Towards sustainable fabrication of modified PVDF membranes using CyreneTM: Exploring chitosan nanoparticles as bio-filler

The urgent need for sustainable approaches in the fabrication of phase-inverted membranes underscores the significance of this study, which investigates a novel combination of bio-based membrane materials. Specifically, this work explores the use of Cyrene^TM, a green solvent, in conjunction with chitosan nanoparticles (CNPs) as a bio-filler for the production of sustainable polyvinylidene fluoride (PVDF) membranes. Additionally, lithium chloride (LiCl) was utilized both as a standalone additive and in combination with CNPs at varying concentrations to evaluate the effects on the structural, mechanical, and filtration properties of PVDF-Cyrene^TM membranes. The findings reveal that increasing concentrations of LiCl as a standalone additive (2.5; 3.0; and 3.5 wt %) yielded hydrophilic membranes with progressively denser and more refined nodular morphologies, which significantly compromised the membranes’ pure water flux (PWF). Notably, the incorporation of CNPs alongside LiCl markedly enhanced membrane pure water flux, particularly at concentrations of 0.5 wt % and 0.7 wt %. In contrast, a sharp decline in PWF was observed at 0.3 wt % CNPs, likely attributable to inadequate CNPs dispersion within the membrane matrix, leading to pore blockage and a substantial reduction in flux. Additionally, the addition of CNPs was most effective at 0.1 wt % to elevate the membrane tensile strength. This study demonstrates that the synergistic use of LiCl and CNPs represents a promising strategy to enhance the mechanical and filtration performance of PVDF membranes. However, the results emphasize the importance of carefully optimizing additive concentrations to achieve balance between various membrane properties. Furthermore, this work highlights the limitations of Cyrene^TM as a solvent, which warrants further investigation to improve its applicability in membrane fabrication processes.