Critical raw metals, including the lanthanide series, scandium and yttrium, are critical components built into permanent magnets, electric vehicles, smartphones and more. Rare earths are now used in nearly all electronic devices. Contrary to their name, rare earths are found almost everywhere in the world. However, they are only found in certain regions in such concentrated quantities that the extremely costly mining work required to get hold of them is worthwhile. And these regions are typically within the sphere of influence of autocratic states – above all China – which makes the supply chains enormously dependent on political sensitivities and imponderables. So many electronic devices are already being manufactured today that production capacities are already at their limits with regard to some of the 17 rare earths. If digitization is to proceed as envisioned, rare earths will have to be recycled effectively. Something that is technically enormously complex and has hardly happened so far. For example, recycling rates for some rare earths are well below 3% in some cases.
How are rare earths mined?
The elements classified as rare earths occur naturally as admixtures in ores and must be purified before use. However, in addition to being energy and waste intensive, mining and separation are immensely challenging, often devastating entire swaths of land through significant mining operations with enormous pollution. An interesting alternative to mining is therefore the recycling of rare earths. But here, too, the cost of deconstruction and cleaning is a constraint. Only a tiny fraction of products are recycled with a view to recovering rare earths.
What are the challenges?
A significant portion of the cost of recycling rare earth elements is associated with their difficult separation. To improve the economic benefits of recycling, efficient solutions are needed to recover targeted rare earth elements from technologically relevant mixtures. The addition of recycled rare earth elements as a new source to the supply chain is expected to reduce pollution and energy costs associated with their primary mining and separation. In addition, a new domestic source of rare earths, in terms of effective WEEE full service, would be a positive contribution to technology and competitive pricing. Not least because it could reduce dependence on politically volatile supply chains.
Why effective recycling is without alternative
Rare earths are important materials in many consumer products, such as electronics and automobiles. These elements currently generate a significant environmental impact when mined. Despite their theoretical reusability, the clear vast majority are lost in the trash after the life cycle of the devices. Recycling appropriate products would provide manufacturers with a steady, domestic source of rare earths while reducing waste. Currently, the main barrier to rare earth element recycling is the cost required to clean up the mixtures recovered from consumer devices.
One possible approach
Recently, a group of researchers at the University of Pennsylvania discovered a separation process that could make the purification of recycled rare earth elements much less expensive. By developing a new organic compound (H3TriNOx) to bind rare earth cations, this group formed 15 different compounds. Studies showed that the “early” rare earth compounds (which contained lanthanum, cerium, praseodymium, neodymium, samarium or europium) preferred to aggregate and form dimeric species. The team observed no such aggregation for “late” rare earth compounds (containing gadolinium, terbium, dysprosium, yttrium, holmium, erbium, thulium, ytterbium, or lutetium).
As a result, the solubility difference of these compounds was large enough to allow efficient separation for all early/late rare earth combinations by a single filtration step. Optimization of separation conditions was used to improve the efficiency of specific combinations, particularly the neodymium/dysprosium and europium/yttrium pairs. These pairs are commonly used in permanent magnets and compact fluorescent lamps, respectively. The TriNOx separation system is expected to contribute to the recycling of these and other long-lived rare earth-containing products and provide a cheap and green new source for these critical raw materials.