MINING OF RARE EARTH ELEMENTS: A KEY FOR THE PRODUCTION OF ENVIRONMENT-FRIENDLY VEHICLES

Dissemination of hybrid and electric vehicles is important for the reduction of hydrocarbon fuel consumption, which can contribute to decrease dispersion of CO2 as well as NOx and SOx into the atmosphere. Production of hybrid vehicles was enabled by installing motors with Dy-bearing NdBFe magnets in the engine. NdBFe magnets are also equipped in many other parts of a vehicle, in addition to the use of light rare earth elements (REEs) in the nickel-hydrogen battery. Thus, REEs are indispensable for the production of environment-friendly vehicles, and the demand of REEs is expected to increase significantly for the sustainable development of the society.

The production of REEs has been nearly monopolized by China (about 90 wt.% in the world) since late 1990s due to low REEs production costs and presence of REE-smelting and utilization industries in China, despite an estimation of huge REEs reserves in many other countries in the world. The present major sources of light REEs are the Bayan Obo Fe-REE deposit in Inner Mongolia and the Maoniuping carbonatite deposit in Sichuan. Heavy REEs are mainly supplied from ion-adsorption deposits related to granite weathering in southern China. However, the production of REEs in China, especially that from ion-adsorption deposits, is limited for the preservation of natural environment and protection of mineral resources.

To produce increasing number and volume of Dy-bearing NdBFe magnets installed in hybrid and electric vehicles, new supply sources for HREEs are required in addition to the Chinese ion-adsorption deposits. Possible sources of HREEs are 1) carbonatite deposits, 2) HREE-rich peralkaline rocks, 3) ion-adsorption deposits outside China, 4) Kiruna-type magnetite-apatite deposits, and 5) stratabound ferromanganese deposits. Among these five types, Kiruna-type magnetite-apatite deposits seem to be most practical and promising, because REEs can be recovered as byproducts of magnetite or apatite from the working mines, of which ore reserves are already confirmed.