Progress of Ultrafiltration-Based Technology in Ion Removal and Recovery: Enhanced Membranes and Integrated Processes

Toxic ions from industrial wastewater entail important challenges to the environment. Ultrafiltration (UF) with low operation pressure and high permeability has been widely used for macromolecules and suspended solids separation. However, UF cannot be directly used to separate ions from wastewater due to the large pore size of UF membranes. Recently, the design of enhanced UF membrane structures and UF-based integrated processes expands the application of UF for ion removal. This review aims to summarize the latest developments of UF membranes preparation as well as integrated UF processes in ion removal. First, the advanced materials for UF membranes preparation are discussed, with specific attention on active nanomaterials including inorganic materials, organic materials, and biomaterial-based materials. The design principles such as pore size control and composite thin layer fabrication of enhanced UF-based membranes for ion removal are illustrated. Next, integrated processes such as micellar-enhanced UF, polymer-enhanced UF, electro-driven UF, and other UF-based combined processes are reviewed. Finally, current application limitations and future perspectives in the enhanced UF membrane for ion removal are discussed. This review presents potential approaches for the preparation and application of enhanced UF membranes in sustainable ion removal from wastewaters.