Isolation and Characterization of Rare Earth Mineral Particles in Florida Phosphate Rock by DE Rapid Scan Radiography and HRXMT
Due to the national dependence on China to supply nearly all the demand for rare earth minerals, a project was proposed to investigate the RE minerals contained in Florida’s phosphate rock. Because traditional methods for resource identification often overlook trace amounts of minerals, dual-energy (DE) radiography followed by high-resolution X-ray microtomography (HRXMT) was used to characterize the rare earth minerals contained within Florida mining samples and to give liberation details. Three sample streams, shaking table concentrate, acid plant feed, and phosphogypsum, were separated into three size classes: >106 μm, 75-106 μm, and 53-75 μm. DE radiographs were taken at two energy levels and the ratio calculated. The images were thresholded to show only potential rare earth particles and then those particles were removed to prepare HRXMT samples. The samples were digitally reconstructed and the concentration of rare earth particles found using digital processing software. The overall concentrations for the three size classes were found to be 2157 ppm in the shaking table concentrate, 104 ppm in the acid plant feed, and 284 ppm in the phosphogypsum, respectively. Based on the degree of liberation, the best particle size to find fully liberated monazite particles is 75-106 μm.