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Lithium is a critical mineral used in batteries for electric vehicles, grid storage, and a host of personal electronics. It is also relatively scarce, so being able to efficiently isolate it from various host minerals is very important.

Canada holds substantial stores of lithium: It's estimated the country has 5.7 million tons in total reserves (including hard rock, brines, and geothermal sources), ranking 5th globally.

Researchers at Queen's University used the Canadian Light Source (CLS) at the University of Saskatchewan to identify better ways to separate montebrasite from spodumene—two of the most common lithium-bearing minerals. It is easier and less costly to extract lithium from the two host minerals individually than when they are combined.

The research is in The Journal of Â鶹ÒùÔºical Chemistry C.

Mining companies use a process called froth flotation to concentrate spodumene and montebrasite. The ore is ground into a fine powder, which is mixed with water. Special chemicals are then added that make the lithium-bearing mineral hydrophobic, allowing it to stick to air bubbles injected into the mix. The bubbles carry the lithium minerals to the surface as a froth that is skimmed off, cleaned, and further processed to get the lithium out.

Lead researcher Espoir Murhula, a Ph.D. student in the Robert M. Buchan Department of Mining Engineering at Queen's, says what they observed about the interaction between water and the surface of montebrasite—using the CLS—was a breakthrough.

"It was fascinating, as we unexpectedly saw that montebrasite was able to change the pH of water very quickly," says Murhula. "In acidic conditions, it behaved like a base, and in alkaline conditions, it behaved as an acid." In addition to the acid-base reactions, montebrasite also lost surface ions, such as fluoride and lithium.

Murhula says this reactivity—changing of the water's chemistry and pH—helps explain why mining companies often have trouble with froth flotation. The efficiency of the process depends on having just the right pH. The team's findings suggest miners can optimize extraction of lithium by adding reagents to adjust the water's pH throughout the flotation process.

Murhula and colleagues also found that the lithium and fluoride that come off montebrasite can form stable lithium fluoride, which is harmful to the environment and human health.

"Being aware of this phenomenon is essential, as it helps prevent environmental pollution from the release of process waters containing lithium fluoride, as well as potential harmful effects on human health," he noted.

"Access to the beamline at the Canadian Light Source was instrumental in understanding the change in surface chemistry at the atomic scale," says Murhula. "No other experimental method was able to indicate a change in bond strength and coordination of surface atoms."