Fabrication of PVDF ultrafiltration membranes with methyl lactate: enhancing performance through green solvent practices

Abstract

Traditional solvents used in the fabrication of ultrafiltration membranes are often toxic, posing risks to the environment and human health. To mitigate these issues, the non-toxic and biodegradable methyl lactate was selected as an alternative solvent for membrane fabrication. The role of methyl lactate during membrane formation was investigated using a combination of non-solvent-induced phase separation (NIPS) and thermally-induced phase separation (TIPS) technique. Polyvinylidene fluoride (PVDF) ultrafiltration membranes with varying compositions and pre-evaporation times were fabricated in a relatively low-temperature system. The optimized membrane exhibited a pure water flux of 135.7 L m⁻² h⁻¹ bar⁻¹ and excellent BSA retention (>99.9%). Owing to their homogeneous sponge-like structure, the membranes fabricated with methyl lactate demonstrated superior mechanical properties compared to PVDF membranes prepared with conventional solvents, with elongation at break exceeding 200%. Furthermore, the abundant availability and competitive cost of methyl lactate among current green solvents highlight its significant advantages for industrial-scale manufacturing. In conclusion, methyl lactate is identified as a new green solvent for PVDF ultrafiltration membrane fabrication, and the resulting membranes show great potential for practical separation processes.