Tactfully introducing amphoteric group into electroactive membrane motivates highly efficient H₂O splitting for...

Membrane-based electro-deposition (MED) is an original process promising for reversible removal and recovery of toxic heavy metal ions from wastewater. The removal efficiency of heavy metal ions, however, was limited by the poor membrane surface H₂O splitting in the conventional ion exchange membrane (IEM). Inspired by the amphoteric interface-triggered ion exchange resin regeneration phenomenon in electro-deionization, herein we subtly introduced the amphoteric group into IEM as a proof of concept to solve the above bottleneck. By virtue of the "electronic porter" role of the amphoteric ^-₃OS-R-N(CH₃)₃⁺, the electron extraction from adsorbed H₂O could be accelerated, extending the H₂O splitting from the conventional membrane surface to the bulk membrane interior. Such an H₂O splitting extension favorably produced an intensified and well-modeled OH^- production region at the anodic side of IEM, enhancing the Ni²⁺ basic deposition accordingly. This special characteristic allowed our MED to realize a super-eminent metal ion removal rate (10.5 mol·h^-1·m^-2) along with an ultra-low specific energy consumption (0.1 kWh·mol^-1) for Ni²⁺ removal, which considerably surpassed those of state-of-the-art heavy metal ion removal processes reported yet. Further, the deposited Ni²⁺ could be in situ recovered in conjunction with the facile polarity reversal method. The amphoteric electroactive membrane with high H₂O splitting activity is expected to pave the path to engineering MED for efficient heavy metal ion removal and recovery.