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其他题名Study on Mechanism and Kinetics of Bioleaching of pentlandite
关键词生物浸出 镍黄铁矿 动力学
其他摘要As an environmental benign technology with wide application, biohydrometallurgical process is characterized with low cost for recovering metal from low-grade ores. It has received increasing attention due to the depletion of mineral deposits and the more stringent regulation on the environmental protection. In this research, a pentlandite concentrate with a purity of 95% enriched from the ore taken in Jinchuan Mine in Gansu Province was used. Thiobacillus ferrooxidans (T.J) and a mesophile bacterium—MLY were tested, and the bioleaching mechanism and kinetics were discussed. The main objective of this work is to get necessary data and process fundamentals for the design and accomplishment of the commercial heap bioleaching for the low-grade Ni-Cu sulfide ores in Jinchuan Mine. The major contributions in this dissertation are as follows: (1) The characteristics of the two bacterial strains in bioleaching of pentlandite were investigated. The experimental results indicated that Thiobacillus ferrooxidans could oxidize Fe2+ to Fe3+ and element sulfur to H2SO4; some T.f. adhered or adsorbed to the surface of pentlandite particles in the process, and the adsorption of the bacteria was completed in an hour; the MLY bacteria oxidized Fe2+ much more quickly ascompared to T.f. An adapted T.f. strain was acquired by culturing in the slurry containing pentlandrite minerals. The results of bioleaching experiment showed that the adapted T.f. bacteria showed more strong activity in both of bioleaching and growth. Three factors were found to affect the performance of the adapted and unadapted T.f: the presence of cations, such as Ni"+, Mg2+ and Cu2+, in the slurry; the energy resources that bacteria may uptake from the solution medium and from the slurry; the shear stress produced by the movement of grains in the slurry. These three factors were tested separately and the results showed that the last one was the most important. Mechanisms of the bioleaching of pentlandite with T.f were explored. In the bioleaching process the action of T.f adhered on the surface of the pentlandite particles v/as demonstrated, but the experiments showed that the chemical reaction of Fe3+ contributed also to the bioleaching of pentlandite. The results of SEM and ES showed that the jarosite, precipitated from solution and amassed on some spots of the surface, covered the ore, but not impeded the leaching. However, Fe(OH)3 hydrolysated from Fe3+ covered the ore surface and impeded the leaching when the concentration of Fe3+ was high enough in the leachate. (4) The bioleaching process by MLY was investigated and the experimental results showed that the bioleaching of pentlandite by MLY at 50 °C differed from that by T.f No cells on the pentlandite surface during MLY leaching and the chemical actions, including the oxidation of Fe3+ and the acid dissolution, were the mechanisms for the leaching of pentlandite. In MLY leaching, the bacteria functioned only to oxidize Fe2+ to Fe3+ and produce oxidant. (5) The kinetic equations for the T.f. and MLY leaching were proposed separately according to the leaching models and the data from kinetic experiments with T.f. and MLY. The effect of temperature on the leaching kinetics was also investigated. Compared the calculated results to the experimental results, good agreement was found for the leaching of coarse ore particales, and the deviation was larger for fine particles. The influence of temperature was greater for the MLY leaching than for the T.f. leaching. (6) Bioleaching of the low-grade ores and tailings from Jinchuan Mine were tested with mixed culture of T.f. and L.f. in 10 L airlift reactor. The experiments showed that the pre-treating with sulfuric acid solution was essential. The dissolved oxygen and slurry concentration were the most important factors affecting the bioleaching rate and the yield. The Ni and Co leached rates were higher than Cu during the bioleaching. The optimized leaching conditions were found as: using a higher initial inoculation of mixed bacteria (including T.f and L.f), pH=2.0-2.5, the dissolved oxygen >3X10"6g/L, the redox potential >500 mV(SCE) and the temperature in 28~35°C during the bioleaching.
GB/T 7714
张广积. 镍黄铁矿生物浸出机理和动力学的研究[D]. 中国科学院过程工程研究所. 中国科学院过程工程研究所,2002.
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