Arsenic-Rich Sludge from Groundwater Treatment and Mine Tailings Waste Can Be Chemically Converted to Amorphous Metallic Arsenic for Use as a Semiconductor Metal

      Scientists at the Geological Survey of Denmark and Greenland have developed a chemical process that converts toxic arsenic waste into metallic arsenic for semiconductors, batteries, and other clean energy technologies. Arsenic waste exists in the residues left after groundwater treatment, which is one source of the waste. Another is mine tailings, mainly from gold and copper mines. I wrote about strong correlations between arsenic in groundwater and cancer rates a few months ago. The region around the Netherlands is well-known to have groundwater with high arsenic content. Thus, dealing with this waste in a way that makes it both inert and useful is a desirable outcome. This includes decreasing environmental risks.

“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.

     The U.S. and the E.U. now consider arsenic to be a critical mineral. Thus, recovering it from waste can have value, as well as reduce alternative disposal and mitigation costs and decrease environmental impacts. There is a significant amount of arsenic waste around the world, and those locations would benefit from its removal from the environment. 

     The arsenic is transformed in a chemical process, “via a two-stage process of alkali extraction and selective reduction.” The final product is what is known as a glassy metal instead of a crystalline metal. Glassy metals can have desirable electrical and mechanical properties. The resulting material was studied at the Canadian Light Source at the University of Saskatchewan. They used specialized tools to examine the atomic structure of the glassy arsenic, also known as amorphous metallic arsenic. The analysis confirmed that the glassy arsenic material meets industrial requirements. Amorphous arsenic is stable and easier to store, handle, and transport than crystalline arsenic, which makes it a desirable product. It is also chemically easier to combine it with “other compounds or thin films, which could make it a better feedstock for producing electronic or optical materials.”

     A diagram of the two-stage process of sludge production and valorization is shown below.

     An article in Chemical & Engineering News explains the process of recovering arsenic from groundwater and turning it into glassy arsenic. The research was reported in the journal Scientific Advances in October 2025.

“Most water treatment plants remove arsenic from groundwater by adding iron ions that oxidize in the water and turn to rust. These rust particles bind to arsenic and eventually settle into a dense, reddish sludge at the bottom of treatment tanks. This waste is rich in arsenic and phosphorus, which are chemically bound to the surfaces of the rust particles.”

“Kaifeng Wang and Case van Genuchten at the Geological Survey of Denmark and Greenland recover the arsenic from this sludge by washing it with a concentrated alkaline solution. This process breaks the chemical bonds between arsenic, phosphate, and the iron oxides, releasing the arsenic and phosphate into the liquid. When the mixture is heated and treated with thiourea dioxide, the dissolved arsenic compounds are reduced to elemental arsenic, which separates as fine metallic particles. The phosphate remains dissolved and can be recovered separately by treatment with calcium.”

     Recovering phosphate is another bonus of the process since it, too, is a valuable commodity. This aids the economics of the process.

     The next step is to test the process at scale. Another challenge to overcome will be recycling the reagents. Since water treatment plants are a major source of arsenic from waste, they can be converted, in a real sense, to amorphous arsenic refineries.

    

References:

 

New chemical process turns toxic arsenic sludge into semiconductor material. Aamir Khollam. Interesting Engineering. January 15, 2026. New chemical process turns toxic arsenic sludge into semiconductor material    

Recovering arsenic from wastewater sludge: A 2-step process transforms toxic waste to high-purity elemental arsenic. Ananya Palivela. American Chemical Society. Chemical & Engineering News, October 17, 2025. Recovering arsenic from wastewater sludge

Commodifying a carcinogen: Critical raw materials from arsenic-laden groundwater. Kaifeng Wang and Case M. van Genuchten. Science Advances. 15 Oct 2025. Vol 11, Issue 42. Commodifying a carcinogen: Critical raw materials from arsenic-laden groundwater | Science Advances