Xu Bohui, Deng Lin, Zhang Shizheng, Luo Wei, Hu Jun, Tan Chaoqun, Singh Rajendra Prasad
Department of Municipal Engineering, Southeast University, Nanjing, 211189, China.
Department of Municipal Engineering, Southeast University, Nanjing, 211189, China.
Environ Pollut. 2023 Feb 15;319:120972. doi: 10.1016/j.envpol.2022.120972. Epub 2022 Dec 27.
Chlorinated-halonitromethanes (Cl-HNMs) including chloronitromethane (CNM), dichloronitromethane (DCNM), and trichloronitromethane (TCNM) are nitrogenous disinfection by-products, which have high cytotoxicity and genotoxicity to human. This study aimed to investigate the degradation kinetic modeling and mechanism of Cl-HNMs under monochloramine activated by ultraviolet of 254 nm (UV/NHCl) treatment. The first-principle kinetic model of UV/NHCl process was developed to simulate Cl-HNMs degradation. Of note, the second-order rate constants of Cl-HNMs reacting with HO• (∼10 M s), Cl• (k = ∼10 M s, k = ∼10 M s), Cl• (k = ∼10 M s, k = ∼10 M s), ClO• (∼10-10 M s) and CO• (∼10-10 M s) were obtained by the first-principle kinetic model. Overall, Cl-HNMs degradation under UV/NHCl treatment was successfully predicted by the kinetic model under various conditions. It was found that UV (>60%) was dominant in Cl-HNMs degradation, followed by HO• (3.8%-24.5%), reactive chlorine species (RCS, 0.9%-28.8%) and CO• (0-26.1%). Among the contributions of RCS, Cl• and Cl• were main radicals in the degradation of CNM and DCNM, while ClO• was responsible for the abatement of TCNM. The minimum EE/O values under UV/NHCl treatment were approximately 30% lower than those under UV treatment. Finally, the possible degradation pathways were proposed, including hemolytic/heterolytic cleavage of Cl-HNMs by UV irradiation, hydrogen abstraction/electron transfer of CNM and DCNM and adduct reaction of TCNM by free radicals. This study based on the kinetic model is beneficial to predict and control the concentrations of Cl-HNMs under UV/NHCl treatment.
包括氯硝基甲烷（CNM）、二氯硝基甲烷（DCNM）和三氯硝基甲烷（TCNM）在内的氯化卤代硝基甲烷是含氮消毒副产物，对人体具有高细胞毒性和遗传毒性。本研究旨在探究254nm紫外线激活一氯胺（UV/NHCl）处理下氯化卤代硝基甲烷的降解动力学模型及机制。建立了UV/NHCl过程的第一性原理动力学模型以模拟氯化卤代硝基甲烷的降解。值得注意的是，通过第一性原理动力学模型获得了氯化卤代硝基甲烷与羟基自由基（10⁹M⁻¹s⁻¹）、氯原子（k₁ = ~10⁹M⁻¹s⁻¹，k₂ = ~10⁹M⁻¹s⁻¹）、氯原子（k₃ = ~10⁹M⁻¹s⁻¹，k₄ = ~10⁹M⁻¹s⁻¹）、次氯酸根（10¹⁰M⁻¹s⁻¹）和羰基自由基（~10¹⁰M⁻¹s⁻¹）反应的二级速率常数。总体而言，动力学模型成功预测了UV/NHCl处理下不同条件下氯化卤代硝基甲烷的降解情况。研究发现，紫外线（>60%）在氯化卤代硝基甲烷降解中起主导作用，其次是羟基自由基（3.8%-24.5%）、活性氯物种（RCS，0.9%-28.8%）和羰基自由基（0-26.1%）。在活性氯物种的贡献中，氯原子和氯原子是CNM和DCNM降解的主要自由基，而次氯酸根负责TCNM的去除。UV/NHCl处理下的最低电能消耗比（EE/O）值比紫外线处理下的低约30%。最后，提出了可能的降解途径，包括紫外线照射对氯化卤代硝基甲烷的均裂/异裂裂解、CNM和DCNM的氢提取/电子转移以及TCNM与自由基的加合反应。基于动力学模型的本研究有助于预测和控制UV/NHCl处理下氯化卤代硝基甲烷的浓度。
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