Advances in Membrane Materials and Processes for Desalination of Brackish Water
Purpose of Review: This review aims to succinctly summarize recent advances of four key membrane processes (e.g., reverse osmosis (RO), forward osmosis (FO), electrodialysis (ED), and membrane distillation (MD)) in membrane materials and process designs, to elucidate the contributions of these advances to the steadfast growth of brackish water membrane desalination processes. With detailed analyses and discussions, the ultimate purpose of the review is to shed light on the future direction of brackish water desalination using membrane processes. Recent Findings: Brackish water has widely varying particulate matter and boron contents, posing great risks of membrane fouling and excessive boron levels to the membrane desalination processes. Recent advances in these four membrane processes largely focus on improving fouling resistance, boron rejection, water flux, and energy efficiency. Aquaporin membranes and thin-film composite polyamide membranes incorporated with nanoparticles exhibit excellent performances for RO and FO, whereas super-hydrophobic membranes prove their great potentials for MD. While recent advances in RO and ED process designs are orientated towards membrane fouling prevention by exploring respectively novel energy-saving membrane-based pre-treatment and reversal operation, recent studies on FO and MD are centered on reducing the energy costs by advancing the fertilizer-drawn concept and utilizing waste heat. Summary: Membrane processes are dominating brackish water desalination, and this trend is hardly to change. Membranes based on nanoparticles and other novel materials are deemed the next membrane generation, and innovative membrane process designs have demonstrated great potentials for brackish water desalination. Nevertheless, further works are needed to scale up these novel membrane materials and designs.