Poly(vinyl alcohol)-based highly permeable TFC nanofiltration membranes for selective dye/salt separation

Loose nanofiltration (LNF) membranes possessing high water permeance and outstanding dye/salt selectivity are highly desirable for fractionating dyes and salts for textile wastewater. Herein, inexpensive and nontoxic poly(vinyl alcohol) (PVA) was utilized as an aqueous monomer via interfacial polymerization to fabricate novel highly permeable LNF membranes upon activation by sodium hydroxide. Systematic chemical and structural analyses indicated that the prepared polyester membrane formed was loose, hydrophilic, and negatively charged. The properties of the LNF membranes were optimized by adjusting the curing temperature (70 °C–100 °C). The optimized PVA-based membrane (PVA-M70°C) showed excellent water permeability (52.6 L m−2 h−1 bar−1), favorable dye rejection (> 90.0 %) and low salt rejection (NaCl and Na2SO4 rejection rates were lower than 5 % and 18 %, respectively). Furthermore, the PVA-M membrane demonstrated excellent antifouling properties and long-term stability. Considering the biodegradable nature and low cost of PVA, PVA-based polyester membranes show great promise for LNF membrane production on an industrial scale. This work advances the use of PVA as a green aqueous monomer in fabricating highly permeable LNF membranes for efficient dye/salt selectivity.