JP2003073752A - Method for leaching pyrite containing chalcopyrite - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for leaching pyrite containing chalcopyrite, which can leach pyrite containing chalcopyrite with a bacterium, in a practically versatile condition. SOLUTION: The method for leaching pyrite containing chalcopyrite while employing an iron bacterium as the bacterium, is characterized by adding activated carbon with the above bacterium to leach.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for leaching a sulfide ore containing chalcopyrite, which is a major mineral of copper, into bacteria.

[0002]

2. Description of the Related Art In the case of obtaining copper (Cu) from an ore, the hydrometallurgical method requires less equipment investment and can be operated flexibly in comparison with the conventional dry metallurgical method, and the copper ingot can be directly produced at the mountainside. There are advantages such as copper oxide ore and secondary copper sulfide ore are applied, and as a method of sulfuric acid leaching, for example, chemical leaching performed by adjusting the ore grain size and temperature under sulfuric acid acidity, and iron oxidizing bacteria at room temperature Leaching with bacteria. Bacterial leaching has the advantage that it can be carried out at room temperature, compared to chemical leaching carried out at high temperatures.

As a copper resource, chalcopyrite is widely used, but in the leaching of chalcopyrite with bacteria, addition of bacteria accelerates the leaching rate.

[0004]

However, although the leaching rate is temporarily increased by the addition of bacteria, there is a problem that the leaching rate cannot be maintained and the reaction becomes stagnant while the copper leaching rate is low. This is because although the leaching rate is temporarily increased by the addition of bacteria, the generated sulfur or the like covers the surface of the chalcopyrite, so that the leaching rate cannot be maintained and the reaction occurs while the copper leaching rate is low. It is believed to be stagnant.

As a technique for improving such leaching of bacteria, a technique of adding silver ions as a reaction accelerator has been proposed (US Pat. No. 4,571,387). However, 100 to 4 silver ions are added per 1 kg of chalcopyrite.
Since 000 mg is added, there is a problem that the cost becomes high.

Further, there are many known techniques for oxidizing iron ions Fe ²⁺ by bacteria to circulate trivalent iron ions Fe ³⁺ for use in copper leaching (JP-A-51-9672).
7, JP-A-10-265864), and WO98.
/ 39491, trivalent iron ion Fe ³⁺ obtained by oxidizing divalent iron ion Fe ²⁺ in bacteria in a bath different from the leaching tank, or an oxidizing agent such as permanganate or hydrogen peroxide is used. Add redox potential to 350-450m
The technique of keeping it at V has been proposed. However,
The actual addition of Fe ³⁺ cannot keep the redox potential within a certain range, and there is a problem that leaching is delayed.

In view of such circumstances, the present invention provides a method of leaching chalcopyrite-containing sulfide ore capable of leaching bacteria in chalcopyrite-containing sulfide ore under practical conditions at a practical operation level. It is an issue.

[0008]

A first aspect of the present invention for solving the above-mentioned problems is a method of leaching a sulfide ore containing chalcopyrite by using iron-oxidizing bacteria as a bacterium. A method for leaching sulfide ore containing chalcopyrite is characterized by adding and leaching.

In the first aspect, the addition of activated carbon allows the leaching reaction to proceed rapidly and continuously without being lowered to the end.

A second aspect of the present invention is the method for leaching sulfide ore containing chalcopyrite according to the first aspect, characterized in that the natural potential of the activated carbon is larger than that of chalcopyrite and smaller than that of pyrite.

In the second aspect, by using a predetermined activated carbon, it is possible to effectively prevent deterioration of the leaching reaction.

In a third aspect of the present invention, in the first or second aspect, the amount of activated carbon added is such that the potential of pulp measured by a saturated calomel electrode due to leaching of chalcopyrite is prevented from changing to the oxidation side. The leaching method for sulfide ore containing chalcopyrite is characterized in that the temperature is maintained at 380 to 400 mV.

In the third aspect, the leaching reaction proceeds rapidly and continuously without lowering to the end, and the copper material can be effectively used.

The structure of the present invention will be described in more detail below.

When sulfide ore containing chalcopyrite (chemical formula: CuFeS ₂ ) is leached with sulfuric acid, the following reaction formulas (1) to (1)
When the reaction shown in (3) occurs and the reactions of (1) to (3) proceed in a well-balanced manner, the copper leaching rate becomes faster and the leaching proceeds continuously.

That is, in the leaching of chalcopyrite, Fe ³⁺ in the leachate acts on the chalcopyrite as an oxidizing agent, and Cu is leached according to the reaction formula (1).

Fe as an oxidizer in the formula (1)
³⁺ is supplied by oxidizing Fe ²⁺ by bacteria as represented by the reaction formula (2).

Further, S ^{0 and the} like produced by the Cu leaching reaction of the formula (1) are oxidized by the reaction formula of the (3), for example.

[0019]

Embedded image CuFeS ₂ + 4Fe ³⁺ → Cu ²⁺ + 5Fe ²⁺ + 2S ⁰ (1)

[0020]

Embedded image Fe ²⁺ + 1 / 2O ₂ + 2H ⁺ → Fe ³⁺ + H ₂ O (2)

[0021]

Embedded image S ⁰ + 3 / 2O ₂ + H ₂ O → H ₂ SO ₄ (3)

Here, in the case of leaching bacteria, (1)
The elemental sulfur produced by the reaction represented by the formula covers the surface of chalcopyrite, and the reaction of formula (3) is so slow that leaching stops, but activated carbon should be added as a reaction accelerator. According to the above, it was found that the reactions of (1) to (3) proceed in a well-balanced manner, probably because elemental sulfur is adsorbed on the activated carbon and the coating of chalcopyrite is prevented.

That is, in the present invention, leaching is performed by adding activated carbon together with bacteria.

Here, the activated carbon is generally used as an adsorbent, and is not particularly limited, but it is not necessary to use expensive palm shell activated carbon having a strong adsorbing power, and an inexpensive coal-based activated carbon is used. Is enough.

Further, it is particularly preferable to use activated carbon whose natural potential is larger than that of chalcopyrite and smaller than that of pyrite. That is, for example, it is preferable to use activated carbon that has a spontaneous potential higher than that of chalcopyrite and lower than that of pyrite in sulfuric acid having a pH of 1.5. This is because, in addition to the effect of the adsorption of sulfur by activated carbon as described above, the effect that the activated carbon and chalcopyrite come into contact with each other and thus chalcopyrite having a low natural potential is likely to leach out is presumed.

In other words, for example, Fe of pH 1.5
^It is preferable to use activated carbon having a reducing power of Fe ^{3+ in} a ³⁺ solution. Or, for example, Fe ^{2+ having} a pH of 1.5
It is preferable to use activated carbon which has an oxidative power of Fe ^{2+ in} the above solution, but has a weak oxidative power.

The amount of activated carbon added is not particularly limited, but it is preferable to maintain the pulp potential (hereinafter referred to as "oxidation-reduction potential") measured with a saturated calomel electrode at 380 to 400 mV. This is because the redox potential of the solution changes with the addition of activated carbon, but in the leaching of copper, the leaching efficiency is good when the redox potential is maintained at 380 to 400 mV. Generally, for example, 1t of leaching ore
Is about 20 to 400 kg.

The particle size of the activated carbon is, for example, about 0.6 mm or less, and the smaller the particle size, the better.

As the above-mentioned copper leaching reactions (1) to (3) proceed, the redox potential increases, but the redox potential and the copper leaching amount are 380 and 380 as shown in FIG.
The amount of copper leaching becomes maximum at about 400 mV.

In this way, it is possible to prevent the redox potential from changing to the oxidation side due to the leaching of chalcopyrite.
Copper can be effectively leached by adding activated carbon to the extent that V is maintained.

On the other hand, the bacterium used in the present invention is an iron-oxidizing bacterium which has been conventionally used for leaching bacteria, and is not particularly limited. Of course, it is preferable to use the acclimated one or bacteria existing in the same environment, and generally, the one acclimated with a sulfide ore containing chalcopyrite is used.

The amount of bacteria to be added is not particularly limited, and is generally 10 ⁶ to 10 ⁷ cells / mL.

Other leaching conditions may be the same as in the conventional bacterium leaching, but the pH is such that Fe ³⁺ does not precipitate,
It is a range in which iron oxidation by bacteria is possible, for example, pH 1 to
4 and the temperature is, for example, 20 to 40 ° C.

The sulfide ore used as a raw material is a sulfide ore containing chalcopyrite, but it is not necessary to concentrate it in order to increase the content of chalcopyrite. The ore grain size may be the same as the concentrate grain size obtained by flotation, but may be used after re-grinding if necessary. Of course, it is also possible to use one having a high copper grade, but it is also possible to use a complex sulfide ore of about 5 to 10%.

The amount of the raw material added is, for example, the amount of copper leached per day of 300 mg / L, and the amount of copper whose leaching is completed in 15 to 17 days. That is, for example, it is preferable to adjust the copper grade and pulp concentration of the concentrate so that the amount of copper metal is 4 to 5 g / L.

According to the method of the present invention, the low copper grade is 5 to 1.
Copper can be leached at 300 to 500 mg / L / day even with 0% concentrate.

An example of hydrometallurgy to which the leaching method of the present invention can be applied is shown in FIG.

As shown in FIG. 2, first, an ore 1 such as a beneficiated waste or a low-grade ore is crushed if necessary (step S1), crushed (step S2), and then floated (step S3). As a result, the waste 2 and the froth 3 are separated. Next, after re-milling the floss 3 (step S4),
After performing the leaching of the present invention (step S5), the leaching solution is filtered (step S6) to separate the filtrate 4 and the residue 5. Next, the filtrate 4 is solvent-extracted (step S7), stripped (step S8), and electrolytically collected (step S9) to obtain electrolytic copper 6. A part of the raffinate 7 of the solvent extraction (step S7) is returned to the leaching step (step S5), the rest is oxidized by bacteria (step S10), and then the pH is adjusted to about pH 4 (step S11) and filtered. By (step S12), the iron cake 8 is obtained. This filtration (step S12)
The pH of the filtrate 9 is adjusted again to about pH 10 (step S
13) and filter (step S14). The residue is the zinc cake 10 which is a solid deposit, and the filtrate 11 is neutralized by the pH adjustment (step S15) to form the waste liquid 12.

[0039]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in more detail based on Examples and Comparative Examples.

(Example 1) The ore used for leaching is a sulfide ore concentrate containing chalcopyrite obtained by flotation of a beneficiated slag of the Jezkent mine, Republic of Kazakhstan. The quality of the concentrate is Cu5
%, Zn 3%, Fe 33%, and the copper in the concentrate exists in the form of chalcopyrite. The bacterium used in the test was an iron-oxidizing bacterium collected from the mine of the Jezkent Mine, Republic of Kazakhstan. After culturing at 9K, the sulfide ore concentrate containing copper and pH 1.5 containing ammonium sulfate and dipotassium hydrogen phosphate. Bacteria cultured in sulfuric acid were used.

0.5 g of concentrate in 45 mL of sulfuric acid of pH 1.5
And bacterial cell suspension 5mL (10 ⁸ cells / mL)
In the examples, activated carbon A was added to the mixture of
1g was added. The additive used had a particle size of 0.6 mm or less. Shake and stir at a temperature of 30 ° C,
Leaching was done.

Comparative Examples 1 to 5 For comparison, the same procedure as in Example 1 was carried out except that 1 g of activated carbon B, graphite, coke, diatomaceous earth, and zeolite were used instead of activated carbon A.

Test Example 1 For Example 1 and Comparative Examples 1 to 5, the amount of copper leached in the solution was measured 6 days after the start of leaching. The measurement result is shown in FIG.

As a result, it was found that activated carbon A (details of which will be described later) has a copper leaching promoting effect as compared with activated carbon B, graphite, coke, diatomaceous earth and zeolite.

For comparison, a similar addition test was performed on coal, charcoal, carbon black, etc. instead of activated carbon A, but coal and charcoal had almost no effect of promoting copper leaching. Although carbon black was found to have a copper leaching promoting effect, it was less effective than activated carbon A.

(Example 2) The ore used for leaching was Example 1
Chloride-containing sulfide ore (Cu6
%, Zn 7%, Fe 26%), and the iron-oxidizing bacteria used are the same as in Example 1.

90 mL of sulfuric acid of pH 1.5 containing 3 g / L of ammonium sulfate and 0.5 g / L of dipotassium hydrogen phosphate
5g of sulfide ore concentrate containing chalcopyrite and 10mL of cell suspension
Was added. To this, 2 g of activated carbon A, which was found to have the effect of promoting copper leaching in Example 1, was adjusted to 0.6 mm or less and added. The temperature was 30 ° C., and leaching was carried out by mechanical stirring with an impeller.

(Comparative Example 6) Leaching was performed in the same manner as in Example 2 except that activated carbon was not used.

Test Example 2 The copper leaching rate was measured for Example 2 and Comparative Example 6. The measurement result is shown in FIG.

As a result, in Comparative Example 6, 30% in 14 days
Leach a small amount of copper, but after that, leaching stagnates, and
Although only 40% was leached after the day, in the example in which the activated carbon A was added, almost 100% of copper was leached in 16 days, which indicates that the activated carbon A promotes the copper leaching. When the ore collected during the leaching was observed with an optical microscope or a scanning electron microscope (SEM), it was observed that the activated carbon A was selectively attached to the chalcopyrite. It is considered that this is because activated carbon adsorbs the sulfur produced by the reaction.

(Test Example 3) Chalcopyrite, pyrite, sphalerite,
The electrodes of activated carbons A and B were prepared and the spontaneous potential was measured. The ores whose potentials were measured are crystals of chalcopyrite from the Toyoha mine, Hokkaido, pyrite from the Wansara mine, Peru, and sphalerite from the Kamioka mine, Gifu prefecture.

As the activated carbon, activated carbon A which was found to promote copper leaching in Examples 1 and 2 was used as a comparison, and activated carbon B which was used in Comparative Example 2 and had a low promoting effect was used.

These ores and activated carbon have a thickness of 0.3 m.
Shaped on a mirror-finished chip of about m, 10 mm
It was fixed to the tip of the φ glass tube with a lake material. A copper wire and a sample were connected with a conductive silver paste, and the wire was fixed with a resin to form an electrode. Using the electrodes created in this way,
The potential was measured in an iron-free 9K medium at pH 1.5. A silver chloride electrode was used as a reference electrode. Table 1 shows the results of measuring the self-potential.

[0054]

[Table 1]

Generally, when a substance having a low spontaneous potential and a substance having a high spontaneous potential coexist, it is considered that a substance having a low potential is easily leached,
It is known that the potential increases in the order of sphalerite, chalcopyrite, and pyrite, which was also confirmed by this measurement result. The spontaneous potential of activated carbon A, which had the leaching promoting effect in Examples 1 and 2, was
It was found to be located between chalcopyrite and pyrite. On the other hand, it was confirmed that the spontaneous potential of activated carbon B having a low leaching promoting effect as a comparison was higher than that of pyrite.

From this, it was found that it is preferable to use, as the additive, activated carbon having a spontaneous potential larger than that of chalcopyrite and smaller than that of chalcopyrite in pH 1.5 sulfuric acid.

(Example 3) The ore used for leaching is a sulfide ore concentrate containing chalcopyrite obtained by flotation of a beneficiated slag of the Jezkent mine, Republic of Kazakhstan. Cu 10%, Zn 6%, F
e 37%. The bacterium used was an iron-oxidizing bacterium collected from the mine of the Jezkent mine, Republic of Kazakhstan, and cultivated by the same method as in Example 1.

[0058] about ore leaching vessel of 5 m ³ 200 kg, water 3.5 m ³ and the cell suspension 0.4 m ³ was added and the pH1.5 with sulfuric acid. 50% pass size P ₅₀ is 20 μm
12 kg of activated carbon having a particle size of was added and leaching was performed at a temperature of 35 ° C. The impeller was stirred at 70 rpm and the circulation pump was operated to prevent the ore from stagnation in the spigot pipe. FIG. 5 shows the results of measuring the copper leaching rate.

Copper was leached at 5 g / L in 16 days from the start of leaching. Until the 12th day, the leaching rate was rather slow, the copper leaching amount was about 270 mg / L per day, and the redox potential was 380 mV or less. Redox potential is 380-400
The leaching amount was 500 mg / L or more per day for 12 to 15 days in the range of mV. Furthermore, it was found that almost no copper was leached during 15 to 16 days when the oxidation-reduction potential increased above 400 mV.

[0060]

As described above, in the bacterial leaching of sulfide ore containing chalcopyrite, by adding activated carbon, the leaching of sulfide ore containing chalcopyrite can be carried out under conditions that are versatile at the actual operation level. There is an effect that can be.

[Brief description of drawings]

FIG. 1 is a diagram showing a relationship between a redox potential and a copper leaching amount.

FIG. 2 is a diagram showing an example of hydrometallurgy to which the leaching method of the present invention can be applied.

FIG. 3 is a diagram showing the results of Test Example 1.

FIG. 4 is a diagram showing the results of Test Example 2;

FIG. 5 is a diagram showing measurement results of Example 3.

Claims (3)

[Claims] 1. A method for leaching a sulfide ore containing chalcopyrite by using iron-oxidizing bacteria as a bacterium, wherein leaching is performed by adding activated carbon together with the bacterium to obtain a sulfide ore containing chalcopyrite. Leaching method. 2. The leaching method of sulfide ore containing chalcopyrite according to claim 1, wherein the natural potential of the activated carbon is larger than that of chalcopyrite and smaller than that of chalcopyrite. 3. The addition amount of the activated carbon according to claim 1, wherein the pulp potential measured by a saturated calomel electrode due to the leaching of chalcopyrite is suppressed to 380.
A method for leaching a sulfide ore containing chalcopyrite, which is characterized in that the voltage is maintained at about 400 mV.