Study on leaching valuable elements from Bayan Obo tailings

Abstract

After extracting rare earths minerals, iron minerals and fluorite from Bayan Obo ore, niobium and scandium which are riched in the mineral processing tailings coexist with the remaining rare earth. In order to recovery these valuable elements, the tailings was disposed with the method of activating roasting-acid leaching. The tailings was roasted with NaCl–Ca(OH) 2 under a temperature of 900 °C for 1.5 h. Weight percentages of NaCl-to-tailings and Ca(OH)2-to-tailings are 10% and 20% respectively. Then the roasted ore experienced two leaching stages from “hydrochloric acid pre-leaching at 90 °C for 1.5 h” to “intensified sulfuric acid leaching at 300 °C for 1 h”. The results show that, the leaching rates of niobium, scandium and rare earth in roasted ore could reach 86.80, 97.42 and 97.94% respectively under the conditions above. Moreover, the radioactivity per unit mass of leaching residue was reduced to 745 Bq/kg and environmentally friendly.