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Electric vehicles, renewable energy and mobile communications are helping Europe to become climate-neutral by 2050. Key to these technologies are ‘rare earths’ and other critical metals, such as neodymium for electric vehicles or cobalt and lithium for laptop and mobile phone batteries.
As well as being lost when technology is thrown away, these metals are often imported from regions like China and the Congo, where supply chains might be disrupted in a crisis.
The SOLCRIMET project, which is funded by the European Research Council, is helping to ensure that European manufacturers have reliable access to these materials, while reducing their environmental impact, saving resources and creating a more circular economy. Led by principal investigator Koen Binnemans, a rare earths specialist at the KU Leuven in Belgium, researchers are developing steps for a new green recycling approach – solvometallurgy.
The process ‘mines’ critical metals such as rare earths, indium and cobalt from discarded technology and waste from technology factories by using low-pollution solvents that have an electric charge. Techniques are tailored to different materials. ‘We have developed several processes for extracting and refining a range of critical metals,’ the chemistry professor says.
The project is having a big impact among scientists. A SOLCRIMET position paper outlining the main methods and advantages of solvometallurgy has become one of the top three most influential scientific papers in the last two years. Project researchers have also patented one process for rare-earth metals and are scaling it up in a second EU-funded project, NEMO.
The project is timely as mining has been suspended in many parts of the world due to the coronavirus crisis. ‘The importance of a diverse, local and sustainable supply has never been clearer,’ Binnemans concludes.
Mining waste
Traditional metal extraction uses heat – pyrometallurgy – or acids dissolved in water – hydrometallurgy, but this does not always work. ‘In many cases, critical metals cannot simply be reused,’ Binnemans explains. The metals might be in very thin coatings, mixed with other elements, oxidised or degraded in some other way.
SOLCRIMET has looked for a process able to produce high-purity metals from problem waste cost-effectively while respecting the environment.
It uses pairs of non-water-based organic solvents that do not mix. The different metals in the waste dissolve in the solvents to varying concentrations and are separated when the solvents move apart. Scientists can then purify and electrorefine the liquids to recover the target metals.
This process uses less water, energy and acid than existing extraction methods, making it more efficient. It also uses only green solvents – biodegradable solvents based on renewable materials. Binnemans points out that several of the project’s papers have been published in the journal Green Chemistry, ‘which sets strict limits in terms of what can be considered as being genuinely eco-friendly’.
Emerging capacity
SOLCRIMET is now continuing its search for new chemical systems that recover critical metals from waste. It is testing new pairs of solvents to find the most promising systems for a range of materials, while new electroactive compounds and non-aqueous electrolytes are in the pipeline for the refining part of the process.
‘Solvometallurgy is still an emerging domain,’ says Binnemans. He adds that there is scope for future research on how to recycle the solvents, creating a closed loop that makes the metal-recovery processes even more sustainable.
More immediately, the solvometallurgy concepts are proving useful for refining lithium for batteries, Binnemans adds. Although lithium deposits exist in parts of Europe, the metal goes to China for processing. According to Maroš Šefčovič, the former European Commission Vice-President for Energy Union: ‘The demand for processed refined lithium will be quite big in Europe, so it makes sense to have lithium-refining capacities here.’