A new mathematical model for transport and adsorption of the saturated brine cations: Fe 2(+), Ca2(+) and Mg2+ through nanofiltration membrane at different pressures and 40 degrees C was developed. Saturated brine containing NaCl with the concentration higher than 97% was challenged with the negatively charged PVD membrane. Three equilibrium adsorption isotherms: Langmuir, Freundlich and Redlich-Peterson were fitted to the cations' equilibrium sorption data at different pressures. The Freundlich isotherm was found to well represent the measured adsorption data based on the higher coefficient of determination (r(2)). The cations transmission through the membrane was elucidated using a simple transport model incorporating convection and diffusion terms. An auxiliary dynamic model was derived for estimation of the membrane bulk porosity variation on the basis of total adsorption rate and accumulation of cations on the membrane matrix. Finally, at each operating pressure, the cations' transport equations (three partial differential equations; PDEs) combined with the adsorption isotherm and were solved simultaneously enumerating the effect of bulk porosity variation during the filtration process. Model estimations were compared with the experimental data at different pressures. Subsequently an acceptable agreement (more than 95%) was achieved. (C) 2009 Elsevier B.V. All rights reserved.