For decades, treatment plants have been removing arsenic from drinking water without having a proper place to dispose of it afterwards, often leading to environmental pollution and health risks. That all could change following a recent breakthrough by a young scientist based in Denmark.
Researcher Case van Genuchten says despite being studied extensively, a solution regarding how to manage and store arsenic waste safely has yet to be established.
“In the best care scenario, this material has been put in a landfill. In the worst-case scenario, in areas like India…this waste is just kind of accumulated and stockpiled,” he explains. “This waste, which now has concentrated arsenic levels, it just cast aside and put back into the environment.”
Until now, that is.
Over the last several years, van Genuchten has used his vast understanding of chemistry to take the toxic arsenic sludge that has been removed from groundwater and convert it into metallic arsenic, which was recently classified as a critical raw material. Using sodium hydroxide and a non-toxic chemical called TDO, van Genuchten was able to create this highly sought-after substance, giving new life to a toxic paste that would have otherwise sat in a landfill.
“Something really interesting globally is happening with arsenic now. In many regions of the world, arsenic is now classified as a critical raw material, and the reason why is because it’s used to produce products that are needed for the transition from fossil fuels to clean energy systems.”
That list includes semiconductors, batteries, and alloys.
“Even five years ago, there wasn’t this changing societal perspective of what arsenic could be. It’s always been viewed as this carcinogen.”
He adds that the Canadian Light Source at the University of Saskatchewan was used to look closely at the properties of their metalloid.
“The Canadian Light Source is one of the only places in the world that has the kind of capabilities to probe the structure of amorphous material.”
He says the CLS beamline helped them discover that the substance they created may be even more well-suited for semiconductor construction than the commercial metallic arsenic from a chemical supplier.
“We actually think that, by forming this amorphous metallic arsenic, it’s going to be easier to produce semiconductors with the amorphous form compared to crystalline metallic arsenic…I think of it a little bit like putty. It’s very easy to get the amorphous material to transform because you don’t have to break down a crystalline structure.”
Not only will it be easier to use, but this form of metallic arsenic also reacts favourably to oxidization.
“We were really surprised to see that amorphous metallic arsenic was less susceptible to oxidation by atmospheric oxygen than crystalline arsenic…The amorphous form oxidized much slower than the crystalline form.”
Beyond the environmental benefits of this upcycling process, Van Genuchten says generating their own metallic arsenic from soil and water sources would completely remove the need for countries to import it, therefor disrupting the substance’s entire global supply chain as we know it.
He uses the United States as an example. “As of the last USGS report, not a single gram of metallic arsenic was produced domestically. One hundred per cent of it was imported, and the vast majority of that was from China.”
Looking forward, the researchers are conducting both semiconductor synthesis experiments with a parter in Sweden, as well as working with water utilities in Europe to test how this upcycling process works via fabricated, small-scale, on-site systems.
“That’s going to tell us a lot about what the challenges could be going from the labs to larger scale systems.”
