多菌灵的γ射线辐照降解机理研究

Study on Degradation Mechanism of Carbendazim by γ-irradiation

采用γ射线辐照技术降解多菌灵,考察了不同初始条件对多菌灵降解效果的影响,并通过液相色谱-质谱(LC-MS)技术和量子化学计算分析了多菌灵在水溶液中的降解产物和降解路径。结果表明:γ射线能有效降解多菌灵,初始浓度越低、吸收剂量越大,多菌灵的降解率越高;·OH自由基、·H自由基和水合电子e_(aq)^-在辐照降解过程中的贡献大小依次为·OH、·H、e_(aq)^-。LC-MS检测到m/z=119、134、208的降解产物。多菌灵的键级、键长和NBO电荷等量子化学信息能很好地解释LC-MS检测到的降解产物,结合LC-MS检测结果和量子化学分析得到的多菌灵的降解路径为:多菌灵在自由基的进攻下降解生成5-羟基多菌灵、2-氨基苯并咪唑和苯并咪唑,2-氨基苯并咪唑和苯并咪唑在自由基的进攻下继续降解为分子量更小的物质。

The radiolytic degradation process of carbendazim was investigated by γ-irradiation. The effect of the initial condition of irradiated solution on the effectiveness of carbendazim decomposition was studied, and the degradation products were identified by LC-MS, additionally, quantum chemistry was used to analyze the degradation pathway of carbendazim. The results indicate that carbendazim can be degraded efficiently, the lower the initial concentration of carbendazim is and the higher the absorbed dose is, the better the degradation rate of earbendazim is. The contribution to carbendazim degradation by the radicals is in the order of · OH） 〉· H〉eaq^-. Three main degraded products （m/z=119, 134 and 208） were identified by LC-MS. Bond orders, bond lengths and NBO atomic charges of carbendazim are highly in accordance with those of LC-MS identification. According to combination of parameters of carbendazim and LC-MS identification, the pathway of carbendazim degradation is that 5-hydroxycarbendazim, 2-aminobenzimidazole and benzimidazole are produced by free radicals reacted with carbendazim, then small molecules are produced by free radicals reacted with 2-amino- benzimidazole and benzimidazole.