Bacterial beneficiation principle, process and precautions

Mineral called bioleaching bacteria, it is the use of catalytic action of certain microorganisms, so that the metal ores dissolved out. For example, there is a sulfur-oxidizing bacterium which has the ability to oxidize elemental sulfur to form sulfuric acid in solution. Another type is iron oxidizing bacteria, which has the ability to accelerate the oxidation of FeSO4 to Fe2(SO4)3, which greatly increases the Fe2(SO4)3 content in the solution. The H2SO4 and Fe2(SO4)3 solutions are effective solvents for sulfide ore and other minerals. For example, pyrite is generally contained in polymetallic sulfide ore. In the presence of water and oxygen, pyrite slowly oxidizes and forms FeSO4 and H2SO4. The reaction formula is: Chemical action: 2FeS2+7O2+2H2O ————→2FeSO4+2H2SO4 Ferric bacteria in the presence of aerobic and sulfuric acid, the FeSO4 is oxidized to Fe2(SO4)3 at a very fast rate. The reaction formula is: Bacterial action: 2FeSO4+H2S04+1 / 2O2 ---- → Fe2 (SO4) 3 + H2O Fe2 (SO4) 3 can minerals dissolved out of the metal, for example, when the luminance copper oRE, can generate CuSO4, FeSO4, and S, the reaction is: Cu2S +3Fe2(SO4)3—→2CuSO4+4FeSO4+S The FeSO4 formed by the above reaction can be reoxidized by iron oxidizing bacteria to form Fe2(SO4)3, and the reaction is repeatedly circulated in the solution, and the leaching action is continuously performed. If there is sulfur oxidizing bacteria in the solution, the S formed by the reaction will be oxidized by sulfur oxidizing bacteria to form H2SO4, which is more effective for the leaching of ore. The reaction formula is: Bacterial action: 2S+3O2+2H2O —— ——→2H2SO4 Advantages of bacterial leaching:

(1) The equipment is simple and easy to operate.

(2) Adapted to the treatment of lean ore, waste ore, tailings and slag, etc.

(3) Comprehensive leaching and comprehensive recovery of various metals,

(4) At present, the bacterial leaching process for copper and uranium is relatively mature, and the copper leaching solution can recover copper by extraction-electrowinning method or iron displacement-flotation method.
The main disadvantage of bacterial leaching is that the cultivation of bacteria is troublesome and the leaching period is relatively long. There are many examples of application of bacterial beneficiation in China, such as a copper mine in Guangdong, bacterial leaching in an old mining area in a copper mine in Anhui, and a copper mine in Hunan. This paper introduces the application of bacterial leaching to treat copper-bearing tailings in a copper mine in Hunan. A large number of flotation tailings and re-election tailings exist in a copper mine in Hunan. The flotation tailings contain 0.11%~0.20% copper; the re-election tailings contain 2.25%~1.50% copper, and both tailings contain Rare metal. The process of bacterial leaching of tailings is shown in Figure 7-7. Since the tailings have a fine particle size, the leaching tank is used for leaching. The acid, acidified water and alkaline gangue in the ore are first added. When the pH reaches about 2.0, the leaching solution containing the high-iron (Fe3+) is added for cyclic leaching until the concentration of copper and rare metals in the immersion liquid is low. Then add a copper, rare metal bacteria infusion, when the concentration of the leachate is lower, and then wash for 2 to 3 days to discharge.

The tailings leaching time is 20 days, and the leaching results are listed in Table 7-2. After the rare metal in the leachate is adsorbed, the tail liquid contains about 1.5-2.0 g/L of copper. The copper is precipitated into sponge copper by iron replacement. The chemical reaction formula is: Fe+CuSO4—→FeSO4+Cu↓
(1) The higher the copper content of the replacement liquid, the lower the iron content should be as little as possible, pH=1.8%~2.0; Table 7-2, the result of bacterial leaching of tailings