The many kinds of PFAS are called “forever chemicals” because of the difficulty of making them harmless. But there’s been a good deal of progress recently.
Why it’s necessary to solve this problem
Here’s why that matters.
Per- and polyfluoroalkyl substances (PFAS) are manufactured chemicals used in firefighting foam, breathable outerwear, fast-food packaging and other products. Now, there is increasing concern about PFAS as a health risk.
Two big problems about PFAS:
- They’re often present in highly dilute form, such as in groundwater, landfill leachate and industrial wastewater
- The molecules are difficult to break, because they contain a carbon-fluorine bond, one of the strongest known to science
This post looks at ways to concentrate and destroy PFAS.
PFAS concentration technologies
Three ways to concentrate PFAS-laden groundwater are:
Foam fractionation: Foam fractionation involves releasing bubbles of air from below the water to be treated. As the bubbles rise, the surface-active molecules, including PFAS, attach themselves to the gas-liquid interface of the bubbles, to form a foam on the liquid’s surface. This foam can then be skimmed off.
Ion exchange: This method uses ion exchange resins made of highly porous, polymeric material. The internal porous surfaces of the resins contain highly polar (charged) bound chemical groups that will attract molecules having opposite charge. PFAS molecules, holding a negative charge, are attracted to anionic exchange (positively charged) resins, from which they can be removed.
Reverse osmosis: This involves using pumps to push the liquid up against a semi-permeable membrane. Water molecules are small enough to slip through the membrane, while larger contaminant particles and molecules – including PFAS – stay on the “concentrate” side.
PFAS destruction technologies
Here are some of the methods for PFAS destruction.
Incineration: One destruction technique that has been found wanting is incineration – not all PFAS molecules get destroyed, and harmful by-product molecules are formed.
Plasma: This technology destroys PFAS molecules by harnessing the fourth state of matter, plasma. Within the plasma vortex reactor, a voltage gradient is applied between two electrodes. This creates an electric field that strips electrons from the inflowing gas molecules, creating charged ions and releasing a plasma discharge. The ions are highly chemically reactive, and can break down PFAS molecules. This produces harmless byproducts like fluoride, sulfate, carbon dioxide and water. Our company, Onvector LLC, uses plasma vortex technology.
Supercritical water oxidation (SCWO, pronounced “SKWOH”): Water above a given temperature and pressure is considered “supercritical,” where chemical oxidation processes are accelerated. SCWO might prove a practical way to destroy PFAS by breaking the strong carbon-fluorine bonds. It’s been shown to do the job – but the hard work will be showing that it can do this reliably and cost-effectively.
Electrochemical oxidation: This is a water treatment technology that uses electrical currents passed through a solution, such as PFAS-containing water, to oxidize pollutants. Advantages of EC include: low energy costs, operation at ambient conditions, ability to be in a mobile unit, and no requirement for chemical oxidants as additives. But it’s hard to scale up, and has the potential to generate toxic by-products.
Next step: reach out to us for an exploratory conversation
If you have a PFAS problem you want to solve, please reach out and we’ll have a conversation around whether there’s a fit between what you need and what we can offer. We’re also interested in skilled professionals who might want to join our team.