A roast-leach process for extraction of rare earths from complex monazite-xenotime concentrates
- Bureau of Mines, Rolla, MO (United States)
The proposed process approaches the problem of solubilizing rare-earth phosphates (monazite and zenotime) found at the Pea Ridge iron mine in Sullivan, MO, from both a pyrometallurgical and hydrometallurgical point of view. It utilizes a roasting operation that converts the rare-earth phosphates to rare-earth oxides (REOs), which eliminates some costly and hazardous processing steps currently in practice. Different combinations of roasting temperatures and acid concentrations have been investigated to selectively extract the rare-earth values. Cerium is selectively solubilized by roasting at 427{degrees}C and leaching with a sulfuric acid concentration of 265 g/L. After the cerium is removed, the neodymium and lanthanum can be solubilized at a roasting temperature of 500{degrees}C and a sulfuric acid concentration of 88 g/L. Finally, neodymium, praseodymium, and yttrium are solubilized at a roasting temperature of 871{degrees}C and a sulfuric acid concentration of 265 g/L. Alternative leaching media, such as thiourea, sulfuric acid-doped thiourea mixtures, ammonium thiosulfate, nitric acid, and hydrochloric acid have also been investigated along with the addition of ultrasonic agitation. Using ultrasonics in addition to mechanical agitation, hydrochloric acid proved to be the best leaching medium. The best roasting temperatures for selective solubilization remained the same, but all of the leaching steps were conducted at 64 g/L hydrochloric acid.
- Sponsoring Organization:
- USDOE
- OSTI ID:
- 88719
- Report Number(s):
- CONF-931043-; ISSN 0149-6395; TRN: 95:004653-0040
- Journal Information:
- Separation Science and Technology, Vol. 30, Issue 7-9; Conference: 8. symposium on separation science and technology for energy applications, Gatlinburg, TN (United States), 24-28 Oct 1993; Other Information: PBD: Apr-May 1995
- Country of Publication:
- United States
- Language:
- English
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