Abstract
Abstract Environmental pollution and valuable resource waste exist commonly in current metallurgical processes of bastnaesite concentrates. A novel associated process of calcification roasting, mineral beneficiation and acid leaching was proposed. This paper focused on the prior calcification roasting decomposition procedure. By studying the influence of roasting conditions on cerium oxidation, the optimum technology conditions were obtained: operated at 650°C for 60 min with 20% calcium hydroxide. After roasting, the leaching rate of rare earths can reach 98.84%. Bastnaesite can be sufficiently decomposed at lower temperature with calcium hydroxide added and the emission rate of fluorine decreased by over 98% compared with that during the roasting without additives. After the roasting, the main existence form of fluorine turned calcium fluoride, which made it possible for resource utilization and environmental protection. Particle sizes and scanning electron microscope and energy dispersive spectrometer analyses indicated that rare earth oxides gathered in particles of >48 μm, while generated calcium fluoride with fluffy cotton morphology distributed evenly.
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