(387f) FO Separations with High-Performance TFC Membranes and Novel Draw Solutes

Forward osmosis (FO), an emerging membrane separation process utilizing the difference of osmotic pressure between the feed and draw solution as the driving force, has drawn growing attention ascribed to its unique advantages of relative low energy consumption, high water recovery, and low fouling propensity. Nevertheless, the development of a high-efficient FO system is still hindered by the lack of sustainable high-performance FO membranes and suitable draw solutes. Thin-film composite (TFC) membranes with excellent separation performance and convenient fabrication technology, have gained much attention in FO applications recently. Despite this, traditional TFC membranes formed by TMC and MPD still face problems of insufficient hydrophilicity and the permeability-rejection trade-off phenomenon. In our work, the surface modification by various hydrophilic amine monomers has been performed to improve the membrane water permeability and anti-fouling property. In-situ modification with various tertiary amines as the aqueous phase additives is also investigated, which can act as the catalyst to accelerate the interfacial polymerization. In comparison with the control TFC membrane, these modified membranes have the higher water flux, lower reverse salt flux and enhanced fouling resistance because of the smoother surface, as well as the thinner and denser PA layer with the higher crosslinking degree. In addition, the selection of proper draw solution is also crucial to guarantee a high-performance FO process with minimal reverse solute flux and easy draw solution recovery. Here, series of organic salt draw solutes with adjustable chemical structure and optimized molecular size are synthesized and applied for FO process. The results show that the introduction of carboxyl and phosphate groups to the molecular structure of organic draw solutes is a simple and effective way to enhance the osmotic pressure and FO performance of the draw solutions.