Toward Sustainable Fabrication of Poly(vinylidene fluoride) Ultrafiltration Membranes via a Nonionic Deep Eutectic Solvent Cosolvent Strategy

Improving the sustainability of poly(vinylidene fluoride) (PVDF) ultrafiltration membrane fabrication requires reducing hazardous solvents without compromising processability or performance. Herein, a nonionic deep eutectic solvent (NIDES) N -methylacetamide/acrylic acid was blended with N, N -dimethylformamide (DMF) to prepare PVDF UF membranes. At relatively lower NIDES fractions (DMF/NIDES = 5:1–2:1), NIDES exhibited both solvent and additive functions, which formed more and better-connected membrane pores, increased near surface oxygen and nitrogen functional groups and enhanced surface wettability. As a result, pure water permeability increased while sodium alginate (SA) rejection was only moderately affected. In contrast, at DMF/NIDES = 1:1, the membrane shifted to a sponge-like morphology with crystalline surface features and reduced surface wettability, causing a severe loss of SA rejection. On the optimized co-solvent basis, 2 wt % poly(vinylpyrrolidone) further enhanced pore connectivity and delivered ultrahigh permeability of 2048.24 L m –2 h –1 bar –1 with SA rejection of 84.60%.