The study proposes to use them as anion-exchange membranes for water treatment

The researcher Amaia Ortiz de Lejarazu defended her doctoral thesis on Friday 18th. The objective of this work, entitled Anion-exchange membranes from end-of-life reverse osmosis membranes: indirect recycling approach for a circular water sector, is the preparation of ion-exchange membranes on discarded membranes and their application in water treatment and aims to contribute to a circular economy as part of the objectives established by the European Commission through the European Green Deal. The dissertation has been directed by Serena Molina Martínez and Juan Manuel Ortiz Díaz-Guerra, IMDEA Water researchers, within the Doctoral Programme in Hydrology and Management of Water Resources, coordinated by the University of Alcalá in collaboration with Rey Juan Carlos University.

The increase of end-of-life reverse osmosis (RO) membrane modules yearly dumped in landfills comprises an important environmental concern. In this context,  the development of innovative membrane reuse and recycling alternatives can help reduce the waste generated and foster the transition towards a circular economy in the water sector. 

Previous studies have focused on membrane reuse and direct recycling alternatives. However, an indirect recycling approach—deconstructing the RO module and extracting and managing its components individually—could represent a more suitable alternative for excessively damaged membranes. 

In this context, the research focuses on developing innovative alternatives for the reuse and recycling of membranes to reduce waste generation and promote the transition towards a circular economy in the water sector. The technical feasibility of the developed membranes has been validated under different water treatment processes, such as brackish water desalination by electrodialysis, selective counter ion separation and nitrate transport by Donnan dialysis, and simultaneous removal in a bioreactor of ion exchange membrane bioreactor.

The results obtained show that the use of these membranes could represent a more affordable alternative to commercial ones, opening a new path to its use in electrochemical separation processes such as the recovery of nitrate from wastewater or obtaining drinking water for irrigation or industrial purposes.

Amaia Ortiz de Lejarazu Larrañaga joined the Membrane Technology group at IMDEA Water in 2015. Since then, she has participated in the INREMEM project (Innovation and recycling of membranes for water treatment) and INREMEM 2.0 (Hybrid wastewater treatments based on recycled membranes with the objective of zero liquid discharge (ZLD)).