Abstract
Sc2O3 was successfully extracted and separated from Bayan Obo tailings by a CaCl2-reductive carbon powder-combinative roasting method. The optimum process condition was obtained through adjusting specific effect factors. It is found that Sc2O3 with the ratio of 87.51 % is leached out under roasting temperature of 800 °C for 2 h through adding 73 % CaCl2, 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 (SiO2, CaF2 and NaFeSi2O6) as well as important phases (LiScSi2O6, REFCO3 and REPO4) would turn into new phases (CaFeSiO4, Fe, Ca3(PO4)2, NaCl, RE2O3 and Sc2O3) 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.
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