Modeling of the separation performance of nanofiltration membranes and its role in the applications of nanofiltration technology in product separation processes

Although there is a voluminous literature on the determination of structural parameters(the pore radius,the ratio of membrane porosity to membrane thickness)of a nanofiltration(NF)membrane and its separation perfor-mance(such as the rejection and the permeation flux)by the simplified Teorell-Meyer-Sievers(TMS)model,little of this research comments on other theories and the consequences of linking modeling evaluation to technological application.Theories used to predict the separation performance of an NF membrane usually include:the non-equilibrium thermo-dynamic model,the pore model,the space charge model,the TMS model,the electrostatic and steric-hindrance model,and the semiempirical model.In the article,we briefly trace the origins or the general ideas of the above-mentioned theories.From there,recent researches on the characterization of mem-brane structural parameters and electrical properties(such as the surface charge density qw)are reviewed.We then turn to research on the separation performance of an NF membrane for single-component solutions of inorganic electrolytes,neutral organic solutions,and a mixture solution of electro-lytes or that of an electrolyte and neutral organic solute.Afterwards,we outline the applications of NF technology in the processes of product separation and conclude with a discussion on the role of models in such applications.