Abstract Sodium hypochlorite (NaOCl) is a widely used cleaning reagent for membrane separation processes to recover membrane permeability; however, the competitive interactions of different chlorine species with fouling layers have not been adequately elucidated. In this work, we investigated the pH-dependent diffusion of the active chlorine species and reactions involved in the consequent dissociation and/or destruction of the fouling layers. The hypochlorite conductivity and dynamic diffusion tests showed that an increase in pH facilitated the uneven and fast diffusion of active chlorine via relaxing the matrix structure of the fouling layer. Under the synergetic effects of oxidation, hydrolysis and hydraulic shearing, the enhanced diffusion resulted in an uneven but massive removal of the foulants rather than a layer-by-layer dissociation, leading to a higher membrane cleaning efficiency. Sodium dodecyl sulfate (SDS), an anionic surfactant, was added into the cleaning solution to further validate the diffusion-dependent cleaning mechanisms. With a faster diffusion process aided by SDS, the cleaning efficiency was significantly improved. These findings provide new insight into the chemical cleaning mechanisms, which are of great importance to the optimisation of cleaning efficiency for various membrane-based processes.

中文翻译：

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使用 NaOCl 重新研究膜清洁机制：试剂扩散的作用

摘要 次氯酸钠（NaOCl）是一种广泛用于膜分离过程中恢复膜渗透性的清洗剂；然而，不同氯种类与污垢层的竞争相互作用尚未得到充分阐明。在这项工作中，我们研究了活性氯物质的 pH 依赖性扩散以及随后的离解和/或污垢层破坏所涉及的反应。次氯酸盐电导率和动态扩散测试表明，pH 值的增加通过松弛污垢层的基体结构促进了活性氯的不均匀和快速扩散。在氧化、水解和水力剪切的协同作用下，增强的扩散导致污垢的不均匀但大量去除，而不是逐层解离，导致更高的膜清洗效率。将阴离子表面活性剂十二烷基硫酸钠 (SDS) 添加到清洁溶液中，以进一步验证依赖于扩散的清洁机制。通过SDS辅助的更快扩散过程，清洁效率显着提高。这些发现为化学清洗机制提供了新的见解，这对于优化各种基于膜的工艺的清洗效率非常重要。