Common clay could be used to trap harmful metals from mine waste

When waste material left behind by coal and metal mining is exposed to air and water, it can release the metal nickel into nearby streams, ponds, and groundwater. At high concentrations, nickel is toxic to people, fish, plants, and other living things.

New research conducted using the Canadian Light Source (CLS) at the University of Saskatchewan (USask) has confirmed that a common clay called kaolinite can trap some of the nickel in mine wastewater, reducing the amount that leaches into the local environment. The study was a collaboration between the Industry Services team at the CLS and former USask research scientists. 

Dr. Jim Hendry, distinguished emeritus professor at USask was investigating water treatment technology aimed at removing metals from mine-affected water.  In the laboratory, he and colleague Dr. Soumya Das, also formerly with the Department of Geological Sciences at USask, had been working to understand how kaolinite traps and releases nickel when exposed to water at various pH levels.

Hendry and Das reached out to Peter Blanchard of the Industry Services group at the CLS; they wanted to use synchrotron light to confirm the mechanism by which kaolinite clays sequester nickel. The CLS is one of only a handful of synchrotrons worldwide that has a team dedicated to supporting companies that want to use synchrotron tools in their research.

With the help of ultrabright X-rays at the CLS, the team verified that the way nickel bonds to clay depends on the pH of the water that contacts the clay.  At a lower pH, the bond between the nickel and clay is weak. But as you increase the pH, the bond strengthens. The stronger the bond, the more stable or tightly held the nickel becomes, and the less bioavailable it is. The team’s findings are published in the journal Applied Geochemistry.

Blanchard says the synchrotron provided strong confirmatory evidence of this “sponge” like behaviour in kaolinite clays. The technique they used – X-ray absorption spectroscopy – is element-specific, so they were able to focus in on nickel, to see how it bonds to the clay. “Our beamlines are very sensitive so we can analyze nickel at fairly low concentrations, something that’s difficult to do using a laboratory source. Synchrotron light is a powerful tool for researchers to have in their toolbox.”

There’s great interest in developing water treatment technology that can trap the leached metals released from mine waste, according to Blanchard. “Showing how nickel interacts with clays can provide scientists with the information they need to understand how it and other metals commonly found in mine waste move through soil and groundwater, which in turn can help industry design better water treatment systems.”

How could these findings be applied in the real world? Blanchard says that, in theory, a mining company that is trying to safely contain nickel could flow mine-affected water through a “filter” containing clay with a specific pH.

He says the team’s findings provide solid “proof of concept.” “This is definitely a good start because we now have a better understanding on how a natural substance in the environment can be used to sequester the nickel,” Blanchard says. “It shows that there’s something in nature that could potentially be modified to more safely contain nickel in the future.”

This research is ongoing, as Hendry, Das, and Blanchard continue to investigate the nickel sequestering behaviour of other clay minerals.

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Das, Soumya, M. Jim Hendry, and Peter ER Blanchard. "Characterizing nickel adsorption-desorption on kaolinite." Applied Geochemistry (2026): 106858. https://doi.org/10.1016/j.apgeochem.2026.106858 

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