Think Out Loud

University of Washington researchers find new way to destroy forever chemicals

By Rolando Hernandez (OPB)
Sept. 28, 2022 4:36 p.m. Updated: Sept. 28, 2022 7:50 p.m.

Broadcast: Wednesday, Sept. 28

Forever chemicals are molecules that are present in our daily lives. They’re found in food packaging and household cleaning supplies. What concerns many scientists is their ability to persist in soil and water because they can’t break down naturally. Researchers at the University of Washington have created a reactor that can destroy the most common type of forever chemicals: PFOA and PFOS. Igor Novosselov is a research associate professor in mechanical engineering at UW. He joins us to share how this reactor works and the implications it can have for the future.


Note: The following transcript was created by a computer and edited by a volunteer.

Dave Miller: This is Think Out Loud on OPB. I’m Dave Miller. We start today with new research on chemicals known a PFOAS; they’re found in countless products they are famous for not breaking down. That’s why they’re known as forever chemicals. They’re also very dangerous to human health. As the EPA has noted, they can lead to cancer and cardiovascular and neurological and developmental issues among other problems. And they could soon be listed by the federal government as hazardous substances with the so-called superfund designation. So it is welcome news that researchers at the University of Washington have found a new way to neutralize these chemicals. Igor Novosselov is a Research Associate Professor in Mechanical Engineering. He joins us to talk about this work. Welcome to the show.

Igor Novosselov: Hello there.

Miller: What kinds of products are these chemicals used in or found in?

Novosselov: There are two primary issues with these chemicals. First of all, the highest concentration of those chemicals can be found in the sites where we have firefighting foam training pits. So any kind of liquid fires need to be put out with this foam. The foam has been used in the shipyards, on the Air Force Bases. And this is the number one priority for us, to understand where this firefighting foam goes. Number two is the, you know, your standard things that were made by Dupont, or 3-M, like Teflon and Scotchgard. So those are also there. And those can be found in the landfills. And the… you know the water from the landfills called leachate, coming out with a very high concentrations of those chemicals being in there.

Miller: Landfills, but I also imagine our closets and our kitchen cupboards and on our stoves.

Novosselov: Absolutely. Dupont has this miracle surface called the Teflon and we’ve been using this for the last 50 years. It’s wonderful to cook on, but it might not be very healthy because at very high temperatures, these compounds can break down.

Miller: Are there any ways to destroy these chemicals right now? I mean, before we get to what you and your team have been working on? I mean, what was, what was the method in the past?

Novosselov: Basically they would barrel them up and store them and when the barrels leak, then you have a problem. If you have very high concentrations, people were trying to burn them. But you know, if you use the material to be a forever chemical that was designed to extinguish fires, it’s very hard to burn those things. So the number one thing so far, it’s been incineration and incineration has been used in many countries and in many states, in the United States, but now it becomes a dirty word because nobody wants to have the incinerator in their backyard.

Miller: In addition to just the existing problem with incineration, Is it also the case that when you burn these chemicals, you create other ones?

Novosselov: Those are, as I mentioned, are very tough chemicals to break down. So the primary use of firefighting foam was C-8 compounds, it means that eight carbons strung together and terminated by fluorine atoms. And that’s what’s called the fluorocarbon. And these molecules are notoriously hard to break, especially sulfonated compounds, known as PFOS [polyfluoroalkyl substances] and we’ll talk about that maybe later. But yes,

when you’re trying to burn those, the molecules are so tough, they don’t burn themselves and they create aerosols and you can admit those things in aerosol phase, (inaudible). So you’re ending up with volatile organic fluorines or aerosol containing fluorine compounds.

Miller: So you have been looking at another way to handle these to destroy or neutralize these chemicals using what you call a reactor. Can you describe physically what this is?

Novosselov: So our reactor is a bench-top left scale reactor, it’s not very big and that reactor operates in a supercritical water condition. Supercritical water is something that is hot and high pressure. So if you take the water and boil it, it starts to boil at 100°C, you can raise the temperature of boiling to 374 [degrees], if you crank pressure high enough. At the pressures of 220 atmospheres, water boils at 374°C. However, if you exceed that temperature, you’ll go into something called the supercritical water region, where water behaves not like water and not like gas. It’s something in between. It’s like very dense gas, but it’s also ionized. So it’s very, very active, chemically aggressive, it’s very corrosive and specifically very, very active for organic compounds that we’re talking about carbon-fluorine compounds.


Miller: So in a sense, what you have is a very powerful pressure cooker?

Novosselov: You can explain it like that. The pressure cooker has issues because, pressure cooker is something we call the batch reactor. You put things in there and you let it boil or let it come to some kind of equilibrium. But you need to make sure that you have a throughput through the reactor. It means you need to continuously go through the reactor and continuously oxidize those chemicals. So if you have a pressure cooker, it takes a long time for those molecules to heat up, maybe an hour, maybe two hours before you reach those temperatures. But we operate this reactor in a continuous flow regime. It means we already have something hot and we spray those chemicals in kind of like a diesel engine. You know, you spray your fuel into already hot and high pressure environment to make it burn, right? So that’s kind of kind of what we do.

Miller: What are the by-products? So let’s say that you have some water and then you put some of these forever chemicals in your reactor and you crank it up and it gets super hot, super pressurized, Not… no longer exactly a liquid or a gas, what exactly happens to the forever chemicals,

Novosselov: It depends, and it depends on where you operate. So if you operate right around this transition point where you have a 300, maybe 400°C, you’re gonna have incomplete product of oxidation. So you’re gonna have a lot of intermediate species. They include gas species that include liquid species. And you’re breaking maybe breaking the parent compound, but you still have a lot of other compounds that are washing out of the reactor. Once you raise the temperature to 600°C, very little comes out. And what you have is a complete product of oxidation which is going to be carbon dioxide, water molecule, and the fluorine molecules go to inorganic fluoride. So something you can find in a toothpaste, chlorinated water in a, you know, in a in our tap or sodium fluoride in the toothpaste. So those all contain fluoride. Fluoride is not really being regulated, only the very high concentrations. It can be harmful for humans, but at the level that we produce sodium fluoride, it’s not very dangerous.

Miller: So let’s talk about applications here because you know that this is a tabletop-sized contraption. How big could it get? How much could it scale?

Novoselov: You can scale up significantly. In some instances scaling up is actually a little bit easier than making it smaller. It’s something to do with surface to volume ratio. If you have small devices, they have typically, large surfaces and very little volume. So you have a lot of heat loss from the reactor. But if you are bigger then you don’t have this issue. So it’s easy to sustain this oxidative regime. The issue of course how to make it big and how to make it safe and that’s where we need to scratch our heads and us being engineers we probably can figure it out.

Miller: So what is the dream here? Let’s say that there is a maker of some kind of firefighting foam and they’ve got barrels of stuff that, because of let’s say a superfund designation, that they can’t just throw away somewhere. What in the future might they do?

Novosselov: You can have a reactor on site that basically processing this ‘A Triple F,’ Firefighting foam. And there’s a lot of it there…every shipyard, every airport has this because it’s used to extinguish liquid fires. You have fuel on fire. What do you do? You cannot throw water on it. So that’s what’s been used. So there’s a lot of that and they, you know, the army decided that DOD, Department of Defense decided that by 2024 they do not want to use this foam and they want to get rid of all the foam and everything that ever touched that foam. So that’s a pretty aggressive timescale. We really need to push it forward. They really got to figure out how to make those reactors and how to operate them properly. So that’s one of the applications, is basically destruction of the legacy, ‘A Triple F.’

Miller: What other potential applications do you see?

Novosselov: There’s a lot of sites in the United States and around the world where groundwater is contaminated. Looking at the map of Oregon, there’s a number of, you know, air force bases and number of airports. And I was just clicking around here and I found that, you know, Klamath Falls has a very high level of PFAS in the groundwater. So I’m not going to be surprised if I see that site will be designated ‘Superfund.’ It’s probably one of the highest concentration of groundwater, PFAS in the groundwater, in the Pacific Northwest. Only probably rivals with the Spokane Air Force Base, with the Fairchild Air Force Base. So, those two hot spots in the Pacific Northwest is really a concern.

Miller: Could what you’re talking about- and we just have two minutes left- but, could a reactor of the kind you’re describing a larger one actually be used to clean up an entire groundwater system, a whole aquifer?

Novosselov: No, it cannot. It’s just too much. So, it had to be in a combination with other things. We see our reactor at the end of life for these PFAS compounds. So, the things we envision is, there’s going to be some pre-concentration technology; it can be iron membranes or it can be foam concentrate but they can concentrate that PFAS from relatively large volume to relatively small volume, that can be treated by the reactor.

Miller: First gather this stuff and then put in the reactor to eradicate it. Just briefly, are there efforts underway to reduce the creation of these chemicals in the first place?

Novosselov: There is, there is a large, large effort on…by the federal government to actually come out with alternative formulation when we do not have the fluoride, chlorine containing firefighting foams. But you know, it’s just so prolific. The use of those is so prolific and such beautiful material – is very tough. You know, the water sheds from it, so it’s a good material. So it’s gonna be hard for society to kind of turn away from your teflon pans to the cast iron pans, not everybody gonna do it. So it’s going to be there for a while I think.

Miller: Igor Novosselov, thanks very much.

Novosselov: Thank you.

Miller: Igor Novosselov is a Research Associate Professor in Mechanical Engineering at the Univers

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