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In this work a method is proposed to predict salt rejection by nanofiltration. The procedure starts from the steric, electric and dielectric exclusion model with charge (and permitivity) depending on the concentration along the pore, SEDE-VCh, for membrane characterization, and substitutes all fitting parameters by values obtained by independent methods. These parameters are the relative permittivity inside the pores and the two constants of the Freundlich isotherm for the volumetric charge density, which can be obtained by impedance spectroscopy techniques. Moreover, the pore size and shape and the active layer thickness are required to complement the model. The pore size was obtained by using a neutral solute rejection test and the active layer thickness was estimated by SEM. Therefore, the model also requires pore shape as input. AFM measurements suggest the assumption of a slit shape for the pores.A Desal-HL membrane has been structurally, electrically and functionally characterized. These data allowed the testing of the predictive model that was subsequently demonstrated; as far as results are good enough considering the complexity of the mechanisms involved. Consequently, it seems clear that once the model parameters have been obtained by independent methods, it can be used as a predictive tool.

2011) Dielectric properties of electrolyte solutions in polymeric nanofiltration membranes, Desalination and Water Treatment, 27:1-3, 25-30To link to this article: http://dx. A B S T R AC TIn this work a nanofi ltration membrane immersed in an electrolyte solution has been studied using impedance spectroscopy. In this technique the membrane is in contact with the same concentration at both sides, therefore there is not any ion transport through the membrane and, thus, it is possible to obtain electric and dielectric properties that would help to model the nanofi ltration process. Results allow obtaining the electrical properties of the whole system assumed as consisting in an equivalent electric circuit. Three relaxation times can be identifi ed and modeled with the aim of understanding the behavior of the solution inside the pores as a function of concentration. The pore permittivity decreases with increasing concentration due to confi nement effects, while the conductivity inside the pores increases rapidly for high concentrations due to the easy penetration of the ions into the pores.

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