NUMERICAL ANALYSIS ON SELECTIVE ION TRANSPORT IN CHARGED NANO-PORES FOR ELECTRODIALYSIS APPLICATIONS

Abstract

Increasing attentions are paid to charged nano-pore membranes for ion exchange applications. Numerous studies showed that the ion transport characteristics in nano-channels are strongly influenced by electrolyte concentration as well as surface charge density on channel walls. Previously, we discovered the selective ion diffusivity through charged nano-pore membranes decreased with an increase in electrolyte concentration due to the steep decay of electrical potential in the pore. In this study, we conducted numerical analyses investigating ion transport properties in cylindrical charged nano-channels for various electrolyte concentration and channel geometry. Poisson and Nernst-Planck equations were solved to calculate the distributions of electrical potential and ion concentrations. For 3 nm pores with a charge density of 50 mC/m2, the transport numbers are evaluated as 0.91 and 0.85 at electrolyte concentrations of 35 and 70 g NaCl/L, respectively. The transport number also decreased with an increase in pore size. However, the 20 nm pore membrane maintained ion exchange characteristics with transport numbers greater than 0.72 at the concentration of 35 g NaCl/L.