New way to produce heavy rare earth metals
13 March 2006
Chemists in China have for the first time demonstrated the electrochemical reduction of a solid oxide of a heavy rare earth metal into its metallic state. The process requires less energy than conventional methods of producing pure rare earth metals, said the researchers, and could provide an economically more attractive route to the metals' production. Heavy rare earth metals have potential applications in areas such advanced information storage devices and powerful permanent magnets.
Dihua Wang and colleagues from Wuhan University in China sandwiched pellets of the oxide of the heavy rare earth metal terbium between two pieces of molybdenum mesh as an electrode and inserted this in molten calcium chloride. A graphite rod was used as a counter electrode, and when a constant voltage was passed across the two electrodes, the terbium oxide became metallized.
Conventional formation of these metals from their oxides requires the conversion of the oxide to fluoride followed by calciothermic reduction at around 1500°C, followed by further refining.
'The energy consumption of the electrolytic process is far lower than existing industrial technologies,' George Chen, a member of the team who is now based at the University of Nottingham, UK, told Chemistry World. 'Also, conventional metallurgical theory is that in the presence of calcium the reduction of a metal compound to the metal should go through the calciothermic reduction process. However, this has been disproven in this work for the reduction solid heavy rare earth metal oxides, which is of fundamental significance.'Simon Hadlington
D Wang et al, Angew. Chem. Int. Ed., 2006 (DOI: 10.1002/anie.200503571)