Leaching Kinetics of Limonite-Type Laterite Nickel Ore from Ammonium Hydrogen Sulfate Solution at Atmospheric Pressure

The leaching behavior of nickel and iron in limonite-type laterite nickel ore was studied through ammonium hydrogen sulfate atmospheric leaching. The leaching temperature, ammonium bisulfate concentration, reaction time, and acid excess rate during the nickel dissolution process were optimized using the response surface methodology (RSM) Box–Behnken design. The parameters of the optimal process conditions obtained are 74% mass concentration of NH₄HSO₄, 83 min leaching time, 17% excess of NH₄HSO₄, and 112°C leaching temperature, and the maximum recovery of nickel is 90.9%. The kinetic behavior of nickel and iron leaching processes was evaluated using a shrinking core model, and their activation energies were calculated. The results show that the kinetic models for the leaching of nickel and iron are consistent with the chemical reaction model, which can be expressed by the linear equation 1 − (1 − a)^1/3 = k_rt. Based on the linear equation and Arrhenius equation, the activation energies of leached nickel and iron are 67.76 kJ/mol and 68.81 kJ/mol, respectively.