Catalytic oxidation of the dye wastewater with hydrogen peroxide

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<ul><li><p>Chemical Engineering and Processing 44 (2005) 10131017</p><p>Catalytic oxidation of the dye wastewaterhengUniver</p><p>b Key L g Unive</p><p>uary 202005</p><p>Abstract</p><p>This artic g H2Oan effective ared bindicate that ma ofgood chemi t the cthan those p lyst wabe recovered as use 2005 Else</p><p>Keywords: D Precip</p><p>1. Introduction</p><p>It has been estimated that about 15% of the dyes producedin the world are released into environment during theirsynthesis acontaminatbefore reletheir treatm[4], biodegprocessescontaminanhave been sater contaibeen foundoften referbyproducts</p><p>The tecwastewaterheterogeneions suchFenton rea</p><p> CorresponE-mail ad</p><p>the formation of hydroxyl radicals from hydrogen perox-ide [11,1316]. The organic compounds RH existed in thewastewater can be oxidized by hydroxyl radicals into R,which can be further, oxidized into carbon dioxide and wa-</p><p>0255-2701/$doi:10.1016/jnd processing [1], causing serious environmentalion. Thus, it is important to make some treatmentase. Various methods have been applied forent, including coagulation [2,3], denitrificationradation [5], absorption [6,7], and oxidation</p><p>[1,812]. The oxidation technologies, in whichts are converted into carbon dioxide and water,uccessfully used for the treatment of the wastew-</p><p>ning organic pollutants. Hydrogen peroxide hasuseful in the treatment of wastewater and is</p><p>red as a friendly oxidant because the oxidationare water and oxygen.</p><p>hnology using hydrogen peroxide to treat dyehas two different methods, homogeneous and</p><p>ous reaction. In the homogeneous reaction, metalas Fe2+and Cu2+ are used as the catalysts. Inction (a homogeneous reaction), the key step is</p><p>ding author. Tel.: +86 791 830 5149; fax: +86 791 830 5124.dress: qiuzm@ncu.edu.cn (Z. Qiu).</p><p>ter. However, metallic salts catalyst may cause secondarypollution.</p><p>The other one is heterogeneous catalytic reaction. Manyresearchers have studied the treatment of dye wastewater bymeans of wet oxidation via heterogeneous catalysts [1721].And this method, using heterogeneous catalysts and hydro-gen peroxide, has been found a good one for the treatment ofwastewater.</p><p>The aim of this study was to find a good heterogeneous cat-alyst to treat dye wastewater effectively. The catalyst wouldhelp to promote the decomposition of hydrogen peroxide toform hydroxyl radicals.</p><p>2. Materials and methods</p><p>2.1. Materials</p><p>All chemicals used in the experiment were analyticallypure reagents.</p><p> see front matter 2005 Elsevier B.V. All rights reserved..cep.2005.01.004Zumin Qiu a,b,, Yunbing He a, Xiaoca School of Environmental and Chemical Engineering, Nanchang</p><p>aboratory of Poyang Lake Ecology and Bio-resource Utilization, NanchanReceived 1 March 2004; received in revised form 28 Jan</p><p>Available online 16 March</p><p>le presented an approach for the treatment of dye wastewater usincatalyst, a series of catalysts containing transition metals were prepCu is a promising catalyst as it eliminated almost totally the chro</p><p>cal oxygen demand (COD) removal rate. The results also show tharepared by impregnation. Moreover, the activity decrease of the cata</p><p>after treatment. The results were also satisfied when the catalyst wvier B.V. All rights reserved.</p><p>ye wastewater; Hydrogen peroxide; Heterogeneous; Copper; Impregnation;with hydrogen peroxideLiu a, Shuxian Yu a</p><p>sity, Nanchang Jiangxi 330029, Chinarsity, Ministry of Education, Nanchang 330029, China05; accepted 28 January 2005</p><p>2 and heterogeneous catalysts. In order to screen outy impregnation and precipitation methods. The resultsthe acid scarlet aqueous solution accompanied with aatalysts prepared by precipitation were more effectives not changed between batches, and the catalysts couldd to treat other dye wastewater.</p><p>itation</p></li><li><p>1014 Z. Qiu et al. / Chemical Engineering and Processing 44 (2005) 10131017</p><p>2.2. Preparation of catalyst</p><p>-Al2O3 (gamma-alumina) was washed repeatedly withdistilled H[22]. The cnamely, theMAl2O3(method [deDetails offollows: thnating 10 gNi or Mn)metal). Theature. Afteand then ca</p><p>The M10 g -Al2Oaqueous so(CO(NH2)stant tempeprecipitatin100 C for</p><p>After thdepositedmetals)/(-</p><p>2.3. Cataly</p><p>Experimunder agitalyst, the glatemperaturstarted with</p><p>2.4. Analy</p><p>COD wchroma waat 510 nm [</p><p>3. Results</p><p>3.1. Screen</p><p>Table 1scarlet aquit can be fshowed wecompositiooxidize therier of -Aremoval rametals. Anon the remwas in the</p><p>Table 1Catalytic oxidation of acid scarlet solution by various heterogeneouscatalysts</p><p>st COD removal rate (%) Chroma removalrate (%)</p><p>O3 5.7 9.8l2O3(I) 62.1 83.12O3(I) 9.1 11.7l2O3(I) 13.2 21.4</p><p>l2O3(I) 27.8 40.2l2O3(P)a 72.3 98.1l2O3(P)a 33.8 53.6l2O3(P)a 18.9 32.8= 632.5 mg/L, 1.5 g catalyst, 2.5 mL H2O2, initial pH 4.0, reaction</p><p>120 mine preci</p><p>rationcatalysthosethe cauitablwater</p><p>Effect</p><p>ble 2red wprecip</p><p>s of thred w</p><p>ion ofecreasO3 orand c</p><p>Effect</p><p>g. 1 shytic acthe incatio wd whe</p><p>the r1. Th</p><p>+. Different CO(NH2)2/-Al2O3 (g) ratios would lead tormation of different compounds on the catalyst, which</p><p>d affect catalytic activity [24].</p><p>2of the precipitator on the catalytic activity</p><p>itator COD removal rate (%) Chroma removalrate (%)</p><p>3 26.7 42.8O3 33.6 51.22O 53.2 79.0</p><p>CO3 72.5 98.4H2)2 72.3 98.12O at first, dried and then activated at 300 Catalyst was prepared by two different methods,conventional impregnation method [denoted as</p><p>I), M is Cu, Zn, Ni or Mn], and precipitationnoted as MAl2O3(P), M is Cu, Zn, Ni or Mn].</p><p>the preparation of the catalyst were described ase MAl2O3(I) catalysts were prepared by impreg--Al2O3 powder into 40 mL nitrate of metal (Cu,or zinc acetate aqueous solution of 5 (wt.% ofn the solution was stirred for 4 h at room temper-</p><p>r filtration, the deposit was dried for 4 h at 100 C,lcined in air at 450 C for 4 h.Al2O3(P) catalyst was prepared by impregnating</p><p>3 powder into 40 mL metal nitrate or zinc acetatelution of 5 (wt.% of metal). Then 10 g precipitator2) was added to the solution, depositing in a con-rature water bath at 55 C for 4 h. After ageing,g, washing and filtering, the deposit was dried at4 h, and then calcined in air at 450 C for 4 h.e preparation, the loadings of these metals</p><p>on -Al2O3 were found to be (5.0 0.2 mgAl2O3 (g)) in both methods.</p><p>tic reaction</p><p>ents were carried out in a glass reactor (1000 mL)tion. After adding Acid Scarlet GR and the cata-ss reactor was placed in a water thermostat. The</p><p>e in the thermostat was kept at 70 C. The reactionthe addition of H2O2.</p><p>sis</p><p>as measured by dichromate method [23]. Thes determined by the absorbance of the solution1].</p><p>and discussion</p><p>ing tests</p><p>presented the results of the degradation of the acideous solution (1000 mg/L) at 70 C. From Table 1,ound that the catalyst without transition metalak catalytic activity in hydrogen peroxide de-n. Although H2O2 is a strong oxidant, it failed todye hue. So some metals were loaded on the car-</p><p>l2O3. As shown in Table 1, the COD and chromates increased when catalysts contained transitiond the type of transition metals had a great influenceoval rate of COD and chroma. The activity ordersequence of Cu &gt; Zn &gt; Mn &gt; Ni &gt;-Al2O3. The</p><p>Cataly</p><p>-Al2CuANiAlMnAZnACuAZnAMnACOD0time:</p><p>a Th</p><p>prepaThethanthatwas s</p><p>waste</p><p>3.2.</p><p>Taprepawithtermprepapositnot dNa2CCOD</p><p>3.3.</p><p>Ficatalwiththe rtainewhento beNH4the fowoul</p><p>TableEffect</p><p>Precip</p><p>Na2CONaHCNH3HNH4HCO(N, temperature: 70 C.pitator is CO(NH2)2 and the pH is variable in the process.</p><p>method also influenced the activity of catalyst.ts prepared by precipitation were more effectiveprepared by impregnation. The results indicatetalyst containing Cu prepared by precipitatione for the removal of both COD and chroma from.</p><p>of different precipitators</p><p>showed the effects of three kinds of catalystsith different precipitators. The catalysts prepareditator NH4HCO3 and CO(NH2)2 were better ine COD and chroma removal rates. The catalystith precipitator NH3H2O promoted the decom-H2O2, but the COD and chroma removal rates dide significantly. While the catalysts prepared withNaHCO3 had weaker activity in the removal of</p><p>hroma.</p><p>of the amount of CO(NH2)2</p><p>owed the effect of CO(NH2)2 concentration on thetivity. COD and chroma removal rates increasedrease in the ratio of CO(NH2)2/-Al2O3 (g) whenas below 0.5. A relatively higher value was ob-n the ratio was between 0.5 and 1, but decreasedatio was over 1. The optimum ratio was founde hydrolysis products of CO(NH2)2 are OH and</p></li><li><p>Z. Qiu et al. / Chemical Engineering and Processing 44 (2005) 10131017 1015</p><p>Fig. 1. Effect of the amount of CO(NH2)2 on catalytic activity, () CODand () colority.</p><p>3.4. Effect of the calcination temperature</p><p>The effect of the calcination temperature on the catalyticactivity warates increature when tfor which mwhen theand chromtemperaturthe optimuwas 475 C700 C poscalcinationthe sinterinwith spinelrapid decreit, the X-rainvestigateof 33.6 andthat of CuO</p><p>Fig. 2. Effect() colority.</p><p>Fig. 3. XRD(2) CuO and (</p><p>(curve (a))temperatur37 which windicated t</p><p>the ing. 2 anity thae cata2/g, seratur</p><p>The va</p><p>uringlutionuffs. Ter ionns waition:l pHder toneousding</p><p>itionsas fos showed in Fig. 2. COD and chroma removalsed with the increase in the calcination tempera-he temperature was lower than 475 C, the reason</p><p>ight be the formation of active CuO. However,temperature was higher than 475 C, the CODa removal rates decreased with the increase ine because some particles may be sintered. Hence,m calcination temperature to prepare the catalyst. Generally, Cu/-Al2O3 catalysts calcined belowsessed highly dispersed CuO, while when thetemperature was higher than 700 C, not only</p><p>g of particles but also the formation of CuAl2O4-type structure [25] might appear, resulting in thease of the catalytic activity. In order to elucidatey diffraction properties of the Cu catalyst were</p><p>d. According to Fig. 3, small peaks were at 238.7 (curve (b)), which were corresponding to[26]. While the peaks at 2 of 33.6 and 38.7</p><p>within Fiactivof th72 mtemp</p><p>3.5.</p><p>Dthe sodyestcoppper io(condinitiaIn ormogeby adcondrate wof the calcined temperature on catalytic activity, () COD and</p><p>reaction wa</p><p>3.6. Tests oother dye a</p><p>The stabruns were</p><p>was controits catalyticby the cokdye or orgthe catalysthe activityin the airfigure of CuO/Al2O3, (a) 750 C and (b) 450 C; (1) -Al2O3,3) CuAl2O4.</p><p>disappeared with the increase in the calcinatione and some peaks were observed at 2 of 31.4 andere corresponding to that of CuAl2O4 [26]. This</p><p>hat some catalysts were changed into CuAl2O4crease in the calcination temperature. As shownd Fig. 3, the highly dispersed CuO has a highern CuAl2O4. Furthermore, the BET surface arealysts at 475, 700 and 800 C were 112, 99 andhowing the sintering of the catalysts at highere.</p><p>lidation of the heterogeneous reaction</p><p>the experiment, some copper ions can be found inafter the treatment, but no metal was found in thehis may be caused by the leaching out of some</p><p>s from the catalyst. The concentration of the cop-s 9.87 ppm and the COD removal rate was 76.7%COD0 = 632.5 mg/L, 1.5 g catalyst, 2.5 mL H2O2,4.0, reaction time: 120 min, temperature: 70 C).</p><p>make sure whether the catalytic reaction was ho-or heterogeneous, experiments were carried out</p><p>no catalyst but 10 ppm Cu(NO3)2 solution (otherwere the same as above). And the COD removalund to be 4.7%, which confirmed that the catalytic</p><p>s heterogeneous.</p><p>f the stability of Cu catalyst and treatment ofqueous solution</p><p>ility of the Cu catalyst was shown in Table 3. Fiveoperated with the same catalyst at 70 C and pHlled at 4.0. When the catalyst was reused directly,</p><p>activity decreased slowly. This might be causeding of the catalyst surface and the inhibition ofanic compounds formed on some active sites oft. Nevertheless, the decrease was not great andof the catalyst can be recovered by recalcining</p><p>at 450 C for 3 h. From Table 3, the COD and</p></li><li><p>1016 Z. Qiu et al. / Chemical Engineering and Processing 44 (2005) 10131017</p><p>Table 3Catalyst stability</p><p>Catalyst COD removal rate (%) Chroma removalrate (%)</p><p>Fresh 77.5 99.1Reused once 73.9 98.9Reused twice 69.0 92.4Reused third 65.6 87.2Reused fourth 62.5 85.1Reused fifth 61.1 83.6Reused sixtha 73.6 98.1COD0 = 632.5 mg/L, reaction time: 120 min, temperature: 70 C, pH = 4.0,3.0 mL H2O2.</p><p>a The catalyst was calcined before reuse.</p><p>chroma removal rates of the recalcined catalyst were 73.6and 98.1, which was a little lower than that of the fresh one.The differesites, which</p><p>Table 4using Cu cwhen usedof the dyeDuring theserved to cH2O2, andcaused bythe chromoand then atthalene rinmay occurprincipallyfurther oxi</p><p>3.7. The p</p><p>As the oment the acenvironmenout from thand existeddards, pH v7.07.5 bytration of C</p><p>Table 4The treatmen</p><p>Category</p><p>Acid scarlet GSoluble blueAcid black 10Direct red FDirect scarletBasic flavineBasic pinkReaction timecatalyst.</p><p>4. Conclusions</p><p>This study investigated the oxidation of dye using the het-erogeneouscatalyst preof chromaalyst couldthe air at 4the activity</p><p>Acknowled</p><p>The autZhu JianhaThe resear</p><p>a and</p><p>rence</p><p>.A. Saleed withrans. M. Hasef meta71317. Xu,SAFC5 (2001.A. Rond denntotrop. Cripprocyclicrobiol..H. Janyntheticiron. S.M. Shontrol c2001) 8.G. Gircid inal aspey coba23112.M. Kobethylen</p><p>8 (2002.B. Konce might be caused by the poison of some activecould not be recovered.</p><p>showed the treatments of other dye wastewateratalyst and H2O2. The catalyst was also effectiveto treat other dye aqueous solutions. The chromaaqueous solution degraded easier than the COD.experiment, the color of the dye solution was ob-hange from red to dark-red with the addition ofthen gradually changed to colorless. This may bethe formation of OH radicals which would attackphoric group (e.g. azo-group, nitro-group) first,tacked the intermediates (e.g. phenyl ring, naph-g and so on). In this system, the oxidation of dyein two steps [27]: at first, the intermediates wereformed and then some of the intermediates were</p><p>dized to CO2 and H2O.</p><p>ost-treatment of the wastewater</p><p>ptimum pH should be controlled at 4.0, after treat-id solution could not be directly released into thet. Furthermore, some copper ions also leached</p><p>e catalyst (the Cu2+ concentration was 510 ppm)in solution. In order to reach the releasing stan-</p><p>alue of the treated wastewater must be adjusted toadding alkali. Under this condition, the concen-u2+ would be less than 2 ppm.</p><p>Chin</p><p>Refe</p><p>[1] Ir</p><p>T[2] T</p><p>o</p><p>1[3] Q</p><p>P1</p><p>[4] La</p><p>a</p><p>[5] Ce</p><p>c</p><p>[6] Ys</p><p>v</p><p>[7] Zc</p><p>([8] E</p><p>a</p><p>c</p><p>b1</p><p>[9] Im</p><p>3[10] Nt of other dye aqueous solutions</p><p>COD0 (mg/L) COD removalrate (%)</p><p>Chroma removalrate (%)</p><p>R 632.5 74.2 98.5966.2 78.1 99.3</p><p>B 624.3 72.7 98.41687.1 83.2 85.7</p><p>4B 1330.3 82.4 84.6O 899.3 77.7 87.3</p><p>810.1 76.9 86.5: 120min, temperature: 70 C, pH = 4.0, 2.5 mL H2O2, 1.5 g</p><p>todegradpolymer</p><p>[11] H.L. Sheater, Wa</p><p>[12] S. MunedegradatAir Soil</p><p>[13] F.J. BeltadvancedWater A</p><p>[14] C. Kangof hydroand ketocatalyst and H2O2 under mild conditions. Thepared by precipitation allowed a total eliminationand had a significant COD removal rate. The cat-be recovered between batches by recalcining in</p><p>50 C for 3 h though there was a little decrease ofin the COD and chroma removal rates.</p><p>gments</p><p>hors are grateful to Prof. Jiayang Chen and Doc.ng for their helpful discussions and corrections.ch work is funded by the Education Ministr...</p></li></ul>

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