| Copper is used widely in various fields. With the development of economics, however, copper supply is lack in China due to copper mineral shortage. Therefore, it is signification to use low-grade copper mineral, which is chalcopyrite, to product copper. Compared to the traditional metallurgy technology of copper, bio-hydrometallurgy, which can deal with low-grade copper ore, has the advantages of low cost, simple process and less environment problem. However, low bioleaching rate of the chalcopyrite is a seriously problem which limited its industrial application. In this thesis, the chalcopyrite bioleaching is investigated, and its leaching mechanisms and process control are studied from the view of microbiology, mineralogy and metallurgy.ASH-07 is used as leaching bacteria and composed of synergic Thiobacillus ferrooxidans, Leptospirilum ferrooxidans and Thiobacillus thiooxidans. The optimal growing conditions are 1.2～1.8 for pH value and 45℃～50℃ for temperature. The growth activity and oxidability of ASH-07 are significantly improved after the domestication by Cu2+, Zn2+ and Ni2+. It is not only shortens the growth period, but also accelerates the oxidation of Fe2+. The concentrations of Cu2+, Zn2+ and Ni2+ which can be accepted by domesticated ASH-07 are 15.0 g·L-1,5.0 g·L-1 and 3.0 g·L-1, respectively.The adsorbed bacterial concentration on the chalcopyrite surface is measured by the ninhydrin colorimetry. The optimal measure conditions is 560 nm for wavelength, 25 min for cracking time,7.0 for pH value,15 min for heating time and 6 min for cooling time. The results of adsorbed bacterial concentration on different conditions of ore granularity, pulp concentration and initial pH value show that the higher absorbed bacterial concentration on unit pulp concentration occurs when the grain size is below 37.0μm and pulp concentration is 3.0 wt.%, and the absorbed bacterial concentration is 8.9×108 cell·mL-1 and 2.2×108 cell·mL-1 after leaching for 24 h, respectively. In addition, the higher the adsorbed bacterial concentration on unit pulp concentration on the chalcopyrite surface is, the higher the copper leaching rate is. The initial pH value has less influence on bacterial adsorption, but bacteria own better growth activity and oxidability when pH value is 1.2-1.8, resulted in higher copper leaching rate.The morphologies, thickness and chemical compositions of the oxide film formed on the chalcopyrite surface are examined by polarizing microscope, Scanning electron microscope (SEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The SEM observation of oxide film shows that the configuration transfers from granular to membraniform and the structure transfers from sparse to compact during the process of bioleaching for 168 h, and the thickness of the oxide film is 6.0 μm at 168 h. The XRD and XPS analysis of the oxide film indicates that the chemical state of element sulfur changes as S2-â†'S0â†'S4+â†'S6+. Moreover, it is deduced that Cu1-xFe1-ySz(x<y), S0, Fe(â…¢)-oxide, Fe(â…¢)-O-OH and jarosite are produced in sequence. Sulfide layer and S0 layer are intermediate products. The passivation is produced by jarosite layer. The main compositions of substance on bornite surface are copper sulfide and S0 after bioleaching for 144 h, which have no effect on its further leaching. It is the main reason that bornite bioleaching is prior to chalcopyrite.The chalcopyrite bioleaching passivation is inhibited by strengthening leaching and lowering pH value. In the strengthening leaching, it is not only prevents the formation of jarosite, but also removes coated jarosite layer from the surface of chaicopyrite, and the copper leaching rate is 43.5 wt.% higher than ordinary bioleaching. The bioleaching process is operated when the pH value is remained at 1.2, which not only ensures better bacterial growth activity and oxidability, but also prevents the formation of jarosite due to more concentration of H+. The copper leaching rate reaches 71.4 wt.% after leaching for 192 h. |
PDF Full Text Request