Parametric study of microporous nanofiber support and thin-film composite membranes for remediation of saline water

In this work, polyamide 6 (PA6) nanofiber-supported thin-film composite membranes have been studied for saline water remediation. Nanofiber-based support layers are critical in enhancing the membrane surface area and facilitating the formation of high-performance polyamide (PA) thin films. Herein, microporous nanofiber support membranes were fabricated using a lamination technique at varying temperatures, and the effects of lamination temperature on fiber diameter, pore size, and air permeability were investigated to optimize the support layer for PA thin-film membrane fabrication. Results indicate that increasing the lamination temperature from 110°C to 135°C decreases air permeability and pore size while increasing fiber diameter. Using the optimized support laminated at 110°C, ultrafiltration PA thin-film membranes were developed, and the effects of monomer type and feed pH on membrane performance were evaluated. M-phenylenediamine (MPD)-based membranes achieved a maximum salt rejection of 74% but exhibited a relatively low water flux of 0.42 L·m ⁻² ·h ⁻¹ at 400 kPa. In contrast, piperazine (PIP)-based membranes demonstrated a low sodium chloride (NaCl) rejection of 25% but a high magnesium sulfate (MgSO ₄ ) rejection of 97% at the same benzenetricarbonyl trichloride (TMC) concentration, with a significantly higher flux of 8.6 L·m ⁻² ·h ⁻¹ . Acidic conditions improved the flux of MPD-based membranes up to 5-fold but significantly reduced salt rejection, whereas alkaline conditions enhanced salt rejection for PIP-based membranes while decreasing flux. This work is the first attempt in the literature to systematically investigate the influence of lamination temperature on nanofiber support for further PA thin-film membrane formation, providing new insights into optimizing support layer properties for desalination.