Bacterial leaching

Bacterial leaching is a leaching method that utilizes microorganisms and their metabolites to oxidize and immerse the target components in the ore. Has been found in a variety of bacterial leaching, the most important of bioleaching bacteria, the most common is iron oxide Thiobacillus. These bacteria are widely distributed in the mineral leaching of metal sulphide minerals, coal mine ore acidic water, are chemoautotrophic bacteria, bacteria of inorganic nutrients, organic matter as no external energy, iron, sulfur oxide released chemical energy As an energy source, it synthesizes its own cells with carbon dioxide in the atmosphere, inorganic nitrogen, phosphorus , sulfur and other inorganic nutrients in the solution. They are sour and amiable, and they are used to living in acidic waters containing many heavy metal ions.
In addition, bacteria which reduce sulfate to sulfide, reduce hydrogen sulfide to elemental sulfur, and oxidize nitrogen to nitrate have also been found.
1922 has been found that sulfur bacilli can leach mineral iron sulfide and zinc sulfide mineral, has been 60 years of history. At present, it is believed that bacterial leaching of sulfide minerals has direct and indirect effects: direct action of bacteria. Thiobacillus ferrooxidans living in acidic water can oxidize low-valent iron in sulfide ore to high-valent iron and oxidize sulfur to sulfuric acid, oxidizing In the process, the mineral crystal lattice is destroyed, and copper and other metals are transferred into the immersion liquid as sulfate.
The principle flow of bacterial leaching is shown in the figure below. The leaching can be immersed or immersed. Currently, the leaching method is more common. Depending on the composition of the immersion liquid, the metal can be recovered in different ways. If the content of useful components in the immersion liquid is high, the product may be obtained by metal replacement method, electrowinning method or chemical precipitation method; if the content of the useful component is low, the separation may be carried out by ion exchange method, activated carbon adsorption method or extraction method in advance. Set, and then use the corresponding method to analyze the product.

The tail liquid after the recovery of the metal is sent to the regeneration tank for regeneration, in which case the required oxygen, carbon dioxide, nutrient base, sufficient water and a certain acidity are supplied. When preparing the bacterial liquid, a certain amount of ferrous iron culture solution (mine water containing ferrous iron or mother liquor after copper plating) should be prepared first, and then a certain amount of nutrient base is added (the main solution of sulfur tetrasulfate is added potassium dihydrogen phosphate and Ammonium sulfate), adjust the pH value to 1.5-3.0 (about 2.0) with sulfuric acid, and connect the strain into the culture solution, and continuously blast air at 25-35 ° C until the high iron content in the liquid reaches the required value. There are two kinds of regeneration methods for the concentration of bacteria. One is to adjust the pH value of the tail liquid and then directly send it to the heap for leaching and regeneration. In the other, the tail liquid is placed in a special regeneration tank. The regenerated and regenerated bacteria liquid is sent to the leaching operation. In order to accelerate bacterial growth and oxidation, the bacteria can be pre-grown on vertical plates, plastic rings or corrugated honeycomb plastic plates, then placed in a regeneration tank, and added with nutrient base and blasted in air, when the tail liquid is rinsed. It is regenerated when immersed in the regeneration tank. Sunlight should be avoided when preparing and regenerating bacterial liquid to prevent ultraviolet rays from inhibiting the growth and reproduction of bacteria.
It can handle a variety of bacterial leaching of sulfide minerals, nickel, and zinc sulfide, chalcocite, covellite, bornite and tetrahedrite easily leached chalcopyrite leaching is difficult, and galena, molybdenite mine leaching. It is currently widely used to recover copper and uranium from lean ore, off-balance mines, tailings, small and scattered bonanzas and mined mines.
The bacterial leaching process is simple, the investment is small, and the cost is low, but the leaching period is long, the leaching rate is greatly affected by the temperature, and the acid consumption when the alkaline gangue is treated is high.

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