Tuning electrodialytic transport properties of heterogeneous cation exchange membrane by the addition of charged microspheres

In this study, the sulfonated polystyrene microspheres (MPs) which embraced much smaller particle size and narrower size distribution than those of conventional resin powders (RPs) were synthesized and employed as ion-exchangers exclusively or additives to prepare heterogeneous cation exchange membrane (CEM). Thereupon the effects of the incorporation of the charged MPs on the properties of heterogeneous CEM were investigated. Firstly, the morphologies of the synthesized MPs and the corresponding CEMs were examined by SEM observation. Then, the membrane properties were comprehensively evaluated by the measurements of ion exchange capacity, water uptake, transport number, salt permeability coefficient, membrane resistance, limiting current density and so on. Moreover, surface homogeneity was explored by means of the chronopotentiometric analyses. The experimental results showed that the required amount of RPs can be reduced significantly by adding moderate MPs while achieving the similar or even higher membrane conductivity at almost no sacrifice of other membrane properties. Moreover, the surface homogeneity was also enhanced, which can effectively alleviate the concentration polarization behavior at the membrane/solution interface. All these experimental results indicated that the added MPs can make good connections among the conductive regions both in membrane body and at membrane surface and then facilitate ion transport.