Wang and 13 co-authors reported in late 2022 that heavy rare-earth elements (HREEs) such as Gd–Lu, Sc and Y are irreplaceable metals for a number of critical (including clean) technologies, but they are scarce. Ion-adsorption deposits, which form within weathering crusts, supply more than 95% of the global HREE demand.
Illustration of IAD mining via EKM and AIP mechanisms a, 3D illustration
of in situ EKM for an IAD. The hydrated REEs are expected to be mobilized
and extracted from an IAD under electrokinetic effects. I, current. b,
Illustration of the EKM mechanisms for REE recovery, including ion exchange,
electromigration, electroosmosis and the collection of EOF and precipitation.
c, Comparison between conventional leaching and the EKM technique and
schematic of the AIP process.
However, these deposits are currently mined via ammonium-salt-based leaching techniques that are responsible for severe environmental damage and show low recovery efficiency. As a result, the adoption of such techniques is restricted for REE mining, further exacerbating REE scarcity, which in turn could lead to supply chain disruptions.
The authors reported that the design of an innovative REE mining technique, electrokinetic mining (EKM), which enables green, efficient and selective recovery of REEs from weathering crusts. Its feasibility is demonstrated via bench-scale, scaled-up and on-site field experiments. Compared with conventional techniques, EKM achieves ~2.6 times higher recovery efficiency, an ~80% decrease in leaching agent usage and a ~70% reduction in metallic impurities in the obtained REEs.
As an additional benefit, the results point to an autonomous purification mechanism for REE enrichment, wherein the separation process is based on the mobility and reactivity diversity between REEs and metallic impurities. Overall, the evidence presented suggests that EKM is a viable mining technique, revealing new paths for the sustainable harvesting of natural resources.
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