State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Haidian District, Beijing 100085, China; University of Chinese Academy of Sciences, Beijing 100049, China; Jiangsu Collaborative Innovation Center of Technology and Material of Water Treatment, Suzhou University of Science and Technology, Suzhou 215009, China.
State Key Laboratory of Environmental Aquatic Chemistry, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, 18 Shuangqing Road, Haidian District, Beijing 100085, China.
Water Res. 2022 Sep 1;223:118966. doi: 10.1016/j.watres.2022.118966. Epub 2022 Aug 9.
Electrode passivation is the most challenging technical problem in electrocoagulation (EC) water treatment process, but research on understanding and mitigating passivation evolution are still lacking. Herein, homogenization of current density (CD) distribution was found to be a critical factor in alleviating the anode passivation during EC process. Decreasing electrode area decelerated the growth of passivation layer on anode through homogenizing CD distribution, which was quantified by the ratios of CD distributed at the electrode edges and centers. When aluminum anode area decreased from 8 cm to 2 cm with a constant CD, the homogenization degree increased by 24.0%, and passivation was reduced by 24.3%. The depth profiles of passivated anodes confirmed the inhomogeneity of the anode passivation. Thicker passivation layers were observed at edges due to high CD distributions, which originated from the "edge effect" of electric field distribution between parallel plate electrodes. A facile strategy to homogenize CD distribution by splitting electrodes into smaller electrodes is then proposed for passivation mitigation, which can save energy consumption by 21.8% with unchanged removal efficiency. This study provides a unique insight into anode passivation mitigation and a feasible electrode design in EC.
电极钝化是电絮凝（EC）水处理过程中最具挑战性的技术问题，但对理解和减轻钝化演变的研究仍然不足。本研究发现，均匀化电流密度（CD）分布是缓解 EC 过程中阳极钝化的关键因素。通过均匀化 CD 分布来减少电极面积会减缓阳极钝化层的生长，这可以通过 CD 在电极边缘和中心的分布比例来量化。当铝阳极面积从 8cm 减小到 2cm 时，CD 保持不变，均匀度提高了 24.0%，钝化减少了 24.3%。钝化阳极的深度剖面证实了阳极钝化的不均匀性。由于 CD 分布较高，在边缘处观察到较厚的钝化层，这源于平行板电极之间电场分布的“边缘效应”。然后提出了一种将电极分割成更小电极以均匀化 CD 分布的简便策略，用于减轻钝化，同时在去除效率不变的情况下可节省 21.8%的能耗。本研究为阳极钝化缓解提供了独特的见解，并为 EC 中的可行电极设计提供了思路。
