Improved Flotation Separation of Rare Earth Ore

A critical step in the extraction of elements from ore, especially rare earth elements that are found in complex minerals, is separation. Froth flotation is a highly versatile method for physically separating particles based on differences in the ability of air bubbles to selectively adhere to specific mineral surfaces in a mineral/water slurry. The particles with attached air bubbles are then carried to the surface and removed, while the particles that remain are completely wetted stay in the liquid phase. Froth flotation is an attractive approach, but its effectiveness is limited for the rare earth minerals as they occur as phosphates, carbonates, fluorides, silicates and oxides with gangue minerals, which often share physical properties. By providing another tool for separation, increased understanding of localized surface chemistries in complex rare earth minerals could enable affordable processes that improve grades, recoveries, capital costs and operating costs for separation of rare earth elements from their ores. The techniques used to characterize surface chemistry in flotation relate to methods to make selective minerals hydrophobic by adjusting the surface charge so that ionic collectors may be adsorbed. In the case of non-sulfide minerals this is complicated by the fact that the waste materials are also non-sulfide, so very small differences in surface chemistry properties are observed. Finding chemical methods to selectively adsorb collectors onto the desired minerals requires additional fundamental understanding of the surface ions (potential determining ions) and charges (electrochemical potentials) encountered. The work, coupled with the development of a fundamental understanding can lead to greatly improved processes for concentration by froth flotation.