PDF Basket
Rare earth elements (REEs) are used in a wide range of products such as optical lenses and magnets, as well as in processes such as ceramics, metallurgy and polishing. However, as Europe does not currently produce these minerals, it is dependent on imports, mainly from China.
To help increase European self-sufficiency, SecREEts developed methods to extract rare earth concentrates from the phosphate rocks used in fertiliser production. The REEs were separated by a chromatographic method before molten salt electrolysis was undertaken to produce rare earth metals for magnets.
“Extracting REEs with virtually no additional environmental footprint, offers a highly sustainable alternative to new mining,” says Arne Petter Ratvik, coordinator of the EU-funded project and senior research scientist with SINTEF, one of Europe’s largest independent research organisations.
“Crucially our SecREEts separation processes could significantly contribute to the circular economy as they can be adopted for other feed sources containing REEs, including secondary resources such as end-of-life magnets and electronic waste items,” Ratvik adds.
REE extraction
The phosphate rocks used in fertiliser production typically contain 0.3 % to 1 % REEs. But when the fertiliser is produced using the nitrophosphate process, these REEs end up in the finished fertiliser, where they have no value. SecREEts developed a process for extracting the rare earths directly from this process.
While the mixed acid process is the more common route for producing fertiliser, the REEs end up in a tailing with gypsum and radioactive elements, making them more difficult to separate.
“The nitrophosphate process is superior for getting REEs because they can be extracted directly in existing plants, by simply introducing an additional step,” explains Ratvik.
SecREEts successfully conducted three pilots. In the first, REEs were extracted directly from the fertiliser process in the plant of project partner Yara, which uses around 650 000 tonnes of phosphate rocks annually. REE concentrate was extracted from the phosphate-rich solution, known as mother liquor, using precipitation techniques.
This concentrate was sent to REEtec, where high-purity individual rare earth oxides (REOs) were separated by a novel chromatographic process, more environmentally friendly than existing solvent-solvent extraction methods.
These REOs were then sent to specialist engineers at Less Common Metals to produce metals using a fluoride-based electrolysis process at 1 050 °C to 1 100 °C. The resulting metal was then alloyed and strip cast for high-performance magnet production.
“High-strength magnets are critical to the European economy for applications such as electric vehicles, industrial motors and wind turbines,” explains Ratvik. The quality of the magnet alloys was validated by magnet producer Vacuumschmelze.
SecREEts’ modular process can be deployed to all fertiliser producers using the nitrophosphate process.
Filtering opportunities and threats
With the European Commission’s forthcoming Critical Raw Materials Act aiming to ensure REE supply, these innovations are timely.
While Europe does actually have several large REE deposits – notably the Fen area in Norway and recently discovered deposits in Kiruna, Sweden – supply challenges remain.
“Going from exploring mineral deposits, to mining them, is costly and the licensing can take 10 to 15 years,” says Ratvik. “Our process offers a viable and faster alternative.”
Project partner REEtec has announced its ambition to be the first in Europe to produce high-purity REOs at industrial scale, having raised the necessary capital with LKAB as the largest shareholder. However, initially the RE concentrate will come from a Canadian mine due to current European constraints on fertiliser availability.
“Chinese plans to focus more production on finished products could disrupt European supply and manufacturing, so we should be exploring multiple value chains for a reliable supply of critical materials,” concludes Ratvik.
Meanwhile, Ratvik continues to exploit the SecREEts processes for REE recovery, contributing to projects working to achieve Europe’s green transition, such as the EU-funded REEPRODUCE project.