Novel Forward Osmosis Membranes Engineered with Polydopamine/Graphene Oxide Interlayers: Synergistic Impact of Monomer Reactivity and Hydrophilic Interlayers
Pooria Karami, Md Mizanul Haque Mizan, Behnam Khorshidi, Sadegh Aghapour Aktij, Ahmad Rahimpour, João B. P. Soares, Mohtada Sadrzadeh
Abstract
In this study, a series of polyamide membranes with improved water permeability and thermal stability for forward osmosis applications were synthesized with the main objective of tuning the chemical structure of the polyamide layer to enhance its resistance at higher temperatures. Constructing an interlayer over the substrate of thin-film composite membranes is a promising approach to have better control over the synthesis of a thin and smooth selective layer. Polyamide thin-film composite membranes equipped with polydopamine/graphene oxide interlayers were fabricated. To enhance the thermal stability of thin-film composite membranes, the selective layer chemical composition was modified by an amine monomer: triaminopyrimidine (TAP). The presence of an interlayer made the polyamide layer smoother and thinner. The FTIR spectra showed characteristic peaks for PDA/GO and polyamide, showing the successful formation of the interlayer and selective layer. XPS results demonstrated that the TAP monomers increased cross-linking of the polyamide by forming more amide linkages during the polymerization process. TAP monomers contributed to fewer structural variations of the polyamide layer at high temperatures, leading to a smaller increase in water flux and reverse salt flux of TAP-modified membranes by increasing the 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 reverse salt flux, respectively, with 1 M NaCl solution as the draw solution by increasing the temperature from 25 to 65 °C. However, thin-film composite membranes with no TAP showed 8.3 L/m 2 h and 6.1 g/m 2 h increases in water flux and reverse salt flux, respectively. Our results could be leveraged to develop novel forward osmosis membranes that can potentially dewater hot wastewater streams.