Electrochemical activation of peroxymonosulfate in cathodic micro-channels for effective degradation of organic pollutants in wastewater

Abstract

Persulfate may be electrochemically activated into sulfate radicals (SO4•−) or hydroxyl radicals (•OH) by accepting electrons on cathode. Although electro-activated persulfate has displayed good performance in oxidation of organic pollutants in wastewater, both yield and availability of radicals are still limited because the electrostatic repulsion resists the contact between persulfate anions and cathode. In this study, a flow-through cathode (FTC) with well-ordered micro-channels was fabricated via carbonization of wood. The solution containing persulfate ions flowed through these micro-channels and then activation of persulfate was confined and performed in the micro-channels, which enhanced remarkably the contact between persulfate ions and cathode. Under the residence time of 10 min and other optimized conditions, the decomposition rate of persulfate in FTC displayed 3.78 folds of enhancement compared with that on a flow-by cathode (FBC). EPR signal of •OH produced in FTC was also higher distinctly than that on FBC. The average removal rates of phenol and TOC in FTC were 97.9 % and 39.6 %, respectively, which were 2.61 times and 2.57 times as much as that on FBC. Cycling experiments indicated that this FTC had good stability. Therefore, activating persulfate in FTC is an efficient strategy to enhance the yield and availability of radicals.