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Desalination 268 (2011) 5559

Contents lists available at ScienceDirect

Desalin

.e ltoxic to organisms. The biological processes can ineffectively degradethese substances and decolorize the H-acid wastewater. As aromaticring with sulfonic (SO3H) is easily dissolved in water, the generalchemical and physical methods are very inefcient [3].

Wet air oxidation (WAO) is a method of oxidizing dissolvableor suspended organic compounds as well as reducible inorganiccompounds with oxygen or air at high temperature and high pressureconditions. The application of traditionalWAO is limited because of itssevere operation conditions and rather costly investment [46].

shown that, when associated with transition metal oxides and noblemetals, cerium oxide promotes oxygen storage and release to enhanceoxygenmobility, and forms surface and bulk vacancies to improve thecatalyst redox properties of the system [1618]. In the CWAO, TiO2with the good stability do not display the activity, and was often usedas the support of metals [1921].

No previous CWPO of H-acid studies dealing with Fe/TiO2CeO2catalysts have been reported. Yang et al. [22] presented an investiga-tion of catalytic wet air oxidation (CWAO) of phenol over CeO2TiO2Catalytic wet hydrogen peroxide oxidatideveloped in recent years, which can decomefuents, as well as poisonous, detrimentalwastewater [7,8]. By adding catalyst and oxi

Corresponding author. Tel.: +86 29 88302632; fax:E-mail address: zxlbx@china.com (B. Zhao).

0011-9164/$ see front matter 2010 Elsevier B.V. Aldoi:10.1016/j.desal.2010.09.050es in dye intermediates substituted by some), etc, that are extremely

TiO2CeO2-based CWPO systems have not yet been investigated.Cerium oxide and CeO2-containing materials have been studied as agood alternative for the oxidation catalysts and supports. It has beenwastewater are often aromatic compoundgroups, such as amino (NH2), nitro (NO21. Introduction

H-acid (1-amino-8-naphthol-3, 6-ddye intermediate which is widely usesynthesis of direct, acidic, reactive anpharmaceutical industry [1,2]. Since this complicated and the utilization ratwastewater from the manufacturingsubstituted derivatives of naphthalecolor and strong acidity. Organic suic acid) is an importantemical industry for thec dye, as well as in theuction process of H-acidw materials is low, thesses is rich in variouspound and is of dark

tion, because the OH radicals generated in the reaction are highlyoxidative, non-selective, and able to decompose many organiccompounds including dyes and pesticides. In recent years, manyinvestigators have been trying to improve the catalytic activity andstability of heterogeneous oxidation catalysts to enhance the efciencyof CWPO. Transitionmetals (mainly Fe, but also Cr, Mn, Co, Ni, and Cu)are supported over differentmaterials: AC [9], pillared clays [10], ZSM-5 [11], CeO2 [12], zeolite [13], SiO2 [14] and -Al2O3 [15]. However,on (CWPO) has beenpose high concentrationand hardly degradabledant, CWPO process can

catalysts. They odue to a promoproperties of titawas inuenced b

In the paper, Tco-precipitationBET nitrogen adsEDX), transmissi

+86 29 88373052.

l rights reserved.mild conditions without too much energy consump-TiO2H-acidCatalytic wet hydrogen peroxide oxidatioTiO2CeO2 and Fe/TiO2CeO2 catalysts

Binxia Zhao , Binchu Shi, Xiaoli Zhang, Xin Cao, YaoCollege of Chemical Engineering, Northwest University, Xi'an, Shaanxi 710069, China

a b s t r a c ta r t i c l e i n f o

Article history:Received 18 February 2010Received in revised form 26 September 2010Accepted 27 September 2010Available online 18 October 2010

Keywords:Catalytic wet hydrogen peroxide oxidation(CWPO)Metal oxideCeO2

TiO2CeO2 and Fe/TiO2CeOrespectively, and evaluatedhigh concentration aqueoucharacterized by BET, XRDcomparatively more active,pollutants of dye industry srestrained the growth oftemperature of 100 C, init98.1% color removal, 89.6%

j ourna l homepage: wwwof H-acid in aqueous solution with

ong Zhang

talysts were prepared by the methods of co-precipitation and impregnation,ough the catalytic wet peroxide oxidation treatment of H-acid solution in theedium under mild experimental conditions. Furthermore, the catalysts wereM-EDX and TEM. The results showed that iron-containing samples wereTiO2CeO2 (Ti/Ce 9/1, 2 wt.% Fe) was a very efcient catalyst to oxidize theas H-acid into biodegradable species and doping cerium into TiO2 obviouslytal, greatly enhancing the surface areas of the catalysts. At the reactionH of 5.0, the atmospheric pressure and the theoretical dosage of peroxide,and 65.4% TOC reduction with Fe/TiO2CeO2 catalyst were obtained.

2010 Elsevier B.V. All rights reserved.

ation

sev ie r.com/ locate /desa lbserved an increase in the mineralization efciencyting effect of the ceria in the structural and redoxnium dioxide. They found that the catalytic activityy Ce/Ti mol ratio seriously.iO2CeO2 and Fe/TiO2CeO2 catalysts are prepared byand impregnation, respectively, and characterized byorption method, scanning electron microscope (SEM-on electron microscope (TEM) and X-ray diffraction

UVVIS spectrophotometer to follow the progress of the decoloriza-tion during wet peroxide oxidation. An induced coupled plasma (ICPModel: IRIS Advantage) was used for determination of dissolvedmetal in solution. Residual hydrogen peroxide was determined by acolorimetric method.

3. Results and discussion

3.1. XRD and BET analysis of TiO2CeO2

XRD was used to investigate the phase structure and the phasecomposition of TiO2-CeO2 catalysts. Fig. 1 shows the power XRDpatterns of the 11 Ti/Ce catalyst samples. According to the mainfeatures of the patterns, the samples can be divided into two groups:Ti-rich catalysts (with titanium content of 80% and above) and Ce-richcatalysts (with cerium content 50% and above). For pure TiO2, only thepeaks of anatase titania (2=25.20, 37.76, 47.92, and 53.78) weredetected. It means that TiO catalyst calcined at 350 C exists as

56 B. Zhao et al. / Desalination 268 (2011) 5559(XRD). The purpose is to study the performance of TiO2CeO2 and Fe/TiO2CeO2 for the catalytic oxidation of H-acidwith hydrogen peroxide.

2. Materials and methods

2.1. Preparation of catalysts

The TiO2CeO2 catalysts were prepared by co-precipitationmethod. The hydrolysis of TiCl4 was performed at 0 C to get Tiaqueous solution. The mixture solution of the aqueous Ti and Ce(NO3)3 with different molecular ratios of Ti and Ce was added drop-wise to excess ammonia solution at room temperature under stirring,and then stirred for 2 h and aged in the 80 C for 3 h. The precipitatewas washed with distilled water to remove Cl, and dried at 110 Cfor 12 h. After that, the precursor was calcined in the air at 350 C for3 h to obtain TiO2CeO2 powder catalyst (pure CeO2 or TiO2 catalystswere prepared with co-precipitation by adding Ce(NO3)3 or Tiaqueous solution to excess ammonia solution).These catalysts werereferred to as Ti/Ce 10/0 (pure titanium oxide), Ti/Ce 9/1, Ti/Ce 8/2, Ti/Ce 7/3, Ti/Ce 6/4, Ti/Ce 5/5, Ti/Ce 4/6, Ti/Ce 3/7, Ti/Ce 2/8, Ti/Ce 1/9 andTi/Ce 0/10 (pure cerium oxide).

The TiO2CeO2 (Ti/Ce 9/1) was chosen from CWPO tests assupport, and 0.5, 1, 2, and 3 wt.% Fe (the weight ratio of Fe to carrier)/TiO2CeO2 catalysts were prepared by impregnating it in a solutionwith different concentrations of Fe(NO3)3 under room condition for12 h, then evaporated at 80 C and dried at 110 C for overnight. Theobtained catalysts were calcined in a furnace at 350 C for 3 h. Aftercalcinations, the catalysts were stored in a dessicator.

2.2. Characterization of samples

The surface areas of the samples were measured at 77 K using theBET method performed on Autosorb(MT)-1 Series-Surface Area andPore Size Analyzers. Powder X-ray diffraction (XRD) patterns of thecatalysts were obtained with a D/max-3C powder diffractometer byusing nickel-ltered Cu K radiation at a scanning range of 2070and under a speed of 4/min. X-ray tube voltage was 35 kV and theelectric current was 40 mA. Scanning electron microscopy (SEM) andenergy dispersive X-ray spectroscopy (EDX) techniques were used todetermine the catalyst granule morphology and elemental distribu-tion of the catalyst particles using JSM-5800 Oxford ISIS-200EDXscanning electron microscope. Transmission electron microscopy(TEM) measurements were performed on a Hitachi H-600 transmis-sion electron microscopy.

2.3. Determination of catalytic activity

CWPO process was carried out in the 0.5 L autoclave equippedwith a condenser, stirrer and heating device that keeps the constanttemperature. The 1.0 g of solid catalyst and 17.6 mL of hydrogenperoxide (30% w/w, corresponding to the theoretical stoichiometricamount of H2O2 for complete oxidation of H-acid up to CO2 and H2O)were introduced into 250 mL of aqueous H-acid solution (10 g/L). Thereaction was conducted at atmospheric pressure and the temperatureof 100 C. When the reaction temperature reached the setting value,the reaction started and the time was zero, the solution was analyzedto conrm the absence of adsorption by the catalyst. For all runs thereaction time was 90 min.

2.4. Analyses

Total organic carbon was determined using a Vario model TOCanalyzer. The analysis of COD was conducted in accordance withstandard method. The pH was measured by means of a PHS-3B pH-meter. The visible light absorbance at the characteristic wavelength of

the sample, i.e. 528 nm, was measured using a UV-2550 Shimadzu2

anatase structure. In Ti-rich samples, the peaks of anatase titaniabecame much weaker and the wider with the increase of adding Cecontent into TiO2, while no peaks of cerium oxides were observed inthe spectra of XRD. This means that the crystal size of TiO2CeO2particles decreased with the increase of Ce content in Ti-rich samples.When the Ti/Ce mol ratios were between 7/3 and 6/4, the peaksbecame very faint scattering, indicating that TiO2CeO2 existed asamorphous phase. The Ti/Ce 7/3 exhibited the most asymmetricdiffraction peaks. This can be associated with large lattice distortionresulting from the introduction of dopant/vacancy. Accordingly, thisexplains that the Ti/Ce 7/3 sample exhibited the largest BET surfacearea (as in Fig. 2). For pure CeO2, the strong peaks were attributedto cubic CeO2 (2=28.57, 33.09, 47.49, and 56.26). In Ce-richsamples, the dominant diffraction peaks are the characteristic ofcerianite CeO2. No titanium oxide phases were detected by XRD. Thismay be due either to the formation of TiCe oxide solid solutionswith cerianite structure or to the occurrence of amorphous titaniumoxide. Besides, in Ti-rich catalysts, with the increasing amount of Ce,some peaks of anatase titania moved left. This shift indicates that partof cerianite species enters into the titanium lattice and provokes thecontraction of its unit cell and shaping TiCe oxide solid solutionswith anatase titania structure. It is also noticeable that in Ce-richcatalysts, a progressive shift of the diffraction peaks to higher Braggangles was observed, whichwas due to the insertion of Ti ions into thelattice of CeO2, also shaping CeTi oxide solid solutionswith cerianitestructure.

The effect of ratio of Ti and Ce on BET surface area is depictedin Fig. 2. The surface area of pure TiO2 (68.25 m2/g) was bigger thanthat of pure CeO2 (55.93 m2/g). The BET surface area increased

20 25 30 35 40 45 50 55 60 65 70Diffraction angle (2.Theta)

Ti:Ce=0:10

Ti:Ce=1:9

Ti:Ce=2:8Ti:Ce=3:7Ti:Ce=4:6Ti:Ce=5:5Ti:Ce=6:4Ti:Ce=7:3Ti:Ce=8:2Ti:Ce=9:1Ti:Ce=10:0Fig. 1. XRD patterns of the different TiO2CeO2 catalysts.

040

80

120

160

0 0.2 0.4 0.6 0.8 1

BET

Sur

face

are

a/(m

2 /g)

Ti/(Ti+Ce)

Fig. 2. Effect of Ti/(Ti+Ce) composition on BET surface area.

57B. Zhao et al. / Desalination 268 (2011) 5559monotonically with increasing contents of cerium, up to 173.6 m2/gfor the Ti/Ce 7/3 sample, and then gradually dropped to 55.93 m2/g,the BET surface area of pure cerium oxide. For doped-CeO2 and doped-TiO2 catalysts, the surface areas of TiO2CeO2 catalysts are higher thanthat of pure CeO2 or TiO2 catalyst. As can be seen, the BET surface areaof all the composite oxide samples far outweighed that predicted formere mechanical mixtures of the two metal oxides. This suggests thatwith the current catalysts, there was a strong intimate interactionbetween titanium and cerium oxides.

3.2. XRD and BET analysis of Fe/TiO2CeO2

The XRD patterns of all the compositions (0, 0.5, 1, 2, and 3%) Fe/TiO2CeO2 (Ti/Ce 9/1) calcined at 350 C for 3 h is shown in Fig. 3. TheXRD patterns of Fe-doped TiO2CeO2 samples almost coincide withthat of bare TiO2CeO2 showing no crystalline phase attributed to ironoxide. Anatase type structure is kept almost same in all Fe-dopedTiO2CeO2 catalysts, only the peaks of anatase titania became muchstronger than bare TiO2CeO2. There are two reasons responsible forthis result. One possible reason is that the Fe3+ content in the Fe/TiO2CeO2 samples is below the detection limit of this technique. Another isthat all Fe3+ ions might substitute Ti4+ ions and insert into the crystallattice of TiO2CeO2 because the radii of Fe3+ (0.69 A) is similar to thatof Ti4+ (0.745 A), so Fe3+ can be easily incorporated into the crystallattice of TiO2, forming an irontitanium oxide solid solution [2325].

Table 1 shows the BET surface areas and the particle sizes of the Fe/TiO2CeO2 (Ti/Ce 9/1) catalysts. The BET surface areas of Fe/TiO2CeO were smaller than that of bare TiO CeO , moreover, they2 2 2

20 25 30 35 40 45 50 55 60 65 70Diffraction angle(2.Theta)

TiO 2-CeO 2

0.5% Fe/TiO 2-CeO 2

1% Fe/TiO 2-CeO 2

2% Fe/TiO 2-CeO 2

3% Fe/TiO 2-CeO 2

Fig. 3. XRD patterns of the different Fe/TiO2CeO2 catalysts.decreased monotonically with increasing contents of iron, up to91.9 m2/g. However, when the Fe content rose to 3%, the surface arearose slightly to 93.28 m2/g.

3.3. SEM and TEM analysis

Fig. 4 presents three representative TEM images of the followingsamples: pure TiO2, TiO2CeO2 (Ti/Ce 9/1) and 2% Fe/TiO2CeO2 (Ti/Ce9/1). In all cases, the small and irregular particles of the catalysts wereobserved. Moreover, it can be seen that from Fig. 4(a) slightaggregates of TiO2 particles are observed, but the better dispersioncan be achieved by doping of CeO2 as shown in Fig. 4(b). It is becauseof the insertion of Ce into the lattice of TiO2 and replacement of Ti ionproved by the fact that no peaks of cerium were detected in the XRDpattern, leading to great enhancement of the dispersion. It is alsonoticeable that since the FeCe ions inserted into the lattice of TiO2,the structure of Fe/TiO2CeO2 catalyst was better dispersion andmoreirregular which could partially explain the reason why the surfacearea of Fe/TiO2CeO2 catalyst was higher than that of TiO2.

The chemical composition of the catalyst on the surface of 2% Fe/TiO2CeO2 (Ti/Ce 9/1) catalyst was determined by SEM-EDX. Theresults obtained from SEM-EDX suggest that there was a little Fe(0.65%)whichwasmuch less than loading content (2%) and no Cewasobserved in the surface of the catalyst since most Fe and all Ce wereinserted into the lattice of TiO2. It was conrmed that no Fe wasdetected by XRD because of its low content in the surface.

3.4. Effect of the ratio of Ti and Ce

Fig. 5 shows the activity of the different catalysts in the CWPO of H-acid under the reaction temperature of 100 C, atmospheric pressure,a catalyst dosage of 1.0 g, H2O2 amount of 17.6 mL and reaction timeof 90 min. It was possible to achieve 40.1% color removal, 35.1% CODreduction, and 15.1% TOC reduction without catalyst, and 32.5.2% and15.3% TOC conversion were obtained in CWPO of H-acid over pureTiO2 and CeO2 catalysts, indicating that pure TiO2 was more activethan pure CeO2 which had little activity. The ratio of Ti and Ce affectedthe activity of the TiO2CeO2 catalyst greatly. When the ratio of Ti andCe was higher than 9/1, doping a little CeO2 into TiO2 could obviouslyimprove the catalytic activity. However, when the ratio of Ti and Cewas smaller than 9/1, the catalytic activity was decreased with theincrease of Ce content. Using the Ti/Ce 9/1 catalyst, which is the mostactive catalyst, 89.1% color removal, 69.6% COD, and 35.8% reductionswere obtained in CWPO of H-acid. It is noticed that the activities ofTiO2CeO2 catalysts were not in agreement with that of the surfaceareas of the TiO CeO catalysts (in Fig. 2). This nding can be

Table 1The BET surface area and the particle size of the catalysts.

Samples The surface area (m2/g) The size of the particles (nm)

TiO2CeO2 104.2 11.70.5% Fe/TiO2CeO2 95.0 12.71% Fe/TiO2CeO2 92.7 12.22% Fe/TiO2CeO2 91.9 13.13% Fe/TiO2CeO2 93.3 12.42 2

explained by considering that the concentration of the chemisorbedoxygen decreases on the surface of the catalysts with the highersurface areas, because the chemisorbed oxygen is the most activeoxygen specie, and plays an important role in the CWPO of organiccompounds [22].

3.5. Effect of Fe content in Fe/TiO2CeO2

Iron oxide appeared as a promising alternative in the CWPO ofrefractory contaminant such as phenol and dye [12,15]. The different

020

40

60

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100

10/0 9/1 8/2 7/3 6/4 5/5 4/6 3/7 2/8 1/9 0/10 None

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enta

ge re

mov

al (%

)

Ti/Ce

Color

COD

TOC

58 B. Zhao et al. / Desalination 268 (2011) 5559a iron loading content in Fe/TiO2CeO2 catalysts were prepared in orderto improve the degradation efciency of H-acid. Fig. 6 shows thedegradation efciency, obtained for the different Fe/TiO2CeO2catalysts at 100 C (after 90 min of reaction). It was evident that Feloading could obviously improve the activity of the catalyst, and thatgreater catalytic activity did not always correspond to the maximumFe content (catalyst 3% Fe/TiO2CeO2). It might rather be related witha better iron dispersion in TiO2CeO2 catalysts. When Fe content was2%, the degradation efciency was the highest, arrived 98.1% colorremoval, 89.6% COD and 65.4% TOC reduction, and it can be concludedfrom the results of CWPO that the TOC reduction can be improved byabout 30% compared to using TiO2CeO2 catalyst under the samereaction condition. Nevertheless, a general tendency to increase thecatalytic activity as the iron content increases was observed, probably

Fig. 5. COD removal of H-acid solution with the different TiO2CeO2 catalysts (pH=5.0,catalyst amount [TiO2CeO2]=1.0 g,H2O2dosage=17.6 mL, reaction temperature=100 C,and reaction time=90min).b

c

Fig. 4. TEM photographs of catalyst samples; (a) TiO2; (b) TiO2CeO2 (TiCe 9/1); (c) 2%Fe/TiO2CeO2 (Ti/Ce 9/1).because the iron (active phase) reacts with the hydrogen peroxideconstituting a modied Fenton system capable of generating hydroxyl(OH) and perhydroxil (HO2 ) radicals to carry out the oxidation of theorganic molecules [26,27]:

Fe3+ Cat + H2O2Fe2+ Cat + HO2 + H

1

Fe2+ Cat + H2O2Fe3+ Cat + HO + HO 2

RH + OHH2O + Rdfurther oxidation 3

HO2 + Fe3+ CatH + O2 + Fe

2+ Catd 4

HO2 + H2O2HO + H2O + O2 5

H2O2 +OHHO2 + H2O: 6

The hydroxyl radicals generated on the inner surface of themicroporous material can diffuse to the external surface to break thelarge molecule into smaller fragments which can then diffuse insidethe microporous material. The small number of sites on the externalsurface of themicroporousmaterial crystals may be sufcient to breakthe large molecule into smaller fragments [28].

The degradation efcient is strongly related to the consumption ofH2O2 which will be decomposed into hydroxyl [29]. H2O2 decompo-sition after 90 min was complete for our experiment with Fe/TiO2CeO2. The decomposition of H2O2 might give two hydroxyl radicalswhich react with H-acid in water.0

20

40

60

80

100

0 0.5 1 2 3

Perc

enta

ge r

emoval

(%

)

Fe loading (%)

Color

COD

TOC

Fig. 6. COD removal of H-acid solution with different Fe/TiO2CeO2 catalysts (pH=5.0,catalyst amount [2% Fe/TiO2CeO2]=1.0 g, H2O2 dosage=17.6 mL, reactiontemperature=100 C, and reaction time=90 min).

3.6. Stability of Fe/TiO2CeO2

As well known, the stability of the CWPO systems is one of theimportant factors for practical application. For this reason, recyclingexperiment was carried out using 2% Fe/TiO2CeO2 catalyst in order todetermine its stability. In particular, the 2% Fe/TiO2CeO2 catalyst wasrecovered by ltration from the solution after treatment, washedwithultra-pure water, dried at 110 C overnight and then re-used underthe same reaction conditions: pH 5.0, 1.0 g catalyst, 17.6 mL H O ,

leach out from the catalysts, which could cause additional pollution.

catalysts, adding a little of Ce to TiO2, the surface area of TiO2CeO2

[3] Y. Zhang, X. Quan, S. Chen, Y. Zhao, F. Yang, Microwave assisted catalytic wet airoxidation of H-acid in aqueous solution under the atmospheric pressure usingactivated carbon as catalyst, J. Hazard. Mater. B 137 (2006) 534540.

[4] S. Imamura, Catalytic and noncatalytic wet oxidation, Ind. Eng. Chem. Res. 38(1999) 17431753.

[5] F. Luck, A review of industrial catalytic wet air oxidation processes, Catal. Today 27(1996) 195202.

[6] V.S. Mishra, V.V. Mahajani, J.B. Joshi, Wet air oxidation, Ind. Eng. Chem. Res. 34(1995) 248.

[7] G. Centi, S. Perathoner, T. Torre, M.G. Verduna, Catalytic wet oxidation with H2O2of carboxylic acids on homogeneous and heterogeneous Fenton type catalysts,Catal. Today 55 (2000) 6169.

59B. Zhao et al. / Desalination 268 (2011) 5559increases, and in our Ti/Ce catalytic systems, surface area alone cannotaccount for the trend of activity change with composition. 35.8%and 65.4% TOC removals were obtained with TiO2CeO2 (Ti/Ce 9/1)and the Fe/TiO2CeO2 (Ti/Ce 9/1, 2% Fe) in CWPO of H-acid underthe reaction temperature of 100 C, atmospheric pressure, a catalystdosage of 1.0 g, H2O2 amount of 17.6 mL and reaction time of 90 min,respectively. It is necessary to improve the stability of Fe/TiO2CeO2further.

References

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[2] M. Noorjaha, M.P. Reddy, V.D. Kumari, B. Lavdrine, P. Boule, M. Subrahmanyam,Photocatalytic degradation of H-acid over a novel TiO2 thin lm xed bed reactorand in aqueous suspensions, J. Photoch. Photobio. A Chem. 156 (2003) 179187.To investigate the stability of 2% Fe/TiO2CeO2 with respect to metalleaching, the concentrations of dissolved Fe, Ti, and Ce in the solutionafter catalytic wet peroxide oxidation for 90 min were analyzed usingICP, and 4.93 and 0.45 mg/L for Fe and Ti, respectively. No detectableamount of dissolved Ce could be measured. This result indicates thatthe loss of color removal mainly was due to the leaching of Fe. Mucheffort should be given to the improvement of active componentsleaching from the catalysts in the next future.

4. Conclusions

TiO2CeO2 and Fe/TiO2CeO2 (Ti/Ce 9/1) catalysts prepared withco-precipitation and impregnation had good activity in CWPO of H-acid. The activity of TiO2CeO2 catalysts was strongly affected bycatalyst composition. The most active catalyst was Ti/Ce 9/1. Feloading could obviously improve the activity of TiO2CeO2 catalyst,and the greater catalytic activity did not always correspond to themaximum Fe content. The optimum Fe loading content was 2%. XRD,BET and SEM techniques showed the textural and structuralproperties. The interaction of metallic ions Ti, Ce and Fe causes theformation of TiCe and FeTiCe oxide solid solutions. For TiO2CeO2t=100 C, and 90 min reaction time. 98.1%, 83.5%, and 63.5% colorremoval of H-acid solution were obtained by three-run consecutiveexperiments, respectively. 35.3% of the iron was leached after three-run consecutive experiments. The results clearly show the presence ofFe ions in the solution coming from the catalyst and the stability of 2%Fe/TiO2CeO2 decreases fast in successive runs.

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Catalytic wet hydrogen peroxide oxidation of H-acid in aqueous solution with TiO2CeO2 and Fe/TiO2CeO2 catalystsIntroductionMaterials and methodsPreparation of catalystsCharacterization of samplesDetermination of catalytic activityAnalyses

Results and discussionXRD and BET analysis of TiO2CeO2XRD and BET analysis of Fe/TiO2CeO2SEM and TEM analysisEffect of the ratio of Ti and CeEffect of Fe content in Fe/TiO2CeO2Stability of Fe/TiO2CeO2

ConclusionsReferences