Toxic PFAS are endangering our water. Now there are plans to ban them in Europe. This presents the industrial sector with major problems because these “forever chemicals” are essential to many products and processes.
© Fotografie: Jan von Holleben
Web special Fraunhofer magazine 4.2023
PFAS have been hailed as a magic bullet in the industrial sector for more than 70 years. But in early 2023, the European Chemicals Agency (ECHA) announced that their days were numbered. It has recommended that the European Commission place a ban on per- and polyfluoroalkyl compounds, and to do so as quickly and extensively as possible. “Since the ECHA made its announcement, companies have been practically banging on our door,” says Dr. Stefan Löbbecke, spokesperson for the Fraunhofer Chemistry Alliance. He reports that the number of inquiries regarding substitute chemicals and environmental and human toxicology assessments for various PFAS materials, as well as recycling, filtering and cleaning technologies, has increased exponentially in recent months. On serious note, Löbbecke adds: “I can understand companies’ concerns and hardships, with some of them feeling a ban is a threat to their very existence.” PFAS can be found in everyday products like coated pans, pizza boxes and outdoor jackets, as well as in medical devices, heat pumps and batteries.
As process chemicals, PFAS are used in the semiconductor industry to etch patterns in microchips, for example. They repel water, dirt and oil, they can withstand high temperatures and aggressive chemicals, and they are resistant to bacteria and light. Almost no other chemical substance can compete with them, so unique are their properties – and this explains why they are used so frequently. PFAS now come in many different variants, numbering around 15,000 substances according to the U.S. Environmental Protection Agency.
But while these colorless, odorless and tasteless substances can be used in a wide range of applications, they have also been found to be toxic in many cases. They can cause cancer and infertility and weaken the immune system. What’s more, the industrially produced, extremely stable carbon-fluorine bonds characteristic of PFAS are not found in nature and cannot be decomposed. Once they are released into the environment, PFAS stay there forever, which is why they are often called “forever chemicals” in public debate. A study conducted by the German Environment Agency (UBA) in 2020 tested children between the ages of 3 and 17 and found PFAS in the blood of every test subject.
Despite all of the risks, in many applications it would be impossible to stop using PFAS overnight. Nevertheless, researchers at Fraunhofer are working on a range of projects aimed at developing alternatives, reducing PFAS contamination in the environment over time and using improved filtering and cleaning technologies to ensure that fewer forever chemicals end up in watercourses, organisms and soil, where they can accumulate and spread.
It is important that risk assessments differentiate between the individual compounds so that those that pose a particularly high risk potential to people and the environment are removed from circulation sooner. In the case of PFOS (perfluorooctane sulfonate), PFOA (perfluorooctanoic acid) and PFHxS (perfluorohexanesulfonic acid), this has already happened. They are only permitted for use in a small number of exceptional cases. Since February 25, 2023, restrictions have also been imposed on perfluorinated carboxylic acids – of which PFNA (perfluorononanoic acid) is the best known – affecting how they are placed on the market, manufactured and used.
The substances all belong to the class of PFAS, which are made up of long carbon chains. They accumulate in organisms along the food chain and are rarely excreted.
Human beings come at the end of the food chain. The substances bind to the proteins in human blood, in the kidneys and liver, where they remain for many years and can have a harmful effect. During pregnancy, they are transferred to the unborn child through the placenta and even passed on through breast milk.
In many cases, the industrial sector has now switched to short-chain PFAS, which are made up of a maximum of six perfluorinated carbon atoms. These accumulate in the organism to a lesser extent but they are more mobile. They are not retained in the soil and quickly enter the groundwater, which is often used for the drinking water supply.
The Fraunhofer Institute for Toxicology and Experimental Medicine ITEM is working with 15 European partners in the ZeroPM project, which aims to identify the potential risks of different PFAS in drinking water. Dr. Annette Bitsch, head of section for chemical safety: “It is not a trivial thing to say that one substance is more dangerous than another. It is important to take a comprehensive view of the individual substances. A fundamental principle in toxicology is that the risk is calculated on the basis of the inherent danger posed by the substance and the degree of exposure, or how often you come into contact with it.” To this end, she is analyzing study data and scientific publications. “In this process, it becomes clear fairly quickly which substances are critical.” She adds that it comes as little surprise, therefore, that the use of PFOS, PFOA, PFHxS and PFNA has been restricted first.
The European Food Safety Authority (EFSA) also focused on these four compounds in its most recent report from 2020 and defined a threshold value for the maximum weekly intake that is considered to be not harmful to health. This is 4.4 nanograms per kilogram of body weight. “This is equivalent to only around 0.00003 milligrams per person per day,” explains Bitsch. The substances are most frequently found in drinking water, fish, fruit, eggs and egg products.
When it comes to the plan put forward by the European Chemicals Agency (ECHA) to apply the restrictions to all PFAS in the near future, Bitsch expresses her understanding: “That is a huge class of substances with many subcategories. It will take decades for them all to undergo thorough toxicology assessments. We can’t wait that long.” She adds that exceptions are still possible, such as if a substance is needed in certain medical applications, if an assessment of the benefits and risks suggests continued use is preferable, or if it has been scientifically proven that a substance is harmless. However, the burden of proof rests with the industrial sector, she says.
The urgent need for an EU regulation has also been confirmed by the most recent research findings from the Fraunhofer Institute for Molecular Biology and Applied Ecology IME, which were published in January 2023. In the SumPFAS study carried out on behalf of the German Environment Agency (UBA), the researchers conclude that PFAS are much more widespread than previously thought. Dr. Bernd Göckener, head of department for Trace Analysis and Environmental Monitoring at Fraunhofer IME: “Even in smaller rivers, we found large quantities – including of lesser known PFAS. The problem is often no longer local but general. PFAS are simply everywhere.”
Together with his team, he examined around 200 samples of suspended solids and sediment from 170 rivers and lakes across Germany and compared them with archived samples from the German Environmental Specimen Bank, which has been documenting chemical pollution in the environment and in human beings since the 1980s. The good news is that pollution of the watercourses with PFAS has reduced; the EU bans are working. The bad news is that when Göckener and his team used a modified analysis that includes precursors, they found that overall PFAS concentrations were up to 346 times higher than when conventional investigation methods were used. Once they are released into the environment, precursors oxidize to form conventional PFAS. Göckener: “From an analytical perspective, we will never fully understand these thousands of substances. We assume that the level of pollution is much higher than we are able to measure.”
Göckener and his team found particularly high levels of PFAS downstream of large wastewater treatment plants and industrial facilities that produce or process PFAS. The forever chemicals enter rivers primarily through wastewater and eventually end up in the North Sea or Baltic Sea. “The oceans are the great reservoir for all PFAS around the world. This is where they will continue to accumulate,” Göckener believes.
That’s unless alternatives to PFAS are successfully developed so that the continuous influx can at least be reduced. Dr. Jakob Barz at the Fraunhofer Institute for Interfacial Engineering and Biotechnology IGB is working on this very task. He is using plasma technology to functionalize different material surfaces in order to make them chemically stable or resistant to dirt, water and ice. Barz: “Strictly speaking, PFAS coatings are not needed in many applications. The only thing we haven’t got right yet is a really effective oil-repellent function.” He adds different chemical substances to the plasma depending on the characteristic profile required. “The molecules are broken up. The individual fragments react on the surface of the material, where they form a polymer layer.
The type of polymer created always depends on the substances I add to my plasma, and on the process conditions.” One advantage of the plasma coating is that it can be applied in a very thin layer, like a film on the surface. Textures and pores are retained without being blocked, making this method ideal for coating solder stencils for computer circuit boards or membranes for use in wastewater filtration. These are both applications in which PFAS are used today.
For water-repellent coatings on outdoor fabrics, the researchers at Fraunhofer IGB use a biobased, sustainable substitute: chitosan. This forms a robust shell around the fibers, thereby improving the wear resistance. It can be obtained from various sources, including crustaceans. The EU sees around 250,000 tons of crustacean shell waste every year, over 6 million tons accumulate annually worldwide – a natural resource in abundance. Insect cuticles and exoskeletons, a common residue from animal foodstuff production, contain chitin, from which chitosan is made. “Chitosan is much more reactive than chitin. We use this to our advantage. We apply it to the fabric at the same time as water-repellent vegetable oils. With the application of heat and pressure, the substances bond to form an even and robust protective layer,” explains Dr. Thomas Hahn, deputy head of the Bioprocess Engineering working group at Fraunhofer IGB. His colleague Dr. Achim Weber adds: “The ingenious thing is that our impregnation – which is based on natural products – can be easily reactivated after cleaning it in the washing machine by ironing the fabric or putting it in the dryer.” Another advantage is that the formulation is simple to apply using the machines and production technologies already available in the textile industry. “Chitosan is also an effective solution for food packaging or coated boxes to protect washing powder from moisture and clumping, for example,” says Weber. PFAS can be safely dispensed with in this case too, he says.
However, the forever chemicals have so far been indispensable to the energy transition. Whether used in electrolyzers to obtain hydrogen, or in fuel cells and batteries, membranes that contain PFAS can be found everywhere. They need to offer properties such as high chemical stability and special levels of conductivity and permeability. “The material requirements are extreme,” says Dr. Taybet Bilkay-Troni, head of the Polymers and Electronics department at the Fraunhofer Institute for Applied Polymer Research IAP. Nevertheless, she and her team are looking for alternatives – and they have already succeeded. Together with the Center for Fuel Cell Technology ZBT, they have developed a new type of polymer and used it to produce membranes for anion-exchange membrane water electrolyzers (AEM-WE).
As Bilkay-Troni explains: “The membrane is at the heart of any electrolyzer. It is crucial to the reliability and effectiveness of the electrolysis process, or in other words, the process of splitting water into hydrogen and oxygen using electricity.” In addition to the membrane, electrolysis requires two electrodes (anode and cathode), a source of direct current and an electrically conductive fluid called the electrolyte. The positively charged hydrogen collects on the cathode, while the negatively charged oxygen collects on the anode. The membrane ensures that the negatively charged ions – or anions – are transported, and separates the anode and cathode chambers. The electrolyte is a weak lye, with electrolysis taking place at temperatures of around 60 to 80 degrees – operating conditions to which the membrane is continuously exposed. Nevertheless, it must not become brittle and should retain its flexibility and ionic conductivity.
The initial results in the electrolysis test cell are promising, with the PFAS-free membrane remaining stable. The new polymer that is used to make the membrane can also be processed very effectively. Another advantage is that there is no need to use costly electrodes made from rareearth metals, such as those required in proton-exchange membrane electrolysis, which is commonly used today. In the future, the membrane could also be used in fuel cells. “But before we get there, a few more development steps are needed,” adds Bilkay-Troni. “We are just at the beginning of our research. Next, we want to work with our partner ZBT GmbH to test the membrane in a real-life environment over a longer period so that we can continue to improve the stability and conductivity.” She believes the membrane could be ready for market in three to five years. “The demand is huge. But companies always prefer to have a finished product. We can’t offer them that. The only way we can develop good solutions that meet their needs is to work together with the industrial sector.”
As long as we are unable to replace PFAS completely, it is all the more important to capture them as effectively as possible and prevent them from spreading in the environment. To this end, Dr. Stefano Bruzzano from the Fraunhofer Institute for Environmental, Safety and Energy Technology UMSICHT worked with Cornelsen Umwelttechnologie GmbH several years ago to develop a cleaning technology that has since undergone continuous modification.
It is particularly efficient where there are high emission levels that are locally limited, such as when special foams are used to extinguish fires, or at landfills in which consumer goods containing PFAS slowly “bleed” and release the chemicals into the groundwater. The PerfluorAd® cleaning system can be used on site in a mobile container to clean the polluted water. For this purpose, the water is pumped into the system vessel where PerfluorAd® is added; this is a biodegradable liquid agent to which the PFAS bind, causing them to settle at the bottom.
The remaining water is channeled through activated carbon filters, in which the few PFAS that were not captured in the first cleaning step are retained. The severely contaminated sediment is later disposed of appropriately in an incinerator at temperatures well in excess of 1,000 degrees Celsius. Bruzzano: “The strength of our process lies in the fact that it combines different methods.” The activated carbon filters, which are already used in many water treatment plants, were not enough to provide a cleaning process that was both powerful and environmentally sound. At higher contaminations of more than 10 micrograms of PFAS per liter, they quickly became clogged. “It is important to analyze the polluted water in advance so that our process can be adapted to the PFAS and associated substances in the water, as well as the level of contamination,” emphasizes Bruzzano. This determines how much PerfluorAd® needs to be added, and whether any other process additives are needed, such as flocculants to separate the PFAS.
Dr. Georg Umlauf from Fraunhofer IGB is going one step further. Instead of simply removing PFAS from the water, he wants to destroy their structures to render them harmless by using plasma technology, just like his colleague Dr. Jakob Barz. As Umlauf explains: “We ignite air plasma between two electrodes and the polluted water flows in between them and down a column. Since the plasma is a very energy-rich medium, we can break apart the PFAS molecule chains so that we can keep shortening the carbon chains. However, this requires the water to be pumped around a circuit multiple times because one-off, brief contact with the plasma is not enough. The end goal is to mineralize the PFAS, which is when they have more or less dissolved. Then there is no need to use an energy-intensive combustion process.”
In the laboratory reactor, Umlauf successfully tested the plasma cleaning method with real samples from wastewater contaminated with PFAS. In the future, he would like to adapt the process to handle larger volumes. An improved analytical method should enable more accurate monitoring of the process and help to adjust the number of pump circuits required in individual cases. “However, there are still a few more challenges to overcome until we have a finished system that can clean tens of thousands of cubic meters of water per year. We are looking for partners from the recycling and industrial sectors to take part in the subsequent research.” This would spell the end for forever chemicals.
But time is running out. The European Commission wants to reach a decision on the PFAS ban by 2025. There will have to be transitional periods and exceptions. The substances are too important to achieving a rapid energy and mobility transition, as well as to state-of-the-art medical devices and the semiconductor industry. This is why alliance spokesperson Löbbecke underlines the urgency of the Fraunhofer research: “We can limit PFAS emissions. But we cannot completely dispense with PFAS yet.”
in nanograms per liter | nanograms per kilogram
Fraunhofer Institute for Chemical Technology ICT
