Pre-concentration of fluorite from a rare earth element carbonatite deposit through the combination of magnetic separation and leaching

Abstract

Fluorspar, also known as fluorite, is commonly used as a raw material to produce fluorinated chemicals (e.g., hydrofluoric acid) or as a flux to lower the melting temperature in steel production. In the present study, a process was developed to produce a fluorite concentrate from a rare earth element (REE) bearing carbonatite. After an initial flotation step to remove gangue minerals from REE-bearing minerals, magnetic separation was applied to the flotation concentrate to pre-concentrate the fluorite into the non-magnetic fraction, while REE-bearing minerals were recovered in the magnetic fraction. The non-magnetic fraction was then subjected to hydrochloric acid leaching to solubilize carbonates and other mineral impurities. The optimum conditions were established using a conventional approach for magnetic separation and a surface response methodology for the leaching process. The optimum conditions for magnetic separation in this study were determined to be three subsequent passes at an intensity of 5,000 G. The optimum conditions of the leaching step in this study included a 5 M HCl solution, a reaction time of 1 h, a temperature of 20 °C, and a solid–liquid ratio fixed (S/L) of 25% (w/v). The fluorite content in the sample increased from 15.6% to 74.6% after magnetic separation and HCl leaching, while 76.7% of fluorite was recovered.