Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong.
Chemosphere. 2020 Dec;260:127644. doi: 10.1016/j.chemosphere.2020.127644. Epub 2020 Jul 18.
This study investigated the degradation of eight aliphatic halogenated contaminants (one brominated flame retardant and seven disinfection by-products) in synthetic drinking water by the UVA/TiO and UVA/Cu-TiO processes. The degradation rate constants of 2,2-bis(bromomethyl)-1,3-propanediol and trichloromethane in the UVA/Cu-TiO process were 10.1 and 1.29 times, respectively, higher than those in the UVA/TiO process. In contrast, the degradation rate constants of dichloroacetaldehyde, monochloroacetonitrile, monobromoacetonitrile and dibromonitromethane in the UVA/Cu-TiO process were 8.15, 2.33, 2.84 and 1.80 times, respectively, lower than those in the UVA/TiO process. The degradation rate constants of monobromonitromethane and dichloronitromethane were comparable in the two processes. The relationships between the degradation rate constants and the structural characteristics of the selected contaminants were examined to explain the different degradation efficacies of the contaminants in the two processes. As suggested by a quantitative structure-activity relationship (QSAR) model, the UVA/TiO process favored the degradation of contaminants with more polar electron-withdrawing moieties and higher degrees of chlorination. While the UVA/Cu-TiO process favored the degradation of hydrophilic unsaturated contaminants with multiple bonds. The concentrations of the reactive species (e.g., HO and e) generated in the two photocatalytic processes were quantified using competition kinetics. The UVA/Cu-TiO process generated >10 times higher concentrations of HO than the UVA/TiO process, suggesting that the former process was more suitable for the degradation of contaminants that are reactive towards HO, while e and e-derived superoxide radicals were non-negligible contributors to contaminant degradation in the UVA/TiO process.
本研究考察了 UVA/TiO 和 UVA/Cu-TiO 工艺对合成饮用水中 8 种脂肪族卤代污染物（一种溴代阻燃剂和 7 种消毒副产物）的降解。在 UVA/Cu-TiO 工艺中，2,2-双（溴甲基）-1,3-丙二醇和三氯甲烷的降解速率常数分别比 UVA/TiO 工艺高 10.1 和 1.29 倍。相比之下，在 UVA/Cu-TiO 工艺中，二氯乙腈、一氯乙腈、一溴乙腈和二溴硝基甲烷的降解速率常数分别比 UVA/TiO 工艺低 8.15、2.33、2.84 和 1.80 倍。两种工艺中二溴硝基甲烷和二氯硝基甲烷的降解速率常数相当。考察了所选污染物的降解速率常数与结构特征之间的关系，以解释两种工艺中污染物降解效率的差异。如定量构效关系（QSAR）模型所示，UVA/TiO 工艺有利于降解具有更多极性吸电子基团和更高氯化度的污染物。而 UVA/Cu-TiO 工艺有利于降解具有多个双键的亲水性不饱和污染物。使用竞争动力学量化了两种光催化过程中产生的活性物质（如 HO 和 e）的浓度。UVA/Cu-TiO 工艺产生的 HO 浓度比 UVA/TiO 工艺高>10 倍，表明前者工艺更适合降解对 HO 具有反应性的污染物，而 e 和 e 衍生的超氧自由基对 UVA/TiO 工艺中污染物的降解也有不可忽视的贡献。
