Engineering High-Performance Nanofiltration Membranes With Functionalized SAPO-34: Toward Efficient Desalination and Pharmaceutical Micropollutant Rejection

Access to clean water is a basic human right. Membrane-based filtration processes are less energy-intensive but have some shortcomings, such as chlorine instability, fouling, and the flux–rejection trade-off. This work has fabricated higher-flux, chlorine-resistant, and divalent-selective thin-film composite (TFC) membranes by covalently decorating functionalized SAPO-34 into the active layer. SAPO-34 was synthesized, followed by triamine functionalization and characterization using powdered XRD, TEM, SEM–EDX, FTIR and TGA. The functionalized SAPO-34 was dispersed (different % wt ratios viz. 0.025 and 0.05) into aqueous piperazine solution while fabricating the polyamide layer crosslinked using trimesoyl chloride. The resulted thin-film composite membranes were thoroughly characterized using ATR-FTIR, AFM, SEM, EDX, WCA, and Zeta potential. The filtration performance of 0.025 PPSAPO and 0.05 PPSAPO membranes has presented higher permeate flux of 60 and 64 LMH respectively when compared to control PP (33 LMH). In addition, fabricated membranes showed higher rejection (more than 95%) for divalent ions and lower rejection (about 20% at 15 bar) for monovalent ions, demonstrating divalent selectivity. Similarly, the new membranes demonstrated equal or better rejection of pharmaceutical pollutants compared to the control membrane. Furthermore, the membranes have presented excellent chlorine stability (500 ppm, NaOCl) up to 16–32 h compared to 4 h for the control membrane.