Photodegradation of benzene, toluene and xylenes under visible light applying N-doped mixed TiO2 and...

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Catalysis Today xxx (2014) xxx–xxx

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Catalysis Today

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hotodegradation of benzene, toluene and xylenes under visible lightpplying N-doped mixed TiO2 and ZnO catalysts

.M. Ferrari-Limaa,∗, R.P. de Souzab, S.S. Mendesb, R.G. Marquesb, M.L. Gimenesb,.R.C. Fernandes-Machadob

Universidade Tecnológica Federal do Paraná, Rua Marcílio Dias 635, Apucarana 86812-460, BrazilUniversidade Estadual de Maringá, Av. Colombo 5790, Maringá 87020-900, Brazil

r t i c l e i n f o

rticle history:eceived 11 January 2014eceived in revised form 10 March 2014ccepted 14 March 2014vailable online xxx

a b s t r a c t

N-doped TiO2/ZnO catalysts were prepared by sol–gel technique and calcined at 380 and 500 ◦C. Itsphotocatalytic activity was evaluated in the photodegradation of benzene, toluene and xylenes (BTX)under visible-LED light and compared with the undoped TiO2/ZnO activity. The amount of doped nitrogenwas found to be 0.64 at%. Concentrations of BTX were analysed by gas chromatography applying theheadspace technique. The N TiO2/ZnO catalyst calcined at 500 ◦C led to reductions of benzene, tolueneand xylenes concentrations greater than 80 wt% after 120 min of irradiation. The photocatalytic reactions

eywords:itrogen doped catalystsiO2

nOhotocatalysisTXisible light

followed the first order kinetics.© 2014 Elsevier B.V. All rights reserved.

. Introduction

Aromatic compounds deserve very special attention fromesearchers, as well as from petrol stations, petrochemical and sol-ent industries administrators. Benzene, toluene and xylene (BTX)re highly toxic and carcinogenic hydrocarbons [1,2], whose rela-ively high solubility in water brings about a major concern aboutossil fuel spillages in aquatic media and groundwater pollution.TX can also be found in sewage treatment systems due to the dis-harge of contaminated wastes from petrol stations. According to

orld Health Organization (WHO), the maximum allowed concen-rations of benzene, toluene and xylenes in potable water are 0.01,.7 and 0.5 mg/L, respectively [3]. A variety of techniques have beentudied aiming to remove aromatic hydrocarbons from contami-ated water. Investigations on methods such as bioremediation,iodegradation, advanced oxidation processes and adsorption haveeen reported [4–7].

Photocatalysis is an advanced oxidation process which is well

Please cite this article in press as: A.M. Ferrari-Lima, et al., PhotodegradN-doped mixed TiO2 and ZnO catalysts, Catal. Today (2014), http://dx

nown by the ability to mineralise any sample contaminated byn organic substrate through the activation of a semiconductorxide, the photocatalyst [7]. TiO2 is undoubtedly the most usual

∗ Corresponding author. Fax: +55 43 3245 6460.E-mail address: ana [email protected] (A.M. Ferrari-Lima).

ttp://dx.doi.org/10.1016/j.cattod.2014.03.042920-5861/© 2014 Elsevier B.V. All rights reserved.

photocatalyst, and its activation requires the provision of ultravio-let radiation [8]. However, its activity still needs improvements inorder to avoid some drawbacks like charge recombination [8–11].

Many modifications on TiO2 structure and characteristics havebeen proposed aiming to enhance the photocatalytic activity andachieve visible light responsive catalysts. Previous works demon-strated that the heterojunction of similar band gap semiconductorslike TiO2 and ZnO can result in synergic effects due to the decreasein the recombination rate and increase in the lifetime of theelectron–hole pair [8]. Enhancement on visible light activity hasbeen reported as a consequence of nitrogen doping, which leads toa reduction in the band gap energy [12]. The two main routes ofnitrogen incorporation in the TiO2 structure involve replacementof oxygen with nitrogen (substitutional doping) or occupation ofinterstitial sites (interstitial doping). The binding energy rangesfrom 396 to 398 eV for substitutional nitrogen, and 400 to 406 eVfor interstitial nitrogen [13,14]. Di Valentin et al. [15] suggest thatinterstitial nitrogen binds to the interstitial O2− lattice forming N Otype bond surrounded by three atoms of Ti. Other authors describethe interstitial nitrogen as Ti O N or Ti N O, but without defininga geometric arrangement of atoms [14].

ation of benzene, toluene and xylenes under visible light applying.doi.org/10.1016/j.cattod.2014.03.042

Only a few papers have reported the synthesis of N-doped mixedoxides. The N-doped TiO2/ZnO catalyst has been synthesised andshowed good results on the photodegradation of methyl orange,but the level of incorporated nitrogen has not been measured

dx.doi.org/10.1016/j.cattod.2014.03.042


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Fig. 1. Flowchart of the process used for preparation of the catalysts.

15]. N-doped TiO2 coupled with ZnO nanotubes showed excellenthotocatalytic activities for the decomposition of NOx gas underisible-light [16]. Additionally, N-doped SiO2/TiO2; Sn-dopednO/TiO2 nanocomposite films; Fe-doped TiO2/ZnO have also beeneported [17–19].

In this sense, the present work aimed to synthesise and charac-erise N-doped mixed TiO2 and ZnO photocatalysts and evaluate itsctivity on the photodegradation of BTX aqueous solutions underisible light.

. Experimental

.1. Materials

Benzene (99.5% pure), toluene (99.8% pure) and xylenes (98.5%ure) from Mallinckrodt in HPLC grade were used for preparation ofTX solution. Titanium isopropoxide (Across Organics, 98% pure),

sopropanol (Fmaia, 99.5% pure), ammonium hydroxide (Fmaia,8–30% pure), zinc acetate (Synth) and potassium niobate (CBMM)ere used for the synthesis of the catalysts.

.2. Catalysts preparation

Catalysts were prepared by sol–gel method. An acid solutionf zinc acetate in isopropanol was sonicated for 30 min before theddition of titanium isopropoxide (TTIP) in an appropriate ratioo obtain 50 wt% of ZnO and 50 wt% of TiO2. The undoped catalystsere obtained by adding distilled water drop-wise into the solution

nd the N-doped catalysts were obtained by adding ammoniumydroxide instead of distilled water. The suspension formed wasontinuously stirred for 60 min, submitted to ageing for 48 h andhen dried at 80 ◦C followed by calcination at 380 and 500 ◦C for

h. Fig. 1 outlines the steps for preparation of the catalysts.

.3. Catalysts characterisation


.3.1. Specific surface area, XRD and SEM analysisTextural analysis was carried out by nitrogen adsorption

sotherm at 77 K using QuantaChrome Nova 1200 equipment. X-ay diffraction (XRD) was performed in a Bruker D8 Advance X-ray

PRESS Today xxx (2014) xxx–xxx

diffractometer with Cu 40 K� radiation, 30 mA and Ni filter. Theobserved peaks were compared with the data published by JCPDS.Scanning electron microscopy (SEM) analysis was carried out onShimadzu SS-550 Superscan Microscope.

2.3.2. Spectroscopic analysisHigh-resolution X-ray photoemission spectra (XPS) were

recorded in a Kratos AXIS UltraDLD spectrometer fitted withthe ‘delay line detector’. The equipment was operated with amonochromated X-ray source (Al) and the survey spectrum wasrecorded at 160 eV pass energy and 600 W X-ray power. The acqui-sition used time was 120 s.

Photoacoustic spectroscopy (PAS) was performed withmonochromatic light provided by a xenon lamp of 1000 W(Oriel Corporation 68820) in an apparatus containing a monochro-mator (Oriel Instruments 77,250), a high sensitivity capacitivemicrophone (Bruel and Kjaer) and a lock-in amplifier (EG and G5110). The light beam was modulated with a mechanical modulator(Stanford Research Systems SR540). The photoacoustic spectrumwas obtained on modulation frequency of 21 Hz at wavelengthfrom 200 to 800 nm. Emission spectra of the lamps were acquiredin a VS140 Linear Array UV–vis and Vis Spectrometer (HORIBA).

2.3.3. Zero point of chargeThe zero point of charge (pHZPC) was determined by suspending

fixed mass of catalyst samples into six 50 mL Erlenmeyer flasks con-taining 30 mL of 0.1 M potassium nitrate solution. The initial pH ofthese suspensions were adjusted to 2, 4, 6, 8, 10, and 12 by adding afew drops of nitric acid or potassium hydroxide. The solutions wereallowed to equilibrate for 24 h in an isothermal shaker at 22 ± 1 ◦C.The suspension was then filtered, and the final pH of these sampleswere measured again [20].

2.4. Photocatalytic reactions

The photocatalytic reactions were carried out with aqueoussolutions containing benzene, toluene and xylenes (100 mg/L each,300 mg/L cumulatively). The concentration of catalyst was 1.0 g/Land the degradation was monitored by gas chromatography usingan OV-5 column (5% phenyl, 95% dimethylpolysiloxane) applyingthe headspace technique. Prior to analysis, 5.0 mL of each samplewere heated in a 10 mL headspace vial at 70 ◦C for 30 min. Afterthat, 1.0 mL of the gas phase was injected in the chromatographiccolumn.

The photocatalytic reactor consisted of a multiple stirrer IKAModel RT 15 POWER with a 16 W white LED lamp (Ouroluz) onthe top. Reactions proceeded at 25 ◦C. The emission peak of thelamp was located at 439.8 nm and the intensity of emission was1270 ± 10 lx. The photocatalytic reactions were carried out for120 min. The photographic illustration of the reactor is showed inFig. 2.

3. Results and discussion

3.1. Catalysts characterisation

3.1.1. Specific surface area, XRD and SEM analysisTextural analysis results are shown in Table 1. The nitrogen

adsorption–desorption data showed type IV like isotherms withtype H2 hysteresis loop, indicating the presence of well-developedmesoporosity for all the catalysts. As it can be seen in Table 1, doped


catalysts showed higher specific surface area. These results may bedue to the presence of nitrogen which leads to controlled nucleationand growth of crystallites, as well as the formation of a well-orderedmesoporous structure [21,22].



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Fig. 2. Photograph of the photocatalytic reactor.

Table 1Characterisation of the catalysts.

Catalyst SBETa

(m2/g)Crystallite sizeb

(nm)Pore volumec

(cm3/g)Eg

d

(eV)pHZPC

TiZn 380 161.0 – 0.16 3.34 7.6TiZn 500 71.7 10.1 0.14 3.36 6.6N TiZn 380 175.7 – 0.22 2.94 7.5N TiZn 500 102.1 8.7 0.18 2.88 7.2

a BET surface area calculated from the linear part of the BET plot (P/P0 = 0.1–0.3).b Calculated by applying the Scherrer equation for line broadening to the zincite

(0 0 2) diffraction peak.c Total pore volume, taken from the volume of N2 adsorbed at P/P0 = 0.95.d Band gap energy obtained by photoacoustic spectroscopy.

Fig. 3. (a) X-Ray powder diffraction patterns for (a) TiZn and (b) N TiZn precursor

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The prepared catalyst powders showed to be amorphous in X-ray diffraction (Fig. 3), as it is expected for sol–gel precipitates [23].Annealing at 500 ◦C was necessary to induce formation of crys-tallinity. As shown in the X-ray diffraction patterns of TiZn 500and N TiZn 500 nanoparticles, a mixture of the three phases is evi-dent. Anatase (A) and rutile (R) phases of titania, together with thezincite ZnO are present. No shifts to the XRD peaks were observedafter doping. The presence of rutile phase in small quantities canbe beneficial since it promotes the electron transport to the con-duction band of rutile phase, which is adjacent to anatase phase.This transport can be effective in decreasing recombination rate sothat, photocatalytic activity of nanoparticles with rutile and anatasephases is higher than that of pure anatase phase as the presence ofrutile phase acts as a defect or impurity and causes high photocat-alytic activity [24,25].

The average crystallite size was estimated for TiZn 500 andN TiZn 500 by applying the Scherrer’s formula (D = K�/ cos �) onthe zincite (0 0 2) diffraction peaks (the highest intensity peak ofthe diffraction patterns), where � is wavelength of the Cu K� used,

is the full width at half maximum of the diffraction angle con-sidered, K is a shape factor (0.94) and � is the angle of diffraction.The results are shown in Table 1. The crystallite size was found tobe 10.1 nm and 8.7 nm for TiZn 500 and N TiZn 500, respectively.Similar magnitude results are described in literature for N TiO2catalyst prepared by sol–gel method [22].

Morphologies of TiZn 500 and N TiZn 500 revealed by SEMmicrographs are shown in Fig. 4. All samples appeared as agglom-erates of non-uniform particles. The powders in all cases presentedaggregates consisting of smaller particles deposited on larger par-ticles. Similar morphologies have been reported by Tian et al. [15]when N-doped TiO2/ZnO catalysts were prepared. EDX analysis wasperformed to characterise the elemental composition of the sam-ples TiZn 500 and N TiZn 500. A typical EDX pattern of the samplesis shown in Fig. 5. The representative EDX pattern further demon-strates the presence of carbon impurities in the sol–gel derivednanocrystallites.

3.1.2. Spectroscopic analysisXPS analysis has been performed to determine the chemical

states and concentration of each existing element. Fig. 6 shows theXPS survey spectra of doped and undoped catalysts. Elements of


N, Ti and Zn were confirmed to exist in doped sample by the threepeaks at binding energies of 400.4, 458.82, 1021.55 eV, which arerelated to N 1s, Ti 2p, and Zn 2p, respectively. The atomic loads of Ti,Zn and N were 14.23, 28.82 and 0.64 at%, respectively. Whereas, in

powder sintered at the temperatures indicated. Zn: zinc, A: anatase, R: rutile.


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Fig. 4. SEM micrographs of (a) TiZn and (b) N TiZn. Images on

ndoped catalysts, nitrogen was completely absent and the atomicoads of Ti and Zn were 12.81 and 29.4 at%, respectively. The two

ain ways of incorporation of nitrogen into the TiO2 structurenvolve replacing oxygen with nitrogen (substitutional nitrogen)r occupation of interstitial sites (interstitial nitrogen). The bindingnergy related to substitutional nitrogen ranges from 396 to 398 eVnd for interstitial nitrogen ranges from 400 to 406 eV [13,14].


PS analysis of N TiZn 500 indicated that N close to the surfaceas a characteristic binding energy of 400.4 eV. This is ascribedo interstitial nitrogen bound to lattice oxygen to give NO-likepecies.

Fig. 5. EDX pattern of (a) TiZn

ht were taken at higher magnification than the one on the left.

The band gap energies acquired by photoacoustic spectroscopyare presented in Table 1. It is observed that the nitrogen dopingcaused a red shift in the absorption threshold allowing the applica-tion of lower energy radiation sources for activation of the catalyst,as expected and described by several authors [13,26–28]. The low-est value for band gap energy, 2.88 eV, was achieved for N TiZn 500whose corresponding wavelength is 430 nm. The graphical abstract


shows the superposition of the white LED lamp emission spectraand the N TiZn 500 catalyst absorption spectra. It can be notedthat the doped catalyst is able to absorb the radiation emitted bythe lamp and thus, be activated by visible light.

500 and (b) N TiZn 500.



A.M. Ferrari-Lima et al. / Catalysis Today xxx (2014) xxx–xxx 5

Fig. 6. XPS analysis of (a) TiZn 500 and (b) N TiZn 500.

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.1.3. Zero point of chargeFig. 7 shows the pHZPC values in terms of difference pH in solu-

ion before and after soaking with potassium nitrate. The results areummarised in Table 1. TiZn 380 and TiZn 500 have pHZPC values of.6 and 6.6, respectively, while N TiZn 380 and N TiZn 500 haveHZPC values of 7.5 and 7.2, respectively. These values are close tohose found in literature for TiO2 and ZnO oxides [8,29]. It is knownhat the adsorption of pollutants and degradation rates are higherear the pHZPC of the catalyst [30]. However, at pH values close tohe pHZPC, the zero surface charge yields zero electrostatic surfaceotential that cannot produce the interactive rejection necessary toeparate the particles within the liquid. This induces a phenomenonf aggregation and photocatalyst clusters become larger [29]. This


ffect can facilitate the separation of the catalyst from the solution,ut it is important to consider the influence on the ability of theuspension to absorb and transmit light.

3.2. Visible-light-induced degradation of BTX

The degradation of BTX when the solution was irradiated withvisible light in the presence of TiZn and N TiZn was evaluated.Fig. 8 shows the photocatalytic degradation of BTX after 120 min ofirradiation. As seen in Fig. 8, there is about 35 wt% of reduction ofBTX in the absence of light.

This reduction is not assigned to photolysis since the solutionof BTX does not absorb the visible light emitted by the white LEDlamp, as shown in Fig. 9, and the absorption of light is a require-ment for the photolysis event [30]. Therefore, whereas the systemis under constant stirring, forced convection phenomena are prob-ably occurring and encouraging evaporation. Accumulation of BTX


on the surface of the catalysts have been checked after reactionsand no evidences of organic accumulated molecules have beenfound. In this sense, the assessment of the actual reaction rate of



6 A.M. Ferrari-Lima et al. / Catalysis Today xxx (2014) xxx–xxx

Fig. 7. Zero point of charge of the catalysts (a) TiZn and (b) N TiZn.

Fig. 8. Residual percentage of BTX after 120 min of irradiation.

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Table 2Kinetics parameters of benzene, toluene and xylenes degradation.

Catalyst kma × 10−3 (min−1) t1/2 (min) R2

TiZn 380 6.64 ± 0.13 438.7 0.9742TiZn 500 7.63 ± 0.19 653.9 0.9856N TiZn 380 9.93 ± 0.7 97.2 0.9601N TiZn 500 17.64 ± 0.09 80.2 0.9622

that, it can be assumed that (i) N TiO2 had visible light absorp-tion in the range of visible light due to the occurrence of interstitialdoping; (ii) coupling of N TiO2 with ZnO seemed to photosensi-tise ZnO in longer wavelength region and diminish recombination;

Table 3Final concentrations (mg/L) of benzene, toluene and xylenes after 120 minirradiation*.

Compound Catalyst

Initial Withoutcat

TiZn380

TiZn500

N TiZn380

N TiZn500

Benzene 100 73.8 44.8 36.9 26.1 14.1

Fig. 9. UV–vis absorption spectra of BTX solution.

hotodegradation considered the evaporation losses of BTX duringhe process.

Kinetics studies have been performed and the results are summ-rised in Table 2. The photodegradation followed a pseudo first


rder pattern. The kinetic constants, km, were calculated by obtain-ng the average value for the degradation kinetic constant of eachompound.

a Average value obtained from the kinetics constant of each compound (benzene,toluene, o-, m- and p-xylenes).

Results showed that within 120 min of visible light irradiationin the presence of the photocatalysts, the degradation rates of BTXwere 6.64 × 10−3, 7.63 × 10−3, 9.93 × 10−3 and 17.64 × 10−3 min−1

for TiZn 380, TiZn 500, N TiZn 380 and N TiZn 500, respectively.The best results were obtained when N TiZn 500 catalyst wasapplied. The final concentrations of each compound after treatmentcan be seen in Table 3. The Brazilian legislation establishes limits of1.2 mg/L for benzene and toluene and 1.6 mg/L for xylenes presentin treated wastewater prior to release in the environment. In thisway, about 99% of the tested chemicals should be degraded. Thereferred efficiency was achieved when the solution was irradiatedduring 240 min with N TiZn 500 catalyst.

The observed behaviour patterns suggest that the reaction ratecan be enhanced by nitrogen incorporation into the TiO2 matrix thatled to a red shift on the band gap absorption edge, as well as by thepresence of rutile phase of TiO2 in combination with anatase phaseon N TiZn 500, as previously discussed. Additionally, in previousstudy [8] commercial mixed TiO2/ZnO photocatalysts have provedthat the heterojunction of both semiconductor oxides led to syner-gic effect by means of electron transfer from the conduction bandof ZnO to the conduction band of TiO2 and the hole transfer fromthe valence band of TiO2 to the valence band of ZnO, decreasing therecombination rate and increasing the lifetime of the electron–holepair, thus enhancing the occurrence of redox reactions. In face of


Toluene 100 73.2 45.7 39.5 28.6 12.9Xylenes 100 64.8 49.1 45.1 31.0 13.7

* Source and intensity of irradiation: 439.8 nm LED lamp, 1270 ± 10 lx.


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iii) the combination of anatase and rutile phases of TiO2 increasedhe electron–hole pair separation. This efficient charge separationncreased the lifetime of the charge carriers and enhanced thefficiency of the interfacial charge transferring to adsorbed sub-trates [16].

. Conclusions

Nanocrystalline undoped and N-doped TiO2 have been synthe-ised by a simple method involving titanium(IV) isopropoxide, zinccetate and ammonia. The synthesised material presented a mix-ure of rutile and anatase phase of TiO2 and zincite phase of ZnOith a high surface area and a crystal size in the nanometric scale.

he nitrogen doping caused a red shift in the absorption bandffecting the photocatalysis directly. The oxide N TiZn 500 showedfficient catalytic activity in degrading the BTX in aqueous solutionnder visible light.

cknowledgements

This work was sponsored by the Brazilian agencies CNPq andAPES.

eferences

[1] F. Simantiraki, C.G. Kollias, D. Maratos, J. Hahladakis, E. Gidarakos, J. Environ.Chem. Eng. 1 (2013) 9–17.

[2] H. Nourmoradia, M. Nikaeen, M. Khiadani, Chem. Eng. J. 191 (2012) 341.[3] World Health Organization, Guidelines for Drinking-Water Quality, World


Health Organization, Distribution and Sales, Geneva, Switzerland, 2004.[4] Chi-Wen Lin, Chih-Hung Wu, Chen-Ting Tang, Shih-Hsien Chang, Bioresour.

Technol. 124 (2012) 45–51.[5] D.E.C. Mazzeo, C.E. Levy, D.F. de Angelis, M.A. Marin-Morales, Sci. Total Environ.

408 (2010) 4334–4340.

[

[

[

PRESS Today xxx (2014) xxx–xxx 7

[6] M. Aivalioti, I. Vamvasakis, E. Gidarakos, J. Hazard. Mater. 178 (2010)136–143.

[7] D. Cazoir, L. Fine, C. Ferronato, J.-M. Chovelon, J. Hazard. Mater. 235–236 (2012)159–168.

[8] A.M. Ferrari-Lima, R.G. Marques, N.R.C. Fernandes-Machado, M.L. Gimenes,Catal. Today 209 (2013) 79–83.

[9] S. Liao, H. Donggen, D. Yu, Y. Su, G. Yuan, J. Photochem. Photobiol., A 168 (2004)7–13.

10] S.G. Kumar, L.G. Devi, J. Phys. Chem. A 115 (2011) 13211–13241.11] V.S. Santana, N.R.C. Fernandes-Machado, Catal. Today 133–135 (2008)

606–610.12] A. Paola, E. García-López, G. Marcì, L. Palmisano, J. Hazard. Mater. 211–212

(2012) 3–29.13] J. Ananpattarachai, P. Kajitvichyanukul, S. Seraphin, J. Hazard. Mater. 168 (2009)

253–261.14] F.E. Oropeza, J. Harmer, R.G. Egdell, R.G. Palgrave, Phys. Chem. Chem. Phys. 12

(2010) 960–969.15] J. Tian, J. Wang, J. Dai, X. Wang, Y. Yin, Surf. Coat. Technol. 204 (2009) 723–730.16] Y. Huang, Y. Wei, J. Wu, C. Guo, M. Wang, S. Yin, T. Sato, Appl. Catal., B: Environ.

123–124 (2012) 9–17.17] C. Kim, M. Choi, J. Jang, Catal. Commun. 11 (2010) 378–382.18] S. Benkara, S. Zerkout, H. Ghamri, Mater. Sci. Semicond. Process. 16 (2013)

1271–1279.19] J. Gao, X. Luan, J. Wang, B. Wang, K. Li, Y. Li, P. Kang, G. Han, Desalination 268

(2011) 68–75.20] M. Al-Harahsheh, R. Shawabkeh, A. Al-Harahsheh, K. Tarawneh, M.M. Batiha,

Appl. Surf. Sci. 255 (2009) 8098–8103.21] K.M. Parida, J. Brundabana Naik, J. Colloid Interface Sci. 333 (2009) 269–276.22] G.C. Collazzo, E.L. Foletto, S.L. Jahn, M.A. Villetti, J. Environ. Manage. 98 (2012)

107–111.23] T. Peng, D. Zhao, K. Dai, W. Shi, K. Hirao, J. Phys. Chem. B 109 (2005) 4947–4952.24] J.G. Yu, Y.R. Su, B. Cheng, Adv. Funct. Mater. 17 (2007) 1984–1990.25] M.A. Behnajady, H. Eskandarloo, N. Modirshahla, M. Shokri, Desalination 278

(2011) 10–17.26] C. Di Valentin, E. Finazzi, G. Pacchioni, A. Selloni, S. Livraghi, M.C. Paganini, E.

Giamello, Chem. Phys. 339 (2007) 44–56.27] J. Sun, L. Qiao, S. Sun, G. Wang, J. Hazard. Mater. 155 (2008) 312–319.


28] D. Li, N. Ohashi, S. Hishita, T. Kolodiazhnyi, H. Haneda, J. Solid-State Chem. 178(2005) 3293–3302.

29] S. Malato, P. Fernández-Ibánez, M.I. Maldonado, J. Blanco, W. Gernjak, Catal.Today 147 (2009) 1–59.

30] J.-M. Herrmann, J. Photochem. Photobiol., A 216 (2010) 85–93.


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