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

Abstract

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.

Keywords

• rare earth concentrate
• active powder
• structure–activity relationship
• nh₃-scr
• catalytic activity