Efficient synthesis of interfacially polymerized membranes for solvent resistant nanofiltration

Thin film composite (TFC) membranes are used worldwide in aqueous applications. They mostly consist of a polyamide top-layer put on a polysulfone support via interfacial polymerization. Due to their thin and dense selective layer, these membranes are also interesting for filtrations in organic solutions. Polysulfone should then be replaced by a more solvent resistant material. The synthesis of solvent resistant nanofiltration TFC membranes via a newly developed method is reported: phase inversion, crosslinking and impregnation of a polyimide support are combined by adding amines to the aqueous coagulation bath. Next, a thin polyamide top-layer is formed on the support via interfacial polymerization. Several amines are tested as crosslinker for the support and as monomer for top-layer formation. The use of an amine mixture is also explored. Membrane stability, time in the coagulation bath, effect of solvent activation and mass & solvent intensity of the process are investigated. This novel synthesis method minimizes the use of (hazardous) materials, thus requires less reagents and creates less waste. Moreover, time and effort are saved during the synthesis process, which is of great interest for membrane producers and from an environmental point of view.