A method for reducing the passivation effect on the surface of low-grade chalcocite using l-ascorbic acid
By using L-ascorbic acid reducing agent to regulate pH and Eh values during the bioleaching process of chalcocite, and combining it with acidophilic bacterial strains, the passivation problem caused by pyrite hydrolysis was solved, and efficient copper mineral leaching was achieved.
Patent Information
- Application Number
- CN202310611776.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- Filing Date
- 2023-05-29
- Publication Date
- 2026-02-17
- Estimated Expiration
- 2043-05-29
AI Technical Summary
During the bioleaching of chalcocite, the hydrolysis of pyrite leads to the consumption of oxidant by Fe3+, which reduces the Fe2+ concentration, affects microbial activity, and generates ferruginous substances that passivate the copper ore surface, thus reducing the copper dissolution rate.
L-ascorbic acid reducing agent was used to control the pH and Eh values in the leaching system. By reducing Fe3+ to Fe2+, the formation of iron alum was reduced and the leaching reaction was promoted. A mixed strain of acidophilic ferrooxidizing thiobacillus, ferrooxidizing Leptospira, and acidophilic iron protoplasm was used for bioleaching.
It significantly improves the leaching efficiency of chalcocite, with a copper leaching rate of up to 96%. The process is simple, the equipment is basic, and the energy consumption is low.
Smart Images
Figure CN116640925B_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The present application belongs to the technical field of bio-metallurgy, and particularly relates to a method for weakening the passivation effect on the surface of chalcocite by using L-ascorbic acid. BACKGROUND
[0002] Pyrite is a common associated gangue mineral in the process of bioleaching of chalcocite. In a complex leaching system, Fe 3+ generated by the dissolution of pyrite will undergo a hydrolysis reaction to generate different forms of precipitates, which will cause the pH value in the leaching system to change. In the process of bioleaching, the hydrolysis reaction will consume the oxidant Fe 3+ required for the oxidation of sulfide ore, thereby reducing the concentration of Fe 2+ , the energy substance of microorganisms, and affecting the growth activity of microorganisms; at the same time, the precipitates such as jarosite generated by the hydrolysis of Fe 3+ will also adhere to the surface of copper sulfide, thereby reducing the dissolution rate of copper, i.e., the passivation effect in the process of bioleaching of copper ore.
[0003] It has been found by relevant personnel that the passivation effect on the surface of ore in the process of bioleaching of chalcocite is closely related to the Eh value in the leaching system. In the process of bioleaching of copper ore, the main influencing factors of the Eh value are the concentrations of Fe 3+ and Fe 2+ . Therefore, a reducing agent can be added to the leaching system, so that a large amount of Fe 3+ in the leaching system is reduced to Fe 2+ , and the reduced Fe 2+ can continue to serve as the energy substance of bacteria, and Fe 3+ continues to oxidize chalcocite; in addition, the generation of jarosite can be reduced, the passivation effect on the surface of copper ore is weakened, and the leaching reaction is promoted, thereby improving the leaching rate of chalcocite.
[0004] Therefore, the applicant proposes a method for weakening the passivation effect on the surface of chalcocite by adding L-ascorbic acid reducing agent, which promotes the reduction of Fe 3+ in the leaching system to Fe 2+ by adding L-ascorbic acid reducing agent in the middle of bioleaching, and reduces the generation of jarosite passivation. The present application has important significance for improving the bioleaching rate of chalcocite. SUMMARY
[0005] The purpose of the present application is to improve the leaching efficiency of chalcocite, and a method for weakening the passivation effect on the surface of chalcocite by using L-ascorbic acid is proposed, which can significantly improve the leaching efficiency of chalcocite.
[0006] To achieve the above-mentioned purpose, the present application adopts the following technical solutions:
[0007] A method for reducing the passivation effect on the surface of low-grade chalcocite using L-ascorbic acid involves using a mixed strain of *Acidobacterium ferrooxidans*, *Leptospira ferrooxidans*, and *Plasmodium ferrooxidans*, acclimated to pure chalcocite minerals, as the leaching strain for bioleaching of low-grade chalcocite. During the leaching process, the pH and Eh values of the leaching system are monitored and measured every 24 hours. When the pH value exceeds 1.90±0.05, sulfuric acid is added to lower the pH to 1.90±0.05. When the Eh value exceeds 500±5 mV, L-ascorbic acid is added to lower the Eh value to 500±5 mV. The leaching cycle is 20 days. Ultimately, this method utilizes L-ascorbic acid to reduce the passivation effect on the surface of low-grade chalcocite and improve the bioleaching efficiency of low-grade chalcocite.
[0008] The above-mentioned method for reducing the passivation effect on the surface of low-grade chalcocite using L-ascorbic acid specifically includes the following steps:
[0009] (1) Prepare low-grade chalcocite into powder with a particle size ≤74μm;
[0010] (2) Inoculate 10 mL of the iron bacteria mixed culture into 90 mL of 9K medium, adjust the pH to 1.8 with sulfuric acid solution, and place it in a constant temperature shaking incubator at 30℃ and 150 r / min for shaking culture. Subculture every 6 days at an inoculum size of 10 vol%. Subculture is stopped when the color of the culture medium changes from light green to reddish brown, thus obtaining the subcultured bacterial culture; wherein, the iron bacteria mixed culture consists of 1×10 7 CFU / mL Acidophilus ferrooxidans, 1×10 6 CFU / mL ferrous oxide Leptospira and 1×10 4 Composition of CFU / mL of acidophilic iron protoplasm;
[0011] (3) Take 10 mL of the subcultured bacterial solution obtained in step (2) and place it in a 250 mL Erlenmeyer flask. Place it in a constant temperature shaking incubator at 30℃ and 150 r / min and shake it. When the bacteria grow to the logarithmic phase, add 90 mL of iron-free 9K medium and 1.0 g of pure chalcocite mineral. Continue to culture until the culture solution turns reddish-brown to obtain the first acclimatization bacterial solution. Take 10 mL of the first acclimatization bacterial solution and place it in a 250 mL Erlenmeyer flask. Place it in a constant temperature shaking incubator at 30℃ and 150 r / min and shake it. When the bacteria grow to the logarithmic phase, add 90 mL of iron-free 9K medium and 1.0 g of pure chalcocite mineral. Continue to culture until the culture solution turns reddish-brown to obtain the second acclimatization bacterial solution.
[0012] (4) Add 2-3g of low-grade chalcocite powder obtained in step (1), 10mL of secondary acclimatization bacterial solution obtained in step (3) and 90mL of iron-free 9K medium to a 250mL conical flask. After mixing, place the flask in a constant temperature shaking incubator at 40±5℃ and 180±10r / min for biological shaking leaching. The entire leaching cycle is 20 days. During the leaching process, the pH and Eh values of the leaching system are monitored and measured every 24 hours. When the pH value of the leaching system exceeds 1.90±0.05, sulfuric acid solution is added to lower the pH value to 1.90±0.05. When the Eh value of the leaching system exceeds 500±5mV, L-ascorbic acid solution is added to lower the Eh value to 500±5mV.
[0013] The Cu grade of the low-grade chalcocite is 0.30% ± 0.05%.
[0014] The 9K culture medium is formulated as follows: Solution A: 3.0 g / L (NH)₂SO₄, 0.5 g / L K₂HPO₄, 0.1 g / L KCl, 0.5 g / L MgSO₄·7H₂O, 0.01 g / L Ca(NO₃)₂, 800 mL deionized water, pH adjusted to 2.0, autoclaved at 121℃ for 20 min; Solution B: 44.3 g / L FeSO₄·7H₂O, 200 mL deionized water, pH adjusted to 2.0, sterilized by filtration through a 0.22 μm filter membrane; the sterilized 800 mL Solution A is mixed with 200 mL Solution B and then dispensed.
[0015] The iron-free 9K culture medium is formulated as follows: 3.0 g / L (NH)2SO4, 0.5 g / L K2HPO4, 0.1 g / L KCl, 0.5 g / L MgSO4·7H2O, 0.01 g / L Ca(NO3)2, 100 mL deionized water, pH adjusted to 2.0, and autoclaved at 121℃ for 20 min.
[0016] The concentration of the sulfuric acid solution is 50% v / v;
[0017] The concentration of the L-ascorbic acid solution is 100 g / L.
[0018] The above-mentioned method of using L-ascorbic acid to reduce the passivation effect on the surface of low-grade chalcocite is applied to the bioleaching of low-grade chalcocite.
[0019] The significant advantages of this invention are:
[0020] The present invention has a short process flow, simple operation, simple equipment, and low energy consumption, which can significantly improve the bioleaching rate of chalcocite. It has been measured that after leaching for 20 days, the Cu leaching rate can reach up to 96%. Attached Figure Description
[0021] Figure 1 This is a process flow diagram of the present invention.
[0022] Figure 2 This refers to the pH measurement value of this invention.
[0023] Figure 3 The Eh measurement value is for this invention.
[0024] Figure 4 This is a diagram showing the copper leaching rate of the present invention. Detailed Implementation
[0025] To make the content of this invention easier to understand, the technical solution of this invention will be further described below with reference to specific embodiments, but this invention is not limited thereto.
[0026] In this invention, the 9K culture medium formula is as follows: Solution A (g / L): 3.0 g / L (NH)₂SO₄, 0.5 g / L K₂HPO₄, 0.1 g / L KCl, 0.5 g / L MgSO₄·7H₂O, 0.01 g / L Ca(NO₃)₂, 800 mL deionized water, pH adjusted to 2.0, autoclaved at 121℃ for 20 min; Solution B: 44.3 g / L FeSO₄·7H₂O, 200 mL deionized water, pH adjusted to 2.0, sterilized by filtration through a 0.22 μm filter membrane; the sterilized 800 mL Solution A and 200 mL Solution B are mixed and dispensed.
[0027] In this invention, the iron-free 9K culture medium is formulated as follows: 3.0 g / L (NH)2SO4, 0.5 g / L K2HPO4, 0.1 g / L KCl, 0.5 g / L MgSO4·7H2O, 0.01 g / L Ca(NO3)2, 1000 mL deionized water, pH adjusted to 2.0, and autoclaved at 121°C for 20 min.
[0028] In this invention, the multi-element analysis results and copper chemical phase analysis results of the low-grade chalcocite are listed in Tables 1 and 2.
[0029] Table 1. Multi-element analysis results (%) of low-grade chalcocite.
[0030] Component Cu S TFe As Pb Al2O3 SiO2 CaO MgO K2O Na2O Zn Content 0.30 5.03 4.23 0.074 0.079 12.34 76.66 0.13 0.01 1.05 0.087 0.01
[0031] Table 2. Copper chemical phase analysis results (%) of low-grade chalcocite.
[0032]
[0033]
[0034] In this invention, the multi-element analysis results of the pure chalcocite mineral are listed in Table 3.
[0035] Table 3. Multi-element analysis results of pure chalcocite minerals
[0036]
[0037] In this invention, there are no special restrictions on the source of the three iron bacteria, namely, *Acidithiobacillus ferrooxidans*, *Leptospira ferrooxidans*, and *Acidithiobacillus ferrooxidans*. Any source of iron bacteria well known in the art can be used. Specifically, the three iron bacteria in the embodiments of this invention were isolated from the acidic pit water of the Zijinshan sulfide mine in Longyan City, Fujian Province.
[0038] In this invention, pH value was measured using an Ohaus ST3100 acidity meter, Eh value was measured using a METTLER TOLEDO potentiometer, and copper and iron content was measured using an iCAP7400 inductively coupled plasma atomic emission spectrometer.
[0039] Experimental group 1
[0040] A method for reducing the passivation effect on the surface of low-grade chalcocite is carried out according to the following steps:
[0041] (1) Low-grade chalcocite was crushed, ground, and classified to produce powder with a particle size ≤74μm. A representative sample was quantitatively analyzed and the Cu grade was 0.30%.
[0042] (2) Inoculate 10 mL of the iron bacteria mixed culture into 90 mL of 9K medium, adjust the pH to 1.8 with 50% (v / v) sulfuric acid solution, and place in a constant temperature shaking incubator at 30℃ and 150 r / min. Subculture every 6 days at an inoculum size of 10 vol%. Stop subculturing when the color of the culture medium changes from light green to reddish brown to obtain the subcultured culture medium; the iron bacteria mixed culture medium is composed of 1×10 7 CFU / mL Acidophilus ferrooxidans, 1×10 6 CFU / mL ferrous oxide Leptospira and 1×10 4 Composition of CFU / mL of acidophilic iron protoplasm;
[0043] (3) Take 10 mL of the passaged bacterial culture obtained in step (2) and place it in a 250 mL Erlenmeyer flask. Place the flask in a constant temperature shaking incubator at 30℃ and 150 r / min and shake. When the bacteria reach the logarithmic growth phase, add 90 mL of iron-free 9K medium and 1.0 g of chalcocite mineral. Continue culturing for about 6 days until the culture medium turns reddish-brown to obtain the first acclimatization bacterial culture. Take 10 mL of the first acclimatization bacterial culture and place it in a 250 mL Erlenmeyer flask. Place the flask in a constant temperature shaking incubator at 30℃ and 150 r / min and shake. When the bacteria reach the logarithmic growth phase, add 90 mL of iron-free 9K medium and 1.0 g of chalcocite mineral. Continue culturing for about 6 days until the culture medium turns reddish-brown to obtain the second acclimatization bacterial culture. The second acclimatization bacterial culture was found to contain 1 × 10⁻⁶ Acidophilus ferrooxidans. 8 CFU / mL, ferrous oxide Leptospira 1×10 7 CFU / mL, Acidophilus iron protease 1×10 5 CFU / mL;
[0044] (4) Add 2-3g of the low-grade chalcocite powder obtained in step (1), 10mL of the secondary acclimatization bacterial solution obtained in step (3), and 90mL of iron-free 9K medium to a 250mL conical flask. Place the flask in a constant temperature shaking incubator at 40±5℃ and 180±10r / min for biological shaking leaching. Monitor the pH and Eh values of the leaching system in real time. The entire leaching cycle is 20 days.
[0045] (6) After leaching, the leaching system was subjected to solid-liquid separation to obtain leaching solution and leaching residue. ICP detection was performed, and the Cu leaching rate was calculated to be 66%.
[0046] Experimental group 2
[0047] A method for reducing the passivation effect on the surface of low-grade chalcocite is carried out according to the following steps:
[0048] (1) Low-grade chalcocite was crushed, ground and classified to obtain powder with a particle size ≤74μm. The representative sample was quantitatively analyzed and the Cu grade was 0.30%.
[0049] (2) Inoculate 10 mL of the iron bacteria mixed culture into 90 mL of 9K medium, adjust the pH to 1.8 with 50% (v / v) sulfuric acid solution, and place in a constant temperature shaking incubator at 30℃ and 150 r / min. Subculture every 6 days at an inoculum size of 10 vol%. Stop subculturing when the color of the culture medium changes from light green to reddish brown to obtain the subcultured culture medium; the iron bacteria mixed culture medium is composed of 1×10 7 CFU / mL Acidophilus ferrooxidans, 1×10 6 CFU / mL ferrous oxide Leptospira and 1×104 Composition of CFU / mL of acidophilic iron protoplasm;
[0050] (3) Take 10 mL of the passaged bacterial culture obtained in step (2) and place it in a 250 mL Erlenmeyer flask. Place the flask in a constant temperature shaking incubator at 30℃ and 150 r / min and shake. When the bacteria reach the logarithmic growth phase, add 90 mL of iron-free 9K medium and 1.0 g of chalcocite mineral. Continue culturing for about 6 days until the culture medium turns reddish-brown to obtain the first acclimatization bacterial culture. Take 10 mL of the first acclimatization bacterial culture and place it in a 250 mL Erlenmeyer flask. Place the flask in a constant temperature shaking incubator at 30℃ and 150 r / min and shake. When the bacteria reach the logarithmic growth phase, add 90 mL of iron-free 9K medium and 1.0 g of chalcocite mineral. Continue culturing for about 6 days until the culture medium turns reddish-brown to obtain the second acclimatization bacterial culture. The second acclimatization bacterial culture was found to contain 1 × 10⁻⁶ Acidophilus ferrooxidans. 8 CFU / mL, ferrous oxide Leptospira 1×10 7 CFU / mL, Acidophilus iron protease 1×10 5 CFU / mL.
[0051] (4) Add 2-3g of the low-grade chalcocite powder obtained in step (1), 10mL of the secondary acclimatization bacterial solution obtained in step (3), and 90mL of iron-free 9K medium to a 250mL conical flask. Place the flask in a constant temperature shaking incubator at 40±5℃ and 180±10r / min for biological shaking leaching. Monitor the pH and Eh values of the leaching system in real time. The entire leaching cycle is 20 days. During the leaching process, monitor the pH and Eh values of the leaching system and measure them every 24 hours. After each measurement, when the pH value of the leaching system exceeds 1.90±0.05, adjust the pH value with 50% (v / v) sulfuric acid to control the pH value at 1.90±0.05.
[0052] (5) After leaching, the leaching system was subjected to solid-liquid separation to obtain leachate and leaching residue. ICP detection was performed, and the Cu leaching rate was calculated to be 75%.
[0053] Experimental group 3
[0054] A method for reducing the passivation effect on the surface of low-grade chalcocite using L-ascorbic acid is carried out according to the following steps:
[0055] (1) Low-grade chalcocite was crushed, ground and classified to obtain powder with a particle size ≤74μm. The representative sample was quantitatively analyzed and the Cu grade was 0.30%.
[0056] (2) Inoculate 10 mL of the iron bacteria mixed culture into 90 mL of 9K medium, adjust the pH to 1.8 with 50% (v / v) sulfuric acid solution, and place in a constant temperature shaking incubator at 30℃ and 150 r / min. Subculture every 6 days at an inoculum size of 10 vol%. Stop subculturing when the color of the culture medium changes from light green to reddish brown to obtain the subcultured culture medium; the iron bacteria mixed culture medium is composed of 1×10 7 CFU / mL Acidophilus ferrooxidans, 1×10 6 CFU / mL ferrous oxide Leptospira and 1×10 4 Composition of CFU / mL of acidophilic iron protoplasm;
[0057] (3) Take 10 mL of the passaged bacterial culture obtained in step (2) and place it in a 250 mL Erlenmeyer flask. Place the flask in a constant temperature shaking incubator at 30℃ and 150 r / min and shake. When the bacteria reach the logarithmic growth phase, add 90 mL of iron-free 9K medium and 1.0 g of chalcocite mineral. Continue culturing for about 6 days until the culture medium turns reddish-brown to obtain the first acclimatization bacterial culture. Take 10 mL of the first acclimatization bacterial culture and place it in a 250 mL Erlenmeyer flask. Place the flask in a constant temperature shaking incubator at 30℃ and 150 r / min and shake. When the bacteria reach the logarithmic growth phase, add 90 mL of iron-free 9K medium and 1.0 g of chalcocite mineral. Continue culturing for about 6 days until the culture medium turns reddish-brown to obtain the second acclimatization bacterial culture. The second acclimatization bacterial culture was found to contain 1 × 10⁻⁶ Acidophilus ferrooxidans. 8 CFU / mL, ferrous oxide Leptospira 1×10 7 CFU / mL, Acidophilus iron protease 1×10 5 CFU / mL.
[0058] (4) Add 2-3g of the low-grade chalcocite powder obtained in step (1), 10mL of the secondary acclimatization bacterial solution obtained in step (3) and 90mL of iron-free 9K medium to a 250mL conical flask. Place the flask in a constant temperature shaking incubator at 40±5℃ and 180±10r / min for biological shaking leaching. The entire leaching cycle is 20 days. During the leaching process, the pH and Eh values of the leaching system are monitored and measured every 24 hours. After each measurement, when the pH value of the leaching system exceeds 1.90±0.05, the pH value is reduced to 1.90±0.05 with 50% (v / v) sulfuric acid solution. When the Eh value of the leaching system exceeds 500±5mV, the Eh value is reduced to 500±5mV with 100g / L L-ascorbic acid solution.
[0059] (5) After leaching, the leaching system was subjected to solid-liquid separation to obtain leachate and leaching residue. ICP detection was performed, and the Cu leaching rate was calculated to be 96%.
[0060] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made within the scope of the claims of the present invention should be included in the scope of the present invention.
Claims
1. A method for reducing the passivation effect on the surface of low-grade chalcocite using L-ascorbic acid, characterized in that: A mixed strain of *Acidithiobacillus ferrooxidans*, *Leptospira ferrooxidans*, and *Plasmodium ferrooxidans*, domesticated with pure chalcocite minerals, was used as the leaching strain for bioleaching of low-grade chalcocite. During the leaching process, the pH and Eh values of the leaching system were monitored and measured every 24 hours. When the pH value exceeded 1.90±0.05, sulfuric acid was added to lower the pH to 1.90±0.
05. When the Eh value exceeded 500±5 mV, L-ascorbic acid was added to lower the Eh value to 500±5 mV. The leaching cycle was 20 days. Ultimately, L-ascorbic acid was used to reduce the surface passivation effect of low-grade chalcocite and improve the bioleaching efficiency of low-grade chalcocite. The method includes the following steps: (1) Prepare low-grade chalcocite into powder with a particle size ≤74μm; (2) Inoculate 10 mL of the iron bacteria mixed culture into 90 mL of 9K medium, adjust the pH to 1.8 with sulfuric acid solution, and place it in a constant temperature shaking incubator at 30℃ and 150 r / min for shaking culture. Subculture once every 6 days at an inoculum of 10 vol%. Subculture is stopped when the color of the culture medium changes from light green to reddish brown to obtain the subcultured culture medium; wherein, the iron bacteria mixed culture medium consists of 1×10 7 CFU / mL Acidophilus ferrooxidans, 1×10 6 CFU / mL ferrous oxide Leptospira and 1×10 4 Composition of CFU / mL of acidophilic iron protoplasm; (3) Take 10 mL of the subcultured bacterial solution obtained in step (2) and place it in a 250 mL Erlenmeyer flask. Place it in a constant temperature shaking incubator at 30℃ and 150 r / min and shake it. When the bacteria grow to the logarithmic phase, add 90 mL of iron-free 9K medium and 1.0 g of pure chalcocite mineral. Continue to culture until the culture solution turns reddish-brown to obtain the first acclimatization bacterial solution. Take 10 mL of the first acclimatization bacterial solution and place it in a 250 mL Erlenmeyer flask. Place it in a constant temperature shaking incubator at 30℃ and 150 r / min and shake it. When the bacteria grow to the logarithmic phase, add 90 mL of iron-free 9K medium and 1.0 g of pure chalcocite mineral. Continue to culture until the culture solution turns reddish-brown to obtain the second acclimatization bacterial solution. (4) Add 2~3g of low-grade chalcocite powder obtained in step (1), 10mL of secondary acclimatization bacterial solution obtained in step (3) and 90mL of iron-free 9K medium to a 250mL conical flask. After mixing, place the flask in a constant temperature shaking incubator at 40±5℃ and 180±10r / min for biological shaking leaching. The entire leaching cycle is 20 days. During the leaching process, the pH and Eh values of the leaching system are monitored and measured every 24 hours. When the pH value of the leaching system exceeds 1.90±0.05, sulfuric acid solution is added to lower the pH value to 1.90±0.
05. When the Eh value of the leaching system exceeds 500±5mV, L-ascorbic acid solution is added to lower the Eh value to 500±5mV.
2. The method according to claim 1, characterized in that: The Cu grade of the low-grade chalcocite is 0.30% ± 0.05%.
3. The method according to claim 2, characterized in that: The formulation of the 9K medium is as follows: Solution A: 3.0 g / L (NH4)2SO4, 0.5 g / L K2HPO4, 0.1 g / L KCl, 0.5 g / L MgSO4·7H2O, 0.01 g / L Ca(NO3)2, 800 mL deionized water, adjust the pH to 2.0, and autoclave at 121℃ for 20 min; Solution B: FeSO4·7H2O 44.3g / L, deionized water 200mL, pH adjusted to 2.0, sterilized by filtration through a 0.22μm filter membrane; mix 800mL of sterilized solution A with 200mL of solution B and dispense.
4. The method according to claim 1, characterized in that: The iron-free 9K culture medium is formulated as follows: 3.0 g / L (NH4)2SO4, 0.5 g / L K2HPO4, 0.1 g / L KCl, 0.5 g / L MgSO4·7H2O, 0.01 g / L Ca(NO3)2, 100 mL deionized water, pH adjusted to 2.0, and autoclaved at 121℃ for 20 min.
5. The method according to claim 1, characterized in that: The concentration of the sulfuric acid solution is 50% v / v.
6. The method according to claim 1, characterized in that: The concentration of the L-ascorbic acid solution is 100 g / L.
7. The application of the method as described in claim 1 in the bioleaching of low-grade chalcocite.