Optimization and investigation of kinetics of sulfuric acid leaching of mixed hydroxide precipitate

In this study, the optimization and kinetics of the leaching of nickel in mixed hydroxide precipitate containing nickel in sulfuric acid (H2SO4) solutions were investigated. The optimum values of the experimental parameters on the solubility of nickel in mixed hydroxide precipitate were determined using central composite design. A mathematical model representing the dissolution kinetics was proposed according to the determined optimum parameter values. The effects of sulfuric acid (H2SO4) concentration, stirring speed, temperature and leaching time on the dissolution of nickel were investigated. As a result of the experiments, it was found that the dissolution increased with the increase of sulfuric acid concentration, stirring speed and reaction temperature, and decreased with the increase of solid/liquid ratio. It was determined that the dissolution kinetics of nickel from the precipitate fit the diffusion controlled model from the ash film. The activation energy for the dissolution process was calculated as 37.73 kJ/mol. After the dissolution process, evaporation process was applied to the solution and the compound with NiO structure was obtained.