Thin-Film Nanocomposite Forward Osmosis Membranes Prepared on PVC Substrates with Polydopamine Functionalized Zr-Based Metal Organic Frameworks

In this study, UiO-66-NH2 metal–organic frameworks (MOFs) were modified by a mussel-inspired approach to yield polydopamine (PDA)–MOF hybrid nanoparticles (NPs) and then embedded within a polyamide (PA) layer to synthesize thin-film nanocomposite (TFN) membranes for desalination and heavy metal removal. The PA layer was fabricated via interfacial polymerization (IP) reaction between PDA/m-phenylenediamine (MPD) aqueous solution and trimesoyl chloride (TMC)/MOF organic solution on the low-cost PVC substrate. First, various zirconium-based MOFs (Zr-based MOFs) were synthesized with manipulating the dopamine (DA) concentration. Then, after selecting the best NPs (MOF@PDA(0.25)), the effects of different loadings of the selected NPs on the FO performance were evaluated. In comparison to the conventional thin film composite (TFC) membrane (15.95 L/m2 h) using DI water as a feed solution (FS) and 1 M NaCl as a draw solution (DS), incorporation of MOF@PDA(0.25) led to enhanced water flux of the TFN membrane (29.73 L/m2 h) without sacrificing selectivity due to the establishment of extra water channels and improvements in both hydrophilicity and compatibility between NPs and the PA layer. Finally, the modified membranes demonstrated outstanding performance for desalination and heavy metal (Cu2+ and Pb2+) removal. The rejection displayed the trend of Cu2+ > Pb2+ for all of the fabricated membranes.