Wancen Xie, Nan Wang, Denghui Pan, Zexu Zhao, Jiahui Wen, Lixue Shen, Wei Zhang, Yao Zhang, Qingjun Yu, Peng Tang
Abstract 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%.