Research Article Enhanced Photocatalytic Degradation of ...downloads.hindawi.com/archive/2013/356025.pdf · One step hydrothermal process is employed to produce ZnFe 2 O 4 and ZnFe

Hindawi Publishing CorporationIndian Journal of Materials ScienceVolume 2013 Article ID 356025 6 pageshttpdxdoiorg1011552013356025

Research ArticleEnhanced Photocatalytic Degradation of MethyleneBlue Using ZnFe2O4MWCNT Composite Synthesizedby Hydrothermal Method

Sonal Singhal1 Rimi Sharma1 Charanjit Singh1 and S Bansal2

1 Department of Chemistry Panjab University Chandigarh 160 014 India2Department of Science and Technology New Delhi India

Correspondence should be addressed to Sonal Singhal sonal1174gmailcom

Received 3 July 2013 Accepted 31 July 2013

Academic Editors W Cantwell D Das and W Gurnule

Copyright copy 2013 Sonal Singhal et al This is an open access article distributed under the Creative Commons Attribution Licensewhich permits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Multiwalled carbon nanotubes (MWCNTs) were synthesized using arc discharge method at a magnetic field of 430G andpurified using HNO

3H2O2 Transmission electron micrographs revealed that MWCNTs had inner and outer diameter of sim2 nm

and sim4 nm respectively Raman spectroscopy confirmed formation of MWCNTs showing G-band at 1577 cmminus1 ZnFe2O4and

ZnFe2O4MWCNTwere produced using one step hydrothermalmethod Powder X-ray diffraction (XRD) confirmed the formation

of cubic spinel ZnFe2O4as well as incorporation of MWCNT into ZnFe

2O4 Visible light photocatalytic degradation of methylene

blue (MB) was studied using pure ZnFe2O4and ZnFe

2O4MWCNT The results showed that ZnFe

2O4MWCNT composite had

higher photocatalytic activity as compared to pure ZnFe2O4 After irradiation for 5 hours in the visible light MB was almost

84 degraded in the presence of ZnFe2O4photocatalyst while 99 degradation was observed in case of ZnFe

2O4MWCNT

composite This enhancement in the photocatalytic activity of composite may be attributed to the inhibition of recombinationof photogenerated charge carriers

1 Introduction

Solar energy active photocatalysts have been a promisingmaterial for an environmental purification process Effortshave been made to synthesize materials capable of utilizingsolar spectrum for the photo degradation of industrial wastepollutants and dyes [1] Awide use of dyes as redox indicatorsbiological stains and pharmaceutical industries had adverseeffects on gastrointestinal genitourinary and cardiovascularsystem of human body [2 3] Degradation of organic pollu-tants and dyes such as methylene blue bromophenol blueand Chicago sky blue from industrial waste water remains asa challenge because of low visible light photo catalytic activityof metal oxides and sulphides [4ndash6] Large band gap of ZnSTiO2 SrTiO

3 and Ag

3VO4[7ndash9] prevents their functioning

as effective catalyst for visible light photo degradation [10]However the advantage of ferrites as photo catalysts

is their capability to absorb visible light solar irradiation

because of low band gap and large availability of catalytic sitesfor adsorption of noxious waste and dyes [11] Also ferritesare magnetic [12ndash15] in nature giving them added advantageof easy recovery after photocatalytic reaction

Albeit the numerous literature has been reported onthe photo degradation of different dyes using ZnFe

2O4as

catalyst having spinel structure where Zn2+ cations occupytetrahedral site and Fe3+ enters octahedral site [16]The bandgap of ZnFe

2O4is small (19 eV) due to which it utilizes

visible light to act as a photocatalyst [17] Fan et al [18]prepared nanocrystalline ZnFe

2O4by hydrothermal method

and investigated photodegradation of acid orange II azodye The authors observed better photocatalytic activity ascompared to bulk ZnFe

2O4sample prepared by conventional

solid state method The effect of sintering temperature onphotodegradation of methyl orange was studied by Jadhav etal [11] and observed maximum activity for samples sinteredat 500∘C Su et al [19] synthesized ZnFe

2O4by hydrothermal

2 Indian Journal of Materials Science

process and reported photodegradation of acid orange IIdye within 2 hours Li et al [20] synthesized spinel zincferrite nanospheres of 212 nm and noticed enhanced photocatalytic activity of the ZnFe

2O4nanospheres as compared to

ZnFe2O4nanoparticles in the decomposition of rhodamine

B However low quantum efficacy as a photo catalyst ofthe zinc ferrite has been improved by loading ZnFe

2O4

to titanium dioxide [10] Main drawback of ZnFe2O4TiO2

composite is that it can absorb onlyUV light in predominanceand only 50 of the dye degrades

Therefore the process of photo degradation requiresabsorption of visible light form solar or artificial sourcesFor the purpose of improving photo catalytic activity of theferrites and to efficiently utilize visible light a high aspectratio and tubular nanometric dimensions of multiwalled car-bon nanotubes (MWCNTs) make themselves a prospectivecandidate for photo catalytic activity [21 22] Decoration ofCNTs surface by foreign materials especially metal oxides[23] extends their field of application and improves theirchemical electrical mechanical and thermal properties thatcan be used in advanced nanotechnology [24] MagneticCNT composites have been found to be a potential alternatein future for materials with low photo catalytic activityDegradation of organic pollutants and toxic dyes has beenan important aspect to study the photo catalytic efficiency ofmagnetic CNT composites [25]

Thus our effort is to synthesize MWCNTs by arc dis-charge method This method is advantageous over otherpreviously reported methods because it is a low cost methodwhich gives completely aligned multiwalled carbon nan-otubes of high purity Further the surface of MWCNTs wasdecorated by ZnFe

2O4 This was envisaged so as to efficiently

design a green nanocomposite for the absorption of visiblelight from the spectrum One step hydrothermal processis employed to produce ZnFe

2O4and ZnFe

2O4MWCNTs

composite Combination of two semiconductors that isZnFe2O4and MWCNT would enhance the photo catalytic

activity Due to enhancement in photochemical activity ofZnFe2O4MWCNTs composite it is found to degrade almost

99 of the MB dye

2 Experimental

21 Synthesis of MWCNTs A metal-free arc dischargemethod was used to synthesize MWCNTs An arc excitationbetween the graphite rods submerged in the deionized waterwas carried out by applying an AC voltage of 50V to generate100A of currentThe schematic diagram for the same is givenin Figure 1 The electromagnets having soft iron core andcopper wire winding around the core serve the purpose forthe generation of 430 Gauss of magnetic field in a directionperpendicular to the arcing rods The gap between the interelectrodes was maintained at a separation of sim05mm forthe generation of arc A gap control screw unit was usedfor the movement of graphite electrodes Carbon soot wasproduced by discharging graphite electrodes for 1 hr andliquid turned black which was separated by decantationThisproduct formed was washed with de-ionized water 3-4 times

followed by refluxing with 8M aqueousHNO3for 24 hrsThe

sample was then refluxed again in 30H2O2as done by Feng

et al [26] for 24 hrs for further removal of impurities left pHwas then neutralized by washing the sample with de-ionizedwater The sample was air dried and annealed at 400∘C for 30minutes

22 Synthesis of ZnFe2O4MWCNT Nanocomposite A vari-

ety of methods are available to synthesize ferrites [27ndash31]but here ZnFe

2O4and ZnFe

2O4MWCNT were prepared by

hydrothermal process [32] The starting materials that isferric nitrate zinc nitrate and sodium hydroxide used forthe preparation were of analytical grade 10mmol of ferricnitrate and 5mmol of zinc nitratewere dissolved inminimumamount of water 10mg of prepared MWCNT was addedinto the solution and sonicated for 10 minutes The pH ofthe solution was set to 12-13 with the help of 6M sodiumhydroxideThemixture was vigorously stirred for 30 minutesand transferred into Teflon-lined stainless steel autoclaveThe autoclave was sealed and maintained at 180∘C for 12hoursThe product was allowed to cool to room temperaturefiltered andwashedwith distilled water followed by drying invacuum oven for 12 hours The same procedure was appliedwithout adding MWCNT to get pure ZnFe

2O4

23 Photocatalytic Activity The photocatalytic activity ofZnFe2O4and ZnFe

2O4MWCNT was evaluated by degra-

dation of aqueous solution of methylene blue (MB) undervisible light irradiation 50mg of catalyst was added to 50mLof 10mgL aqueous solution of MB Before illumination themixture was stirred in dark for 30min to achieve adsorptiondesorption equilibrium between catalyst and dye solutionThe solution was exposed to visible light under stirring afteraddition of 2mL of 30 H

2O2 At given time intervals 3mL

of aliquotswaswithdrawn and centrifuged to remove catalystThe concentration of methylene blue in aqueous solution wasdetermined with the help of UV-Vis spectrophotometer

24 Physical Measurements Transmission electron micro-graphs (TEM) were recorded using Hitachi (H7500) Trans-mission Electron microscope operated at 120 kV Ramandata were recorded using Invia Raman Microscope (Ren-ishaw) at room temperature with argon ion laser excitation514 nm (5mW power) over a range of 0ndash3200 cmminus1 X-raydiffractographs of the prepared samples were recorded usingan X-ray diffractometer (model PANalyticalrsquos Xrsquopert PROspectrophotometer) with Cu-K120572 radiation Photoirradiationwas carried out using 160W Hg lamp The concentration ofmethylene blue during the degradation was monitored byUV-visible spectrophotometer JASCO V-530

3 Results and Discussions

31 TEM Characterization The morphology of the MWC-NTswas studied using TEManalysisThe sample was agitatedultrasonically in ethanol for 20 minutes to avoid aggregation

Indian Journal of Materials Science 3

AC supply Transformer

60V

50V

40V

30V

Neutral

Variable V

200A

150A

100A

50A

Resistancecoil

Deionized water

Graphite rods

B

(B)

Spark

Rectifier

N

Magnetic field

DC+

DCminus

Figure 1 Schematic diagram of the arc discharge apparatus

of the sample Nanotubes thus obtained had inner and outerdiameter of sim2 nm and sim4 nmThe corresponding wall thick-ness of sim2 nm can be attributed to the formation of approx-imately seven walled CNTs (interlayer distances betweengraphene sheets being 033 nm) The TEM micrographs ofMWCNTs after refluxing using HNO

3H2O2are shown in

Figure 3 which indicated the formation of pure nanotubesCNTs obtained after purification has cleaner surface withoutany amorphous carbon impurities TEM image also revealedthat there is no effect on the shape and surfacemorphology ofMWCNTs Hence the obtained nanotubes were further usedfor the formation of nanocomposite

32 Raman Spectroscopy Raman spectroscopy revealedinvaluable insights into the purification of nanotubes G-band(1577 cmminus1) corresponded to the confirmation of MWCNTsDefect induced D-band (1355 cmminus1) was minimized afterpurifying CNTs with HNO

3H2O2for 24 hrs as shown in

Figure 4 D-band arises due presence of sp3 hybrid carbonwhereas G-band is due to existence sp2 hybrid carbon as inthe case of MWCNTs Intensity of D-Band is smaller when430 Gauss of magnetic field was generated perpendicularto arcing rods Occurrence of G-Band at 1581 cmminus1 alsoconfirmed that semiconducting MWCNTs were produced

[33] Large intensity of G1015840-Band at sim2700 cmminus1 indicatedthe reduction of amorphous carbon [34] These resultswere also supported by transmission electron microscopy(TEM) Decrease in the intensity of D-Band and increase inthe intensity of G1015840-Band clearly confirmed the removal ofamorphous carbon impurities and carbon lamellas from theMWCNT sample

33 X-Ray Diffraction Studies The phase composition ofall the synthesized samples was investigated using pow-der X-ray diffraction (XRD) technique XRD pattern ofZnFe2O4MWCNT nanocomposite pure ZnFe

2O4 and

MWCNT is presented in Figure 2 A strong diffraction peakat 2120579 = 26∘ can be indexed to (002) plane of MWCNT(Figure 2(a)) corresponding to the P6

3mmc space group

No peak corresponding to any other metal impurity wasobserved for purified sample The lattice parameters weredetermined using the Powley and Le Bail refinementmethodand the values of ldquoardquo and ldquocrdquo were 245gt and 675gt respec-tively corresponding to the hexagonal structure of graphite[35] The diffraction peaks of pure ZnFe

2O4(Figure 2(b))

confirmed formation of cubic spinel structure with Fd-3mspace group The peaks indexed to (220) (311) (400) (511)and (400) planes correspond to cubic spinel structure Thelattice parameter was calculated using the Powley refinementmethod and was found to be 846 A Based on the following


0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

12 20 30 40 50 60 70

(220

)

(511

)

(440

)

(400

)

(311

)

(002)

Relat

ive i

nten

sity

(a)

(b)

(c)

Angle 2120579

Figure 2 XRD patterns of (a) MWCNT (b) ZnFe2O4 and (c)

ZnFe2O4MWCNT

20nm

Figure 3 TEM image of MWCTs after purifying with HNO3

24 hrsH2O2 24 hrs

Debye-Scherrer relation [36] crystallite size was found to be10 nm

119889 =

09120582

120573 cos 120579 (1)

where 119889 is the diameter of the particle 120573 is the fullwidth of half maximum (FWHM) 120582 is the X-ray wave-length (1542gt) and 120579 is the angle of diffraction In caseof ZnFe

2O4MWCNT composite (Figure 2(c)) besides the

diffraction peaks of ZnFe2O4 a new peak at 2120579 = 26∘ was also

observed indicating coexistence of ZnFe2O4andMWCNT in

the composite However the intensity of the peak is low dueto addition of very small amount of MWCNT

0 500 1000 1500 2000 2500 30000

200

400

600

800

1000

Ram

an in

tens

ity (a

u)

Raman shift (cmminus1)

(D-1355)

(G-1577)

(G998400-2700)

Figure 4 Raman spectra of MWCNTs obtained after purificationwith HNO

3 24 hrsH

2O2 24 hrs

0

02

04

06

08

1

12

14

16

18

2

200 300 400 500 600 700 800Wavelength (nm)

Abso

rban

ce

0 hr

1 hr

2 hr

3 hr

4 hr

5 hr

Figure 5 Change in absorption with time in the presence ofZnFe2O4MWCNT

34 Photocatalytic Activity The photocatalytic activities ofZnFe2O4and ZnFe

2O4MWCNT nanocomposite were eval-

uated by degradation of methylene blue (MB) solutionFigure 5 shows degradation of MB in the presence ofZnFe2O4MWCNT nanocomposite under visible light irra-

diation The UV-visible spectra of MB solution show fourcharacteristic peaks at 246 292 617 and 663 nm Additionof H2O2masks peaks at 246 and 292 nm while the peaks at

617 and 663 nmregularly decrease in intensitywith increasingirradiation timeThe peak at 664 nm disappeared completelyin 5 hours indicating complete degradation (sim99) of MBdye The photocatalytic degradation was calculated by apply-ing following [37]

degradation = (119862

119900minus 119862

119905

119862

119900

) times 100 (2)

where 119862119900is initial MB concentration and 119862

119905is the concen-

tration of MB at time 119905 For comparison the degradation


0

10

20

30

40

50

60

70

80

90

100

0 05 1 15 2 25 3 35 4 45 5Irradiation time (hrs)

(a)

(b)

CC o

()

Figure 6 Effect of catalysts (a) ZnFe2O4MWCNTand (b) ZnFe

2O4

on decomposition of methylene blue

of MB was performed using pure ZnFe2O4 Photocatalytic

degradation efficiency of MB in the presence of ZnFe2O4and

ZnFe2O4MWCNT nanocomposite is shown in Figure 6 It

was observed that after irradiation for 5 hours about 84 ofMB was degraded in the presence of ZnFe

2O4photocatalyst

while 99 degradation was observed in case of compos-ite Therefore it can be concluded that ZnFe

2O4MWCNT

nanocomposite exhibits stronger photocatalytic activity ascompared to pure ferrite This may be due to strongerinteraction between ZnFe

2O4and MWCNT which inhibited

recombination of photogenerated charge carriers

4 Conclusion

An economical arc discharge method was used to synthesizemultiwalled carbon nanotubes Predominance of MWCNTshaving diameter of around 2ndash4 nm in the prepared sam-ple was clearly shown by TEM image Oxidizing agentHNO

3H2O2was used to purify the MWCNTs without

affecting the surface of nanotubes Raman spectra show thepeak intensity of D- and G1015840-bands which clearly revealed thepurity of as-synthesized carbon nanotubes Decrease in theintensity of defect induced D-band at 1350 cmminus1 and increasein the intensity of G1015840-band at 2700 cmminus1 indicating theremoval of amorphous carbon Further synthesis of ZnFe

2O4

and ZnFe2O4MWCNT composite was successfully carried

out using one step hydrothermal method Formation of com-posite was confirmed using XRDThe peaks indexed to (220)(311) (400) (511) and (400) planes correspond to cubic spinelstructure along with a very small peak of CNTs A compara-tive photocatalytic study of ZnFe

2O4and ZnFe

2O4MWCNT

nanocomposite clearly indicated the enhancement of pho-tocatalytic activity in ZnFe

2O4MWCNT nanohybrid MB

was almost 84 degraded in the presence of ZnFe2O4

photocatalyst while 99 degradation was observed in caseof ZnFe

2O4MWCNT composite after irradiation for 5 hours

in the visible light MWCNTs significantly enhance photo-catalytic activity of ZnFe

2O4as strong interaction between

ZnFe2O4and MWCNT inhibits recombination of photo

generated carriers

Acknowledgment

The authors are highly grateful to the Council of Scientificand Industrial Research (CSIR) for providing the necessaryfinancial support

References

[1] P Xiong Y Fu L Wang and X Wang ldquoMulti-walled carbonnanotubes supported nickel ferrite a magnetically recyclablephotocatalyst with high photocatalytic activity on degradationof phenolsrdquoChemical Engineering Journal vol 195-196 pp 149ndash157 2012

[2] B Mokhlesi J B Leikin P Murray and T C Corbridge ldquoAdulttoxicology in critical care part II specific poisoningsrdquoChest vol123 no 3 pp 897ndash922 2003

[3] J W Harvey and A S Keitt ldquoStudies of the efficacy andpotential hazards of methylene blue therapy in aniline-inducedmethaemoglobinaemiardquoBritish Journal ofHaematol vol 54 pp29ndash41 1982

[4] M A Gibson and JW Hightower ldquoOxidative dehydrogenationof butenes over magnesium ferrite kinetic and mechanisticstudiesrdquo Journal of Catalysis vol 41 no 3 pp 420ndash430 1976

[5] E Manova T Tsoncheva D Paneva I Mitov K Tenchev andL Petrov ldquoMechanochemically synthesized nano-dimensionaliron-cobalt spinel oxides as catalysts for methanol decomposi-tionrdquo Applied Catalysis A vol 277 no 1-2 pp 119ndash127 2004

[6] P Baldrian V Merhautova J Gabriel et al ldquoDecolorizationof synthetic dyes by hydrogen peroxide with heterogeneouscatalysis by mixed iron oxidesrdquo Applied Catalysis B vol 66 no3-4 pp 258ndash264 2006

[7] S Boumaza A Boudjemaa A Bouguelia R Bouarab and MTrari ldquoVisible light induced hydrogen evolution on new hetero-system ZnFe

2O4SrTiO

3rdquo Applied Energy vol 87 no 7 pp

2230ndash2236 2010[8] S XuW Shangguan J Yuan J Shi andM Chen ldquoPreparations

and photocatalytic degradation of methyl orange in water onmagnetically separable Bi

12TiO20

supported on nickel ferriterdquoScience and Technology of AdvancedMaterials vol 8 no 1-2 pp40ndash46 2007

[9] Y Yang Z Cao Y Jiang L Liu and Y Sun ldquoPhotoinducedstructural transformation of SrFeO

3and Ca

2Fe2O5during

photodegradation of methyl orangerdquo Materials Science andEngineering B vol 132 no 3 pp 311ndash314 2006

[10] B Zhang J Zhang and F Chen ldquoPreparation and character-ization of magnetic TiO

2ZnFe

2O4photocatalysts by a sol-gel

methodrdquo Research on Chemical Intermediates vol 34 no 4 pp375ndash380 2008

[11] S D Jadhav P P Hankare R P Patil and R Sasikala ldquoEffect ofsintering on photocatalytic degradation of methyl orange usingzinc ferriterdquoMaterials Letters vol 65 no 2 pp 371ndash373 2011

[12] X Liu and W Gao ldquoPreparation and magnetic properties ofNiFe2O4nanoparticles by modified pechini methodrdquoMaterials

and Manufacturing Processes vol 27 no 9 p 905 2012[13] M Drofenik M Kristl D Makovec Z Jaglicic and D Hanzel

ldquoPreparation and study of zinc ferrite nanoparticles with a highmagnetizationrdquoMaterials and Manufacturing Processes vol 23no 6 pp 603ndash606 2008


[14] H Xu andH Yang ldquoMagnetic properties of Y3Fe5O12nanopar-

ticles doped Bi and Ce ionsrdquo Materials and ManufacturingProcesses vol 23 no 1 pp 1ndash4 2008

[15] H Y He ldquoSynthesis and magnetic properties of Co05Zn05

Fe2O4nanoparticles by template-assisted combustion methodrdquo

Materials and Manufacturing Processes vol 27 no 9 p 9012012

[16] J P Singh GDixit R C SrivastavaHMAgrawal V R Reddyand A Gupta ldquoObservation of bulk like magnetic orderingbelow the blocking temperature in nanosized zinc ferriterdquoJournal of Magnetism and Magnetic Materials vol 324 no 16pp 2553ndash2559 2012

[17] X Li Y Hou Q ZhaoW Teng XHu andG Chen ldquoCapabilityof novel ZnFe

2O4nanotube arrays for visible-light induced

degradation of 4-chlorophenolrdquoChemosphere vol 82 no 4 pp581ndash586 2011

[18] G Fan Z Gu L Yang and F Li ldquoNanocrystalline zinc ferritephotocatalysts formed using the colloid mill and hydrothermaltechniquerdquo Chemical Engineering Journal vol 155 no 1-2 pp534ndash541 2009

[19] M Su C He V K Sharmab et al ldquoMesoporous zinc ferritesynthesis characterization and photocatalytic activity withH2O2visible lightrdquo Journal of HazardousMaterials vol 211-212

pp 95ndash103 2012[20] X Li Y Hou Q Zhao and L Wang ldquoA general one-

step and template-free synthesis of sphere-like zinc ferritenanostructures with enhanced photocatalytic activity for dyedegradationrdquo Journal of Colloid and Interface Science vol 358no 1 pp 102ndash108 2011

[21] J Salvetat A J Kulik J Bonard et al ldquoElastic modulusof ordered and disordered multiwalled carbon nanotubesrdquoAdvanced Materials vol 11 no 2 pp 161ndash165 1999

[22] W Oh and M Chen ldquoSynthesis and characterization ofCNTTiO

2composites thermally derived from MWCNT and

titanium(IV) n-butoxiderdquo Bulletin of the Korean ChemicalSociety vol 29 no 1 pp 159ndash164 2008

[23] X Wang Z Zhao J Qu Z Wang and J Qiu ldquoFabrication andcharacterization of magnetic Fe

3O4-CNT compositesrdquo Journal

of Physics and Chemistry of Solids vol 71 no 4 pp 673ndash6762010

[24] E W Wong P E Sheehan and C M Lieber ldquoNanobeammechanics elasticity strength and toughness of nanorods andnanotubesrdquo Science vol 277 no 5334 pp 1971ndash1975 1997

[25] W Wang P Serp P Kalck and J L Faria ldquoVisible light pho-todegradation of phenol on MWNT-TiO

2composite catalysts

prepared by a modified sol-gel methodrdquo Journal of MolecularCatalysis A vol 235 no 1-2 pp 194ndash199 2005

[26] Y Feng H Zhang Y Hou et al ldquoRoom temperature purifi-cation of few-walled carbon nanotubes with high yieldrdquo ACSNano vol 2 no 8 pp 1634ndash1638 2008

[27] J Chandradass D S Bae M Balasubramanian and K H KimldquoThe influence of oleic acid to metal nitrate ratio on the particlesize andmagnetic properties of lanthanum ferrite nanoparticlesby emulsion methodrdquo Materials and Manufacturing Processesvol 26 no 2 pp 230ndash235 2011

[28] L J Berchmans V Leena K Amalajyothi S Angappan and AVisuvasam ldquoPreparation of lanthanum ferrite substituted withMG and CArdquo Materials and Manufacturing Processes vol 24no 5 pp 546ndash549 2009

[29] G Chandrasekaran ldquoSpectroscopic study of autocombustionprocess in the synthesis of nano particles of Ni-Cu ferriterdquo

Materials and Manufacturing Processes vol 22 no 3 pp 366ndash369 2007

[30] Y H Guu K Tsai and L Chen ldquoAn experimental studyon electrical discharge machining of manganese-zinc ferritemagnetic materialrdquoMaterials andManufacturing Processes vol22 no 1 pp 66ndash70 2007

[31] H Jiang X Wang C Yu and L Wang ldquoMolten salt synthesisof Ni

05Zn05Fe2O4powdersrdquo Materials and Manufacturing

Processes vol 25 no 12 pp 1489ndash1493 2010[32] N Y Mostafa Z I Zaki and Z K Heiba ldquoStructural and

magnetic properties of cadmium substitutedmanganese ferritesprepared by hydrothermal routerdquo Journal of Magnetism andMagnetic Materials vol 329 pp 71ndash76 2013

[33] A C Ferrari ldquoRaman spectroscopy of graphene and graphitedisorder electron-phonon coupling doping and nonadiabaticeffectsrdquo Solid State Communications vol 143 no 1-2 pp 47ndash572007

[34] J Maultzsch S Reich C Thomsen et al ldquoRaman characteri-zation of boron-doped multiwalled carbon nanotubesrdquo AppliedPhysics Letters vol 81 no 14 pp 2647ndash2649 2002

[35] M C Schabel and J L Martins ldquoEnergetics of interplanarbinding in graphiterdquo Physical Review B vol 46 no 11 pp 7185ndash7188 1992

[36] A K M Akther Hossain and M L Rahman ldquoEnhancement ofmicrostructure and initial permeability due to Cu substitutionin Ni

050minus119909CuxZn

050Fe2O4ferritesrdquo Journal of Magnetism and

Magnetic Materials vol 323 no 15 pp 1954ndash1962 2011[37] M M Rashad R M Mohamed M A Ibrahim L F M Ismail

and E A Abdel-Aal ldquoMagnetic and catalytic properties ofcubic copper ferrite nanopowders synthesized from secondaryresourcesrdquo Advanced Powder Technology vol 23 no 3 pp 315ndash323 2012

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process and reported photodegradation of acid orange IIdye within 2 hours Li et al [20] synthesized spinel zincferrite nanospheres of 212 nm and noticed enhanced photocatalytic activity of the ZnFe

2O4nanospheres as compared to

ZnFe2O4nanoparticles in the decomposition of rhodamine

B However low quantum efficacy as a photo catalyst ofthe zinc ferrite has been improved by loading ZnFe

2O4

to titanium dioxide [10] Main drawback of ZnFe2O4TiO2

composite is that it can absorb onlyUV light in predominanceand only 50 of the dye degrades

Therefore the process of photo degradation requiresabsorption of visible light form solar or artificial sourcesFor the purpose of improving photo catalytic activity of theferrites and to efficiently utilize visible light a high aspectratio and tubular nanometric dimensions of multiwalled car-bon nanotubes (MWCNTs) make themselves a prospectivecandidate for photo catalytic activity [21 22] Decoration ofCNTs surface by foreign materials especially metal oxides[23] extends their field of application and improves theirchemical electrical mechanical and thermal properties thatcan be used in advanced nanotechnology [24] MagneticCNT composites have been found to be a potential alternatein future for materials with low photo catalytic activityDegradation of organic pollutants and toxic dyes has beenan important aspect to study the photo catalytic efficiency ofmagnetic CNT composites [25]

Thus our effort is to synthesize MWCNTs by arc dis-charge method This method is advantageous over otherpreviously reported methods because it is a low cost methodwhich gives completely aligned multiwalled carbon nan-otubes of high purity Further the surface of MWCNTs wasdecorated by ZnFe

2O4 This was envisaged so as to efficiently

design a green nanocomposite for the absorption of visiblelight from the spectrum One step hydrothermal processis employed to produce ZnFe

2O4and ZnFe

2O4MWCNTs

composite Combination of two semiconductors that isZnFe2O4and MWCNT would enhance the photo catalytic

activity Due to enhancement in photochemical activity ofZnFe2O4MWCNTs composite it is found to degrade almost

99 of the MB dye

2 Experimental

21 Synthesis of MWCNTs A metal-free arc dischargemethod was used to synthesize MWCNTs An arc excitationbetween the graphite rods submerged in the deionized waterwas carried out by applying an AC voltage of 50V to generate100A of currentThe schematic diagram for the same is givenin Figure 1 The electromagnets having soft iron core andcopper wire winding around the core serve the purpose forthe generation of 430 Gauss of magnetic field in a directionperpendicular to the arcing rods The gap between the interelectrodes was maintained at a separation of sim05mm forthe generation of arc A gap control screw unit was usedfor the movement of graphite electrodes Carbon soot wasproduced by discharging graphite electrodes for 1 hr andliquid turned black which was separated by decantationThisproduct formed was washed with de-ionized water 3-4 times

followed by refluxing with 8M aqueousHNO3for 24 hrsThe

sample was then refluxed again in 30H2O2as done by Feng

et al [26] for 24 hrs for further removal of impurities left pHwas then neutralized by washing the sample with de-ionizedwater The sample was air dried and annealed at 400∘C for 30minutes

22 Synthesis of ZnFe2O4MWCNT Nanocomposite A vari-

ety of methods are available to synthesize ferrites [27ndash31]but here ZnFe

2O4and ZnFe

2O4MWCNT were prepared by

hydrothermal process [32] The starting materials that isferric nitrate zinc nitrate and sodium hydroxide used forthe preparation were of analytical grade 10mmol of ferricnitrate and 5mmol of zinc nitratewere dissolved inminimumamount of water 10mg of prepared MWCNT was addedinto the solution and sonicated for 10 minutes The pH ofthe solution was set to 12-13 with the help of 6M sodiumhydroxideThemixture was vigorously stirred for 30 minutesand transferred into Teflon-lined stainless steel autoclaveThe autoclave was sealed and maintained at 180∘C for 12hoursThe product was allowed to cool to room temperaturefiltered andwashedwith distilled water followed by drying invacuum oven for 12 hours The same procedure was appliedwithout adding MWCNT to get pure ZnFe

2O4

23 Photocatalytic Activity The photocatalytic activity ofZnFe2O4and ZnFe

2O4MWCNT was evaluated by degra-

dation of aqueous solution of methylene blue (MB) undervisible light irradiation 50mg of catalyst was added to 50mLof 10mgL aqueous solution of MB Before illumination themixture was stirred in dark for 30min to achieve adsorptiondesorption equilibrium between catalyst and dye solutionThe solution was exposed to visible light under stirring afteraddition of 2mL of 30 H

2O2 At given time intervals 3mL

of aliquotswaswithdrawn and centrifuged to remove catalystThe concentration of methylene blue in aqueous solution wasdetermined with the help of UV-Vis spectrophotometer

24 Physical Measurements Transmission electron micro-graphs (TEM) were recorded using Hitachi (H7500) Trans-mission Electron microscope operated at 120 kV Ramandata were recorded using Invia Raman Microscope (Ren-ishaw) at room temperature with argon ion laser excitation514 nm (5mW power) over a range of 0ndash3200 cmminus1 X-raydiffractographs of the prepared samples were recorded usingan X-ray diffractometer (model PANalyticalrsquos Xrsquopert PROspectrophotometer) with Cu-K120572 radiation Photoirradiationwas carried out using 160W Hg lamp The concentration ofmethylene blue during the degradation was monitored byUV-visible spectrophotometer JASCO V-530

3 Results and Discussions

31 TEM Characterization The morphology of the MWC-NTswas studied using TEManalysisThe sample was agitatedultrasonically in ethanol for 20 minutes to avoid aggregation



60V

50V

40V

30V

Neutral

Variable V

200A

150A

100A

50A

Resistancecoil

Deionized water

Graphite rods

B

(B)

Spark

Rectifier

N

Magnetic field

DC+

DCminus



3H2O2are shown in







2O4 and


3mmc space group


2O4(Figure 2(b))



0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

12 20 30 40 50 60 70

(220

)

(511

)

(440

)

(400

)

(311

)

(002)

Relat

ive i

nten

sity

(a)

(b)

(c)

Angle 2120579


ZnFe2O4MWCNT

20nm


24 hrsH2O2 24 hrs


119889 =

09120582

120573 cos 120579 (1)






0 500 1000 1500 2000 2500 30000

200

400

600

800

1000

Ram

an in

tens

ity (a

u)


(D-1355)

(G-1577)

(G998400-2700)


3 24 hrsH

2O2 24 hrs

0

02

04

06

08

1

12

14

16

18

2

200 300 400 500 600 700 800Wavelength (nm)

Abso

rban

ce

0 hr

1 hr

2 hr

3 hr

4 hr

5 hr








119900minus 119862

119905

119862

119900

) times 100 (2)





0

10

20

30

40

50

60

70

80

90

100


(a)

(b)

CC o

()


2O4






2O4photocatalyst


2O4MWCNT




4 Conclusion




2O4



2O4and ZnFe

2O4MWCNT









generated carriers

Acknowledgment


References








2O4SrTiO




12TiO20



3and Ca

2Fe2O5during



2ZnFe














































050minus119909CuxZn











CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials





60V

50V

40V

30V

Neutral

Variable V

200A

150A

100A

50A

Resistancecoil

Deionized water

Graphite rods

B

(B)

Spark

Rectifier

N

Magnetic field

DC+

DCminus



3H2O2are shown in







2O4 and


3mmc space group


2O4(Figure 2(b))



0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

12 20 30 40 50 60 70

(220

)

(511

)

(440

)

(400

)

(311

)

(002)

Relat

ive i

nten

sity

(a)

(b)

(c)

Angle 2120579


ZnFe2O4MWCNT

20nm


24 hrsH2O2 24 hrs


119889 =

09120582

120573 cos 120579 (1)






0 500 1000 1500 2000 2500 30000

200

400

600

800

1000

Ram

an in

tens

ity (a

u)


(D-1355)

(G-1577)

(G998400-2700)


3 24 hrsH

2O2 24 hrs

0

02

04

06

08

1

12

14

16

18

2

200 300 400 500 600 700 800Wavelength (nm)

Abso

rban

ce

0 hr

1 hr

2 hr

3 hr

4 hr

5 hr








119900minus 119862

119905

119862

119900

) times 100 (2)





0

10

20

30

40

50

60

70

80

90

100


(a)

(b)

CC o

()


2O4






2O4photocatalyst


2O4MWCNT




4 Conclusion




2O4



2O4and ZnFe

2O4MWCNT









generated carriers

Acknowledgment


References








2O4SrTiO




12TiO20



3and Ca

2Fe2O5during



2ZnFe














































050minus119909CuxZn











CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

12 20 30 40 50 60 70

(220

)

(511

)

(440

)

(400

)

(311

)

(002)

Relat

ive i

nten

sity

(a)

(b)

(c)

Angle 2120579


ZnFe2O4MWCNT

20nm


24 hrsH2O2 24 hrs


119889 =

09120582

120573 cos 120579 (1)






0 500 1000 1500 2000 2500 30000

200

400

600

800

1000

Ram

an in

tens

ity (a

u)


(D-1355)

(G-1577)

(G998400-2700)


3 24 hrsH

2O2 24 hrs

0

02

04

06

08

1

12

14

16

18

2

200 300 400 500 600 700 800Wavelength (nm)

Abso

rban

ce

0 hr

1 hr

2 hr

3 hr

4 hr

5 hr








119900minus 119862

119905

119862

119900

) times 100 (2)





0

10

20

30

40

50

60

70

80

90

100


(a)

(b)

CC o

()


2O4






2O4photocatalyst


2O4MWCNT




4 Conclusion




2O4



2O4and ZnFe

2O4MWCNT









generated carriers

Acknowledgment


References








2O4SrTiO




12TiO20



3and Ca

2Fe2O5during



2ZnFe














































050minus119909CuxZn











CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials




0

10

20

30

40

50

60

70

80

90

100


(a)

(b)

CC o

()


2O4






2O4photocatalyst


2O4MWCNT




4 Conclusion




2O4



2O4and ZnFe

2O4MWCNT









generated carriers

Acknowledgment


References








2O4SrTiO




12TiO20



3and Ca

2Fe2O5during



2ZnFe














































050minus119909CuxZn











CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










































050minus119909CuxZn











CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials










CeramicsJournal of







Biomaterials




Journal of


Journal of





CoatingsJournal of

Advances in








MaterialsJournal of


Nano

materials



Documents

Research Article Enhanced Photocatalytic Degradation of ...downloads.hindawi.com/archive/2013/356025.pdf · One step hydrothermal process is employed to produce ZnFe 2 O 4 and ZnFe