Transfer of Monovalent Salts through Nanofiltration Membranes: A Model Combining Transport through Pores and the Polarization Layer

Nanofiltration is a very useful separation process having many industrial and environmental applications. The prediction of separation performances requires the understanding of the various physical phenomena governing the solute transfer through the membrane. In this paper, a two-dimensional model called the pores and polarization transport model (PPTM) is presented, which combines the convective-diffusive-migration transport within the pores with the transport through the concentration polarization layer. This model was developed for predictive purpose to evaluate the efficiency of separation with a minimum of characterization experiments. Model parameters assessment is presented, and experimental results obtained for various monovalent salt solutions (NaCl and KCl) are compared with simulations to validate the model. This model can predict the influence of the various operating parameters on the polarization layer and the experimental rejections of single salt solutions.