Preparation of carboxylic multiwalled-carbon-nanotube–modified poly(m-phenylene isophthalamide) hollow fiber nanofiltration membranes with improved performance and application for dye removal

Carboxylic multiwalled carbon nanotube (C-MWCNT)-modified poly(m-phenylene isophthal amide) (PMIA) hollow fiber nanofiltration (NF) membranes were fabricated by a dry-jet wet spinning method. Different contents of C-MWCNTs (0.0675%, 0.10% and 0.15%) were blended into the PMIA to enhance the performance of the C-MWCNTs/PMIA NF membranes. The membrane morphology, surface properties and solute separation performances of the C-MWCNTs/PMIA NF membranes were characterized. The results showed the C-MWCNTs/PMIA NF membranes with 0.1% C-MWCNTs exhibited the best performance of the membranes, with the water flux and Na ₂ SO ₄ rejection up to 51 L/(m ² h) and 81% at 10 bar, respectively. Results of dye removal experimental showed that the membranes exhibited a higher removal for direct red 23 and congo red with more negative charge.