New technique could help solve two global challenges at once by recovering valuable metals from waste tailings
Researchers have found a way to remove carbon dioxide from the atmosphere while mining critical metals needed for renewable energy infrastructure.
“To build the ‘green grid,’ we need to at least double the amount of mining we do globally to get the raw materials we need,” says Sasha Wilson, professor in the Department of Earth and Atmospheric Sciences at the University of Alberta and Canada Research Chair in Biogeochemistry of Sustainable Mineral Resources. Additionally, billions of tonnes of carbon dioxide need to be removed from the atmosphere by 2100 to limit climate warming, Wilson adds.
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As Wilson explains, to create the renewable energy infrastructure required to achieve carbon neutrality, we need more metals such as nickel, chromium and platinum, which are used in everything from batteries to electric vehicles. The problem is that current methods of obtaining these metals aren’t efficient and effective enough.
In addition, many of the metals needed to build green infrastructure are mined from rocks rich in minerals like magnesium, calcium and iron. The current process of extracting the metals from these rocks results in tailings, in the form of finely pulverized mineral wastes that are disposed of. However, Wilson and collaborator Jessica Hamilton at the Australian Synchrotron have found a way to extract more nickel from these tailings.
“Today, a lot of nickel mines throw out about a third of the nickel they mine as waste because it’s in tailings, in a form that’s not recoverable,” says Wilson. “We’ve figured out a way to recover that nickel while sequestering CO2.”
The new process essentially solves two problems at once by increasing the yield of metals from nickel mines while also decreasing the amount of CO2 in the atmosphere.
Wilson and Hamilton, along with collaborators Andrew Frierdich from Monash University and Phil Renforth from Heriot-Watt University, recently received a $2.8-million grant from the Grantham Foundation for the Protection of the Environment that will allow them to demonstrate the process on a pre-industrial scale. By testing the method on a larger scale, they will streamline the process and measure how much time and energy it takes. Next steps will involve finding industry partners to pilot the process in existing mines.
Most mined nickel comes from deposits called laterites – a type of old, weathered soil formed by minerals breaking down over millions of years. It’s much easier to extract metals from laterites than from unweathered rocks, Wilson notes.
“You only need to know how to process one part of the laterite to get as much nickel out as possible, whereas in the type of rocks that host nickel in Canada, the nickel might be trapped in 20 different types of the compound and you have to pick one or two to target,” Wilson explains. “It’s just not possible to design a mine that can extract all of it from every different type of material.”
By creating artificial nickel laterites, the researchers are able to fast-track the process of the rocks breaking down from millions of years to just a few days.
“We get the same benefit in terms of ease of processing and getting more of the resource out of the rock.”
The tailings are transformed into artificial nickel laterites through an acid heap-leaching technique that mimics the natural process. Wilson says the technique involves a neutralization reaction similar to the vinegar and baking soda volcanoes familiar to young science students.
“The acid dissolves out all the nickel and concentrates it into basically just rust. The nickel’s in the rust, and all the magnesium and calcium we need to trap carbon dioxide just falls out the bottom and we bind it with CO2 from the air.”
While the researchers haven’t yet confirmed where the pre-industrial scale testing will occur, Wilson says the new solution has a uniquely Albertan benefit.
“For nickel, it’s relevant to Alberta and the growing hydrogen economy here. You need to be able to produce a lot of nickel to process and store hydrogen.”
Wilson also notes there’s an appetite within the minerals industry for innovative solutions such as this one, as many companies have committed to reaching carbon-neutral operations within the next 10 to 30 years.
“They’re making really huge changes to their operations to reach these goals. It’s part of their social licence to operate – their investors and the communities within which they operate expect it,” Wilson says. “Some mining companies are looking to the type of technologies we’re developing to start mining CO2 from the air and offer CO2 removal as a service, which is really cool.”
Wilson and her collaborators also developed measurement, monitoring and verification protocols for CO2 removal in mine tailings, which allows companies to measure and verify the amount of CO2 they’ve sequestered. This will enable individuals to claim credit for the removal and provides a way to account for how much CO2 is being sequestered globally.
The new process moves us a step closer to a sustainable renewable energy infrastructure while also benefiting multiple industries, says Wilson.
“If you can have more efficient mines that produce less waste for the amount of resource you extract, that’s a nice benefit.
“By turning them into carbon sequestration operations too, there are possibilities to extend the lives of mines so you don’t have to open new mines when you already know where you’ve got a resource. It can provide more stability to communities that rely on this industry.”
| By Adrianna MacPherson
This article was submitted by the University of Alberta’s Folio online magazine, a Troy Media Editorial Content Provider Partner.
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