Comparative study of imazalil degradation in three systems: UV/TiO₂, UV/K₂S₂O₈ and UV/TiO₂/K₂S₂O₈

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• 作者：R. Hazime ; Q.H. Nguyen ; C. Ferronato ; A. Salvador ; F. Jaber ; J.-M. Chovelon
• 关键词：Imazalil ; Alcohol ; UV/K2S2O8 ; UV/TiO2/K2S2O8 ; Sulfate radicals
• 刊名：Applied Catalysis B: Environmental
• 出版年：2014
• 出版时间：January, 2014
• 年：2014
• 卷：144
• 期：Complete
• 页码：286-291
• 全文大小：594 K

文摘

The degradation of imazalil was achieved in three different advanced oxidation processes, namely UV/TiO₂, UV/K₂S₂O₈ and UV/TiO₂/K₂S₂O₈. The most relevant findings showed that for the UV/TiO₂ system, the best efficiency was obtained at alkaline pH for which the rate of degradation is governed by imazalil adsorption onto TiO₂, while for the UV/TiO₂/K₂S₂O₈ system, the best efficiency was obtained at acidic pH for which the rate of degradation is governed by persulfate adsorption onto TiO₂ surface. In this last case, sulfate adsorption can reduce e^?/h⁺ recombination while sulfate radicals are generated. Concerning the UV/K₂S₂O₈ system, it was shown that pH does not play an important role in the degradation and persulfate concentration is the main factor governing the rate of degradation.

Experiments with tert-butanol were achieved at different pH and the results showed that at pH = 6.5 and with a ratio [K₂S₂O₈]/[imazalil] = 100, hydroxyl radicals were responsible for 67.6 % of the degradation in the UV/TiO₂ system, 3.1 % in the UV/K₂S₂O₈ system, meaning that the degradation should be mainly attributed to sulfate radicals and 33.2 % in the UV/TiO₂/K₂S₂O₈ system meaning that both OH and SO₄^? were involved in the degradation.

Coming to the comparison of photoproducts by using LC/MS/MS (pH = 6.5), the conclusion is that hydroxylated products were more produced in the UV/TiO₂ system while a mechanism involving a charge transfer would be responsible of the degradation with persulfate systems. TOC analysis shows that total mineralization was reached faster in systems containing persulfate.