Department of Energy, Environmental & Chemical Engineering , Washington University in St. Louis , Brauer Hall, 1 Brookings Dr. , St Louis , Missouri 63130 , United States.
Environ Sci Technol. 2018 Sep 4;52(17):9579-9594. doi: 10.1021/acs.est.8b02219. Epub 2018 Aug 23.
Photochemical reactions contribute to the transformation of contaminants and biogeochemically important substrates in environmental aquatic systems. Recent research has demonstrated that halogen radicals (e.g., Cl, Br, Cl, BrCl, Br) impact photochemical processes in sunlit estuarine and coastal waters rich in halides (e.g., chloride, Cl, and bromide, Br). In addition, halogen radicals participate in contaminant degradation in some engineered processes, including chlorine photolysis for drinking water treatment and several radical-based processes for brine and wastewater treatment. Halogen radicals react selectively with substrates (with bimolecular rate constants spanning several orders of magnitude) and via several potential chemical mechanisms. Consequently, their role in photochemical processes remains challenging to assess. This review presents an integrative analysis of the chemistry of halogen radicals and their contribution to aquatic photochemistry in sunlit surface waters and engineered treatment systems. We evaluate existing data on the generation, speciation, and reactivity of halogen radicals, as well as experimental and computational approaches used to obtain this data. By evaluating existing data and identifying major uncertainties, this review provides a basis to assess the impact of halogen radicals on photochemical processes in both saline surface waters and engineered treatment systems.
光化学反应导致环境水系统中污染物和生物地球化学重要基质的转化。最近的研究表明，卤族自由基（如 Cl、Br、Cl、BrCl、Br）影响富含卤化物（如氯化物 Cl 和溴化物 Br）的光照河口和沿海水体中的光化学过程。此外，卤族自由基还参与一些工程处理过程中的污染物降解，包括饮用水处理中的氯光解以及盐水和废水处理中的几种基于自由基的过程。卤族自由基与底物选择性反应（具有跨越几个数量级的双分子速率常数），并通过几种潜在的化学机制进行反应。因此，它们在光化学过程中的作用仍然难以评估。本综述综合分析了卤族自由基的化学性质及其在光照地表水和工程处理系统中的光化学中的贡献。我们评估了卤族自由基的生成、形态和反应性的现有数据，以及用于获取这些数据的实验和计算方法。通过评估现有数据和确定主要不确定性，本综述为评估卤族自由基对盐地表水和工程处理系统中光化学过程的影响提供了基础。
