SASKATOON, Sask. — Arsenic waste at closed mines is one of Canada’s largest and most expensive environmental liabilities, driven in large part by historic gold mining.
At the Giant Mine site in Yellowknife, NWT, 237,000 tonnes of arsenic trioxide dust is stored underground – a volume that would fill seven 10-storey buildings or 9,480 dump trucks. The estimated cost for remediating the site is a whopping $4.4 billion CAD.
Canada isn’t alone in dealing with this potential threat to the environment and human health: Legacy arsenic mine waste is a global problem facing many other countries including Australia, France and the United States.
However, this liability is increasingly being viewed as a potential asset, with an altered form of the element – metallic arsenic – now classified as a critical mineral by several countries because of its importance for green technologies ranging from solar panels to EV batteries. Little surprise then that research teams from around the world are actively looking for ways to transform the material.
As part of an international collaboration, environmental engineers Tamara Etmannski from the University of British Columbia and Case van Genuchten at the Geological Survey of Denmark and Greenland have developed a method for converting arsenic from its carcinogenic form into the sought-after form that could play a key role in society’s transition away from fossil fuels.
The early results of their research, say Etmannski and van Genuchten, have been “very promising.” The conversion process is relatively simple, and because the metallic arsenic is separated from the remaining waste during processing, it is easier to remove other valuable elements such as gold, which do not dissolve in the reaction.
van Genuchten says one of the biggest surprises in their project came from their use of the Canadian Light Source (CLS) at the University of Saskatchewan (USask); ultrabright synchrotron light enabled the researchers to examine the converted arsenic’s chemical structure.
“While the [upcycled] arsenic is very pure, more than 99 per cent arsenic, the structure of it is completely different than commercial arsenic,” he says. van Genuchten is keen to explore whether this difference is useful in the synthesis of semiconductors.
Big picture, says Etmannski, the team has two goals: first, create large amounts of metallic arsenic for use in electronics manufacturing. And second, transform all the vast stores of arsenic waste so it “doesn’t even exist in place anymore…so there's no further risk of contamination to the environment.”
Once they’ve successfully demonstrated that they can make a semiconductor from their converted arsenic, says Etmannski, the next big step will be determining whether they can scale up the process to put it into practice at Giant Mine, to upcycle the enormous store of arsenic waste for commercial use.
