

96

4.5.4

Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 and

(ZrO2)1-x(ZnO)xFe2O3 synthesized by mechanically stirred

co-precipitation for the degradation of Methyl Orange

99

4.5.5

Optimization of x value (Al2O3)1-x(ZnO)xFe2O3 synthesized

by ultra-sonic assisted mechanically stirred co-precipitation

for the degradation of Methyl Orange

101

xii

4.5.6 Optimization of pH for the degradation of CI Reactive

Black 5

104

4.5.7 Optimization of photocatalyst dose for the degradation of CI

Reactive Black 5

107

4.5.8 Optimization of initial dye concentration for the degradation

of CI Reactive Black 5

110

4.5.9

Optimization of x values for (Al2O3)1-x(ZnO)xFe2O3 &

(ZrO2)1-x(ZnO)xFe2O3 synthesized by mechanically stirred

co-precipitation for the degradation of CI Reactive Black 5

112

4.5.10

Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 &

(ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic assisted

mechanically stirred co-precipitation for the degradation of

CI Reactive Black 5

115

4.5.11 Optimization of pH for the degradation of Methylene Blue 117

4.5.12 Optimization of catalyst dose for the degradation of

Methylene Blue

120

4.5.13 Optimization of initial dye concentration for the degradation

of Methylene Blue

122

4.5.14

Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 and

(ZrO2)1-x(ZnO)xFe2O3 and synthesized by mechanically

stirred co-precipitation for the degradation of Methylene

Blue

125

4.5.15

Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 and

(ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic assisted


Methylene Blue

127

4.6 Reusability Test for (Al2O3)0.75(ZnO)0.25Fe2O3 and

ZrO2.Fe2O3 synthesized by ultra-sonic assisted mechanically


130

4.7 Evaluation of Quality Assurance Parameters 132

4.7.1 Chemical Oxygen Demand (COD), Total Organic Carbon

(TOC) analysis.

132

4.7.2 Mineralization of dyes 135

xiii

4.7.3 Total Suspended Solids (TSS) 136

4.7.4 Haemolytic activity (Toxicity) 137

Chapter 5 Summary 139

Literature Cited 141

xiv

List of Tables

Table

No.

Title

Page

No.

3.1 Normal amounts of AlCl3, ZnCl2 and FeCl3 used for the synthesis of


31

3.2 Normal amounts of ZrCl4, ZnCl2 and FeCl3 used for the synthesis of

(ZrO2)1-x(ZnO)xFe2O3

32

4.1 Table No. 4.1 Estimated weight and molar percent of Al2O3.Fe2O3


precipitation and calcined at 600ᴼC from EDX spectra

66

4.2 Estimated weight and molar percent of (Al2O3)0.75(ZnO)0.25Fe2O3

from EDX spectra. Synthesized by ultra-sonic assisted mechanically

stirred co-precipitation and Calcined at 600ᴼC from EDX spectra.

68

4.3 Estimated weight and molar percent of (Al2O3)0.50(ZnO)0.50Fe2O3



69

4.4 Estimated weight and molar percent of (Al2O3)0.25(ZnO)0.75 Fe2O3



70

4.5 Estimated weight and molar percent of ZnO.Fe2O3 synthesized by

ultra-sonic assisted mechanically stirred co-precipitation and

calcined at 600ᴼC from EDX spectra

72

4.6 Estimated weight and molar percent of ZrO2.Fe2O3 synthesized by

ultra-sonic assisted mechanically stirred co-precipitation and

calcined at 600ᴼC from EDX spectra

73

4.7 Estimated weight and molar percent of (ZrO2)0.75(ZnO)0.25Fe2O3



75

xv




76




77

4.10 particle sizes of (Al2O3)1-x(ZnO)xFe2O3 synthesized with

mechanically stirred co-precipitation technique at different values of

x

78

4.11 particle sizes of (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-sonic

assisted mechanically stirred co-precipitation technique at different

values of x

79

4.12 particle sizes of (ZrO2)1-x(ZnO)xFe2O3 synthesized with mechanically

stirred co-precipitation technique at different values of x

85

4.13 Particle sizes of (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic

assisted mechanically stirred co-precipitation technique at different

values of x

85

4.12.1 Surface area and porosity analysis of (Al2O3)0.75(ZnO)0.25Fe2O3 90

4.13.1 Surface area and porosity analysis of ZrO2.Fe2O3 91

4.14 Optimization of pH for the degradation of Methyl Orange With

(Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-

precipitation with 50mg/100ml catalyst loading, 50ppm initial dye

concentration at room temperature

92

4.15 Optimization of pH for the degradation of Methyl Orange With

(ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-

precipitation at 50mg/100ml catalyst loading, 50ppm initial dye


93

4.16 Optimization of catalyst dose for the degradation of Methyl Orange

With (Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred

co-precipitation at pH = 3, and 50ppm initial dye concentration at

room temperature

94

xvi

4.17 Optimization of catalyst dose for the degradation of Methyl Orange

With (ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred

co-precipitation at pH = 3, and 50ppm initial dye concentration at

room temperature

95

4.18 Optimization of initial dye concentration for the degradation of

Methyl Orange With (Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by

mechanically stirred co-precipitation at pH = 3, and 60mg/100ml

catalyst dose at room temperature

97


Methyl Orange With (ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by

mechanically stirred co-precipitation at pH = 3, and 60mg/100ml


98

4.20 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by

mechanically stirred co-precipitation for the degradation of methyl

orange at pH=3, catalyst dose 60mg/100ml and initial dye

concentration 50ppm at room temperature

99

4.21 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by


orange at pH=3, catalyst dose 60mg/100ml and initial dye


100

4.22 value of x and their respective photocatalysts for (Al2O3)1-

x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3

101


ultra-sonic assisted mechanically stirred co-precipitation for the

degradation of methyl orange at pH=3, catalyst dose 60mg/100ml

and initial dye concentration 50ppm at room temperature.

102



degradation of methyl orange at pH=3, catalyst dose 60mg/100ml

and initial dye concentration 50ppm at room temperature.

103

xvii

4.25 Optimization of pH for the degradation of CI Reactive Black 5 With




105


ZrO2 Fe2O3) synthesized by mechanically stirred co-precipitation

with 60mg/100ml catalyst loading, 50ppm initial dye concentration

at room temperature

106


ZrO2 Fe2O3) synthesized by mechanically stirred co-precipitation

with 60mg/100ml catalyst loading, 50ppm initial dye concentration

at room temperature

108

4.28 Table No. 4.28 Optimization of catalysts dose for the degradation of

CI Reactive Black 5 With ZrO2.Fe2O3 synthesized by mechanically

stirred co-precipitation at pH = 3 and 50ppm initial dye concentration

at room temperature

109

4.29 Optimization of initial dye concentration for the degradation of CI

Reactive Black 5 With (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by

mechanically stirred co-precipitation at pH = 3 and 60mg/100ml


110


Reactive Black 5 With ZrO2.Fe2O3 synthesized by mechanically

stirred co-precipitation at pH = 3 and 60mg/100ml catalyst dose at

room temperature

111


mechanically stirred co-precipitation for the degradation of CI

Reactive Black 5 at pH=3, catalyst dose 60mg/100ml and initial dye


113


mechanically stirred co-precipitation for the degradation of CI

114

xviii

Reactive Black 5 at pH=3, catalyst dose 60mg/100ml and initial dye




degradation of CI Reactive Black 5 at pH=3, catalyst dose

60mg/100ml and initial dye concentration 50ppm at room

temperature

115



degradation of CI Reactive Black 5 at pH=3, catalyst dose

60mg/100ml and initial dye concentration 50ppm at room

temperature

116

4.35 Optimization of pH for the degradation of methylene blue with


precipitation at 60mg/100ml catalyst dose and 50ppm initial dye


118


ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at

60mg/100ml catalyst dose and 50ppm initial dye concentration at

room temperature

119

4.37 Optimization of catalyst dose for the degradation of methylene blue

with (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by mechanically stirred

co-precipitation at pH = 9 and 50ppm initial dye concentration at

room temperature

120

4.38 Optimization of catalyst dose for the degradation of methylene blue

with ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation

at pH = 9 and 50ppm initial dye concentration at room temperature

121


methylene blue with (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by

mechanically stirred co-precipitation at pH = 9 and 60mg/100ml


123

xix


methylene blue with ZrO2.Fe2O3 synthesized by mechanically stirred

co-precipitation at pH = 9 and 60mg/100ml catalyst dose at room

temperature

124

4.41 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 synthesized by


methylene blue at pH = 9, 60mg/100ml catalyst dose and 50ppm

initial dye concentration at room temperature

125

4.42 Optimization of x value of (ZrO2)1-x(ZnO)xFe2O3 synthesized by


methylene blue at pH = 9, 60mg/100ml catalyst dose and 50ppm


126



degradation of methylene blue at pH = 9, 60mg/100ml catalyst dose

and 50ppm initial dye concentration at room temperature

128



degradation of methylene blue at pH = 9, 60mg/100ml catalyst dose

and 50ppm initial dye concentration at room temperature

129

4.45 Reusability of (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3 in six cycles

for MO, RB5 and MB at optimum operational conditions

130

4.46 Degradation, decrease in COD and decrease in TOC with

(Al2O3)0.75(ZnO)0.25Fe2O3 & ZrO2.Fe2O3

132

xx

List of Figures

Fig.

No.

Title

Page

No. 4.1 XRD patterns of Al2O3.Fe2O3 synthesized by mechanically stirred co-

precipitation

45

4.2 XRD patterns of Al2O3.Fe2O3 synthesized by ultra-sonic assisted

mechanically stirred co-precipitation

45

4.3 XRD patterns of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by mechanically


47

4.4 XRD patterns of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic

assisted mechanically stirred co-precipitation

47



48



49



50



51

4.9 XRD patterns of ZnO.Fe2O3 synthesized by mechanically stirred co-

precipitation

52

4.10 XRD patterns of ZnO.Fe2O3 synthesized by ultra-sonic assisted


53

4.11 XRD patterns of ZrO2.Fe2O3 synthesized by mechanically stirred co-

precipitation

54

4.12 XRD patterns of ZrO2.Fe2O3 synthesized by ultra-sonic assisted


55

4.13 XRD patterns of (ZrO2)0.75(ZnO)0.25 Fe2O3 synthesized by mechanically


55

4.14 XRD patterns of (ZrO2)0.75(ZnO)0.25 Fe2O3 synthesized by ultra-sonic


56

xxi

4.15 XRD patterns of (ZrO2)0.50(ZnO)0.50 Fe2O3 synthesized by mechanically


57

4.16 XRD patterns of (ZrO2)0.50(ZnO)0.50 Fe2O3 synthesized by ultra-sonic


58

4.17 XRD patterns of (ZrO2)0.25(ZnO)0.75Fe2O3 synthesized by mechanically


59

4.18 XRD patterns of (ZrO2)0.25(ZnO)0.75Fe2O3 synthesized by ultra-sonic


59

4.19 SEM image of Al2O3.Fe2O3 synthesized by ultra-sonic assisted

mechanically stirred co-precipitation and calcined at 600ᴼC

60

4.20 SEM Image of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic

assisted mechanically stirred co-precipitation and calcined at 600ᴼC

61



61



62

4.23 SEM Image of ZnO.Fe2O3 synthesized by ultra-sonic assisted


62

4.24 SEM Image of ZrO2.Fe2O3 synthesized by ultra-sonic assisted


63

4.25 SEM Image of (ZrO2)0.75(ZnO)0.75Fe2O3 synthesized by ultra-sonic


63



64



64

4.28 SEM (back scatter) image for EDX spectra of Al2O3.Fe2O3 synthesized

by ultra-sonic assisted mechanically stirred co-precipitation and calcined

at 600ᴼC

65

4.29 EDX spectra of Al2O3.Fe2O3 synthesized by ultra-sonic assisted 66

xxii


4.30 SEM (back scatter) image for EDX spectra of (Al2O3)0.75(ZnO)0.25Fe2O3

synthesized by ultra-sonic assisted mechanically stirred co-precipitation

and calcined at 600ᴼC

67

4.31 EDX spectra of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic


67

4.32 SEM (back scatter) image for EDX spectra of (Al2O3)0.50(ZnO)0.50Fe2O3

synthesized by ultra-sonic assisted mechanically stirred and calcined at

600ᴼC

68

4.33 EDX spectra of (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized by ultra-sonic


69

4.34 SEM (back scatter) image for EDX spectra of (Al2O3)0.25(ZnO)0.75 Fe2O3



70

4.35 EDX spectra of (Al2O3)0.25(ZnO)0.75 Fe2O3 synthesized by ultra-sonic


70

4.36 SEM (back scatter) image for EDX spectra of ZnO.Fe2O3 synthesized by

ultra-sonic assisted mechanically stirred co-precipitation and calcined at

600ᴼC

71

4.37 EDX spectra of ZnO.Fe2O3 synthesized by ultra-sonic assisted


71

4.38 SEM (back scatter) image for EDX spectra of ZrO2.Fe2O3 synthesized

by ultra-sonic assisted mechanically stirred co-precipitation and calcined

at 600ᴼC

72

4.39 EDX spectra of ZrO2.Fe2O3 synthesized by ultra-sonic assisted


73

4.40 SEM (back scatter) image for EDX spectra of (ZrO2)0.75(ZnO)0.25Fe2O3



74

xxiii

4.41 EDX spectra of (ZrO2)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic


74



and calcined at 600ᴼC.

75



76




77



77

4.46 Particle size distribution by intensity for Al2O3.Fe2O3 synthesized by


79

4.47 Particle size distribution by intensity for (Al2O3)0.75(ZnO)0.25Fe2O3


80



80



81

4.50 Particle size distribution by intensity for ZnO.Fe2O3 synthesized by


81

4.51 Particle size distribution by intensity for Al2O3.Fe2O3 synthesized by

ultra-sonic assisted mechanically stirred co-precipitation

82



82



83



83

xxiv

4.55 Particle size distribution by intensity for ZnO.Fe2O3 synthesized by


84

4.56 Particle size distribution by intensity for ZrO2.Fe2O3 synthesized by


86

4.57 Particle size distribution by intensity for (ZrO2)0.75(ZnO)0.25Fe2O3


86



87



87

4.60 Particle size distribution by intensity for ZrO2.Fe2O3 synthesized by


88



88



89



89

4.64 Optimization of pH for the degradation of methyl orange with




92

4.65 Optimization of pH for the degradation of methyl orange with



concentration at room temperature.

93

4.66 Optimization of catalyst dose for the degradation of methyl orange with


precipitation at pH = 3, and 50ppm initial dye concentration at room

temperature

95

xxv

4.67 Optimization of catalyst dose for the degradation of methyl orange with


precipitation at pH = 3, and 50ppm initial dye concentration at room

temperature

96

4.68 Optimization of initial dye concentration for the degradation of methyl

orange with (Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically

stirred co-precipitation at pH = 3, and 60mg/100ml catalyst dose at room

temperature.

97

4.69 Optimization of initial dye concentration for the degradation of methyl

orange with (ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically

stirred co-precipitation at pH = 3, and 60mg/100ml catalyst dose at room

temperature.

98



orange at pH=3, catalyst dose 60mg/100ml and initial dye concentration

50ppm at room temperature

100



orange at pH=3, catalyst dose 60mg/100ml and initial dye concentration

50ppm at room temperature

101

4.72 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-

sonic assisted mechanically stirred co-precipitation for the degradation

of methyl orange at pH=3, catalyst dose 60mg/100ml and initial dye


103

4.73 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-


of methyl orange at pH=3, catalyst dose 60mg/100ml and initial dye


104




106

xxvi






107

4.76 Optimization of catalysts dose for the degradation of CI Reactive Black

5 With (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred

co-precipitation at pH = 3 and 50ppm initial dye concentration at room

temperature

108

4.77 Optimization of catalysts dose for the degradation of CI Reactive Black

5 With ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation

at pH = 3 and 50ppm initial dye concentration at room temperature

109


Reactive Black 5 With (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by

mechanically stirred co-precipitation at pH = 3 and 60mg/100ml catalyst

dose at room temperature

111


Reactive Black 5 With ZrO2.Fe2O3 synthesized by mechanically stirred

co-precipitation at pH = 3 and 60mg/100ml catalyst dose at room

temperature

112


mechanically stirred co-precipitation for the degradation of CI Reactive

Black 5 at pH=3, catalyst dose 60mg/100ml and initial dye


113


mechanically stirred co-precipitation for the degradation of CI Reactive

Black 5 at pH=3, catalyst dose 60mg/100ml and initial dye


114

4.82 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-


of CI Reactive Black 5 at pH=3, catalyst dose 60mg/100ml and initial

116

xxvii

dye concentration 50ppm at room temperature

4.83 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-


of CI Reactive Black 5 at pH=3, catalyst dose 60mg/100ml and initial

dye concentration 50ppm at room temperature

117



precipitation at 60mg/100ml catalyst dose and 50ppm initial dye


118


ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at

60mg/100ml catalyst dose and 50ppm initial dye concentration at room

temperature

119

4.86 Optimization of catalyst dose for the degradation of methylene blue with

(Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by mechanically stirred co-

precipitation at pH = 9 and 50ppm initial dye concentration at room

temperature

121

4.87 Optimization of catalyst dose for the degradation of methylene blue with

ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at pH =

9 and 50ppm initial dye concentration at room temperature

122


methylene blue with (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by

mechanically stirred co-precipitation at pH = 3 and 60mg/100ml catalyst

dose at room temperature

123


methylene blue with ZrO2.Fe2O3 synthesized by mechanically stirred co-

precipitation at pH = 9 and 60mg/100ml catalyst dose at room

temperature

124


mechanically stirred co-precipitation for the degradation of methylene

blue at pH = 9, 60mg/100ml catalyst dose and 50ppm initial dye

126

xxviii



mechanically stirred co-precipitation for the degradation of methylene

blue at pH = 9, 60mg/100ml catalyst dose and 50ppm initial dye


127

4.92 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-


of methylene blue at pH = 9, 60mg/100ml catalyst dose and 50ppm


128

4.93 Optimization of x value of (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-


of methylene blue at pH = 9, 60mg/100ml catalyst dose and 50ppm


129

4.94 Reusability of (Al2O3)0.75(ZnO)0.25Fe2O3 in six cycles for the degradation

of MO, RB5 and MB at optimum operational conditions

131

4.95 Reusability of ZrO2.Fe2O3 in six cycles for the degradation of MO, RB5

and MB at optimum operational conditions

131

4.96 Decrease in COD of MO, RB5 and MB with (Al2O3)0.75(ZnO)0.25Fe2O3 133

4.97 Decrease in COD of MO, RB5 and MB with ZrO2.Fe2O3 133

4.98 Decrease in TOC of MO, RB5 and MB with (Al2O3)0.75(ZnO)0.25Fe2O3 134

4.99 Decrease in TOC of MO, RB5 and MB with ZrO2.Fe2O3 134

4.100 Mineralization of MO,RB5 and MB with (Al2O3)0.75(ZnO)0.25Fe2O3 in 8

hours

135

4.101 Mineralization of MO, RB5 and MB with ZrO2.Fe2O3 25Fe2O3 in 8 hours 136

4.102 Toxicity assay of samples treated with (Al2O3)0.75(ZnO)0.25Fe2O3 and

un-treated samples

137

4.103 Toxicity assay of samples treated with (Al2O3)0.75(ZnO)0.25Fe2O3 and

un-treated samples

138

xxix

ABSTRACT

Water pollution is a major problem around the world especially the countries having

large textile industries as these industries use huge amount of water in textile processing.

Dyes make our world beautiful but dyes industries have major part of water pollution. 10 -15

percent of dye goes to the water stream during the dying process in a textile dyeing

industries. Many of these dyes are carcinogenic and have very harmful effects on human

being as well as aquatic life. Many physical and chemical techniques are used for the

treatment of waste water. One of currently investigating technique is photocatalytic

degradation of organic pollutants from waste water.

In this study two types of novel metal oxides nanophotocatalysts were synthesized

with general formulas (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3 where x = 0, 0.25,

0.50, 0.75 and 1. Co-precipitation via simple mechanical stirring and a newly developed

method co-precipitation via ultra-sonic assisted mechanical stirring were used for the

synthesis of both nanophotocatalysts.

Characterization of synthesized photocatalyst was done with X-Ray Diffraction,

Scanning Electron Microscopy, Energy Dispersive X-Ray, Particle size analysis and Surface

analysis like Single Point surface area, BET surface area and pore volume BJH adsorption

and desorption pore volume,

Photocatalytic activity test was performed with three different dyes Methyl Orange

(MO), CI Reactive Black 5 (RB5) and Methylene Blue (MB) by optimizing the pH,

photocatalyst dose and initial dye concentration for both photocatalysts at room temprature.

(Al2O3)1-x(ZnO)xFe2O3 with x=0.25 has maximum degradation efficiency as it degraded MO

93.52%, RB5 91.08% and MB 83.74% with photocatalyst synthesized by ultra-sonic assisted

mechanically stirred co-precipitation while the photocatalyst (ZrO2)1-x(ZnO)xFe2O3

synthesized by ultra-sonic assisted mechanically stirred co-precipitation with x= 0 degraded

the MO 78.38%, RB5 83.21% and MB 73.97% in 140 min.

1

CHAPTER 1

INTRODUCTION

Life on earth depends on water. We cannot think about any sort of life without water.

Relationship between the atmosphere, lithosphere and hydrosphere is through water cycle

and major driving force on our planet is this water cycle. Water on earth and oceans is

constantly evaporating into atmosphere. Rain and snow fall is the result of that evaporated

water when atmosphere is saturated. Some part of water is present in solid form as glaciers or

polar ice. Rain water or melted snow percolates through earth as ground water or go back to

the sea. Human beings are neglecting the importance of water as it is unnecessarily flowed to

sink and polluted with different pollutants and they never thought about the danger which

they are purchasing.

The metropolitan growth and fast industrialization has resulted in continuous

deterioration of the Global environment since many years. These environmental changes are

not in favor of living organisms present on earth. These activities are creating problems like

Global warming and environmental pollution (Hill, 2010). Besides other environmental

issues, water pollution is of major concern. Water is extensively used in many industries

because it is universal solvent. The extensive use of water in many industries and the

pollution of natural water resources have worsened the problem of water scarcity. The

disease free clear drinking water is an important pre-requisite for existence of life on earth

but the quality of drinking water is declining day by day. The pollution of water reservoirs is

also dangerous for aquatic life. Fish are vulnerable to polluted water. To prevent the water

from contamination has become an issue of prime importance for the modern World.

Textile industry is one of the most important and rapidly developing industrial

sectors. It has high importance in terms of its environmental impact, since it consumes

considerably high amounts of water for processing (Tüfekci et al., 2007). Hence the textile

effluents are playing a key role in enhancing the water pollution problem. Theses effluents

usually contain acids, alkalies, salts, surfactants, oxidizing or reducing agents, enzymes, fatty

2

mater and scouring agents along with synthetic dyes. These synthetic colors are major source

or water pollution due to their visibility and recalcitrant nature (Crini, 2006).

Currently more than 8000 types of dyes are being manufactured having different

chemical natures. Major portion of these dyes is consumed by textile processing industries

(Anjaneyulu et al., 2005). These synthetic dyes possess complex aromatic structures so are

mostly non-degradable (Daneshvar et al., 2008). Once these dyes get enter into water

streams, these consume the dissolved oxygen which results in the destruction of aquatic life.

These colored effluents changes the water quality parameters like pH, dissolved oxygen

(DO), biological oxygen demand (BOD) and chemical oxygen demand (COD) etc. (Özer et

al., 2006; Mahmoud et al., 2007). Water becomes unsuitable for aquatic life and human

consumption. Hence, this polluted water requires treatment before its discharge into

environment (Papić et al., 2004).

Different methods for water treatment like chemical, physical, physico-chemical,

mechanical and biological are commercially employed to textile colored waste water

(Ferrero, 2000). Classical techniques which are still in use to decontaminate polluted water

include adsorption (Rauf et al., 2009; Nasuha et al., 2010), chlorination (Ge et al., 2008;

Sharma et al., 2009), coagulation (Ahmad and Puasa, 2007; Riera-Torres et al., 2010), ion

flotation (Shakir et al., 2010)b, membrane process (Lee et al., 2008; Jirankova et al., 2010),

sedimentation (Zodi et al., 2010) and solvent extraction (Egorov et al., 2008; Juang et al.,

2009). All these methods have advantages and drawbacks as well. The end products of these

techniques need to be processed further for complete purification. There are newer advanced

oxidation processes which can be used to degrade harmful products into carbon dioxide and

water (Ullah et al., 2012).

Advanced oxidation processes (AOPs) are alternative methods for decolorizing

and reducing recalcitrant wastewater loads that are generated by textile effluents.

Considerable progress has been made in the development of AOPs for textile effluent in

recent years, especially in ozone-related processes. Conventional oxidation treatment

has found difficulty to oxidize dyestuffs and complex structured organic compounds at

low concentrations or if they are especially resistant to the oxidants. To ease the stated

problems advanced oxidation processes have been developed to generate hydroxyl free

3

radicals by different techniques (Hill, 2010). These processes are combination of ozone

(O3) and hydrogen peroxide (H2O2) and UV irradiation which showed the greatest

promise to treat textile waste water. These oxidants effectively decolorize dyes,

however do not remove COD completely (Al-Kdasi et al., 2004). AOPs also include

biodegradation, fenton, photofenton, photocatalytic, sonolysis, ozonation and UV

photocatalytic processes. These advanced oxidation processes are better than chemical

ones however these are much costly (Ullah et al., 2012).

The development of civilization has been intimately linked with the ability of

human being to work with materials beginning with stone age and ranging through the

era of copper and bronze then iron age and now is the age of advanced materi als i.e.

nano sized particles. Advanced materials or nanoparticles possess a new set of

magnetic, optical, transport, mechanical, electrochemical and photochemical properties

(Nalwa, 1999). First photo electrochemical cell was designed by Fujishima and Honda

for splitting water using Pt coated TiO2 (Fujishima and Honda, 1972). Since then

nanophotocatalysts have been used to decompose organics, in solar cells for the

production of electricity and H2, in electronic devices and in optical coatings

(Hashimoto et al., 2005).

A number of semiconductors having photocatalytic properties have been

investigated for the remediation of water and air pollution. Examples of some

semiconductors along with their band gap energies are Fe2O3 (2.2 eV) (Duret and

Grätzel, 2005), NFeTiO2 (2.8 eV) (Kuvarega et al., 2014), CdS (2.5 eV) (Mews et al.,

1996), SnO2 (3.5 eV) (Leite et al., 1999), SrTiO3 (3.4 eV) (Lee et al., 2013), TiO2 (3.2

eV) (Wold, 1993), WO3 (2.8 eV) (Morales et al., 2008), , ZnFe2O4 (1.9 eV) etc.

(Kondawar et al., 2011)

Then there are attempts to synthesize binary and ternary visible light driven

nanophotocatalysts with enhanced activity e.g. ZrO2/TiO2 (Wang et al., 2006; Hidalgo

et al., 2007; Neppolian et al., 2007; Wu et al., 2009; McManamon et al., 2011; Song et

al., 2011; Sun et al., 2011; Swetha and Balakrishna, 2011; Shao et al., 2014; Pirzada et

al., 2015), Mn/ZrO2 (Alvarez et al., 2007), ZrO2 (Stojadinović et al., 2015), ZnO.ZrO2

(Sultana et al., 2015), Nb2Zr6 O17-x Nx (Kanade et al., 2007), ZrO2 TaON ((Maeda et

al., 2009), Zr TiO4/Bi2O3 (Neppolian et al., 2010), CdS/Zr-McM-41 (Liu et al., 2012)a,

4

ZrO2/SnO2 (Pouretedal et al., 2012), ZrBi2WO6 (Zhang et al., 2011)c, Fe2O3-

ZrO2/Al2O3 (Liu et al., 2012)b and N-Zr-TiO2 (Liu et al., 2015).

Visible light can be defined as portion of electromagnetic spectrum having

wavelength between 380-780 nm. Sunlight contain only about 4% UV-light (λ=300-380

nm). Visible light activation of photocatalyst is being pursued all over the world. Even

though such photocatalysts could not be gained in full success. It has been highly

demanded for immediate and future applications.

Photocatalyst induced by visible light should have a band gap between 2-3 eV

and ionic character of bond below 30 % (Shakir et al., 2010)a. So that photons of visible

light can excite electrons from valence band to conduction band producing electron and

hole (e-/h+) pair (Liu et al., 2012)a. Success of photoreaction depends upon transfer

efficiency of e- or h+ to oxidizing and reducing radicals. But recombination rate of e-

and h+ is very fast (nanoseconds) than the transfer rate (micro seconds to milli seconds).

A large number of charge carriers recombine resulting in heat energy e - + h+ → heat

(Hoffmann et al., 1995). Conduction band e- act as a reducing agent and valence band

h+ act as oxidizing agent at the surface of a semiconductor (Chen et al., 2010).

Photocatalytic activity can be enhanced by controlling recombination rate of photo

generated e- and h+. Suitable scavenger can trap e- or h+ leading to redox reaction and

retarding recombination rate of charge carriers (Wang et al., 2009)b.

Semiconductor should have the following properties so that it can work as a

good photocatalyst.

i. Its chemical nature should be such that it can change its oxidation states to

accommodate positive hole (h+) instead of decomposition (Hoffmann et al.,

1995).

ii. It should have more than one stable oxidation states (Wold, 1993).

iii. It should have suitable band gap energy (Khan and Rao, 1991). Band gap

energy should be up to 3.0 eV (Shakir et al., 2010)a.

iv. It should be inert against chemical and photo corrosion (Nair et al., 1993).

v. It should be non-toxic (Mills et al., 1993).

vi. It should have low cost (Dong et al., 2012).

5

The position of zirconium in periodic table is in IVth B group under titanium.

Structural parameters of Zr indicate that ZrO2 should be a very good semiconductor for

photocatalysis in heterogeneous photocatalysis with band gap energy 5.0 eV and

conductance & valence potential +4 to -1 verses normal hydrogen electrode (NHE)

(Wang et al., 2004; Pouretedal et al., 2012). ZrO2 has thermal stability, resistant to

chemical & photo corrosion and strong mechanical stability (Plaza et al., 1997; Zhang

and Gao, 2001; Yu et al., 2003). ZrO2 can be applied in a number of technological

fields for example high performance ceramics (Garvie et al., 1975), oxygen sensors

(León et al., 1997), high temperature fuel cells (Badwal, 1990; Li et al., 2004; Wang et

al., 2004), catalysts (Haw et al., 2000; Wu et al., 2009), optical coatings (Mansour et

al., 1990), orthopedic and dental implants (Li and Hastings, 1998), white pigment and

opacifier (Siddiquey et al., 2011), photocatalyst composite materials (Zhang and Gao,

2001), chromatographic support materials (Acosta et al., 1995), highly efficient

photocatalysis (Ashkarran et al., 2010; Du et al., 2014) and Ionic conductor (Wei and

Li, 2008; Matsui et al., 2009).

ZrO2 is dominating in photocatalysis field because of its high band gap, nontoxic

nature, high surface area, high photocatalytic activity, wide range of processing

procedure, low cost, reusability and very good chemical and photo chemical stability.

ZrO2 prepared by arc-discharge method showed two times more photocatalytic activity

as compare with Degussa P-25 TiO2 standard photocatalyst under similar experimental

conditions for Rhodamine B degradation (Ashkarran et al., 2010).

A number of research workers and engineers are being involved in the basic

studies, manufacturing, improvements, measurements and application of ferrites.

Ferrites may be defined as magnetic materials composed of oxides containing ferric ion

as the main constituent. Hilpert in 1909 published the first systematic study of the

relationship between the chemical and magnetic preparations: Ferrites are used in the

area of information storage, audio tapes, disk storage media and credit cards. They are

very important due to their optical, electronic, magnetic properties and for their

stability against physical and chemical changes. At the same time these are very good

photocatalysts. e. g. ZnFe2O4 is a n-type semiconductor with band gap of 1.9 eV, can be

activated by the visible light irradiation λ=652 nm or shorter wave lengths, A new

6

magnetic and visible light responsive photocatalyst TiO2-ZnFe2O4 was prepared by

alloying TiO2 and ZnFe2O4 semiconductors. (Srinivasan et al., 2006)a. Magnetic

nanoparticles have got much importance in nano-structured materials (Curtis and

Wilkinson, 2001). These materials have unique paramagnetic property which mean that

they are attracted by a magnet and retain no residual magnetic character when magnetic

field is removed (Yang et al., 2004). Magnetic nanoparticles are applied in various

fields e.g. magnetically assisted drug delivery (Patil, 2003), magnetic separation of

biomolecules (Lee et al., 2006), magnetic resonance imaging (Yallapu et al., 2011),

gene manipulation (Green et al., 2008) and photocatalysis (Rana et al., 2005; Green et

al., 2008; Harraz et al., 2014).

Light induced chemical reaction occurring at the sur face of nano sized catalyst is

termed as photocatalysis. It can be further subdivided in catalyzed and sensitized

whether the excitation take place at catalyst surface or absorbate molecule (Linsebigler

et al., 1995). The absorbed energy is consumed to excite electrons of valence band to

conduction band. Difference of the energy between conduction band and valence band

is known as band gap energy of the semiconductor. If photon has energy equal to or

greater then band gap energy electron of valence band is transferred to conduction band

leaving positive hole in valence band. The pair of this negative (e -) and positive charge

(h+) is known as electron-hole pair (EHP). Band gap energy (Eg) of semiconductor and

wavelength of light (λ) which can produce EHP can be related by the equation

Eg = 1240/ λ (nm) (Shakir et al., 2010)a

This absorption of energy also depends upon the size and surface area of

photocatalyst. The recombination of EHP produces heat energy which is biggest

hindrance in the successful photocatalytic reaction. The life time of EHP is about 30

nano seconds (Colombo and Bowman, 1996).

The photo excited electrons transferred to surface of photocatalyst and parti cipate in

reduction of O2 to O2∙ or singlet oxygen to O∙ in aqueous solution.

O2 + e- O2∙

7

O + e─ O ∙

O∙ + H2O H2O2∙

O∙ + O2 O3

∙ (Goswami, 1995; Cavicchioli and

Gutz, 2002)

These reactions prevent EHP recombination and causes the photocatalysis to start

(Diebold, 2003). Photo generated positive hole (h+) also transferred to the surface of

photocatalyst and oxidizes easily oxidizable organics or react with OH- and produce

OH∙ which is short lived and highly reactive radical

h+ + OH─ OH∙

This OH. radical combine with organic pollutant and degrade into CO2 and H2O

(Shapovalov et al., 2002). The pollutants which can be decomposed photocatalytically

are alcohols, phenols, halo phenols, alkanes, halo alkanes, aromatics, pesticides,

herbicides, surfactants, polymers, dyes, bacteria, molds, fungi, viruses and cancer cells

(Mills and Le Hunte, 1997).

Three parameters which affect the photocatalytic reaction of a photocatalyst are as

under (Martin et al., 1995)

I. Ability to absorb photon of light

II. Rate of oxidation reduction reaction occurring at its surface.

III. Rate of e-/h+ EHP recombination

These three parameters can be controlled by the properties of photocatalyst which are

crystal structure, crystalline phase, porosity, surface area, surface acidity, surface OH -

groups, band gap energy, e─ and h+ separation/recombination and particle size. All of

these properties can be changed by using a number of chemical and physical methods

(Blake, 1994; Boldyrev and Tkáčová, 2000) .

Scientists round the world are working to improve the nanophotocatalysts for the

response of UV activation to visible light activation (Mohamed et al., 2012). This goal

can be achieved by different methods i.e. by doping of photocatalysts with other

8

elements, by sensitizing photocatalysts with colored compounds, by coupling of

different semiconductors. There is an urgent need in the field of photocatalysis to

develop new photocatalysts which can be activated by sun light with enhanced

functions.

This project was designed to treat the colored textile effluents efficiently with low -cost

photocatalysis. To achieve this aim we have developed two novel photocatalyst which

are visible light driven with enhanced photocatalytic activity

I. (Al2O3)1-x(ZnO)xFe2O3.

II. (ZrO2)1-x(ZnO)xFe2O3.

9

CHAPTER 2

REVIEW OF LITERATURE

Visible light driven photocatalysts (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-

x(ZnO)xFe2O3 were synthesized for the treatment of colored effluents. The

photocatalytic activity of these photocatalysts was evaluated by degrading three

different dyes in aqueous solution. These were also characterized for their physical

parameters. Exact literature about these photocatalysts is not available for review.

However some review of literature about different types of nanophotocatalysts is given

below for comparison.

Nanocomposite material WOx-TiO2 was synthesized by sol-gel technique and

characterized by XPS, XRD, SPS, PL, EFISPS and UV-Vis spectroscopy. Particle size

of this catalyst was 23.4 nm and surface area was 85.1 m²g-1. Photocatalytic activity was

determined by degrading methylene blue (MB) dye under visible light irradiation. 83.5

% TOC was removed in 100 min this catalyst was best for M.B. degradation..(Li et al.,

2001).

ZrO2.TiO2 binary oxides nanocomposites were synthesized by sol-gel technique

and calcined at 600ᴼC and 800ᴼC. Nanocomposites were subjected to XPS, XRD, TEM,

SEM, BET, UV-Vis spectroscopy for characterization. Photocatalytic activity was

assessed by salicylic and Cr(VI) degradation. Band gap energy of the sample calcined at

600°C was 3.54 eV and that at 800 °C was 3.36 eV.(Colón et al., 2002)

Degussa P-25 TiO2 was sensitized with average diameter of 30 nm. Acid Red 44

was used as a sensitizer visible light sensitized dye which was pH dependent. The

sensitized dye then activates TiO2. Which then degrade organic pollutant i.e. phenol. At

the same time sensitized dye was also decomposed. In this TiO 2 can degrade phenol and

Acid Red 44 under visible light [λ =420 nm] irradiation (Moon et al., 2003).

Nano crystals of Zr4+ doped TiO2 was synthesized by sol-gel technique. And

characterized by TEM, IR, XRD and BET analysis. The photo catalytic activity was

tested by degrading methyl orange in aqueous solutions Zr 0.06Ti0.94O2 showed best

10

decolorizing efficiency i.e. 87.7 % which is 1.5 time greater as compared with TiO2 and

P25 TiO2. Introduction of Zr24+ in TiO2 resulted in smaller particle size, larger surface

area and lattice deformation (Wang et al., 2004).

A visible light driven nanophotocatalyst TiO2-ZnFe2O4 was synthesized by a co-

precipitation/hydrolysis method and characterization was done by SEM, XRD and UV-

Vis. Spectroscopy. Photocatalytic activity was determined by phenol degradation under

visible (λ> 400 nm), UV and solar light. TiO2-ZnFe2O4 degraded 52 % phenol under

indoor solar light irradiation (Srinivasan et al., 2006)a.

Nanocomposites of CdS/TiO2 were synthesized by a reverse micelle route and

calcined at 500 oC. Photo catalyst was characterized by XRD and SEM-EDS analysis.

Photocatalytic activity was assessed by phenol degradation in aqueous solution. CdS

50% TiO2 degraded 40 % phenol in 3.5 h under visible light (λ> 400 nm) through a cut

off glass filter. The particle size of CdS-TiO2 nanocomposite was [CdS ~ 18.1 nm and

TiO2 ~ 59.9 nm] and surface area was 24 m²g-1 (Srinivasan et al., 2006)b.

ZnS/TiO2 nanocomposite was prepared by solvothermal technique. Visible light

induced photocatalyst was characterized by TEM, XRD, UV/DRS and PL spectroscopy.

Particle size varies between 10-15 nm. Photocatalytic activity was determined by

degrading the parathion-methyl under visible light irradiation. Photo catalyst degraded

100 % parathion methyl in 30 min. The enhanced activity was due to association of

nanophotocatalyst and pollutant molecules (Xiaodan et al., 2006).

ZrO2 was doped with Mn, Fe, Co and Cu using sol-gel technique. Synthesized

photocatalysts were subjected to BET surface area, XPS, XRD, and UV/Vis

Spectroscopy. 2,4 Dichlorophenoxy acetic acid (2,4 D) was degraded as a test pollutant

under UV light (254nm) irradiation. 70 % 2,4, D was decomposed by Mn-ZrO2

calcined at 400○C. Tetragonal phase of ZrO2 was dominant in all the samples. Band gap

energy ranged between 3.6 – 5.5 eV. BET surface area was found to be 55 and 80 m2/g

doped metals could not be detected by XRD being in small concentrations (Alvarez et

al., 2007).

Nanophotocatalyst Fe/ZrO2-TiO2 was synthesized by sol-gel impregnation

technique. It was characterized by EXAFS spectroscopy. Only tetragonal zirconium

dioxide was present with TiO2. Fe-O-Fe and Fe-O-Zr bonds were formed in

11

nanocomposite. Photocatalytic oxidation of salicylic acid was reduced from 15.8 to <1

% due to iron dropping and photocatalytic reduction of Cr IV was reduced from 7 % to

<1 %. Doping of Fe on ZrO2-TiO2 system depressed the photocatalytic activity of ZrO2-

TiO2 (Hidalgo et al., 2007).

Synthesis of binary oxides photocatalyst ZrO2-TiO2 was done by sol-gel

technique with different weight ratios of ZrO2 and TiO2. The photocatalyst was

characterized by FTIR, DRS, XRD, Nitrogen Adsorption, Raman Spectroscopy, Photo

luminescence and TEM analysis. Photocatalytic activity was determined by degrading

4-chloro phenol as a test pollutant. Binary oxides catalyst showed better activity as

compared with ZrO2 or TiO2 or Degussa P25 TiO2. Molar ratio 1:1 ZrO2-TiO2 catalyst

calcined at 500 ○C showed 94 % degradation of 4-chloro phenol under UV light

irradiation in 60 min. Reaction mechanism considering band gap energies was proposed

(Neppolian et al., 2007).

Ag-TiO2 photocatalyst was prepared by sol-gel and photo deposition technique

and characterized by TEM, XRD and UV-Vis spectrometry. Photo catalytic activity was

determined by degrading Reactive Yellow 17 (RY 17) using UV and Visible light.

About 95 % RY-17 was degraded in 120 min under visible light irradiation. 100 % TOC

was removed after 5 hour under visible light irradiation. RY -17 degradation obeyed 1st

order kinetics (Rupa et al., 2007).

TiO2-ZnO binary oxide nano powder synthesized by ultrasonic precipitation

technique was subjected to XRD analysis. Photocatalytic activity was determined by

degrading C.I. Basic Blue-41 in aqueous solution. Optimum pH was 6.2 and dye

concentration was 20 mg/L. 1:1 [TiO2:ZnO] degraded 100 % dye in 1 hour. Dye

degradation reaction showed pseudo Ist order kinetics (Jiang et al., 2008).

K0.3 Ti4 O7.3 OH1.7 was prepared by calcination method and TiO2 anatase

nanoparticles were prepared by hydrothermal technique. Both these materials were

combined by refluxing in HNO3 to prepare K0.3 Ti4 O7.3 OH1.7-TiO2 nanocomposite.

Photocatalyst was characterized by XRD, SEM TEM techniques. Photo catalytic

activity was determined by degrading methylene blue under black light irradiation.

photocatalyst K0.3 Ti4 O7.3 OH1.7 – TiO2 calcined at 600 oC for two hours gave the

highest photocatalytic activity (Tawkaew et al., 2008).

12

Highly activated Fe2O3/SnO2 nanophotocatalyst was synthesized and calcined at

300 oC, 400 oC and 500 oC for 3 hour. Photocatalyst was characterized by TEM, XRD,

BET, and UV-Vis spectroscopy. Sample calcined at 400 oC resulted in smallest particle

sized of 15 nm, largest surface area 28.75 m²g-1 and highest photo catalytic activity i.e.

98 % degradation of acid Blue 60 in 60 min under visible light (λ> 400 nm) irradiation.

This activity was 3.6 times greater as compare with P-25 TiO2 (Xia et al., 2008).

Phosphate Zr doped TiO2 was prepared via non-hydrolytic sol-gel technique.

Samples calcined at 550 °C to 950 °C gave 2.88-5.28 times higher degradation of Bis-

phenol than P-25. TiO2 under UV light (λ= 305 nm) irradiation. Samples were analyzed

by thermal treatment, FTIR, XPS, TEM, XRD techniques. Largest particle size of

TOPO-Zr-TiO2 was 16.1 nm at 950°C and below 750 °C band gap was 3.4 eV. Zr4+ and

p5+ ions did not reduced the band gap energy of T iO2 as they lie in valence and

conduction band regions (Chang et al., 2009).

Polyoxometalate-ZrO2 nanocomposite was synthesized by sol-gel method and

characterized by using SEM, TEM, XRD, FTIR analysis techniques. Photocatalyst was

used for oxidation of primary and secondary benzyl alcohols and was reused for several

times without appreciable loss of activity. Physical characterization was done by FTIR,

XRD, TEM, EET and UV-Vis. Spectroscopy. The average particle size was 15 nm and

surface area was 292 m²g-1 (Farhadi and Zaidi, 2009).

NiO-Bi2O3 nanocomposite was prepared by sol gel technique. It was

characterized by XRD and UV/Vis spectroscopy. The results showed the complete

alloying of two oxides. Photocatalytic activity test was performed by degrading

methylene blue and methyl orange dyes. 100 % methyl orange and 85 % methylene blue

were decomposed in 120 min. (Hameed et al., 2009).

By the modification of TiO2 two photocatalysts Porphyrin/TiO2 and Fe3+-

Porphyrin/TiO2 were prepared through chemisorption technique. Photocatalytic activity

of porphyrin and Fe3+-porphyrin Titanium dioxide was assessed by degrading

Rhodamine B (RhB) in aqueous solution under UV and visible light irradiation.

Porphyrin /TiO2 degraded about 50 % RhB under visible light irradiation. Porphyrin

and Fe3+ Porphyrin enhanced the activity under UV light. But under visible light only

Pr enhanced the activity (Huang et al., 2009).

13

ZnO nano particles were introduced into titanate nano tubes. ZnO/titanate

photocatalyst was characterized by TEM, BET, XRD and UV/Visible spectroscopy.

Hexagonal wartzite phase of ZnO was attached to titanate nano tubes in the nano

composite structure. Photocatalytic activity was determined by degrading Rhodamine B

under visible light (λ=420 nm) irradiation. About 97 % RhB was degraded in 12 hours

by ZnO/titanate 20 % and ZnO/titanate 40 % (Liu et al., 2009).

Re-TiO2 (Re = La, Pr, Nd, Sm, Eµ, Dy and Gd) nanocomposites were

synthesized by hydrolysis in aqueous solution by a low cost method. Photocatalysts

were characterized by SEM, BET, XRD, HRTEM, and UV-Vis Spectroscopy.

Photocatalytic activity was evaluated by degrading Orange II dye dissolved in water

under UV and Visible light (λ-254, 365 and 400 nm). Best activity was shown under

visible light. Nd doped TiO2 is commercially produced to use in self-cleaning paints.

(Štengl et al., 2009).

Visible light photocatalyst S-TiO2-ZrO2 was synthesized by one-step method.

The nanocomposite was characterized by XRD, TEM, XPS, DRS, FTIR, ESR and N2

adsorption desorption measurements. Addition of ZrO 2 inhibited the phase

transformation, enhanced visible light absorption and increased activity. MB

degradation was about 90 % by S-TiO2-ZrO2 calcined at 500 °C (Tian et al., 2009).

TiO2/P3HT photocatalyst was prepared by mixing poly (3-hexylthiophene) with

TiO2 nanoparticles in high speed blender using CHCl3 as solvent. Photocatalyst was

characterized by XRD, XPS, TEM, FTIR and UV-Vis-spectroscopy. It showed good

textural properties similar to that of individual oxides containing two isoelectronic ions.

TiO2/P3HT degraded 88.5% methyl orange in 10 h under visible light irradiation.

Photocatalyst was stable after 10 cycles of reuse. (Wang et al., 2009)a.

Bimetals co-doped Bi/Co-TiO2 and Fe/Co-TiO2 nanocomposites were

synthesized by stearic acid gel technique. Photocatalyst was characterized by XRD,

SEM and UV-Vis spectroscopy. Photocatalytic activity was evaluated by degrading

Rhodamine B in aqueous solution under visible light (λ> 400 nm). Fe (0.1 % - 0.4 %)-

TiO2 showed 100 % efficiency of degrading Rhodamine B in 240 min where Fe alone

had negative effect on activity. Fe/Co co-doped TiO2 was reused three times with a 15

% loss of activity in each reuse (Wang et al., 2009)c.

14

Nanocomposite of TiO2/ZrO2 by facile route containing 10-90 mole% TiO2 was

prepared and characterized by XRD and TEM analysis. Photocatalytic activity was

evaluated by degrading Rhodamine B under UV-light (λ= 365 nm) irradiation. 60:40

TiO2/ZrO2 calcined at 600 °C degraded 90 % RB in 60 min (Yuan et al., 2009).

Bio-mineralization technique was used to produce Cs/CdS nanocomposite.

Chitosan crosslinked nano CdS photocatalyst was characterized by XRD, TEM, SEM,

TGA and FTIR analysis techniques. Photocatalytic activity was assessed by degrading

congo red dye in aqueous solution under visible light through a UV cut off light filter

85.9 % congo red was degraded in 180 min (Zhu et al., 2009).

A magnetic nanophotocatalyst TiO2/SiO2/Ni Fe2O4 by was prepared by hydro

thermal, sol-gel and solvothermal techniques. It was characterized by SEM, TEM,

XRD, HRTEM, VSM and UV-Vis spectroscopy. Nanoparticles were spherical with 30

nm dia. Photocatalytic activity was assessed by basic violet -5 (BV-5) degradation in

aqueous solution under UV light irradiation. 97 % of BV-5 was degraded in 360 min.

Being magnetic photocatalyst was separated very easily by applying external magnetic

field and reused 5 times without appreciable loss of activity (Yuan et al., 2010).

Nanophotocatalyst ZrOx-ZnO with enhanced activity was prepared via cetyl

trimethyl ammonium assisted hydrothermal technique. Binary oxide photocatalyst was

characterized by XRD, XPS, SEM, BET and UV/Vis spectroscopy. ZrO x/ZnO

decomposed 88 % of Dimethyl phthalate within 30 min under microwave irradiations.

Photocatalytic activity of prepared catalyst was 15 % higher than Degussa P25 TiO2.

Half-life of DMP degradation was shortened 45 % as compare with P25 TiO2. Binary

photocatalyst was recycled 6 times with the same efficiency (Liao et al., 2010).

Magnetic photocatalysts MxBi1-xFeO3, (M=Mg, Al or Y) were prepared by citric

acid sol-gel technique and calcined at 600 °C for 3 hours. Nano sized ceramic alloys

were characterized by XRD, SEM, EDX, DR and SQUID measurements. Photocatalytic

activity was evaluated by degrading Rhodamine B (Rh.B) as standard test pollutant.

Under visible light (λ>400 nm) through a cut off filter YBiFeO3 degraded 18 % Rh.B

where BiFeO3 degraded 14 % RhB and P-25 TiO2 degraded 7 % Rh.B. being magnetic

in nature photocatalyst can be easily separated from reaction mixture by applying

external magnet. (Madhu et al., 2010).

15

A visible light responsive photocatalyst ZrTiO4/Bi2O3 was prepared by

hydrothermal technique. The synthesized catalyst was characterized by XRD, XPS,

DRS, PL and TEM analysis. Particle size of 7 nm was obtained when calcined at 450

○C. Photocatalytic activity was determined by degrading 4 -cholorophenol as a test

pollutant. 40 % degradation was achieved in 60 min of visible light irradiation by the

photocatalyst calcined at 450 ○C which is higher than the sample calcined at 400, 500

and 550○C and also from Degussa P25 TiO2. That was due to small particle size, higher

surface area and stronger absorption of visible light. Due to these properties

ZrTiO4/Bi2O3 is a candidate for alternative commercial photocatalyst (Neppolian et al.,

2010).

Nanoparticles of ZnCuS and ZnNiS were synthesized by co-precipitation

method. Appropriate stoichiometric solutions of ZnCl2 and NiCl2.6H2O were co-

precipitated with Na2S.9H2O solution. The precipitated nanoparticles were filtered,

washed, dried in an autoclave at 100 ○C for 2 hours. The nanocomposite photocatalyst

was characterized by XRD, TEM, AAS and UV-Vis spectroscopy. Photocatalytic

activity was determined by degrading congo red under UV-Vis irradiation. Zn0.94Ni0.06S

shoed about 95 % degradation of congo red in 120 min and Zn0.9Cu0.1S about 98% in

120 min. the catalyst was reused 4 times in the degradation process at the cost of 0.5 %

Zn loss (Pouretedal and Keshavarz, 2010).

N-Zr/TiO2 prepared by sol-gel method was studied for the effect of N and NZr

dropping. Phase structure, morphology, mean crystalline size, texture, thermal and

crystallization properties were studied by XRD, SEM, TEM, XPS, BET analysis. The

photocatalytic activity was evaluated by methylene blue (MB) degradation. The MB

degradation rate was 0.717/m as compare with P25 TiO 2 0.116/m. The rate of N-

Zr/TiO2 is 6.18 times greater than P-25 TiO2. Zr doped TiO2 nanomaterial have smaller

particle size, larger surface area higher thermal stability (Lucky and Charpentier, 2010).

Photocatalytic degradation of Methyl Orange and Acid Orange 7 was performed

with WOx/TiO2 under visible light (λ>420 nm). 4.2 % WOx/TiO2 photocatalyst showed

best activity by decolorizing 100% Methyl Orange and Acid Orange 7 in 300 min a nd

240 min respectively. Decolorization of the dyes was investigated with changes in

absorption spectra. Effect of photocatalyst concentration, pH and initial concentration

16

of dye was noted. Photocatalyst was reused for degrading dyes. The nanocomposite was

subjected to XRD, DRS, TEM and EDX analysis (Sajjad et al., 2010).

Fe-TiO2 photocatalyst was synthesized by using hydrothermal technique.

Nanocomposite was characterized by XRD for detection of Fe 2O3 and TiO2.

Photocatalytic activity was assessed by degrading phenol in water solution under

different wavelengths of light irradiation. (λ = 190 -250, 390, 405 nm and sunlight).

About 8 % phenol was degraded under sunlight in 24 hours. Effect of solution

temperature and pH was also observed. The degradation reaction obeyed I st order

kinetics (Shawabkeh et al., 2010).

Ag/V-TiO2 nanophotocatalyst synthesized by sol-gel-solvothermal technique

was characterized by XRD and TEM analysis techniques. Particle size and band gap

energy were 12 nm and 2.25 eV. Photocatalytic activity was determined by degrading

Rhodamine B (RhB) and Coomassie Brilliant Blue G-250 (CBB) in water solution

under UV and visible light (λ = 313 nm and 420 nm respectively) irradiation. Ag/V

TiO2 (1.8 Ag, 4.9 V) was the best catalyst which degraded 62 % RhB and 100 % CBB

in 240m under visible light irradiation (Yang et al., 2010)a.

Hydroxyapatite (Fe3O4/HAP) was prepared via homogeneous precipitation

technique nanophotocatalyst was characterized for its physical parameters by TEM,

FTIR and XRD analysis. Diameter of spherical particles was 25 nm. Photocatalytic test

was performed by degrading diazinon under UV light irradiation. About 75 % of

diazinon was degraded in 60 min. Magnetic nature of nanoparticles helped in the

separation of catalyst from reaction mixture by an external magnet. The photocatalyst

could be reused 7 times with 7 % loss of activity (Yang et al., 2010)b.

Sol-gel technique was used to synthesize TiO2/ZrO2 nanocomposite and

subjected to XRD, TEM, UV-Vis spectroscopy and fluorescence emission spectra

techniques. Nanocomposite contained anatase TiO2 and tetragonal ZrO2. Photocatalytic

activity was determined by the degradation of methyl orange under UV light irradiation.

The catalyst with Ti/Zr ratio 15.2 % showed best activity of 60 % in 105 min. The same

catalyst was reused 5 times with no less of activity (Zhang and Zeng, 2010).

Mn-ZnO nanoparticles were prepared using co-precipitation technique. 75 mmol

solution of (CH3COO)2 Zn in ethanol was mixed with ethanolic solutions of

17

(CH3COO)2 Mn. Mixture solution was heated at 75 °C for 45 min and cooled to room

temperature. NaOH solution was added with stirring (150 rpm) till 8.3 pH was reached.

Resulting precipitates were separated by centrifuging at 4000 rpm for 20 min. washed

with C2H5OH and dried at 110 °C for 12 h. The sample was ground and calcined at 650

°C for 3h. Photocatalyst was characterized by XRD, SEM, TEM, EDX, BET and UV-

Vis reflectance for band gap measurements. Band gap of 1 % Mn-ZnO was 2.2 eV. 1 %

Mn-ZnO4 degraded 88 % O-cresol in 360 min under visible light irradiation (Abdollahi

et al., 2011).

Vanadium-doped TiO2–montmorillonite (MMT) nanophotocatalyst was prepared

by sol-gel method and characterized by XPS, TEM, XRD, DRS, FTIR and N2

adsorption isotherms. V-TiO2 MMT has smaller particle size than TiO2 and V-TiO2.

The photocatalytic activity was estimated by degrading sulpho rhodamine B (SRB)

under visible light λ=450 nm through a cutoff filter. About 65 % SRB was degraded in

18 h by V-TiO2 MMT where the ratio of Ti/MMT was 120 mmol/g (Chen et al., 2011).

Mixed metal oxide (MMO) of Zn-Al-In nanocomposites was synthesized by

chemical co-precipitation method. The solutions of Zn(NO3)2.6H2O, Al(NO3)3.9H2O

and In(NO3)3.4H2O with the molar ratio Zn/Al-In = 3.0 and In/Al-In = 0.3, 0.5 and 0.7

were co-precipitated with 0.24 M NaOH and 0.1 M Na2CO3 solutions. Alkali solutions

were added drop wise up to pH 10. Suspension was kept at 60 ○C for 6 hr. the

precipitate were filtered, washed, dried and calcined at 500 ○C for 4 hr. The prepared

photocatalyst was characterized by XRD, NMR. TEM, N2 adsorption and UV/Vis

defused reflectance spectroscopy. Photocatalytic activity was determined by degrading

Methylene Blue dye in H2O solution. MMO with molar ration 0.5 degraded MB up to

73 % in 240 min under visible light (λ>420 nm) irradiation. Band gap energy of the

sample was 2.50 eV (Fan et al., 2011).

A thin film of W-TiO2 synthesized by liquid phase deposition method was

characterized by XRD, XPS, EDX, SEM techniques. 1 -7 % W doping transferred

absorption wavelength into visible light range which was confirmed by UV-Vis

spectroscopy. Photocatalytic activity was determined by degrading dodecyl benzene

sulfonate (DBS). 5 % W-TiO2 film degraded 84.8 % DBS in 4 hour which was

18

improved up to 92 % in 90 min under +1.0 anodic bias potential under visible light (λ

>540 nm) irradiation (Gong et al., 2011).

Synthesis of C-doped Zn(OH)2V2O7 nanorods was done by hydrothermal

technique. Photocatalyst was characterized by XPS, DRS, SEM and XRD analysis

photocatalytic activity was estimated by methylene Blue (MB) degradation. Visible

light activated catalyst degraded about 90 % MB in 30 m. Dye decoloration obeyed

kinetics of first order reaction. The doped carbon was in free and carbide form on the

surface of nanorods (Guo et al., 2011).

Nanorods and nanotubes of N-TiO2 was prepared by solvothermal method

and characterized by XRD, TEM and UV-Vis spectroscopy. The N2 doping shifted the

band gap from 3.2 eV to 2.05 eV of nanorods and 2.40 eV of nanotubes which shifted

absorbance edge 605 to 504 nm. N-TiO2 nanotube degraded 70 % of methyl orange in

10 hours of visible light irradiation. BET surface area was 247 m²g -1 (He and He, 2011).

Er3+-TiO2 photocatalyst was synthesized by sol-gel method. Fibrous film was

made by electro spinning. Particle size was reduced from 18 nm to 8 nm when doped Er

was changed from 0-1.5 mol %. Photocatalyst was characterized by XRD, SEM, TEM

and UV-Vis spectroscopy. The absorption edge shifted towards red light. Acid

synergetic combination of e- with Er3+ resulted in higher activity under visible light.

Photocatalytic activity was estimated by degrading di fferent dyes i.e. orange-I and

methylene blue dyes by visible light activation (Lee et al., 2011).

Sol-gel technique was used to synthesize P-TiO2 nanophotocatalyst and the

photocatalyst was characterized by XRD, SEM, TEM, BET and UV-vis

spectrophotometry. Photocatalytic activity was determined by degrading rhodamine

B(RhB) under solar light irradiation. Degradation %age of RhB could be attained up to

70 % in 10 h of irradiation (Lv et al., 2011).

ZrO2-TiO2 was prepared by sol-gel method. ZrO2 percentage ranged from 0.5 –

4.0 percent of metal contents. The catalyst was calcined at 700 ○C. the ZrO2-TiO2 was

subjected to XRD, and TEM analysis. Particle size was below 10 nm. Photocatalytic

activity was measured by degrading phenol under UV light (λ ≤ 365 nm). Degradation

was measured by UV/Vis spectrophotometer. 1 % Zr-TiO2 calcined at 700 ○C gave

highest degradation rate of phenol. The catalyst was reused 5 times without any loss of

19

activity. Percentage degradation of phenol was calculated by the formula % DE = (C o –

Ct)/Co x 100. Where Co is initial concentration of phenol and C t concentration of phenol

at time T (McManamon et al., 2011).

Bovine serum albumin capped CdS nanocrystals were prepared by precipitation

method and characterized by XRD, TEM and UV-Vis spectroscopy. Particle size was in

between 3.1-3.8 nm. Photocatalytic activity up to 86 % was obtained from degradation

of methylene blue under visible light (λ -653 nm) irradiation in 7 hour. This bovine

serum albumin (BSA) capped CdS have great potential application in industry (Pathania

et al., 2011).

W/TiO2 nanocomposite was prepared by sol-gel technique. Sample was

subjected to XRD analysis. Photocatalytic activity was determi ned by degrading 2-

chlorophenol (2-Cp) 0.4 % W-TiO2 completely removed 2-Cp in 120 min under blue

light irradiation. The degradation was 75 % of the degradation of P-25 TiO2 under UV-

irradiation. Photocatalytic activity was independent of crystalline structure and showed

Ist order reaction kinetics (Putta et al., 2011).

Nanocomposite of CuO-ZnO was synthesized by wet impregnation process and

calcined at 550 °C for 5 hours which changed the sample from purple to grey color.

Photocatalyst was characterized by XRD, TEM, XPS, DRS techniques. Photocatalytic

activity was determined by degrading Acid Red-88 (AR-88). Activity of CuO/ZnO was

2 times greater as compare with bare CuO and ZnO. Total organic carbon (TOC) was

also removed after decolorization of AR-88 (Sathishkumar et al., 2011).

Magnetic nanocomposite CoFe2O4–Cr2O3–SiO photocatalyst was synthesized by

co-precipitation technique. Band gap energy of nanocomposite was 3-4 eV,

Photocatalytic activity was evaluated by Methylene Blue (MB) degradation under UV

light irradiation. About 90 % MB was degraded in 120 min in the first cycle, 88 % in

the second cycle and 86 % in third cycle. Photocatalyst being magnetic can be easily

separated by applying external magnetic field (Senapati et al., 2011).

WO3/BiOCl was prepared by wet impregnation process. Nanocomposite was

characterized by XRD, SEM, TEM, RS, EDX, N2 absorption and thermo gravimetric

analysis. WO3/BiOCl heterojuction nanocomposite shifted the absorption edge to

visible region photocatalytic efficiency was determined by degradation of rhodamine B

20

(RhB). 10 % WO3/BiOCl degraded RhB completely in 180 min under visible light (λ

<420 nm) through a cutoff glass filter. Degradation reaction showed 1st order kinetic

(Shamaila et al., 2011).

Zr–I–TiO2 was synthesized by hydrolysis technique and calcined at 400-600 ○C.

Nanophotocatalyst was characterized by XRD, TEM, XPS and UV/Vis spectroscopy.

Photocatalytic activity was measured by decolourizing the Methyl orange (MO) in

visible light (λ > 400 nm). Particle size was nearly 10nm and band gap energy of 5 %

Zr-I-TiO2 was 2.52 eV. It degraded 94 % MO in 240 min. Zr on the surface of TiO2

increased the active sites resulting in enhancement of Photocatalytic activity (Song et

al., 2011).

Highly efficient, visible light induced TiO2 photocatalyst was prepared by sol-

gel technique at temperature ≤300 °C nanophotocatalyst was characterized by XPS,

TEM, FTIR, XRD, UV-Vis, DRS and DSC-TGA techniques. Photocatalytic activity

was determined by degrading methyl orange using visible light (λ ≥ 400 nm) TiO 2

nanoparticles have anatase phase with carbon self-doping. Photocatalytic activity of

prepared TiO2 particles is much higher than P25-TiO2, PPY/TiO2, P3HT/TiO2,

PANI/TiO2 N-TiO2 and Fe3+-TiO2. TiO2 (270 °C, 0.5 h) showed the best activity of 80

%. MO degradation in 120 min under visible light irradiation (Wang et al., 2011)b.

Visible light induced CdS/La2Ti2O7 nanophotocatalyst was synthesized by sono-

chemical technique. Photocatalyst was characterized by TEM, SEM, XRD, UV-Vis

diffuse reflectance spectroscopy. Photocatalytic activity was estimated by methyl

orange degradation. Photo catalytic activity of 99 % was achieved with (La/Cd= 1:3) in

140 min. Low band gap energy of the photocatalyst make it responsive in longer

wavelength i.e. visible range (Wang et al., 2011)c.

Fe3+-TiO2 was supported at natural zeolite to make the photocatalyst easily

separateable and to enhance its activity. Photocatalyst was characterized by XRD,

FTIR, UV-Vis spectroscopy, DRS, SEM and EDX analysis. Photocatalytic activity was

evaluated by degrading methyl orange as a test pollutant. Photocatalytic activity was

optimum at 6 % Fe/TiO2/Zeolite. Fe+3 concentration affects the photocatalytic activity

of the sample forming Fe-O-Ti bond 5 % Fe enhanced the activity and there was

decrease in activity from 7 % Fe. (Wang et al., 2011)a.

21

CNTs/P-TiO2 nanocomposite prepared by hydrothermal technique was

characterized by XRD, XPS, TEM, BET, FTIR, TG-DSC, UV-Vis and DRS analytical

techniques. Methyl orange (MO) dye in solution was degraded to determine the

photocatalytic activity of nanocomposite. 95 % MO was decomposed with CNTs/P-

TiO2 photocatalyst in 240 min of visible light irradiation (λ > 410 nm) through a cut off

UV filter (Wang and Zhou, 2011).

Magnetic and optical nanophotocatalyst Fe3O4/ZnO with different composition

was prepared by facile route. The morphology and physicochemical properties were

studied by applying FTIR, TEM, XRD, VSM and UV-Vis spectroscopy. Photocatalytic

activity was estimated by degrading methyl orange (MO) dye in aqueous solution. 93.6

% degradation of MO was achieved in 60m of irradiation under visible light, pH = 7,

concentration of catalyst 0.51 mgL -1 and concentration of MO = 6x10-5 molL-1. Being

magnetic photocatalyst can be recycled easily. There is a 30 % decrease in activity after

5 times use of catalyst 10 % Fe3O4/ZnO molar ratio was optimal for Fe3O4/ZnO4 bi-

functional nanophotocatalyst (Xia et al., 2011).

Ag/MWCNTs nanophotocatalyst was developed by photo reduction and thermal

decomposition techniques. Ag/MWNTs catalyst was characterized by FE -TEM, XPS,

and UV-Vis spectroscopy. Photocatalytic activity of prepared photo catalyst was

determined by degrading Rhodamine B (RhB) as test pollutant under visible light

irradiation. About 55 % degradation of RhB was achieved by 3 % Ag/MW CNTs in 6

hours of visible light irradiation. Photocatalyst prepared by thermal decomposition

showed better results as compared with photo reduction (Yan et al., 2011).

MgFe2O4/TiO2 nanophotocatalyst was prepared by mixing of nano TiO2 & nano

MgFe2O4 and then calcined at 500 °C for 2 hour. The optimal composition was 3 weight

percent MgFe2O4 and optimal annealing temperature was 500 °C. Nanocomposite was

characterized by SEM, TEM, XRD, UV-Vis spectroscopy and N2 sorption. Crystal size

of 2 % MgFe2O4/TiO2 calcined at 500 °C was 24.56 nm and surface area 43 m²g-1. This

catalyst degraded about 90 % Rhodamine B under visible light irradiation in 180 min

(Zhang et al., 2011)a.

An efficient visible light induced photocatalyst ZrO2-Bi2WO6 was

prepared by hydrothermal technique. The photocatalyst was characterized by XRD,

22

TEM, DRS, XPS, PL spectra. Photocatalytic activity test was carried out by degrading

Rhodamine B (RhB) and phenol under visible light (λ >420 nm) irradiation. RhB was

completely removed in 20 min in 3 mol percent Zr and 60% phenol was degraded in

120 min. Photo catalyst was reused five times without appreciable loss of activity

(Zhang et al., 2011)c.

Visible light photocatalyst AgBr/Ag3PO4 hybrid was synthesized by ion

exchange method. Photocatalyst was characterized by XRD, FE -SEM, EDS and DRS

analysis. AgBr/Ag3PO4 6:4 hybrid degraded 95.1 % methyl orange (MO) in 50 min with

visible light irradiation (λ > 420 nm) which is higher than AgBr or Ag3PO4 alone. In the case

of MO dye there is possibility of dye sensitization. To remove this ambiguity a colorless

pollutant was also degraded efficiently. TOC removal of MO was 51.8 % after irradiation in

50 min and that of phenol was 22.5 % in 100 min. MO was first degraded to colour less

products and then into CO2 and H2O. photocatalytic efficiency was decreased upto 5 % in 4

cycles and upto 19 % after 5 cycles of reuse (Cao et al., 2012).

Sulfanilic acid modified TiO2 nanoparticles were prepared by hydrothermal

method and characterized by XRD, SEM, XPS, FTIR and UV-Vis spectroscopy. The

photocatalytic activity of catalyst was determined by congo red decoloration under

visible light irradiation through a cutoff filter (λ >400 nm). TiO2/SA degraded about 90

% Congo red dye in 210 m. The used photocatalyst was separated and dried at 80 °C for

5 hour and recycled 7 times with 15 % total loss of activity (Guo et al., 2012).

Nanocomposites of Fe2O3-ZrO2/Al2O3 were supported at Al2O3 by sol-gel

technique. Nanophotocatalyst was characterized by SEM, TEM, XRD, XPS, ICP-AES

and N2 sorption. Nanocomposite contains iron as λ-Fe2O3 monoclinic, zirconium as

tetragonal ZrO2 and aluminum as Al2O3. Photocatalytic activity was estimated by

degrading phenol in aqueous media. 93 % of phenol was degraded in 120 min under

UV-light irradiation in the presence of H2O2. Band gap energy of Fe2O3-ZrO2 2.68 ev

and Al2O3 = 3.92 eV (Liu et al., 2012)b.

N doped GaZn mixed oxide was synthesized by solid state reaction. Catalyst was

characterized for its structural, electronic and optical properties by XRD, SEM, TEM, SAED,

XPS and UV/Vis-DRS techniques. N-GaZn calcined at 500 °C degraded 54 % of 100 ppm 4-

Chloro-2-Nitrophenol solution in 4 h under direct sunlight irradiation. The band gap energy

23

of photocatalyst was 2.6 eV. Nitrogen contents, surface area, PL intensity and band gap

energy enhanced the photocatalytic activity of nanophotocatalyst (Martha et al., 2012).

Nanoparticles of CdS synthesized by precipitation method and Cd++ were

exchanged into zeolite. Photocatalyst was characterized by XRD, SEM and FTIR

analysis. Photo catalytic activity of the catalyst was determined by the degradation of

86 % crystal violet dye (CV) in 60 min under sunlight. 92 % decrease in COD and

change of TOC was also determined. Sunlight assisted catalyst was reused 4 time with

20 % loss of activity. Photocatalyst was recommended the complete mineralization of

pollutants in waste water (Nezamzadeh-Ejhieh and Banan, 2012).

Three types of photocatalysts ZrO2/SnO2, ZrO2/CeO2 and SnO2/CeO2 were

prepared using sol-gel method and calcined at 550 ○C. Characterization of synthesized

catalysts was done by applying XRD, TEM and IR Spectroscopy XRD patterns

confirmed the monoclinic and tetragonal phases of ZrO 2. Photocatalytic activity

experiments were performed by degrading 2 -nitro-phenol. ZrO2/SnO2 1:4 at pH 5

showed best activity by degrading 90 % 2-nitro phenol in 240 min. Photocatalyst was

reused 5 times with loss of 50 % activity. Used catalyst was removed from the reaction

mixture washed and dried at 80 ○C for 2 h at the end of each cycle (Pouretedal et al.,

2012).

Ag/AgCl nanophotocatalyst was synthesized. The composite material was highly

activated with visible light. The absorption ability was increased by increasing etching time,

the samples were characterized by X-ray Diffractrometery, X-ray Photoelectro Spectroscopy,

SEM and X-ray Energy Dispersive Spectroscopy. Photocatalytic activity was determined by

methyl orange which was decomposed 96 % in 40 min of visible light irradiation. The

catalyst was remained stable during degradation process. The reaction mechanism was also

proposed (Xu et al., 2013).

Nanoparticles of Zn0.5Co0.5Al0.5Fe1.46La0.04 O4 were synthesized by flash auto

combination method and blend them with PVP, PVA, PVAc and PEG polymers as capping

agents. The coating strategy controls the agglomeration of ferrites nanoparticles and

produced a well-designed core-shell nano-assembly with enhanced physical properties. XRD

and HRTEM confirmed the formation of ferrite as a core surrounded by polymeric

properties. All prepared samples were effective in removing dyes from waste water which

24

was cleared from color index analysis, 90 % efficiency was given by

Zn0.5Co0.5Al0.5Fe1.46La0.04O4 /PVP nanocomposite as compared with 76 % with pure ferrite

sample. Polymer blended ferrite in the form of core-shell were better in all respects (Ahmed

et al., 2013).

ZnFe2O4 magnetic nanoparticles were prepared by microwave assisted hydrothermal

method for the degradation of Acid Red 88 dye, Nanoparticles were characterized by XRD,

TEM, SEM, BET, ICP-AES and FTIR analysis. While degrading acid dye concentration (10-

56 mg/L), pH (3.2-10.7) and temperature of bath (20-60 ᴼC) were optimized. Decolorization

of the dye followed the pseudo 2nd order kinetics, Dye was adsorbed by nanoparticles

spontaneously and exothermally (Konicki et al., 2013).

ZnFe2O4 magnetic nanoparticles were prepared for the photocatalytic decolorization

and mineralization of dyes reactive red 198 and reactive red 120. The particles were prepared

by hydrothermal method and calcined at 600 ○C for 1 hour. Nanoparticles were characterized

by XRD, SEM and FTIR analysis. Decolorization of dyes was studied by UV/Vis

spectrophotometer. Initial concentration of dye, salt concentration and concentration of

catalyst were studied under UV radiations (200-280 nm). It was conducted that ZnFe2O4

nanoparticles could be used to degrade and mineralize the colored waste water (Mahmoodi,

2013).

Porous ZnFe2O4 film was fabricated through a template-assisted route and the sample

was calcined at 900 ○C for 3 h. The sample was analyzed by XRD, SEM, EDS, AFM and

ICP-EAS techniques. Photocatalytic activity was measured by degrading rhodamine B dye in

aqueous solution under visible light (> 420 nm) at 25 ○C. Porous ZnFe2O4 film degraded 80

% rhodamine B while ZnFe2O4 powder prepared by solid state method degraded 60 % of dye

in 8 hours. ZnFe2O4 film was recycled five times without any appreciable loss of activity. So

the photo degradation of organic pollutants in industrial waste water can be done successfully

(Nan et al., 2013).

Bismuth ferrite nanoparticles synthesized by sonication for 15 min at 35 ○C were

characterized by XRD and TEM analysis. Nanoparticles exhibited the band gap energy of 2.2

eV with excellent chemical stability. Small sized crystalline nanoparticles degraded 100 %

25

methylene blue in 30 min at pH 12 under sunlight irradiation. COD reduction was 83 %.

Initial concentration of dye had significant effect on rate of reaction. Degradation reaction

obeyed pseudo first order kinetics. Bismuth ferrite nanoparticles can be used to degrade the

organic pollutants in colored waste water (Soltani and Entezari, 2013).

Lanthanum ferrite nanoparticles were prepared by emulsion technique at room

temperature. Nanophotocatalyst was characterized by XRD, SEM, TEM, FT-IR, XRF and

UV/Vis spectroscopy. Nanoparticles were sharply crystalline and well dispersed provskite

phase. The band gap energy was 2.43 eV and particle size 32.68 nm. Photocatalytic activity

of the photocatalyst was estimated by degrading Toluidine Blue O (TBO) under visible light

irradiation. TBO was completely degraded after 90 min. Author proposed that

nanophotocatalyst has potential for industrial applications (Abazari et al., 2014).

Co0.6Zn0.4Cu0.2 Cdx Fe1.8 – xO4 (x= 0.2, 0.4, 0.6, 0.8) was synthesized by sol-gel auto-

combustion technique. Cd+2 substitution changed significantly magnetic, electrical and

structural properties of the ferrite. Nano crystalline ferrite was characterized by XRD, VSM

and UV/Vis spectroscopy. The particle size of nanocrystal was between 33–37 nm (calcined

at 1000 ᴼC). Pore size was increased with increasing Cd+2 concentrations. Photocatalytic

activity was evaluated by methyl orange dye degradation in water solution under visible light

irradiation. Photocatalytic activity of the sample containing Cd+2 (x=0.8) calcined at 1000 ○C

was 100 % after 1 hour of reaction. The catalyst could be easily separated by external magnet

for reuse (Bhukal et al., 2014).

Magnetic CoxNi1-xFe2O4 nanoparticles were prepared by hydrothermal method.

Physical characterization was performed by XRD, SEM, BET and VSM techniques. Congo

red in aqueous solution was used to determined adsorption capacity of cobalt nickel ferrite.

Sample with x= 0.3 gave largest adsorption capacity while the sample with x= 0.5 showed

the quickest adsorption. Adsorption reaction showed the pseudo 2 nd order kinetics. Best

magnetic properties were showed by the sample prepared at 140 ○C for 2 hours. The cobalt

nickel ferrite were good adsorbent to treat waste water containing congo red dye (Chen et al.,

2014).

26

Core-shell TiO2-SiO2/CoFe2O4 photocatalyst was developed such that CoFe2O4 was

synthesized by organic acid precursor technique. TiO2-SiO2 was prepared and coated onto

CoFe2O4 by sol-gel method. In this core-shell CoFe2O4 acts as core and TiO2-SiO2 as shell.

Characterization of photocatalyst was done by XRD, SEM, TEM, XPS, FTIR techniques.

Photocatalytic activity was determined by degrading methylene blue in aqueous solution

under UV light. 98.3 % methylene blue was degraded in 40 min. Efficiency of photocatalyst

was dependent on initial concentration of the dye, pH of the reaction solution and catalyst

dosage. The photocatalyst was separated from the reaction mixture by external magnet and

recycled six times with 4 % loss of activity. The loss of activity was due to the occupation of

active sites of photocatalyst by reaction intermediates (Harraz et al., 2014).

A magnetically ordered mesoporous copper ferrite was developed by nano-casting

with 122 m2/g surface area and 9.2 nm pour size. Meso-CuFe2O4 was characterized by XRD,

SEM, TEM, FT-IR, XPS and Raman Spectra technique. Catalytic activity was determined by

degrading imidaclopride, 100 % removal of imidaclopride took place in 5 hours. The reaction

followed pseudo first order kinetics. Hydroxyl radicles were responsible for the degradation

reaction and their generation was proportional to the degradation efficiency. Iron leaching

from Meso-CuFe2O4 was very low even in acidic solution. The catalyst did not loss activity

in 5 cycles of reuse. The magnetic nanophotocatalyst is a potential candidate for the removal

of organic pollutants (Wang et al., 2014)b.

N-doped TiO2/ZnFe2O4 photocatalyst was synthesized via vapor thermal technique.

Photocatalyst was characterized for is physico-chemical properties using spectroscopic and

microscopic analysis. N-doped TiO2/ZnFe2O4 showed improved photodegradation of dyes as

compared with TiO2/ZnFe2O4 and ZnFe2O4. Being magnetic photocatalyst it could be easily

isolated from reaction mixture using external magnetic field. The synthesized photocatalyst

could be used effective and conveniently for the treatment of waste water (Yao et al., 2015).

N, Zr co-doped mesoporous TiO2 photocatalyst was prepared by solution combustion

synthesis technique. Photocatalyst was characterized by XRD, TEM, BET, XPS and UV-Vis

diffuse spectroscopy. Z-Zr co-doping increased the BET surface area as well as

photocatalytic efficiency. Band gap of N-Zr-TiO2 was between 2.17 to 2.76. Doping of 10 %

27

Zr showed highest photocatalytic efficiency. It was also found that synthesized photocatalyst

was highly dispersable (Liu et al., 2015).

TiO2/ZrO2 was prepared using sol-gel technique. TiO2/ZrO2 photocatalyst was

characterized by XRD, TEM, SEM and TDA/TGA analysis techniques. Tetrahedral ZrO2 and

anatase TiO2 phases were present. The particles were spherical with 10.5 nm diameter. Result

showed increased in band gap energy and decreased in recombination rate of charge carriers

6.0 % ZrO2 addition showed maximum degradation of an azo dye Ponceau BS under UV

light irradiation (Pirzada et al., 2015).

28

CHAPTER 3

MATERIALS AND METHODS

This project was designed regarding current environmental issues to treat the textile

wastewater and achieve maximum mineralization of dyes and other textile auxiliaries that are

frequently present in wastewater. Two nanophotocatalysts were synthesized and

characterized. Colored waste water was treated with theses photocatalysts. Water quality

parameters like chemical oxygen demand (COD), total organic carbons (TOC), total

suspended solids (TSS), Toxicity and mineralization test had been performed. All sort of

research work has been performed in chemistry laboratory, Department of Chemistry

University of Agriculture Faisalabad and School of Chemistry and Molecular Biosciences,

University of Queensland, Australia.

3.1. Apparatus and Chemicals

3.1.1. Apparatus:

Following apparatus was used in research work:

Volumetric flasks (Pyrex)

Pipettes (Pyrex)

Measuring cylinders (Pyrex)

Beakers (Pyrex)

Funnels (Pyrex)

Screw-cap vials (Pyrex)

Three neck flask (Pyrex)

3.1.2. Chemicals:

Following chemicals were used in this research work. All chemical were purchased

from Sigma-Aldrich and used without any further purification.

29

Remazol Black B (CI Reactive Black 5)

Methyl Orange (C.I. 13025)

Methylene Blue (C.I. 52015)

Silver Sulphate

Potassium hydrogen phthalate

Potassium dichromate

Mercury sulphate

Sulphuric acid (98%)

Sodium hydroxide

Glucose

Sodium sulphate

Sodium hydrogen phosphate

Aluminum Chloride

Zirconium Chloride

Zinc Chloride

Ferric Chloride

3.2. Instruments

Mechanical Stirrer (IKA RW 20 Digital)

Heating Mantle (SGS 98-I-B)

Hot plates (IKA RCT Basic)

Digital thermometer (Thermoprobe TL1W)

100 watt Ultra sonic bath with operating frequency 40 kHz (Unisonics FXP12MH)

Scanning Electron Microscope (Philips XL 30)

UV-Visible spectrophotometer (Agilent Cary 60 UV-Vis)

Turbo-Pumped Sputter Coater (Quorum Q150T)

Zeta Sizer (Malvern Nano ZS)

X-ray Diffractometer (Bruker D8 Advance)

Nitrogen Adsorption Surface-Area Pore Size Analyzer (Micromeritics Tristar 3000)

30

3.3 Chemical co-precipitation

Co-precipitation is a simple method for the synthesis of nanoparticles. In this method

low temperature and less time is required as compare with hydrothermal, solvo thermal and

thermal decomposition. Water is used as solvent which is cheap and environmental friendly,

product yield is high and scalable but size and shape of particles is a little inferior. It is a

facile easy and simple method to prepare nanoparticles from metallic salt solutions. Mixture

of salt solutions is co-precipitated by adding a base with vigorous stirring at room

temperature or at elevated temperature in the absence of reactive oxygen (Faraji et al., 2010).

A pH range 8 to 14 is required for complete precipitation of stoichiometric ratio Fe+++: = 2:1

in an inert atmosphere (Iida et al., 2007).

In this project two types of nanophotocatalysts (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-

x(ZnO)xFe2O3 (x = 0, 0.25, 0.50,0.75 and 1) were synthesized by two different methods of co-

precipitation.

i) Co-precipitation by mechanical stirring

ii) Co-precipitation by ultra-sonic assisted mechanical stirring

3.3.1 Co-precipitation by mechanical stirring

In this method co-precipitation was done in three necks round bottom flask of 500 ml

fitted with mechanical stirrer and heating mantle to provide heat to the reaction mixture. One

neck of the flask was used to introduce the ammonia solution through a variable speed

dispenser, one for stirrer and one for the thermometer to note the temperature of the reaction

mixture during the reaction. Reaction conditions used are, temperature 65○C , stirring speed

500 rpm, ammonia solution 30-40 drops/min and the end point was pH = 10.

3.3.2 Co-precipitation by ultra-sonic assisted mechanical stirring

This method was newly developed. In this method co-precipitation was done under

the influence of ultra-sonic radiations during mechanical stirring. The reaction was

performed in a 500 ml three neck flask placed in temperature controlled ultra-sonic bath, an

overhead mechanical stirrer and variable speed dispenser was used for the drop wise

31

introduction of ammonia solution. Reaction conditions used are, temperature 65○C, stirring

speed 500 rpm, ammonia solution 30-40 drops/min and the end point was pH = 10.

3.4 Synthesis of (Al2O3)1-x(ZnO)xFe2O3

Stock solutions of normality 1 were prepared for AlCl3, ZnCl2 and FeCl3.6H2O in

deionized water. 100ml of solutions of both ZnCl2 and AlCl3 were prepared from stock

solutions against the different values of x and labeled as solution A and B respectively.

100ml of 1 normal FeCl3.6H2O solution was used for each value of x and labeled as solution

C. Solution A, B and solution C were mixed slowly with continuous stirring, heated up to

65○C (Behrens et al., 2011), stirred for 30 min at the same temperature. To precipitate

chloride precursors the pH of solution was raised by adding 30% ammonia solution drop

wise with constant stirring to gain pH = 10 (Hessien et al., 2008), this process took 2 hours.

The resulting mixture was kept stirring for another 60 min. The resulting precipitates of

(Al2O3)1-x(ZnO)xFe2O3 were centrifuged and washed with deionized water till chloride free

and a final washing with absolute alcohol (Ren et al., 2012).

Table No. 3.1 Normal amounts of AlCl3, ZnCl2 and FeCl3 used for the synthesis of


Value

of x

Normality of 100 ml solutions (Al2O3)1-x(ZnO)xFe2O3

AlCl3

Solution A

ZnCl2

Solution B

FeCl3

Solution C

0 1.00 0.00 1.00 Al2O3.Fe2O3

0.25 0.75 0.25 1.00 (Al2O3)0.75(ZnO)0.25Fe2O3

0.50 0.50 0.50 1.00 (Al2O3)0.5(ZnO)0.5Fe2O3

0.75 0.25 0.75 1.00 (Al2O3)0.25(ZnO)0.75Fe2O3

1 0.00 1.00 1.00 ZnO.Fe2O3

Washed precipitates were dried at 80○C for 24 h in an electric oven and cooled to

room temperature. These were ground in agate pestle and mortar to fine powder and divided

into 3 portions a, b and c. sample a was calcined at 400○C and sample b was calcined at

600○C for four hours and sample c was left uncalcined these samples of nanophotocatalysts

32

were stored in glass bottles kept at a dry place for further use (Bo et al., 2007; Shao et al.,

2014).

The above same process was used for the synthesis of nanophotocatalysts (Al2O3)1-

x(ZnO)xFe2O3 by ultrasonic assisted mechanically stirred co-precipitation only the difference

was in arrangement of apparatus as given in section 3.3.

3.5 Synthesis of (ZrO2)1-x(ZnO)xFe2O3

Stock solutions of normality 1 were prepared for ZrCl4, ZnCl2 and FeCl3.6H2O in

deionized water. 100ml of solutions of both ZnCl2 and ZrCl4 were prepared from stock

solutions against the different values of x and labeled as solution A and B respectively.

100ml of 1 normal FeCl3.6H2O solution was used for each value of x and labeled as solution

C.

Table No. 3.2 Normal amounts of ZrCl4, ZnCl2 and FeCl3 used for the synthesis of


Value

of x

Normailty of 100 ml solutions (ZrO2)1-x(ZnO)xFe2O3

AlCl3

(Solution A)

ZnCl2

(Solution B)

FeCl3

(Solution C)

0 1.00 0.00 1.00 ZrO2.Fe2O3

0.25 0.75 0.25 1.00 (ZrO2)0.75(ZnO)0.25Fe2O3

0.50 0.50 0.50 1.00 (ZrO2)0.5(ZnO)0.5Fe2O3

0.75 0.25 0.75 1.00 (ZrO2)0.25(ZnO)0.75Fe2O3

1 0.00 1.00 1.00 ZnO.Fe2O3

Solution A, B and solution C were mixed slowly with continuous stirring, heated up

to 65○C (Behrens et al., 2011), stirred for 30 min at the same temperature. To precipitate

chloride precursors the pH of solution was raised by adding 30% ammonia solution drop

wise with constant stirring to gain pH = 10 (Hessien et al., 2008), this process took 2 hours.

The resulting mixture was kept stirring for another 60 min. The resulting precipitates of

(ZrO2)1-x(ZnO)xFe2O3 were centrifuged, filtered under vacuum and washed with deionized

33

water till chloride free and a final washing with absolute alcohol (Ren et al., 2012). Washed

precipitates were dried at 80○C for 24 h in an electric oven and cooled to room temperature.

These were ground in agate pestle and mortar to fine powder and divided in to 3 portions a, b

and c. Sample a was calcined at 400○C for four hours and sample b was calcined at 600○C for

four hours and sample c was left uncalcined, these samples of nanophotocatalysts were

stored in glass bottles and kept at a dry place for further use (Bo et al., 2007; Shao et al.,

2014).

The above same process was used for the synthesis of nanophotocatalysts (ZrO2)1-

x(ZnO)xFe2O3 by ultrasonic assisted mechanically stirred co-precipitation only the difference

was in arrangement of apparatus as given in section 3.3.

3.6 X-Ray Diffraction Analysis

XRD is an important technique which gives information about the crystalline

structure of solids i.e. lattice constants, geometry of crystals, unknown materials, defects and

stresses on crystalline structure (Azaroff, 1968; Cullity, 1956). Diffraction can occur in an

electromagnetic wave interact with one another having path difference of the order of wave

length. Visible light can be diffracted by grating which have dark lines a few thousand A○

apart of the order of wavelength of visible light. X-ray diffraction takes place at the crystal

two layers of which are separated by the order of wavelength of X-ray. X-rays have wave

length in A○ which is in the range of inter atomic layers in crystalline solids. It can be

diffracted from the atomic layers of atoms which is the characteristic property of crystalline

solid (Ohring, 1992). Bragg’s law states that constructive interference take place between

two waves reflected from successive lattice planes which are d distance apart of the order of

the integral multiple of x-ray wave length λ so that,

n λ = 2d sinθ

θ is an angle which x-ray make with the lattice plane and d is the distance between two

reflecting planes. (Birkholz, 2006). Diffraction lines broadens inversely to crystal size.

Crystal size can be calculated using Scherrer’s formula (Rahman et al., 2013).

Δ2θ = 0.9λ/L Cos θ

34

L is the size of crystal in A○ and Δ2θ is the FWHM of the diffraction line at θ (Daou et al.,

2009).

X-Ray diffraction analysis was performed to calculate the size of crystal and

determining the crystalline phase of photocatalysts, using Bruker’s D8 Advanced with Cu Kα

radiation (λ = 1.5418 A○) with a glass slide having cavity 10x10x1 mm3 as sample holder

(Ismail et al., 2014). Nanocomposite powder was fixed in sample holder and put in the

diffractometer which was controlled by a data scan software with the scan parameters, step

size = 0.05○, scan rate = 1.2○ per min. and 2 θ = 10-100○ (Bai et al., 2014)

3.7 Scanning Electron Microscopy (SEM)

Surface details of the material can be studied by SEM analysis. This analysis gives

information in between a high magnifying microscope and transmission electron microscope.

In this process an electron beam is generated by electron source gun and this beam of

electrons is scanned over the specimen. The image is formed by the secondary or back

scattered electrons through a detector. The secondary electron gives topographic information

of the target material. The back scattered electron produced the e- + h+ pair in semiconductor

detector and give information about the chemical composition of the sample (Zhou and

Wang, 2007; Alyamani and Lemine, 2012).

In this project SEM (Philips XL 30) with LaB6 electron source was used to study the

topography of nanocomposites (Wong et al., 2012; Habibi and Sheibani, 2013). The

powdered photocatalyst was mixed with C2H5OH and dispersed on silicon substrate. It was

dried at 60 ᴼC in an oven for 24 h and placed on a sample stub with the help of magnetic

tape. Sample was coated with 10 nm of platinum layer with help of sputter coater (Quorum

Q150T) (Dewan et al., 2012). Electron microscope was operated at accelerated voltage of 5-

20 Kv, working distance 8-15 mm and spot size 3-5.

3.8 Energy Dispersive X-ray Spectroscopy (EDX)

Energy dispersive X-ray spectroscopy is an elemental analysis technique.

Electromagnetic radiations and sample interact in this technique, charged particles hit the

target metal, X-rays are emitted which are used as analyzing radiations (Toyoda et al., 2004;

35

Corbari et al., 2008). Characterization ability of this method depends upon the fact that X-

rays emitted from each element are of characteristic nature of the element which is unique for

that element. A high energy beam of electrons is focused on the sample to be analyzed for the

emission characteristic X-rays of the atom. The incident beam ejects an electron of the inner

shell leaving there an electron hole which is filled by an electron of high energy shell. The

difference of these two shells is released in the form of characteristic X-rays of the element

which can be measured by an energy dispersive spectrometer peaks with appropriate energies

which provide information about the elemental composition of the sample. Peak height is

proportional to elemental concentration. Position and height of peak with appropriate energy

and net count rate of variables give the composition of the element (Goldstein et al., 2012).

In this project Energy Dispersive X-ray analysis was performed with Philips XL 30

equipped with EDX detector to get EDX spectra and elemental composition of the samples

(Sohrabi et al., 2014; Vanaja et al., 2014). Sample powder was dispersed on magnetic tape

fixed on sample holder. Sample was placed in electron microscope and EDX spectra was

produced from back scattered electron image.

3.9 Particles Size Analysis

Dynamic Light Scattering is used to measure particle and molecular size. The

principle of dynamic light scattering is that fine particles and molecules that are in constant

random thermal motion, called Brownian motion, diffuse at a speed related to their size,

smaller particles diffusing faster than larger particles. The speed of Brownian motion is also

determined by the temperature, therefore precision temperature control is essential for

accurate size measurement. To measure the diffusion speed, the speckle pattern produced by

illuminating the particles with a laser is observed. The scattering intensity at a specific angle

will fluctuate with time, and this is detected using a sensitive avalanche photodiode detector

(APD). The intensity changes are analyzed with a digital auto correlator which generates a

correlation function. This curve can be analyzed to give the size and the size distribution

(Pecora, 2013).

In this project particle size was measured using the dynamic light scattering (DLS)

method with Malvern Zetasizer (Nano ZS) (Omar et al., 2014). Sample was dispersed in

36

deionized water and placed in ultrasonic bath to make good suspension. This suspension was

taken in sample cell and analyzed.

3.10 Surface area Pore Size Analysis

Surface area and porosity are two important physical properties that impact the

quality and utility of solid phase chemicals. Gas Adsorption analysis is commonly used for

surface area and porosity measurements. This involves exposing solid materials to gases or

vapors at a variety of conditions which evaluate either the weight uptake or the sample

volume. Analysis of these data provides information regarding the physical characteristics of

the solid including porosity, total pore volume (TOPV), and pore size distribution. The

Brunauer, Emmett and Teller (BET) technique is the most common method for determining

the surface area of powders and porous materials. Nitrogen gas is generally employed as the

probe molecule and is exposed to a solid under investigation at liquid nitrogen conditions

(i.e. 77ᴼ K). The surface area of the solid is evaluated from the measured monolayer capacity

and knowledge of the cross-sectional area of the molecule being used as a probe (Sing, 2001;

Lowell et al., 2012).

The surface area and adsorption–desorption measurements were carried out on

a Micromeritics Tristar 3000 porosimeter at 77ᴼ K using liquid nitrogen. 0.2g of each sample

was taken in sample tubes and degassed at 150 °C for 12 h (Zhu et al., 2013). Loss of weight

was calculated by measuring the weight of empty tubes, weight of sample + tube before and

after degassing. Then theses sample tubes were fixed in Tristar 3000 calculations was made

by software automatically.

3.11 Photocatalytic activity

There are different terms used for photocatalytic reactions (Lu and Pichat, 2013)

(i) Photoxidation (taking place at hole h+)

(ii) Photoreduction (taking place at surface e─)

(iii) Photosensitization (when electron is absorbed by substrate molecule)

37

All photocatalysts should have filled valence band and empty conduction band. A photon

(hv) of light having equal or greater energy than band gap energy of photocatalyst excite

electron from valence band to conduction band a charge separation take place at the surface

of photocatalyst transferring an electron to conduction band and a positive charge hole (h+) at

valence band. When this electron/hole (e─/h+) recombine producing heat energy. This

situation is the failure of photocatalysis and takes place in nano seconds. A successful

photocatalyst should possess the following characteristics (Gaya, 2013).

i) Photocatalyst can reverse its oxidation state so that it can accommodate a hole

without decomposition i.e. semiconductor should have more than one stable

oxidation states.

ii) Photocatalyst should have suitable band gap energy equal to or less than visible

light photon’s energy.

iii) It should be non-photo-corrosive.

iv) It should be non-toxic.

v) It should be cheap and abundantly available.

Different methods have been employed for the testing of photocatalytic activity of

nanophotocatalyst e.g.

i) Decomposition of water for hydrogen production (Teets and Nocera, 2011;

Preethi and Kanmani, 2013).

ii) Degradation of organic waste for electricity production (Lianos, 2011).

iii) Decomposition of insecticides (Kitsiou et al., 2009).

iv) Decomposition of toxic gasses (Barea et al., 2014).

v) Degradation of organic pollutants like Phenols, dyes etc. (Zhang et al., 2014; Ma

et al., 2015).

As this work is for the treatment of synthetic textile waste water therefore three dyes have

been chosen to degrade

i) Methyl Orange

ii) C I Reactive Black 5

iii) Methylene Blue

I

C I Reactive Black 5

Methyl Orange

Methylene Blue

38

These dyes have been chosen due to the reason that the use of dyes in industry are at the top

as compare with other organic pollutants. The focal aim of this work is the testing of the dye

degradation ability of synthesized nanophotocatalysts under visible light irradiation

3.11.1 Photocatalytic activity test

Photocatalytic activity test was performed by the degradation of dyes. An aqueous

100ml solution of dye with different initial concentrations and initial pH of all three dyes was

used. It was taken in a 250 ml glass reactor. Photocatalyst with different doses was added to

the dye solution and stirred in dark for 30 min to develop adsorption desorption equilibrium

(Abdelaal and Mohamed, 2014). The reactor was exposed to visible light using 150 W

halogen lump (Ananpattarachai et al., 2009) with a constant stirring at 200 rpm with

mechanical stirrer in open atmosphere at room temperature. 3ml aliquots were taken from the

system after each 20 min interval (Gupta et al., 2015). These were centrifuged at 4000 rpm

for 10 min to separate catalyst particles and to obtain the clear solution (Ju et al., 2011). The

absorption values were taken to calculate degradation for each sample using Agilent Cary 60

UV-Vis spectrophotometer (Yang et al., 2013). Spectrophotometer was equipped with

software to record data. Base line correction was performed using deionized water.

Degradation percentage was calculated by using following formula (Gupta et al., 2015).

% Degradation = Co −Ct

Co × 100

Where Co absorbance at zero and Ct absorbance at time t.

3.11.2 Optimization of pH

The initial pH value of the reaction mixture affects the photocatalytic activity of the

photocatalyst low pH produces positive charge while high pH produces negative charge to

the surface of photocatalyst. Experiment 3.11.1 was repeated at pH 1,3,5,7 and 9 to optimize

the pH for the degradation of each dye (Siddique et al., 2011).

3.11.3 Optimization of photocatalyst dose

Degradation rate changes with the change of dose of the photocatalyst. At a certain

concentration maximum light can pass through reaction mixture and activate the

39

photocatalytic particles after that concentration photocatalytic particles itself start to hinder

the passage of light resulting in low degradation (Sapawe et al., 2013)b. Photocatalytic

experiment 3.11.1 was repeated at 20, 30, 40, 50, 60 and 70 mg/100ml for all the three dyes.

3.11.4 Optimization of dye concentration:

Initial concentration of the dye solution affects the photocatalytic efficiency of

photocatalyst. By increasing dye concentration more molecules are available for the

adsorption on surface of photocatalyst. But very higher concentration decreases the passage

of light through the dye solution due to dark color (Sobana et al., 2013). To optimize the

initial dye concentration in photocatalytic experiments 20, 30, 40, 50, 60 and 70 ppm solution

were used for each dye.

3.12 Reusability test

Catalyst lifetime is an important parameter of the photocatalytic process because its

use for a longer period of time leads to a significant cost reduction of the treatment (Subash

et al., 2013)a. Reusability test was performed to check the stability and photocatalytic

efficiency of used photocatalyst. In this experiment 100 ml of 50 ppm dye solution was taken

at optimized pH in reactor and 60 mg of photocatalyst was added to the solution and stirred

for 30 min in dark and then exposed to visible light for 140 min and centrifuged to separate

the catalyst. It was washed with deionized water, dried at 100ᴼC for 2 hours and used again in

next experiment. This experiment was repeated 6 times with both photocatalysts for all three

dyes (Jiang et al., 2014).

3.13 Evaluation of Quality Assurance Parameters

3.13.1 Chemical oxygen demand (COD)

Reagent preparations

Digestion solution

Digestion solution was prepared by adding 2.6g K2Cr2O7, 8.33g HgSO4 in 42ml

concentrated H2SO4 (98%) and then diluting it to 250ml with deionized water.

40

Catalyst solution

5.06 g Ag2SO4 was dissolve in 500 ml concentrated H2SO4 and placed it for 48 h to

ensure complete dissolution of Ag2SO4.

Standard Solution of Potassium hydrogen phthalate (KHP)

A standard solution of Potassium hydrogen phthalate was prepared by dissolving

425mg KHP in 1L of deionized water. 425 ppm solution of KHP gives 500 mg/L COD.

Procedure

For COD analysis according to standard methods 3.5 ml of catalyst solution was

added to1.5 ml of digestion solution in clean screw-cap vials and allowed to stand to ambient

temperature. Then 2.5 ml of sample solution was added and vials were incubated at 150°C

for 2 hours in a dry incubator. After allowing the vials to cool to room temperature COD

values were determined by measuring the absorbance of digested assay solution at λ=600nm

on UV-Visible recording spectrophotometer (Rice et al., 2012).

Calculations:

Standard factor =COD of standard KHP

absorbance of digested solution

COD of sample = standard factor × absorbance of digested solution

Percent decrease in chemical oxygen demand was calculated by using following formula.

Decrease in COD % = (COD)initial − (COD)final

(COD)final × 100

3.13.2 Total organic carbon (TOC)

Reagent preparations

2N potassium dichromate (K2Cr2O7) solution was prepared by dissolving 98.06 gram

per litter.

41

250 ppm solution of glucose was prepared by dilution method from a stock solution

of 1000ppm. 25ml of stock solution was taken and diluted to 100ml in volumetric

flask.

Analytical grade sulphuric acid (98%) was used.

Procedure

1.6ml of sulphuric acid was taken in clean screw-cap vials and then 1ml of 2N

potassium dichromate (K2Cr2O7) was added and mixed. Then 4ml of sample solution or

glucose solution was added and incubated at 110°C for 1.5 hours. After incubation

absorbance were taken at λ= 590nm using UV-Visible recording spectrophotometer. (Rice et

al., 2012)

Calculations

Standard factor = concentration of glucose (mg/L)/ absorbance after incubation

TOC of sample (mg/L) = standard factor × absorbance of sample after incubation.

Removal of TOC in percentage was calculated by using formula.

Removal TOC % = (TOC)initial − (TOC)final

(TOC)final × 100

3.12.2 Mineralization test

In this experiment 100 ml of 50 ppm dye solution was taken at optimized pH in

photocatalytic reactor and 60 mg of photocatalyst was added to the solution and stirred for 30

min in dark and then exposed to visible light for 140 min to test mineralization of the dye. 5

ml aliquots were taken from the system after each 20 min and TOC values were obtained

(Hernández-Uresti et al., 2013).

42

3.13.4 Total suspended solids (TSS)

Procedure:

a. Selection of filter paper and sample volume:

Sample volume should be selected to give yield between 2.5 and 200mg dried residues.

And if volume filtered fail to meet minimum yield, increase sample volume up to 1 L. If

complete filtration takes more than 10 minutes, increase filter pore diameter or decrease

sample volume.

b. Sample analysis:

Wattman # 42 filter paper was used for this analysis and volume chosen was 50ml.

First filter paper was made moisture free by placing it in electric oven at 105°C till constant

weight and then 50ml of sample was taken and allowed to filter. After the completion of

filtration, filter paper once again was dried in electric oven at 105°C for 1 hour or till

constant weight and then weighing of that filter paper containing residues was done. (Rice et

al., 2012)

Calculations:

Total suspended solids (mg

L) =

A − B

Sample volume used in ml× 1000

Where:

A = weight of filter paper + dried residue in mg

B = weight of filter paper in mg

3.12.5 Hemolytic Activity (Toxicity)

Hemolytic activity of the compound was studied by the method used by Powell and

coworkers (Powell et al., 2000). Three mL freshly obtained heparinized human blood was

collected from volunteers after consent and counseling. It was gently mixed, poured into a

sterile 15 mL falcon tube and centrifuged for 5 min at 1000 rpm. The supernatant was poured

off and viscous pellet washed three times with 5 mL of chilled (4oC) sterile isotonic

43

Phosphate-buffer saline (PBS) solution. The pH was adjusted at 7.4 and stabilized by mixing

for almost half an hour at room temperature. The washed cells were suspended in the 29 mL

chilled PBS solution. Erythrocytes were counted and found to be 7.068 X 108 cells per mL

for each assay. Then 20μL of solution of the compound was taken in six apendoff tubes, each

of 2mL size. 20μL Triton X-100 (0.1% v/v) was taken as positive control which caused

100% cell lysis and phosphate buffer saline (PBS) was taken as negative control which

caused 0% cell lysis. Then in each apendoff tube (containing 20 μL sample solution) 180 μL

diluted cell suspension was added and mixed well. Tubes were then incubated for 35 min at

37oC agitated for10 min immediately after incubation and the tubes were placed on ice for 5

min. Then tubes were centrifuged for 5 min at 1000 rpm. After centrifugation 100 μL of the

supernatant was taken from each tube and diluted with 900 μL chilled (4oC) PBS. Then all

the tubes were maintained on ice. Then 200 μL of each of the sample concentration was

added into 96 well micro plate. Positive control (100% lysis) and negative control (0% lysis)

were also taken on the same 96 well micro plate. After sampling the absorbance was noted at

576 nm on μQuant (Bioteck, USA). The % RBCs lysis for each concentration was calculated

by using following formula:

Hb Abs.

% Hemolysis = ————— × 100

Hb100% Abs.

Data observed was expressed Hb hemolysis of the sample and Hb100% of 100% hemolysis of

the blood.

3.13 Data analysis

All experiments were performed in triplicates and the experimental data was analyzed by

applying standard deviation.

44

CHAPTER 4

RESULTS AND DISCUSSIONS

4.1 X-Ray Diffraction Analysis

XRD is an important technique which gives information about the crystalline

structure of solids i.e. lattice constants, geometry of crystals, unknown materials, defects and

stresses on crystalline structure (Park et al., 2010). X-ray diffraction analysis was performed

to check the crystallinity of the samples calcined at different temperature and the first

selection of the photocatalyst was made on the basis of XRD results. Sample with calcination

at 600ᴼC were good crystalline in each mixture of metals oxides.

XRD patterns of the samples were analyzed with the help of Match! 3.0.0 (Phase

Identification software from Powder Diffraction) by Crystal Impact Bonn, Germany.

Database used for the analysis was Crystallography Open Database (COD) REV129424

2015.01.07.

4.1.1 X-Ray Diffraction Analysis of (Al2O3)1-x(ZnO)x(Fe2O3)

4.1.1.1 X-Ray Diffraction Analysis of Al2O3.Fe2O3 synthesized by mechanically stirred

co-precipitation

Al2O3.Fe2O3 synthesized by mechanically stirred co-precipitation was calcined at

400ᴼC and 600 ᴼC and the XRD patterns of un-calcined and calcined sample are given in Fig.

4.1. Un-calcined sample did not show any crystallinity as there is no peak. Sample calcined

at 400ᴼC has peaks for crystalline structures but these peaks are broad which show some

crystalline and some amorphous phase in the sample. But the sample calcined at 600ᴼC has

very sharp peaks which confirm its crystallinity. This sample has two type of crystal system.

Peaks at 2θ is equal to 32.95ᴼ, 35.57ᴼ, 40.94ᴼ, 49.28ᴼ, 62.56ᴼ and 63.87ᴼ are peaks for α-Fe2O3

(hematite) with rhombohedral crystal system according to entry number 96-900-9783.

Hercynite phase was also detected with peaks at 18.78ᴼ, 63.61ᴼ and small peaks at 72.06ᴼ and

45

75.06ᴼ which represents the reported formula AlFe2O4 with cubic crystal system according to

entry number 96-901-2447.

Fig. 4.1 XRD patterns of Al2O3.Fe2O3 synthesized by mechanically stirred co-

precipitation

Fig. 4.2 XRD patterns of Al2O3.Fe2O3 synthesized by ultra-sonic assisted mechanically


Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

46

4.1.1.2 XRD Analysis of Al2O3.Fe2O3 synthesized by ultra-sonic assisted mechanically

stirred co-precipitation.

XRD pattern of Al2O3.Fe2O3 synthesized by ultra-sonic assisted mechanically stirred and

calcined at 600ᴼC are shown in Fig. 4.2. Two types of crystal system were detected basic

sharp peaks at 2θ = 24.26ᴼ, 33.31ᴼ, 35.76ᴼ, 43.72ᴼ, 54.87ᴼ, 62.75ᴼ, 64.94ᴼ, 72.36ᴼ, 81.83ᴼ,

83.41ᴼ and 89.04ᴼ represents the α-Fe2O3 (Hematite) with trigonal crystal system according to

entry number 96-901-4881. Gahnite phase was also detected at 2θ = 39.41ᴼ, 49.71ᴼ, 56.31ᴼ,

69.93ᴼ, 75.44ᴼ and 94.29ᴼ which represents cubic crystal system according to the entry

number 96-900-7028.

4.1.1.3 X-Ray Diffraction Analysis of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by


XRD patterns of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by mechanically stirred co-

precipitation are shown in Fig. 4.3. Peaks at 2θ equal to 24.21ᴼ, 33.25ᴼ, 40.96ᴼ, 54.23ᴼ, 57.76ᴼ,

and 69.84ᴼ matching with α-Fe2O3 (hematite) with trigonal crystal system according to entry

number 96-901-4881. Two peaks at 49.60ᴼ and 83.28ᴼ confirm the gahnite phase Al2O4Zn

(entry number 96-900-7025) and a peak at 62.39ᴼ represents ZnO (Zincite) with hexagonal

crystal system according to entry number 96-901-1663. So the sample has more than 1 phase

and crystal systems.

4.1.1.4 X-Ray Diffraction Analysis of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-

sonic assisted mechanically stirred co-precipitation

XRD patterns of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic assisted

mechanically stirred co-precipitation are shown in Fig. 4.4. XRD Pattern for the sample

calcined at 600ᴼC showed the peaks at 2θ is equal to 24.21ᴼ, 33.25ᴼ, 40.96ᴼ, 54.23ᴼ, 57.76ᴼ,

and 69.84ᴼ matching with α-Fe2O3 (hematite) with trigonal crystal system according to entry

number 96-901-4881. It is the basic constituent of the (Al2O3)0.75(ZnO)0.25Fe2O3

photocatalyst. Peaks matching with the formula Al2Fe0.4O4Zn0.6 at 64.94ᴼ and 85.23ᴼ which

confirm the presence of gahnite phase in the sample (entry number 96-900-6314).Two more

peaks at 49.60ᴼ and 83.28ᴼ also confirm the gahnite phase matching with Al2O4Zn according

to entry number 96-900-7025.

47

Fig. 4.3 XRD patterns of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by mechanically stirred

co-precipitation

Fig. 4.4 XRD patterns of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic assisted


Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

48



XRD patterns of (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized by mechanically stirred co-

precipitation and calcined at 600ᴼC matched with three different phases Hematite, Hercynite

and Franklinite. α-Fe2O3 (hematite) with trigonal crystals belongs to the peaks at 24.16ᴼ,

33.20ᴼ, 39.75ᴼ, 40.82ᴼ, 64.03ᴼ, 75.65ᴼ and 85.93ᴼ according to the entry number 96-591-0083.

Cubic Fe2O4Zn (Franklinite) has peaks at 2θ is equal to 29.99ᴼ, 35.65ᴼ, 62.52ᴼ and 65.86ᴼ

(entry no. 96-900-6896). A small amount of cubic AlFe2O4 (hercynite) was detected with

peaks at 35.65ᴼ, 54.14ᴼ, 57.70ᴼ and 80.38ᴼ according to entry number 96-901-2447. Patterns

are shown in Fig. 4.5.


co-precipitation

Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

49



Un-calcined (Al2O3)0.50(ZnO)0.50Fe2O3 did not show any crystallinity and calcined at

400ᴼC showed some peaks appeared in both samples synthesized by mechanically stirred and

ultra-sonic assisted mechanically stirred co-precipitation. Only the sample calcined at 600ᴼC

has sharp peaks so phase analysis was performed for it. Patterns are shown in Fig. 4.6. Peaks

at 2θ = 33.21ᴼ, 37.01ᴼ, 49.47ᴼ, 62.46ᴼ, 72.06ᴼ, 75.51ᴼ, 80.86ᴼ, 83.08ᴼ, 88.56ᴼ and 93.84ᴼ are the

characteristics peaks for Al2O3 with orthorhombic crystal system according to entry number

96-100-0443. AlFe2O4 with Hercynite phase is also detected according to entry number 96-

901-2447 and peaks at 2θ equal to 30.55ᴼ, 35.64ᴼ, 54.17ᴼ, 57.69ᴼ, 72.06ᴼ, 75.51ᴼ, 83.08ᴼ and

88.56ᴼ. Peaks at 2θ = 33.21ᴼ, 35.64ᴼ, 40.93ᴼ, 49.47ᴼ, 85.10ᴼ and some common peaks with

other confirmed the presence of α-Fe2O3 (Hematite).



Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

50



X-Ray diffraction analysis of (Al2O3)0.25(ZnO)0.75Fe2O3 also showed the same

behavior for un-calcined and calcined at 400ᴼC. So phase analysis from XRD patterns of

(Al2O3)0.25(ZnO)0.75Fe2O3 calcined at 600ᴼC was done with Match! 3.0.0. XRD patterns are

shown in Fig. 4.7 and 4.8.

(Al2O3)0.25(ZnO)0.75Fe2O3 synthesized by mechanically stirred co-precipitation and

calcined at 600ᴼC showed about 62.6% franklinite phase as the peaks at 2θ = 30.08ᴼ, 62.66ᴼ,

71.42ᴼ and 7.43ᴼ matched with cubic Fe2O4Zn according to the entry 96-900-6896. AlFe2O4

(hercynite) with cubic crystal system was detected by matching with peaks at 30.70ᴼ, 54.32ᴼ,

57.60ᴼ, 63.95ᴼ, 75.43ᴼ and 88.30ᴼ (entry number 96-901-2447). Peaks at 3.70ᴼ, 35.41ᴼ and

80.65ᴼ matched with hexagonal ZnO (entry number 96-101-1260). Some specific peaks for

trigonal hematite were also observed at 24.05ᴼ, 33.36ᴼ, 41.07ᴼ, 49.07ᴼ, 84.96ᴼ and 95.59ᴼ

according to entry number 69-901-4881.


co-precipitation

Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

51



Another method used for the synthesis of (Al2O3)0.25(ZnO)0.75Fe2O3 was ultra-sonic

assisted mechanically stirred co-precipitation almost the same peaks with some additional

peaks were observed for this sample but there was a change in crystal system. XRD patterns

are shown in Fig. 4.8. It can be observed from peaks for rhombohedral hematite (α-Fe2O3) at

2θ = 24.16ᴼ, 33.16ᴼ, 40.86ᴼ, 49.47ᴼ, 75.51ᴼ, 83.08ᴼ and 88.62ᴼ according to entry number 96-

900-9783. Peaks matched with cubic franklinite (Fe2O4Zn) at 30.18ᴼ, 43.34ᴼ, 62.52ᴼ, 74.66ᴼ,

78.90ᴼ and 89.53ᴼ (entry number 96-9006-895). Some common peaks for hexagonal ZnO

were observed at 54.11ᴼ, 64.02ᴼ, 72.11ᴼ and 80.73ᴼ (entry number 96-101-1260).



4.1.1.9 X-Ray Diffraction Analysis of ZnO.Fe2O3 synthesized by mechanically stirred

co-precipitation

Phase identification for ZnO.Fe2O3 synthesized by mechanically stirred co-

precipitation calcined at 600ᴼC was done and two types of phases hematite (α-Fe2O3) and

Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

52

franklinite (Fe2O4Zn) were detected. Hematite with rohmbohedral crystal system was

identified at 2θ is equal to 24.09ᴼ, 33.09ᴼ, 49.40ᴼ, 54.04ᴼ, 57.56ᴼ, 62.39ᴼ, 63.95ᴼ, 69.50ᴼ,

71.91ᴼ, 75.37ᴼ, 77.65ᴼ, 80.59ᴼ,8.89ᴼ and 88.48ᴼ according to entry number 96-101-1241.

Franklinite with cubic crystals was identified at 2θ = 18.15ᴼ, 29.90ᴼ, 35.62ᴼ, 42.82ᴼ, 53.12ᴼ,

56.58ᴼ, 62.15ᴼ, 70.54ᴼ, 73.48ᴼ, 88.94ᴼ and 93.64ᴼ according to entry number 96-900-5108.

XRD patterns are shown in Fig. 4.9.

Fig. 4.9 XRD patterns of ZnO.Fe2O3 synthesized by mechanically stirred co-

precipitation

4.1.1.10 X-Ray Diffraction Analysis of ZnO.Fe2O3 synthesized by ultra-sonic assisted


XRD patterns of ZnO.Fe2O3 synthesized by ultra-sonic assisted co-precipitation and

calcined at 600ᴼC is shown in Fig. 4.10. It has matched with three phases rhombohedral

hematite (α-Fe2O3), cubic franklinite (Fe2O4Zn) and small amount of hexagonal zincite

(ZnO). Characteristic peaks for hematite are at 2θ = 24.33ᴼ, 33.14ᴼ, 41.04ᴼ, 49.65, ᴼ 54.28ᴼ,

57.74ᴼ, 69.81ᴼ, and all the peaks from 75.62ᴼ to 93.88ᴼ (entry number 96-900-9783). Peaks

identified for franklinite are at 2θ = 18.33, ᴼ 30.14ᴼ, 35.50ᴼ, 43.06ᴼ, 56.89ᴼ and 62.75ᴼ (entry

Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

53

number 96-900-6896). Zincite has peaks at 35.25ᴼ, 62.34ᴼ, 64.20ᴼ and 72.09ᴼ(entry No. 96-

101-1260).

Fig. 4.10 XRD patterns of ZnO.Fe2O3 synthesized by ultra-sonic assisted mechanically


4.1.2 X-Ray Diffraction Analysis of (ZrO2)1-x(ZnO)x(Fe2O3)

4.1.2.1 X-Ray Diffraction Analysis of ZrO2.Fe2O3 synthesized by mechanically stirred

co-precipitation

ZrO2.Fe2O3 synthesiszed by mechanically co-precipitation with calcination

temperature 600ᴼC was analyzed for phase identification. ZrO2 with cubic crystal system and

α-Fe2O3 with trigonal crystal system were detected. Peaks at 2 = 24.12ᴼ, 33.12ᴼ, 40.81ᴼ,

49.41ᴼ, 53.98ᴼ and 62.33ᴼ represent α-Fe2O3 according to entry number 96-900-0140 and

peaks at 30.43ᴼ, 50.90ᴼ, 60.54ᴼ and 63.90ᴼ are the characteristics peaks for ZrO2 according to

entry number 96-900-9052. XRD patterns are shown in Fig. 4.11.

Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

54

Fig. 4.11 XRD patterns of ZrO2.Fe2O3 synthesized by mechanically stirred co-

precipitation

4.1.2.2 X-Ray Diffraction Analysis of ZrO2 .Fe2O3 synthesized by ultra-sonic assisted


ZrO2.Fe2O3 synthesized by ultra-sonic assisted mechanically stirred co-precipitation

and calcined at 600ᴼC showed sharp peaks. Baddeleyite (ZrO2) with monoclinic crystal

system and trigonal hematite (α-Fe2O3) was detected. Baddeleyite has characteristic peaks at

2θ is equal 33.43ᴼ, 36.04ᴼ, 72.89ᴼ, 76.29ᴼ and 89.45ᴼ according to entry number 96-900-7449

and hematite detected at 24.49ᴼ, 33.43ᴼ, 49.80ᴼ, 58.35ᴼ, 72.89ᴼ, 62.59ᴼ and 89.28ᴼ according

to entry number 96-901-6458. Patterns are shown in Fig. 4.12.

4.1.2.3 X-Ray Diffraction Analysis of (ZrO2)0.75(ZnO)0.25 Fe2O3 synthesized by


XRD patterns of (ZrO2)0.75(ZnO)0.25Fe2O3 synthesized by mechanically stirred co-

precipitation technique are shown in Fig.4.13. Sample calcined at 600ᴼC has two broad peaks

from 27ᴼ to 36ᴼ and 60ᴼ to 63ᴼ. Peaks detected under this rang of 2θ are 30.78ᴼ, 34.36ᴼ, 62.02ᴼ

for hexagonal ZnO, 28.25ᴼ, 32.01ᴼ, 36.22ᴼ, 61.49ᴼ and 62.47ᴼ for monoclinic ZrO2, 35.99,

Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

55

60.54 for cubic wuestite (FeO) and 31.00ᴼ, 60.54ᴼ for cubic franklinite according to entry

number 96-101-1260, 96-230-0204, 96-900-8637 and 96-900-6908 respectively.

Fig. 4.12 XRD patterns of ZrO2.Fe2O3 synthesized by ultra-sonic assisted mechanically


Fig. 4.13 XRD patterns of (ZrO2)0.75(ZnO)0.25 Fe2O3 synthesized by mechanically stirred

co-precipitation

Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

56

4.1.2.4 X-Ray Diffraction Analysis of (ZrO2)0.75(ZnO)0.25 Fe2O3 synthesized by ultra-


Baddeleyite ZrO2 with orthorhombic crystals, cubic Franklinite Fe2O4Zn, ZnO with

hexagonal crystal system and trigonal hematite (α-Fe2O3) were the detected phases in

(ZrO2)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic assisted mechanically stirred co-

precipitation technique. XRD pattern has no very sharp peaks but the specific and some

common peaks which can be observed at 2θ are 30.46ᴼ, 35.62ᴼ, 51.08ᴼ, 60.08ᴼ and 35.92ᴼ for

ZrO2, 30.46ᴼ, 63.61ᴼ and 35.92ᴼ for Fe2O4Zn, 56.64ᴼ, 62.89ᴼ for ZnO and 35.62ᴼ, 56.30ᴼ,

62.56ᴼ for Fe2O3 according to entry number 96-9005836, 96-900-6901, 96-230-0113 and 96-

901-5066 respectively. XRD patterns are shown in Fig. 4.14.

Fig. 4.14 XRD patterns of (ZrO2)0.75(ZnO)0.25 Fe2O3 synthesized by ultra-sonic assisted




XRD patterns of (ZrO2)0.50(ZnO)0.50Fe2O3 synthesized by mechanically stirred co-

precipitation are shown in Fig. 4.15. Sample calcined at 600ᴼC has peaks for following

phases. a) Cubic franklinite (Fe2O4Zn) at 2θ = 18.25ᴼ, 30.02ᴼ, 42.88ᴼ and 62.42ᴼ (Entry No.

Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

57

96-900-6895). b) Cubic maghemite (Fe2O3) at 2θ = 18.25ᴼ, 30.02ᴼ, 35.75ᴼ and 62.83ᴼ (Entry

no. 96-9006317). c) monoclinic baddeleyite (ZrO2) at 35.75ᴼ, 50.71ᴼ, 59.65ᴼ and 62.45ᴼ

according to entry number 96-900-7449.

Fig. 4.15 XRD patterns of (ZrO2)0.50(ZnO)0.50 Fe2O3 synthesized by mechanically stirred

co-precipitation



Phases detected in XRD patterns (ZrO2)0.50(ZnO)0.50Fe2O3 synthesized by ultra-sonic

assisted mechanically stirred co-precipitation and calcined at 600ᴼC are. a) Cubic franklinite

(Fe2O4Zn) at 2θ = 18.25ᴼ, 30.02ᴼ, 42.88ᴼ and 62.42ᴼ (Entry No. 96-900-6895). b) Cubic

maghemite (Fe2O3) at 2θ = 24.02ᴼ, 32.25ᴼ, 40.71ᴼ, and 49.25ᴼ (Entry no. 96-901-2693). c)

Cubic ZrO2 at 2θ = 30.54ᴼ, 35.34ᴼ and 63.66ᴼ (Entry No. 96-900-9052). d) Hexagonal ZnO at

2θ = 32.01ᴼ and 63.66ᴼ according to entry number 96-230-0114. Patterns are shown in Fig.

4.16.

Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

58

Fig. 4.16 XRD patterns of (ZrO2)0.50(ZnO)0.50 Fe2O3 synthesized by ultra-sonic assisted




XRD pattern of (ZrO2)0.25(ZnO)0.75 Fe2O3 synthesized by mechanically stirred co-

precipitation are shown in Fig. 4.17. Sample calcined at 600ᴼC showed four broad peaks

ranging at 2θ = 25ᴼ to 37ᴼ, 47ᴼ to 50ᴼ, 54ᴼ to 60ᴼ and 61ᴼ to 65ᴼ. Maghemite (tetragonal Fe2O3)

was detected at 2θ is equal to 26.14ᴼ, 34.02ᴼ, 55.07ᴼ and 63.07ᴼ (Entry No. 96-901-2693).

Zincite (hexagonal ZnO) was detected at 34.31ᴼ, 35.42ᴼ, 61.95ᴼ and 64.08ᴼ (Entry No. 96-

101-1260). Monoclinic ZrO2 was detected at 35.21ᴼ, 55.25ᴼ, 55.56ᴼ, 55.81ᴼ and 62.85ᴼ (Entry

No. 96-230-0297).



Franklinite, baddeleyite and hematite were detected in XRD patterns of

(ZrO2)0.25(ZnO)0.75Fe2O3 synthesized by ultra-sonic assisted mechanically stirred co-

precipitation technique which are shown in Fig. 4.18. (ZrO2)0.25(ZnO)0.75Fe2O3 calcined at

600ᴼC has identified peaks at 2θ = 18.30ᴼ, 29.98ᴼ, 53.27ᴼ, 56.73ᴼ, 62.27ᴼ, 73.69 and 89.15 are

the characteristics peaks for franklinite (Fe2O4Zn) with cubic crystals (Entry No. 96-900-

Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

59

6895). Orthorhombic baddeleyite (ZrO2) was detected at 2θ = 35.57ᴼ, 43.00ᴼ and 86.41ᴼ

(Entry No. 6-900-5836). Trigonal hematite (Fe2O3) identified with the characteristic peaks at

2θ is equal to 24.10ᴼ, 33.24ᴼ, and 35.57ᴼ according to entry number 96-901-4881.

Fig. 4.17 XRD patterns of (ZrO2)0.25(ZnO)0.75Fe2O3 synthesized by mechanically stirred

co-precipitation

Fig. 4.18 XRD patterns of (ZrO2)0.25(ZnO)0.75Fe2O3 synthesized by ultra-sonic assisted


Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

Calcined at 400ᴼC

Calcined at 600ᴼC

Uncalcined

60

4.1.2.9 X-Ray Diffraction Analysis of ZnO.Fe2O3 synthesized by mechanically stirred

and ultra-sonic assisted mechanically stirred co-precipitation

XRD analysis of ZnO.Fe2O3 synthesized by mechanically stirred is given in section

4.1.1.9 and XRD analysis of ZnO.Fe2O3 synthesized by ultra-sonic assisted mechanically

stirred is given in section 4.1.1.10

4.2 Scanning Electron Microscopy

4.2.1 Scanning Electron Microscopy of (Al2O3)1-x(ZnO)xFe2O3

Scanning Electron Microscopy (SEM) was done for the samples with best

photocatalytic activity from (Al2O3)1-x(ZnO)xFe2O3 synthesized by both simple stirred and

ultra-sonic assisted stirred co-precipitation. The samples synthesized by ultra-sonic assisted

mechanically stirred co-precipitation showed good photocatalytic efficiency. All three dyes

have maximum photocatalytic degradation with these samples. SEM images of the samples

synthesized by ultra-sonic assisted mechanically stirred co-precipitation are shown in Fig

4.19 to 4.23 for Al2O3.Fe2O3, (Al2O3)0.75(ZnO)0.25Fe2O3, (Al2O3)0.50(ZnO)0.50 Fe2O3,

(Al2O3)0.25(ZnO)0.75Fe2O3 and ZnO.Fe2O3 (Calcined at 600ᴼC) respectively it is clear from

the images that all the photocatalysts have no specific shape. But the SEM image of

(Al2O3)0.75(ZnO)0.25Fe2O3 has round shape particles with large surface area that is why it was

most active sample for photocatalysis and it degraded all three dyes above 80 percent.

ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ ᶥ1 µm

Fig. 4.19 SEM image of Al2O3.Fe2O3 synthesized by ultra-sonic assisted mechanically

stirred co-precipitation and calcined at 600ᴼC

61

Fig. 4.20 SEM Image of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic assisted




62



Fig. 4.23 SEM Image of ZnO.Fe2O3 synthesized by ultra-sonic assisted mechanically


4.2.2 Scanning Electron Microscopy for (ZrO2)1-x(ZnO)xFe2O3

Samples with high photocatalytic efficiency were analyzed by Scanning Electron

Microscopic analysis for (ZrO2)1-x(ZnO)xFe2O3.The samples synthesized by ultra-sonic

63

assisted mechanically stirred co-precipitation calcined at 600ᴼC have higher photocatalytic

activity than the samples synthesized by simple mechanically stirred. SEM results are shown

in Fig 4.24 to 4.27 for ZrO2.Fe2O3, (ZrO2)0.75(ZnO)0.25Fe2O3, (ZrO2)0.5(ZnO)0.5Fe2O3 and

(ZrO2)0.25(ZnO)0.75Fe2O3 respectively. ZnO.Fe2O3 is shown in Fig. 4.23. There was no

specific shape observed in all samples.

Fig. 4.24 SEM Image of ZrO2.Fe2O3 synthesized by ultra-sonic assisted mechanically


Fig. 4.25 SEM Image of (ZrO2)0.75(ZnO)0.75Fe2O3 synthesized by ultra-sonic assisted


64





65

4.3 Energy Dispersive X-Ray (EDX) Analysis

4.3.1 Energy Dispersive X-Ray (EDX) Analysis of (Al2O3)1-x(ZnO)xFe2O3

EDX analysis was done for for (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-sonic

assisted stirred during co-precipitation. The samples synthesized by ultra-sonic assisted co-

precipitation have best results for the removal of dyes from waste water. . Homogeneity of

the material can be observed form back scatter electron images all samples are homogeneous

but Al2O3.Fe2O3 is non-homogeneous material as its surface has different shades and it looks

like a pours material at the same time it is least efficient for photocatalysis.

4.3.1.1 Energy Dispersive X-Ray Analysis of Al2O3 .Fe2O3

EDX analysis of Al2O3.Fe2O3 was performed with help of Philips XL 30 equipped

with EDX detector and back scatter electron images of the samples were taken to analyze the

chemical composition of the samples for qualitative and some estimation of molar and

weight percentage of elements present in sample. It is clear from the SEM image shown in

Fig. 4.28 that the sample was non-homogeneous metals oxide. The area underlined in Fig.

4.28 was pointed out for EDX spectra which are shown in Fig. 4.29. Spectra have very clear

peaks for Fe, Al and O a small peak of C also observed which is due the magnetic tape used

for the support of sample on stub this peak was eliminated for the weight and molar percent

analysis. Estimated weight and molar percent for Fe, Al and O from the EDX spectra is

shown in Table 4.1.

Fig. 4.28 SEM (back scatter) image for EDX spectra of Al2O3.Fe2O3 synthesized by

ultra-sonic assisted mechanically stirred co-precipitation and calcined at 600ᴼC

66

Fig. 4.29 EDX spectra of Al2O3.Fe2O3 synthesized by ultra-sonic assisted mechanically


Table No. 4.1 Estimated weight and molar percent of Al2O3.Fe2O3 synthesized by ultra-

sonic assisted mechanically stirred co-precipitation and calcined at 600ᴼC from EDX

spectra

Component Wt % Mol %

Al2O3 22.74 31.55

Fe2O3 77.26 68.45

Total 100.00 100.00

4.3.1.2 Energy Dispersive X-Ray Analysis of (Al2O3)0.75(ZnO)0.25Fe2O3

Sample with formula (Al2O3)0.75(ZnO)0.25Fe2O3 was analyzed with EDX and back

scatter electron image of the sample was taken to analyze the surface and chemical

composition of the sample for qualitative and quantitative analysis. Fig. 4.30 shows that the

sample was homogeneous metals oxide. EDX spectra shown in Fig. 4.31 have very clear

peaks for Fe, Al, Zn and O. Estimated weight and molar percent was performed from the

EDX spectra which is shown in Table 4.2 which confirm the percent composition used for

the synthesis of photocatalyst.

67

Fig. 4.30 SEM (back scatter) image for EDX spectra of (Al2O3)0.75(ZnO)0.25Fe2O3

synthesized by ultra-sonic assisted mechanically stirred co-precipitation and calcined at

600ᴼC

Fig. 4.31 EDX spectra of (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic assisted


68

Table No. 4.2 Estimated weight and molar percent of (Al2O3)0.75(ZnO)0.25Fe2O3 from

EDX spectra. Synthesized by ultra-sonic assisted mechanically stirred co-precipitation

and Calcined at 600ᴼC from EDX spectra.


Al2O3 14.24 19.49

Fe2O3 79.20 69.25

ZnO 6.56 11.26

Total 100.00 100.00

4.3.1.3 Energy Dispersive X-Ray Analysis of (Al2O3)0.50(ZnO)0.50Fe2O3

It is clear from back scatter electron SEM image (Fig. 4.32) that sample was

homogeneous metals oxide. EDX spectra shown in Fig. 4.33 have very clear peaks for Fe,

Al, Zn and O a small peak of C was also observed which is due the magnetic tape used for

the support of sample on stub. All other elements were eliminated from Peak list to estimate

the weight and molar percent from the EDX spectra which is shown in table 4.3.

Fig. 4.32 SEM (back scatter) image for EDX spectra of (Al2O3)0.50(ZnO)0.50Fe2O3


600ᴼC

69

Fig. 4.33 EDX spectra of (Al2O3)0.50(ZnO)0.50Fe2O3 synthesized by ultra-sonic assisted


Table No. 4.3 Estimated weight and molar percent of (Al2O3)0.50(ZnO)0.50Fe2O3


600ᴼC from EDX spectra


Al2O3 17.34 22.98

Fe2O3 74.01 62.64

ZnO 8.65 14.38

Total 100.00 100.00

4.3.1.4 Energy Dispersive X-Ray Analysis of (Al2O3)0.25(ZnO)0.75 Fe2O3

EDX analysis of homogeneous metals oxide (Al2O3)0.25(ZnO)0.75 Fe2O3 from SEM

back scatter electron image is shown in Fig. 4.34 and EDX spectra in Fig. 4.35. Peaks for Fe,

Al and O are very clear in Fig. 4.24 some other peaks of C and Si due to support used for the

sample. Weight and molar percent estimated from EDX spectra are shown in table 4.4.

70

Fig. 4.34 SEM (back scatter) image for EDX spectra of (Al2O3)0.25(ZnO)0.75 Fe2O3


600ᴼC

Fig. 4.35 EDX spectra of (Al2O3)0.25(ZnO)0.75 Fe2O3 synthesized by ultra-sonic assisted


Table No. 4.4 Estimated weight and molar percent of (Al2O3)0.25(ZnO)0.75 Fe2O3




Al2O3 5.91 8.14

Fe2O3 83.24 73.16

ZnO 10.84 18.70

Total 100.00 100.00

71

4.3.1.5 Energy Dispersive X-Ray Analysis of ZnO.Fe2O3

Sample with formula ZnO.Fe2O3 was analyzed energy dispersive X-rays with help of

Philips XL 30. Image produced by back scatter electrons is given in Fig. 4.36 and EDX

spectra shown in Fig. 4.37. Clear peaks were observed for Fe, Zn and O a small peak of Si

also observed which is due the silicon wafers used for the support of sample on stub.

Estimated weight and molar percent was performed from the EDX spectrum which is shown

in Table 4.5 in this estimation Si peak was eliminated from the observed peaks. Estimated

quantities are near to the percent composition used for the synthesis of photocatalyst.

Fig. 4.36 SEM (back scatter) image for EDX spectra of ZnO.Fe2O3 synthesized by ultra-

sonic assisted mechanically stirred co-precipitation and calcined at 600ᴼC

Fig. 4.37 EDX spectra of ZnO.Fe2O3 synthesized by ultra-sonic assisted mechanically


72

Table No. 4.5 Estimated weight and molar percent of ZnO.Fe2O3 synthesized by ultra-


spectra


Fe2O3 87.62 78.29

ZnO 12.38 21.71

Total 100.00 100.00

4.3.2. Energy Dispersive X-Ray (EDX) Analysis of (ZrO2)1-x(ZnO)xFe2O3

4.3.2.1 Energy Dispersive X-Ray Analysis of ZrO2.Fe2O3

Back scatter electron image of the sample was taken to analyze the surface of the

photocatalyst and its chemical composition. Results are shown in Fig. 4.76. SEM image

showed that the sample was homogeneous mixture of metals oxide. An EDX spectrum of the

sample is shown in Fig. 4.77. Peaks for Fe, Zr and O are very clear and peaks for C and Al

also observed which is due the magnetic tape used for the support of sample on aluminum

stub these peaks were not included in elemental estimation. Estimated weight and molar

percent of Zr and Fe oxides are shown in Table 4.45

Fig. 4.38 SEM (back scatter) image for EDX spectra of ZrO2.Fe2O3 synthesized by

ultra-sonic assisted mechanically stirred co-precipitation and calcined at 600ᴼC

73

Fig. 4.39 EDX spectra of ZrO2.Fe2O3 synthesized by ultra-sonic assisted mechanically


Table No. 4.6 Estimated weight and molar percent of ZrO2.Fe2O3 synthesized by ultra-


spectra


Fe2O3 56.26 49.81

ZrO2 43.74 50.19

Total 100.00 100.00

4.3.2.2 Energy Dispersive X-Ray Analysis of (ZrO2)0.75(ZnO)0.25 Fe2O3

(ZrO2)0.75(ZnO)0.25Fe2O3 was analyzed for the surface and chemical composition of

the sample. It is clear from the Fig. 4.40 the sample was homogeneous metals oxide the area

underlined was used for EDX spectra which shown in Fig. 4.41. Spectra have very clear

peaks for Fe, Zr, Zn and O a small peak for Al also observed which is due the Al support

used for sample. Estimated weight and molar percent was performed from the EDX spectra

74

which is shown in Table 4.46 which is almost same to the percent composition used for the

synthesis of photocatalyst.

Fig. 4.40 SEM (back scatter) image for EDX spectra of (ZrO2)0.75(ZnO)0.25Fe2O3


600ᴼC

Fig. 4.41 EDX spectra of (ZrO2)0.75(ZnO)0.25Fe2O3 synthesized by ultra-sonic assisted


75

Table No. 4.7 Estimated weight and molar percent of (ZrO2)0.75(ZnO)0.25Fe2O3




Fe2O3 65.76 57.81

ZrO2 28.83 32.85

ZnO 5.41 9.34

Total 100.00 100.00

4.3.2.3 Energy Dispersive X-Ray Analysis of (ZrO2)0.50(ZnO)0.50Fe2O3

EDX analysis of (ZrO2)0.50(ZnO)0.50Fe2O3 was performed for qualitative and

estimation of quantitative analysis. It is clear from the Fig. 4.42 the sample was

homogeneous metals oxide the area underlined was used for EDX spectra shown in Fig. 4.43.

Spectra have very clear peaks for Fe, Zr, Zn and O a small peak of Al also observed which is

due the Al support of sample stub. Estimated elemental weight and molar percent is shown in

Table 4.8 which is almost same as the composition used for the synthesis of photocatalyst.



600ᴼC.

76







Fe2O3 65.76 57.81

ZrO2 28.83 32.85

ZnO 5.41 9.34

Total 100.00 100.00

4.3.2.4 Energy Dispersive X-Ray Analysis of (ZrO2)0.25(ZnO)0.75 Fe2O3

EDX analysis of (ZrO2)0.25(ZnO)0.75 Fe2O3 was performed from the back scatter

electron image of the sample to analyze the surface and chemical composition of the sample.

Fig. 4.44 showed the homogeneous mixture of metals oxides. EDX spectra are shown in Fig.

4.45. The spectrum has very clear peaks for Fe, Zr and O peaks of C, Al and Si also observed

which is due the magnetic tape used for the support of sample on Al stub and silicon support.

Estimated weight and molar percent was performed from the EDX spectra which is shown in

Table 4.9.

77



600ᴼC







Fe2O3 76.71 66.90

ZrO2 11.62 13.13

ZnO 11.67 19.97

Total 100.00 100.00

78

4.4 Particle Size, Surface area and porosity analysis

4.4.1 Particle Size analysis of (Al2O3)1─x(ZnO)xFe2O3

Particle size was analyzed by Malvern Zetasizer (Nano ZS). Average particle

sizes are given in table No. 4.10 and 4.11 for (Al2O3)1-x(ZnO)xFe2O3 synthesized by co-

precipitation by mechanically stirred co-precipitation and (Al2O3)1-x(ZnO)xFe2O3 synthesized

by co-precipitation by ultra-sonic assisted mechanically stirred co-precipitation with different

values of x. It was observed from SEM images that particles were not of a specific shape so

the Zetasizer calculates the diameter of particles from different directions and give average

particle size as distribution of particle size by intensity. Particle sizes were also calculated

from X-Ray diffraction patterns by using Scherer’s formula. Both results have values close to

each other whith the confirmation of actual particle sizes. Effect of ultra-sonic assisted

stirring during the co-precipitation is the decrease in particle sizes. Photocatalytic activity

was improved due to small particle size and large surface area.

Table No. 4.10 particle sizes of (Al2O3)1-x(ZnO)xFe2O3 synthesized with mechanically


X


Average particle

Size with Zetasizer

(nm)

Particle size Calculated by

Scherer’s formula from XRD

(nm)

0 Al2O3.Fe2O3 28.21 27.91

0.25 (Al2O3)0.75(ZnO)0.25Fe2O3 53.15 52.40

0.50 (Al2O3)0.5(ZnO)0.5Fe2O3 39.56 38.33

0.75 (Al2O3)0.25(ZnO)0.75Fe2O3 53.64 53.01

1 ZnO.Fe2O3 29.22 28.31

79

Table No. 4.11 particle sizes of (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-sonic assisted

mechanically stirred co-precipitation technique at different values of x

X


Average particle

Size with Zetasizer

(nm)


Sherer’s formula from XRD

(nm)

0 Al2O3.Fe2O3 12.51 11.09

0.25 (Al2O3)0.75(ZnO)0.25Fe2O3 28.29 23.06

0.50 (Al2O3)0.5(ZnO)0.5Fe2O3 25.21 24.95

0.75 (Al2O3)0.25(ZnO)0.75Fe2O3 36.11 35.37

1 ZnO.Fe2O3 22.15 21.35

Fig. 4.46 Particle size distribution by intensity for Al2O3.Fe2O3 synthesized by


0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

Inte

nsity (

%)

Size (d.nm)

80

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

Inte

nsity (

%)

Size (d.nm)

Fig. 4.47 Particle size distribution by intensity for (Al2O3)0.75(ZnO)0.25Fe2O3 synthesized

by mechanically stirred co-precipitation

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

Inte

nsity (

%)

Size (d.nm)



81

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

Inte

nsity (

%)

Size (d.nm)



0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

Inte

nsity (

%)

Size (d.nm)

Fig. 4.50 Particle size distribution by intensity for ZnO.Fe2O3 synthesized by


82

0 5 10 15 20 25 30 35 400

1

2

3

4

5

6

7

8

Inte

nsity (

%)

Size (d.nm)

Fig. 4.51 Particle size distribution by intensity for Al2O3.Fe2O3 synthesized by ultra-


0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

Inte

nsity (

%)

Size (d.nm)



83

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

Inte

nsity (

%)

Size (d.nm)



0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

Inte

nsity (

%)

Size (d.nm)



84

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

Inte

nsity (

%)

Size (d.nm)

Fig. 4.55 Particle size distribution by intensity for ZnO.Fe2O3 synthesized by ultra-sonic


4.4.2 Particle Size analysis of (ZrO2)1-x(ZnO)xFe2O3

(ZrO2)1-x(ZnO)xFe2O3 synthesized by co-precipitation via mechanical stirring and

ultra-sonic assisted mechanical stirring was analyzed by Zetasizer for the particle size

measurements. Particle sizes were also calculated by Scherer’s formula using XRD patterns.

Results are given in table No. 4.12 and 4.13 with different values of x. SEM images showed

that there was no specific shape of particles. XRD results confirmed more than one crystal

system in samples so the calculations made by Zetasizer are the average particle sizes of the

samples. Particle size distribution by intensity for the samples synthesized by both methods

are given in Fig. 4.56 to 4.63. Particle sizes calculated from both methods have near values

which confirm the actual sizes. Particle sizes were decreased by ultra-sonic assisted

mechanically stirred co-precipitation which showed large surface area and improvement in

photocatalytic activity.

85

Table No. 4.12 particle sizes of (ZrO2)1-x(ZnO)xFe2O3 synthesized with mechanically


X


Average particle

Size with Zetasizer

(nm)



(nm)

0 ZrO2.Fe2O3 23.52 22.41

0.25 (ZrO2)0.75(ZnO)0.25Fe2O3 54.15 53.79

0.50 (ZrO2)0.5(ZnO)0.5Fe2O3 49.83 33.93

0.75 (ZrO2)0.25(ZnO)0.75Fe2O3 54.92 54.16

1 ZnO.Fe2O3 29.22 28.31

Table No. 4.13 Particle sizes of (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic assisted

mechanically stirred co-precipitation technique at different values of x

X


Average particle

Size with Zetasizer

(nm)



(nm)

0 ZrO2.Fe2O3 13.89 12.96

0.25 (ZrO2)0.75(ZnO)0.25Fe2O3 19.15 18.07

0.50 (ZrO2)0.5(ZnO)0.5Fe2O3 26.21 25.83

0.75 (ZrO2)0.25(ZnO)0.75Fe2O3 24.15 23.25

1 ZnO.Fe2O3 22.15 21.35

86

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

Inte

nsity (

%)

Size (d.nm)

Fig. 4.56 Particle size distribution by intensity for ZrO2.Fe2O3 synthesized by


0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

35

Inte

nsity (

%)

Size (d.nm)

Fig. 4.57 Particle size distribution by intensity for (ZrO2)0.75(ZnO)0.25Fe2O3 synthesized


87

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

Inte

nsity (

%)

Size (d.nm)



0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

Inte

nsity (

%)

Size (d.nm)



88

0 5 10 15 20 25 30 35 400

1

2

3

4

5

6

7

8

Inte

nsity (

%)

Size (d.nm)

Fig. 4.60 Particle size distribution by intensity for ZrO2.Fe2O3 synthesized by ultra-


0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

Inte

nsity (

%)

Size (d.nm)



89

0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

30

Inte

nsity (

%)

Size (d.nm)



0 10 20 30 40 50 60 70 80 90 1000

5

10

15

20

25

Inte

nsity (

%)

Size (d.nm)



90

4.4.3 Surface area and porosity analysis of (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3

Surface area and porosity analysis was performed by nitrogen adsorption-desorption

using Tristar 3000. Single point, Brunauer-Emmett-Teller (BET) and Langmuir surface area,

BET adsorption, Barret-Joyner-Halenda (BJH) adsorption and desorption pore diameter was

calculated for most active sample which were (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3.

Results are shown in table 4.12.1 & 4.13.1. It is clear from the results that ultra-sonic assisted

stirred co-precipitation improved the surface area and particle size. Pore diameter was

decreased in case of BET and BJH adsorption but BJH desorption diameter was almost same

for both samples. Increase in surface area enhanced the adsorption capacity and

photocatalytic activity of photocatalyst because adsorption processes are depends on the

surface reactions with materials (Hassan et al., 2014).

Table No. 4.12.1 Surface area and porosity analysis of (Al2O3)0.75(ZnO)0.25Fe2O3

Surface area and porosity (Al2O3)0.75(ZnO)0.25Fe2O3 Synthesized by stirring

Synthesized by ultra-sonic

assisted stirring

Single Point Surface Area

(m2/g)

184.37 313.98

BET Surface Area (m2/g) 193.62 332.30

Langmuir Surface Area

(m2/g)

268.86 462.37

BET Adsorption Average

Pore Diameter (nm) 5.28 3.38

BJH Adsorption Average


BJH Desorption Average


91

Table No. 4.13.1 Surface area and porosity analysis of ZrO2.Fe2O3

Surface area and porosity ZrO2.Fe2O3 Synthesized by stirring

Synthesized by ultra-sonic

assisted stirring

Single Point Surface Area

(m2/g)

153.85 254.16

BET Surface Area (m2/g) 171.51 217.75

Langmuir Surface Area

(m2/g)

193.77 381.28

BET Adsorption Average

Pore Diameter (nm)

4.30 2.84

BJH Adsorption Average

Pore Diameter (nm)

3.85 2.97

BJH Desorption Average

Pore Diameter (nm)

3.62 3.39

4.5 Photocatalytic Activity

4.5.1 Optimization of pH for the degradation of Methyl Orange

Catalysts used for the optimization of pH were (Al2O3)0.50(ZnO)0.50(Fe2O3) and

(ZrO2)0.50(ZnO)0.50Fe2O3) with an initial pH from 1 to 9 using odd numbers. Degradation

was calculated with 20min interval of time up to 140 min on each pH value by taking

absorbance at 507 nm with the help of UV/Vis spectrophotometer and percentage

degradation was calculated from the absorbance. Degradation was increased with increase in

time up to 120 min and almost remained constant after 120 to 140 min. Degradation

efficiency was increased from 1 to 3 pH and then decreased from 3 to 9 pH so the maximum

degradation was 78.12% with (Al2O3)0.50(ZnO)0.50(Fe2O3) and 65.24% with and

(ZrO2)0.50(ZnO)0.50Fe2O3) at pH = 3 with catalyst dose 50mg/100ml, dye concentration 50

ppm at room temperature. Experiments were performed in triplicate. The results are shown in

table No. 4.14 and 4.15 and graphical representation is given in Fig. 4.64 and 4.65.

Photocatalytic activity should be increased with the increase in pH as at higher pH values

more OH ions are available which increase the formation of OH radicals (Kaur et al., 2013).

In this case degradation was decreased by increasing pH of the solution because at lower pH

92

values formation of HO2 radicals takes place which compensate the deficiency of hydroxide

ions (Ku and Hsieh, 1992). Methyl orange is anionic in nature and oxidative attack of the

hole on dye molecule is rate determining step so at low pH this attack will be supported and

more dye molecules will be degraded (Al-Qaradawi and Salman, 2002).

Table No. 4.14 Optimization of pH for the degradation of Methyl Orange With

(Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation with

50mg/100ml catalyst loading, 50ppm initial dye concentration at room temperature

Time (min)

Degradation (%)

pH 1 ± SD pH 3 ± SD pH 5 ± SD pH 7 ± SD pH 9 ± SD

20 12.32 1.01823 15.32 0.89096 9.75 1.06137 5.14 0.91075 2.87 0.96025

40 26.98 1.04652 32.76 1.00381 23.51 1.05217 16.65 0.99278 5.96 1.04794

60 39.19 1.13137 49.46 0.75052 36.46 0.82307 25.15 0.76282 9.18 0.74642

80 55.32 1.04652 65.18 0.9256 48.65 0.85984 33.25 0.88106 12.15 0.95035

100 67.52 1.03238 75.95 1.01221 59.18 1.00381 39.65 0.98316 16.14 1.0502

120 72.78 0.77782 78.21 0.69032 68.81 0.80101 45.44 0.68207 19.32 0.69706

140 72.68 1.04653 78.12 0.69118 69.21 0.94723 45.67 0.61993 20.13 0.67693

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

80

Degra

dation (

%)

Time (Min)

pH 1

pH 3

pH 5

pH 7

pH 9

Fig. 4.64 Optimization of pH for the degradation of methyl orange with

(Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at


93

Table No. 4.15 Optimization of pH for the degradation of Methyl Orange With

(ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at


Time

(Min) Degradation (%)


20 7.42 0.9832 10.15 0.88488 6.12 0.86522 3.52 0.97337 2.21 0.96354

40 20.92 1.0324 24.14 0.92916 17.85 0.89819 11.41 1.00143 5.74 0.9911

60 31.32 1.2987 37.65 1.16883 23.17 1.1039 20.21 1.23377 9.95 1.22078

80 42.13 0.8756 46.22 0.78804 38.32 0.77928 29.18 0.81431 11.15 0.80555

100 50.95 1.1896 56.12 1.07064 46.41 1.07064 35.32 1.08254 15.51 1.07064

120 60.46 0.9632 65.51 0.86688 57.18 0.87651 43.14 0.90541 17.23 0.84762

140 61.47 1.1569 65.75 1.04121 58.90 0.99493 44.85 1.06435 18.15 0.99493

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

80

Degra

dation (

%)

Time (Min)

pH 1

pH 3

pH 5

pH 7

pH 9

Fig. 4.65 Optimization of pH for the degradation of methyl orange with

(ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at

50mg/100ml catalyst loading, 50ppm initial dye concentration at room temperature.

94

4.5.2 Optimization of catalyst dose for the degradation of Methyl Orange

(Al2O3)0.50(ZnO)0.50(Fe2O3) and (ZrO2)0.50(ZnO)0.50(Fe2O3) were used for the

optimization of catalyst concentration starting from 20mg/100ml to 70mg/100ml degradation

was increased from 20mg to 60mg/100ml. Degradation was increased 40.18 to 80.87 % with

(Al2O3)0.50(ZnO)0.50(Fe2O3) and 13.39 to 69.95 with (ZrO2)0.50(ZnO)0.50(Fe2O3) in 140 min

time of reaction. By increasing photocatalyst amount more particles will be available which

leads to more active sites availability (Wang et al., 2013; Rashid et al., 2014). After

60mg/100ml there was decrease in degradation efficiency because more increase in

concentration can decrease the light passing through dye solution which decreased the

photocatalytic efficiency (Sherly et al., 2014). Results are shown in table No. 4.16, 4.17 and

Fig. 4.66 and 4.67. Optimized dose for the degradation of methyl orange was 60mg/100ml at

optimum pH and 50 ppm dye solution at room temperature.

Table No. 4.16 Optimization of catalyst dose for the degradation of Methyl Orange

With (Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at

pH = 3, and 50ppm initial dye concentration at room temperature

Time

(Min)

Degradation (%)

20mg ± SD 30mg ± SD 40mg ± SD 50mg ± SD 60mg ± SD 70mg ± SD

20 5.14 0.6524 8.34 0.63935 11.81 0.71978 15.31 0.58064 16.42 0.64653 13.31 0.53497

40 13.25 0.5247 19.27 0.50371 26.07 0.47223 32.43 0.45649 34.19 0.52103 29.11 0.47223

60 21.06 0.8326 30.12 0.78264 41.28 0.75767 49.57 0.70771 56.38 0.82844 48.29 0.81595

80 28.37 0.9356 39.23 0.86075 55.37 0.86075 65.08 0.77655 71.05 0.93279 61.19 0.83268

100 34.51 0.7145 50.01 0.64305 61.55 0.67163 75.21 0.57874 78.37 0.71379 73.22 0.60018

120 39.31 0.4235 57.19 0.37268 66.1 0.4108 78.09 0.33457 80.28 0.42214 76.05 0.35151

140 40.18 0.9245 58.05 0.79507 66.89 0.88752 78.59 0.71186 80.87 0.91858 76.39 0.74884

95

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

80

90

Degra

dation (

%)

Time (Min)

20mg

30mg

40mg

50mg

60mg

70mg

Fig. 4.66 Optimization of catalyst dose for the degradation of methyl orange with

(Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at pH =

3, and 50ppm initial dye concentration at room temperature.

.

Table No. 4.17 Optimization of catalyst dose for the degradation of Methyl Orange

With (ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at

pH = 3, and 50ppm initial dye concentration at room temperature.

Time



20 3.52 0.25931 7.09 0.25672 9.95 0.25801 10.35 0.23079 14.31 0.23597 9.83 0.20485

40 4.31 0.12966 9.35 0.12447 14.85 0.12875 24.13 0.1141 32.84 0.12058 22.89 0.09984

60 7.24 0.19448 14.85 0.18281 25.05 0.1939 37.21 0.1692 49.25 0.18476 35.54 0.14586

80 9.28 0.25931 21.67 0.23857 34.87 0.25698 46.25 0.22301 57.65 0.25153 43.59 0.1893

100 11.05 0.32414 26.31 0.31766 45.28 0.32252 56.01 0.27552 63.29 0.3209 53.75 0.25283

120 13.28 0.32414 32.81 0.31117 54.33 0.32284 65.37 0.27228 69.51 0.31766 60.37 0.23986

140 13.45 0.26548 33.05 0.24159 55.1 0.26521 65.58 0.23893 69.95 0.24955 60.57 0.20176

96

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

80

90

Degra

dation (

%)

Time (Min)

20mg

30mg

40mg

50mg

60mg

70mg

Fig. 4.67 Optimization of catalyst dose for the degradation of methyl orange with

(ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at pH =

3, and 50ppm initial dye concentration at room temperature.

4.5.3 Optimization of dye concentration for the degradation of Methyl Orange

To optimize the concentration of dye for the degradation of Methyl Orange 20 to 70

ppm of dye solution was used at optimum values of pH = 3 and catalyst dose (60mg/100ml).

The degradation efficiency was increased with the increase in dye concentration up to 50

ppm and after this value of concentration the degradation efficiency was decreased. So

(Al2O3)0.50(ZnO)0.50(Fe2O3) and (ZrO2)0.50(ZnO)0.50(Fe2O3) showed maximum degradation

efficiency at 50ppm. Results are shown in table No. 4.18 & 4.19 with graphical

representation in Fig. 4.68 & 4.69. (Al2O3)0.50(ZnO)0.50(Fe2O3) degraded 80.87% while

ZrO2)0.50(ZnO)0.50(Fe2O3) degraded 69.95% methyl orange in 140 min at optimum

conditions. Degradation rate was directly proportional to the concentration of dye molecules

because by increasing dye concentration more molecules are available so the adsorption of

molecules on the surface of photocatalyst increased (Ahmed et al., 2011). Concentration

above the optimized value decreased the degradation efficiency due to opacity of the reaction

mixture which may decrease the penetration of visible light in the reaction mixture (Swetha

and Balakrishna, 2011).

97

Table No. 4.18 Optimization of initial dye concentration for the degradation of Methyl

Orange With (Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-

precipitation at pH = 3, and 60mg/100ml catalyst dose at room temperature.

Time

(Min)

Degradation

(%)

20pp

m ± SD

30ppm

± SD 40pp

m ± SD

50ppm

± SD 60pp

m ± SD

20 7.24 0.78454 9.85 0.70609 12.05 0.76104 16.42 0.70609 14.78 0.62763

40 11.87 0.82412 20.76 0.73347 27.32 0.78291 34.19 0.73347 30.42 0.65105

60 23.18 0.62348 32.54 0.54243 42.85 0.57984 56.38 0.54243 49.06 0.48631

80 29.81 0.27554 40.35 0.25074 56.13 0.27003 71.05 0.24248 64.55 0.21217

100 35.79 0.63857 51.24 0.58748 63.51 0.61303 78.37 0.54917 72.14 0.48531

120 40.17 0.58796 58.11 0.5174 66.13 0.55856 80.28 0.52328 73.21 0.44097

140 40.29 0.45698 58.64 0.42042 66.89 0.42956 80.87 0.39529 74.13 0.33817

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

80

90

Degra

dation (

%)

Time (Min)

20ppm

30ppm

40ppm

50ppm

60ppm

Fig. 4.68 Optimization of initial dye concentration for the degradation of methyl orange

with (Al2O3)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at

pH = 3, and 60mg/100ml catalyst dose at room temperature.

98

Table No. 4.19 Optimization of initial dye concentration for the degradation of Methyl

Orange With (ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-

precipitation at pH = 3, and 60mg/100ml catalyst dose at room temperature.

Time


20ppm ± SD 30ppm ± SD 40ppm ± SD 50ppm ± SD 60ppm ± SD

20 5.98 0.78454 8.56 0.70609 10.5 0.76104 14.31 0.70609 12.73 0.62763

40 10.95 0.82412 18.12 0.73347 24.86 0.78291 32.84 0.73347 28.57 0.65105

60 20.62 0.62348 28.38 0.54243 38.99 0.57984 49.25 0.54243 43.15 0.48631

80 24.61 0.27554 35.45 0.25074 51.03 0.27003 57.65 0.24248 52.85 0.21217

100 29.57 0.63857 44.58 0.58748 57.41 0.61303 63.29 0.54917 58.94 0.48531

120 34.79 0.58796 50.57 0.5174 60.83 0.55856 69.51 0.52328 61.86 0.44097

140 35.03 0.45698 51.01 0.42042 60.99 0.42956 69.95 0.39529 62.65 0.33817

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

80

90

Degra

dation (

%)

Time (Min)

20ppm

30ppm

40ppm

50ppm

60ppm

Fig. 4.69 Optimization of initial dye concentration for the degradation of methyl orange

with (ZrO2)0.50(ZnO)0.50(Fe2O3) synthesized by mechanically stirred co-precipitation at

pH = 3, and 60mg/100ml catalyst dose at room temperature.

99

4.5.4 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3

synthesized by mechanically stirred co-precipitation for the degradation of Methyl

Orange

To optimize value of x value for (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3

was done to get maximum degradation efficiency of methyl orange at optimum conditions of

pH, photocatalyst dose and dye concentration (pH = 3, 60mg/100ml catalyst dose and 50ppm

dye concentration) at room temperature. The results are shown in table No. 4.20 & 4.21 and

Fig. 4.70 & 4.71. Values of x and their respective formulas are shown in table No. 4.22. It

can be seen from the results X=0.25 with formula (Al2O3)0.75(ZnO)0.25Fe2O3 form (Al2O3)1-

x(ZnO)xFe2O3 has maximum degradation of methyl orange. By increasing the ZnO and

decreasing Al2O3 degradation efficiency was decreased but the absence of Al2O3 and ZnO

have very low degradation percentage therefore (Al2O3)0.75(ZnO)0.25Fe2O3 has best results for

the removal of methyl orange. In case of (ZrO2)1-x(ZnO)xFe2O3 X = 0 with formula

ZrO2.Fe2O3 showed maximum degradation efficiency. ZnO has negative effect in this

photocatalyst because by increasing Zn there was decrease in photocatalytic efficiency.

Table No. 4.20 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by

mechanically stirred co-precipitation for the degradation of methyl orange at pH=3,

catalyst dose 60mg/100ml and initial dye concentration 50ppm at room temperature.

Time


X= 0 ± SD X=

0.25 ± SD

X=

0.50 ± SD

X=

0.75 ± SD X= 1 ± SD

20 3.11 0.75632 20.85 0.83256 15.85 0.63985 10.75 0.73363 5.18 0.64287

40 10.24 0.82154 37.94 1.20014 31.72 0.58764 23.18 0.7476 12.97 0.71474

60 17.32 0.97852 61.05 0.96544 52.91 0.86354 39.82 0.92959 21.88 0.87088

80 28.34 1.23547 76.91 0.53214 69.95 0.95485 51.37 1.14899 30.17 1.05015

100 34.21 1.02314 81.07 0.96324 77.28 0.23658 62.74 0.91059 37.06 0.89013

120 39.14 0.96871 83.19 0.62548 80.09 0.48652 76.86 0.93965 51.67 0.86215

140 40.02 0.53214 83.67 0.45981 80.53 0.29364 77.15 0.52682 52.15 0.45232

100

20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80

90

100

Degra

dation (

%)

Time (Min)

x = 0

x = 0.25

x = 0.50

x = 0.75

x = 1

Fig. 4.70 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by mechanically

stirred co-precipitation for the degradation of methyl orange at pH=3, catalyst dose

60mg/100ml and initial dye concentration 50ppm at room temperature.

Table No. 4.21 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by

mechanically stirred co-precipitation for the degradation of methyl orange at pH=3,

catalyst dose 60mg/100ml and initial dye concentration 50ppm at room temperature.

Time


X= 0 ± SD X=0.25 ± SD X=0.50 ± SD X=0.75 ± SD X= 1 ± SD

20 17.85 0.45682 15.87 0.53691 14.31 0.63985 12.73 0.54387 10.85 0.84532

40 35.64 0.26597 33.76 0.53219 32.84 0.58764 28.57 0.48774 23.71 0.23154

60 55.12 0.56987 53.47 0.49633 49.25 0.86354 41.85 0.7081 34.37 0.74521

80 66.15 0.15698 63.15 0.35972 57.65 0.95485 47.84 0.77343 38.75 0.63214

100 69.89 0.39852 66.94 0.25465 63.29 0.23658 51.29 0.18926 41.32 0.51235

120 75.43 0.49521 70.85 0.65123 69.51 0.48652 54.91 0.39895 45.02 0.78951

140 75.81 0.53246 71.05 0.59864 69.95 0.29364 55.65 0.24078 45.63 0.71326

101

20 40 60 80 100 120 140

10

20

30

40

50

60

70

80

Degra

dation (

%)

Time (Min)

x = 0

x = 0.25

x = 0.50

x = 0.75

x = 1

Fig. 4.71 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by mechanically

stirred co-precipitation for the degradation of methyl orange at pH=3, catalyst dose

60mg/100ml and initial dye concentration 50ppm at room temperature.

Table 4.22 value of x and their respective photocatalysts for (Al2O3)1-x(ZnO)xFe2O3 and


X (Al2O3)1-x(ZnO)xFe2O3 (ZrO2)1-x(ZnO)xFe2O3

0 Al2O3.Fe2O3 ZrO2.Fe2O3

0.25 (Al2O3)0.75(ZnO)0.25Fe2O3 (ZrO2)0.75(ZnO)0.25Fe2O3



1 ZnO.Fe2O3 ZnO.Fe2O3

4.5.5 Optimization of x value (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-sonic assisted

mechanically stirred co-precipitation for the degradation of Methyl Orange

Selection of best photocatalyst with respect to their x values for the degradation of

methyl orange with (Al2O3)1-x(ZnO)xFe2O3 & (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-

102

sonic assisted mechanically stirred co-precipitation was done on optimum conditions of pH,

photocatalyst dose and initial dye concentration (pH = 3, 60mg/100ml catalyst dose and

50ppm dye concentration). The results are shown in table No. 4.20 and 4.21. Valu of x and

their respective formulas are shown in table 4.22. It can be observed from the results that

x=0.25 with formulas (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3 have maximum degradation

of methyl orange. Trend in photocatalytic activity was the same as mechanically stirred co-

precipitation but photocatalytic efficiency was increased from 87.67% to 93.52% with

(Al2O3)0.75(ZnO)0.25Fe2O3 and 75.81 to 78.07 % with ZrO2.Fe2O3 at same reaction conditions.

It is due the decrease in particle size and increase in surface area of the photocatalyst so that

more dye particles can adsorbed on photocatalyst surface which leads to the availability of

more active sites for dye molecules (Peng et al., 2005; Zhang et al., 2014).

Table No. 4.23 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-

sonic assisted mechanically stirred co-precipitation for the degradation of methyl

orange at pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room

temperature.

Time


X= 0 ± SD X= 0.25 ± SD X= 0.50 ± SD X=

0.75 ± SD X= 1 ± SD

20 6.12 0.85253 21.34 0.86547 18.57 0.97027 13.73 0.85768 7.33 0.86114

40 11.51 1.04749 43.17 1.14857 34.08 0.99926 31.28 1.14053 13.28 1.09114

60 18.26 0.87029 62.24 0.96544 54.19 0.85924 42.19 0.96061 21.49 0.95636

80 23.41 0.65677 78.41 0.73645 65.47 0.63335 50.04 0.73056 27.54 0.67017

100 33.17 0.94981 89.45 1.02654 74.25 0.92389 61.08 1.01935 35.85 1.0213

120 41.23 0.63161 93.04 0.68541 89.13 0.59631 71.18 0.65114 47.15 0.65114

140 42.15 0.20208 93.52 0.21485 89.72 0.39122 72.01 0.4084 49.12 0.51272

103

20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80

90

100

Degra

dation (

%)

Time (Min)

x = 0

x = 0.25

x = 0.50

x = 0.75

x = 1

Fig. 4.72 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-sonic

assisted mechanically stirred co-precipitation for the degradation of methyl orange at

pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room

temperature.

Table No. 4.24 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-

sonic assisted mechanically stirred co-precipitation for the degradation of methyl

orange at pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room

temperature.

Time


X= 0 ± SD X=

0.25 ± SD

X=

0.50 ± SD

X=

0.75 ± SD X= 1 ± SD

20 19.85 0.71852 16.97 0.54387 15.01 0.45637 11.67 0.54387 10.47 0.3883

40 38.24 0.19218 35.02 0.48774 34.27 0.44172 29.88 0.48774 22.78 0.22076

60 57.85 0.61107 55.89 0.7081 50.95 0.40699 43.02 0.7081 35.12 0.46729

80 69.15 0.51203 65.72 0.77343 59.12 0.29137 49.24 0.77343 39.88 0.12715

100 74.19 0.40988 69.08 0.18926 64.83 0.20372 52.98 0.18926 42.79 0.31882

120 78.38 0.6474 73.52 0.39895 70.11 0.53401 55.88 0.39895 47.98 0.40607

140 78.07 0.58487 73.87 0.24078 70.57 0.49088 56.05 0.24078 48.01 0.43662

104

20 40 60 80 100 120 140

10

20

30

40

50

60

70

80

Degra

dation (

%)

Time (Min)

x = 0

x = 0.25

x = 0.50

x = 0.75

x = 1

Fig. 4.73 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic

assisted mechanically stirred co-precipitation for the degradation of methyl orange at


temperature.

4.5.6 Optimization of pH for the degradation of CI Reactive Black 5

For the optimization of pH the catalysts used were (Al2O3)0.75(ZnO)0.25(Fe2O3) &

ZrO2.Fe2O3 because they showed maximum degradation of methyl orange dye. Initial pH was

taken from 1 to 9 using odd numbers. Degradation efficiency was calculated with 20min

interval of time up to 140 min on each pH value by taking absorbance at 597 nm with the

help of UV/Vis spectrophotometer and percentage degradation was calculated from the

absorbance.

Degradation was increased with increase in time up to 120 min and almost remained

constant after 120 to 140 min. Degradation efficiency was increased up to pH=3 and then

decreased from pH 3 to 7 for both catalysts. At pH 9 degradation was increased again but it

was less than pH 3 so the maximum degradation was achieved at pH = 3 with catalyst dose

60mg/100ml, dye concentration 50 ppm at room temperature. The results are shown in table

105

no. 4.25 & 4.26. Graphical representation of the results is given in Fig. 4.73 & 4.74.

(Al2O3)0.75(ZnO)0.25(Fe2O3) degraded 83.15 % and 72.01 % RB5 at pH 3 & 9 respectively.

Table No. 4.25 Optimization of pH for the degradation of CI Reactive Black 5 With


60mg/100ml catalyst loading, 50ppm initial dye concentration at room temperature.

Time



20 19.32 0.24681 21.33 0.68815 11.47 1.01026 8.54 0.6991 18.37 0.88164

40 33.44 0.75432 38.07 0.27318 21.81 0.61665 15.38 0.26596 31.87 0.87144

60 55.51 0.84732 61.71 0.57417 32.29 0.21428 21.58 0.4572 52.08 0.63158

80 69.31 0.54864 77.54 0.23669 45.57 0.46028 28.03 0.21659 65.31 0.74246

100 72.09 1.03238 81.35 0.78206 51.71 0.37072 37.02 0.96082 69.34 0.81558

120 75.53 0.35478 82.77 0.6371 57.07 0.21758 42.54 0.60712 71.85 0.56215

140 76.36 0.15476 83.15 0.15676 57.45 0.22285 42.94 0.60568 72.01 0.54155

This behavior can be explained by mechanism of dye degradation at acidic and basic

conditions. CI Reactive Black 5 dye has sulfonic (-SO3─) and [2(sulfoxy)ethyl]sulfonyl (-

SO2CH2CH2OSO3─) groups which help in solubilizing of dye in water and reactive group for

dye fixation (Muruganandham et al., 2006). At acidic pH surface of photocatalyst charged

positively so the electrostatic attraction takes place which increase the adsorption of dye

molecules on the surface of photocatalyst another reason for this attraction is positively

charged holes so due these reasons acidic pH increased degradation (Kritikos et al., 2007;

Soltani and Entezari, 2013). Photocatalytic activity again increased at pH 9 due to change in

mechanism of reaction at basic pH there are more hydroxide ion available which help in

oxidation of dye molecule and degradation again increased (Zielińska et al., 2001; Soltani

and Entezari, 2013).

106

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

80

90

Degra

dation (

%)

Time (Min)

pH 1

pH 3

pH 5

pH 7

pH 9

Fig. 4.74 Optimization of pH for the degradation of CI Reactive Black 5 With




ZrO2 Fe2O3) synthesized by mechanically stirred co-precipitation with 60mg/100ml

catalyst loading, 50ppm initial dye concentration at room temperature.

Time



20 16.27 0.53071 18.71 0.34897 10.84 0.53316 7.046 0.35554 13.22 0.82023

40 30.87 0.94137 34.23 0.33752 19.35 0.84082 13.158 0.44533 27.56 0.92419

60 39.54 0.81452 47.38 0.8345 26.92 0.92188 18.5748 0.35871 33.69 0.59162

80 47.58 0.83206 61.26 0.44719 35.42 0.78319 22.6688 0.54139 42.74 0.97016

100 58.52 1.01648 69.75 0.32323 40.72 0.33722 25.2464 0.49388 50.32 0.26269

120 64.08 0.17357 72.76 0.90682 45.72 0.95158 32.004 0.63379 55.76 0.43662

140 64.88 0.24198 72.35 0.45836 46.22 0.25187 32.354 0.22508 56.46 0.57235

107

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

80

Degra

dation (

%)

Time (Min)

pH 1

pH 3

pH 5

pH 7

pH 9

Fig.4.75 Optimization of pH for the degradation of CI Reactive Black 5 With

ZrO2.Fe2O3) synthesized by mechanically stirred co-precipitation with 60mg/100ml


4.5.7 Optimization of photocatalyst dose for the degradation of CI Reactive Black 5

(RB5)

Optimization of catalyst dose for the degradation of CI Reactive Black 5 with

(Al2O3)0.75(ZnO)0.25(Fe2O3) and ZrO2.Fe2O3 was done from 20mg/100ml to 70mg/100ml.

Reaction conditions were pH=3 and 50ppm initial dye concentration at room temperature.

Degradation was increased from 20mg to 60mg/100ml in 140 min.

(Al2O3)0.75(ZnO)0.25(Fe2O3) degraded RB5 83.15% while ZrO2.Fe2O3 degraded RB5 72.35%.

At photocatalyst concentration 70mg/100ml there was decrease in photocatalytic activity. By

the increase of photocatalyst concentration more active sites are available for the dye

molecule to be adsorbed so that degradation was increased up to 60mg/100ml but at

70mg/100 ml suspension becomes opaque due to large amount of suspended particles of

catalyst which may decrease the intensity of light passing through the reaction mixture by

108

scattering it (Daneshvar et al., 2003; Ahmed et al., 2011; Shirsath et al., 2013). Results are

shown in table no. 4.27 & 4.28, Fig. 4.75 & 4.76.


ZrO2 Fe2O3) synthesized by mechanically stirred co-precipitation with 60mg/100ml


Time



20 7.88 0.43931 9.97 0.49768 12.74 0.23546 15.02 0.54124 21.33 0.30035 18.77 0.25208

40 12.58 0.34404 15.24 0.33533 18.52 0.12564 22.14 0.22889 38.07 0.19893 35.84 0.1803

60 18.93 0.5257 21.69 0.40281 28.54 0.32657 33.78 0.80322 61.71 0.22418 49.47 0.2208

80 25.99 0.56838 29.66 0.37892 37.41 0.87416 45.28 0.29006 77.54 0.26445 60.11 0.23606

100 31.85 0.41727 38.45 0.25722 46.85 0.29654 57.44 0.42992 81.35 0.74234 67.12 0.62418

120 36.78 0.26045 43.87 0.24309 57.44 0.32155 65.07 0.33215 82.77 0.20769 71.28 0.17294

140 37.08 0.57615 44.13 0.22743 57.97 0.12777 65.42 0.15478 83.15 0.37662 71.88 0.30702

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

80

90

Degra

dation (

%)

Time (Min)

20mg

30mg

40mg

50mg

60mg

70mg

Fig. 4.76 Optimization of catalysts dose for the degradation of CI Reactive Black 5 With

(Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-precipitation at pH =

3 and 50ppm initial dye concentration at room temperature.

109

Table No. 4.28 Optimization of catalysts dose for the degradation of CI Reactive Black

5 With ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 3 and

50ppm initial dye concentration at room temperature.

Time



20 6.81 0.71523 9.47 0.94388 12.68 1.02657 14.32 0.81465 18.71 0.99692 15.75 0.72679

40 11.36 0.90502 15.31 0.51949 22.56 0.76496 25.55 0.98858 34.23 0.54895 28.56 0.67858

60 16.84 0.85947 21.85 0.87184 31.58 0.94992 36.87 0.80597 47.38 1.02023 39.85 0.81734

80 22.45 0.90745 30.94 1.0171 39.32 0.73585 47.32 0.94194 61.26 0.75258 51.24 0.92599

100 29.33 0.49588 39.12 0.92247 48.55 0.87963 54.71 0.89804 69.75 0.94041 60.35 0.71778

120 34.55 0.56071 44.25 0.68939 53.25 0.8062 59.55 0.58008 72.76 0.86316 64.85 0.43662

140 35.08 0.91238 44.86 0.36758 53.84 0.9417 59.89 0.94129 72.35 0.94375 65.18 0.9142

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

80

Degra

dation (

%)

Time (Min)

20mg

30mg

40mg

50mg

60mg

70mg

110

Fig. 4.77 Optimization of catalysts dose for the degradation of CI Reactive Black 5 With

ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 3 and 50ppm

initial dye concentration at room temperature.

4.5.8 Optimization of initial dye concentration for the degradation of CI Reactive Black

5

Concentration of dye is an important factor for photocatalytic activity. CI Reactive

Black 5 was degraded with initial concentration from 20 ppm to 60 ppm. Degradation

efficiency was increased with the increased in dye concentration up to 50 ppm after that it

was decreased at 60 ppm so the optimum value was 50 ppm. Table 4.29 & 4.30 contain the

mean values for % degradation with time and graphically represented in Fig. 4.77 & 4.78.

Maximum degradation was 83.15% with (Al2O3)0.75(ZnO)0.25(Fe2O3) and 72.35% with

ZrO2.Fe2O3. This factor can be explained as the concentration was increased there was

increase in degradation efficiency because more dye molecules were available to adsorb on

the active sites of photocatalyst so the effective collisions were increased. After a specific

concentration (50ppm) degradation efficiency was decreased due to decrease in intensity of

light passing through reaction mixture as more light will be absorbed by dye molecules than

the photocatalyst (Muruganandham et al., 2006; Yao et al., 2010; Konicki et al., 2013).

Table No. 4.29 Optimization of initial dye concentration for the degradation of CI

Reactive Black 5 With (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred

co-precipitation at pH = 3 and 60mg/100ml catalyst dose at room temperature.

Time



20 9.55 0.26208 12.85 0.25931 15.2 0.25931 21.33 0.44826 18.41 0.47845

40 16.74 0.95246 20.89 0.94483 23.33 0.29655 38.07 0.29655 30.25 0.3625

60 27.12 0.49866 35.76 0.25931 42.15 0.94483 61.71 0.94483 55.34 0.26533

80 35.45 0.23035 44.85 0.29655 53.21 0.25931 77.54 0.25931 66.23 0.12985

100 42.34 0.38887 55.79 0.94483 59.38 0.32414 81.35 0.25931 73.85 0.28706

120 53.88 0.23872 62.7 0.32414 68.56 0.32414 82.77 0.32414 76.24 0.36918

140 54.12 0.36156 62.95 0.14781 68.97 0.29561 83.15 0.27553 76.61 0.15725

111

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

80

90

Degra

dation (

%)

Time (Min)

20ppm

30ppm

40ppm

50ppm

60ppm

Fig. 4.78 Optimization of initial dye concentration for the degradation of CI Reactive

Black 5 With (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-

precipitation at pH = 3 and 60mg/100ml catalyst dose at room temperature.

Table No. 4.30 Optimization of initial dye concentration for the degradation of CI

Reactive Black 5 With ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation

at pH = 3 and 60mg/100ml catalyst dose at room temperature.

Time



20 12.07 0.93654 13.27 0.94431 15.21 0.95642 18.71 0.5327 16.69 0.79654

40 21.34 0.83568 23.76 0.35078 26.52 0.84562 34.23 0.97546 30.14 0.94968

60 29.38 0.72657 31.94 0.85683 35.46 0.32154 47.38 0.8457 41.26 0.23458

80 37.56 0.89658 41.28 0.95833 45.82 0.76542 61.26 0.75468 52.66 0.73256

100 41.78 0.66547 46.42 0.67292 52.75 0.98745 69.75 0.91258 59.25 0.82578

120 45.63 0.96597 51.27 0.95875 57.63 0.84125 72.76 0.99462 61.84 0.52565

140 45.86 0.32365 51.53 0.62206 57.97 0.62145 72.35 0.24853 61.77 0.89654

112

20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80

De

gra

datio

n (

%)

Time (Min)

20ppm

30ppm

40ppm

50ppm

60ppm

Fig. 4.79 Optimization of initial dye concentration for the degradation of CI Reactive

Black 5 With ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 3

and 60mg/100ml catalyst dose at room temperature.

4.5.9 Optimization of x values for (Al2O3)1-x(ZnO)xFe2O3 & (ZrO2)1-x(ZnO)xFe2O3

synthesized by mechanically stirred co-precipitation for the degradation of CI Reactive

Black 5

Degradation of reactive black B was done on optimum conditions of pH 3,

photocatalyst dose 60mg/100ml and initial dye concentration 50ppm at room temperature to

optimize the value of x for (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3 synthesized by

mechanically stirred co-precipitation. The results are shown in table No. 4.31 & 4.32 and

Fig. 4.79 and 4.80. Value of x and their respective formulas are shown in table 4.22. It can be

observed from the results x=0.25 for (Al2O3)1-x(ZnO)xFe2O3 and x = 0 for (ZrO2)1-

x(ZnO)xFe2O3. (Al2O3)1-x(ZnO)xFe2O3 showed maximum degradation 83.15% with

(Al2O3)0.75(ZnO)0.25(Fe2O3) and minimum degradation with 35.84% with Al2O3.Fe2O3.

(ZrO2)1-x(ZnO)xFe2O3 showed maximum degradation 72.35% with ZrO2.Fe2O3 and minimum

degradation 40.78 with ZnO.Fe2O3.

113

Table No. 4.31 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by

mechanically stirred co-precipitation for the degradation of CI Reactive Black 5 at


temperature.

Time (Min)

Degradation (%)

X= 0 ± SD X= 0.25 ± SD X= 0.50 ± SD X= 0.75 ± SD X= 1 ± SD

20 3.14 0.21043 21.33 0.3073 14.41 0.5468 10.85 0.49212 9.11 0.74902

40 9.44 0.09901 38.07 0.35987 24.52 0.3214 22.74 0.28926 11.27 0.91186

60 16.33 0.22097 61.71 0.20237 38.45 0.2154 33.84 0.59386 17.35 0.50616

80 21.41 0.33667 77.54 0.4722 51.28 0.1254 44.25 0.21286 25.74 0.63214

100 29.5 0.53521 81.35 0.20897 65.58 0.5647 55.12 0.50823 33.24 0.86807

120 35.47 0.38538 82.77 0.38538 69.81 0.6547 61.35 0.8923 40.51 0.81879

140 35.84 0.15705 83.15 0.35562 69.92 0.4658 61.87 0.21456 40.78 0.35683

20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80

90

Degra

dation (

%)

Time (Min)

x = 0

x = 0.25

x = 0.50

x = 0.75

x = 1

Fig. 4.80 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by mechanically

stirred co-precipitation for the degradation of CI Reactive Black 5 at pH=3, catalyst

dose 60mg/100ml and initial dye concentration 50ppm at room temperature.

114

Table No. 4.32 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by

mechanically stirred co-precipitation for the degradation of CI Reactive Black 5 at


temperature.

Time (Min)

Degradation (%)

X= 0 ± SD X=

0.25 ± SD

X=

0.50 ± SD

X=

0.75 ± SD X= 1 ± SD

20 18.71 0.44312 15.32 0.53691 12.98 0.63985 10.01 0.54387 9.11 0.74902

40 34.23 0.8187 26.31 0.65236 21.36 0.99494 17.82 0.81461 11.27 0.91186

60 47.38 0.87675 39.72 0.97225 26.84 0.51812 21.75 0.8974 17.35 0.50616

80 61.26 0.66312 48.52 0.78778 34.21 0.8194 28.51 0.60273 25.74 0.63214

100 69.75 0.8918 58.65 0.81136 41.74 0.31848 37.21 0.96655 33.24 0.86807

120 72.76 0.69266 63.12 0.68886 49.35 0.75029 43.51 0.86982 40.51 0.81879

140 72.35 0.35408 63.74 0.21905 49.87 0.20555 43.83 0.38372 40.78 0.35683

20 40 60 80 100 120 140

10

20

30

40

50

60

70

80

Degra

dation (

%)

Time (Min)

x = 0

x = 0.25

x = 0.50

x = 0.75

x = 1

Fig. 4.81 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by mechanically

stirred co-precipitation for the degradation of CI Reactive Black 5 at pH=3, catalyst

dose 60mg/100ml and initial dye concentration 50ppm at room temperature.

115

4.5.10 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 & (ZrO2)1-x(ZnO)xFe2O3

synthesized by ultra-sonic assisted mechanically stirred co-precipitation for the

degradation of CI Reactive Black 5

(Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic assisted

mechanically stirred co-precipitation were used to optimize the x value as well as to compare

the photocatalytic activity of samples synthesized by mechanically stirred co-precipitation

method. The results are shown in table no. 4.33 & 4.34 and Fig. 4.81 & 4.82. Value of x and

their respective formulas are shown in table 4.22. It was found that (Al2O3)0.75(ZnO)0.25Fe2O3

and ZrO2.Fe2O3 synthesized by ultra-sonic assisted mechanically stirred co-precipitation are

most active photocatalysts similar to the photocatalysts synthesized by mechanically stirred

co-precipitation. But photocatalytic activity of photocatalysts synthesized by ultra-sonic

assisted mechanically stirred co-precipitation was high as compared to photocatalysts

synthesized by mechanically stirred co-precipitation. Degradation was increased from

83.15% to 91.08% with (Al2O3)0.75(ZnO)0.25(Fe2O3) and 72.5% to 83.21% with Al2O3.Fe2O3.

The basic reason for the increase in photocatalytic activity was particle size and surface area

of the sample. Particles size was decreased by ultra-sonic assisted mechanically stirred co-

precipitation which caused the increase in surface area and decreased in pore volume this

change on surface of photocatalyst increased adsorption of dye molecules which lead to

increase in photocatalytic activity. (Tratnyek and Johnson, 2006; Shah et al., 2013).

Table No. 4.33 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-

sonic assisted mechanically stirred co-precipitation for the degradation of CI Reactive

Black 5 at pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at

room temperature.

Time


X= 0 ± SD X=

0.25 ± SD

X=

0.50 ± SD

X=

0.75 ± SD X= 1 ± SD

20 6.45 0.52185 16.08 0.36208 12.58 0.42257 10.84 0.35613 8.45 0.78431

40 9.56 0.93169 29.64 0.67766 28.74 0.52164 22.54 0.21123 15.74 0.98367

60 13.25 0.89274 48.25 0.56463 44.84 0.28052 34.88 0.60806 22.58 0.60606

80 22.85 0.31981 67.33 0.70015 54.36 0.90212 49.51 0.56545 33.54 0.39392

100 30.54 0.27779 80.47 0.47315 67.85 0.73172 64.45 0.80733 49.65 0.91561

120 41.77 0.32297 90.75 0.26752 71.85 0.59375 68.05 0.53914 51.87 0.75426

140 41.98 0.76726 91.08 0.18548 72.31 0.33774 68.51 0.25257 52.25 0.60889

116

20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80

90

100

Degra

dation (

%)

Time (Min)

x = 0

x = 0.25

x = 0.50

x = 0.75

x = 1

Fig. 4.82 Optimization of x value for (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-sonic

assisted mechanically stirred co-precipitation for the degradation of CI Reactive Black

5 at pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room

temperature.

Table No. 4.34 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-

sonic assisted mechanically stirred co-precipitation for the degradation of CI Reactive

Black 5 at pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at

room temperature.

Time



20 20.77 0.78259 16.33 0.80036 13.55 0.85637 11.15 0.84153 8.45 0.8431

40 42.35 0.97296 31.54 0.93897 25.46 0.54172 22.25 0.6608 15.74 0.83668

60 56.84 0.51941 43.55 0.72313 36.78 0.60699 33.89 0.88664 22.58 0.96061

80 67.35 1.09624 50.44 0.96515 48.54 0.91373 44.52 0.28263 33.54 0.99392

100 75.29 0.8443 59.87 0.95898 56.84 0.80372 53.28 0.90168 49.65 0.61561

120 83.07 0.76324 71.35 0.82714 63.76 0.93401 59.14 0.46459 51.87 0.85426

140 83.21 0.70299 71.67 0.92624 63.96 0.89088 59.77 0.91725 52.25 0.80889

117

20 40 60 80 100 120 140

10

20

30

40

50

60

70

80

90

Degra

dation (

%)

Time (Min)

x = 0

x = 0.25

x = 0.50

x = 0.75

x = 1

Fig. 4.83 Optimization of x value for (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic

assisted mechanically stirred co-precipitation for the degradation of CI Reactive Black

5 at pH=3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room

temperature.

4.5.11 Optimization of pH for the degradation of Methylene Blue

Initial pH of the reaction mixture plays an important role in photocatalytic

degradation of dyes (Yao and Wang, 2010). Initial pH of solution for degradation of

methylene blue was optimized at pH 1 to 9 with odd numbers with 60mg/100ml catalyst

loading and 50ppm initial dye concentration. Photocatalysts used for the degradation of

methylene blue were (Al2O3)0.75(ZnO)0.25(Fe2O3) and ZrO2.Fe2O3. The degradation

efficiency was increased by increasing pH and the maximum degradation was achieved at

pH=9. (Al2O3)0.75(ZnO)0.25(Fe2O3) degraded MB 76.52% while ZrO2.Fe2O3 degraded MB

64.57% Results with mean values for degradation and their ± SD are given in Table No.

4.35& 4.36 and graphically represented in Fig. 4.83 & 4.84. Methylene blue is a cationic dye

it was attracted towards negatively charged photocatalyst at high pH value due to this

attraction more dye molecules were adsorbed on catalyst surface and photocatalytic activity

was increased (Guillard et al., 2003). Another factor which plays important role is the

118

availability of hydroxide ions at high pH value more hydroxide ions were produced and leads

to increase in the production OH radicals which increased oxidative degradation of

methylene blue at pH = 9 (Chakrabarti and Dutta, 2004; Talebian and Nilforoushan, 2010;

Sultana et al., 2015).

Table No. 4.35 Optimization of pH for the degradation of methylene blue with


60mg/100ml catalyst dose and 50ppm initial dye concentration at room temperature.

Time

(Min)

Degradation (%)


20 10.31 1.01823 9.34 0.98995 8.35 1.11723 4.51 0.98995 15.24 0.98995

40 21.34 1.04652 16.37 1.10309 15.25 1.13137 8.33 1.10309 29.91 1.10309

60 36.03 1.13137 27.19 0.82024 24.91 0.84853 11.71 0.82024 43.18 0.82024

80 45.91 1.04652 38.45 0.98995 32.52 0.9051 14.63 0.98995 52.08 0.98995

100 56.43 1.03238 49.05 1.11723 38.41 1.10309 16.24 1.11723 62.94 1.11723

120 67.55 0.77782 61.25 0.74953 43.71 0.83439 17.64 0.74953 76.03 0.74953

140 67.83 1.04653 61.98 0.71256 44.09 0.9568 17.87 0.71256 76.52 0.71256

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

80

Degra

dation (

%)

Time (Min)

pH 1

pH 3

pH 5

pH 7

pH 9

Fig. 4.84 Optimization of pH for the degradation of methylene blue with



119

Table No. 4.36 Optimization of pH for the degradation of methylene blue with

ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at 60mg/100ml

catalyst dose and 50ppm initial dye concentration at room temperature.

Time



20 7.24 0.2354 6.54 0.53687 4.25 0.23587 2.18 0.54699 8.13 0.89542

40 17.85 0.35496 14.58 0.49635 11.89 0.12365 9.88 0.65489 20.27 0.62381

60 29.84 0.16597 25.87 0.26587 20.18 0.32156 12.55 0.51987 33.15 0.85742

80 41.35 0.59876 38.22 0.69874 28.34 0.59874 16.48 0.84592 45.38 0.26587

100 51.37 0.64782 49.94 0.52134 35.28 0.21568 20.78 0.79658 56.54 0.4237

120 59.68 0.24796 58.44 0.86688 43.25 0.21654 24.92 0.90541 64.18 0.62374

140 60.14 0.34569 58.73 0.6548 43.89 0.35982 25.05 0.32154 64.57 0.24621

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

Degra

dation (

%)

Time (Min)

pH 1

pH 3

pH 5

pH 7

pH 9

Fig. 4.85 Optimization of pH for the degradation of methylene blue with ZrO2.Fe2O3

synthesized by mechanically stirred co-precipitation at 60mg/100ml catalyst dose and

50ppm initial dye concentration at room temperature.

120

4.5.12 Optimization of catalyst dose for the degradation of Methylene Blue

Optimization of catalyst does was done at 20mg/100ml to 70mg/100ml at optimized

pH and 50ppm of dye solution. Degradation was increased from 20mg to 60mg/100ml and

76.23% and 64.57 % of methylene blue was degraded with (Al2O3)0.75(ZnO)0.25Fe2O3 and

ZrO2.Fe2O3 in 140 min time of reaction. Further increase in photocatalyst loading there was

decrease in photocatalytic efficiency. Mean values with ±SD are shown in table No. 4.37 and

4.38 by graphical representation in Fig. 4.85 and 4.86. Increase in photocatalytic efficiency is

due the increase in amount of nanophotocatalyst particles in the reaction mixture so

adsorption of methylene blue was increased. Decrease in efficiency is due to light scattering

by access amount of solid particles present in reaction mixture(Sarasidis et al., 2014; Wang

et al., 2014).

Table No. 4.37 Optimization of catalyst dose for the degradation of methylene blue with

(Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 9

and 50ppm initial dye concentration at room temperature.

Time



20 5.15 0.55454 7.18 0.54345 10.24 0.61181 12.78 0.49354 15.35 0.54955 13.37 0.45472

40 11.26 0.43551 18.56 0.41808 23.52 0.39195 26.14 0.37889 30.85 0.43245 27.43 0.39195

60 19.45 0.68273 28.84 0.64176 35.34 0.62129 38.47 0.58032 43.25 0.67932 40.54 0.66908

80 24.35 0.75784 30.56 0.69721 38.72 0.69721 46.34 0.62901 52.46 0.75556 49.34 0.67447

100 28.15 0.57161 33.45 0.51444 41.28 0.53713 52.24 0.46299 63.54 0.57103 57.48 0.48014

120 37.08 0.34727 42.28 0.3056 53.08 0.33686 65.25 0.27435 76.04 0.34615 68.12 0.28824

140 37.81 0.75809 42.47 0.65196 53.54 0.72777 66.12 0.58373 76.23 0.75324 68.72 0.61405

121

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

80

90

Degra

dation (

%)

Time (Min)

20mg

30mg

40mg

50mg

60mg

70mg

Fig. 4.86 Optimization of catalyst dose for the degradation of methylene blue with

(Al2O3)0.75(ZnO)0.25Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 9

and 50ppm initial dye concentration at room temperature.

Table No. 4.38 Optimization of catalyst dose for the degradation of methylene blue with



Time



20 3.46 0.2152 4.65 0.2438 6.25 0.5103 7.08 0.85065 8.13 0.7969 8.74 0.6267

40 5.17 0.1050 8.23 0.1194 13.98 0.4765 18.59 0.5988 20.27 0.5489 19.91 0.4678

60 8.33 0.1594 15.82 0.1718 23.56 0.2499 29.18 0.8059 33.15 0.7202 30.29 0.6173

80 10.75 0.2074 19.03 0.2171 30.85 0.6358 34.72 0.2419 45.38 0.2528 38.32 0.2259

100 12.17 0.2495 24.23 0.2922 37.74 0.4796 41.38 0.3898 56.54 0.3940 46.25 0.3177

120 15.56 0.2560 30.55 0.2893 44.15 0.8062 47.69 0.5800 64.18 0.5863 50.78 0.4366

140 16.14 0.2123 31.08 0.2367 44.83 0.6417 48.46 0.2412 64.57 0.2437 51.45 0.3142

122

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

Degra

dation (

%)

Time (Min)

20mg

30mg

40mg

50mg

60mg

70mg

Fig. 4.87 Optimization of catalyst dose for the degradation of methylene blue with



4.5.13 Optimization of dye initial concentration for the degradation of Methylene Blue

Photocatalytic degradation of methylene blue was carried out with different initial

concentrations ranging from 20 ppm to 60 ppm for the optimization of initial concentration

of methylene blue solution to get maximum degradation. (Al2O3)0.75(ZnO)0.25(Fe2O3)

degraded 76.23% and ZrO2.Fe2O3 degraded 64.57% of methylene blue at 50ppm initial dye

concentration. Results with mean degradation percent and their ± SD are shown in Table No.

4.39 & 4.40 and Fig. 4.87 & 4.88. It can be observed from the results that degradation of

methylene blue was increased by increasing initial concentration of dye and got maximum

degradation at 50 ppm of dye solution due to increase in dye molecule in solution which may

increase adsorption rate at the surface of photocatalyst. Further increase in initial

concentration decrease the degradation efficiency due decrease in intensity of light needed to

active photocatalyst (Shirsath et al., 2013).

123

Table 4.39 Optimization of initial dye concentration for the degradation of methylene

blue with (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-

precipitation at pH = 9 and 60mg/100ml catalyst dose at room temperature.

Time


20mg ± SD 30mg ± SD 40mg ± SD 50mg ± SD 60mg ± SD

20 6.36 0.69824 9.35 0.62136 11.58 0.76104 15.35 0.62136 14.18 0.53349

40 10.63 0.74995 19.38 0.67479 25.68 0.78291 30.85 0.67479 27.15 0.56641

60 20.34 0.57984 28.96 0.49361 37.54 0.57984 43.25 0.49361 39.84 0.42795

80 27.71 0.26176 35.15 0.23319 46.28 0.27003 52.46 0.22551 48.84 0.19095

100 31.13 0.61941 43.54 0.55811 55.88 0.61303 63.54 0.52171 58.78 0.44163

120 35.13 0.58208 48.84 0.48636 61.52 0.55856 76.04 0.49188 68.74 0.40569

140 35.52 0.42042 49.26 0.40781 61.98 0.42956 76.23 0.37553 68.16 0.3145

20 40 60 80 100 120 140 1600

10

20

30

40

50

60

70

80

90

Degra

dation (

%)

Time (Min)

20ppm

30ppm

40ppm

50ppm

60ppm

Fig 4.88 Optimization of initial dye concentration for the degradation of methylene blue

with (Al2O3)0.75(ZnO)0.25(Fe2O3) synthesized by mechanically stirred co-precipitation at

pH = 3 and 60mg/100ml catalyst dose at room temperature.

124

Table 4.40 Optimization of initial dye concentration for the degradation of methylene

blue with ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 9


Time


20mg ± SD 30mg ± SD 40mg ± SD 50mg ± SD 60mg ± SD

20 6.07 0.23654 6.58 0.49636 7.85 0.45968 8.13 0.13268 7.05 0.79654

40 12.68 0.3568 14.95 0.13654 16.75 0.23657 20.27 0.32587 18.56 0.34968

60 22.54 0.2657 25.85 0.36548 27.54 0.16548 33.15 0.31549 30.54 0.23458

80 30.54 0.49658 34.51 0.28797 39.41 0.02315 45.38 0.32155 41.36 0.13256

100 39.84 0.36547 46.85 0.31587 50.36 0.31256 56.54 0.42366 53.25 0.02578

120 45.38 0.26597 52.34 0.46987 56.87 0.12366 64.18 0.32156 59.56 0.25648

140 45.81 0.12365 52.96 0.36548 58.08 0.13287 64.57 0.18975 59.94 0.48965

20 40 60 80 100 120 1400

10

20

30

40

50

60

70

De

gra

datio

n (

%)

Time (Min)

20ppm

30ppm

40ppm

50ppm

60ppm

Fig. 4.89 Optimization of initial dye concentration for the degradation of methylene

blue with ZrO2.Fe2O3 synthesized by mechanically stirred co-precipitation at pH = 9


125

4.5.14 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3 and

synthesized by mechanically stirred co-precipitation for the degradation of Methylene

Blue

The general formulas (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3 has different

composition between oxides with different values of x to optimize value of x for the best

photocatalyst composition for the degradation of methylene blue was done on optimum

conditions pH = 9, catalyst dose 60mg/100ml and initial dye concentration 50 ppm. The

results with mean degradation values are shown in Table No. 4.41 & 4.42 and Fig. 4.89 &

4.90. Value of x and their respective formulas are shown in Table No. 4.22.

(Al2O3)0.75(ZnO)0.25(Fe2O3) with x= 0.25 degraded 76.72% which was the maximum

degradation and minimum degradation of MB was 44.83% with Al2O3.Fe2O3 (x= 0). Other

photocatalyst (ZrO2)1-x(ZnO)xFe2O3 showed maximum degradation 64.57% with ZrO2.Fe2O3

(x= 0) and minimum degradation was 45.63% with ZnO.Fe2O3 (x=1).

Table No. 4.41 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 synthesized by

mechanically stirred co-precipitation for the degradation of methylene blue at pH = 9,

60mg/100ml catalyst dose and 50ppm initial dye concentration at room temperature

Time



20 2.98 0.2654 15.24 0.7854 9.11 0.5468 7.31 0.1246 4.95 0.3878

40 8.12 0.1547 30.57 0.5623 23.54 0.3214 16.53 0.2351 14.05 0.2354

60 15.68 0.3564 43.65 0.3264 31.34 0.2154 22.15 0.6857 19.38 0.5624

80 23.47 0.4951 52.42 0.2165 41.63 0.1254 30.38 0.3257 26.15 0.3571

100 32.58 0.8234 63.25 0.3215 54.12 0.5647 42.38 0.6146 37.35 0.7563

120 44.25 0.4235 76.21 0.4235 62.13 0.6547 59.43 0.7265 54.95 0.2431

140 44.83 0.3141 76.72 0.3124 62.54 0.4658 59.88 0.4598 55.16 0.3547

126

20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80

Degra

dation (

%)

Time (Min)

x = 0

x = 0.25

x = 0.50

x = 0.75

x = 1

Fig. 4.90 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 synthesized by mechanically

stirred co-precipitation for the degradation of methylene blue at pH = 9, 60mg/100ml


Table No. 4.42 Optimization of x value of (ZrO2)1-x(ZnO)xFe2O3 synthesized by

mechanically stirred co-precipitation for the degradation of methylene blue at pH = 9,


Time


X= 0 ± SD X=

0.25 ± SD

X=

0.50 ± SD

X=

0.75 ± SD X= 1 ± SD

20 8.13 0.45682 6.34 0.53691 5.75 0.63985 5.93 0.54387 4.65 0.84532

40 20.2

7 0.18618 15.24 0.45236 13.8 0.49949 12.86 0.21461 9.78 0.33154

60 33.1

5 0.4274 26.96 0.37225 22.12 0.51812 19.34 0.2974 15.23 0.24521

80 45.3

8 0.11303 38.56 0.28778 33.15 0.38194 26.57 0.50273 24.35 0.53214

100 56.5

4 0.33874 47.12 0.21136 41.98 0.23185 35.21 0.16655 33.05 0.41235

120 64.1

8 0.27141 56.87 0.46889 50.63 0.35029 46.78 0.38698 44.81 0.18951

140 64.5

7 0.37272 57.41 0.21905 50.91 0.20555 46.81 0.23837 45.63 0.21326

127

20 40 60 80 100 120 140

10

20

30

40

50

60

70

Degra

dation (

%)

Time (Min)

x = 0

x = 0.25

x = 0.50

x = 0.75

x = 1

Fig. 4.91 Optimization of x value of (ZrO2)1-x(ZnO)xFe2O3 synthesized by mechanically

stirred co-precipitation for the degradation of methylene blue at pH = 9, 60mg/100ml


4.5.15 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3

synthesized by ultra-sonic assisted mechanically stirred co-precipitation for the

degradation of Methylene Blue

Optimum conditions for the degradation of methylene blue were used for the

selection of best photocatalyst from (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3 with

respect to x value. The results are show in Table No. 4.13 and Fig. 4.21 and value of x and

their respective formulas are shown in Table No. 4.22. Table No. 4.43 and 4.44 contains the

mean values for percent degradation of MB with their ± SD. Best metals oxide composition

from (Al2O3)1-x(ZnO)xFe2O3 was x = 0.25 with formula (Al2O3)0.75(ZnO)0.25(Fe2O3) which

degraded methylene blue 83.74% and x=0 with formula ZrO2.Fe2O3 from (ZrO2)1-

x(ZnO)xFe2O3 degraded 73.97% of MB. Minimum degradation was 45.82% with

Al2O3.Fe2O3 and 47.18% with ZnO.Fe2O3. Photocatalysts synthesized by ultra-sonic assisted

mechanically stirred co-precipitation showed increase in photocatalytic efficiency as

compared to photocatalysts synthesized by mechanically stirred co-precipitation due to small

particle size and large surface area which increase the adsorption of dye molecules on surface

of photocatalyst. (Huang et al., 2013).

128

Table No. 4.43 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-

sonic assisted mechanically stirred co-precipitation for the degradation of methylene

blue at pH = 9, 60mg/100ml catalyst dose and 50ppm initial dye concentration at room

temperature

Time


X= 0 ± SD X= 0.25

± SD X= 0.50

± SD X= 0.75

± SD X= 1 ± SD

20 4.12 0.72465 16.11 0.73565 11.34 0.82473 8.15 0.72903 6.88 0.53159

40 7.98 0.36854 32.93 0.75296 26.89 0.5796 19.97 0.2347 13.06 0.64852

60 14.25 0.76586 46.88 0.84959 41.18 0.75613 31.28 0.84534 20.43 0.6734

80 24.34 0.59109 64.34 0.63335 56.91 0.54468 47.36 0.62828 31.54 0.77102

100 33.91 0.86433 74.75 0.52572 69.31 0.81302 60.85 0.89703 45.37 0.79512

120 45.28 0.58108 83.05 0.63058 75.29 0.54861 67.73 0.59905 54.11 0.50473

140 45.82 0.18793 83.74 0.2084 75.82 0.37948 68.08 0.39615 54.32 0.34707

20 40 60 80 100 120 1400

10

20

30

40

50

60

70

80

90

Degra

dation (

%)

Time (Min)

x = 0

x = 0.25

x = 0.50

x = 0.75

x = 1

Fig. 4.92 Optimization of x value of (Al2O3)1-x(ZnO)xFe2O3 synthesized by ultra-sonic

assisted mechanically stirred co-precipitation for the degradation of methylene blue at

pH = 9, 60mg/100ml catalyst dose and 50ppm initial dye concentration at room

temperature.

129

Table No. 4.44 Optimization of x value of (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-

sonic assisted mechanically stirred co-precipitation for the degradation of methylene

blue at pH = 9, 60mg/100ml catalyst dose and 50ppm initial dye concentration at room

temperature.

Time



20 15.36 0.68259 13.1047 0.50036 12.29 0.45637 11.6794 0.4153 9.51 0.35335

40 28.06 0.17296 22.952 0.43897 21.5 0.44172 19.99723 0.4108 16.99 0.20531

60 41.97 0.51941 35.856 0.62313 32.49 0.40699 28.92011 0.38664 25.34 0.44393

80 58.85 0.40962 49.6155 0.66515 43.45 0.29137 39.56453 0.28263 36.41 0.12334

100 67.84 0.3443 57.2352 0.15898 51.89 0.20372 43.5703 0.20168 39.12 0.31563

120 73.54 0.56324 64.9318 0.32714 55.52 0.53401 51.11538 0.46459 46.82 0.35328

140 73.97 0.50299 65.3489 0.19262 55.91 0.49088 51.44373 0.41725 47.18 0.37113

20 40 60 80 100 120 140

10

20

30

40

50

60

70

80

Degra

dation (

%)

Time (Min)

x = 0

x = 0.25

x = 0.50

x = 0.75

x = 1

Fig. 4.93 Optimization of x value of (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic

assisted mechanically stirred co-precipitation for the degradation of methylene blue at

pH = 9, 60mg/100ml catalyst dose and 50ppm initial dye concentration at room

temperature.

130

4.6 Reusability Test for (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3


Stability of photocatalysts is an important aspect in application of photocatalysts for

the removal of dyes or any other organic matter from waste water. Photocatalyst used for

longer time can reduce the cost of water treatment (Subash et al., 2013b; Tonda et al., 2014).

The most efficient photocatalysts (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3 were reused in

six cycles to check stability of these photocatalysts against all three dyes Methyl Orange

(MO), CI Reactive Black 5 (RB5) and Methylene Blue (MB) 3 mg photocatalyst was added

in each cycle to recover the loss of catalyst during separation and washing process (Shahid et

al., 2013). Photocatalyst was active efficiently in 6 cycles (Jiang et al., 2014). 5 – 7 % loss

of activity was observed. The results are shown in Table No. 4.45 and Fig. 4.93 & 4.94. It

can be concluded from the results that both catalysts can be reuse successfully for the

removal of dyes from waste water which can reduce the cost of waste water treatment.

Table No. 4.45 Reusability of (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3 in six cycles for

MO, RB5 and MB at optimum operational conditions.

Catalyst

Dye

% Degradation in 6 cycles

1 ±SD 2 ±SD 3 ±SD 4 ±SD 5 ±SD 6 ±SD

A MO 93.52 0.5684

92.78 0.4659

91.06 0.3125

90.25 0.2354

89.71 0.5236

88.96 0.3258

RB5 91.08 0.4556

90.26 0.6354

89.71 0.6624

87.05 0.4236

86.16 0.4965

84.87 0.5286

MB 83.74 0.5234

82.90 0.5648

82.14 0.5321

81.33 0.4587

80.24 0.4756

78.86 0.4523

B MO 78.38 0.4831

77.65 0.4287

76.63 0.2875

75.51 0.3166

75.02 0.4817

74.37 0.5997

RB5 83.21 0.4156 82.41 0.5337 81.85 0.4983 80.84 0.5165 80.24 0.4121 79.38 0.3878

MB 73.97 0.4397 73.15 0.4800 72.27 0.5234 71.69 0.4899 71.04 0.4042 70.54 0.4845

A = (Al2O3)0.75(ZnO)0.25Fe2O3

B = ZrO2.Fe2O3

MO = Methyl Orange

RB5 = CI Reactive Black 5

MB = Methylene Blue

131

MO RB5 MB0

20

40

60

80

100

120

Degra

da

tion (

%)

Cycle 1

Cycle 2

Cycle 3

Cycle 4

Cycle 5

Cycle 6

Fig. 4.93 Reusability of (Al2O3)0.75(ZnO)0.25Fe2O3 in six cycles for the degradation of

MO, RB5 and MB at optimum operational conditions.

MO RB5 MB0

20

40

60

80

100

120

De

gra

da

tio

n (

%)

Cycle 1

Cycle 2

Cycle 3

Cycle 4

Cycle 5

Cycle 6

Fig. 4.95 Reusability of ZrO2.Fe2O3 in six cycles for the degradation of MO, RB5 and

MB at optimum operational conditions.

132

4.7 Evaluation of Quality Assurance Parameters

4.7.1 Chemical Oxygen Demand (COD), Total Organic Carbon (TOC) analysis.

COD is the measurement of oxygen required for the oxidation of organic matter

present in a sample by strong chemical oxidant (Dan et al., 2000). TOC is the measure of

total organic matter present in sample (Thurman, 2012). To check the degradation efficiency

COD and TOC test was performed because TOC and COD values can show that during

photocatalytic process only chromophoric groups are break down to decolorize the dye

solution or other organic groups are break down into CO2 and H2O. The photocatalysts

(Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3 synthesized by ultra-sonic assisted co-precipitation

were used for this purpose because these catalysts showed maximum degradation efficiency.

This test was performed for all three dyes Methyl Orange (MO), CI Reactive Black 5 (RB5)

and Methylene Blue (MB). Values for degradation, decrease in COD and decrease in TOC

are given in table 4.46.

Table No. 4.46 Degradation, decrease in COD and decrease in TOC with

(Al2O3)0.75(ZnO)0.25Fe2O3 & ZrO2.Fe2O3

(Al2O3)0.75(ZnO)0.25Fe2O3

Dye Degradation

(%)

Decrease in COD

(%)

Decrease in TOC

(%)

MO 93.52 51.82 43.56

RB5 91.08 44.58 38.77

MB 83.74 54.92 47.88

ZrO2.Fe2O3

MO 78.38 42.78 35.87

RB5 83.21 37.25 32.55

MB 73.97 46.23 39.84

It can be observed from the results that percent decrease of COD and TOC was less

than degradation of dye in case of both photocatalysts and all three dyes. Reason for this

difference is that only chromophoric groups of dye molecules are break down which are

133

responsible for colors removal. Dye molecules converted into other color less organic

products like phenolic or other benzene ring containing compounds (Paul et al., 2011;

Sapawe et al., 2013)b.

20 40 60 80 100 1200

10

20

30

40

50

60

Decre

ase in C

OD

(%

)

Time (Min)

MO

RB5

MB

Fig 4.96 Decrease in COD of MO, RB5 and MB with (Al2O3)0.75(ZnO)0.25Fe2O3

20 40 60 80 100 1200

10

20

30

40

50

Decre

ase in C

OD

(%

)

Time (Min)

MO

RB5

MB

Fig 4.97 Decrease in COD of MO, RB5 and MB with ZrO2.Fe2O3

134

20 40 60 80 100 1200

10

20

30

40

50

Decre

ase in T

OC

(%

)

Time (Min)

MO

RB5

MB

Fig 4.98 Decrease in TOC of MO, RB5 and MB with (Al2O3)0.75(ZnO)0.25Fe2O3

20 40 60 80 100 1200

10

20

30

40

Decre

ase in T

OC

(%

)

Time (Min)

MO

RB5

MB

Fig 4.99 Decrease in TOC of MO, RB5 and MB with ZrO2.Fe2O3

135

4.7.2 Mineralization of dyes

Concentration of organic pollutant in any sample is indexed by TOC values. Degree

of mineralization of compound under study is indicated by TOC (Reddy et al., 2013). Long

time treatment upto 8 h was performed to get the maximum mineralization (Ullah et al.,

2013). It was done for all three dyes with (Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3.

Mineralization was increased with increasing time which indicated that organic carbon

present in sample was converted into carbon dioxide and water (Chen et al., 2004).

(Al2O3)0.75(ZnO)0.25Fe2O3 mineralize MO 80.45%, RB5 72.05% and MB 85.12% in 8 h time

of reaction at pH = 3, catalyst dose 60mg/100ml and initial dye concentration 50ppm at room

temperature. While ZrO2.Fe2O3 mineralize MO 69.42%, RB5 = 64.82 % and MB 74.28% in

8 at optimum conditions.

1 2 3 4 5 6 7 8 9

10

20

30

40

50

60

70

80

90

Decre

ase in T

OC

(%

)

Time (hour)

MO

RB5

MB

Fig. 4.100 Mineralization of MO,RB5 and MB with (Al2O3)0.75(ZnO)0.25Fe2O3 in 8 hours

136

1 2 3 4 5 6 7 8 9

10

20

30

40

50

60

70

80

Decre

ase

in

TO

C (

%)

Time (hour)

MO

RB5

MB

Fig. 4.101 Mineralization of MO, RB5 and MB with ZrO2.Fe2O3 25Fe2O3 in 8 hours

4.7.3 Total Suspended Solids (TSS)

Total suspended solids (TSS) is an important parameter to find the insoluble

quantities of pollutants in waste water specially disposed by the textile industries. Solid

particles in water can block the sun light which can affect the vegetation and cause rise in

temperature on surface (Mulligan et al., 2009). High TSS amounts can decrease the dissolved

oxygen level from normal level required for aquatic life and good quality of water. TSS

values are very high in waste water coming from textile industries as they use variety of

textile auxiliaries during processes. In this project we used dye solutions as synthetic

effluents, therefore TSS values were negligible or near to zero before treatment. But after

photocatalyst loading there was very small increase in TSS as 0.95mg/L, 1.13 mg/L and 1.10

mg/L for (Al2O3)0.75(ZnO)0.25Fe2O3 and 1.21mg/L, 1.26mg/L and 1.22mg/L for ZrO2.Fe2O3

with methyl orange, CI Reactive Black 5 and methylene blue respectively.

137

4.7.3 Haemolytic activity (Toxicity)

Toxicity of the sample can be estimated from the rate of haemolysis by applying different

concentrations of synthetic compounds on human erythrocytes (Sharma and Sharma, 2001).

Human red blood cell lysis was compared with samples after treatment containing Triton-

X100 1% as positive control it showed 100% lysis while Phosphate Buffer Saline (PBS) as

negative control showed 0% lysis. Results of treated samples were compared with these

controls. Haemolytic activity was performed for Methyl Orange (MO), CI Reactive Black 5

(RB5) and Methylene Blue (MB) solutions before and after treatment.

(Al2O3)0.75(ZnO)0.25Fe2O3 and ZrO2.Fe2O3 synthesized by ultra-sonic assisted mechanically

stirred co-precipitation were used for treatment. Results are shown in Fig. 4.102 for

(Al2O3)0.75(ZnO)0.25Fe2O3 and in Fig. 4.103 for ZrO2.Fe2O3. It can be observed from the

results that toxicity of treated samples was decreased by both catalysts. Decrease in toxicity

by (Al2O3)0.75(ZnO)0.25Fe2O3 was more than ZrO2.Fe2O3 for all three dyes.

PBS MO RB5 MB Triton X 100

0

20

40

60

80

100

RC

Bs L

ysis

(%

)

Before Treatment

After Treatment

Fig. 102 Toxicity assay of samples treated with (Al2O3)0.75(ZnO)0.25Fe2O3 and un-treated

samples.

138

PBS MO RB5 MB Triton X 100

0

20

40

60

80

100

RC

Bs L

ysis

(%

)

Before Treatment

After Treatment

Fig. 102 Toxicity assay of samples treated with (Al2O3)0.75(ZnO)0.25Fe2O3 and un-treated

samples.

139

CHAPTER-5

SUMMARY

Textile industrial effluents are playing a significant role in enhancing water pollution.

These effluents contain different chemicals especially synthetic dyes which are very difficult

to degrade by using the classical techniques. Evolution of a new branch of science known as

nano science has completely replaced the previously used classical technologies because

Nanomaterials completely mineralize most of organics and remove completely organic

matter from polluted water. Nanophotocatalyst are non-toxic, non-corrosive and stable

chemically and thermally.

In this study two types of novel metal oxides nanophotocatalysts were synthesized

with general formulas (Al2O3)1-x(ZnO)xFe2O3 and (ZrO2)1-x(ZnO)xFe2O3 where x = 0, 0.25,

0.50, 0.75 and 1. Co-precipitation via simple mechanical stirring and a newly developed

method co-precipitation via ultra-sonic assisted mechanical stirring were used for the

synthesis of both nanophotocatalyst. Samples were calcined at 400ᴼC and 600ᴼC to get

crystalline structures. Characterization of synthesized photocatalyst was done with X-Ray

Diffraction (XRD), Scanning Electron Microscopy (SEM), Energy Dispersive X-Ray

analysis (EDX), Particle size analysis and Surface analysis like Single Point surface area,

BET surface area and pore volume BJH adsorption and desorption pore volume.

Photocatalytic activity test was performed with three different dyes Methyl Orange (MO), CI

Reactive Black 5 (RB5) and Methylene Blue (MB) by optimizing the pH, photocatalyst dose

and initial dye concentration for both photocatalysts at room temperature.

X-Ray diffraction patterns showed that samples calcined at 600ᴼC are good

crystalline. In phase analysis more than one phase were detected in all samples. No specific

shape was seen in SEM images of most photo-catalytically active samples. EDX analysis was

also performed for highly efficient photocatalysts all components were detected in EDX

spectra of all samples at their relative energies. Particle sizes were calculated from XRD data

with help of Scherer’s formula and Zetasizer both results were matched with each other.

140

Particles with different sizes were detected in different samples ranging from 12 nm to 55

nm. Surface area was increased with decrease in particle size by ultra-sonic assisted

mechanically stirred co-precipitation.

Optimum pH was 3 for MO and RB5 while maximum degradation of MB was

occurred at pH 9. Catalyst dose was 60mg/100ml and optimum Initial dye concentration

was 50ppm for all three dyes with both catalysts. Co-precipitation via ultra-sonic assisted

mechanical stirring enhanced the photocatalytic activity of both photocatalysts by decreasing

particle size and increasing surface area of photocatalysts. (Al2O3)1-x(ZnO)xFe2O3 synthesized

by ultra-sonic assisted mechanically stirred co-precipitation with x=0.25 has maximum

degradation efficiency as it degraded MO 93.52%, RB5 91.08% and MB 83.74% while the

photocatalyst (ZrO2)1-x(ZnO)xFe2O3 synthesized by ultra-sonic assisted mechanically stirred

co-precipitation with x= 0 degraded the MO 78.38%, RB5 83.21% and MB 73.97% in 140

min. Therefore both are potential nanophotocatalysts for wastewater treatment.

141

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