Sacrificial membranes in water purification: Concepts, current status, and outlook

Sacrificial membranes typically contain a regenerable surface layer that is designed to address one or more of the critical limitations of membrane separation, such as fouling, low chlorine resistance, and poor selectivity towards certain contaminants. By enabling in-situ removal of fouled, damaged, or spent surface layers, regeneration of the sacrificial membrane can be achieved by depositing a fresh surface layer on the base membrane. In this review, we first review the materials that are currently being studied and evaluated for sacrificial membrane applications and identify new promising materials. Then, we discuss the application of sacrificial membranes to control fouling, increase chlorine resistance, and improve targeted contaminant removal. In particular, we discuss the promise of sacrificial multi-functional membranes that utilize functional materials to remove contaminants by adsorption or reaction simultaneously during filtration. Finally, we conclude with a discussion of regeneration strategies for sacrificial membranes and an outlook on opportunities and challenges in the field. The most promising regeneration strategies for removing spent layers and redepositing new ones are the in-situ procedures that align with the routine cleaning protocols widely adopted by the membrane industry.