Concentration Polarization in Membrane Systems

The phenomenon of concentration polarization (CP) in membrane systems refers to the emergence of concentration gradients in solution near the membrane surface due to the selective transport of some solution components through the membrane under the effect of transmembrane driving forces. CP accompanies all types of membrane processes, changing transport conditions and reducing efficiency of separation processes: in most cases, the total transport rate decreases, the energy consumption increases, and the selectivity of the transport process is lost. This review addresses general regularities and specific features of the CP phenomenon in electrodialysis, reverse osmosis, nanofiltration, ultrafiltration, and pervaporation processes, as well as membrane sensing systems and fuel cells. Fundamentals of the CP phenomenon and experimental methods for its investigation are discussed.