Forever Chemicals, Hemp, and Nanotech: An Unconventional Approach to PFAS Remediation
By Adara Taylor
PFAS compounds, commonly known as forever chemicals, have been found almost everywhere, from samples of human blood to snow and ice on the peak of Mount Everest. A threat to human health and the environment, the verdict is out on who will bear the burden of cleanup–and how.
Enter hemp, a modern hero of phytoremediation—the use of plants to remove contaminants from soil, water, and air. Pollutants, including some PFAS chemicals, cling to water molecules as they’re drawn up stem and leaf tissue, which can later be harvested and moved to a designated waste site. “[But] hemp doesn’t take up all PFAS compounds equally well,” says Haynes, “It tends to take up the smaller molecules—the ones that are happier being in water.”
To capture larger PFAS molecules, Haynes and her graduate students Cheng-Hsin Huang and Riley Lewis set out to construct synthetic nanoparticles that act as a sponge for stubborn, water-avoiding forever chemicals. A solution of nanoparticles sprinkled over contaminated soil, for example, would help mobilize reluctant forever chemicals for uptake by hemp tissue.
“My group has been building nanoparticles that can be used for various applications in plants. We’d also been building nanoparticles for a biomedical application where we were purposefully loading them up with perfluorinated molecules, so it seemed really interesting to ask whether we could essentially hide [PFAS] inside nanoparticles so that plants can take them up?”
The issue of PFAS contamination hits close to home in Minnesota where 3M, one of the earliest manufacturers of PFAS, recently settled for $850 million to help address the damage caused by PFAS leaching from waste sites into local wells and aquifers.
Partnering with Minnesota-based Ecolab, Haynes and her team are looking at two distinctly different nanomaterials carbon dots (CDs) and silica-based particles. Carbon dots are appealing because large quantities can be produced quickly while still being cheap and sustainable. Silica-based particles are another sustainable choice, and chemists have a better understanding of their structure. “Silica nanoparticles have the same chemical composition as sand or glass, but we make them really small, and they look like wiffle balls.” The challenge is to make these tiny wiffle ball-like particles appealing to PFAS so the particles are sucked into the empty cavity at the center. Even if these materials are effective, however, there’s still a need to address the breakdown of indestructible PFAS toxins being held at long-term waste facilities.
Haynes’ research of PFAS remediation began in partnership with collaborators at the Connecticut Agricultural Experiment Station (CAES) and members of the Aroostook band of the Micmac Nation in Maine. The Airforce returned an abandoned–and highly contaminated–Air Force Base to Micmac jurisdiction after firefighting foam drenched the soil with dangerous levels of forever chemicals.
In 2019, the Aroostook band began planting industrial hemp in an attempt to restore the parcel of land where concentrations of forever chemicals reached levels deemed unsafe by federal standards. When collaborating researchers saw a significant (if modest) decrease in soil concentrations of forever chemicals where hemp had been planted, the effort sparked interest and collaborations, like the partnership with Haynes, to find accessible, industry-friendly ways of remediating environments polluted by forever chemicals.
Haynes describes it as a significant part of the remediation process. “Even if this proposal works perfectly, it doesn’t break down the PFAS. It pretty much just says ‘Can we at least know where it is? Can we use a tool to concentrate [PFAS molecules] in one place so that we know where they are so we can do whatever’s next?’ We’re working on just the concentration part of the puzzle, hoping to add to the bigger overall solution.”
Efforts like those made by Haynes, CAES, and the Micmac Nation may not mark the finish line in the global effort to remediate PFAS chemicals, but they may open a path forward for sustainable PFAS removal in Minnesota and beyond. Ecolab, a global player in the water treatment and purification industry, is looking at commercial applications for the technology.
While there may not be a single solution to the global issue of PFAS contamination, nanoparticles could become part of the toolkit for removing forever chemicals from contaminated soil—part of a suite of technologies addressing the problem. “I’m a big believer that there’s not going to be one big winner,” says Haynes.”It’s going to be a conglomeration of chipping away from [many] angles.”