Turning sludge into semiconductors

Researchers from the Geological Survey of Denmark and Greenland have developed a technique to convert toxic arsenic waste into a critical material for semiconductors and essential green-transition technologies.

“Arsenic has been considered a toxic contaminant for decades. It's known as the King of Poisons and the Poison of Kings,” says Case van Genuchten, lead author on the recent publication. “It is very commonly found in groundwater and in gold and copper mine sites around the world.”

Groundwater can easily be treated to remove arsenic for drinking, but the leftover arsenic sludge remains toxic, as does the arsenic in mine tailings. Dealing with this waste has been a long-standing environmental and economic challenge, since there is no way to make arsenic non-toxic.

Van Genuchten and post-doc Kaifeng Wang, co-author of the study, saw a potential opportunity for valorizing arsenic waste by transforming it.

“The societal value of arsenic is changing almost in real time,” he says. “Arsenic is now used in a variety of different products that are needed to transition from fossil fuel economies to clean energy systems,” he says. The metalloid’s value is on the rise: A number of countries now include arsenic on their official list of critical minerals.

Van Genuchten and Wang have developed a chemical process to produce the metallic form of arsenic from groundwater treatment sludge, which can then be used in batteries, semiconductors, and other technologies. The technique forms a glassy, rather than crystalline, metallic arsenic.

To understand the unique features and important details about the glassy metal, van Genuchten turned to the Canadian Light Source at the University of Saskatchewan. “The Brockhouse beamline at the CLS was such a wonderful place for this work to happen. We needed a very specific technique to study the glassy material, and the CLS team facilitated our work really very quickly.”

Van Genuchten and his collaborators now want to test the technique at-scale. He hopes to bring the arsenic upcycling technique to actual water treatment labs and sees potential value for the method at sites around the world.

“There is so much of this waste that we haven’t been sure what to do with for a very long time, says van Genuchten. If you're able to take it out of the environment and create something that has value out of it, I think it is a really powerful environmental and societal idea.”

--

Wang, Kaifeng, and Case M. van Genuchten. "Commodifying a carcinogen: Critical raw materials from arsenic-laden groundwater." Science Advances 11, no. 42 (2025): eadz5816. DOI: 10.1126/sciadv.adz5816

Access images and B-roll related to this research

To arrange an interview with the researcher, contact:

Greg Basky
Communications Coordinator
Canadian Light Source
306-370-9446
greg.basky@lightsource.ca