Perfluoroalkyl and polyfluoroalkyl substances, known as PFAS, are often called “forever chemicals” because they break down very slowly in the environment.
These chemicals have been widely used in products such as firefighting foams, nonstick coatings, and water-resistant materials.
Over time, they have become a major environmental concern because they can accumulate in soil, water, and even in the human body.
Most scientific research today focuses on removing PFAS from the environment and safely disposing of them.
However, researchers at Rice University have taken a very different approach. Instead of simply trying to destroy PFAS waste, they have developed a method that uses it to extract lithium, a valuable metal used in batteries.
Their work was recently published in the journal Nature Water.
Lithium is a key material in lithium-ion batteries, which power smartphones, laptops, electric vehicles, and many renewable energy storage systems.
Traditionally, lithium is mined from rock or extracted from salty underground water known as brine.
While extracting lithium from brine can be less damaging than mining, it still faces challenges. These include high costs, large water use, and difficulty separating lithium from other minerals in the brine.
The research team, led by Rice University scientist James Tour and postdoctoral researcher Yi Cheng, saw an opportunity to solve two problems at once: dealing with PFAS waste and improving lithium extraction.
Their process begins with firefighting foam that contains PFAS chemicals. When this foam is cleaned from the environment, it is often treated with granular activated carbon, or GAC. This material absorbs PFAS and traps it inside.
However, once the carbon becomes saturated with PFAS, it creates another waste problem because the contaminated carbon must be disposed of.
Instead of throwing away this PFAS-contaminated carbon, the researchers used it as a starting material. They mixed the PFAS-laden carbon with a highly salty brine solution that contains lithium along with other minerals.
Inside PFAS molecules is fluorine, an element that can form strong chemical bonds with lithium. The researchers wanted to release this fluorine from the PFAS and allow it to combine with lithium in the brine to form lithium fluoride, a useful lithium compound.
To make this happen, the team used a technique called electrothermal heating. This process quickly heats the mixture to extremely high temperatures—more than 1,000 degrees Celsius—and then rapidly cools it. These intense conditions break apart the PFAS molecules, freeing the fluorine atoms so they can react with lithium and other metals in the brine.
After the reaction, the mixture contained several fluoride salts, including lithium fluoride, calcium fluoride, and magnesium fluoride. The researchers then used heat again to separate the lithium fluoride from the other compounds. Because lithium fluoride boils at a lower temperature than the other salts, it could be distilled and collected.
Using this method, the team recovered about 82 percent of the available lithium fluoride with 99 percent purity. They also tested the recovered lithium in lithium-ion battery electrolytes and found that it worked well, improving stability and performance.
Environmental analysis suggests the new process may use less water and energy than existing lithium-extraction methods. It may also produce lower greenhouse gas emissions and operate faster, taking only minutes to complete.
The researchers say their work shows that waste materials like PFAS could be transformed into useful resources instead of simply being treated as pollutants.
