Scientists have discovered a new way to break up “forever chemicals,” the notoriously persistent pollutants that contaminate our waterways and threaten public health, adding to a growing list of potential ways to deal with the long-lived compounds.
News of a simple, low-energy way to degrade some, but not all, chemicals forever came in August from researchers at Northwestern University who described how these tightly bound, long-chain synthetic chemicals — once thought impossible to degrade without a large amount of energy – “dissolved” under unexpectedly mild conditions.
Now, a team of scientists at the University of California (UC) Riverside has reported an alternative method to supercharge the destruction of PFAS chemicals in water.
It uses UV light and hydrogen gas to break down these harmful substances found in beverage consumables.
Long-lived PFASs (per and polyfluoroalkyl substances) were widely used for decades as anti-stick and waterproofing agents, where they found their way into everything from fire-fighting foam to cosmetics. They were later dubbed “forever chemicals” for the way they persist in the environment, have been found at alarmingly high levels in drinking water around the world, and have been linked to health problems such as liver cancer.
If this kind of research progress continues, they may eventually come off.
“The advantage of this technology is that it is very sustainable,” says Haizhou Liu, a chemical and environmental engineer at UC Riverside, and a senior researcher on the team that developed the new patent-pending process, which produces no unwanted byproducts.
Setting aside the regulatory levers that limit the risks of environmental contamination, there are two parts to solving the PFAS problem. The first involves removing the material from environmental resources, such as by filtering drinking water supplies (most often using carbon)—an easier task than cleaning up contaminated soil or groundwater.
The next, and more difficult, step is to dispose of the concentrated PFAS chemicals or destroy them without creating other harmful substances in the process. PFAS can be burned at high temperatures, for example, but this is expensive and incinerating products containing PFAS risks spreading them further.
This is where the new process comes in. It works with hydrogen gas bubbles (H2) through contaminated water to ionize water molecules (H2THE). This creates reactive species including hydrated electrons that then attack the strong bonds that hold the PFAS chemicals together.
Blasting the water with high-energy, short-wavelength UV also helps speed up these chemical reactions that were otherwise too slow to be useful in industrial settings.
So far the researchers have only tested their method on small volumes (500 milliliters or 17 fluid ounces) of tap water containing PFOA and PFOS, two types of forever chemicals.
But they have achieved rapid and almost complete degradation of the pollutants in these test batches using less electricity than previous attempts.
Dual hydrogen gas and UV light degraded 95 percent of the PFOA and PFOS chemicals within 45 minutes of treating the water, and up to 97 percent overall. However, the method still needs some optimization because even at barely detectable levels, PFAS chemicals are dangerous, according to health authorities.
This isn’t the first time researchers have tried to attach PFAS chemicals to break them down. Another group at Clarkson University in New York is working with the US Air Force to treat PFAS-contaminated water, using plasma reactors and argon gas to break apart the PFAS molecules.
Plasma gas is an ionized gas consisting of free roaming electrons and positive ions. In pilot tests of contaminated water discharged from monitoring wells at Air Force sites, treatment in plasma reactors for up to 50 minutes degraded between 36 and 99 percent of the PFAS chemicals, some faster than others.
With a problem this big, we need to consider all the options on the table. “The general consensus is that there is no one-size-fits-all solution for all chemicals that degrade forever,” chemical engineer Selma Mededovic Thagard of Clarkson University told the American Geophysical Union. Eos magazine.
Liu and his colleagues at UC Riverside believe they can also make their process more energy efficient by trying other low-energy light sources and tweaking their settings to enhance the diffusion of hydrogen gas through the water.
This will be important if the technology is to have a chance to scale up from laboratory test-tube experiments to real industrial applications, as it has been the main obstacle for other methods.
“We’re optimizing it by trying to make this technology versatile for a wide range of PFAS-contaminated source waters,” says Liu. “The technology has shown promising results in destroying PFAS in both drinking water and different types of industrial wastewater.”
The research was published in Journal of Hazardous Materials Letters.