Bacterial leaching of copper mineral raw materials and process technology

Copper oxide ore leaching residues can be used to treat bacterial or silicate type low carbonate content, mixed mineral, lean ore, ore sheet, waste rock, tailings, copper slag and goaf and the mine waste Mine and so on.

1. Preparation and regeneration of bacterial leaching agent

Bacterial leaching for copper is currently a variety of iron oxide mainly Thiobacillus, Thiobacillus ferrooxidans bacteria iron oxide and the like. Under acidic conditions, they can quickly oxidize ferrous sulfate to high-sulfur sulfate (the oxidation rate is 112-120 times higher than natural oxidation), and oxidize elemental sulfur and low-priced sulfur to sulfuric acid.

Industrial preparation of bacterial leaching agents generally includes the following steps:

(1) Preparing a certain amount of ferrous medium, the main component of which is ferrous sulfate, which can be obtained by using acidic pit water containing ferrous ions, mother liquor after replacing copper with iron or scrapping iron with sulfuric acid solution. In addition, a certain amount of medium must be added to the culture solution, and for Thiobacillus ferrooxidans, (NH ₄ ) ₂ SO ₄ and K ₂ HPO _{4 are} mainly added.

(2) Adjust the pH to 1.8 to 2.0 with 10% sulfuric acid.

(3) Inoculation strains, in order to ensure a certain oxidation rate, the general inoculum should be no less than 1/10 of the amount of the solution, and the continuous culture method is not subject to this limitation.

(d) Continuously blast air under suitable temperature conditions (20 ~ 35 ° C) until the high iron content in the solution reaches the required level.

There are two methods for leaching agent regeneration, namely, intermittent culture methods and continuous culture methods. Intermittent culture is to use 70% to 80% of the cultured bacterial liquid for leaching, and 20% to 30% of the bacterial liquid (called old liquid) is left as a strain in the culture tank, and the tail liquid is re-added for regeneration. The continuous process is to continuously flow the tail liquid from one end of the culture tank, and the cultured leaching agent continuously flows out from the other end of the culture tank, and the regeneration process is continuous. During regeneration, the pH is generally maintained at 1.5 to 3.0, the temperature is about 30 ° C, air is continuously blown in, and an appropriate amount of the medium is added.

Second, the bacteria leaching process

The bacterial leaching process generally involves the following operations:

(1) Ore preparation work. The copper ore is ground to a certain particle size according to the characteristics of the ore and subsequent process requirements, and then piled into a heap or loaded into a leaching tank. If the method of in-situ leaching is adopted, it is necessary to select a liquid and a liquid collection method to excavate some grooves to facilitate the flow of the leaching agent and the leachate.

(2) Leaching. Bacterial leaching method is generally used to treat lean ore. The percolation method is usually used. According to specific conditions, heap leaching, tank leaching or in-situ leaching can be used, and the clarified liquid for subsequent treatment can be directly obtained. Some of the rich ore, etc. can also be stirred and leached by bacteria, and the leached slurry can be separated by solid-liquid separation to obtain a clear copper-containing leaching solution.

(3) Recycling of useful ingredients. From the leaching solution, copper can be used, such as iron replacement, precipitation-flotation or extraction-electrowinning.

The bacterial leaching process varies depending on the nature of the ore being processed, the method of treatment, and the requirements. Figure 1 illustrates the flow of a mixed ore that circulates copper using H. thermophilus.

Figure 1 Flow chart of leaching mixed ore with Thiobacillus ferrooxidans

Third, bacterial leaching production practice

A mine in China is a deposit of copper deposits, and the primary copper deposits are enriched by secondary percolation to form miners. The copper ore body is mainly composed of secondary copper sulfide. The secondary copper sulfide minerals mainly account for 79% of the copper ore, the primary copper sulfide accounts for 9%, and the copper oxide accounts for 12%. The gangue minerals are mainly quartz and feldspar .

The mine is immersed in a percolation tank using Thiobacillus ferrooxidans, and the production process is a bacterial leaching-extraction-electrowinning process. Production practice shows that about 50% of the copper leaching speed is faster, and the remaining 50% of the leaching speed is slower. In order to adapt to this feature, a large amount of liquid is used in the initial stage of leaching to accelerate the leaching. In the later stage of leaching, the method of leisure and tempering is used to accelerate the oxidation of copper sulphide minerals. At the same time, in order to meet the requirements of subsequent copper extraction, the leaching is reduced in the later stage of leaching. The acidity of the agent to increase the pH of the infusion. 9 percolation cycles were used to ensure that the copper content in the immersion liquid was relatively constant, the leaching period was 60-90 days, and the copper leaching rate was 79.5%, of which 42.9% of the original copper sulphide and 77.4% of the secondary copper sulphide. It is 93.6%.

The immersion liquid was filtered through clarified sand and subjected to four-stage reverse extraction with 7% N-510 No. 200 solvent oil solution, and the extraction rate was 85%. The copper content of the supported organic phase was 1.4 g/L, and the three-stage stripping was carried out using a waste electrolyte containing 200 g/L of sulfuric acid and 40 g/L of copper, and the stripping rate was 99%. Copper-rich liquid composition: copper 45g / L, sulfuric acid 200g / t, iron 6.5g / L.

In 8% of antimony-containing lead-antimony alloy is electrodeposition anode plate, stainless steel plate as the cathode, the cell voltage of 1.9 ~ 2.1V, a current density of 111A / m ^2, with the pole pitch of 100mm, copper rich solution flow rate of 5.6 L/min.

Since the leaching period is long and the leaching rate is low when the bacteria are leached, the promotion and application in production are limited. But for some poor ore, bacterial leaching still has its advantages.