Dissolution of Cobalt from CoO/Al2O3 Catalyst with Mineral Acids

In this study, the dissolution of CoO from CoO/Al 2 O 3 catalyst with HCl, H 2 SO 4, and HNO 3 solutions was investigated in a batch reactor employing parameters that were expected to affect the dissolution rate of cobalt, such as stirring speed, temperature, and acid concentration. It was found that 99.82% of cobalt was dissolved after 4 h with HCl at 2 M, 75 °C, and a liquid-to-solid ratio (l/s) of 100 mL/g, while only 31.96% and 13.57% cobalt dissolutions were reached with H 2 SO 4 and HNO 3, respectively, under the same operation conditions. The difference in dissolution rates was due to the presence of different anions (Cl −, NO 3 −, and HSO 4 − ) involved in the surface reactions. Dissolution kinetic of cobalt was examined according to a heterogeneous model. It was found that the dissolution rate was controlled by surface chemical processes in all cases.