Rare Earth Mineral Flotation Doug Schriner, Graduate Student Dr. Corby Anderson, Harrison-Western Professor
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Background
Mineral Flotation
Experimental Focus
As rare earth elements become increasingly prevalent in industry, their supply must rise to meet their demand. While not rare in the sense of hard to find, these elements occur in widely-dispersed, complex minerals that are often difficult to separate. Two minerals in particular, bastnaesite and monazite, have dominated the cerium and lanthanum supply for years. Their beneficiation has been studied and practiced (particularly by Molycorp at Mountain Pass), but new emphasis has been put on novel methods to recover these valuable metals. This poster will cover the established flotation practices and fundamentals along with an overview of the new Critical Materials Institute activities at the Kroll Institute for Extractive Metallurgy at Colorado School of Mines.
After the minerals have been liberated by comminution they are passed through a flotation mill to produce a rare-earth concentrate. This upgrading step often involves several different reagents combined to achieve the desired selectivity. The key process behind that selectivity is to render only the desired minerals hydrophobic. • Collectors attach mineral particles to the bubbles of gas and cause them to float • Fatty Acids, Hydroxamates, Amines • Depressants and Activators cause one species to be preferentially floated in order to achieve selectivity. • Sodium Sulfide, Potassium Alum, Soda Ash
Studying mineral flotation requires expertise in surface chemistry and plant practice. Several phenomena are key to understanding flotation: • Zeta Potential is a measure of the surface charge of a species in solution. • Contact Angle reveals whether a species is hydrophilic or hydrophobic. • Adsorption Density records the quantity of reagent required to cover a surface or achieve flotation.
Molycorp Flotation
Minerals Bastnasite is a rare-earth fluorocarbonate mineral, typically (Ce, La)CO3F, although it can contain other rare earth inclusions. It dominates the world cerium supply, and is mined prominently at Mountain Pass in California and Bayan Obo in China. Monazite, on the other hand, is a rare-earth phosphate: (Ce, La, Pr, Nd, Th)PO4. Before the discovery of the mountain pass deposit, it dominated the rare-earth supply, being recovered principally from heavy mineral sands. In hard rock deposits, the minerals must often be floated from one another in order to recover the valuable rare earth content from each mineral.
Fuerstenau 1957
Future Research Aplan 1988
Mineral liberation and gangue depression will always be targets for beneficiation research. The greater the extent of liberation, the easier the separation will be, which will lead to improved rare earth recovery and concentrate grade.
Acknowledgements The authors wish to acknowledge the support of the Critical Materials Institute. More information on the CMI can be found at https://cmi.ameslab.gov.
Authors Doug Schriner
[email protected] Ren et al 2000
Martinez and Uribe 1995
Dr. Corby Anderson
[email protected]
Colorado School of Mines, Hill Hall 900 15th Street, Golden, CO 80401
