取代脲类除草剂光催化降解动力学比较

为研究取代脲类除草剂在TiO₂光催化降解过程中的动力学规律,以非草隆、异丙隆和利谷隆3种取代脲类除草剂为研究对象,通过Langmuir-Hinshelwood动力学模型对其TiO₂光催化降解动力学进行模拟,并系统探讨了催化剂用量、C₀(取代脲类除草剂的初始浓度)、溶液pH、温度、ROSs(活性氧物种)和电子捕获剂等的影响. 结果表明:非草隆、异丙隆和利谷隆的TiO₂光催化降解均符合假一级动力学模型,其动力学常数分别为0.082 8、0.068 7和0.095 4 min-1；取代脲类除草剂分子中的芳香环和脲桥上的取代基对降解速率常数的大小有明显的影响. ROSs试验表明,非草隆、异丙隆和利谷隆光催化降解过程中分别有91.6%、95.5%和86.8%的贡献来自·OH；而光生空穴和其他ROSs的贡献相对较小,并且电子捕获剂BrO₃-和S₂O₈2-对取代脲类除草剂的降解动力学有显著的促进作用. 

Comparative Study on Photocatalytic Degradation Kinetics of Substituted Phenylurea Herbicides in Aqueous Solution

In order to elucidate the general laws of photocatalytic degradation kinetics, three substituted phenylurea herbicides, including fenuron, isopronuron and linuron, were selected as model compounds to investigate in a system of Xe lamp and TiO₂. The effects of catalyst dosages, initial concentration of substituted phenylurea herbicides, pH value, temperature, reactive oxidative species (ROSs) and electron-captured agents on photocatalytic kinetics were also systematically studied. The results indicated that the degradation kinetics followed a pseudo-first-order by Langmuir-Hinshelwood model, and the rate constants were obtained as 0.0828,0.0687 and 0.0954 min-1 for fenuron, isopronuron and linuron, respectively. Moreover, the substituted groups on aromatic ring and bridge chain of the urea group significantly affected the degradation rate. The results from ROSs suggested that the contributions of ·OH were 91.6%, 95.5% and 86.8% for fenuron, isopronuron and linuron, which played an important role in the photocatalytic degradation of these three substituted phenylurea herbicides, while photohole and the other ROSs only did minor contributions. Additionally, BrO₃- and S₂O₈2- of the electron-captured agents obviously promoted the degradation rates of the three substituted phenylurea herbicides. Based on the results, environmental fate, transfer effect and potential risk of substituted phenylurea herbicides could be properly evaluated in environmental waters.