Researchers at Arizona State University have developed a new technique to destroy per- and polyfluoroalkyl substances (PFAS), commonly known as “forever chemicals.”
Forever chemicals are a family of synthetic substances that do not rot, rust, or break down in sunlight or soil, until now.
In a study, an international coalition designed a catalytic “hunter-killer” membrane to annihilate these toxic molecules.
“We all have PFAS in us. They stay in the environment. They move up the food chain, and so they’re a big legacy problem,” said Bruce Rittmann, director of the Biodesign Swette Center for Environmental Biotechnology.
The chemistry that hunts
Conventional water treatment methods like activated carbon filters, ion-exchange resins, and reverse osmosis extract toxic PFAS from drinking water. However, these methods fail to destroy the chemicals and simply trap the contaminants. Also, these processes leave behind concentrated brines and hazardous waste filters. Facilities ultimately bury or incinerate this waste, which delays the problem rather than solving it.
“PFAS are hard to break down, and normal processes that we use don’t work,” added Rittmann.
The reason behind this stubbornness is the carbon-fluorine bond. It is widely considered the single strongest bond in organic chemistry. Fluorine atoms shield the carbon backbone like interlocking armor plates. Microbes can’t digest it. Chemicals can’t pierce it.
“There’s really no place to get a start to break it down,” Rittmann explained.
To crack the uncrackable, Rittmann’s team worked alongside collaborators from Rice University, Tongji University, the National University of Singapore, and Nanjing University. And turned to a clever piece of molecular matchmaking.
Researchers constructed a hollow fiber membrane lined on the outside with palladium nanoparticles rather than attacking PFAS in open water.
The process works from the inside out. Pressurized hydrogen gas passes through the center of microscopic hollow fiber straws, diffusing outward until it meets a palladium catalyst. This catalyst splits paired hydrogen molecules into highly reactive individual hydrogen atoms. At the same time, PFAS molecules floating in the surrounding water attach to the palladium surface, bringing the reactive hydrogen and target pollutants together for destruction.
When the target and the activated hydrogen meet on the surface, the catalyst forces a violent chemical reaction. The hydrogen strips away the protective fluorine guard, stripping the molecule of its “forever” superpower and reducing it to harmless components.
More refinement of tech
During a continuous 58-day trial, the system treated water containing a cocktail of six different regulatory-priority PFAS compounds.
It removed over 90 percent of each compound and stripped away 83 percent of the total fluorine, the study reported.
High PFAS concentrations riddle groundwater near military bases, municipal landfills, airports, and wastewater treatment plants worldwide. These toxins accumulate in crops, livestock, and human tissue, where exposure has been linked to kidney cancer, thyroid disease, immune dysfunction, and developmental delays.
A universal mechanism to dismantle the full family of compounds could transform environmental remediation.
Several challenges need to be addressed before this technology can be deployed in municipal water systems. For instance, there’s a need to minimize the required amount of palladium to reduce costs. The precious metal trades at roughly $50,000 per kilogram.
Practical deployment will likely pair the reactor with existing filtration methods to concentrate contaminated water first. This allows the catalytic system to efficiently destroy the resulting waste stream.
The arrival of hunter-killer chemistry suggests this persistent toxic legacy might finally be coming to an end.