Today, it is both very difficult and very expensive to treat water containing the toxic per- and polyfluoroalkyl substances (PFAS). The problem is their very small concentrations in water, and this makes it very difficult to capture the toxic substances and remove them.

A research project with funding from Independent Research Fund Denmark’s Green Research pool will now try to solve this problem. The project is being carried out by researchers from Aarhus University and Aalborg University, and it aims to develop a system to make the process of capturing and removing PFAS significantly easier.

"We hope to capture PFAS compounds in water, so we can break them down. We’ll be using a specially developed membrane that can detect these substances," says Associate Professor Mads Koustrup Jørgensen from the Department of Chemistry and Bioscience at Aalborg University, who is the main researcher behind the project.

The membrane is a filter coated with glucose. This binds the PFAS compounds so that they remain on the membrane. The PFAS can then be released into a concentrated fluid stream and become part of advanced oxidation processes with specially designed nanomaterials that can break down the otherwise notoriously strong carbon-fluorine bonds that make these substances ‘forever chemicals’.

"We will use oxidation to break down the PFAS compounds. We’ll be using ultraviolet light to initiate the process and drive the catalytic reaction," says Assistant Professor Zongsu Wei, from the Department of Biological and Chemical Engineering at Aarhus University, who is the project specialist in PFAS compounds.

Zongsu Wei has previously developed a new carbon-nano material that can completely break down PFAS into non-harmful components, and the process will work using this material.

Besides being far simpler and cheaper than existing technologies, the degradation method is also sustainable.

"This technology uses significantly less energy than current treatment techniques, and we can use it to realise our goal to completely degrade PFAS,” says Zongsu Wei.

FACTS:

The state threshold value for the level of concentration of a number of PFAS compounds in drinking water is just 0.002 micrograms per litre. This concentration corresponds to a maximum of 2 grams of PFAS in 1 million cubic metres of water. When concentrations are so small, it is difficult to directly treat and remove PFAS in drinking water, for example.

PFAS is extremely difficult to break down in nature, but the substances bind to a type of glucose called cyclodextrins. The researchers will coat cyclodextrins onto a membrane that can then collect PFAS in a water stream. This could be in connection with PFAS-contaminated groundwater, in water-containing processes in industry or when remediating contaminated soil, after which the water can be run through the membrane for treatment. Part of the research project is about finding out how to get cyclodextrins to stick to the membrane, and another part concerns how to release the PFAS compounds from the membrane again once they have been captured.

After the membrane has collected PFAS, it can be released into a concentrate, which can be then efficiently treated to break down the PFAS using Zongsu Wei’s technology. The aim is to break down PFAS into fluoride, CO₂ and water by using ultraviolet light-initiated reactions.

Contact

Assistant Professor Zongsu Wei
Aarhus University, Department of Biological and Chemical Engineering
Mail: zwei@bce.au.dk
Tel.: +45 93522047