Photocatalytic degradation of chlorfenapyr in aqueous suspension of TiO2
Photocatalytic degradation of chlorfenapyr in aqueous suspension of TiO2
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DOI：
10.1016/j.molcata.2005.02.010
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发表时间：
2005-05-24
影响因子：
--
通讯作者：
Lu, YT
中科院分区：
文献类型：
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作者：
Cao, YS;Chen, JX;Lu, YT
采用两种不同的单色紫外光照射（300和350 nm）研究了溴虫腈在二氧化钛悬浮液中的直接光解和光催化降解。溴虫腈的直接光解和光催化降解均符合准一级动力学（C-t = C（0）e（-kt））。光解反应是缓慢的，并且相应的分解率在300和350 nm的UV下在TiO 2的存在下分别增加了约2.5和3倍。由于氢氧根离子的增加，在中性至碱性范围内，光催化速率随pH的增加而增加。然而，在中性介质中，反应逐渐被延迟。在pH 4、6、7、9和11时，降解半衰期（t（1/2））分别为13.7、16.2、16.2、10.7和8.7 min。温度的影响有助于溴虫腈的光催化降解。光催化降解速率随TiO 2投加量的增加而增加，且在较高的TiO 2投加量下，反应受到抑制。当使用1200 mg L-1 TiO 2时，降解速度最快，随着催化剂浓度的增加，降解速度缓慢增加，直至800 mg L-1，当浓度从800增加到1200 mg L-1时，降解速度更快，在1600 mg L-1时降解速度降低。在较低的溴虫腈浓度下，降解速率要快得多。H_2O_2辅助降解实验结果表明，低投加量的H_2O_2能提高溴虫腈的降解速率，但过量的H_2O_2会消耗羟基自由基，使降解速率降低。(c)2005 Elsevier B. V.保留所有权利。
The direct photolysis and the photocatalytic degradations of chlorfenapyr in TiO2 suspensions with and without the use of hydrogen peroxide were studied using two different monochromatic UV irradiations (300 and 350 run). Both the direct photolysis and photocatalytic degradations of chlorfenapyr follow pseudo-first-order degradation kinetics (C-t = C(0)e(-kt)). Photolysis reactions were slow, and the corresponding photocatalysis rates were increased by about 2.5 and 3 times in the presence of TiO2 at 300 and 350 nm of UV, respectively. Photocatalytic rates were increased with the pH at neutral to alkaline ranges because of the increase of hydroxide ions. However, the reaction was gradually retarded at the neutral medium. The half times of degradation (t(1/2)) were 13.7, 16.2, 16.2, 10.7 and 8.7 min, respectively, at pH 4, 6, 7, 9 and 11. The effect of temperature is helpful to the photocatalytic degradation of chlorfenapyr. The photocatalytic degradation rates were found to increase with TiO2 dosages, and the reaction was retarded at higher TiO2 dosages. The fastest degradation occurred when 1200 mg L-1 TiO2 was used, the rate increased slowly with increasing catalyst concentration up to 800 mg L-1 and more rapidly when the concentration was increased from 800 to 1200 mg L-1, and decreased at 1600 mg L-1. A much faster degradation rate at lower chlorfenapyr concentrations was achieved. The results of H2O2-assisted photocatalysis experiments showed that a low H2O2 dosage in photocatalysis would enhance the degradation rate of chlorfenapyr, however, an overdose of H2O2 will retard the rate because of the expenditure of hydroxyl radicals. (c) 2005 Elsevier B.V. All rights reserved.