A simple and green preparation of PVA-based cation exchange hybrid membranes for alkali recovery

Here, a novel and green route for preparing cation exchange hybrid membranes is presented via polyvinyl alcohol (PVA) and 3-trihydroxysilyl-1-propanesulfonic acid (THOPS), during which aqueous media instead of organic solvents is used and sulfonation process is avoided. The resulting hybrid membranes have the water uptake (WR) of 38–86%, ion exchange capacities (IECs) of 0.70–1.56 mmol/g, initial decomposition temperature (IDT) of 224–231 °C, tensile strength (TS) of 13.3–40.7 MPa, and favorable elongation at break (Eb) of 177–571%. The linear expansion ratio (LER) is in the range of 15–25% in water, while in the range of 18–27% in 1.0 M alkali solution. Diffusion dialysis (DD) of NaOH/Na2WO4 system shows that the dialysis coefficients of NaOH (UOH) are in the range of 0.011–0.022 m/h, with the separation factors (S) of 11.6–20.6. Consequently, apart from endowing the resulting hybrid membranes with desirable DD performances, the method employed herein is simple and environment-friendly particularly due to the avoidance of organic solvents and hazardous sulfonation agents.