PVA–silica anion-exchange hybrid membranes prepared through a copolymer crosslinking agent

With poly(vinyl alcohol) (PVA) and N-triethoxysilylpropyl-N,N,N-trimethylammonium iodine (A-1100(+)) as the starting precursors, PVA–SiO2 anion-exchange membranes have been successfully prepared through sol–gel process. Exploration of the preparation conditions shows that some crosslinking agents are necessary for enhancement of PVA and A-1100(+) interaction and acquirement of membranes with improved stability in salt liquid and water. The crosslinking agents include small alkoxysilanes, such as tetraethoxysilane (TEOS), γ-glycidoxypropyltrimethoxysilane (GPTMS), monophenyltriethoxysilane (EPh), and a copolymer from glycidylmethacrylate (GMA) and γ-methacryloxypropyl trimethoxy silane (γ-MPS). Among these, poly(GMA-co-γ-MPS) exhibits more excellent crosslinking ability due to its long polymer chain, multi-alkoxy silicon groups, and multi-epoxy groups. Membranes crosslinked with 25% poly(GMA-co-γ-MPS) and heated at 120 °C demonstrate favorable hydrophilicity (water uptake, WR, in the range of 64–151%) and high tensile properties. The tensile strength (TS) is in the range of 55–82 MPa, and the elongation at break (Eb) can reach up to 16.0%. Practical ion exchange capacities (IECP) are in the range of 0.52–0.79 mmol/g, and static transport number (t−) varies from 0.69 to 0.80. Membranes crosslinked with 25% or 50% poly(GMA-co-γ-MPS) and heated at 130 °C show lower mechanical strength, but have higher stabilities and electrical properties. WR is in the range of 29–39%, and the IECP is ranging from 0.76 to 1.01 mmol/g. Diffusion dialysis of hydrochloride acid (HCl) and ferrous chloride (FeCl2) mixture shows the separation factor SH/Fe can reach up to 21, with higher dialysis coefficient of H+ (UH) than that of commercial membrane DF-120.