High Permeance Polyamide Nanofiltration Membranes Based on Poly(l-lactic acid) Electrospun Nanofibrous Membranes with Controlled Hydrophilicity

Abstract

Nanofiltration (NF) membranes have aroused great attention in recent years. The most commonly used NF membranes are polyamide (PA) thin-film composite (TFC) membranes based on ultrafiltration membranes. Owing to the high porosity and interconnected pores, electrospun nanofibrous membranes are promising substrates for the fabrication of high-flux nanofiltration membranes, i.e., thin-film nanofibrous composite (TFNC) nanofiltration membranes. In this work, poly(l-lactic acid) (PLLA) nanofibrous membranes with adjustable hydrophilicity were successfully fabricated, and then, a PA layer was synthesized on the surface via the interfacial polymerization between piperazine (PIP) and trimesoyl chloride (TMC). The hydrophilicity of PLLA nanofibrous membranes influences the distribution and adsorption weight of PIP, which further affects the formation and morphology of the PA layer. Results indicate that, as the hydrophilicity of PLLA nanofibrous membranes increases, the adsorption amount of PIP increases, the thickness of the PA layer decreases, and the cross-linking degree increases, which ensures both high permeance and high rejection to Na2SO4. The TFNC membranes exhibit a water permeance of 17.0 L·m–2·h–1·bar–1 and a Na2SO4 rejection of 98.0%. This work achieves the control of substrate hydrophilicity by introducing hydrophilic additives and provides new insights for the fabrication of high-performance nanofiltration membranes.