Reflection coefficient of nanofiltration membranes in single electrolyte solution
The space-charge(SC)model and Teorell-Meyer-Sievers(TMS)model combined with irreversible thermodynamics model are applied to predict the transport coefficients of nanofiltration membranes in single electrolyte solution.The reflection coefficient has been numerically calculated by the SC model and analytically calculated by TMS model.The results show that the reflection coefficient approaches unit in the range of low-concentration regime and approaches zero in the range of high-concentration.While the diffusion coefficients ratio of co-ion over counterion is less than 1.0,the reflection coefficient is positive over the whole concentration range.When the ratio is larger than 1.0,the reflection coefficient is negative in a certain intermediate concentration region.And the increase of the surface charge density and the decrease of the pore radius cause the increase in the reflection coefficient.The SC model and TMS model show good agreement in the calculation of the reflection coefficient when the dimensionless potential gradient in the pore surfaces is less than 1.0 and the pore radius is less than 5.0 nm.