Fabrication of proton permselective composite membrane for electrodialysis-based waste acid reclamation

One of difficulties in electrodialysis (ED)-based waste acid reclamation lies in how to separate protons from metal cations efficiently and economically. A proton permselective composite membrane (PPCM) is specially designed for the process as evidenced by a porous polysulfone membrane and a cross-linked chitosan layer, which perform functions of support and separation, respectively. Herein, a series of PPCM fabricating conditions are analyzed, including casting solution composition, cross-linking agents, and the coating process. Subsequently, the changes in chemical composition and microstructure are explored by ATR-FTIR spectroscopy, SEM and the measurement of porosity and average pore size. Furthermore, the investigations on the electrodialytic transport properties of PPCM are performed, including electrical resistance, limiting current, water transport behavior, and proton permselectivity. Notably, ED experiments show some PPCM performances are even better than those of conventional cation-exchange membranes (CEMs), such as relatively low leakage of metal cations and water migration behavior, relatively high energy efficiency and productivity. However, the proton permselectivity of PPCM for metal cations will weaken with increase of current density, and its proton permselectivity for anions is inferior to CEM. Nevertheless, in view of its many advantages, this paper indicates PPCMs have a promising application prospect.