Studies on the leaching kinetics of cobalt from spent catalyst with sulphuric acid

Kinetics of cobalt leaching from spent catalyst was investigated. The studied variables were particle size, stirring speed, sulphuric acid concentration and reaction temperature. The experiment results indicate that leaching rate of cobalt from spent catalyst increases with increasing sulphuric acid concentration. The results obtained show that leaching of ∼ 98% of cobalt is achieved using -0˙1 + 0˙074 mm particle size at a reaction temperature of 80°C for 240 min reaction time with 30% (w/w) sulphuric acid concentration. The solid/liquid ratio was maintained constant at 1 : 8 g mL-1. A kinetic model was suggested to describe the leaching process of cobalt from spent catalyst and leaching kinetics indicates that diffusion through the product layer is the rate controlling process during the reaction. The activation energy was determined to be ∼ 10˙0 kJ mol-1, which is characteristic for a diffusion controlled process.