Separation of Sc ₂ O ₃ from Bayan Obo tailings through an innovative roasting method

Abstract

Abstract Sc 2 O 3 was successfully extracted and separated from Bayan Obo tailings by a CaCl 2 ‐reductive carbon powder‐combinative roasting method. The optimum process condition was obtained through adjusting specific effect factors. It is found that Sc 2 O 3 with the ratio of 87.51 % is leached out under roasting temperature of 800 °C for 2 h through adding 73 % CaCl 2 , and 20 % reductive carbon powder with liquid to solid ratio of 3. Moreover, the specific reaction mechanism during roasting process was investigated by thermogravimetric–differential scanning calorimetry (TG‐DSC) and X‐ray diffraction (XRD) techniques. The results show that the main phases (SiO 2 , CaF 2 and NaFeSi 2 O 6 ) as well as important phases (LiScSi 2 O 6 , REFCO 3 and REPO 4 ) would turn into new phases (CaFeSiO 4 , Fe, Ca 3 (PO 4 ) 2 , NaCl, RE 2 O 3 and Sc 2 O 3 ) after complicated reactions, which effectively break up the original mineral compositions and activate the existing state of containing scandium matter, consequently facilitating the subsequent hydrochloric acid leaching process.