Consideration on degradation kinetics and mechanism of thiamethoxam by reactive oxidative species (ROSs) during photocatalytic process
Consideration on degradation kinetics and mechanism of thiamethoxam by reactive oxidative species (ROSs) during photocatalytic process
复制标题
DOI：
10.1016/j.cej.2014.02.016
复制
发表时间：
2014-06
影响因子：
15.1
通讯作者：
Hai Yang;Huajie Liu;Zhibin Hu;Jiawei Liang;Huailin Pang;B. Yi
中科院分区：
文献类型：
--
作者：
Hai Yang;Huajie Liu;Zhibin Hu;Jiawei Liang;Huailin Pang;B. Yi
Photocatalytic degradation kinetics of thiamethoxam was optimized by using both single-variable-at-a-time and central composite design based on the response surface methodology. Four factors, such as catalyst dosages, pH values, temperatures and substrates concentration, affect the photocatalytic degradation rates significantly. Moreover, surface reactions with photoholes and radical dot OH on the surface of TiO 2 are responsible for the photocatalytic degradation of thiamethoxam. The effects of inorganic anions, metal ions and the contribution of reactive oxidation species on the degradation kinetics were also discussed. It could be concluded that the oxidative metal ions such as Cu 2+ and Fe 3+ promoted the degradation of thiamethoxam, while highly reductive anions such as I−, Br−, S 2 O 3 2-, NO 2-and CrO 3 2-inhibited the photocatalytic activity. The results also indicated that radical dot OH radicals functioned as the main active species for the photocatalytic degradation of thiamethoxam. Seven photocatalytic intermediates were separated and identified by HPLC and HPLC/MS/MS. The active sites of thiamethoxam were predicted by frontier electron densities and chemisorption pattern. The activation barriers Ea were calculated by the transition state of intermediates. Two degradation pathways were thereby proposed as the cleavage of 1, 3, 5-oxadiazinane ring and the hydroxylation of thiophene rings attacked by radical dot OH radicals on the initial stage of photocatalytic process.
