Alternative flowsheet for rare earth beneficiation of Bear Lodge ore

The Bear Lodge Project is an important rare earth deposit in the United States. While extensive previous studies have settled on a crushing, screening, gravity and magnetic separation process, this study sets out to investigate an alternative flowsheet based on flotation and wet high intensity magnetic separation (WHIMS) to effectively beneficiate the rare earth oxide (REO) content of the Bear Lodge ore. Mineral characterization found ancylite was the dominant rare earth mineral, associated mainly with calcite and strontianite. Electrokinetic studies on the effects of pH, concentrations of various ions (Sr2+, HCO3− and CO32−) and hydroxamate concentrations were performed to establish the electric nature of the Bear Lodge ore. The isoelectric points (I.E.P) of the material in distilled water was around 5.27. The Sr2+ and CO32− ions in solution significantly affected the surface charge of the material. Adsorption studies suggested that the mechanism of hydroxamate adsorption is chemisorption, as hydroxamate adsorption increased on the Bear Lodge ore with an increase in temperature. WHIMS was employed to remove the iron content to reduce the interference of iron in following flotation process and consumption of hydroxamic acid. After cleaner flotation a REO grade of 11.2% at 72.7% recovery from a feed material of 4.5% REO was obtained. In light of the loss of REO in WHIMS process, it is possible to produce a concentrate containing 11.2% REO grade at 61.2% recovery.