Department of Chemical & Petroleum Engineering, University of Calgary, 2500 University Dr NW, Calgary, AB T2N 1N4, Canada.
Department of Chemical & Petroleum Engineering, University of Calgary, 2500 University Dr NW, Calgary, AB T2N 1N4, Canada.
Water Res. 2020 Dec 15;187:116433. doi: 10.1016/j.watres.2020.116433. Epub 2020 Sep 16.
Treating water and wastewater is energy-intensive, and traditional methods that require large amounts of chemicals are often still used. Electrocoagulation (EC), an electrochemical treatment technology, has been proposed as a more economically and environmentally sustainable alternative. In EC, sacrificial metal electrodes are used to produce coagulant in-situ, which offers many benefits over conventional chemical coagulation. However, material precipitation on the electrodes during long term operation induces a passivating effect that decreases treatment performance and increases power requirements. Overcoming this problem is considered to be the greatest challenge facing the development of EC. In this critical review, the studies that have examined the nature of electrode passivation, and its effect on treatment performance are considered. A fundamental approach is used to examine the association between passivation and faradaic efficiency, a surrogate for EC performance. In addition, the strategies that have been proposed to remove or avoid passivation are reviewed, including aggressive ion addition, AC current operation, polarity reversal, ultrasonication, and mechanical cleaning of the electrodes. It is concluded that the success of implementing each method is dependent on critical operating parameters, and careful consideration should be taken when designing an EC system based on the phenomena discussed in this article. In conclusion, this review provides insight into passivation mechanisms, delivers guidelines for sustaining high treatment performance, and offers an outlook for the future development of EC.
处理水和废水是能源密集型的，传统的大量使用化学物质的方法仍然经常被使用。电化学混凝（EC）作为一种更经济和环境可持续的替代方法，是一种电化学处理技术，已经被提出。在 EC 中，牺牲性金属电极用于原位产生混凝剂，这比传统的化学混凝有许多优势。然而，在长期运行过程中，材料在电极上的沉淀会产生钝化效应，从而降低处理性能并增加功率需求。克服这个问题被认为是 EC 发展面临的最大挑战。在这篇重要的综述中，考虑了研究电极钝化的性质及其对处理性能的影响。采用一种基本方法来考察钝化与法拉第效率（EC 性能的替代指标）之间的关系。此外，还回顾了提出的去除或避免钝化的策略，包括添加侵蚀性离子、交流电操作、极性反转、超声波和电极的机械清洁。结论是，每种方法的成功实施都取决于关键的操作参数，在基于本文讨论的现象设计 EC 系统时应慎重考虑。总之，本综述提供了对钝化机制的深入了解，为维持高处理性能提供了指导，并对 EC 的未来发展提供了展望。
