Preparation of proton block and highly conductive AEM by creating PANI dominated and hydrophobicity ion channels for sulfuric acid enrichment

Abstract

Electrodialysis is widely used to separate and concentrate sulfuric acid from industrial wastewater. Nevertheless, owing to the proton leakage of anion‐exchange membrane (AEM), the concentration of recycled sulfuric acid is typically less than 20 wt.%. What is more, the restraining of proton leakage would sacrifice the conductivity of membrane, leading to the increasing of energy consumption (EC). In this work, a proton block and highly conductive polyaniline (PANI)/polyvinylidene fluoride (PVDF) membrane were prepared by creating PANI dominated and hydrophobicity ion channels through etching. The variations of solubility, structure, and electrical performance of membrane during etching process were investigated. As a result, the electrical performance of membrane, especially for the conductivity, was significantly improved owning to the formation of PANI dominated ion channels and spaces. Meanwhile, even the porosity and water content of etched membrane were improved, the anions were mainly migrated through molecular chains of PANI; the protons were still blocked by the hydrophobic pores. Further, the etched membranes with different porosities were used to enrich sulfuric acid (1 wt.%) through electrodialysis. As a result, the proton leakage was proved to be the major limitative factor of acid solution enrichment. By using the optimal etched membrane, concentrated acid (41 wt.%) was obtained with a less energy consume (EC), compared with commercial AEM.