Hydrogen manganese oxide-induced construction of polyaniline nano-cone array composite membrane for highly efficient acid recovery via selective electrodialysis

The discharge of acidic wastewater containing high concentrations of heavy metal ions and inorganic acids poses severe environmental risks. Selectrodialysis (SED) based on monovalent-selective cation exchange membranes (MSCEMs) offers a promising approach to recovery acid from such streams. However, the performance of MSCEMs is limited by the fundamental selectivity-permeability trade-off. This report develops a novel composite MSCEM prepared by blending hydrogen manganese oxide (HMO) with proton transport channels with sulfonated poly (dimethyl phenylene oxide), followed by in situ self-polymerization to generate a positively charged surface layer. This enables a dual mechanism of size sieving and electrostatic repulsion that ensures high proton/divalent cation selectivity. The MSCEM developed in this work exhibits a high proton selectivity of 112.5 ± 3.0 in HCl/FeCl 2 mixture, which is approximately 19 times higher than that of the commercial MSCEM. Additionally, the HMO on the membrane surface guides the formation of a V-shaped polyaniline transport channels layer, enabling reduced proton transport resistance and contributing to a proton flux of 4.25 ± 0.2 mol m −2  h −1 . The prepared MSCEM also demonstrates universal H-permselectivity across various coexisting cation systems (Fe 2+ /Cu 2+ /Ni 2+ ) and anion systems (SO 4 2− /Cl − ). The novel MSCEM with composite structure exhibited superior proton conductivity and permselectivity, thus paving the way for efficient utilization of waste acid resources via SED.