Preparation of proton permselective composite membrane and its application in waste acid reclamation by ion substitution electrodialysis

Nowadays, the reclamation of industrial waste acid characterized with low acid concentration and high metal ion content has attracted much attention. How to carry out effectively a separation between protons and metal ions becomes a top priority. In this report, a so-called proton permselective composite membrane was prepared specifically for waste acid reclamation by electrodialysis. Above all, a porous supporting membrane was prepared from polysulfone via classical wet phase inversion technology. Therein appropriate amount of sulfonated polysulfone (SPSF) was added to adjust its microstructure. Subsequently, a hydrophilic composite layer, such as Poly(ethylene imine) layer or Poly(vinyl alcohol) layer, was used to endow the proton permeability based on the unique transport mechanism of protons in which water molecules play an important role. ATR-FTIR and SEM were employed to monitor the changes in chemical composition and microstructure of as-prepared membranes, respectively. Furthermore, their electrodialytic transport properties, including electrical resistance, limiting current, water transport behaviors, proton permselectivity and anion-blocking ability, were investigated and compared with those of typical commercial cation-exchange membrane. As confirmed by series of electrochemical characterizations, as-prepared composite membranes, especially PVA-Series membranes, exhibited outstanding work performances and remarkable practical value in the acid recovery. At last, the ion substitution electrodialysis for waste acid reclamation in which typical composite membranes were assembled were also conducted to examine the process energy consumption, the concentration and purity of the produced acid.