Highly permeable and mechanically durable forward osmosis membranes prepared using polyethylene lithium ion battery separators

A porous polyethylene (PE) membrane commercialized as a lithium ion battery separator was utilized as a support for the fabrication of a highly permeable and mechanically durable thin film composite (TFC) forward osmosis (FO) membrane. The highly open and interconnected pore structure of the PE support combined with its thin thickness (~8 µm) is beneficial for mitigating internal concentration polarization, thus enhancing FO water flux. The proper plasma treatment on the PE support and the use of a surfactant enabled the stable formation of a polyamide permselective layer on top of the support via a commercial interfacial polymerization process. The prepared PE-supported TFC (PE-TFC) membrane exhibited a remarkably high FO performance (~3.5 times higher water flux and ~35% lower specific salt flux than the commercial HTI-CTA membrane in FO mode) due to its significantly low structural parameter (~161 µm) and high permselectivity. The PE-TFC membrane also had superior mechanical properties compare to the much thicker commercial FO membrane due to the exceptionally high mechanical integrity of the PE support, ensuring the mechanically stable membrane operation. The proposed strategy offers a new material platform for FO membranes with strong commercial potential and excellent performance and durability.