Efficient acid/alkali recovery enabled by only one negatively charged microporous polymer membrane

Abstract

The recovery of acid/base from industrial wastewater via membrane technology is energy efficient and has a low carbon footprint, while demanding high‐performing ion exchange membranes. It remains a grand challenge for ion exchange membranes, enabling concomitantly fast H+/OH− transport and high ion selectivity. This article presents a negatively charged microporous polymer membrane, a sulfonated polyxanthene membrane, which has intrinsic micropore channels for H+/OH− permeation, and we find that highly selective H+ and OH− transport can be acquired with the same membrane. This membrane exhibits a high H+/Fe2+ selectivity of 617 (6.3 times that of the commercial CIMS membrane) in acid recovery and a very high OH−/WO42− selectivity of 649 (the highest value ever reported) in alkali recovery while maintaining comparable H+/OH− transport rate. The results highlight the importance of hydrophilic micropores as ion‐selective channels in constructing high‐performing ion exchange membranes for resource recovery.