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 x 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 similar to 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 mu g 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.