Optimization of crosslinking in Poly(vinylidene fluoride) membranes for solvent-resistant nanofiltration: a comparative study between crosslinking agents

This study presents an optimized and scalable crosslinking approach for poly(vinylidene fluoride) (PVDF) membranes in solvent-resistant nanofiltration (SRNF), emphasizing cost efficiency, safety, and environmental sustainability. The effect of four swelling media – water, methanol, ethanol and isopropanol – and three amine crosslinkers – 1,6-hexamethylenediamine (HDA), polyethyleneimine (PEI), and 2,2’-(ethylenedioxy)bis-(ethylamine) (Jeffamine) – on membrane stability, permeability, and rejection was investigated. Filtration performance was tested using a 2-methyltetrahydrofuran (MeTHF) solution containing Sudan Black B (SB) (457 Da) dye. Results were benchmarked against those PVDF membranes prepared using the earlier reported undiluted diamine crosslinking method. The new optimized approach, utilizing a 2.5 wt% HDA solution in ethanol for reaction during 24 h, achieved high solvent resistance and yielded comparable SB rejection (73 %) and permeance (16 L m−2 h−1 bar−1). Characterization via X-ray photoelectron spectroscopy (XPS), gel content analysis, and tensile strength measurements validated the enhanced stability and performance of the crosslinked membranes. These findings support the feasibility of implementing cheaper and more sustainable diluted amine crosslinking solutions to prepare PVDF-based SRNF membranes, advancing sustainable production of membranes for industrial applications.