Evaluating the multifaceted separative role of cellulose acetate supported zinc oxide nanocomposite reverse osmosis membrane towards water decontamination and desalination

• Developed CA@ZnO membrane for enhanced water purification. • Employed phase inversion method with DMF as a solvent. • DFT analysis revealed electronic properties of the membrane. • Removes salts, heavy metals and degrades methylene blue. • Filtered 70–80% oil from oily wastewater. This study explores the development of a novel reverse osmosis (RO) membrane composed of cellulose acetate (CA) and zinc oxide nanoparticles (ZnO). The main objective was to fabricate a multifunctional membrane, synthesized through the phase inversion method, capable of low-cost simultaneous desalination with high ion selectivity, efficient dye removal under optimized conditions, and significant elimination of heavy metal ions and organic contaminants for enhanced water purification. Density functional theory (DFT) analysis was further employed to examine the electronic properties, including band structure, density of states, and charge distribution, thereby linking nanoscale behavior to observed performance. The CA@ZnO membrane exhibited excellent efficiency in removing dissolved salts (Na + , Ca 2+ , Mg 2+ ), achieving 60% rejection for NaCl, 44.03% for CaCl 2 , and 43.34% for MgCl 2 . It further enabled the removal of 70–80% oil from oily wastewater and showed high adsorption efficiency for methylene blue dye in the visible spectrum range. In addition, the membrane exhibited substantial removal of toxic heavy metals (Ni 2+ , Zn 2+ , Cd 2+ , Cr 3+ , Fe 3+ ) under optimized conditions. Compared to conventional polymeric RO membranes, the CA@ZnO composite showed enhanced stability, antimicrobial activity, and cost-effectiveness, addressing the challenges of fouling and limited selectivity. The novelty of this study lies in the dual role of ZnO nanoparticles, which not only improve ion rejection but also introduce photocatalytic activity for dye degradation, enabling multifunctional water purification in a single platform. These findings underscore the potential of the CA@ZnO membrane for advanced desalination, pollutant removal, and water purification applications.