Fabrication of Poly(vinylidene fluoride) Ultrafiltration Membranes Using Greener PolarClean and NIDES: Structure Regulation, Performance Enhancement, and Life Cycle Assessment

Abstract

Replacing toxic solvents and petrochemical additives in poly(vinylidene fluoride) (PVDF) ultrafiltration (UF) membrane fabrication is essential for advancing sustainable membrane manufacturing. Herein, a greener fabrication route for PVDF UF membranes was developed by employing PolarClean as a green solvent and a nonionic deep eutectic solvent (NIDES) as a green additive at a relatively low temperature. The effects of PVDF concentration, NIDES dosage, and the support layer on phase inversion behavior as well as membrane properties were systematically investigated. The results showed that the NIDES acted as both a pore-forming agent and a surface chemical modifier. At an appropriate dosage, NIDES promoted pore formation and enriched functional groups on the membrane surface. However, excessive addition led to additive deposition and surface heterogeneity. The optimized membrane M5-8P-1DES achieved a pure water permeability of 1040 L m–2 h–1 bar–1 with a sodium alginate rejection of 96.8%. For mechanical property optimization, the support layer was utilized and the supported membrane further increased permeability to 2459 L m–2 h–1 bar–1. Life cycle assessment showed that PolarClean and NIDES were mostly environmentally preferable to conventional materials. However, under realistic fabrication conditions, the PolarClean-based membrane showed higher impacts in most categories due to higher solvent demand and energy input. Green electricity analysis showed that onshore wind electricity markedly improved its environmental competitiveness, making it the lowest-impact option. This highlights the importance of low-carbon electricity for realizing the sustainability potential of PolarClean-based membrane fabrication. Overall, this study provides both a greener fabrication strategy for PVDF membranes and a clearer framework for assessing truly sustainable membrane manufacturing.