Optimization of process parameters and kinetic modelling for leaching of copper from oxidized copper ore in nitric acid solutions

The leaching behavior of Tunceli malachite mineral was investigated in nitric acid solutions by two steps to evaluate the effect of various experimental parameters. In the first step, the optimal conditions for the leaching process were determined, while in the second step, a kinetic evaluation for the process was performed. In the optimization experiments, the concentration of nitric acid, temperature, stirring speed, and solid-to-liquid ratio were selected as the independent variables, and the central composite design method (CCD) was applied to the experimental data. At the end of the experiments, the optimal values for the concentration of nitric acid, temperature, solid-to-liquid ratio and stirring speed were determined to be 0.5 mol/L, 50 °C, 0.004 g/mL and 500 r/min, respectively. Under the optimal conditions, the leaching rate was found to be 99% for 120 min of reaction time. In the kinetic evaluation tests, the effects of the concentration of nitric acid, temperature, stirring speed, solid-to-liquid ratio and particle size on the leaching rate of copper from malachite were investigated. In these tests, it was determined that the leaching rate increased with the increase in the temperature, acid concentration and stirring speed, and with the decrease in the particle size and solid-to-liquid ratio. In consequence of the kinetic analysis, it was observed that the leaching kinetics followed the mixed kinetic model, and a mathematical model for the leaching process was introduced. The activation energy for this process was calculated to be 36.23 kJ/mol.