Preparation of cation-exchange hybrid membranes with multi-functional groups and their performance on alkali recovery

Abstract

Cation-exchange hybrid membranes have been prepared via the blending of sulfonated poly(2,6-dimethyl-1,4-phenylene oxide) (SPPO) with poly(vinyl alcohol) (PVA), which is cross-linked with multisilicon copolymer of poly(acrylic acid-co-γ-methacryloxypropyl trimethoxy silane) (poly(AA-co-γ-MPS)). The SPPO phase, PVA phase, and multisilicon copolymer can provide the membranes with functional groups of –SO3Na, –OH and –COOH, respectively. Hence, multi-functional groups are formed within the hybrid membranes. The hybrid membranes have a short-term thermal stability of 234–260°C, tensile strength (TS) of 12–13 MPa, and elongation at break of 27–49%. Membrane stability in alkaline solution is much affected by the content of SPPO. The membranes are potentially applied in diffusion dialysis (DD) for alkali recovery (NaOH/Na2WO4). The dialysis coefficients of NaOH (UOH) are in the range of 0.0075–0.032 m/h, which are higher than those of commercial membranes and reported membranes. The separation factor can reach up to 21.2 at 25°C for the membrane containing 10 wt% SPPO. Meanwhile, the membrane shows relative stability during long-term DD process. Hence, the multi-functional groups are effective for the diffusion dialysis process.