WHQR | By Kelly Kenoyer
Published February 17, 2022 at 5:09 PM EST
Scientists at the NC Policy Collaboratory have developed a new PFAS filtering technology that’s particularly good at removing GenX from drinking water.
There's a new sheriff in town to fight the emerging contaminants in the Cape Fear River.
The newly developed technology — known as 'ionic fluorogel' — is years in the making, and aims to unseat existing technologies that are less effective.
Granular Activated Carbon, or GAC, is the filter of choice for many water treatment plants, as it covers a wide spectrum of contaminants. But Frank Leibfarth, a chemist and researcher at UNC Chapel Hill, said it’s not perfect.
“When you've put an initial amount of water into granular activated carbon, it absorbs organic matter and PFAS," he explained. "But as it starts to become saturated and there's more organic matter there, it will actually kick off some PFAS from binding sites and kind of put it back into the water.”
Under lab conditions, Leibfarth found that the carbon would need to be changed out every four or five months — an expensive venture, and a major problem when it comes to disposing of the contaminated carbon.
So Leibfarth sought an alternate filtration method formulated just for PFAS (per- and poly- fluoroalkyl substances). With the support of the North Carolina Policy Collaboratory, he and his team have developed what’s known as a fluorinated ion exchange resin. The ionic fluorogel looks like tiny white dots, each less than a millimeter in size, and works for at least 13 or 14 months. That's as long as they tested it for, and it may last even longer, he said.
It’s also reusable.
“We've actually found we can wash the PFAS off those materials. So we can create a concentrated brine of PFAS that we can then destroy," Leibfarth said. "And then we can re-use the resin multiple times.”
How It Works
The gel uses two different strategies to attract PFAS: electrostatics, and the Fluorous Interaction.
Leibfarth says electrostatics are a common method for capturing materials, and the more easily understood of the two interactions. “Most PFAS are negatively charged. So we put positive charge charges permanently in this resin to make that electrostatic interaction and to absorb the PFAS.”
The other strategy is unique to the gel: it’s called a Fluorous interaction. The material actually uses a component of the PFAS: Fluorine, to attract the PFAS to the filter.
The science is complicated but, basically, fluorine is attracted to other fluorine, but isn't attracted to water or oil, Leibfarth says. "We want to take advantage of that fact that Fluorine is unique, and likes itself, but doesn't like water and doesn't like oil. So we designed this resin to have a fluorinated matrix.”
He says those two attributes work together magnificently, any synergistically. “You get a much larger effect than either individually.”
Scaling Up Testing
The ionic fluorogel is effective in a lab, but needs further testing before it can get implemented commercially. That will take funding – but Jeffery Dennis Warren, the executive director of the NC Policy Collaboratory, says the team has received a lot of support from the state legislature.
“The November budget provided $10 million for this specific program,” he said, which will be used for three pilot projects.
One of those pilots will be at a water treatment plant, and the Cape Fear Public Utility Authority is scheduled for talks with the researchers next week.
Another will be at a wastewater treatment plant, as a lot of effluent running into the Haw River is full of PFAS.
The third deployment calls for a water well, and Warren said the team is looking at an offline well in Wrightsville beach for that pilot.
Three years ago, testing revealed at least one of the town’s wells had high levels of PFAS – believed to have ‘migrated’ from CFPUA’s aquifer, which at one point was also filled with PFAS-contaminated water. The pilot aims to change that.
Legislators are very excited about the prospect of this technology, including Sen. Michael Lee (R- New Hanover County). He strongly supported this funding in the budget last year, along with members in both parties and in both bodies of the legislature.
Lee even suggested CFPUA could replace its GAC filter, which is currently under construction, with a more effective fluorogel filter down the line: “They can retrofit it for this ionic fluorogel media that again pulled out 100% [of the PFAS] in the lab, they're not sure if it will, but at least it'll do a lot better than than the GAC.”
The intellectual property rights for the technology will stay with the UNC Chapel Hill, so any profits that come from it can go towards future PFAS research.
Leibfarth said the pilot projects will likely be up and running in 18 months, though with necessary safety testing, it’s unclear when the gel might be used at a larger scale.