Synergistic Effect of NiFe-LDH and PES/SPSf Matrix on Metal Ion Rejection Efficiency from Surface Water

Abstract

Clean water remains a pressing global challenge and developing membranes that are both efficient and durable is critical. This study combined two polymers, polyethersulfone (PES) and sulfone-modified polysulfone (SPSf), with NiFe-layered double hydroxides (LDHs) to create a new class of multifunctional membranes. The membranes were characterized using FTIR, SEM, water contact angle, and zeta potential. The addition of NiFe-LDH fillers improved the hydrophilicity and surface structure of the membranes and enhanced the separation performance of the resulting membranes. The best-performing membrane (M3, with 2 wt.% NiFe-LDH) delivered pure water flux of about 218 L.m^-2h^-1, which was nearly three times higher than that of the pristine PES/SPSf membrane. Furthermore, M3 removed approximately 92.4% of bovine serum albumin (BSA), attributed to the synergistic combination of size exclusion, electrostatic repulsion, and hydrophilicity. The membrane also showed excellent antifouling properties, maintaining over 65.9% and 71.2% flux recovery after three fouling-cleaning cycles for BSA solution and surface water, respectively. Importantly, the M3 membrane achieved high removal efficiencies for heavy metals, rejecting 91% of Cd²⁺, 93% of Pb²⁺, and 88% of Cu²⁺. These results highlight how the synergy between PES/SPSf and NiFe-LDH can overcome the common challenges of fouling and low metal ion rejection, offering a promising route toward practical and sustainable water treatment solutions.