International Program in Hazardous Substance and Environmental Management, Graduate School, Chulalongkorn University, Bangkok, 10330, Thailand; Center of Excellence on Hazardous Substance Management (HSM), Chulalongkorn University, Bangkok, 10330, Thailand.
Department of Civil and Environmental Engineering, North Dakota State University, Fargo, ND, 58108-6050, USA.
Water Res. 2016 Jul 1;98:160-7. doi: 10.1016/j.watres.2016.04.010. Epub 2016 Apr 11.
Photodegradation of haloacetonitriles (HANs), highly carcinogenic nitrogenous disinfection by-products, in water using vacuum ultraviolet (VUV, 185 + 254 nm) in comparison with ultraviolet (UV, only 254 nm) was investigated. Monochloroacetonitrile (MCAN), dichloroacetonitrile (DCAN), trichloroacetonitrile (TCAN), and dibromoacetonitrile (DBAN) were species of HANs studied. The effect of gas purging and intermediate formation under VUV were examined. The results show that the pseudo first order rate constants for the reduction of HANs under VUV were approximately 2-7 times better than UV. The order of degradation efficiency under VUV and UV was MCAN < DCAN < TCAN < DBAN. The degradation efficiencies of individual HANs under VUV were higher than those of mixed HANs, suggesting competitive effects among HANs. Under nitrogen purging, the removal rate constants of mixed HANs was much higher than that of the aerated condition by 34.4, 34.9, 10.1, and 3.8 times for MCAN, DCAN, TCAN, and DBAN, respectively. The major degradation mechanism for HANs was different depending on HANs species. Degradation intermediates of HANs such as 2-chloropropionitrile, 2,2-dimethylpropanenitrile, and fumaronitrile were produced from the substitution, addition, and polymerization reactions. In addition, chlorinated HANs with lower number of chlorine atom including MCAN and DCAN were found as intermediates of DCAN and TCAN degradation, respectively.
采用真空紫外光（VUV，185nm+254nm）与紫外光（UV，仅 254nm）对比研究了水中卤乙腈（HANs，具有高致癌性的含氮消毒副产物）的光降解。研究了一氯乙腈（MCAN）、二氯乙腈（DCAN）、三氯乙腈（TCAN）和二溴乙腈（DBAN）这几种 HANs。考察了 VUV 下气体吹扫和中间产物的形成的影响。结果表明，VUV 下 HANs 的还原假一级速率常数比 UV 下约提高了 2-7 倍。VUV 和 UV 下的降解效率顺序为 MCAN<DCAN<TCAN<DBAN。VUV 下各 HANs 的降解效率均高于混合 HANs，表明 HANs 之间存在竞争作用。在氮气吹扫下，混合 HANs 的去除速率常数比曝气条件下分别高 34.4、34.9、10.1 和 3.8 倍，对于 MCAN、DCAN、TCAN 和 DBAN。HANs 的主要降解机制取决于 HANs 种类。HANs 的降解中间体，如 2-氯丙腈、2,2-二甲基丙腈和富马腈，是通过取代、加成和聚合反应产生的。此外，发现具有较低氯原子数的氯化 HANs，如 MCAN 和 DCAN，分别为 DCAN 和 TCAN 降解的中间体。
