I. Screening, isolation and domestication of strains
At present, the strains used for uranium , copper and gold heap leaching are first separated from the acid mine water containing sulfide minerals, and then domesticated and cultivated indoors. In the initial stage of the culture, (NH 4 ) 2 SO 4 , K 2 HPO 4 , KCl, MgSO 4 · 7H 2 O, Ca(NO 3 ) 2 , FeSO 4 · 7H 2 O, etc. are often added as nutrients of the bacteria. The use concentrations (g ∕ L) were: 0.45, 0.15, 0.05, 0.50, 0.01, 60, respectively. Control the pH value to about 2, and continue to inflate, the number of bacteria in the solution reaches 10 9 ∕ml can be used as a seed solution.
Second, the amount of inoculum inoculation
The above-mentioned cultured seed solution is added to the immersion liquid having a pH of about 2, the amount of the seed liquid is generally 10% to 20% of the amount of the immersion liquid, and the number of bacteria in the control immersion liquid is 10 6 to 10 8 . ∕ml.
Third, pH control during leaching
The leaching solution after adding the bacteria can be used to spray the ore. In the spray cycle, the pH value rises to about 3.0, and sulfuric acid needs to be added; in some cases, the oxidation reaction is strong, the pH value may drop to 0.5, and the leaching process Care should be taken to maintain the environment in which the bacteria grow.
Fourth, the control of temperature and aeration
Since the oxidation of sulfide ore by bacteria is an exothermic reaction, the temperature of the spray cycle should be carefully controlled below 38 °C; in addition, the dissolved solution should be aerated and oxygenated, and the aeration amount is controlled at 0.15 to 0.20 L∕L solution .
V. Circulation and treatment of leaching solution of uranium ore bacteria heap
When the uranium ore is leached, the acidity required for leaching is consistent with the pH of the medium required for bacterial growth and reproduction; during the process of oxidizing the sulfide ore, the uranium is also leached at the same time, so the uranium in the leaching solution is adsorbed by the ion exchange resin. The adsorbent tail liquid can generally be directly returned to the heap as a leach solution, and thus circulated until the end of the entire leaching period. It is only necessary to maintain the conditions for bacterial growth and reproduction in the cycle. If the uranium in the leachate from the uranium ore leaching solution is recovered by organic solvent extraction, recycling will be troublesome because organic matter is detrimental to the growth and reproduction of the bacteria. If the uranium in the leachate is recovered by a two-step precipitation method, the growth of the bacteria is also uncomfortable due to a large decrease in iron in the tail liquid and an increase in the pH of the medium. Therefore, in the above two cases, the tail liquid after recovery of uranium should not be directly returned to the yard as a leach solution.
6. Cyanide of gold mine bacterial heap leaching solution and pretreatment slag
The conditions for bacterial pretreatment of gold heap heap leaching are the same as those for uranium ore. During the pretreatment of bacteria, the leaching degree of arsenic in the solution is continuously determined. After the arsenic pyrite in the ore is oxidized to a predetermined requirement, the bacterial pretreatment is stopped. Treatment, the discharge solution is reserved for the next leaching cycle or new heap; at the same time, the pretreatment slag (the ore pretreated ore heap) is washed with alkaline water to completely eliminate the sulfuric acid and other acidic substances in the ore, and the effluent from the ore heap After the pH value reaches 9 to 9.5, the cyanide heap leaching is carried out.
Seven, copper ore bacteria heap leaching process
To date, copper ore is the most widely used for bacterial heap leaching. There are many successful examples of copper sulfide ore, whether it is secondary or primary, or the use of bacterial heap leaching in its mixed ore. The reaction of bacteria to oxidize copper sulfide ore is as follows:
Secondary sulfide ore CuS+2O 2 
CuSO 4
Primary sulfide ore CuFeS 2 +4O 2 CuSO 4 +FeSO 4
Sulfuric acid is also produced in bacterial heap leaching because of the presence of pyrite in the copper sulfide ore and the reaction of the bacteria to oxidize pyrite to produce sulfuric acid.
The copper heap leaching process has been fully matured and has been the most widely used, especially in the heap leaching of copper waste rock. The Copper Queen mine in Arizona, USA, and the Dexing copper mine in China use copper leaching of copper waste rock. Although the copper grade is very low (0.2%-0.3%), the amount of copper is still high due to the huge amount of waste rock. .
Copper waste rock heap leaching is mainly heap leaching of ore, the ore is not broken, the process is relatively simple, so the cost is low, and the benefits are considerable.
The process flow of copper ore bacteria heap leaching is shown in Figure 1.
Figure 1 Schematic diagram of copper ore bacterial heap leaching process
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