Nanofiltration membrane incorporated with CaAlg interlayer and UiO-66-NH2 nanofillers for enhanced water permeance and PPCP removal

The growing concern over pharmaceutical and personal care products (PPCPs) in drinking water sources underscores a serious public health risk. Although polyamide (PA) nanofiltration (NF) membranes are highly effective at removing PPCPs, their performance for neutral and hydrophobic PPCPs requires improvement. To overcome this challenge, we fabricated a hydrophilic NF membrane containing a calcium alginate (CaAlg) hydrogel interlayer and UiO-66-NH 2 nanofillers (PA/UiO-66-NH 2 /CaAlg) to reduce membrane affinity for hydrophobic PPCPs. A fishnet-like structure was created on the membrane surface, which enhanced the effective area for filtration. Consequently, the water permeance of the PA/UiO-66-NH 2 /CaAlg membrane reached 22.7 L·m −2 ·h −1 ·bar −1 , representing an 83 % increase over the control thin-film composite (TFC) membrane. The hydrophilic CaAlg interlayer also restricted the diffusion of piperazine (PIP), thereby slowing its interfacial polymerization with trimesoyl chloride (TMC). This resulted in a highly hydrophilic PA film, evidenced by a water contact angle below 10°. The reduced adsorption of hydrophobic PPCPs on this hydrophilic surface diminished the driving force for their penetration. Furthermore, the inherent hydrophilicity of the CaAlg hydrogel interlayer suppressed the diffusion of hydrophobic PPCPs across the membrane. As a result, the removals for hydrophobic methylparaben (MP), propylparaben (PP), bisphenol A (BPA), and benzylparaben (BP) were significantly enhanced. The selectivity ( A/B ) for BPA increased by more than four times compared to that of the TFC membrane. This study demonstrates that integrating a hydrogel interlayer with MOF nanofillers offers a promising approach for developing high performance NF membranes that exhibit both improved water permeance and superior PPCP removal.