Modelling of solute transport in non-aqueous nanofiltration

This work presents a new approach for modelling of transport of small organic components in nanofiltration of organic solvents. The solute rejection in non-aqueous nanofiltration is affected by a number of membrane–solvent–component interactions, which must be incorporated in a generalised transport model. Since measuring or calculating membrane–solvent–component interactions is difficult, a simple empirical approach is adopted to model the data based on a pore-flow formalism. Previous work showed that solute transport in non-aqueous NF is mainly dominated by convection, but transport models for pore flow, available in the literature, only consider aqueous feed streams. In this article, solvent dependency was implemented in these models in terms of effective pore and solute diameters. This approach was applied on four literature models (the SHP-model, the Ferry model, the Verniory model and the lognormal model). Descriptive modelling of the experimental rejection data of different reference components in methanol, ethanol, acetone and ethyl acetate resulted in the identification of unknown membrane characteristics (pore size or pore size distribution), clearly confirming the solvent dependence of these parameters. This effect was observed for both polymeric and ceramic NF-membranes.The membrane parameters identified from the data fitting were used for predictive modelling of the rejection of raffinose in methanol and ethanol, with a hydrophilic and a hydrophobic NF membrane. A high correlation between predicted values and experimental data was found.