Mechanistic Insight into the Spatial Scale of Nonuniform Oxidation of Micropollutants in Reactive Electrochemical Membranes for Water Purification

A reactive electrochemical membrane (REM) has been identifiedasan excellent platform in micropolluted water purification due to itsrapid mass transfer capability. Unlike traditional flow-by systems,the convection-enhanced REM systems activate the REM's innerreaction sites, potentially imparting a spatially variable reactivity.Therefore, we explored the spatial scale of micropollutant oxidationin REM. Theoretical and experimental evidence demonstrated that anREM might feature nonuniform oxidation activity along its reactiondepth (about hundreds of micrometers). That is, the zone generating (OH)-O-& BULL; was located within a few micrometers beneath theREM surface, i.e., less than 1% of its reaction depthdue to the rapid overpotential/potential drop in the REM. The nonuniformreactive character might render the REM of a strong direct electrontransfer ability, enabling rapid removal of electron-rich micropollutantseven at low potentials. However, unsatisfactory removal of electron-poormicropollutants has been observed, and a higher potential was requiredto prompt the generation of (OH)-O-& BULL;. These results providein-depth insight into the spatial scale of nonuniform oxidation ofmicropollutants in REM, contributing to the analysis of micropollutantoxidation mechanisms and the optimization of the design and operationof REM modules for cost-effective water purification.