Nickel leaching kinetics of high-grade nickel matte with sulfuric acid under atmospheric pressure

The nickel leaching kinetics of high-grade nickel matte with sulfuric acid under atmospheric pressure were studied. The effects of stirring speed, high-grade nickel matte particle size, reaction temperature and sulfuric acid concentration on the percentage of nickel dissolved were investigated. In the leaching process, the Ni3S2 in the dense high-grade nickel matte is decomposed which conforms to the shrinking core model. The results show that the unreacted Cu2S solid film has little effect on the reaction product diffusion, while the reaction temperature and particle size of the high-grade nickel matte have significant effects on the leaching process. The activation energy of the decomposition reaction is 39 kJ mol−1 according to the Arrhenius equation and the reaction order is 0.24 with respect to acid concentration. The corresponding kinetic expression for the leaching process is 1 − (1 − x)1/3 = 1.32 × 103c0.235r0−1exp(−39,034/RT)·t which indicates that the process is controlled by the interfacial chemical reaction.