Polyelectrolyte complex/PVA membranes for diffusion dialysis

Polyelectrolyte complexes (PECs)/polyvinyl alcohol (PVA) membranes are prepared from PVA, anion exchange and cation exchange multisilicon copolymers. Covalent network through SiOSi bonding, electrostatic interaction between N+(CH3)3 and SO3 groups and hydrogen bonding are present to strengthen the membrane structure. •Polyelectrolyte complexes(PECs)/PVA membranes are prepared from PVA, anion exchange and cation exchange multisilicon copolymers.•SiOSi bonding, electrostatic interaction and hydrogen bonding are present to strengthen the membrane structure.•The membrane structure differs from typical “two-phase” or “three-phase” IEMs.•Zwitterionic or charge neutralization micro-phase influences the ions transport processes. Polyelectrolyte complexes (PECs)/polyvinyl alcohol (PVA) membranes are prepared from PVA, anion exchange and cation exchange multisilicon copolymers, which contain plenty of functional groups of OH, N+(CH3)3/Si(OCH3)3, and SO3Na/Si(OCH3)3, respectively. The OH and Si(OCH3)3 groups can undertake sol–gel reaction to form crosslinking structure, while the N+(CH3)3 and SO3Na groups can be combined through electrostatic interaction. The PECs/PVA membranes exhibit improved thermal stability, swelling resistance and flexibility as compared with single anion or cation exchange hybrid membranes. The PECs/PVA membranes have the water uptakes (WR) of 25.3–70.4%, initial decomposition temperatures (IDTs) of 246–285°C, tensile strength of 23.1–33.8MPa, and elongation at break of 3.5–13.1%. The membranes can be potentially applied for both acid and alkali recovery through diffusion dialysis (DD) process. The separation factor (S) for HCl/FeCl2 mixture can reach up to 89.9, which is about five times higher than that of commercial DF-120 membrane (18.5 at 25°C). The dialysis coefficients of NaOH (UOH) are in the range of 0.014–0.019m/h, around 7–9 times higher than the value of commercial SPPO membrane (0.002m/h at 25°C). The membranes also show potential usefulness for industrial acidic and alkali wastes treatment.