Olivine is a rather unassuming rock. Olive brown to yellow green in color, this hard yet brittle mineral is thought to be the most abundant in Earth’s upper mantle. Chemically, olivine is magnesium iron silicate, though it contains other elements too. Economically, it’s close to worthless. Its limited industrial utility stretches to gemstones, metalworking, ceramics, and occasionally, as a gravel for road construction. At some mining sites, olivine is a waste product, stored in piles on the surface.
It’s certainly not an obvious choice as a source for battery materials.
But that’s exactly how it’s viewed by a group of New Zealand engineers. Christchurch-based Aspiring Materials has developed a patented chemical process that produces multiple valuable minerals from olivine, leaving no harmful waste behind. Perhaps most interesting to the energy sector is the rarest of its products—hard-to-source nickel-manganese-cobalt hydroxide that is increasingly required for lithium-ion battery production.
Sustainable Mineral Extraction Process
Aspiring’s pilot plant, which opened in February, is in an anonymous industrial estate east of the city. One corner of the main floor is dominated by a large stainless-steel tank, which is connected to a series of smaller tanks arranged in a stepped line. “Apart from our electrolysis system, the hardware is more typical of dairy plants,” says Colum Rice, Aspiring’s chief commercial officer. “The process is elegant but not massively complicated. Our inputs are rock, water, and renewable energy, and our products come with no CO 2 emissions.”
The rock is olivine “flour”; a fine, green-gray dust that is an unwanted by-product from refractory sand production. This is carried by screw conveyer into the largest tank, where it is combined with sulfuric acid. This acid-leaching step “transforms it into kind of an elemental soup,” says Megan Danczyk, lead chemical engineer at Aspiring. From there, it passes down the reaction chain vessels, where through the addition of caustic soda and careful management of particle size and temperature, three products can be individually extracted.
Megan Danczyk, Aspiring Materials’ lead chemical engineer, holds a scoop of magnesium hydroxide. Aspiring Minerals
About 50 percent of what the process makes is silica that can be a partial replacement for Portland cement, the most common variety of cement in the world. About 40 percent is a magnesium product suitable for use in carbon sequestration, wastewater treatment, and alloy manufacturing, among other things. The final 10 percent is a mixed metal product—iron combined with small quantities of a nickel-manganese-cobalt hydroxide. The battery industry calls it NMC, and it is the go-to material for high-power applications.
Danczyk explains that at the end of the extraction process, they’re left only with a salty brine. “This goes to an electrolyzer, which recycles and regenerates the acid we use for digestion and the base we use to separate the products. It’s a closed loop. We’re using the whole rock, and we’re processing it at low temperature and ambient pressure.”
Right now, Aspiring does each separation consecutively, or as Rice put it, “silica, reload, NMC, reload, magnesium.” The plan is to add two more reaction chains in parallel, so that the process can run continuously, shortening the runtime from three days to one.
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