Flow-Through Electrochemical Activation of Persulfate for Efficient Wastewater Treatment using Ti4O7 Reactive Electrochemical Membranes

Herein, a flow-through reactive electrochemical membrane (REM) system was reported for the complete activation of S2O82– upon a single-pass through the Ti4O7 REM cathode with less than 10 s of residence time. The kinetic constant for S2O82– activation was observed at 21–109 × 10–5 m s–1, which is 1–2 orders of magnitude higher than the reported conventional batch/flow-by electrochemical systems even with the addition of activators. The Ti4O7 REM electrode exhibited good stability in activating S2O82–, and the efficiency decreased by only ∼5% after 5 h of continuous operation due to scaling in a wastewater treatment plant (WWTP) effluent sample. As a proof-of-concept, the REM–persulfate system, i.e., integration of both anodic electrooxidation and cathodic persulfate-based advanced oxidation process, was successfully applied to treat both antibiotics-spiked WWTP effluent and reverse osmosis (RO) concentrate of pretreated coking wastewater. A single-pass of the REM–persulfate system achieved over 95% removal of 6 antibiotics (each 10 μg L–1) from WWTP effluents. As compared with the REM system without persulfate, the addition of 10 mM S2O82– for treating RO concentrate of pretreated coking wastewater resulted in a significant increase in total organic carbon removal from 51.5 to 78.9%. However, it also resulted in the formation of chlorinated byproducts, including ClO3–, ClO4–, and absorbable organic chlorine. Techno-economic analysis with an RO concentrate of pretreated coking wastewater showed that the REM–persulfate system featured a 50% lower initial capital cost than the REM system without persulfate. Results of this study indicate the REM–persulfate system may be potentially a promising wastewater treatment technology.