How engineers are removing toxic ‘forever chemicals’ from the environment

Once celebrated for adding impressive new properties to everyday products, such as non-stick surfaces and water resistance, public perception of ‘forever chemicals’ has changed in recent years as we have learned more about their negative effects.

Known to be extremely persistent in the environment, some per- and polyfluoroalkyl substances (PFAS) are linked with human health concerns including reduced fertility and increased cancer risk. Animals in polluted environments are also at risk, with a recent study by the Norwegian University of Science and Technology showing that PFAS can alter ducklings’ genes before they are born.

PFAS polymers, larger molecules within the group, are considered less toxic – but even those can release greenhouse gases and substances that degrade the ozone layer during production, along with toxic byproducts.

As the European Union explores comprehensive restrictions on PFAS, recent research by environmental magazine Ends Report and The Guardian found that chemical producers are urging the UK to allow continued use of fluoropolymers, part of the PFAS polymer group. Claims that they are less harmful than other types are disputed by industry experts, with Dr Shubhi Sharma, scientific researcher at chemicals charity Chem Trust, telling The Guardian that “fluoropolymers are far more concerning chemicals than the industry claims”.  

While the tug of war between researchers and commercial operators is set to continue, engineers around the world are already working to remove toxic forever chemicals from the environment.

An important first step is knowing when they are present, and a recent project by researchers at the University of Chicago and Argonne National Laboratory could provide a solution. The team developed a portable device that uses unique probes to quantify levels of PFAS, reportedly completing measurements in minutes instead of weeks. Capable of detecting PFAS at 250 parts per quadrillion – the equivalent of finding one grain of sand in an Olympic swimming pool – the device uses a silicon chip that changes electrical conductivity when a PFAS molecule attaches.

Identification is only part of the challenge, however, with capture and destruction of molecules the obvious next step. New options include a material developed at Rice University in Texas that can reportedly capture PFAS 1,000 times better than other materials, and 100 times faster than commercial carbon filters. The layered double hydroxide material of copper and aluminium “create an ideal environment for PFAS molecules to bind with both speed and strength”, a Rice announcement said. The saturated material can then be heated with calcium carbonate, eliminating more than half of the trapped PFAS.

The best solution for the environment is one that prevents forever chemicals from leaking out in the first place. Several products are already destroying PFAS in concentrated waste streams, tackling the problem of disposal. These include the ForeverGone ‘PFAS destruction platform’ from Massachusetts-headquartered Gradiant, which was recently installed at Munich International Airport.

Designed to eliminate forever chemicals from industrial wastewater, the platform pairs techniques known as micro-foam fractionation and advanced electro-oxidation. The first injects billions of microbubbles into contaminated water to separate and concentrate PFAS into a ‘micro-foamate’, before the second destroys the concentrate using proprietary electrodes. Together, Gradiant says, the processes can achieve 99 to 99.9% removal, including short-chain PFAS that some older technologies miss.

Other techniques include supercritical water oxidation, which uses extreme pressure and heat to break down organic materials including PFAS, and a hydrothermal alkaline treatment developed at the Colorado School of Mines.  

Despite the progress, a recent review by researchers at North China Electric Power University and collaborators found that “significant challenges remain” in treatment technologies, including high energy demands, engineering scaleability and the formation of further potentially toxic byproducts.

Beyond treatment, an even more appealing option is development of new materials that provide similar properties to PFAS without the negative effects on health and the environment. Created with funding from the EU’s Horizon 2020 programme and the Swedish government, an open-access database published last year documented all known uses of PFAS and listed potential alternatives that could deliver the same or similar functions.

The database also revealed areas where more innovation is needed, including 83 applications that lack forever chemical alternatives. These were most common in industrial processes such as plastic and rubber production, the research authors said in the American Chemical Society’s Environmental Science & Technology.

In electrolytic hydrogen production, for example, electrolysers often use a PFAS called Nafion in their membranes. Researchers at Columbia University in New York City aim to provide a PFAS-free alternative using silicon dioxide and nanoscale manufacturing techniques.

Other potential replacements for forever chemicals include non-toxic alternatives for water-repellent surfaces, non-stick surfaces with reduced PFAS levels, thanks to nanoscale fletching, and processed cottonseed oil for fabric finishing.  

While new materials and techniques could offer sustainable alternatives, the intrinsic long-lasting nature of PFAS and lobbying by producers means they are likely to remain in environments around the world for the foreseeable future. More engineering solutions will be needed to protect human health and under-pressure natural habitats, while also providing useful products.