Studies On The Electrochemical Performance And Technology Of Sulfide Bio-leaching

In this paper, the fundamental and technological investigations about roles of the oxidation of Fe*and increment of T. ferrooxidans have been proceeded as well as the bio條eaching of sulf ide .. mixed sulf ide and Da BaoShan' s copper ore. The electrochemistry mechanisms of the Fe1* oxidation and sulf ide anode behavior were studied using T. ferrooxidans modified and un-modified powder microelectrode in acid solution systematically.Cyclic votalmmetry, steady potentiodynamic, transient potential stair-step measurement show that the oxidation on the T. ferrooxidans modified carbon powder microelectrode is a reversibility reaction. The unti-diffusion current is 1. SSe^Am. cm"2. By calculation we get the charge diffusion coefficient is 6.25X lO^cm2. s"1. From CV curve we know that the relationship between ipand u12 is a quadric curve. Further more, the Acpp' is liner with u. To quick scan speed, the current晅hrough the T. ferrooxidans modified carbon powder microelectrodeinclude the micro-disc and thin layer current. When the concentration of Cu^under 0. OlSrool. dm"3, even if it varies from 0. 004mol. dnf3to 0. 012mol. dm"3, the presence of Cu^could increase the charge diffusion coefficient, rather than inhibit the Fe2* oxidation. When the electrolyte PH at 1.5-~2.5 and [Fe2*] under 0.16 mol. dm"3, the variation of pH and [Fe2*] can not change the reversibility of the electrode process. It demonstrates that the effect of T. ferrooxidans on the Fe2* oxidation is more active at pH 2 and [Fe2l 0.16mol. dm"3.The T. ferrooxidans bath culture bio-cell is designed. The dynamic equations about the output voltage of bio-cell and the growth of T. ferrooxidans are proposed by utilization of calculation and measuring valve about voltage, [Fe2*] and [Fe3*] concentration. The calculated results using dynamic equation are well consistence with the measurements.Based on the character of powder micro-electrode, which could detect the transient reaction process, the intermediate reactions of the anode process of pyrite^chalcopyrite>covelite,pentlandite,which could not be detected using common electrode are measured by CV test. When the T. ferrooxidans in presence as well as in the presence of Fe3* and the decreasing of pH , the anode process of sulf ide are the successive reactions, company with the peak current and reversibility of reaction increasing, the peak potential negatively moving and the peak area expanding. The T. ferrooxidans has contribution to the oxidation of element sulfur formatted during the intermediate process. The pH has complex effect on the pentlandite anode process.The semiconductor electrochemistry investigate demonstrate that the pyrite is oxidized by the transfer of holes between semiconductor and solution surface, but to chalcopyrite, covelite and penlandite, in the initial time is by the holes transfer, then company with the electron transfer.The dynamic study show that the anode behavior of pyrite, chalcopyrite and penlandite is a mixed control process by electro- chemical reaction and charge diffusion, but to the covelite, charge diffusion is the main control factor. The polarize Tafel curve prove that the addition of T. ferrooxidans can makes the corrosion potential of sulfide decrease , the exchange current increase and the oxidation rate is accelerated. From the potential step-stair measurement, the charge diffusion coefficient and the reaction velocity constant of the anode process of individual and mixed sulfide are acquired. The results show that the corrosion current of the mixed sulfide is higher than that of the individual one. The results of leaching for the mixed sulfide certify the galvanic effect in the processing of the bio- leaching. The leaching for the individual sulfide show that the pyrite will be decomposed continuously company with the decrease of the pH, but the chalcopyrite and pentlandite has little contribution to the decrease of pH.The scan electron microscope and surface electron probe method verify the mixed potential effect in the sulfide bio-leachin...