Earlier I was sent a wonderful article by the BBC about a new breakthrough in degrading “forever chemicals” known as PFAS. PFAS aka “perfluoroalkyl substances” are common chemicals used to make all sorts of houseware from paints to pans to wrappers. They are highly resistant to liquids which is why they’re so often used, but that itself makes them difficult to degrade. Because they are difficult to degrade, they stick around and have been linked to some harmful health effects if they are present at very high levels. This is why the new breakthrough is so important, the ability to degrade these chemicals before they build up to harmful levels would be very useful.

After reading the BBC article I went to the paper itself to understand the science behind the breakthrough. Now here’s where I have questions, because I am not an expert here I’d love if some actual science experts could help me understand this. To start with, PFAS is basically a long string of carbon atoms ending in a carboxylic acid, and attached to each carbon atom is a bunch of fluorine atoms. Prior research demonstrated that the carboxylic acid can be popped off using high temperature (120 degrees C) and a polar, aprotic solvent (water is protic, DMSO is aprotic, aprotic means that is can’t donate hydrogen bonds, which water does do easily). Once the carboxylic acid is popped off by this high temperature and specific solvent, then all the fluorine ions are readily removed by the addition of NaOH. In the main body of the research this step was simultaneous to the popping off of the carboxylic acid (aka at 120 degrees C), but later on the paper said that removing the fluorines could also happen at lower temperatures.

Now this is all very cool but one of my questions is: what happens to all those fluorines? And especially what will happen if we try to industrialize this process to degrade PFAS on a large scale? It appears that the fluorines remain as F- ions in the solution, but from my understanding if even a small amount of water gets into the solution, they will readily turn into HF, a very dangerous acid. If this process is scaled up, it seems conceivable that the concentration of PFAS will be increased in the reaction vessel to more efficiently use space and heat for degradation, meaning the concentration of fluorine following degradation will also be increased, meaning that the possibility for high concentrations of HF will also increase. So basically: is this process ready for prime time, or do we need to add another step to safely remove the F- ions? Fluorine as an atom is very hard to move around, requiring special permits and special containers, so I can’t imagine you can just package and ship it to some plant for re-use in new PFAS production. So what’s the next step? What’s a good way to remove or neutralize the fluorine so it can either be safely disposed of or sold for re-use? I’d love if any scientists could help me understand this.