The Study Of The Thermophiles Bioleaching Behaviours And Mechanisms Of Chalcopyrite With Distinct Genetic Types

The thermophiles bioleaching behaviours and mechanisms of chalcopyrite with distinct genetic types were studied in the present thesis. The chalcopyrite samples are from porphyry type, marine volcanic type, skarn type copper deposit. On the basis of identification and domestication, different thermophiles bioleaching conditions of experiments were carried out, such as different pH values and pulp concentration. To investigate the different bioleaching behaviours, the nature of minerals, the biosorption mechanism, and the dissolution were analyzed. This study provided the theoretical basis of the thermophiles bioleaching mechanisms of chalcopyrite.The effects of pH values and pulp density on the thermophiles bioleaching behaviours of chalcopyrite with distinct genetic types were studied. Under different pH values leaching conditions, the copper leaching yield of marine volcanic chalcopyrite was significantly higher than the porphyry type and skarn type. This result indicated that the marine volcanic type is easier to dissolve than the other two type chalcopyrite. As pH value increasing, the cell concentration and the copper leaching yield of porphyry chalcopyrite increased first and then decreased, and reached a maximum at pH1.5. However, the cell concentration and the copper leaching yield of marine volcanic type and skarn type increased with pH value increasing. Under different pulp density, there were greater differences between behaviours. As pulp density increasing, the cell concentration and the copper leaching yield of porphyry type and skarn type increased first and then decreased, and reached a maximum at pulp density2.0%. However, the cell concentration and the copper leaching yield of marine volcanic type decreased with pulp density increasing. These results suggested that the copper leaching yield of three type chalcopyrite was positive correlations with the cell concentration, which is very important for bioleaching process.To reveal the different bioleaching behaviours of chalcopyrite essentially, the nature of chalcopyrite was studied by four aspects, crystal structure, electron binding energy, valence Fe (Mossbauer spectroscopy) and mineral composition (sulfide mineral). Marine volcanic chalcopyrite had smaller lattice energy and electron binding energy, the higher the Fe2+/Fe3+content, and Cu(II) on its surface, which caused this type chalcopyrite easier to dissolved. In addition, the effects of sulfide minerals on chalcopyrite bioleaching were also studied. The results showed that pyrite, sphalerite and covellite played a negative role in porphyry type and skarn type bioleaching, whereas they had a role in promoting marine volcanic chalcopyrite bioleaching.To reveal the biosorption mechanism of chalcopyrite essentially, the selective attachment, Zeta potential and adsorption affinity were studied. The results showed that after biosorption reached equilibrium, mineral adsorption capacity per unit area of extreme thermophilic bacteria order:skarn type> porphyry type> marine volcanic type. The Zeta potential results indicated that after biosorption, the isoelectric point (IEP) of three type chalcopyrite were consistent with the biosorption order. Analysis of the adsorption behavior of extreme thermophilic bacteria by EDLVO theory, it was found that electrostatic force (EL) played an important role in biosorption.To reveal the dissolution mechanism of chalcopyrite essentially, the redox reaction and leaching product were studied. When extreme thermophiles bioleaching, holes in conduction band and electrons in valence band simultaneously transferring, this meant that protons (H+) and extreme thermophilic bacteria attacked chalcopyrite simultaneously. Extreme thermophilic bioleaching depended on adsorption on mineral surfaces. It was found that the products of porphyry, marine volcanic and skarn chalcopyrite were M-lacking sulfide (CuFeS) and covellite, M-rich sulfide (Cu2Fe2S), M-lacking sulfide (Cu4Fe4S5) and M-rich sulfide (Cu3.5Fe4S2.5) respectively. Elemental sulfur (S0) layer hindered porphyry and skarn chalcopyrite further dissolution, so increasing the cell concentration was favor of these types chalcopyrite dissolved. The surface of the marine volcanic chalcopyrite covered with jarosite layer, thus reducing the pH value of the solution was conducive to marine volcanic chalcopyrite leaching. In addition, reaction equation described the dissolution of three type chalcopyrite, which revealed thermophilic bioleaching mechanism.