(280d) MIL-100 (Fe) Functionalized Thin-Film Nanocomposite Membranes for Enhanced Removal of Uncharged Urea from Water

Urea is widely used in fertilizer production for agricultural purposes which risks runoff into soil and water sources. This poses a concern due to the algal blooms that may form which can poison the environment and even humans due to food source contamination. 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. Adsorptive membranes combine the power of membrane filtration with the adsorption process and provide enhanced selective removal specifically for small and uncharged molecules. Metal-organic frameworks (MOF) are a new generation of effective adsorbents with excellent tuneability in structure and compatibility with polymeric membranes. We synthesized MIL-100 (Fe), an iron-based MOF using heatless method, and tested for urea adsorption. The urea adsorption capacity of MIL-100 (Fe) was tested under varying experimental conditions such as pH (2-10), temperature (25-45°C), MOF concentration (25-400 ppm), and urea concentration (10-1000 ppm). The results revealed the superfast adsorption (reached almost 90% removal within 1 min) of neutrally charged urea molecules. The MOF was able to reach a maximum adsorption efficiency of around 98% with a maximum uptake capacity of 4430 mg/g. In this project, we (i) immobilized the MIL-100 (Fe) on the surface of the polyamide layer of thin-film composite membranes and (ii) incorporated the MIL(Fe) into the polyamide selective layer of TFC for the fabrication of two different types of adsorptive membranes for enhanced removal of urea from water. The urea rejection, water permeability, and antifouling of these two functionalized membranes will be examined and compared with the bare TFC membrane. In addition, the effect of Fe-MOF on the formation of polyamide selective layer structure and morphology will be discussed regarding the impact of Fe-MOF on the interfacial polymerization process.