Department of Chemistry, Curtin Water Quality Research Centre, Curtin University, GPO Box U1987, Perth, Western Australia 6845, Australia; School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea.
School of Earth Sciences and Environmental Engineering, Gwangju Institute of Science and Technology (GIST), Gwangju 61005, Republic of Korea.
Water Res. 2022 Jul 15;220:118515. doi: 10.1016/j.watres.2022.118515. Epub 2022 Apr 29.
Chlorine dioxide (ClO) applications to drinking water are limited by the formation of chlorite (ClO) which is regulated in many countries. However, when ClO is used as a pre-oxidant, ClO can be oxidized by chlorine during subsequent disinfection. In this study, a kinetic model for the reaction of chlorine with ClO was developed to predict the fate of ClO during chlorine disinfection. The reaction of ClO with chlorine was found to be highly pH-dependent with formation of ClO and ClO in ultrapure water. In presence of dissolved organic matter (DOM), 60-70% of the ClO was transformed to ClO during chlorination, while the in situ regenerated ClO was quickly consumed by reaction with DOM. The remaining 30-40% of the ClO first reacted to ClO which then formed chlorine from the DOM-ClO reaction. Since only part of the ClO was transformed to ClO, the sum of the molar concentrations of oxychlorine species (ClO + ClO) decreased during chlorination. By kinetic modelling, the ClO concentration after 24 h of chlorination was accurately predicted in synthetic waters but was largely overestimated in natural waters, possibly due to a ClO decay enhanced by high concentrations of chloride and in situ formed bromine from bromide. Understanding the chlorine-ClO reaction mechanism and the corresponding kinetics allows to potentially apply higher ClO doses during the pre-oxidation step, thus improving disinfection byproduct mitigation while keeping ClO, and if required, ClO below the regulatory limits. In addition, ClO was demonstrated to efficiently degrade haloacetonitrile precursors, either when used as pre-oxidant or when regenerated in situ during chlorination.
二氧化氯（ClO）在饮用水中的应用受到限制，因为其会形成亚氯酸盐（ClO），许多国家都对其进行了管制。然而，当 ClO 用作预氧化剂时，ClO 可在后续消毒过程中被氯气氧化。在这项研究中，开发了一种用于预测 ClO 在氯消毒过程中命运的氯气与 ClO 反应动力学模型。研究发现，ClO 与氯气的反应高度依赖于 pH 值，在超纯水中会形成 ClO 和 ClO。在溶解有机物（DOM）存在的情况下，60-70%的 ClO 在氯化过程中转化为 ClO，而原位再生的 ClO 很快与 DOM 反应而消耗。剩余的 30-40%的 ClO 首先与 ClO 反应，然后由 DOM-ClO 反应形成氯气。由于只有部分 ClO 转化为 ClO，因此在氯化过程中氧氯物种（ClO + ClO）的总摩尔浓度降低。通过动力学模拟，可以准确预测合成水中氯化 24 小时后的 ClO 浓度，但在天然水中则存在较大的高估，这可能是由于高浓度的氯离子和溴化物原位生成的溴增强了 ClO 的衰减。了解氯-ClO 反应机制及其相应动力学，可在预氧化步骤中潜在地应用更高剂量的 ClO，从而在保持 ClO 和（如果需要）ClO 低于监管限制的情况下，改善消毒副产物的缓解。此外，ClO 被证明可以有效地降解卤乙腈前体，无论是用作预氧化剂还是在氯化过程中原位再生时。
