Novel Forward Osmosis Membranes Engineered with Polydopamine/Graphene Oxide Interlayers: Synergistic Impact of Monomer Reactivity and Hydrophilic Interlayers

Inthis study, a series of polyamide membranes with improved waterpermeability and thermal stability for forward osmosis applicationswere synthesized with the main objective of tuning the chemical structureof the polyamide layer to enhance its resistance at higher temperatures.Constructing an interlayer over the substrate of thin-film compositemembranes is a promising approach to have better control over thesynthesis of a thin and smooth selective layer. Polyamide thin-filmcomposite membranes equipped with polydopamine/graphene oxide interlayerswere fabricated. To enhance the thermal stability of thin-film compositemembranes, the selective layer chemical composition was modified byan amine monomer: triaminopyrimidine (TAP). The presence of an interlayermade the polyamide layer smoother and thinner. The FTIR spectra showedcharacteristic peaks for PDA/GO and polyamide, showing the successfulformation of the interlayer and selective layer. XPS results demonstratedthat the TAP monomers increased cross-linking of the polyamide byforming more amide linkages during the polymerization process. TAPmonomers contributed to fewer structural variations of the polyamidelayer at high temperatures, leading to a smaller increase in waterflux and reverse salt flux of TAP-modified membranes by increasingthe temperature. A membrane made with 2 wt % TAP showed 3.2 L/m(2)h and 3.5 g/m(2)h increases in water flux and reversesalt flux, respectively, with 1 M NaCl solution as the draw solutionby increasing the temperature from 25 to 65 & DEG;C. However, thin-filmcomposite membranes with no TAP showed 8.3 L/m(2)h and 6.1g/m(2)h increases in water flux and reverse salt flux, respectively.Our results could be leveraged to develop novel forward osmosis membranesthat can potentially dewater hot wastewater streams.