Oxidation resistance of reduced graphene oxide forward osmosis membranes against hexavalent chromium

Reduced graphene oxide (RGO) forward osmosis (FO) membranes have emerged as promising candidates for efficient wastewater management and osmotic energy harvesting, due to their enhanced chemical stability and superior FO performance for low-energy waste brine treatments, such as volume reduction in oxidative chromium brine for cost-effective disposal. This study examines the oxidation resistance of RGO forward osmosis membranes against chromate Cr(VI). Our findings reveal that both the water flux and the reverse salt flux of RGO membranes are suppressed, accompanying an enhanced reverse flux selectivity after exposure to an acidic or neutral medium of Cr(VI) (pH 2.0–7.0). After exposure to a basic Cr(VI) medium of pH 10.0, an increase in reverse salt flux and a reduction in reverse flux selectivity are observed, which could be due to the synergistic effect of both pH and ionic solutes on the RGO membranes, not due to Cr(VI) oxidation. Remarkably, after the removal of chromate with a full rinse, the RGO membranes show a nearly complete recovery of their FO performance.