Photodegradation of Methylene Blue by TiO2-Fe3O4-Bentonite

Research ArticlePhotodegradation of Methylene Blue by TiO2-Fe3O4-BentoniteMagnetic Nanocomposite

Wei Chen12 Hongyao Xiao12 Hang Xu12 Tonggang Ding12 and Yanmei Gu2

1Key Laboratory of Integrated Regulation and Resource Development on Shallow Lake of Ministry of EducationCollege of Environment Hohai University Nanjing 210098 China2College of Environmental Science Hohai University Nanjing 210098 China

Correspondence should be addressed to Hang Xu 23060096qqcom

Received 20 September 2014 Revised 9 January 2015 Accepted 12 January 2015

Academic Editor Yasser Shaban

Copyright copy 2015 Wei Chen et alThis is an open access article distributed under theCreativeCommonsAttribution License whichpermits unrestricted use distribution and reproduction in any medium provided the original work is properly cited

Fe3O4-bentonite nanoparticles have been prepared by a coprecipitation technique under a nitrogen atmosphere An aqueoussuspension of bentonite was first modified with FeCl

2and FeCl

3 TiO2was then loaded onto the surface of the Fe3O4-bentonite by

a sol-gel method After sufficient drying the colloidal solution was placed in a muffle furnace at 773K to obtain the TiO2-Fe3O4-bentonite composite The material has been characterized by scanning electron microscopy (SEM) X-ray diffraction (XRD)analysis and vibrating sample magnetometry (VSM) Morphological observation showed that Fe3O4 and TiO

2nanoparticles had

been adsorbed on the surface of bentonite nanoneedles The material was then applied for the photodegradation of the azo dyemethylene blue (MB) It was found that the removal efficiency of MB exceeded 90 under UV illumination and that only a20 mass loss was incurred after six cycles The composite material thus showed good photocatalytic performance and recyclingproperties

1 Introduction

Among environmental contaminants dyestuffs constitute amajor component and are of particular concern [1] Azo dyesarewidely applied in the printing and dyeing industries [2ndash4]Some azo dyes can be reduced to aromatic amines which arepotent carcinogens [5]Therefore they need to be completelyremoved from wastewater from printing and dyeing Due toits good catalytic effect stable chemical performance readyavailability and nontoxicity TiO

2has been regarded as an

ideal kind of catalyst since the 1940s [6] Under illuminationthe crystal surface of TiO

2generates electrons (eminus) and holes

(h+) allowing the production of reactive oxygen species(ROS) such as hydroxyl free radicals or oxygen free radicals[7 8] Such species react with the nitrogen double bondsin azo dyes and the dyes are thereby decomposed intonontoxic small-molecule chemicals [9] However pure TiO

2

is of limited use because of its low specific surface area andlow adsorption rate [10ndash13] Various catalyst supports havebeen applied for loading with TiO

2 Xia et al examined TiO

2

supported on layered double hydroxides that shows over 85removal rate of azo dyes [14] Janus et al loaded TiO

2on the

surface of powder activated carbon and used it to removeazo dyes [15ndash18] Xu et al synthesized a new compositematerial hydroxy-iron-aluminum pillared bentonite (H-Fe-Al-Ben) by ion exchange and studied its 995 removal rateof azocarmine B [19]

Due to their adsorption abilities and catalytic activitiesnatural clays have beenwidely used as adsorbents and catalystsupports Bentonite is a clay mineral the main component ofwhich ismontmorillonite [20 21]Due to its unique structurebentonite has good mechanical properties high thermalstability and acid and alkali resistance large surface areaand other favorable characteristics Hence it has been widelyused in adsorbents catalysts adhesives catalyst supportsand so on [22] Bentonite is abundant in China notablyin Wuxi Jiangsu and Zhejiang provinces [23] Researchershave modified the surface of bentonite to enhance its dis-persibility and selectivity Toor et al studied acid and ther-mal activation that leads to approximately 25 increase in

Hindawi Publishing CorporationInternational Journal of PhotoenergyVolume 2015 Article ID 591428 7 pageshttpdxdoiorg1011552015591428

2 International Journal of Photoenergy

the Congo-red adsorption capacity of natural bentonite [24]Li et al synthesized Fe-pillared bentonite and Al-Fe-pillaredbentonite and found that these composite materials wereeffective in removing azo dye X-3B [25] Liu et al found thatthe adsorption capacity of bentonite was greatly increasedby 9055 after interaction with attapulgite [26] Xu et alstudied that when ZnObentonite particles catalyst was usedthe removal rate of Acid Yellow 11 reached to 90 under UVirradiation which was remarkably effective [27]

In practice such adsorbents are difficult to recycle andare liable to cause secondary pollution and a waste ofresources [28] Iron oxide with the formula Fe

3O4 consists

of magnetic black crystals Its good magnetic properties areoften applied to modify materials allowing for improvedrecycling performance Pan et al studied the recovery per-formance of Fe

3O4-attapulgite used for the degradation of

24-dichlorophenol and found the mass loss of adsorbent tobe just 753 after five cycles [29] Wu et al used a solutioncopolymerization technique to synthesize a bentonite-Fe

3O4

PSA magnetic nanocomposite which proved that a smallamount of bentonite could improve the swelling ability forthe removal of Th(IV) [30]

Using bentonite as a catalyst support iron oxide forenhanced recovery performance and TiO

2for catalytic

decomposition we have prepared a TiO2-Fe3O4-bentonite

composite photocatalyst material by a simple combinedprecipitation-coating and sol-gel methodThis composite hasbeen investigated by SEM XRD and VSM

2 Materials and Methods

21 Materials Bentonite (average size 200mesh) was pur-chased from Oilbetter (China) FeCl

3sdot6H2O and FeSO

4sdot

7H2O were purchased from Sinopharm Chemical Reagent

Co (China) the latter was stored under a nitrogen atmo-sphere to avoid the oxidation of Fe(II) Azo dyes wereprocured from Dye Company (Dystar) The test solution wasprepared by dissolving azo dye (30mg) in distilled water(1 L) Methanol ethanol acetylacetone tetrabutyl titanateand sodium hydroxide were purchased from Sigma-AldrichCorporation All experiments were performed using deion-ized ultrapure water from an ultrapure water preparationdevice All reagents were of analytical grade purity and wereused directly without further purification

22 Preparation of the Catalyst

221 Pretreatment of Bentonite Bentonite clay powder (par-ticle size 0074mm) was finely sieved a 5 suspension inwater was prepared and this was allowed to age for 24 h Thebentonite powder was then recovered by centrifugation andplaced in an oven at 378K until it completely dehydrated Itwas kept dry until its subsequent loading with TiO

2

222 Loading of Bentonite with Fe3O4 Fe3O4-bentonite wasprepared by a coprecipitation method

Step 1 At 343K under nitrogen atmosphere bentonitepowder (10 g) was added to 200mL of aqueous solution

containing FeCl3sdot6H2O (50 g) and FeSO

4sdot7H2O (25 g)

Aqueous NaOH solution (10mL 8molL) was then addeddropwise to adjust the pH to 11 and the mixture was stirredcontinuously for 1 h

Step 2 The mixture was aged at 343K for 4 h The particleswere then washed with distilled water until neutral and driedin an oven at 373K for 3 h to afford Fe

3O4-bentonite crystals

223 Loading of Fe3O4-Bentonite with TiO2

Step 1 Fe3O4-bentonite (25 g) was placed in a beaker and

ethanol (80mL) was added The mixture was sonicated for20min and then left to stand

Step 2 Ethanol (80mL) and tetrabutyl titanate (20mL) weremixed in a beaker and sonicated for 20min Further ethanol(80mL) and aqueous nitric acid (obtained by diluting 10 mHNO

3(1mL) with distilled water (16mL)) were then added

to form a colloidal solution The mixture was vigorouslystirred for 30min and then left to stand for 24 h

Step 3Themixture was placed in an oven at 353K until com-pletely dry and then transferred to a muffle furnace andheated at 773K for 3 h to afford TiO

2-loaded magnetic

bentonite

23 Analytical Methods The crystal structure of the productwas determined on aThermoXrsquoTRA type X-ray diffractome-ter The crystal size and morphology of the samples wereexamined using a scanning electron microscope (HitachiLtd S-4800) The magnetic properties of the samples weredetermined using a vibrating sample magnetometer (VSM)(Lake Shore VSM7410)

24 Photocatalytic Reactions Experiments on the degrada-tion of methylene blue were performed to investigate thephotocatalytic effect of the TiO

2-Fe3O4-bentonite A 350W

xenon lamp equipped with a 288K constant temperaturecirculator was used TiO

2-Fe3O4-bentonite (30mg) and

30mgL methylene blue solution (100mL) were mixed for30min in a dark environment After the solution had reachedequilibrium it was placed in a batch stirrer for severalminutes under UV light irradiation Aliquots (2mL) of thesupernatant were withdrawn at intervals to measure themethylene blue concentration by UV spectrophotometry at awavelength of 664 nm No catalyst was added in a blank test

3 Results and Discussion

31 SEM Analysis of TiO2-Fe3O4-Bentonite Figure 1 showsthe XRD patterns of different samples From the figure it isevident that the modification of bentonite did not change itsstructure Comparing Figures 1(a) and 1(b) it can be seenthat the bentonite surface had been successfully loaded withFe3O4and TiO

2by the concerted precipitation-coating and

sol-gel method

International Journal of Photoenergy 3

10 20 30 40 50 60 70

Inte

nsity

(au

)

(a)

(b)

2120579 (∘)

Figure 1 XRD patterns of (a) bentonite (b) TiO2-Fe3O4-bentonite Bentonite 998779 Fe

3O4f TiO

2(rutile)

200 120583m

(a)

100 120583m

(b)

100 120583m

(c)

100 120583m

(d)

Figure 2 SEM images of (a) bentonite (b) Fe3O4-bentonite (c) TiO

2-bentonite and (d) TiO

2-Fe3O4-bentonite

Figure 2 shows SEM images of the samples Figure 2(a)shows a bentonite particle of diameter about 2-3 120583m When5 aqueous suspensions of bentonite were aged for 24 hthe surface area of the crystals was significantly increasedproviding a good surface for the loading of TiO

2and Fe

3O4

[31] FromFigures 2(a) and 2(b) it can be seen that the Fe3O4-

bentonite surface was more rough and that the crystal sizewas smaller after loading with Fe

3O4 Many Fe

3O4particles

were adsorbed on the bentonite surface Figure 2(c) showsa surface image of TiO

2-bentonite from which it is evident

that the bentonite particles had a good surface condition

for the loading of TiO2 Figure 2(d) shows that the crystal

surface morphology was not significantly changed when alarge number of TiO

2particles of diameter 10ndash20 nm were

adhered on the surface of the Fe3O4-bentonite

32 Magnetic Properties of TiO2-Fe3O4-Bentonite Figure 3shows themagnetic hysteresis loop of TiO

2-Fe3O4-bentonite

The magnetic properties of the composite were measured byvibrating samplemagnetometry (VSM) at room temperatureat magnetic field strengths in the range minus20 kOe leH le 20 kOe The magnetic saturation (Ms) residual


minus20000 20000100000minus10000

minus30

minus20

minus10

0

10

20

30

40

Mom

entm

ass (

emu

g)

Field (G)

Ms = 3329 emug

Figure 3 Magnetic hysteresis loop of TiO2-Fe3O4-bentonite at

298K

magnetization (Mr) coercivity (Hc) and MrMs ratio (Sr)of the composite were 3329 emug 087 emug 7973G and0026 respectively Low residual magnetism and coercivityshowed the sample to have ferromagnetic behavior atroom temperature Weak hysteresis attributed to a singlemagnetic domain of nanocrystalline nature was observedwhich indicates that TiO

2-Fe3O4-bentonite is a strongly

paramagnetic material The magnetism of Fe3O4

wasweakened after loading with TiO

2 but was still 3329 emug

so that it could be attracted by a commercial magnet Thusthe TiO

2-Fe3O4-bentonite composite can be recovered by

a simple magnetic separation technique greatly reducingsecondary pollution and the material cost of wastewatertreatment

33 Adsorption Kinetics of TiO2-Fe3O4-Bentonite TheLangmuir-Hinshelwood kinetic model is commonly usedto describe the photocatalytic degradation of organiccompoundsThe relationship between the reaction rate 119903 andthe concentration 119862 is expressed as follows

119903 = minus

119889119862

119889119905

=

119896

119903119870ad119862

1 + 119870ad119862 (1)

where 119896119903is the intrinsic rate constant and 119870ad is the adsorp-

tion equilibrium constant When the adsorption is weak orthe adsorbate concentration is low119870ad119862 is negligible and theadsorption kinetic equation can be simplified to a first-ordermodel

119903 = 119896

119903119870ad119862 = 119870app119862 (2)

where119870app is the apparent adsorption constantIn the initial condition (119905 = 0 119862 = 119862

0)

ln119862

0

119862

= 119870app119905 (3)

where 1198620and 119862 are the initial dye concentration and the

concentration at time 119905 respectively The values of 119870app can

00

05

10

15

20

T (min)0 20 40 60

ln(C

0C

t)

Figure 4 Pseudo-first-order kinetics for the degradation of methy-lene blue

Table 1 Pseudo-first-order kinetic parameters for the photodegra-dation of MB dye

Sample MB119870app [minminus1] 119905

12[min] 119877

2

TiO2-Fe3O4-bentonite 003236 214 09848

thus be calculated from regression analysis of the reactiontime 119905 and lnC

0119862

Figure 4 shows the linear relationship between ln1198620119862

and 119905 for the degradation of methylene blue at 298K asbefits the first-order adsorption model (linear correlationconstant gt 098) The apparent adsorption constant and 119905

12

value are shown inTable 1Thedegradation ofmethylene bluewas 90 complete after 90min of reaction Specifically therate of degradation of methylene blue adsorbed on the TiO

2-

Fe3O4-bentonite compositematerial was 00324minminus1 (119905

12=

214min) that is it was 50 degraded in just 214min Thissynthetic clay composite material thus showed considerablephotocatalytic degradation efficiency

34 The Photocatalytic Properties of TiO2-Fe3O4-BentoniteWe investigated the catalytic effects of bentonite Fe

3O4-

bentonite TiO2-bentonite and TiO

2-Fe3O4-bentonite on the

degradation of methylene blue under xenon lamp lightand the results are shown in Figure 5 It can be seen thatthe reaction almost reached completion after 90min withTiO2-bentonite and TiO

2-Fe3O4-bentonite the removal of

methylene blue was 90 complete after 90min Comparisonof these four adsorbents for the removal of methylene blueindicates that TiO

2-Fe3O4-bentonite is better than bentonite

The TiO2crystals loaded on the surface of bentonite are

mainly responsible for the decomposition of methylene blueStudies have indicated that azo dyes are first adsorbed andthen a surface-catalyzed reaction ensues which is favorablefor their removal From Figure 5 it is also evident that TiO

2-

Fe3O4-bentonite and TiO

2-bentonite removal rate shows

superior removal efficiency compared to Fe3O4-bentonite


0 8060402000

02

04

06

08

10

T (min)

PhotodegradationAdsorption phase

Ct

C0

TiO2Fe3O4ATTsTiO2 ATTs

Fe3O4ATTsATTs

Figure 5 Photocatalytic degradation of methylene blue by bentonite Fe3O4-bentonite TiO

2-bentonite and TiO

2-Fe3O4-bentonite under Xe

light

00

02

04

06

08

10

1 2 3 4 5 60

20

40

60

80

Rem

oval

rate

()

Run

Removal rateWtW0

Wt

W0

Figure 6 TiO2-Fe3O4-bentonite regeneration experiment

and bentonite and that the little difference between TiO2-


2-bentonite is led by little contribu-

tion of Fe3O4to photocatalytic removal efficiency

The regeneration performance of TiO2-Fe3O4-bentonite

was tested by carrying out six cycles of adsorption anddesorption The eluent consisted of methanol and acetic acid(95 05) After separating the catalyst from the aqueoussolution by means of a magnet at the end of each experimentthe catalyst was washed for 30min with 10mL of eluentunder ultrasonicationThe experimental results are shown inFigure 6 It can be seen that the mass loss of the compositematerial over the six cycles was only 20 The compositematerial retained its stable structure during the processindicating good regeneration properties

4 Conclusions

A TiO2-loaded magnetic clay composite material has been

synthesized by a simple ion coprecipitation and sol-gelmethod The catalyst has proved to be effective for theremoval of methylene blue under irradiation with a xenonlamp The absorption of methylene blue on the compositematerial showed pseudo-first-order kinetics with an adsorp-tion rate 119903 of 00324minminus1 In methylene blue degradationexperiments the removal efficiency of a 30mgL methyleneblue solution reached 90 after 90min at 298K and pH70 In addition the composite material incurred only 20mass loss after six cycles of repeated use which shows goodrecycling properties Therefore the described TiO

2-loaded

magnetic clay material showed not only good adsorption


decomposition performance for azo dyes under visible lightbut also excellent recycling properties It thus has greatpotential application in the azo dye treatment industry andis worthy of further study

Conflict of Interests

The authors declare that there is no conflict of interestsregarding the publication of this paper

Acknowledgments

This work was supported by the National Natural ScienceFoundation of China (51308185) National Innovation Train-ing Program (201310294024) and the open research fund ofthe Jiangsu Key laboratory of industrial water conservationabatement (IWCER201203)

References

[1] C E Bonancea G M do Nascimento M L de Souza M LA Temperini and P Corio ldquoSurface-enhanced Raman study ofelectrochemical and photocatalytic degradation of the azo dyeJanus Green Brdquo Applied Catalysis B Environmental vol 77 no3-4 pp 339ndash345 2008

[2] J-Y Park Y Hirata and K Hamada ldquoRelationship between thedyeadditive interaction and inkjet ink droplet formationrdquoDyesand Pigments vol 95 no 3 pp 502ndash511 2012

[3] D H Song H Y Yoo and J P Kim ldquoSynthesis of stilbene-basedazo dyes and application for dichroic materials in poly(vinylalcohol) polarizing filmsrdquo Dyes and Pigments vol 75 no 3 pp727ndash731 2007

[4] W Huang Y Li and H Lin ldquoColorimetric recognitionof acetate anions in aqueous solution using charge neutralazo derivativesrdquo Spectrochimica Acta Part A Molecular andBiomolecular Spectroscopy vol 86 pp 437ndash442 2012

[5] J Huang Y Liu Q Jin X Wang and J Yang ldquoAdsorptionstudies of a water soluble dye Reactive Red MF-3B usingsonication-surfactant-modified attapulgite clayrdquo Journal ofHazardous Materials vol 143 no 1-2 pp 541ndash548 2007

[6] M A Henderson ldquoA surface science perspective on TiO2

photocatalysisrdquo Surface Science Reports vol 66 no 6-7 pp 185ndash297 2011

[7] M Lucic N Milosavljevic M Radetic Z Saponjic MRadoicic and M K Krusic ldquoThe potential application ofTiO2hydrogel nanocomposite for removal of various textile azo

dyesrdquo Separation and Purification Technology vol 122 pp 206ndash216 2014

[8] M A Rauf M A Meetani and S Hisaindee ldquoAn overview onthe photocatalytic degradation of azo dyes in the presence ofTiO2doped with selective transition metalsrdquo Desalination vol

276 no 1ndash3 pp 13ndash27 2011[9] I Stambolova M Shipochka V Blaskov A Loukanov and

S Vassilev ldquoSprayed nanostructured TiO2films for efficient

photocatalytic degradation of textile azo dyerdquo Journal of Photo-chemistry and Photobiology B Biology vol 117 pp 19ndash26 2012

[10] J YanGWuNGuan andL Li ldquoNb2O5TiO2heterojunctions

synthesis strategy and photocatalytic activityrdquo Applied CatalysisB Environmental vol 152-153 no 1 pp 280ndash288 2014

[11] M Lei NWang L Zhu C Xie andH Tang ldquoA peculiar mech-anism for the photocatalytic reduction of decabromodiphenylether over reduced graphene oxide-TiO

2photocatalystrdquo Chem-

ical Engineering Journal vol 241 pp 207ndash215 2014[12] D Chen Y Du H Zhu and Y Deng ldquoSynthesis and characteri-

zation of amicrofibrousTiO2-CdSpalygorskite nanostructured

material with enhanced visible-light photocatalytic activityrdquoApplied Clay Science vol 87 pp 285ndash291 2014

[13] T Xu Y Liu F Ge and Y Ouyang ldquoSimulated solar lightphotooxidation of azocarmine B over hydroxyl iron-aluminumpillared bentonite using hydrogen peroxiderdquo Applied ClayScience vol 100 pp 35ndash42 2014

[14] S-J Xia F-X Liu Z-M Ni W Shi J-L Xue and P-P QianldquoTi-based layered double hydroxides efficient photocatalystsfor azo dyes degradation under visible lightrdquo Applied CatalysisB Environmental vol 144 pp 570ndash579 2014

[15] M Janus E Kusiak J Choina J Ziebro and A W MorawskildquoEnhanced adsorption of two azo dyes produced by carbonmodification of TiO

2rdquoDesalination vol 249 no 1 pp 359ndash363

2009[16] Y B Xie and X Z Li ldquoInteractive oxidation of photoelec-

trocatalysis and electro-Fenton for azo dye degradation usingTiO2-Ti mesh and reticulated vitreous carbon electrodesrdquo

Materials Chemistry and Physics vol 95 no 1 pp 39ndash50 2006[17] Z Zhang Y Xu X Ma et al ldquoMicrowave degradation of

methyl orange dye in aqueous solution in the presence of nano-TiO2-supported activated carbon (supported-TiO

2ACMW)rdquo

Journal of Hazardous Materials vol 209-210 pp 271ndash277 2012[18] J-H Sun Y-KWang R-X Sun and S-Y Dong ldquoPhotodegra-

dation of azo dye Congo Red from aqueous solution by theWO3-TiO2activated carbon (AC) photocatalyst under the UV

irradiationrdquoMaterials Chemistry and Physics vol 115 no 1 pp303ndash308 2009

[19] T Xu Y Liu F Ge L Liu and Y Ouyang ldquoApplication ofresponse surface methodology for optimization of azocarmineB removal by heterogeneous photo-Fenton process usinghydroxy-iron-aluminum pillared bentoniterdquo Applied SurfaceScience vol 280 pp 926ndash932 2013

[20] H Zaghouane-Boudiaf M Boutahala S Sahnoun C Tiar andF Gomri ldquoAdsorption characteristics isotherm kinetics anddiffusion of modified natural bentonite for removing the 245-trichlorophenolrdquo Applied Clay Science vol 90 pp 81ndash87 2014

[21] F Arbaoui and M N Boucherit ldquoComparison of two Algerianbentonites physico-chemical and retention capacity studyrdquoApplied Clay Science vol 91-92 pp 6ndash11 2014

[22] S S Al-Shahrani ldquoTreatment of wastewater contaminated withcobalt using Saudi activated bentoniterdquo Alexandria EngineeringJournal vol 53 no 1 pp 205ndash211 2014

[23] S Zheng and C A Aggelopoulos ldquoDeveloping status and trendon non-metallic minerals processing industry in Chinardquo ChinaNon-Metallic Mining Industry Herald pp 3ndash8 2006

[24] M Toor B Jin S Dai andVVimonses ldquoActivating natural ben-tonite as a cost-effective adsorbent for removal of Congo-redin wastewaterrdquo Journal of Industrial and Engineering Chemistryvol 21 pp 653ndash661 2015

[25] Y Li Y Lu and X Zhu ldquoPhoto-Fenton discoloration of the azodye X-3B over pillared bentonites containing ironrdquo Journal ofHazardous Materials vol 132 no 2-3 pp 196ndash201 2006

[26] Y Liu Y Kang B Mu and A Wang ldquoAttapulgitebentoniteinteractions for methylene blue adsorption characteristics fromaqueous solutionrdquo Chemical Engineering Journal vol 237 pp403ndash410 2014


[27] H Xu T Yu and J Liu ldquoPhoto-degradation of Acid Yellow 11 inaqueous on nano-ZnOBentonite under ultraviolet and visiblelight irradiationrdquoMaterials Letters vol 117 pp 263ndash265 2014

[28] W Zhong P Liu and A Wang ldquoFacile approach to magneticattapulgite-Fe

3O4 polystyrene tri-component nanocompositerdquo

Materials Letters vol 85 pp 11ndash13 2012[29] J Pan L Xu J Dai et al ldquoMagnetic molecularly imprinted

polymers based on attapulgiteFe3O4particles for the selective

recognition of 24-dichlorophenolrdquo Chemical Engineering Jour-nal vol 174 no 1 pp 68ndash75 2011

[30] L Wu Y Ye F Liu et al ldquoOrgano-bentonite-Fe3O4poly(sod-

ium acrylate) magnetic superabsorbent nanocomposite syn-thesis characterization and Thorium(IV) adsorptionrdquo AppliedClay Science vol 83-84 pp 405ndash414 2013

[31] C Zhu X Wang Q Huang et al ldquoRemoval of gaseous carbonbisulfide using dielectric barrier discharge plasmas combinedwith TiO

2coated attapulgite catalystrdquo Chemical Engineering

Journal vol 225 pp 567ndash573 2013

Submit your manuscripts athttpwwwhindawicom

Hindawi Publishing Corporationhttpwwwhindawicom Volume 2014

Inorganic ChemistryInternational Journal of

Hindawi Publishing Corporation httpwwwhindawicom Volume 2014

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International Journal of


Journal of

Chemistry


Advances in

Physical Chemistry

Hindawi Publishing Corporationhttpwwwhindawicom

Analytical Methods in Chemistry

Journal of

Volume 2014

Bioinorganic Chemistry and ApplicationsHindawi Publishing Corporationhttpwwwhindawicom Volume 2014

SpectroscopyInternational Journal of


The Scientific World JournalHindawi Publishing Corporation httpwwwhindawicom Volume 2014

Medicinal ChemistryInternational Journal of


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Applied ChemistryJournal of



Theoretical ChemistryJournal of


Journal of

Spectroscopy

Analytical ChemistryInternational Journal of


Journal of


Quantum Chemistry


Organic Chemistry International

ElectrochemistryInternational Journal of



CatalystsJournal of


the Congo-red adsorption capacity of natural bentonite [24]Li et al synthesized Fe-pillared bentonite and Al-Fe-pillaredbentonite and found that these composite materials wereeffective in removing azo dye X-3B [25] Liu et al found thatthe adsorption capacity of bentonite was greatly increasedby 9055 after interaction with attapulgite [26] Xu et alstudied that when ZnObentonite particles catalyst was usedthe removal rate of Acid Yellow 11 reached to 90 under UVirradiation which was remarkably effective [27]

In practice such adsorbents are difficult to recycle andare liable to cause secondary pollution and a waste ofresources [28] Iron oxide with the formula Fe

3O4 consists

of magnetic black crystals Its good magnetic properties areoften applied to modify materials allowing for improvedrecycling performance Pan et al studied the recovery per-formance of Fe

3O4-attapulgite used for the degradation of

24-dichlorophenol and found the mass loss of adsorbent tobe just 753 after five cycles [29] Wu et al used a solutioncopolymerization technique to synthesize a bentonite-Fe

3O4

PSA magnetic nanocomposite which proved that a smallamount of bentonite could improve the swelling ability forthe removal of Th(IV) [30]

Using bentonite as a catalyst support iron oxide forenhanced recovery performance and TiO

2for catalytic

decomposition we have prepared a TiO2-Fe3O4-bentonite

composite photocatalyst material by a simple combinedprecipitation-coating and sol-gel methodThis composite hasbeen investigated by SEM XRD and VSM

2 Materials and Methods

21 Materials Bentonite (average size 200mesh) was pur-chased from Oilbetter (China) FeCl

3sdot6H2O and FeSO

4sdot

7H2O were purchased from Sinopharm Chemical Reagent

Co (China) the latter was stored under a nitrogen atmo-sphere to avoid the oxidation of Fe(II) Azo dyes wereprocured from Dye Company (Dystar) The test solution wasprepared by dissolving azo dye (30mg) in distilled water(1 L) Methanol ethanol acetylacetone tetrabutyl titanateand sodium hydroxide were purchased from Sigma-AldrichCorporation All experiments were performed using deion-ized ultrapure water from an ultrapure water preparationdevice All reagents were of analytical grade purity and wereused directly without further purification

22 Preparation of the Catalyst

221 Pretreatment of Bentonite Bentonite clay powder (par-ticle size 0074mm) was finely sieved a 5 suspension inwater was prepared and this was allowed to age for 24 h Thebentonite powder was then recovered by centrifugation andplaced in an oven at 378K until it completely dehydrated Itwas kept dry until its subsequent loading with TiO

2

222 Loading of Bentonite with Fe3O4 Fe3O4-bentonite wasprepared by a coprecipitation method

Step 1 At 343K under nitrogen atmosphere bentonitepowder (10 g) was added to 200mL of aqueous solution

containing FeCl3sdot6H2O (50 g) and FeSO

4sdot7H2O (25 g)

Aqueous NaOH solution (10mL 8molL) was then addeddropwise to adjust the pH to 11 and the mixture was stirredcontinuously for 1 h

Step 2 The mixture was aged at 343K for 4 h The particleswere then washed with distilled water until neutral and driedin an oven at 373K for 3 h to afford Fe

3O4-bentonite crystals

223 Loading of Fe3O4-Bentonite with TiO2

Step 1 Fe3O4-bentonite (25 g) was placed in a beaker and

ethanol (80mL) was added The mixture was sonicated for20min and then left to stand

Step 2 Ethanol (80mL) and tetrabutyl titanate (20mL) weremixed in a beaker and sonicated for 20min Further ethanol(80mL) and aqueous nitric acid (obtained by diluting 10 mHNO

3(1mL) with distilled water (16mL)) were then added

to form a colloidal solution The mixture was vigorouslystirred for 30min and then left to stand for 24 h

Step 3Themixture was placed in an oven at 353K until com-pletely dry and then transferred to a muffle furnace andheated at 773K for 3 h to afford TiO

2-loaded magnetic

bentonite

23 Analytical Methods The crystal structure of the productwas determined on aThermoXrsquoTRA type X-ray diffractome-ter The crystal size and morphology of the samples wereexamined using a scanning electron microscope (HitachiLtd S-4800) The magnetic properties of the samples weredetermined using a vibrating sample magnetometer (VSM)(Lake Shore VSM7410)

24 Photocatalytic Reactions Experiments on the degrada-tion of methylene blue were performed to investigate thephotocatalytic effect of the TiO

2-Fe3O4-bentonite A 350W

xenon lamp equipped with a 288K constant temperaturecirculator was used TiO

2-Fe3O4-bentonite (30mg) and

30mgL methylene blue solution (100mL) were mixed for30min in a dark environment After the solution had reachedequilibrium it was placed in a batch stirrer for severalminutes under UV light irradiation Aliquots (2mL) of thesupernatant were withdrawn at intervals to measure themethylene blue concentration by UV spectrophotometry at awavelength of 664 nm No catalyst was added in a blank test

3 Results and Discussion

31 SEM Analysis of TiO2-Fe3O4-Bentonite Figure 1 showsthe XRD patterns of different samples From the figure it isevident that the modification of bentonite did not change itsstructure Comparing Figures 1(a) and 1(b) it can be seenthat the bentonite surface had been successfully loaded withFe3O4and TiO

2by the concerted precipitation-coating and

sol-gel method


10 20 30 40 50 60 70

Inte

nsity

(au

)

(a)

(b)

2120579 (∘)


3O4f TiO

2(rutile)

200 120583m

(a)

100 120583m

(b)

100 120583m

(c)

100 120583m

(d)



2-Fe3O4-bentonite


2and Fe

3O4



3O4 Many Fe

3O4particles









2-Fe3O4-bentonite



minus20000 20000100000minus10000

minus30

minus20

minus10

0

10

20

30

40

Mom

entm

ass (

emu

g)

Field (G)

Ms = 3329 emug


298K










119903 = minus

119889119862

119889119905

=

119896

119903119870ad119862

1 + 119870ad119862 (1)



119903 = 119896

119903119870ad119862 = 119870app119862 (2)


0)

ln119862

0

119862

= 119870app119905 (3)



00

05

10

15

20

T (min)0 20 40 60

ln(C

0C

t)




12[min] 119877

2



0119862



12


2-


12=



3O4-









2-





0 8060402000

02

04

06

08

10

T (min)


Ct

C0


Fe3O4ATTsATTs


2-bentonite and TiO


light

00

02

04

06

08

10

1 2 3 4 5 60

20

40

60

80

Rem

oval

rate

()

Run

Removal rateWtW0

Wt

W0








4 Conclusions



2-loaded






Acknowledgments


References





























2ACMW)rdquo

































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


10 20 30 40 50 60 70

Inte

nsity

(au

)

(a)

(b)

2120579 (∘)


3O4f TiO

2(rutile)

200 120583m

(a)

100 120583m

(b)

100 120583m

(c)

100 120583m

(d)



2-Fe3O4-bentonite


2and Fe

3O4



3O4 Many Fe

3O4particles









2-Fe3O4-bentonite



minus20000 20000100000minus10000

minus30

minus20

minus10

0

10

20

30

40

Mom

entm

ass (

emu

g)

Field (G)

Ms = 3329 emug


298K










119903 = minus

119889119862

119889119905

=

119896

119903119870ad119862

1 + 119870ad119862 (1)



119903 = 119896

119903119870ad119862 = 119870app119862 (2)


0)

ln119862

0

119862

= 119870app119905 (3)



00

05

10

15

20

T (min)0 20 40 60

ln(C

0C

t)




12[min] 119877

2



0119862



12


2-


12=



3O4-









2-





0 8060402000

02

04

06

08

10

T (min)


Ct

C0


Fe3O4ATTsATTs


2-bentonite and TiO


light

00

02

04

06

08

10

1 2 3 4 5 60

20

40

60

80

Rem

oval

rate

()

Run

Removal rateWtW0

Wt

W0








4 Conclusions



2-loaded






Acknowledgments


References





























2ACMW)rdquo

































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


minus20000 20000100000minus10000

minus30

minus20

minus10

0

10

20

30

40

Mom

entm

ass (

emu

g)

Field (G)

Ms = 3329 emug


298K










119903 = minus

119889119862

119889119905

=

119896

119903119870ad119862

1 + 119870ad119862 (1)



119903 = 119896

119903119870ad119862 = 119870app119862 (2)


0)

ln119862

0

119862

= 119870app119905 (3)



00

05

10

15

20

T (min)0 20 40 60

ln(C

0C

t)




12[min] 119877

2



0119862



12


2-


12=



3O4-









2-





0 8060402000

02

04

06

08

10

T (min)


Ct

C0


Fe3O4ATTsATTs


2-bentonite and TiO


light

00

02

04

06

08

10

1 2 3 4 5 60

20

40

60

80

Rem

oval

rate

()

Run

Removal rateWtW0

Wt

W0








4 Conclusions



2-loaded






Acknowledgments


References





























2ACMW)rdquo

































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of


0 8060402000

02

04

06

08

10

T (min)


Ct

C0


Fe3O4ATTsATTs


2-bentonite and TiO


light

00

02

04

06

08

10

1 2 3 4 5 60

20

40

60

80

Rem

oval

rate

()

Run

Removal rateWtW0

Wt

W0








4 Conclusions



2-loaded






Acknowledgments


References





























2ACMW)rdquo

































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of





Acknowledgments


References





























2ACMW)rdquo

































Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of






















Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of










Journal of

Chemistry


Advances in

Physical Chemistry



Journal of

Volume 2014














Journal of

Spectroscopy



Journal of


Quantum Chemistry






CatalystsJournal of

Documents

Photodegradation of Methylene Blue by TiO2-Fe3O4-Bentonite