State Key Laboratory of Urban Water Resource and Environment, School of Environment, Harbin Institute of Technology, Harbin 150090, China.
State Key Laboratory of Heavy Oil Processing, State Key Laboratory of Petroleum Pollution Control, China University of Petroleum-Beijing, Beijing 102249, China.
Sci Total Environ. 2022 Dec 20;853:158345. doi: 10.1016/j.scitotenv.2022.158345. Epub 2022 Aug 28.
The UV/chlorine (UC) system is a homogeneous advanced oxidation process with increasing attention in water decontamination. The addition of TiO is a newly found strategy to enhance the generation of hydroxyl radical (HO) and chlorine radical (Cl) in the UC system. However, the crucial role of chlorine oxide radical (ClO, generated by the reactions of HO and Cl with chlorine) on pollutant degradation, has not been noticed in UV/chlorine/TiO (UCT), the heterogeneous photocatalytic system for chlorine activation. Herein, the role of ClO in UCT was clarified through quenching experiments combined with model simulations during carbamazepine degradation. Tert-butyl alcohol completely inhibited while bicarbonate only partly suppressed carbamazepine degradation in UCT, indicating the important role of ClO. The second-order reaction rate constant between ClO and carbamazepine (k) was fitted to be (1.21 ± 0.08) × 10 M s by the kinetic model, which avoided the influence of carbonate radical (CO), whose contribution couldn't be excluded during k determination in commonly used competitive kinetic methods with bicarbonate. With the obtained k, model simulation suggested that ClO contributed about 50 % to carbamazepine degradation in UCT, and its concentration was less affected under varied conditions (solution pH, chlorine, bicarbonate, and chloride concentration) to keep an efficient carbamazepine degradation. On the contrary, pollutant degradation dominated by HO in UCT was largely inhibited with the increase of pH, chlorine, and bicarbonate concentration. In addition to the promotion of degradation efficiency, less disinfection byproducts and lower energy requirement were found in UCT compared with UC. Furthermore, UCT could maintain satisfactory degradation efficiency and energy saving in ground water and surface water samples. Results of this study unraveled the crucial role of ClO for pollutant degradation in UCT, and showed bright prospects and great potentials of the system in water treatment.
UV/氯（UC）系统是一种均相高级氧化工艺，在水净化方面受到越来越多的关注。添加 TiO 是一种新发现的策略，可以增强 UC 系统中羟基自由基（HO）和氯自由基（Cl）的生成。然而，在 UV/氯/TiO（UCT）即用于氯活化的多相光催化系统中，尚未注意到氯氧化物自由基（ClO，由 HO 和 Cl 与氯反应生成）在污染物降解中的关键作用。在此，通过降解过程中的猝灭实验和模型模拟，阐明了 ClO 在 UCT 中的作用。叔丁醇完全抑制了 UCT 中卡马西平的降解，而碳酸氢盐仅部分抑制了卡马西平的降解，表明 ClO 的重要作用。ClO 与卡马西平之间的二级反应速率常数（k）通过动力学模型拟合为（1.21±0.08）×10 M s，该模型避免了在常用的竞争动力学方法中使用碳酸氢盐进行 k 测定时排除碳酸根自由基（CO）的影响。根据获得的 k 值，模型模拟表明，ClO 在 UCT 中对卡马西平的降解贡献约为 50%，在不同条件（溶液 pH 值、氯、碳酸氢盐和氯化物浓度）下，ClO 的浓度变化较小，以保持高效的卡马西平降解。相比之下，在 UCT 中以 HO 为主导的污染物降解在 pH 值、氯和碳酸氢盐浓度增加时受到很大抑制。与 UC 相比，UCT 不仅提高了降解效率，还降低了消毒副产物的生成和能源需求。此外，UCT 在地下水和地表水样品中仍能保持令人满意的降解效率和节能效果。本研究结果揭示了 ClO 在 UCT 中污染物降解中的关键作用，并展示了该系统在水处理方面的广阔前景和巨大潜力。
