Novel composite cation exchange films based on sulfonated PVDF for electromembrane separations

A novel cation exchange membrane (CEM) composed of a blend of polyvinylidene fluoride (PVDF) and sulfonated PVDF (S-PVDF) was prepared. The membranes were prepared with different fractions of S-PVDF to optimize performance in desalination. The sulfonated polymer was characterized by FTIR, HNMR, DSC and TGA. The membrane properties such as ion exchange capacity (IEC), transport number, morphology, permselectivity, ion conductivity, water uptake, contact angle and electrodialysis (ED) performance were evaluated. Polymer characterization proved the sulfonation of PVDF and the degree of sulfonation was estimated. With increasing S-PVDF fractions, the transport number and permselectivity decreased while the IEC and ion conductivity increased. Finally, the salt extraction in ED obtained for a 70% S-PVDF membrane was 67.6%, which is a better performance than that of a commercial membrane.