Forever chemicals captured and destroyed in single process

Researchers from the University of Illinois-Champaign in the USA have created a single-step device for capturing and destroying diverse per- and polyfluoroalkyl substance (PFAS) chemicals that uses redox electrodialysis and electrosorption.

Desalination technology the key

The method is capable of capturing, concentrating, and destroying diverse PFAS chemicals in water using a single process, including common ultra-short-chain PFAS.

A previous study at the university had proved that short and long-chain PFAS can be removed from water using electrochemically driven adsorption – known as electrosorption. However, the study had fallen short of being able to destroy ultra-short-chain molecules because of their size and their differing chemical properties.

The latest study, published in Nature Communications, led by chemical and biomolecular engineering professor Xiao Su, combines electrosorption with redox electrodialysis - a desalination filtration technology.

Su was assisted in the research by Nayeong Kim, Johannes Elbert and Ekaterina Shchukina.

Fouling PFAS that act like ions

The combination of technologies addressed the problems of capturing and destroying PFAS of all chain lengths. However, the team initially reached an obstacle when utilising their previous highly efficient electrodialysis devices that had successfully been used to remove various non-PFAS contaminants.

The process required ion-exchange membranes, which are expensive and were quickly fouled by the PFAS molecules. To clear the membrane hurdle, Su's team introduced an inexpensive nanofiltration membrane that enables the electric field-driven removal of PFAS without becoming fouled.

This technology is based on previous research conducted by the team which combined redox polymers with nanofiltration membranes to enable energy-efficient desalination.

Su told media: "We decided upon redox electrodialysis because the very short-chain PFAS behave a lot like salt ions in water."

He added: "The challenge was to produce an efficient, effective electrodialysis system to capture the ultra-short-chain PFAS, have it work in tandem with the electrosorption process for the longer-chain PFAS, destroy them with electrochemical oxidation, and make it happen within a single device."

Finding the perfect configuration for PFAS destruction

The removal process begins with the desalination process, Su told media: "After experimenting with a variety of device configurations, we finally settled on a system that desalinates the PFAS-contaminated water to remove the ultra-short-chain molecules, then at the same time, carbon electrodes remove the remaining short- and long-chain molecules."

This process concentrates the PFAS, making them easier to destroy through the electrochemical oxidation process inherent in redox electrodialysis. The process converts the PFAS to fluoride ions, a key step towards eliminating these persistent contaminants from the environment.

Su explained the importance of successfully scaling the technology: "This work is very timely due to interest from the U.S. government, wastewater treatment facilities, and the semiconductor industry."

He added: "Semiconductor production is expected to rise over the coming years, and PFAS abatement for sustainable production will become a major issue moving forward."