Marine Engineering College, Dalian Maritime University, Dalian, 116026, China.
Environmental Science and Engineering College, Dalian Maritime University, Dalian, 116026, China.
Chemosphere. 2021 Oct;280:130669. doi: 10.1016/j.chemosphere.2021.130669. Epub 2021 Apr 27.
The presence of hydrogen peroxide (HO) in ozonation process can resist the formation of carcinogenic bromate (BrO¯) efficiently, and the bromate depression is closely related with background water qualities, especially in high bromide-containing seawater. In this study, the freshwater and seawater were selected to investigate the effects of HO on ozone (O) decomposition kinetics, bromide transformation and bromate depression, and the evolutions of BrO¯ under different scavengers were explored to speculate the primary bromate formation pathways. The results showed that the initial O half-live period (t-O) in seawater was only one-sixth of that in freshwater, and its attenuation rate increased analogously with the increase of HO concentration in both freshwater and seawater. The HO could promote the formation of BrO¯ via hydroxyl radical (•OH) based bromate pathways, nevertheless higher concentration of HO facilitated the reduction of HOBr/OBr¯ back to Br¯, resulting in 87.0% and 73.2% of BrO¯ retardment in freshwater and seawater, respectively. The suppression ratios of BrO¯ were up to 48.4% and 35.3% in freshwater with the addition of •OH and •O¯ scavengers, and the corresponding depressions in seawater decreased to 35.3% and 12.7%, indicating that •OH was dominant on bromate formation when the concentration of residual ozone was adequate to generate some bromine intermediates, meanwhile HO and •O¯ functioned as the key reductants for bromate depression. Based on these results, the Br¯ transformation mechanisms via O, •OH, HO, and •O¯ reactions were speculated, and the feasibility of HO-ozonation was verified for the treatment of high Br¯-containing seawater.
臭氧氧化过程中过氧化氢（HO）的存在可以有效地抑制致癌溴酸盐（BrO¯）的形成，溴酸盐的抑制与背景水质密切相关，尤其是在高溴化物含量的海水中。本研究选择淡水和海水，考察 HO 对臭氧（O）分解动力学、溴化物转化和溴酸盐抑制的影响，探讨不同猝灭剂下 BrO¯的演变，推测主要的溴酸盐形成途径。结果表明，海水中的初始 O 半衰期（t-O）仅为淡水中的六分之一，其衰减速率随淡水和海水中 HO 浓度的增加而呈线性增加。HO 可以通过羟基自由基（•OH）基溴酸盐途径促进 BrO¯的形成，但较高浓度的 HO 有利于将 HOBr/OBr¯还原回 Br¯，导致淡水和海水中 BrO¯的抑制率分别达到 87.0%和 73.2%。在添加•OH 和•O¯猝灭剂的淡水中，BrO¯的抑制率高达 48.4%和 35.3%，而在海水中的抑制率分别降低至 35.3%和 12.7%，表明当剩余臭氧浓度足以生成一些溴化物中间体时，•OH 是溴酸盐形成的主要因素，同时 HO 和•O¯是溴酸盐抑制的关键还原剂。基于这些结果，推测了 O、•OH、HO 和•O¯反应的 Br¯转化机制，并验证了 HO-臭氧氧化法处理高 Br¯含量海水的可行性。
