Thin film composite solvent resistant nanofiltration membrane via interfacial polymerization on an engineered polyethylene membrane support coated with polydopamine

In this work, a thin film composite (TFC) membrane possessing outstanding properties for solvent resistant nanofiltration (SRNF) membrane application was fabricated. For this purpose, high density polyethylene (HDPE)-polystyrene (PS)-styrene-ethylene-butylene-styrene (SEBS) blends were fabricated in the first step with different compositions by using an internal mixer machine and hot press technique, respectively. Then, the fabrication of a novel HDPE support was conducted by etching the PS phase out of the as-prepared HDPE-PS-SEBS blends through solvent extraction method (Etched HDPE). In the next step, the prepared Etched HDPE membrane support was dipped in a dopamine solution, by which auto-oxidization and self-polymerization of dopamine monomers onto the Etched HDPE membrane supports surface was done, leading to the formation of an ultrathin polydopamine (PDA) layer with a strong chemical binding force. By the formation of the polydopamine layer, hydrophilic functional groups were introduced onto the HDPE membranes surface , causing the attraction of m -phenylenediamine (MPD) monomers onto the membrane surface and the formation of a uniform ultrathin PA top layer. Finally, the TFC layer was formed on the as-prepared membrane supports with different m -phenylenediamine and trimesoyl chloride (TMC) concentrations. The performance and properties of the prepared TFC-PE@PDA membrane was investigated for rejection of different dyes including Reactive Red, Direct Yellow, Methyl Blue, Rhodamine B, Crystal Violet and Methyl Orange in SRNF applications, based on which outstanding separation performance (dye rejections of 99.8, 99.5, 99.2, 98.5, 96.8 and 94.4 for RR, DY, MB, RDB, CV and MO, respectively, under the pressure of 9 bar), methanol flux as high as 1.8 L/m 2 h bar along with excellent methanol flux as high as 3.7 L/m 2 h bar after Dimethylformamide activation, were obtained. Furthermore, it is noteworthy that an outstanding solvent resistance (dye rejections of more than 99.2, 98.8, 98.5, 97.9, 96 and 93.8% for RR, DY, MB, RDB, CV and MO, respectively, being dipped in Dimethylformamide at 70 °C for 90 days) was also shown by the prepared TFC-PE@PDA membrane. • A novel Etched PE membrane support was fabricated via etching the PS-SEBS phase out of the as-prepared PS/SEBS/PE composite. • A TFC membrane was prepared via the formation of the thin film layer on the Etched PE membrane covered with a PDA layer. • The prepared TFC membranes contained a hydrophilic and defect-free polyamide barrier layer. • The prepared TFC membranes showed a significant dye rejection performance and superior solvent resistance.