The Study Of Thermo-bioleaching Mechanism Of Chalcopyrite And Therein Sulfur Speciation Transformation

The mechanism of thermo-bioleaching of chalcopyrite by the extreme thermophile Acidianus manzaensis and therein the sulfur speciation transformation were studied in the present thesis. Thermo-bioleaching mechanism of chalcopyrite was studied in terms of electrochemical behaviors of chalcopyrite electrode and therein intermediate products of the electrochemical reactions by an integrated methodology of surface component analytical methods including mainly synchrotron radiation XANES andcyclic votammetry, respectively. The electrochemical behaviors of chalcopyrite electrode were referred under static and rotate condition, in the presence of Acidianus manzaensis and bioleaching by Acidianus manzaensis, respectively. The effects of typical influencing factors and catalysts on the chalcopyrite dissolution and sulfur speciation transformation during chalcopyrite bioleaching by Acidianus manzaensis were further studied to reveal the relationship between them, and thus to elucidate the influence of these factors on the chalcopyrite thermo-bioleaching mechanism. The detailed research contents and the main results are shown as follows:(1) The sterilized thermo-electrochemical dissolution mechanism of chalcopyrite was firstly investigated by combined using sulfur K-edge, copper and iron L-edge X-ray absorption near-edge structure (XANES) and Raman spectroscopy and cyclic voltammetry. The results confirmed the thermo-reduction of chalcopyrite to bornite and chalcocite, and thermo-oxidation of chalcopyrite to covellite and sulfur. Meanwhile, the dissolve ways of chalcopyrite electrode scan in positive and negative directions were preliminary proposed.(2) The influence of temperature, pH and chloride ions on the chalcopyrite electrochemical behaviors in the absence and presence of Acidianus manzaensis were further studied based on the results of part one. The results showed the anodic current of chalcopyrite increased with the increased of temperature in sterilized condition. Acidianus manzaensis enhanced the oxidation reactions of chalcopyrite, and the maximum anodic oxidation current was observed at 65?. The anodic current of chalcopyrite electrode in the absence and presence of Acidianus manzaensis both increased with the increased of the pH. The addition of chloride ions to the 9K medium in the absence of and presence of Acidianus manzaensis both enhanced the anodic oxidation reactions of chalcopyriote.(3) Electrochemical behaviors of chalcopyrite electrode during the process of chemical leached and bioleached by Acidianus manzaensis, and the cyclic voltammograms of chalcopyrite in absence and presence of Acidianus manzaensis in the potential range of chalcopyrite bioleaching were further studied based on the results of part one. The results showed chalcopyrite was passivated both in chemical leaching and bioleaching. Passivation in the chemical leaching was mainly due to the accumulation of elemental sulfur on the electrode surface, while elemental sulfur, jarosite and other oxidation products accumulated on the electrode surface were responsible for the passivation of chalcopyrite bioleaching. Cyclic voltammograms (the scan potential range is 0.3?1V) of chalcopyrite electrode in the absence and presence of Acidianus manzaensis showed chalcopyrite were passivation in two conditions, and the presence of Acidianus manzaensis effectively enhanced the anodic oxidation reactions, but it also not eliminated the passivation.(4) The effect of temperature, pH and pulp concentration on the dissolution of chalcopyrite and the sulfur specation transformation during chalcopyrite bioleaching by Acidianus manzaensis were studied in terms bioleaching behaviors and sulfur K-edge XANES, XRD and FT-IR. The results showed the copper yields increased with the increased of temperature in sterilized leaching. However, the maximum of copper extraction ratio obtained at 65?in bioleaching. Sulfur speciation analysis showed that jarosite and elemental sulfur were the mainly products, and the formation rate of jarosite increased with the increased of temperature. Besides them, a small quantity of chalcocite and covellite were found at the initial and last phase of chalcopyrite bioleaching, respectively.Covellite should be the directily oxidation product of chalcopyrite, while chalcocite should be the reduction products of covellite (oxidation products of chalcopyrite). Cupric concentration increased with the increased of the pulp concentration, while the influence of pulp concentration on the copper extraction ratio was on the contrary. Sulfur speciation analysis showed jarosite was the most abound product in the solid samples, and the formation of elemental sulfur decreased with the increased of the pulp concentration. Chalcocite and covellite were respectively found at the initial and last phase of bioleaching. Copper yields increased with the decreased of pH during chalcopyrite sterilized leaching. However, the influence of pH on the chalcopyrite bioleaching was on the contrary. Sulfur speciation analysis indicated the content of jarosite in the solid samples and the copper ions concentration both increased with the increased of the initial pH, which indicated jarostie only has slightly inhibited role on the chalcopyrite thermo-bioleaching.(5)The influence of catalyst (chloride ions and activated carbon) on the dissolution of chalcopyrite and the sulfur speciation transformation during the chalcopyrite bioleaching by Acidianus manzaensis were studied in terms bioleaching behaviors and sulfur K-edge XANES, XRD and FT-IR. Bioleached results showed that the addition of 0.4g/L chloride ions in the bioleaching system increased the copper recovery from 79.2% to 89.3%, at the same time, sulfur speciation analysis showed chloride ions effectively eliminated the accumulation of elemental sulfur, which indicated the accumulation of elemental sulfur inhibited the dissolution of chalcopyrite. The addition of activated carbon effectively enhanced the dissolution of chalcopyrite; 2g/L activated carbon increased the copper extraction ratio from 64% to 95%. Sulfur speciation analysis showed the formation of chalcocite when the redox potential was lower, the addition of activated carbon had not changed the species of sulfur-containing products but enhanced the formation of them.