Protective Alumina Nanolayers Enhance Ozone Resistance of Polyamide Reverse Osmosis Membranes

Water scarcity is an escalating global challenge, leaving billions without consistent access to clean water. Desalination, particularly through reverse osmosis (RO), has become a critical method of producing fresh water from saline sources. However, thin-film composite (TFC) polyamide (PA) RO membranes, the industrial desalination standard, have a high propensity for biofilm formation, which leads to biofouling, reducing efficiency and increasing energy demand. Ozone disinfection is a simple, effective method to control biofilm development; however, PA membranes undergo chemical degradation when exposed to oxidizing disinfectants, even at very low concentrations. This work presents a novel approach to enhancing the durability of TFC-PA membranes against ozone. This was achieved by applying ultrathin alumina coatings via atomic layer deposition (ALD) on the membrane surface, creating a protective layer that provides active and passive defense against oxidative damage. The thin-film alumina-coated membrane at optimal coating demonstrated 5-fold higher tolerance to ozone exposure than uncoated membranes. They also maintained stable water permeate flux and salt rejection after prolonged filtration and effectively prevented biofilm formation. These findings offer a promising pathway to enhancing the sustainability of RO membranes by addressing critical barriers to their long-term desalination performance, thereby contributing to addressing the problem of global water scarcity.