A Study On V₂O₅-TiO₂-AlF₃/Al₂O₃Catalytic Ozonation Of Organic Compound

The application of ozone in water treatment is reviewed at first, andthe emphasis of discussion is put on heterogeneous catalytic ozonationtechnology developed recently. On the basis of the existing shortcomings ofheterogeneous catalytic ozonation, the research target and main task of thiswork was proposed. The contents of the dessertation mainly include threeparts: Kinetic mechanism of acetic acid degradation by ozone in thepresence of both H₂O₂and Titanium Silicalite（TS-1）; Oxidative efficiencyof V₂O₅-TiO₂-AlF₃/Al₂O₃catalytic ozonation of2-（2,4-dichlorophenoxy）propionic acid; Catalytic performance of V₂O₅-TiO₂-AlF₃/Al₂O₃inozonation of tetrachloropicolinic acid, acetophenone and acetic acid. Theabove results are highly significant for extending application of catalyticozonation，especial for heterogeneous catalytic ozonation, in wastewatertreatment.In chapter Ⅳ, The ozonation of oxalic acid in the presence of H₂O₂and TS-1was investigated under pH=2.8. The experimental results showed that the presence of both TS-1and H₂O₂was the necessary conditions forpromoting the efficiency of acetic acid degradation by ozone. The mainreason for this result might be: TS-1can react with H₂O₂to produce atitanium superoxide species, which can tranfer ozone to hydroxyl radicals.The adsorption and decomposition of ozone on the catalyst was therate-determining step in this process. A pseudo zero-order kinetics equationwas obtained according to the kinetic mechanism, and a linear relationshipbetween1/C_O3⁺and1/k_hetewas also achieved.In chapter Ⅴ, a multicomponent catalyst characterized asV₂O₅-TiO₂-AlF₃/Al₂O₃by XRD was prepared via incipient wetnessimpregnation. The activity of the catalyst in ozonation was evaluated indegradation of2-（2,4-dichlorophenoxy） propionic acid （2,4-DP）. Theresults showed that the catalyst could greatly improve the e ciency ofozonation of2,4-DP. The test of tert-butyl alcohol addition indicated thatthe catalytic ozonation of2,4-DP might follow a hydroxyl radical-typemechanism. The R_ctvalue of the catalytic ozonation calculated by therelative method was larger than ozonation alone. The recycling testindicated that the catalyst remained relatively stable in ozonation of2,4-DP.In chapterⅥ, The catalytic activity of V₂O₅-TiO₂-AlF₃/Al₂O₃wasevaluated in ozonation of three different types of organic compounds,including a heterocyclic compound3,4,5,6-tetrachloropicolinic acid, anaromatic compound acetophenone and a small molecular organic acid acetic acid, under pH2.8. The results showed that the catalyst couldimprove all e ciencies of ozonation of these three typical organiccompounds. The test of tert-butyl alcohol addition indicated that thecatalytic ozonation of three organic pollutants all followed hydroxylradical-type mechanism. The R_ctvalues of the catalytic ozonation fordegradation of these three organic compounds were all larger10times thanthose of ozonation alone, indicating that the V₂O₅-TiO₂-AlF₃/Al₂O₃catalytic ozonation system could generate more hydroxyl radicals thanozonation alone did. The above results demonstrate that the catalyst hasgood activity in ozonation of three organic compounds. This fact is highlysignificant for extending application of advanced oxidation technology inwastewater treatment.