Over the past decade, solvent resistant nanofiltration (SRNF) has gained a lot of attention, as it is a promising energy- and waste-efficient unit process to separate mixtures down to a molecular level. This critical review focuses on all aspects related to this new burgeoning technology, occasionally also including literature obtained on aqueous applications or related membrane processes, if of relevance to understand SRNF better. An overview of the different membrane materials and the methods to turn them into suitable SRNF-membranes will be given first. The membrane transport mechanism and its modelling will receive attention in order to understand the process and the reported membrane performances better. Finally, all SRNF-applications reported so far - in food chemistry, petrochemistry, catalysis, pharmaceutical manufacturing - will be reviewed exhaustively (324 references).

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Alternating deposition of oppositely charged polyelectrolyte (PEs) can create stable solvent-resistant nanofiltration (SRNF) membranes with very high flux and selectivity. A new combination of PEs (poly(diallyldimethylammonium chloride) and sulfonated poly(ether ether ketone) is reported from which supported membranes consisting of 5, 10, 15, and 20 bilayers are prepared via the layer-by-layer method. The morphology of the membranes was studied in detail by SEM and AFM, showing rougher membrane surfaces with increasing bilayer number. For the first time, polyelectrolyte complex (PEC) based membranes were also applied in the filtration of organic solvents, where they form an excellent new tool to study the role of charges in solvent filtrations. Due to Donnan exclusion, the multilayered PEC membranes showed very good retentions up to 99% for charged solutes in the pressure-driven filtration of isopropanol solutions. Moreover, they were found to show excellent prospective use in polar aprotic solvents, like dimethylformamide and tetrahydrofuran, which have been extremely troublesome so far for most existing SRNF membranes.

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