Scientists have discovered a new way to destroy “timeless chemicals”, known pollutants in our waterways and threats to public health, adding to the list of possible approaches to combat them.
News of a simple, low-energy method for breaking down some, but not all, chemicals came in August from researchers at Northwestern University, who described how these long-chain, highly bound synthetic chemicals, once thought impossible to break down without high energy pots, “flies out” in unexpectedly mild conditions.
Now, a team of scientists at the University of California (UC) Riverside have reported an alternative pressurization method to destroy PFAS chemicals in water.
It uses ultraviolet light and hydrogen gas to break down harmful substances found in drinking water.
Long-lasting PFAS (per- and polyfluoroalkyl materials) have been widely used for decades as non-stick and waterproof agents, finding applications in everything from firefighting foam to cosmetics. Dubbed the “timeless chemicals” because they persist in the environment, they have been found in alarmingly high concentrations in drinking water around the world and have been linked to health problems such as liver cancer.
“The advantage of this technology is that it is very robust,” says Haizhou Liu, a chemical and environmental engineer at the University of California, Riverside, and a senior scientist with the group that developed a new, patented process that does not produce unwanted by-products. Leaving aside control levers that reduce the risk of environmental pollution, the solution to the PFAS problem has two parts. The first involves removing materials from natural resources, such as filtering drinking water (often using carbon), an easier task than cleaning up contaminated soil or groundwater. The next and more difficult step is to dispose or destroy the concentrated PFAS chemicals without creating any other harmful substances in the process. For example, PFAS can be burned at high temperatures, but this is expensive, and combustion products containing PFAS can spread it further.
And then a new process begins. They work by passing hydrogen gas (H2) through contaminated water to ionize water molecules (H2O). This generates reactive particles, including hydrated electrons, which then attack the strong bonds that hold the PFAS chemicals together.
Treating water with high-energy, short-wavelength ultraviolet rays also helps speed up these chemical reactions, which used to be too slow to be used in industrial settings.
So far, the researchers have only tested their method on a small amount (500 milliliters, or 17 fl oz) of tap water with PFOA and PFOS, two persistent chemicals.
But they achieved rapid and near-complete degradation of contaminants in these test batches using less electricity than previous attempts.
The double blast of hydrogen gas and UV radiation decomposed 95% of the PFOA and PFOS chemicals within 45 minutes of water treatment and up to 97% overall. But the method still needs some fine-tuning because, according to health authorities, even at barely detectable levels, PFAS chemicals are dangerous.
And this isn’t the first time researchers have tried to use PFAS chemicals to destroy them. Another team from Clarkson University in New York is working with the US Air Force to treat water contaminated with perfluorinated sulfonates using plasma reactors and argon gas to separate PFAS molecules. Plasma gas is an ionizer consisting of free electrons and positive ions. In experimental testing of contaminated water treated from manholes at Air Force facilities, treatment in plasma reactors for up to 50 minutes decomposed 36 to 99% of the PFAS chemicals, some faster than others.
With a problem of this magnitude, we need to consider all possible options. “The general consensus is that there is no one-size-fits-all solution” for an eternal chemical solution, chemical engineer Selma Medovich Thagard of Clarkson University told EOS of the American Geophysical Union.
UC Riverside researchers believe they can also make their process more energy efficient by testing other low-energy light sources and modifying their setup to improve hydrogen gas diffusion through water.
This will be important if the technology has a chance to scale from laboratory experiments in test tubes to real industrial applications, where it has been a major hurdle for other methods.
Research published in the journal Magazine of Hazardous Materials Letters.
Source: Science Alert
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