Behavior of phase transformation of Baotou mixed rare earth concentrate during oxidation roasting

Abstract Based on the new process named “Combination Method” for metallurgy and separating of Baotou mixed rare earth concentrate (BMREC), the aim of this paper is to clearly elucidate the phase change behavior of BMREC without additives during oxidative roasting at 450–800 oC. The results indicate that the bastnaesite in BMREC is decomposed at 450–550 oC, the weight loss is about 10.3 wt%, and the activation energy (E) is 144 kJ/mol. The bastnaesite in BMREC is decomposed into rare earth fluoride, rare earth oxides (La2O3, Ce7O12, Pr6O11 and Nd2O3), and CO2, particularly, with the increase of roasting temperature, bastnaesite in BMREC is more completely decomposed into LaF3, which makes a decrease in leaching rate of La during the HCl leaching process. Additionally, the maximum cerium oxidation efficiency reaches about 60 wt% when the roasting temperature is or above 500 oC, and the oxidation reaction rate of cerium increases with the roasting temperature.