In brief

Using covalent adaptable networks with thermally reversible Diels-Alder adducts, researchers developed water purification membranes that can be reused multiple times without losing effectiveness, thereby reducing waste.

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Clean water and a cleaner planet

1 Mar 2024

A first-of-its-kind recyclable water filtration membrane enables more sustainable practices in wastewater management.

Singapore, an island nation surrounded by seas, faces the paradox of water scarcity. The availability of potable water largely depends on wastewater reclamation and seawater desalination, processes that hinge on membrane filtration technology.

“The substantial application of membrane technology accounts for 70 percent of Singapore’s current water supply, a figure projected to increase to 85 percent by the year 2060,” commented Bofan Li, a Scientist at A*STAR’s Institute of Sustainability for Chemicals, Energy and Environment (ISCE2).

However, the frequent replacement of filtration membranes—essential for optimising efficiency—results in over 28,000 tons of waste annually, significantly contributing to CO2 emissions. Sustainable wastewater treatment practices have, in recent years, pivoted towards biodegradable membranes. Still, challenges in the design phase and end-of-life management have hindered progress, particularly in procedures to recycle used membranes.

Li’s team at ISCE2 worked with colleagues at the National Taiwan University of Science and Technology to address these challenges head-on, exploring sustainable materials and membrane structures resilient enough to withstand the demanding conditions of wastewater treatment. For example, Li listed high mechanical, thermal and chemical stabilities alongside effective separation performance as prerequisites for industry-ready membranes.

“Our focus extended beyond just assessing the thermal and mechanical properties of the materials,” Li stated. “We also considered their stability for practical uses and on-demand recyclability.”

Drawing on covalent adaptable networks (CAN) with thermally reversible Diels-Alder adducts, Li and colleagues developed robust, adaptable polymer-based materials for water filtration membranes. This system works by using special chemical bonds that can be reversed with heat. When heated, the membrane's molecular structure breaks down, allowing contaminants to be removed. After cleaning, new membranes can be refabricated using the recycled polymer, restoring its structure.

This recyclable process enables the membrane to be reused multiple times, reducing waste and improving sustainability in water purification. Li’s team also demonstrated that the new CAN-membranes featured comparable filtration performance to conventional membranes for at least three cycles.

This breakthrough ushers a new era in eco-friendly wastewater treatment membranes, which Li emphasised addresses both disposal concerns and aligns with circular economy principles.

Working towards a goal to achieve industrial-scale membrane production that is both accessible and affordable, the team is currently optimising membrane performance and manufacturing consistency. “Our roadmap ahead is to go from establishing structure-performance relationships, to morphology control, to application exploration and finally, to industrialisation,” concluded Li.

The A*STAR-affiliated researchers contributing to this research are from the Institute of Materials Research and Engineering (IMRE) and the Institute of Sustainability for Chemicals, Energy and Environment (ISCE2).

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Li, B., Wang, S., Loh, X.J., Li, Z. and Chung, T.-S. Closed-loop recyclable membranes enabled by covalent adaptable networks for water purification. Proceedings of the National Academy of Sciences 120 (15), e2301009120 (2023). | article

About the Researchers

Bofan Li obtained her BEng (2016) and PhD (2021) in chemical engineering from the National University of Singapore. She is currently a Research Scientist at A*STAR’s Institute of Sustainability for Chemicals, Energy and Environment (ISCE2). Her research interests are focused on the design and development of smart and sustainable membranes for water purification and organic solvent separations.
Zibiao Li is the Director of the Sustainable and Green Materials division at ISCE2 where he leads a research group working on sustainable polymers towards a circular materials economy. Li holds a joint appointment at the Institute of Materials Research and Engineering (IMRE) and is an adjunct Associate Professor at the National University of Singapore. His research interests focus on materials sustainability and MedTech polymers for healthcare applications.

This article was made for A*STAR Research by Wildtype Media Group