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, 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 23.1-33.8 MPa, 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 0.014-0.019 m/h, around 7-9 times higher than the value of commercial SPPO membrane (0.002 m/h at 25°C). The membranes also show potential usefulness for industrial acidic and alkali wastes treatment.