New ultrasonic technique can destroy toxic “forever chemicals”

If my wife and I ever split, it’ll be over scrambled eggs. Or, more precisely, the pots involved in scrambling eggs. My wife has a preferred pot (something she insists is quite normal), and she cooks everything in it – pasta, sauces, and dastardly eggs. The problem is that her preferred pot is not a non-stick pot. Quite the opposite, actually. This pot seems uniquely designed to cling interminably to any residue whatsoever. To save my marriage, I will need a shipment of per- and polyfluoroalkyl substances (PFAS).

PFAS are a group of chemicals used for their incredible ability to repel oil and water. They’re unsung heroes in much of non-stick cookware, water-repellent clothing, and firefighting foams. Yet, their strength is also their curse. PFAS don’t break down easily in the environment, leading to concerns about their impact on health and ecosystems. They were designed to be indestructible.

PFAS pose a problem. We use them in a lot of our day-to-day lives, yet they can be one of the most damaging and resilient chemicals we’ve ever made. But they may have an Achille’s heel.

The PFAS problem

For years, scientists and environmentalists have grappled with the PFAS conundrum. These compounds have been called “forever chemicals” because of their persistent nature. They collect in the environment, like in rivers and bodies of water, but can also build up the food chain in human and animal tissues, leading to potential adverse health effects. As of August, 3,186 locations across the United States are known to be contaminated with PFAS.

Regulators and researchers worldwide have been trying, and funding, various methods to safely and effectively break down PFAS for a while now. Traditional techniques have proven fruitless, either being too inefficient or creating more harmful byproducts. This challenge has led researchers at The Ohio State University to explore a new approach: ultrasonic defluorination.

This technique promises to open a new frontier in tackling fluorotelomer sulfonates, a subset of PFAS.

Ultrasonic frontiers

The study by Fagan et al. dives into — deep breath — the kinetics and mechanisms of ultrasonic defluorination of fluorotelomer sulfonates.

In slightly less technical terms, they used ultrasonic irradiation to break the strong bonds holding these compounds together. This means using low-frequency sound waves, which create a high-pressure environment. This, in turn, creates intensely hot points, with temperatures up to 10,000 kelvin, which break apart the stable (and tightly clinging) carbon-fluorine bonds in PFAS.

The whole process essentially shakes the molecules really hard until they break apart, not unlike using a jackhammer, but at a molecular level.

The team meticulously analyzed how different conditions, like the frequency and power of ultrasonication, affect the degradation process. They closely measured the breakdown products because they didn’t want the compounds to break into some other, possibly worse, substance. Finally, they weighed up the efficiency of this method in reducing the environmental persistence of these stubborn compounds against other options.

They found it to be successful, safe, and effective.

Not-so-forever chemicals

This study is good news for efforts to tackle what is potentially a highly toxic and hugely damaging chemical. It shows one way to solve a problem we’ve been grappling with for a long time.

However, there are still some hurdles to jump, namely how to implement such a process. The research team has shown that ultrasonic defluorination can be effective in degrading and disarming PFAS on a small level. This means it could be useful in smaller, concentrated, or domestic settings, for example, in water filtration devices. But we don’t yet know how easily or cost-effectively this method could be scaled up for widespread environmental cleanup. Nor do we know if it works as effectively in diverse environmental conditions beyond the laboratory or a few test sites.

That all said, this study does open new doors for dealing with “forever chemicals.” The end goal of turning these environmental pollutants into harmless substances is far from over, but with innovative approaches like ultrasonic defluorination, we inch closer every day.