| The bioleaching of copper sulfide and its improving1. Two mechanism of bacterial leaching for copper sulfide minerals have ever been proposed, when copper sulfide minerals are leached directly by bacteria, it is the direct mechanism, such as:CuFeS2+4O2 bacteria CuSO4+FeSO4The second mechanism is indirect mechanism in which the ferrous ion and elemental sulfur releasing from sulfides are oxidized into ferric ion and sulfuric acid individually by bacteria, the copper sulfide minerals are dissolved as the following reaction:4FeSO4+2H2SO4+O2 bacteria 2Fe2(SO4)+2H2O2S0+2H2O+3O2 bacteria 2H2SO4 CuFeS2+2Fe2(SO4) CuSO4+5FeSO4+2S02. In the present work, the two bacterial species in the original solution from the Da Bao Mountain Copper Mine were isolated - Thiobacillus ferrooxidans(D-T.f) and Thiobacillus thiooxidans(D-T.t). The physiological characters for oxidation and leaching of these two bacteria were studied. It was demonstrated that D-T.f is characterized by higher activities oxidizing ferrous ion and reduced sulfur, with no activity oxidizing elemental sulfur; The D-T.t is characterized by higher activities oxidizing elemental sulfur, without the activity oxidizing ferrous ion and reduced sulfur. The D-T.f has good leaching efficiency on chalcopyrite concentrate. The D-T.t can not leach the chalcopyrite concentrate.3. The original bacteria were enriched with ferrous ion elemental sulfur reduced sulfur and chalcopyrite as energy resource, respectively. The results showed that the bacteria enriched by reduced sulfur exhibited most effective leaching chalcopyrite concentrate, then the bacteria enriched by ferrous ion or chalcopyrite. The bacteria enriched by elemental sulfur showed poor leaching efficiency. The results further showed that when the bacteria without the activity oxidizing the reduced sulfur were used, Its leaching efficiency is much worse than normal D-T.f. When the D-T.f and D-T.t were mixed to leach the chalcopyrite concentrate, it was demonstrated that the leaching of D-T.f is not accelerated byadding T.t at common circumstance, while when the elemental sulfur is added, the D-T.t will accelerate the leaching rate.4. Tt was revealed from the results that the efficiency of bacterial leaching of chalcopyrite is closely related to the physiological characters of oxidation of these bacteria reported. Discuss on the influence of ions or other substrate on bacterial oxidation and leaching of copper sulfide1. The influence of silver ion, cupric ion, elemental sulfur and pH on the bacterial oxidation for ferrous ion have been studied. It has been shown that silver ion has inhibition on bacterial oxidation of ferrous ion; cupric ion has anti-inhibition of silver ion; the influence of elemental sulfur is related to the ration of elemental sulfur to ferrous ion; pH has a certain suitable range.2. The bacterial leaching of chalcopyrite is characterized by much higher leaching rate of copper , much less and stable in dissolved total Fe in solution higher and stable pH, higher concentration of free bacteria, elemental sulfur occuring in the residue in the presence of silver ion. In absence of silver ion the leaching showed much lower leaching rate of copper, increasing dissolved total Fe in the solution, decreasing pH, less concentration of free bacteria, no elemental sulfur occurring in the residue. The best efficiency has been obtained using the D-T.f cultured with silver ion forehand, which has also slower oxidizing ability to the ferrous ion in the leaching solution. The acceleration of the bacterial leaching of chalcopyrite was made by adding D-T.t into the leaching solution with D-T.f and silver ion. Discuss on bio-electrochemistry between different mineral particles The copper sulfide minerals coming from Da Bao Mountain contains zincsulfide. The bacterial leaching behavior of the zinc sulfide minerals closely disseminated with pyrite has been studied. It showed that a lot of zinc ion from zinc sulfide is leached by D-T.f,...
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