College of Civil Engineering and Architecture, Zhejiang University of Technology, Hangzhou, 310023, China.
College of Civil Engineering and Architecture, Zhejiang University of Technology, Hangzhou, 310023, China.
Chemosphere. 2020 Sep;255:126962. doi: 10.1016/j.chemosphere.2020.126962. Epub 2020 May 7.
The degradation of N,N-diethyl-meta-toluamide (DEET) in aqueous solution by the UV/monochloramine (UV/NHCl) process was examined systematically in this study. DEET was resistant to UV photolysis and chloramination, while the synchronous combination of UV irradiation and NHCl can effectively eliminate DEET, which was caused by the generation of hydroxyl radicals and reactive chlorine species. The former played the critical role in DEET degradation, while the contribution of the latter can be ignored. Under all investigated experimental conditions, DEET degradation in the UV/NHCl process followed the pseudo-first-order kinetic model. The water quality parameters exerted the complicated impact. Reducing solution pH and raising water temperature both favored the DEET removal. The presence of sulfate, humic acid and fulvic acid accelerated the degradation, while the introduction of bicarbonate and high-concentration chloride retarded the removal. The plausible degradation pathways of DEET in the UV/NHCl process were proposed through the combination of QTOF/MS analysis and DFT calculation, and mainly involved in the cleavage of C-N bond, dealkylation, mono- and polyhydroxylation. The acute toxicity of reacted solution underwent a trend of first increasing and then decreasing with the prolonged irradiation time, which can be well illustrated by quantitative structure-activity relationship analysis. Electrical energy per order was employed to determine the energy consumption and the optimal conditions were determined as UV fluence of 369.9-493.2 mJ cm and NHCl dosage of 5-20 mg L.
本研究系统考察了 N,N-二乙基间甲苯甲酰胺（DEET）在水溶液中经紫外/单氯胺（UV/NHCl）过程的降解情况。DEET 对紫外光解和氯胺化具有抗性，而紫外辐射与 NHCl 的同步组合可以有效地消除 DEET，这是由于羟基自由基和活性氯物种的生成所致。前者在 DEET 降解中起着关键作用，而后者的贡献可以忽略不计。在所有研究的实验条件下，UV/NHCl 过程中 DEET 的降解符合准一级动力学模型。水质参数产生了复杂的影响。降低溶液 pH 值和提高水温均有利于 DEET 的去除。硫酸盐、腐殖酸和富里酸的存在加速了降解，而碳酸氢盐和高浓度氯离子的引入则阻碍了去除。通过 QTOF/MS 分析和 DFT 计算的结合，提出了 UV/NHCl 过程中 DEET 的可能降解途径，主要涉及 C-N 键的断裂、脱烷基化、单羟基化和多羟基化。反应溶液的急性毒性随照射时间的延长呈现先增加后降低的趋势，这可以通过定量结构-活性关系分析得到很好的说明。用单位电耗来确定能耗，确定的最佳条件为 UV 通量为 369.9-493.2 mJ/cm 和 NHCl 剂量为 5-20 mg/L。
