Composites of TiO2-aluminum pillared montmorillonite_ Synthesis, characterization

NoteComposites of TiO 2-aluminum pillared montmorillonite:Synthesis,characterization and photocatalytic degradation of methylene blueIs Fatimah a ,c ,⁎,Shaobin Wang b ,Narsito c ,Karna Wijaya ca Chemistry Department,Universitas Islam Indonesia,Yogyakarta,55581,Indonesiab Department of Chemical Engineering,Curtin University of Technology,GPO Box U1987,Perth,WA 6845,Australia cChemistry Department,Gadjah Mada University,Yogyakarta,Indonesiaa b s t r a c ta r t i c l e i n f o Article history:Received 20October 2009Received in revised form 7August 2010Accepted 21August 2010Available online 20October 2010Keywords:Pillared montmorillonite Photocatalyst Titania DyesAluminum pillared montmorillonite was prepared and used as a porous support for synthesis of TiO 2-based photocatalysts with varying TiO 2loading.The physicochemical properties of the TiO 2-pillared montmorillonite samples were characterized by X-ray diffraction,N 2adsorption isotherm,UV –visible diffuse re flectance spectroscopy,scanning electron microscopy and transmission electron microscopy.Photocatalytic activity of the materials was evaluated by methylene blue photodegradation in aqueous solution.The titania content in the composites signi ficantly in fluenced the physicochemical properties and catalytic activity.High TiO 2loading in the composite produced crystalline TiO 2and enhanced dye degradation.©2010Elsevier B.V.All rights reserved.1.IntroductionTitania (TiO 2)is a well known material in photocatalysis.As a semiconductor with wide band gap energy and nontoxicity,it is widely used for photocatalytic decomposition of various organic compounds in wastewater treatment (Rajeshwar et al.,2008;Fujishima et al.,2000,2007,2008).However,the use of titania in bulk form suffers from catalyst recovery and activity reduction,which results in ineffective application of the catalyst.In some cases,fine titania particles could also block the penetration of light into the solution.To overcome the limitations,several approaches were proposed e.g.attaching titania particles onto stable inorganic supports (Mahmoudi and Arami,2009;Reddy et al.,2003;Fukahora et al.,2003;Hisanaga and Tanaka,2002;Zhang et al.,1998;Li et al.,2008;Rao et al.,2003).In principle,inorganic materials with high speci fic surface area and chemical stability can be used as host matrix.Natural porous materials such as zeolites and clay minerals are also good and cheaper supports with eco-friendly properties.Clay minerals possess high porosity,exchangeable cations and swellable properties.Previously,several investigators reported the preparation of titania immobilization on clay minerals via pillarization processes.During the preparation,titania was incorporated in the interlayer space of the clay through an intercalation step of pillaring precursors via ionic species followed by calcination to convert the titanium hydroxide to oxide.However,highly acidic environment oftitanium pillaring precursor damages the structure of clay minerals (Yuan et al.,2006;Kooli et al.,1997;Bergaya et al.,2006).As a result,the low crystallinity of supported titania would have a reduced activity in heterogeneous catalysis.In addition,the preparation was not reproducible (Romero et al.,2006).Recently,some investigations reported the synthesis of supported TiO 2or TiO 2composites as catalysts (An et al.,2008;Belessi et al.,2007;Daniel et al.,2007,2008Menesi et al.,2008).Several metals i.e.Al,Zr and Fe were used as pillaring precursors for preparation of pillared clay minerals with higher thermal stability and speci fic surface area.Among them,poly(hydroxo)aluminum pillars were intensively studied due to easy Keggin ion formation.The enhanced speci fic surface area,porosity and thermal stability made these pillared clay minerals as good host matrices.Recently,several reports also showed that aluminum pillared clay minerals can host metal and metal oxide catalysts (Gil et al.,2000,2008;Vicente et al.,2004).In the present study,we report the preparation of an aluminum pillared Indonesian montmorillonite and its use as a support for titania immobilization.These photocatalysts were characterized by several techniques and tested for photodegradation of methylene blue.2.Materials and methods 2.1.Preparation of materialsAlCl 3⋅6H 2O,NaOH,and isopropanol were supplied by Merck and titanium isopropoxide (TTIP)was obtained from Sigma-Aldrich.TheApplied Clay Science 50(2010)588–593⁎Corresponding author.Chemistry Department,Universitas Islam Indonesia,Yogyakarta,55581,Indonesia.Tel.:+62818273001;fax:+62274895920.E-mail address:isfatimah@fmipa.uii.ac.id (I.Fatimah).0169-1317/$–see front matter ©2010Elsevier B.V.All rights reserved.doi:10.1016/j.clay.2010.08.016Contents lists available at ScienceDirectApplied Clay Sciencej o u r n a l h o me p a g e :w w w.e l sev i e r.c om /l o c a t e /c l aysynthesis of aluminum pillared montmorillonite consisted of (i)pre-paration of Keggin ion Al 13solution,(ii)Keggin ion intercalation and neutralization,and (iii)calcination at 500°C.The Keggin ion (Al 13)solution was prepared by slow titration of AlCl 3⋅6H 2O solution with a NaOH solution under vigorously stirring until the ratio of OH −/Al=2.2was reached.The intercalation process was then conducted by dropping this solution into a montmorillonite dispersion at a ratio of 5.0mmol Al/g of montmorillonite without any aging process and calcination at 500°C for 4h.The obtained aluminum pillared montmorillonite was denoted as PILM.Titania/PILM composites were prepared by an impregnation procedure using titanium tetraisopropoxide (TTIP).Firstly,TTIP was diluted with isopropanol to obtain a clear solution of varying Ti concentrations.This solution was slowly added to aluminum pillared montmorillonite dispersion with constant stirring of 6h at room temperature.The solvent was evaporated at 30°C under vacuum.The solid material was dried at 120°C for 6h,and then calcined at 450°C for 4h (TiO 2/PILM).TiO 2with various Ti loading of 0.2,0.6,1.0,3.0,10.0and 20mass%was prepared.The catalysts were referred as Ti-N/PILM where N indicates the Ti content.2.2.Characterization of support and catalystsA gas sorption analyzer (NOVA 1200e)was used to determine the nitrogen adsorption isotherms at −196°C.The surface area was calculated by the BET equation.A Shimadzu X 6000powder diffractometer with Cu-K αradiation was used to obtain X-ray powder diffraction (XRD)patterns.The titanium content was determined by X-ray fluorescence spectroscopy (XRF).The morphology of materials was observed by scanning electron microscopy (SEM JEOL 820)and transmission electron microscopy (TEM JEOL-JEM,120kV).UV –vis diffuse re flectance spectra were obtained at 25°C on a JASCO UNIDEC model V670spectrometer equipped with an integrating sphere,where a BaSO 4plate was used as a reference.The chemical contents of the prepared materials were measured by XRF and EDX.2.3.Photocatalytic activity testThe photocatalytic activity evaluation of TiO 2/PILM materials was carried out in a batch photoreactor.The reactor was made of a Pyrex glass beaker surrounded by a water jacket and four UV tube lamps (UVB lamp,10W).Methylene blue solution (MB)was prepared at the concentration of 5×10−5M and a volume of 500mL solution was used for reaction.In each run,catalyst content was 1g/L.The concentration of methylene blue during the reaction was determined by photometryTable 1Elemental analysis of material.SampleComponent (wt.%)SiO 2Al 2O 3Na 2O CaO FeO MgO TiO 2Montmorillonite 56.4021.628.250.58 3.58 3.39–PILM51.5237.33 2.520.310.89 1.84–Ti-0.2/PILM 54.2334.34 2.320.090.87 1.310.45Ti-0.6/PILM 51.2937.98 1.820.090.22 1.23 1.27Ti-1.0/PILM 51.6536.11 1.830.090.12 1.3 2.38Ti-3.0/PILM 50.0433.08 1.830.090.33 1.02 6.64Ti-10.0/PILM 45.3827.27 1.10.070.19 1.1218.24Ti-20.0/PILM35.3121.961.10.041.070.9933.46Fig.1.Corelation between Ti content in impregnation solution andcatalysts.Fig.2.XRD pattern of support and catalyst materials (m,Cr,q,A and R represent montmorillonite,crystoballite,quartz,anatase and rutile,respectively).589I.Fatimah et al./Applied Clay Science 50(2010)588–593at 630nm using a UV –visible spectrophotometer (HITACHI-U 2080)and further con firmed by HPLC (Shimadzu E-1003).3.Results and discussion 3.1.Catalyst characterizationTable 1presents the chemical composition determined by ele-mental analysis using EDX and XRF.XRF was used to determine Ti content in the samples and EDX was used to analyze other metalcontents.SiO 2and Al 2O 3were the main components of the mineral support and catalysts.Na content in the minerals was higher than Ca,which suggests that the mineral was sodium montmorillonite.For montmorillonite and PILM,no TiO 2was detected.The loading of TiO 2was 0.5–33.5mass%.Fig.1shows the rela-tionship of TiO 2concentration in preparation solution and actual loading of PILM with TiO 2.The good linear correlation suggests that impregnation of TiO 2on PILM was ef ficiently achieved and no sig-ni ficant TiO 2loss occurred during the preparation.The XRD patterns of montmorillonite showed the characteristic re flections at 2θ=6.3°(d 001=14.9Å)and 2θ=19.9°(d =4.5Å).Other re flections at 21.8°and 26.6°indicated crystoballite and quartz (Fig.2).The XRD pattern of PILM was similar to that of montmorillonite but with a different intensity of the re flections.The (001)re flection indicated a basal spacing of 19.5.Re flections of titania on TiO 2/PILM were not observed when the Ti content was 0.2to 0.6mass%.The position and the intensity of the (001)re flection were not affected.The titania phase was identi fied when its content was N 1.0mass%.At 2θ25.1°,37.7°,and 53.8°the (101),(004)and (105)re flections of tetragonal titania (anatase)were observed.With increasing titania content the (101)re flection of rutile at 27°was found.Titania crystallization at high loading was also observed in the preparation of nanoparticle titania membranes and titania incorpo-ration in gels reported in previous studies (Mogyor όsi et al.,2003),where both anatase and rutile forms were produced.In the pillared montmorillonite anatase was generally formed or sometimes no re flections of titania were found (Gil et al.,2000;Rezala et al.,2009;Ding et al.,2008;Binitha and Sugunan,2006;Bovey et al.,1996).Thus,titania crystallized only at higher TiO 2content while very small TiO 2aggregates were homogeneously dispersed at small particle size on clay mineral surface at low TiO 2concentration.The hydrolysis rate of titanium isopropoxide may affect the titania crystallization in the PILM.At high TTIP concentration,titanium would be fast deposited in gel form before it reached the PILM pores (Dhage et al.,2004).Due to the gel form with larger molecular size,titanium isopropoxide was dif ficult to penetrate into the pores of PILM and the condition would favor the formation of both anatase and rutile during the crystallization process.UV –visible diffuse re flectance spectra revealed the existence of smaller titania particles in the pillared montmorillonite matrix (Fig.3).The spectra showed the blue shift in all TiO 2/PILM samples compared to pure TiO 2spectrum.The edge wavelength of the TiO 2/PILM samples increased with increasing titanium content inPILMFig.3.UV –visible diffuse re flection spectra of TiO 2/PILM.Table 2Edge wavelengths of materials.Sample Edge wavelength (nm)Titania (Merck)380.9Ti-0.2/PILM 336.8Ti-0.6/PILM 338.7Ti-1.0/PILM 348.5Ti-3.0/PILM 348.6Ti-10.0/PILM 380.9Ti-20.0/PILM380.9Fig.4.Nitrogen adsorption –desorption isotherm on support and catalyst materials.590I.Fatimah et al./Applied Clay Science 50(2010)588–593(Table 2).At a high concentration of TiO 2,there was no difference in the edge wavelength between the bulk TiO 2and TiO 2/PILM.A similar observation was reported for TiO 2/ZSM5(Zhang et al.,1998).For the TiO 2/PILM samples with Ti loading between 0.2and 3.0mass%,there was no signi ficant change in the value of band gap energy.The values of the edge wavelengths indicated the formation of smaller titania particles.At higher Ti content i.e.10and 20mass%,the edge wavelength values were similar to TiO 2.The XRD pro files also clearly showed the presence of titania crystals on the surface.For TiO 2on ZSM5,the edge wavelength was also not signi ficantly different from bulk TiO 2(Reddy et al.,2003).At Ti content of 0.2–1.0mass%,the speci fic surface area decreased with increasing titanium content,at high Ti content,the speci fic surface area increased again (Fig.4,Table 3).The adsorption –desorption isotherm indicated that TiO 2/PILM was mesoporous at Ti loading of 0.2to 1.0mass%and micropores were formed at higher titanium contents.The BJH pore size distribution (Fig.5)showed a change of pore size at varying Ti loading.At higher Ti loading,micro-pores were developed.Without Ti impregnation,PILM has a peak of larger pore size between 4and 8nm.At Ti loading of 0.2mass%,no such pore peak occurred,due to packing of small TiO 2particles on the surface and pores,resulting in the reduction in speci fic surface area.When more Ti (N 3mass%)was loaded on PILM,the TiO 2aggregates could also form porous structure but with micropores.The developed micropores would enhance the speci fic surface area of TiO 2/PILM.The SEM images of TiO 2/PILM (Fig.6)showed the layered structure of PILM.The surface morphology of Ti-0.2/PILM was not signi ficantly different from the PILM,but abundant titania particles on the surface of Ti-3.0/PILM and Ti-20.0/PILM were observed.The increase of the speci fic surface area due to the formation of titania particles was also shown by TEM images (Fig.7).Large aggre-gates of titania particles were observed for Ti-3.0/PILM.Similar results were reported for titania-pillared montmorillonite (Yoda et al.,2004).Table 3Result of adsorption –desorption measurement.Sample Speci fic surface area (m 2/g)Micropore surface area (m 2/g)Pore volume ×10−1(cm 3/g)PILM 157.834.50.754Ti 0.292.928.80.651Ti0.675.453.60.847Ti 1.066.654.8 1.452Ti 3.0128.687.30.996Ti 10.0133.494.8 1.309Ti20.0187.8116.01.518Fig.5.Pore size distribution of PILM and TiO 2/PILMcomposites.Fig.6.SEM images of support and catalysts.(a)PILM,(b)Ti-0.2/PILM,(c)Ti-3.0/PILM and (d)Ti-20.0/PILM.591I.Fatimah et al./Applied Clay Science 50(2010)588–5933.2.Photodegradation of methylene blue (MB)The photocatalytic activity of various TiO 2/PILM catalysts in MB photodegradation is presented in Fig.8.From the variation of MBconcentration with time,the degradation kinetics was derived and the first order model (Eq.(1))was found to fit the curves.ln MB ½ =−kt +ln MB ½ 0ð1Þwhere,[MB]and [MB]0are MB concentration in sampling time (t )and initial concentration at t =0,respectively,and k is the kinetic rate constant of the first order reaction.Based on the equation,the degradation rate constants (k )were obtained and are presented in Table 4with equilibrium concentration of MB.PILM showed the lowest degradation rate of MB and its adsorption capacity was also low (b 10%).The TiO 2/PILM samples exhibited varying activity depending on TiO 2loading.The catalytic activity followed the order Ti-20.0/PILM N Ti-10.0/PILM N Ti-3.0/PILM NTi-0.6/Fig.7.TEM pro file of (a)PILM,(b)Ti-1.0/PILM and (c)Ti-3.0/PILM.Fig.8.Kinetic variation of MB photodegradation on various photocatalysts.Table 4Constant of MB degradation rate and concentration in equillibrium.Photocatalyst K (10−3/min)C e (10−5M)PILM 0.826 4.355Ti 0.2 3.327 3.085Ti0.6 3.313 3.215Ti 1.0 1.326 4.111Ti 3.0 6.696 1.145Ti 10.09.2280.345Ti20.016.7410.338592I.Fatimah et al./Applied Clay Science 50(2010)588–593PILM~Ti-0.2/PILM N Ti-1.0/PILM~PILM.Ti-0.6/PILM and Ti-0.2/PILM presented a similar activity and their activities were higher than Ti-1.0/PILM.This is probably due to the textural change and surface distribution of TiO2.Loading of TiO2reduced the specific surface area, which resulted in low adsorption of MB on catalyst surface for the MB to be contacted with TiO2for reaction.For all the catalysts,Ti-1.0/PILM had the lowest specific surface area.In addition,the aggregation of TiO2at1mass%might also reduce its dispersion on PILM,making less amount of active sites than those on Ti-0.6/PILM and Ti-0.2/PILM and thus a lower activity of Ti-1.0/PILM.The Pearson correlation was tested to relate the rate constant with other properties of the catalysts such as titania content,specific surface area,microporous surface area,band gap energy and pore volumes(Table5).The Pearson correlation is the parameter to identify the strength of the linear relationship between two variables. The formula of the Pearson correlation coefficient,r,is given by the following equation(Everitt,2006).r=∑n i=1x i−Àxy i−Ày−ffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffiffi∑ni=1x i−Àx2r∑ni=1y i−Ày2ð2Þwhere,x is the parameter of physicochemical character tested,and y is the photocatalytic activity.The specific surface area and pore volume dominantly affected the photodegradation rate,suggesting an adsorption driven mechanism. Furthermore,the titanium content also affected the rate at lower correlation value(0.754).However,the correlation of the band gap energy,though important to photocatalysis,to the rate constant was not high suggesting that the band gap energy was not the determinant parameter of the catalytic degradation of MB.4.ConclusionAluminum pillared montmorillonite is a promising support for titania particles.The small titania particles showed the quantum size effect,and the band gap energy was lower than that of bulk TiO2. However,the photocatalytic activity for methylene blue degradation was not affected by the band gap energy.The results suggested an adsorption driven mechanism.The specific surface area and pore volume strongly influenced the photodegradation rate. AcknowledgementsThe authors would like to express sincere gratitude to the Ministry of Education,Republic of Indonesia through Hibah Penelitian Berpotensi Publikasi Internasional,DP2M-DIKTI2009for thefinancial and technical support to this research.ReferencesAn,T.C.,Chen,J.X.,Li,G.Y.,Ding,X.J.,Sheng,G.Y.,Fu,J.M.,Mai,B.X.,O'Shea,K.E.,2008.Characterization and the photocatalytic activity of TiO2immobilized hydrophobic montmorillonite photocatalysts degradation of decabromodiphenyl ether(BDE 209).Catal.Today139,69–76.Belessi,V.,Lambropoulou,D.,Konstantinou,I.,Katsoulidis,A.,Pomonis,P.,Petridis,D., Albanis,T.,2007.Structure and photocatalytic performance of TiO2/clay nano-composites for the degradation of dimethachlor.Appl.Catal.B73,292–299. Bergaya,F.,Theng,B.K.G.,Lagaly,G.,2006.Handbook of Clay Science,Developments in Clay Science,Volume1.Elsevier Science,Amsterdam.Binitha,N.N.,Sugunan,S.,2006.Preparation,characterization and catalytic activity of titania pillared montmorillonite clays.Micromeso.93,82–89.Bovey,J.,Kooli,F.,Jones,W.,1996.Preparation and characterization of ti-pillared acid-activated clay catalysts.Clay Miner.31,501–506.Daniel,L.M.,Frost,R.L.,Zhu,H.Y.,2007.Synthesis and characterisation of clay-supported titania photocatalysts.J.Col.Inter.Sci.316,72–79.Daniel,L.M.,Frost,R.L.,Zhu,H.Y.,ponite-supported titania photocatalysts.J.Col.Int.Sci.322,190–195.Dhage,S.R.,Choube,V.B.,Samuel,V.,Rav,V.,2004.Synthesis of nanocrystalline TiO2at 100°C.Mat.Lett.58(17–18),2310–2313.Ding,X.,An,T.,Li,G.,Zhang,S.,Chen,J.,Yuan,J.,Zhao,H.,Chen,H.,Sheng,G.,Fu,J.,2008.Preparation and characterization of hydrophobic TiO2pillared clay:the effect of acid hydrolysis catalyst and doped Pt amount on photocatalytic activity.J.Col.Int.Sci320,501–507.Everitt,B.S.,2006.The Cambridge Dictionary of Statistics,Cambridge University Press, 3rd Edition:101.Fujishima,A.,Rao,T.N.,Tryk,D.A.,2000.Titanium dioxide photocatalysis1–21. Fujishima,A.,Zhang,X.,Tryk,D.A.,2007.Heterogeneous photocatalysis:from water photolysis to applications in environmental cleanup.Int.J.Hyd.Ene.32, 2664–2672.Fujishima, A.,Zhang,X.,Tryk,D.A.,2008.TiO2photocatalysis and related surface phenomena.Surf.Sci.Rep.63,515–582.Fukahori,S.,Ichiura,H.,Kitaoka,H.,Tanaka,H.,2003.Photocatalytic decomposition of bisphenol A in water using composite TiO2-zeolite sheets prepared by a papermaking technique.Environ.Sci.Technol.37(5),1048–1051.Gil,A.,Gandía,L.M.,Vicente,M.A.,2000.Recent advances in the synthesis and catalytic applications of pillared clays.Catal.Rev.42,145–212.Gil, A.,Korili,S.A.,Vicente,M.A.,2008.Recent advances in the control and characterization of the porous structure of pillared clay catalysts.Catal.Rev.50(2),153–221.Hisanaga,T.,Tanaka,K.,2002.Photocatalytic degradation of benzene on zeolite-incorporated TiO2film.J.Haz.Mat.93(3),331–337.Kooli,F.,Bovey,J.,Jones,W.,1997.Dependence of the properties of titanium-pillared clays on the host matrix:a comparison of montmorillonite,saponite and rectorite pillared materials.J.Mater.Chem.7(1),153–158.Li,F.,Sun,S.,Jiang,Y.,Xia,M.,Sun,M.,Xue,B.,2008.photodegradation of an azo dye using immobilized nanoparticles of TiO2supported by natural porous mineral.J.Haz.Mat.152(3),1037–1044.Mahmoudi,N.M.,Arami,M.,2009.Degradation and toxicity reduction of textile wastewater using immobilized titania nanophotocatalysis.J.Photochem.Photobiol.B.94(1),20–24.Menesi,J.,Korosi,L.,Bazso,E.,Zollmer,V.,Richardt,A.,Dekany,I.,2008.Photocatalytic oxidation of organic pollutants on titania-clay composites.Chemosphere70, 538–542.Mogyorόsi,K.,Dekány,,K.,Fendler,J.H.,2003.Preparation and characterization of clay mineral intercalated titanium dioxide ngmuir19,2938–2946. Rajeshwar,K.,Osugi,M.E.,Chanmanee,W.,Chenthamarakshan,C.R.,Zanoni,Kajitvi-chyanukul,P.,Krishnan-Ayera,R.,2008.Heterogeneous photocatalytic treatment of organic dyes in air and aqueous media.J.Photochem.Photobiol.C.9,15–36. Rao,V.S.,Rachel,A.,Subrahmanyam,M.,Boule,P.,2003.Immobilization of TiO2on pumice stone for the photocatalytic degradation of dyes and dye industry pollutants.Appl.Catal.B.46,77–85.Reddy,E.P.,Davydov,L.,Smirniotis,P.,2003.TiO2-loaded zeolites and mesoporous materials in the sonophotocatalytic decomposition of aqueous organic pollutants: the role of the support.Appl.Catal.B42(1),1–11.Rezala,H.,Khalaf,H.,Valverde,J.,Romero, A.,Molinari, A.,Maldotti, A.,2009.Photocatalysis with Ti-pillared clays for the oxofunctionalization of alkylaromatics by O2.Appl.Catal.A.352,234–242.Romero,A.,Dorado,F.,Asencio,I.,Garcia,P.B.,Valverde,L.,2006.Ti-pillared clays: synthesis and general characterization.Clays Clay Miner.54(6),737–747. Vicente,M.A.,Belver,C.,Trujillano,R.,Rives,V.,Álvarez,A.C.,Lambert,J.F.,Korili,A., Gandia,L.M.,Gil, A.,2004.Preparation and characterisation of Mn-and Co-supported catalysts derived from Al-pillared clays and Mn-and Co-complexes.Appl.Catal.A.267,47–58.Yoda,S.,Sakurai,Y.,Endo,A.,Miyata,T.,Yanagishita,H.,Otake,K.,Tsuchiya,T.,2004.Synthesis of titania-pillared montmorillonite via intercalation of titanium alkoxide dissolved in supercritical carbon dioxide.J.Mater.Chem.14,2763–2767.Yuan,Peng,Yin,Xiaolin He,Hongping,Yang,Dan,Wang,Zhu,Linjiang,Jianxi,2006.Investigation on the delaminated-pillared structure of TiO2-PILC synthesized by TiCl4hydrolysis method.Micro.Meso.Mat.93(1–3),240–247.Zhang,S.,Fujii,H.,Nosaka,Y.,1998.The dispersion effect of TiO2loaded over ZSM-5 zeolite.J.Mol.Catal.A.129,19–224.Table5Result of Pearson correlation analysis on the effect of physicochemical parameter to the MB photodegradation rate.Factor Pearson correlation(confidence interval=0.95)Titanium content0.754Band gap energy−0.685Specific surface area0.885Micropore surface area0.746Pore volume0.824593I.Fatimah et al./Applied Clay Science50(2010)588–593。