Key Laboratory of Drinking Water Science and Technology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China.
State Key Laboratory of Environmental Criteria and Risk Assessment, Chinese Research Academy of Environmental Sciences, Beijing 100012, China.
Water Res. 2023 Aug 1;241:120159. doi: 10.1016/j.watres.2023.120159. Epub 2023 May 31.
Aromatic polyamide (PA) based membranes are widely used for reverse osmosis (RO), but they can be degraded by free chlorine used for controlling the biofouling prior to RO treatment. Kinetics and mechanisms for the reactions of PA membrane model monomers, i.e., benzanilide (BA), and acetanilide (AC), with chlorine dioxide (ClO) were investigated in this study. Rate constants for the reactions of ClO with BA and AC at pH 8.3 and 21°C were determined to be (4.1±0.1) × 10 M s and (6.0±0.1) × 10 M s, respectively. These reactions are base assisted with a strong pH dependence. The activation energies of BA and AC degradation by ClO were 123.7 and 81.0 kJ mol, respectively. This indicates a relatively strong temperature dependence in the studied temperature range of 21-35 °C. The presence of bromide and natural organic matter does not promote the degradation of model monomers by ClO. BA was degraded by ClO via two pathways: (1) the attack on the anilide moiety with the formation of benzamide (major pathway) and (2) oxidative hydrolysis to benzoic acid (minor pathway). A kinetic model was developed to simulate the degradation of BA and formation of byproducts during ClO pretreatment, and simulations agree well with the experimental data. Half-lives of BA treated by ClO were 1-5 orders of magnitude longer than chlorine under typical seawater treatment conditions. These novel findings suggest the potential application of ClO for controlling biofouling ahead of RO treatment at desalination treatments.
芳香聚酰胺（PA）基膜广泛用于反渗透（RO），但它们可能会被 RO 处理前用于控制生物污堵的自由氯降解。本研究考察了 PA 膜模型单体，即苯甲酰胺（BA）和乙酰苯胺（AC）与二氧化氯（ClO）反应的动力学和机理。在 pH 8.3 和 21°C 下，ClO 与 BA 和 AC 的反应速率常数分别确定为（4.1±0.1）×10 M s 和（6.0±0.1）×10 M s。这些反应是碱辅助的，对 pH 有很强的依赖性。ClO 降解 BA 和 AC 的活化能分别为 123.7 和 81.0 kJ mol，这表明在研究的 21-35°C 温度范围内，温度对反应有较强的依赖性。溴化物和天然有机物的存在不会促进 ClO 对模型单体的降解。ClO 通过两种途径降解 BA：（1）对酰亚胺部分的攻击，形成苯甲酰胺（主要途径）和（2）氧化水解生成苯甲酸（次要途径）。建立了一个动力学模型来模拟 ClO 预处理过程中 BA 的降解和副产物的形成，模拟结果与实验数据吻合较好。在典型的海水处理条件下，ClO 处理 BA 的半衰期比氯长 1-5 个数量级。这些新发现表明，在海水淡化处理中，ClO 有望在 RO 处理前用于控制生物污堵。
