Recycling of end-of-life polymeric membranes for water treatment: Closing the loop

Polymeric membranes have garnered widespread adoption in applications such as desalination, wastewater treatment, and water reuse. Nevertheless, the current disposal practices for these end-of-life (EoL) polymeric membranes, primarily landfill and incineration, are neither economically nor environmentally sustainable. To address this challenge, we first analyzed the factors leading to the EoL phase for these membranes; an understanding that is critical in developing or selecting appropriate recycling technologies. We further proposed a technological framework to guide recycling choices based on the specific state of the EoL membrane. In cases where the membrane exhibits significant breakage, dissolution using eco-friendly solvents, followed by membrane re-preparation, is recommended. For membranes without substantial breakage, regeneration, upcycling, or downcycling strategies can be deployed based on scenarios. We underscored the crucial role of irrecoverable foulant removal within the regeneration technology. Additionally, the reaction interface must be suitably remediated before the application of upcycling technology to EoL microfiltration/ultrafiltration membranes. The downcycling strategy, facilitated by NaOCl oxidation, is readily applicable to EoL nanofiltration/reverse osmosis membranes. This brief frontier review aims to serve as a valuable reference for recycling end-of-life water treatment polymeric membranes.