Diffusion dialysis membranes with semi-interpenetrating network for alkali recovery

Cation exchange membranes based on semi-interpenetrating network (sIPN) are prepared for diffusion dialysis (DD) using poly(vinylidene difluoride) (PVDF) and sodium p-styrenesulfonate (SSS) as starting materials. Five membranes have been prepared by varying the content of PVDF and dosage of cross-linking agent. Ion exchange capacity (IEC), water uptake (WR), swelling resistance and mechanical property of the membranes have been measured. These membranes show excellent thermal and alkali stability due to the high-performance PVDF matrix and sIPN morphology. The membranes have been successfully applied to alkali recovery. The base dialysis coefficients (UOH) are in the range of 0.0008–0.0061 m/h and the separation factors (S) in the range of 12.0–90.3 at 25–65 °C. Effect of PVDF content and cross-linking degree on ion permeability and selectivity has been discussed.