Aqueous stability relations in the hydrometallurgical processing of cerium bastnasite

Abstract

ABSTRACT The stability relations of cerium and its species in the hydrometallurgical processing of bastnasite were studied using Pourbaix diagrams. Different systems of Ce-(F)-(CO3)-(SO4)-(C2O4)-H2O were constructed using HSC Chemistry software with the necessary thermodynamic data. The Ce-F-H2O system exhibits a large stability region for CeF3 (pH∼ −1.5 – 12). The stability domain of was determined by Ce-CO3-H2 system in the pH of 4.5 – 12. The decomposition behaviours of CeFCO3 were studied by Ce-F-CO3-H2O system which shows the stability domain of CeFCO3 from neutral to basic media. The treatment of CeFCO3 with H2SO4 was investigated by depicting diagrams of Ce-F-CO3-SO4-H2O system. According to this system, CeFCO3 can be decomposed to produce soluble Ce sulphates at around pH 6.2. In contrast, alkaline treatment of CeFCO3 converts it to Ce(OH)3 at pH 11. Finally, the recovery of Ce by oxalate precipitation was studied by Ce-C2O4-H2O system which showed the domain of Ce oxalate decahydrate.