Electrically tuning low-pressure membrane surface charge for highly efficient Cr(VI) removal from drinking water

Ionic contaminants, especially heavy metal ions, are a significant challenge for ensuring the safety and quality of drinking water. Electrosorption and membrane separation are effective technologies to remove ionic contaminants; however, the constant electricity demand and lack of selectivity limit their further application. In this study, a low-pressure membrane with an electrically tuning surface charge was developed for the selective and efficient removal of hexavalent chromium (Cr(VI)) from water. Poly(vinyl ferrocene) (PVF) was used to fabricate an electrically responsive interface, and an activated carbon felt (ACF) was applied as a conductive substrate. Fluorescence characterization was then used to further highlight its redox properties and the tunability of its surface charge. The activated PVF-based electro-responsive adsorptive membrane (PERAM) showed an excellent adsorption capacity and selectivity for Cr(VI) during single-pass filtration. Notably, regeneration was achieved by the application of a reversed electric potential without the need for additional chemical additives. The Cr(VI) effluent concentration was reduced to <0.05 mg/L at a high flux of 424 L/m 2 ·h, and it had a treatment capacity of greater than 5140 L/m 2 due to effective activation and regeneration. The electrostatic force changes between the PVF and Cr(VI) at different potentials was the key mechanism that allowed for the rapidly reversible adsorption-desorption of Cr(VI) according to the results of the density functional theory (DFT) calculations and molecular dynamics (MD) simulations.