| With the increasing demand for nickel and magnesium, as well as the gradual depletion of nickel sulfide ore resources, the development of the nickel oxide ore is especially important. There are not only a lot of magnesium and silicon, but also a certain amount of nickel in serpentine. Therefore, it will be of great significance that synthetically recovering nickel, magnesium, silicon and other valuable components in serpentine. In this paper, atmospheric acid leaching was used to extract magnesium oxide, nickel oxide and silica from serpentine ore. Thermodynamic and kinetic were used to derive and analyze for the leaching process. The leaching agent was selected, leaching technology parameter was optimized and the recycling conditions of magnesium oxide, nickel and white carbon black were systematically studied. And the optimum processes about extracting nickel, magnesium and silicon from serpentine ore had been conformed. The specific contents are showed as follows:(1) According to phase analysis, the main crystalline phase in the serpentine which is selected in this project is Chrysotile, Mg3[Si2-xO5](OH)4-4x. Besides Chrysotile, there are some magnesium iron spinel (MgFe2O4) and quartz (SiO2) in it.(2) Thermodynamic analysis had been applied in the process of sulfuric acid leaching. According to the results, it was feasible thar extracting nickel and magnesium from serpentine at normal pressure. The optimum leaching conditions were derived by inspecting the single-factor of leaching, that was the ratio of liquid to solid was12:1, reaction time was4.5h, sulfuric acid concentration was3.0mol·L-1, leaching temperature was70℃, and the particle size of serpentine was less than0.074mm. At the optimum conditions, the leaching rates of nickel and magnesium were as high as85.74%and89.19%respectively. Kinetic model of leaching process was studied on the basis of optimized conditions, and the result showed that both the leaching process of nickel and magnesium were controlled by internal diffusion. The apparent activation energy of nickel and magnesium was obtained by calculating, that was and23.05KJ·mol-1respectively.(3) On the base of elimination for Fe, sodium hydroxide was used as precipitant to prepare nickel oxide. The optimum leaching conditions were derived by inspecting the single-factor, that was the final pH was9.4-9.6, reaction temperature was254.6℃, reaction time was10min, the calcination temperature was500℃, and the calcination time was2.Oh. The result of XRD showed that the production was nickel oxide.(4) Sodium carbonate was used as precipitant to prepare magnesium oxide. Optimum leaching conditions were derived from single-factor experiments, which was the reaction temperature was85℃, molar ratio of magnesium sulfate and sodium carbonate was1:1.5, reaction time was30min, calcination time was2.0h, and the calcination temperature was850℃. The results of XRD and morphology analysis showed that high purity, well-crystallized and spherical structured magnesium oxide can be obtained at the optimal conditions.(5) White carbon black was prepared by precipitation method which includes two stages. The first stage is leaching, i.t. preparation sodium silicate. The second stage is acidification of sodium silicate with hydrochloric acid, i.t. preparation silica. Optimum leaching conditions of the two stages were derived from single-factor experiments. In the first stage, the optimum conditions was that the reaction temperature was80℃, NaOH was mass fraction21%, the ratio of liquid to solid was16:1, the reaction time was2h, water consumption was30mL when washing, and without adding and sodium silicate additive. In the second stage, the optimum conditions reaction were pH was7at the end of reaction, reaction temperature was75℃, aging time was1.5h, and the aging temperature was70℃. |
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