This ‘chemical sponge’ sucks up the valuable minerals in polluted water

So-called rare earth elements aren’t actually rare. It’s just difficult to refine them into the purified forms that are needed for making things like electronics or clean energy tech. The standard processes are also toxic, which is one reason that the world has outsourced production to China.

Supra, a startup that spun out of the University of Texas at Austin, is taking a different approach that’s clean, low-cost, and makes it possible to capture some of the billions of dollars’ worth of critical minerals that are trapped in waste in the U.S.

The company’s technology uses supramolecular receptors, “a string of molecules built to grab specific molecules like a baseball glove,” says CEO Katie Durham. Jonathan Sessler, a chemistry professor at UT Austin, first designed receptors like these to target cancer cells. Then he realized that they could also be designed to target critical minerals.

“My original analogy was we were going to be making a chemical sponge,” Sessler says. “It would go in and capture these elements and we would pick it up and wring it out.”

In the final design, the nanometer-sized receptors are embedded into a polymer filled with tiny pores that increase the surface area for capturing metal ions. The material is 3D-printed into reusable cartridges.

At a mine or industrial site, tailings or wastewater can flow through a series of the cartridges, each targeting a specific element. The receptors bind minerals in alcohol and release them when they’re rinsed with water, using little energy and avoiding the use of toxic chemicals. The process, which the company says is 100 times more selective and faster than current rare earth refining, can also be used on electronic waste.

In lab tests on cobalt, the technology was able to capture 100% of the element, isolating it completely from other elements like lithium in a solution.

The tech can be customized for any element. As it comes to market, the startup is focused first on scandium and gallium, two valuable rare earth elements that currently are imported from China. “The U.S. is 100% import-dependent on them, and we really did not see a lot of other startups trying to address that,” says Durham. By collecting the trace amounts of scandium in industrial waste in the U.S., the company hopes it can change how the element is sourced.

The value varies wildly depending on purity—scandium, for example, can sell for $300 per kilogram at 99.9% purity, but $3,200 per kilogram at 99.99% purity. The purest form, at 99.9999%, sells for $500,000 per kilogram. (The startup is still optimizing its process, but is aiming for the highest purity.) The company plans to launch its first pilots with partners later this year.

Supra is one of a handful of startups working on ways to make rare earth production feasible in the U.S. Others include Phoenix Tailings, which works both with mined material and waste; and Cyclic Materials, which extracts and refines rare earths from end-of-life products.

Because of the demand for an American supply chain, Supra plans to focus first in the U.S. But the company eventually wants to make their products available globally—including in China, to help with the pollution challenge there. “The world has gotten lazy and let China pay the environmental cost,” says Sessler.