Study of ionic and diffusive transport through a regenerated cellulose nanoporous membrane

The effect of charge and pore confinement in the transport of NaCl solutions through a regenerated cellulose nanoporous membrane (pore radius around 1.2±0.3 nm) has been studied. Ionic transport numbers and diffusion coefficients as well as effective membrane fixed charge concentration where determined by analyzing membrane potential values, while salt diffusion coefficient was obtained from diffusion experiments for a wide range of feed NaCl solutions (between 0.005 M and 0.4 M). These results show the significance of electrical interactions at low concentrations (up to 0.05 M) but diffusive effects are predominant at higher NaCl concentrations and as a result of nanopore size and charge, values of diffusive parameter present a reduction of one order of magnitude. Membrane conductivity was obtained from electrical resistance results determined from electrochemical impedance spectroscopy (EIS) plots by using a parallel resistance–capacitance equivalent circuit as a model. The similarity in the values of different electrochemical parameters (fixed charge concentration, ionic and salt diffusion coefficients) determined from direct measurements or estimated indirectly by various models supports the reliability of the results obtained and the analysis carried out.