where Di is the diffusion coefficient of species i (m 2 /s), R is the universal gas constant (J/mol.K), and T is the temperature (K). Instead of direct measurement of ion diffusivity, it could be estimated from other properties. There are different models with complex ranges that have been developed to explain ion transport. However, despite its simplicity, the Wilke and Chang equation is a good approximation of ion diffusivity. Therefore, the diffusivity of ionic species is defined as: 50