(117n) Poster: Thin-Film Nanocomposite Membranes Functionalized with Fe-Based Metal-Organic Frameworks for Enhanced Removal of Small and Uncharged Urea from Water

Urea is widely used in fertilizer production for agricultural purposes, which risks runoff into soil and water sources. Leaching of urea into water resources poses a concern due to algal bloom formation which can kill local wildlife and cause environmental eutrophication. Thin-film composite (TFC) membranes are among the best-performing membranes for water filtration; however, they do not show acceptable rejection for small and uncharged molecules such as urea. To combat this issue, adsorptive membranes combine the power of membrane filtration with adsorbent materials to provide enhanced selective removal, specifically for small and uncharged molecules. Metal-organic frameworks (MOF) are a new generation of effective adsorbents with excellent tunability in structure and compatibility with polymeric membranes. In this study, we synthesized MIL-100 (Fe), an iron-based MOF, using a mild room temperature method and tested for urea adsorption. The urea adsorption capacity of MIL-100 (Fe) was examined under varying experimental conditions such as pH, temperature, MOF concentration, and urea concentration. The results revealed the superfast adsorption (reached almost 90% removal within 2 min) of neutrally-charged urea molecules with a high adsorption capacity of 3321 mg/g and a BET surface area of 1174 m²/g. To fabricate the adsorptive membranes, the MIL-100 (Fe) was grafted on the surface of the polyamide layer of thin-film composite membranes via covalent binding for enhanced removal of urea from water. The MIL-100 (Fe)-TFC membrane showed enhanced permeability (14.10 vs 0.87 LMH/bar) and no significant decrease (47% vs 41%) in Mg salt rejection, indicating successful grafting without damaging the PA layer. In addition, although both bare TFC and MIL-100(Fe)@TFC showed similar rejection of 63% of urea, the MIL-100(Fe)@TFC adsorbed a portion of the urea compared to the bare TFC, which rejected it. The quantification of adsorption versus rejection is currently under investigation.