PFAS and water remediation: current approaches to treating these "forever chemicals"
PFAS, or per- and polyfluoroalkyl substances, often referred to as "forever chemicals," pose a major environmental challenge due to their persistence and toxicity.
Today, in addition to better regulating their use, we need better ways to treat these pollutants, which means first extracting them from the environment and then destroying them. This is a real challenge, as these molecules are both highly varied and very resistant—which is what makes them so successful.
Julie Mendret, University of Montpellier and Mathieu Gautier, INSA Lyon – University of Lyon
Measures to regulate and ban PFAS emissions, which are essential to limit their spread in the environment, are already underway. According to a law passed in February 2025, France must aim to completely halt industrial PFAS discharges within five years.
Recently, an investigation conducted by Le Monde and 29 media partners revealed that decontaminating soil and water contaminated by these substances could cost between €95 billion and €2 trillion over a period of twenty years.
As with other organic contaminants, there are two main types of treatment processes.
Some technologies involve separating and sometimes concentrating PFAS from the polluted environment to enable the discharge of purified effluent, but they consequently generate by-products that still contain pollutants and need to be managed. Other technologies involve breaking down PFAS. These processes involve destroying the C-F (carbon-fluorine) bond, which is very stable and often requires high energy inputs.
In this article, we list some of the many processes currently being tested at different scales (laboratory, pilot, and even full scale), ranging from innovative materials that can sometimes simultaneously separate and destroy PFAS, to the use of living organisms such as fungi and microbes.
Processes for separating and concentrating PFAS in water
Currently, the techniques used to remove PFAS from water are mainly separation processes that aim to extract PFAS from water without breaking them down, requiring subsequent management of PFAS-saturated solids or liquid concentrates (PFAS-concentrated waste).
The most commonly used technique is "adsorption," which relies on the affinity between the solid and the PFAS molecules that attach themselves to the porous surface. Adsorption is an effective separation technique for many contaminants, including PFAS. It is widely used in water treatment, particularly because it is affordable and easy to use. The selection of the adsorbent is determined by its adsorption capacity for the targeted pollutant. Many adsorbent materials can be used (activated carbon, ion exchange resin, minerals, organic residues, etc.).
Among these, adsorption on activated carbon is very effective for long-chain PFAS but less effective for medium- and short-chain PFAS. After adsorption of PFAS, activated carbon can be reactivated by high-temperature thermal processes, which results in high energy costs and the transfer of PFAS to the gas phase, which must be managed.
The first mobile activated carbon PFAS treatment unit was recently deployed in Corbas, in the Rhône region, and can treat 50 cubic meters of water per hour to make it drinkable.
As another adsorption process, ion exchange resins consist of positively charged (anions) or negatively charged (cations) beads. PFAS, which are often negatively charged due to their carboxylic or sulfonic functional groups, are attracted to and can bind to positively charged anion exchange resins. Differences in efficiency have also been observed depending on the length of the PFAS chain. Once saturated, ion exchange resins can be regenerated by chemical processes, producing PFAS-concentrated waste streams that must be treated. It should be noted that ion exchange resins are not approved in France for use in drinking water production.
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The most effective technique currently available for removing a wide range of PFAS —both short-chain and long-chain—from water is filtration using nanofiltration or reverse osmosis membranes. Unfortunately, this technique is energy-intensive and generates separation by-products known as "concentrates." These concentrates have high PFAS concentrations, which makes them difficult to manage (concentrates are sometimes released into the environment when they actually require additional treatment).
Finally, foam fractionation flotation exploits the properties of PFAS (hydrophilic head and hydrophobic tail), which are placed at the air/liquid interface in foam bubbles and recovered at the surface. Extraction rates of 99% are thus achieved for long-chain PFAS. Like the previous techniques, this technique produces a concentrate that must be disposed of later.
Towards technologies that degrade PFAS
Other processes seek to break down contaminants in water in order to offer a more sustainable solution. There are various technologies for destroying pollutants in water: advanced oxidation processes, sonolysis, plasma technology, etc. These processes can be deployed to complement or replace certain concentration technologies.
The destruction of a pollutant is influenced by its potential for biodegradability and oxidation/reduction. The natural degradation of PFAS is very difficult due to the stability of the C-F bond, which has a low biodegradability potential (i.e., it is not easily destroyed by processes occurring in nature, such as those driven by bacteria or enzymes).
Advanced oxidation processes are techniques that use highly reactive free radicals that are potentially effective in breaking C–F bonds. They include ozonation, UV/hydrogen peroxide, and electrochemical processes, among others.
Electrochemical treatment of PFAS is an innovative and effective method for degrading these highly persistent compounds. This process involves applying an electric current through specific electrodes, generating powerful oxidizing radicals capable of breaking carbon-fluorine bonds, which are among the most stable in organic chemistry.
For all these advanced oxidation processes, one point must be monitored: the production of PFAS with shorter chains than the initially treated product must be avoided.
Recently, a company spun off from the Swiss Federal Institute of Technology in Zurich (Switzerland) developed an innovative technology capable of destroying more than 99% of PFAS in industrial wastewater through piezoelectric catalysis. The PFAS are first separated and concentrated by foam fractionation. The concentrated foam is then treated in two reactor modules where piezoelectric catalysis technology breaks down and mineralizes all short-, medium-, and long-chain PFAS.
Sonic-chemical degradation of PFAS is also being studied. When high-frequency ultrasonic waves are applied to a liquid, they create bubbles known as "cavitation bubbles," inside which chemical reactions take place. These bubbles eventually implode, generating extremely high temperatures and pressures (several thousand degrees and several hundred bars), which create reactive chemical species. The cavitation phenomenon is thus capable of breaking carbon-fluorine bonds, ultimately resulting in less harmful and more easily degradable components. Although very promising in the laboratory, it remains difficult to apply on a large scale due to its energy cost and complexity.
Thus, despite these recent advances, several challenges remain for the commercialization of these technologies, due in particular to their high cost, the generation of potentially toxic by-products that require additional management, and the need to determine the optimal operating conditions for large-scale application.
What are the prospects for tomorrow?
Faced with the limitations of current solutions, new avenues are emerging.
One approach is to develop hybrid treatments, i.e., combining several technologies. Researchers at the University of Illinois (United States) have, for example , developed an innovative system capable of capturing, concentrating, and destroying mixtures of PFAS, including ultra-short-chain PFAS, in a single process. By combining electrochemistry and membrane filtration, it is possible to combine the performance of both processes while overcoming the problem of concentrate management.
Innovative materials for PFAS adsorption are also being studied. Researchers are working on stereolithography 3D printing integrated into the manufacturing process of adsorbent materials. A liquid resin containing polymers and photosensitive macrocycles is solidified layer by layer using UV light to form the desired object and optimize the material's properties in order to improve its adsorption performance. These adsorbent materials can be coupled with electrooxidation.
Finally, research is underway on bioremediation to mobilize microorganisms, particularly bacteria and fungi, capable of degrading certain PFAS. The principle involves using PFAS as a carbon source to defluorinate these compounds, but degradation times can be long. This promising biological approach could therefore be combined with other techniques capable of making the molecules more "accessible" to microorganisms in order to accelerate the elimination of PFAS. For example, a technology developed by researchers in Texas uses a plant-based material that adsorbs PFAS, combined with fungi that degrade these substances.
Nevertheless, despite these technical advances, it remains essential to implement regulations and measures upstream of PFAS pollution in order to limit damage to ecosystems and human health.
Julie Mendret, Senior Lecturer, HDR, University of Montpellier and Mathieu Gautier, University Professor, INSA Lyon – University of Lyon
This article is republished from The Conversation under a Creative Commons license. Readthe original article.