Development and characterization of p-phenylenediamine/g-C 3 N 4 -based composite polysulfone (PSF) membranes for enhanced chromium (Cr(VI)) removal from wastewater

In this study, polysulfone (PSF)-based composite membranes were synthesised through phase inversion. These membranes were then dip-coated with non-functionalized and functionalized Graphitic Carbon Nitride (g-C 3 N 4 ) to enhance Chromium (Cr(VI)) removal from a Cr(VI)-containing aqueous industrial water matrix. The effect of nanofiller loading and functionalization concentration on membrane morphology, thermal stability, hydrophilicity, porosity, pure water flux, and Cr(VI) rejection was systematically investigated. Thermogravimetric Analysis (TGA) depicted improved thermal stability upon incorporation of non-functionalized and functionalized g-C 3 N 4 , while Scanning Electron Microscopy (SEM) revealed structural modifications. Water Contact Angle (WCA) measurements demonstrated significant enhancement in surface hydrophilicity after g-C 3 N 4 incorporation and further improvement upon its functionalization with Para-Phenylenediamine (PPD). Among the non-functionalized membranes, the membrane containing 0.2 g g-C 3 N 4 exhibited optimal performance in terms of permeability and rejection. Functionalization of 0.2 g g-C 3 N 4 with 0.054 mg PPD resulted in the highest porosity, maximum pure water flux of 56.12 L m −2 h −1 and superior Cr(VI) rejection of 95.69%. The results demonstrate that moderate non-functionalized and functionalized g-C 3 N 4 loading significantly enhanced the membrane permeability–selectivity balance, making the optimized membrane highly suitable for Cr(VI) removal from aqueous industrial water matrices.