| The method of extracting valuble metals from limonitic laterite by atmospheric pressure acid leaching(APAL) has the advantages simple process, low energy consumption, and low capital costs; However, there still exists the promblem of low nickel extraction ratio in this process such as, which imposes great restrictions on the application.In this paper, on the basis of the mineralogy characteristics of nickel presented as isomorphism with iron in goethite of limonitic laterite, and the research of atmospheric pressure acid leaching of limonitic laterite and synthetized nickel goethite and leaching thermodynamics, reductant is used to improve the effect of atmospheric pressure acid leaching of limonitic laterite. The main conclusions are as follows:The leaching characteristics of nickel and iron of Atmospheric pressure acid leaching characteristics of limonitic laterite is similar, both of the leaching ratio are low. Leaching ratio of nickel and iron are41.86%and39.63%under the conditions:sulphuric acid concentration8%, liquid solid ratio10:1,rolating speed30r/m, temperature90℃and leaching time120min.Extraction of nickel and iron is obvious in linear correlation, which suggests that nickel and iron in laterite is closely associated each other, leaching kinetics of leaching nickel and iron in acid suggest that both metals accord with shrinking core model, controlled by chemical reaction, with activation energy of nickel and iron being42.2kJ/mol and,51.1kJ/mol. Atmospheric pressure acid leaching of laterite reduced by reductant can improve the extraction of nickel and iron obviously; leaching ratio of nickel an iron is59.7%and67.1%, respectively under the conditons:sulphuric acid concentration12%, temperature90℃, Na2SO330g/L and leaching time120min. Compared with the solution system without reductant, activation energy of nickel and iron is decreased from42.2kJ/mol to35.6kJ/mol and51.1kJ/mol to48.6kJ/mol,respectively.Atmospheric pressure acid leaching of synthetized nickeliferous goethite is seperated into two periods. In the first period(1-7min), the main process is the dissovement of nickel absorbed on the surface of goethite, and extraction of nickel and iron is obvious in linear correlation; leaching kinetics shows that leaching of nickel and iron accords with Avarmi equation, controlled by external diffusion. In the second period (15-120min), the main process is the extraction of nickel incorperated into the lattice of goethite, and chemical controlling step shifts from external diffusion to internal diffusion, and extraction of nickel and iron is nonlinear. Leaching characteristics of nickel and iron of nickel goethite further suggests that extraction of nickel and iron is nonlinear; according to the mechanism of hydrothermal synthesis and crystallization of goethite, the distribution of nickel and iron in goethite lattice nonheterogeneous, with most nickel located at the near surface site at anisotropic state. |
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