Researchers at the University of Saskatchewan have found that a common clay mineral could help reduce the amount of nickel released from mine waste into surrounding groundwater and surface water.
Using ultrabright X-rays at the Canadian Light Source (CLS) facility, researchers confirmed that kaolinite can trap nickel from mine-affected water, with the effectiveness of the process depending significantly on the water’s pH.
Waste material left behind by coal and metal mining can release nickel when exposed to air and water. At elevated concentrations, the metal can be toxic to humans, fish, plants and other organisms.
The research involved the CLS Industry Services team and University of Saskatchewan (USask) Distinguished Professor Emeritus Dr. Jim Hendry and former research scientist Dr. Soumya Das. Their findings were published in the journal Applied Geochemistry.
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Hendry had been investigating technologies for removing metals from mine-affected water. Working with Das, formerly of USask’s Department of Geological Sciences, he examined how kaolinite captures and releases nickel when exposed to water under different pH conditions.
The researchers then worked with Peter Blanchard of the CLS Industry Services group to use synchrotron technology to determine how nickel bonds to the clay.
Using X-ray absorption spectroscopy, the team found that nickel bound relatively weakly to kaolinite under lower-pH conditions. As pH increases, however, the bond becomes stronger, leaving the nickel more stable, tightly held and less bioavailable.
Blanchard described the behaviour as similar to that of a “sponge,” with the synchrotron analysis providing strong evidence of the mechanism responsible for retaining nickel.
“Our beamlines are very sensitive so we can analyze nickel at fairly low concentrations, something that’s difficult to do using a laboratory source,” Blanchard said. “Synchrotron light is a powerful tool for researchers to have in their toolbox.”
The findings could eventually contribute to the development of treatment systems designed to capture metals leaching from mine waste.
“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,” Blanchard said.
One potential application could involve directing mine-affected water through a filter containing clay maintained under pH conditions that promote stronger nickel retention.
While the research remains at the proof-of-concept stage, Blanchard said the results demonstrate the potential for using naturally occurring materials as part of future nickel-management technologies.
“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,” he said. “It shows that there’s something in nature that could potentially be modified to more safely contain nickel in the future.”
Hendry, Das and Blanchard are continuing their research to examine how other clay minerals sequester nickel.
