Most of the time, when we hear about PFAS, or “forever chemicals,” it’s most likely in a negative way. These substances are infamous for being nearly impossible to break down and tough on the environment. Usually, scientists focus on how to get rid of them. However, a team at Rice University decided to try something different. Instead of treating PFAS as a waste problem, they found a way to use them to extract lithium from saltwater.

Lithium is the main component of batteries that power our phones and electric cars. Currently, getting it involves a lot of mining or massive evaporation ponds, both of which take a toll on the land.

“Extracting lithium from brine can be less environmentally damaging than conventional mining, but it still faces challenges such as selectivity, cost and water use,” said Yi Cheng, a postdoctoral associate at Rice. “We saw an opportunity to use the fluorine locked in PFAS to recover the lithium in a fast, lower-impact process.”

A New Way to Get Lithium

The team started with activated carbon that had already been used to soak up PFAS from firefighting foam. Normally, once that carbon is full of chemicals, it just becomes more waste. However, the researchers realized that PFAS contains fluorine, which happens to be great at bonding with lithium.

They mixed this “spent” carbon with salty brine and hit it with a massive burst of heat, then cooled it down quickly. This shock breaks the chemical bonds in the PFAS. Then, the fluorine grabs onto the lithium in the brine to create a salt called lithium fluoride.

To separate the lithium from other minerals like calcium or magnesium, they heated the mixture again until the lithium turned into a gas. When they caught that gas, they ended up with a lithium source that was 99% pure.

Faster and Cleaner

When the team tested this recycled lithium in actual batteries, it worked just as well as the standard stuff. In fact, it even helped the batteries stay a bit more stable.

According to their analysis, this method uses less energy and water than traditional brine extraction. It’s also incredibly fast, taking only a few minutes to complete the process.

“By thinking about waste as a potentially useful compound, we were able to convert the problematic GAC-sorbed PFAS into a valuable metal that can be used in batteries, for example,” said James Tour, a professor of chemistry at Rice. “This promises significant environmental, economic and efficiency benefits.”