Chow Héline, Pham Anh Le-Tuan
Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada.
Department of Civil and Environmental Engineering, University of Waterloo, Waterloo, ON N2L 3G1, Canada.
Water Res. 2021 Jun 1;197:117074. doi: 10.1016/j.watres.2021.117074. Epub 2021 Mar 19.
One of the biggest issues in electrocoagulation (EC) water treatment processes is electrode fouling, which can cause decreased coagulant production, increased ohmic resistance and energy consumption, and reduced contaminant removal efficiency, among other operational problems. While it has been suggested that switching the current direction intermittently (i.e., polarity reversal, PR) can help mitigate electrode fouling, conflicting results about the utility of this approach have been reported in the literature. The objective of this study was to systematically investigate the effects of PR frequency and current density on the performance of Fe-EC and Al-EC. It was found that operating Fe-EC under the PR mode reduced neither electrode fouling nor energy consumption. Notably, the Faradaic efficiency (ϕ) in Fe-EC decreased with increasing PR frequency; ϕ was as low as 10% when a PR frequency of 0.5 minutes was employed. Unlike Fe-EC, operating Al-EC under the PR mode resulted in high coagulant production efficiencies, reduced energy consumption, and diminished electrode fouling. In addition to comparing PR-EC and DC-EC, a novel strategy to minimize electrode fouling was investigated. This strategy involved operating Fe DC-EC and Al DC-EC with a Ti-IrO cathode, whose fouling by Ca- and Mg-containing minerals could be readily avoided by periodically switching the current direction.
电凝（EC）水处理工艺中最大的问题之一是电极污染，这可能导致混凝剂产量下降、欧姆电阻和能耗增加以及污染物去除效率降低等其他运行问题。虽然有人提出间歇性地改变电流方向（即极性反转，PR）有助于减轻电极污染，但文献中报道了关于这种方法效用的相互矛盾的结果。本研究的目的是系统地研究PR频率和电流密度对铁-EC和铝-EC性能的影响。研究发现，在PR模式下运行铁-EC既不能减少电极污染也不能降低能耗。值得注意的是，铁-EC中的法拉第效率（ϕ）随着PR频率的增加而降低；当采用0.5分钟的PR频率时，ϕ低至10%。与铁-EC不同，在PR模式下运行铝-EC可提高混凝剂生产效率、降低能耗并减少电极污染。除了比较PR-EC和DC-EC外，还研究了一种使电极污染最小化的新策略。该策略包括使用钛-氧化铱阴极运行铁DC-EC和铝DC-EC，通过定期改变电流方向可以很容易地避免含钙和镁矿物质对其造成污染。
