SURENDRAN.G. Shri Sadhguru Jaggi Vasudev (Isha Foundation) and Shirdi Saibaba . ii Acknowledgement I

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Text of SURENDRAN.G. Shri Sadhguru Jaggi Vasudev (Isha Foundation) and Shirdi Saibaba . ii Acknowledgement I

  • Experimental Studies on Cr(VI) Removal from Wastewater by

    Adsorption using Pig Iron Sludge and Biochar


    Submitted in partial fulfilment

    of the requirements for the degree of




    Under the Supervision of

    Prof. Saroj Sundar Baral





  • i

    Dedicated to

    Shri Sadhguru Jaggi Vasudev (Isha Foundation)


    Shirdi Saibaba

  • ii


    I wish to record my sincere gratitude to Prof. Saroj Sundar Baral, my research supervisor,

    for his role in shaping my thought process. His knowledge, keen interest, constant

    encouragement, help, constructive criticism, endless patience and unstinting

    encouragement have contributed greatly to making this doctoral study a successful and

    enjoyable journey. I record my sincere gratitude to Prof. Srinivas Krishnaswamy & Prof.

    S.D. Manjare for their constant encouragement and advice as DAC members during the

    thesis work. Special thanks to Prof. Saibal Ganguly, Head, Department of Chemical

    Engineering, BITS Pilani- K. K. Birla Goa Campus for his encouragement and for

    sharing with me thoughts on matters beyond my imagination. I record my sincere

    gratitude to Prof. P. K. Das, Associate Dean, Academic Research Division, BITS Pilani-

    K. K. Birla Goa Campus, for helping in all administrative support during the research.

    I wish to offer my sincere thanks to Prof.G.Raghurama, Director, BITS Pilani- K. K.

    Birla Goa Campus, for his constant encouragement and support. I am grateful to Prof.

    Souvik Bhatacharya, Vice Chancellor, BITS Pilani, for granting me an opportunity to

    conduct research at this renowned institute and also for assuring the availability of

    necessary infrastructure and facilities to carry out my work. The role of my department

    colleagues in cheering me on and helping me face life with equanimity can never be

    overstated. All of them have provided more than their share of emotional support.

    My wife has been instrumental in motivating me from time to time. I am indebted to her

    for giving me a happy and joyous environment at home and for her silent sacrifices. I

    would forever be indebted to my parents, my brother and my uncle (S. Muthuvinayagam)

    for their constant love, confidence, prayers, strong support and good wishes. I owe it all

    to them.

    Surendran G.

  • iii


    The present study explores the use of easily available natural and industrial adsorbents

    for the treatment of Cr(VI) contaminated wastewater. In the initial part of the study,

    Cr(VI) adsorption studies have been carried out using two representative bio-sorbent viz

    Sorghastrum Nutans L. Nash and Cocos Nucifera. The effect of various parameters such

    as initial pH of adsorbate solution, initial concentration of Cr(VI), dosage, time and

    particle size has been studied. The adsorbent Sorghastrum Nutans L. Nash was

    characterized before and after adsorption using FTIR, SEM, EDAX, and XRD analysis.

    Among different functional groups present in the adsorbent, OH bending, CN

    stretching/bending and NH stretching plays a major role in Cr(VI) adsorption. Batch

    experiments shows that adsorption coupled reduction i.e. indirect reduction is the

    mechanism of Cr(VI) removal by the biomaterial. Adsorbent surface became highly

    positively charged at lower pH, adsorption rate of Cr(VI) is faster and reduction reaction

    also accelerates at lower pH since, the binding of negatively charged Cr(VI) ion species

    to the cationic groups is enhanced and protons take part in this reaction.

    In case of Sorghastrum Nutans L. Nash, it was observed that the adsorption capacity was

    high at pH 1 whereas, the adsorption capacity was very low at higher pH. In case of

    Cocos Nucifera, the adsorption capacity was significantly high at higher pH as compared

    to Sorghastrum Nutans L. Nash. However, in both the cases, the effluent pH was highly

    acidic and hence required further neutralization steps which may not be economical.

    Further, these adsorbents in their present form cannot be regenerated or recycled for

    industrial use. In addition, the water-soluble compounds present in the bio-sorbents can

    leach-out to the effluent which may create further environmental problem.

    To overcome the above problem, pig iron sludge is explored as an adsorbent for the

    treatment of Cr(VI) contaminated wastewater. From the batch adsorption experiments it

    was observed that, the uptake capacity of the adsorbent was low as compared to the bio-

    sorbent. Whereas, the effluent pH in case of using pig iron sludge was higher compared

    to the bio-sorbents. Further, this adsorbent in its present form can be recycled to

    ferrochrome manufacturing process.

  • iv

    Since the uptake capacity of the pig iron sludge is very less, biochar prepared from

    Sorghastrum Nutans L. Nash was used as an adsorbent. It was observed that the

    adsorption capacity of biochar is higher than other three adsorbents at higher solution pH.

    In addition, the effluent pH is also higher than the other three cases and the Cr(VI)

    adsorbed biochar can be recycled as a raw material to ferrochrome or steel manufacturing

    industry. In this study, a process flow sheet for ferrochrome industry is proposed showing

    the possible location of using the biochar. Adsorption kinetics, isotherms and rate

    limiting steps have been established for all the adsorbents used in this study. From the

    study, it was found that, adsorption process followed pseudo 2nd order kinetics and

    Langmuir adsorption isotherm and surface diffusion is the rate limiting step.

    To optimize the operating conditions, a full factorial design of experiment was used

    within pH, adsorbent dosage, adsorbate concentration and contact time as the

    independent variable and percentage of adsorption as the response variable. Empirical

    model was developed using factorial design of experiment and use of different tools like

    MINITAB, MATLAB and LabVIEW to simulate or analyze the empirical model. From

    the normal probability, residual, contour, 3D surface, main effect and interaction plot

    along with t test, ANOVA and F-test, it is observed that initial solution pH has the most

    significant effect on the percentage removal followed by adsorbent dosage, time and

    adsorbate concentration. The interaction effects of independent variables are evaluated

    and found to be significant.

    There is a requirement of easy, organized and rational methods to choose an adsorbent

    among the large options available by considering all possible factors and their interaction.

    In this study, fuzzy logic method is used for selection of a suitable adsorbent for the

    Cr(VI) removal. Multiple attribute decision making (MADM) is used to determine the

    corresponding weighting values for the selected adsorbent. The preference index is

    calculated by using the subjective and objective weights. The normalized value

    associated with each parameter has given on the basis of effect of each parameter on the

    Cr(VI) removal and uptake capacity of each material. The associated MADM method

    results and the limitations of the approaches are discussed to lay the foundation for

    further improvement.

  • v

    Table of Contents

    Acknowledgement ii

    Abstract iii

    Table of contents v

    List of figures x

    List of tables xii

    Chapter 1: Introduction and Literature Review 1-13

    1.1 Introduction 2

    1.2 Redox Reaction of Chromium 2 `

    1.3 Importance of harmful effects 3

    1.4 Sources of Chromium(VI) in Wastewater 3

    1.5 Chromium (VI) contaminated wastewater Treatment Technologies 5

    1.5.1 Chemical precipitation 5

    1.5.2 Chemical Reduction 7

    1.5.3 Photo catalysis 7

    1.5.4 Membrane Filtration 7

    1.5.5 Electro-dialysis 8

    1.5.6 Biopolymer 8

    1.5.7 Adsorption and Bio-adsorption 9

    1.5.8 Mechanism of bio-sorption 10

    1.5.9 Adsorption of chromium (VI) by industrial waste 10

    1.6 Conclusion 10

    Chapter 2: Bio-sorption of Cr(VI) from wastewater using Sorghastrum Nutans L.



    2.1 Materials 15

    2.2 Methods 15

    2.3 Results and Discussion 16

  • vi

    2.3.1. Characterizations 16

    2.3.2 Effect of Contact time on Cr(VI) adsorption 17

    2.3.3 Effects of pH on Cr(VI) adsorption 18

    2.3.4 Effect of Adsorbent dose 20

    2.3.5 Effects of Initial adsorbate concentration 20

    2.3.6 Effects of particle size on Cr(VI) adsorption 21

    2.4 Kinetic of adsorption 21

    2.4.1. Lagergren’ spseudo first-ordermodel 22

    2.4.2. Ritchie’s second order mod