A Novel Leach-Precipitation Process Towards Cleaner Production of Bastnaesite and Zero-Emission of Fluorine-Bearing Wastewater

A novel simple process for cleaner production of the bastnaesite concentrate has been developed. This process involves several steps: oxidative roasting without additive, coordination leaching using hydrochloric acid, and reductive precipitation. Coordination leaching is first used to leach out the rare earth elements (REEs) and fluorine in the roasted bastnaesite simultaneously according to the coordination of Ce4+ with fluorine ion (F–). The leaching of cerium, non-cerium REEs and fluorine were 90.3%, 97.6% and 60.1%, respectively, under optimal conditions. In the reductive precipitation step, 26.8% of the cerium, 8.3% of the non-cerium REEs, and > 99.9% of the fluorine were precipitated because of the reduction of the as-formed [CeFx]4–x complex by chlorine ion (Cl–) at elevated temperatures, forming (La,Ce)F3 irregular granular powders with a mean particle size of 0.958 μm and a fluorine-free mother liquor with fluorine content around 2 mg/L. These results suggest an envionmentally friendly route for the efficient recovery of REEs and fluorine from the bastnaesite concentrate with zero-emission of fluorine-bearing wastewater.