State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, PR China.
Water Res. 2017 Mar 15;111:288-296. doi: 10.1016/j.watres.2017.01.018. Epub 2017 Jan 11.
Bromate (BrO) is a possible human carcinogen regulated worldwide at a strict standard of 10 μg/L in drinking water. Removal of BrO by advanced reduction processes (ARPs) has attracted much attention due to its high reduction efficiency and easier combination with ultraviolet (UV) disinfection. In this study, we employed a UV/sulfite process to degrade BrO and studied the effects of UV lamp, sulfur(IV) concentration, and pH on effectiveness of the system in degrading BrO. Low-pressure UV lamps (UV-L) instead of medium-pressure UV lamps (UV-M) were selected because of the high ultraviolet-C (UV-C) efficiency of UV-L. The increased sulfur(IV) concentration is proportionally correlated with enhanced degradation kinetics. BrO reduction was improved by increasing pH when pH is within 6.0-9.0, and principal component analysis demonstrated that pH is the most influential factor over sulfur(IV) concentration and type of UV lamp. Degradation mechanisms at different pH levels were subsequently investigated. Results showed that the reduction reactions are induced by hydrated electron (e) at pH > 9.0, by H at pH 4.0, and by both e and H at pH 7.0. Effective quantum efficiency for the formation of e and H in the photocatalytic systems was determined to be 0.109 ± 0.001 and 0.034 ± 0.001 mol E, respectively. Furthermore, mass balance calculation of bromine and sulfur at pH 7 showed that bromide, sulfate and possibly dithionate ions were the major products, and a degradation pathway was proposed accordingly. Moreover, UV/sulfite processes could reduce the initial bromate concentration of 0.1 mM by 82% and 95% in the presence and absence of O in tap water respectively, and 99% in the absence of O in deionized water within 20 min at pH 9.0 and 2.0 mM sulfur (IV).
溴酸盐（BrO）是一种可能的人类致癌物，在世界范围内的饮用水标准中严格规定为 10μg/L。由于其具有较高的还原效率，并且更容易与紫外线（UV）消毒相结合，因此通过先进的还原工艺（ARPs）去除 BrO 引起了广泛关注。在这项研究中，我们采用 UV/亚硫酸盐工艺来降解 BrO，并研究了 UV 灯、亚硫酸盐浓度和 pH 值对该系统降解 BrO 的效果的影响。选择低压 UV 灯（UV-L）而不是中压 UV 灯（UV-M）是因为 UV-L 具有较高的紫外线-C（UV-C）效率。随着亚硫酸盐浓度的增加，降解动力学也相应增强。当 pH 值在 6.0-9.0 范围内时，增加 pH 值会提高 BrO 的还原效果，主成分分析表明 pH 值是比亚硫酸盐浓度和 UV 灯类型更具影响力的因素。随后研究了不同 pH 值水平下的降解机制。结果表明，在 pH 值>9.0 时，还原反应由水合电子（e）引发，在 pH 值为 4.0 时由 H 引发，在 pH 值为 7.0 时由 e 和 H 共同引发。在光催化系统中形成 e 和 H 的有效量子效率分别确定为 0.109±0.001 和 0.034±0.001 mol E。此外，在 pH 值为 7 时，溴和硫的质量平衡计算表明，溴化物、硫酸盐和可能的连二硫酸盐是主要产物，并相应地提出了一种降解途径。此外，在自来水中存在和不存在 O 的情况下，UV/亚硫酸盐工艺可以在 20 分钟内将初始溴酸盐浓度为 0.1mM 的水样分别降低 82%和 95%，在去离子水中不存在 O 的情况下，在 pH 值为 9.0 和 2.0mM 亚硫酸盐（IV）的情况下，溴酸盐的去除率可达到 99%。
