Surface Properties and Denitrification Performance of Impurity-Removed Rare Earth Concentrate

Acid leaching and alkali roasting were used to remove impurities such as Ca and Si in Baiyun Obo rare earth concentrate. The effects of acid-base treatment on the physical and chemical properties of the samples were analyzed by scanning electron microscopy, X-ray diffraction, Brunauer-Emmett-Teller characterization, X-ray photoelectron spectroscopy, H₂-temperature-programmed reduction, NH₃-temperature-programmed desorption (TPD), and NO-TPD. Results showed that the content of Ce₇O₁₂ in the rare earth concentrates increased and the dispersion was uniform. The grains became smaller, the specific surface area of rare earth concentrates increased, and the active sites were more exposed. Ce coexisted in the form of Ce³⁺ and Ce⁴⁺, whereas Fe coexisted in the form of Fe³⁺ and Fe²⁺. The content of Fe³⁺ was increased. The acid-base-treated rare earth concentrates had a denitration efficiency of 87.4% at a reaction temperature of 400 °C.