Ion transport properties of cation-exchange membranes modified by nano-sized SiO2 nanoparticles

Poly(vinylidene fluoride)(PVDF) cation-exchange membranes based on nanoparticles modification were prepared by blending process. These membranes were extensively characterized for their surface morphology, and water content, ion perm-selectivity using SEM, water uptake and ion exchange capacity measurements. It was found that membranes conductivity, permselectivity and counterion diffusion coefficient increased with the weight of SiO₂ content in the membrane phase. When SiO₂ content was 20% of PVDF and ion mean concentration was 0.055 mol/L, the permselectivities of Na⁺, Ca²⁺ and Mg²⁺ were 0.984, 0.893 and 0.891, respectively. When SiO₂ was 0.28%, Na⁺ diffusion coefficient was 11.16×10^-12m²/s. And Na⁺ diffusion coefficient of cation-exchange membranes without SiO₂ content was 3.71×10^-12m²/s. Furthermore, membranes with 2.0% SiO₂ nanoparticles exhibited very good selectivity, water content, ion-exchange capacity and moderate membrane conductivity, which may be used for the application in membrane treatment processes and fuel cell.