Method for regulating and controlling oxidation-reduction potential and free radical effect based on oxygen environment to reinforce bioleaching of chalcopyrite

Abstract

The invention discloses a method for regulating and controlling oxidation-reduction potential and free radical effect based on an oxygen environment to strengthen chalcopyrite bioleaching, and belongs to the technical field of biological metallurgy. In the microbiological leaching process of the chalcopyrite, the oxidation-reduction potential of a leaching system is regulated and controlled within the range of 410 mV to 480 mV by alternately providing an oxygen-enriched environment and an oxygen-deficient environment, so that selective leaching of copper is enhanced; according to the method, the oxygen-enriched environment is used for promoting generation of free radicals and enhancing oxidation leaching of copper, the oxygen-deficient environment is used for inhibiting oxidation of iron, and selective dissolution of copper is enhanced through microbial anaerobic sulfur oxidation and iron reduction, so that the reaction rate and selectivity in the leaching process can be further optimized; and meanwhile, rapid formation of passive films (jarosite and the like) can be avoided by regulating and controlling the oxidation-reduction potential, the leaching efficiency of the chalcopyrite is improved, and the method is low in cost, easy to operate, free of secondary pollution and capable of being applied and popularized.

Description

Technical Field

[0001] The invention relates to a chalcopyrite leaching method, in particular to a method for strengthening chalcopyrite bioleaching based on regulating redox potential and free radical effect in an oxygen environment, and belongs to the technical field of biometallurgy. Background Art

[0002] At present, copper ore bioleaching accounts for more than 30% of the total global electrolytic copper production. Compared with traditional ore dressing and pyrometallurgy, copper ore bioleaching has the advantages of short process, in-situ development, low investment cost, and lower carbon emissions in the production process. However, in the process of bioleaching of copper sulfide ore, due to the large-scale oxidation of ferrous iron in the leaching system by iron-oxidizing microorganisms and the large-scale leaching of iron ions from associated minerals in the leaching system, Fe 3+ / Fe 2+ The ratio is too high, so that the system is maintained at a high redox potential. Due to the high redox potential in the system, substances such as jarosite are easily formed at this potential. The specific reaction formula is as follows: + +3Fe 3+ +2SO4 2+ +6H2O→MFe3(SO4)2(OH)6+6H + (M + For potassium, ammonium and other cations), these substances will form a dense passivation film on the surface of the mineral, which seriously restricts leaching, so controlling the redox potential is an important way to control the formation of the passivation film. To solve this kind of problem, a Chinese patent (publication number: CN 110527830 A) discloses a method for biological leaching of chalcopyrite, which adjusts the potential by adding surfactants and / or isothiazolinone fungicides to inhibit microbial activity, but the addition of substances will have a toxic effect on the leaching microorganisms, and even kill the leaching microorganisms, affecting the microbial community and leaching performance; a Chinese patent (publication number: CN 115261619A) discloses a method for promoting microbial leaching of chalcopyrite using garnet, which can expose the adsorption sites for iron in the finely ground garnet, so that Fe 3+ The concentration decreases, but the K in garnet + Ions promote the formation of jarosite, which itself contains about 22% iron, and its effect on subsequent leaching remains to be discussed. Summary of the invention

[0003] In view of the problems existing in the prior art, the purpose of the present invention is to provide a method for strengthening chalcopyrite bioleaching by regulating redox potential and free radical effect based on oxygen environment. The method changes the micro-oxygen environment of the leaching system by alternately providing an oxygen-rich environment and an oxygen-deficient environment to adjust the redox potential to within the range of 410mV to 480mV (vs. Ag / AgCl reference electrode), and utilizes a high oxygen concentration environment to promote free radical generation and enhance copper oxidation leaching, while the oxygen-deficient environment inhibits iron oxidation and utilizes microbial anaerobic sulfur oxidation and iron reduction to enhance the selective dissolution of copper. At the same time, the ferrous ions generated in the oxygen-deficient environment are fully utilized to catalyze the generation of free radicals under oxygen-rich conditions, so that the reaction rate and leaching selectivity in the leaching process can be further optimized by alternately providing an oxygen-rich environment and an oxygen-deficient environment. The method does not add additional substances and does not have side effects on leaching microorganisms. The purpose of improving leaching efficiency and selectivity can be achieved by simply changing the oxygen environment. The method has low cost, simple operation, no new burden on leachate treatment, and no secondary pollution.

[0004] In order to achieve the above technical objectives, the present invention provides a method for strengthening the bioleaching of chalcopyrite based on regulating the redox potential and free radical effect in an oxygen environment. The method is to regulate the redox potential of the leaching system within the range of 410mV to 480mV (vs. Ag / AgCl reference electrode) by alternately providing an oxygen-rich environment and an oxygen-deficient environment during the microbial leaching of chalcopyrite to strengthen the selective leaching of copper.

[0005] In view of the technical problem that high redox potential leads to the generation of passivation film (jarosite, etc.) during biological leaching of chalcopyrite, the present invention regulates the redox potential within the range of 410mV to 480mV by changing the micro-oxygen environment of the leaching system, and the formation of the passivation film (jarosite, etc.) can be effectively prevented within the redox potential, thereby enhancing the leaching efficiency of chalcopyrite. As for the regulation of the micro-oxygen environment, the present invention adopts a method of alternately providing an oxygen-rich environment and an oxygen-deficient environment to the leaching system, which can change the micro-oxygen environment of the leaching system, promote the generation of free radicals and enhance the oxidation leaching process of copper in a high oxygen concentration environment, and inhibit the oxidation of iron in an oxygen-deficient environment, and utilize microbial anaerobic sulfur oxidation and iron reduction to enhance the selective dissolution of copper, while making full use of the oxygen-deficient environment to generate ferrous ions to catalyze the generation of free radicals under oxygen-rich conditions, so that the reaction rate and leaching selectivity in the leaching process can be further optimized by alternately providing an oxygen-rich environment and an oxygen-deficient environment.

[0006] As a preferred solution, oxygen-rich gas is first continuously introduced into the leaching system to provide an oxygen-rich environment. When the redox potential of the leaching system rises to 480 mV, the introduction of oxygen-rich gas is stopped, and then non-oxygen gas or a closed leaching system is continuously introduced into the leaching system to provide an oxygen-deficient environment. When the redox potential in the leaching system drops to 410 mV, oxygen-rich gas is continuously introduced into the leaching system to provide an oxygen-rich environment. This process is repeated alternately to control the redox potential of the leaching system between 410 mV and 480 mV. The invention constructs an oxygen-rich environment and an oxygen-deficient environment by alternately supplying oxygen and non-oxygen gas (or isolating oxygen). The high oxygen concentration in the oxygen-rich environment can promote the generation of free radicals and the synergistic enhancement of copper oxidation leaching by microorganisms, while the anaerobic environment inhibits the oxidation of ferrous iron, and enhances the selective dissolution of copper by microbial sulfur oxidation and ferric iron reduction, thereby greatly improving the selective leaching of copper. At the same time, the ferrous ions generated in the anaerobic environment are used to catalyze the generation of free radicals under oxygen-rich conditions, and the oxygen-rich environment and the anaerobic environment synergistically enhance the selective leaching of copper, and the redox potential of the leaching system is controlled between 410mV and 480mV, mainly to prevent a large amount of iron ions from forming a dense and stable passivation film of minerals such as jarosite on the surface of pyrite, thereby severely limiting the leaching of copper.

[0007] As a preferred solution, the non-oxygen gas includes at least one of nitrogen, carbon dioxide or inert gas. The non-oxygen gas is mainly used to isolate oxygen, and nitrogen, carbon dioxide or inert gas can meet the application requirements.

[0008] As a preferred solution, the oxygen content of the oxygen-enriched gas is not less than 21% by volume. The oxygen-enriched gas mainly has a higher oxygen concentration than air relative to air.

[0009] As a preferred solution, the chalcopyrite is ground to a particle size of -75 mm.

[0010] As a preferred embodiment, the microorganisms include at least one of iron-oxidizing bacteria, sulfur-oxidizing bacteria and iron-sulfur-oxidizing bacteria.

[0011] As a preferred solution, the concentration of chalcopyrite in the leaching system is 1-5wt%; the components and contents of the culture solution in the leaching system are: (NH4)2SO4 2.0-4.0g / L, MgSO4·7H2O 0.4-0.6g / L, KCl 0.05-0.15g / L, Ca(NO3)2 0.005-0.015g / L, and K2HPO4 0.40-0.60g / L.

[0012] As a preferred solution, the conditions for the microbial leaching are: pH 2.0±0.2, temperature 30±2°C, and stirring speed 150-200 rpm.

[0013] The present invention changes the micro-oxygen environment of the leaching system by alternately providing an oxygen-rich environment and an oxygen-deficient environment to adjust the redox potential to within the range of 410mV to 480mV (vs. Ag / AgCl reference electrode). Within the redox potential range, the free radical effect is enhanced in the oxygen-rich environment, while the iron reduction sulfur oxidation selective leaching effect is enhanced in the oxygen-deficient environment, and the concentration of ferrous ions that can catalyze the generation of free radicals in the leaching system is increased to promote the generation of free radicals in the oxygen-rich environment. The reaction rate and selectivity in the leaching process are further optimized. When the reduction potential is controlled within the range of 410mV to 480mV, the formation of iron alum substances can be effectively suppressed, thereby weakening the passivation of the chalcopyrite surface during the leaching process and enhancing the efficiency of chalcopyrite leaching.

[0014] The free radicals generated by catalysis of ferrous ions accumulated in the bioleaching system under an oxygen-rich environment of the present invention include hydroxyl free radicals, superoxide free radicals, singlet oxygen free radicals and the like.

[0015] The leaching system of the present invention includes chalcopyrite powder, 9k culture solution and leaching microorganisms. The 9k culture solution has the following components: (NH4)2SO4 is 3.0 g / L, MgSO4·7H2O is 0.5 g / L, KCl is 0.1 g / L, Ca(NO3)2 is 0.01 g / L, and K2HPO4 is 0.50 g / L.

[0016] Compared with the prior art, the technical solution of the present invention has the following beneficial technical effects:

[0017] (1) The present invention does not add any additional substances during the microbial leaching process, and will not produce any side effects on the leaching microorganisms.

[0018] (2) In the process of microbial leaching, the present invention realizes micro-oxygen environment regulation by alternately providing an oxygen-rich environment and an oxygen-deficient environment. When the high oxygen concentration reached by the oxygen supply can promote the generation of free radicals and the microorganisms to synergistically enhance the oxidative leaching of copper, the oxygen-deficient environment inhibits the oxidation of ferrous iron, and enhances the selective dissolution of copper through microbial sulfur oxidation and ferric iron reduction. At the same time, the oxygen-deficient environment is used to increase the concentration of ferrous ions in the leaching system that can catalyze the generation of free radicals, so as to promote the generation of free radicals in the oxygen-rich environment.

[0019] (3) During the microbial leaching process, the present invention constructs an anaerobic environment to slow down the physiological activities of microorganisms to control the oxidation rate of ferrous iron, thereby effectively regulating the redox potential and enhancing the leaching of copper.

[0020] (4) The present invention only requires simple oxygen environment control during the microbial leaching process, which is low-cost, simple in method, does not create a new burden on the leaching liquid treatment, and does not cause secondary pollution.

[0021] (5) In the process of microbial leaching, the present invention controls the oxygen environment to adjust the redox potential within a suitable range, thereby effectively preventing the rapid formation of a passivation film and enhancing the leaching of chalcopyrite. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a process flow chart of the present invention.

[0023] Figure 2 This is a graph showing the copper leaching rate versus time of the leaching system in Example 1 of the present invention (the chalcopyrite concentration is 1 wt %, and the acidophilic bacteria used are composed of Acidithiobacillus ferrooxdians and Acidithiobacillus Thiooxidan).

[0024] Figure 3 This is a time trend chart of the redox potential of the leaching system in Example 1 of the present invention vs. the Ag / AgCl reference electrode (the chalcopyrite concentration is 1 wt %, and the acidophilic bacteria used are composed of Acidithiobacillus ferrooxdians and Acidithiobacillus Thiooxidan).

[0025] Figure 4 This is a bar graph of the change in superoxide radical concentration in the leaching system in Example 1 of the present invention (the chalcopyrite concentration is 1 wt %, and the acidophilic bacteria used are composed of Acidithiobacillus ferrooxdians and Acidithiobacillus Thiooxidan).

[0026] Figure 5 This is a bar graph of the change in hydroxyl radical concentration in the leaching system in Example 1 of the present invention (the chalcopyrite concentration is 1 wt %, and the acidophilic bacteria used are composed of Acidithiobacillus ferrooxdians and Acidithiobacillus Thiooxidan).

[0027] Figure 6 This is a graph showing the copper leaching rate versus time of the leaching system in Example 2 of the present invention (the chalcopyrite concentration is 3 wt %, and the acidophilic bacteria used are composed of Acidithiobacillus ferrooxdians and Acidithiobacillus Thiooxidan).

[0028] Figure 7This is a time trend chart of the redox potential of the leaching system vs. the Ag / AgCl reference electrode in Example 2 of the present invention (the chalcopyrite concentration is 3 wt %, and the acidophilic bacteria used are composed of Acidithiobacillus ferrooxdians and Acidithiobacillus Thiooxidan).

[0029] Figure 8 This is a bar graph of the change in superoxide radical concentration in the leaching system in Example 2 of the present invention (the chalcopyrite concentration is 3 wt %, and the acidophilic bacteria used are composed of Acidithiobacillus ferrooxdians and Acidithiobacillus Thiooxidan).

[0030] Fig. 9 This is a bar graph of the change in hydroxyl radical concentration in the leaching system in Example 2 of the present invention (the chalcopyrite concentration is 3 wt %, and the acidophilic bacteria used are composed of Acidithiobacillus ferrooxdians and Acidithiobacillus Thiooxidan).

[0031] Fig.10 This is a graph showing the copper leaching rate versus time of the leaching system in Example 3 of the present invention (the chalcopyrite concentration is 1 wt %, and the acidophilic bacteria used are composed of an enrichment of acidic mine wastewater).

[0032] Fig.11 The redox potential of the leaching system in Example 3 of the present invention vs. the Ag / AgCl reference electrode over time (the chalcopyrite concentration is 1 wt %, and the acidophilic bacteria used are composed of acid mine wastewater enrichments, including acidophilic bacteria and acidithiobacillus bacteria).

[0033] Fig.12 This is a bar graph of the change in superoxide radical concentration in the leaching system in Example 3 of the present invention (the chalcopyrite concentration is 1 wt %, and the acidophilic bacteria used are composed of acid mine wastewater enrichments, including acidophilic bacteria and acidithiobacillus bacteria).

[0034] Fig.13 This is a bar graph of the change in hydroxyl radical concentration in the leaching system in Example 3 of the present invention (the chalcopyrite concentration is 1 wt %, and the acidophilic bacteria used are composed of acid mine wastewater enrichments, including acidophilic bacteria and acidithiobacillus bacteria). DETAILED DESCRIPTION

[0035] The present invention is further described below in conjunction with the accompanying drawings and specific preferred embodiments, but the protection scope of the present invention is not limited thereby.

[0036] The microbial strains involved in the following specific examples are obtained from the China Center for Type Culture Collection or acidophilic bacteria enriched by acid mine wastewater.

[0037] Microbial inoculation and expansion culture process: Take the purchased Acidithiobacillus ferrooxdians and Acidithiobacillus Thiooxidan as examples. By adding 44.79g / L of ferrous sulfate heptahydrate and 10g / L of elemental sulfur (sublimed sulfur) as energy materials to the 9k culture solution, the inoculation amount of each acidophilus is 10ml / L, and then the inoculation is carried out after expansion culture. When the total concentration of the composite flora reaches 1×10 10 / L or more, it is used for leaching chalcopyrite. The composition of the 9k culture solution is as follows: (NH4)2SO4 is 3.0g / L, MgSO4·7H2O is 0.5g / L, KCl is 0.1g / L, Ca(NO3)2 is 0.01g / L, and K2HPO4 is 0.50g / L.

[0038] In the following examples, the leaching system includes chalcopyrite powder and 9k culture solution inoculated with leaching microorganisms. The specific conditions of the microbial leaching process are: pH 2.0, temperature 30°C, and stirring speed 180 rpm.

[0039] Example 1

[0040] The acidophilic bacteria group selected is composed of Acidithiobacillus ferrooxdians and Acidithiobacillus Thiooxidan. The chalcopyrite is ground to less than 75 mm. The chalcopyrite concentration in the stirring system is 1wt%. Oxygen is continuously introduced during the leaching process. After the redox potential reaches 480mV, the closed stirring environment is used to reduce the redox potential to 410mV. The cycle is repeated for 56 days.

[0041] Comparison index: In Example 1, the oxygen environment is compared with aerobic conditions, anoxic conditions and oxygen environment regulation. Figure 2 The results showed that after 56 days of leaching, the leaching rate under aerobic conditions was 62.03%, the leaching rate under anoxic conditions was 8.2%, and the leaching rate under oxygen environment control was 73.94%, which was 11.91% higher than that under conventional aerobic conditions, thereby enhancing the leaching rate of chalcopyrite.

[0042] Figure 2 and Figure 3The results showed that the redox potential could not be controlled under aerobic conditions, and the leaching rate increased slowly after reaching 628 mV on the 20th day, while the leaching rate continued to increase under oxygen environment control conditions.

[0043] Figure 4 and Figure 5 It shows that the amount of instantaneous free radicals increases under aerobic conditions under oxygen regulation. The free radical concentration under oxygen regulation at the highest concentration is more than 50% higher than that under continuous aerobic conditions, indicating that regulating oxygen conditions enhances the free radical effect and strengthens oxidation to a certain extent, thereby enhancing leaching.

[0044] Example 2

[0045] The acidophilic bacteria group selected is composed of Acidithiobacillus ferrooxdians and Acidithiobacillus Thiooxidan. The chalcopyrite is ground to less than 75 mm. The chalcopyrite concentration in the stirring system is 3wt%. Oxygen is continuously introduced during the leaching process. After the redox potential reaches 480mV, the closed stirring environment is used to reduce the redox potential to 410mV. The cycle is repeated for 56 days.

[0046] Comparison index: In Example 2, the oxygen environment is compared with aerobic conditions, anoxic conditions and oxygen environment control. Figure 6 The results showed that after 56 days of leaching, the leaching rate under aerobic conditions was 60.29%, the leaching rate under anoxic conditions was 7.78%, and the leaching rate under oxygen environment control was 71.30%, which was 11.01% higher than that under conventional aerobic conditions, thereby enhancing the leaching rate of chalcopyrite.

[0047] Figure 6 and Figure 7 The results showed that the redox potential could not be controlled under aerobic conditions, and the leaching rate increased slowly after reaching 639 mV on the 20th day, while the leaching rate continued to increase under oxygen environment control conditions.

[0048] Figure 8 and Fig. 9 It shows that the amount of instantaneous free radicals increases under aerobic conditions under oxygen regulation, indicating that regulating oxygen conditions enhances the free radical effect, enhances oxidation and strengthens leaching to a certain extent.

[0049] Example 3

[0050] Acidophilic bacteria were selected as the enrichment composition of acidic mine wastewater, including acidophilic bacteria and acidithiobacillus bacteria. Chalcopyrite was ground to less than 75 mm. The chalcopyrite concentration in the stirring system was 1 wt%. Oxygen was continuously introduced during the leaching process. After the redox potential reached 480 mV, a closed stirring environment was used to reduce the redox potential to 410 mV. The cycle was repeated for 56 days.

[0051] Comparison index: In Example 3, the oxygen environment is compared with aerobic conditions, anoxic conditions and oxygen environment regulation. Fig.10 The results showed that after 56 days of leaching, the leaching rate under aerobic conditions was 63.79%, the leaching rate under anoxic conditions was 8.40%, and the leaching rate under oxygen environment control was 73.72%, which was 9.93% higher than that under conventional aerobic conditions, thereby enhancing the leaching rate of chalcopyrite.

[0052] Fig.10 and Fig.11 The results showed that the redox potential could not be controlled under aerobic conditions, and the leaching rate increased slowly after reaching 637 mV on the 20th day, while the leaching rate continued to increase under oxygen environment control conditions.

[0053] Fig.12 and Fig.13 It shows that the amount of instantaneous free radicals increases under aerobic conditions under oxygen regulation, indicating that regulating oxygen conditions enhances the free radical effect, enhances oxidation and strengthens leaching to a certain extent.

[0054] In summary, the present invention effectively regulates the redox potential based on the oxygen environment, and the free radical effect is enhanced under oxygen regulation, thereby enhancing leaching. Different acidophilic bacteria combinations and acid mine wastewater enriched bacteria groups also have good leaching effects, significantly enhancing the leaching of chalcopyrite.

[0055] The above embodiments are only preferred implementations of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A method for enhancing chalcopyrite bioleaching based on regulating redox potential and free radical effect in an oxygen environment, characterized in that: In the microbial leaching process of chalcopyrite, the redox potential of the leaching system is regulated within the range of 410 mV to 480 mV (vs. Ag / AgCl reference electrode) by alternately providing an oxygen-rich environment and an oxygen-deficient environment to enhance the selective leaching of copper.

2. The method for enhancing chalcopyrite bioleaching based on regulating redox potential and free radical effect in an oxygen environment according to claim 1, characterized in that: First, oxygen-rich gas is continuously introduced into the leaching system to provide an oxygen-rich environment. When the redox potential of the leaching system rises to 480 mV, the introduction of oxygen-rich gas is stopped, and then non-oxygen gas or a closed leaching system is continuously introduced into the leaching system to provide an oxygen-deficient environment. When the redox potential in the leaching system drops to 410 mV, oxygen-rich gas is continuously introduced into the leaching system to provide an oxygen-rich environment. This process is repeated alternately to control the redox potential of the leaching system between 410 mV and 480 mV.

3. The method for enhancing chalcopyrite bioleaching based on regulating redox potential and free radical effect in an oxygen environment according to claim 2, characterized in that: The non-oxygen gas includes at least one of nitrogen, carbon dioxide and an inert gas; The volume content of oxygen in the oxygen-rich gas is not less than 21%.

4. The method for enhancing chalcopyrite bioleaching based on regulating redox potential and free radical effect in an oxygen environment according to claim 1, characterized in that: The chalcopyrite is ground to a particle size of -75 mm.

5. The method for enhancing chalcopyrite bioleaching based on regulating redox potential and free radical effect in an oxygen environment according to claim 1, characterized in that: The microorganisms include at least one of iron oxidizing bacteria, sulfur oxidizing bacteria and iron-sulfur oxidizing bacteria.

6. The method for enhancing chalcopyrite bioleaching based on regulating redox potential and free radical effect in an oxygen environment according to claim 1, characterized in that: The concentration of chalcopyrite in the leaching system is 1 to 5 wt%; The components and contents of the culture solution in the leaching system are: (NH4)2SO4 2.0-4.0 g / L, MgSO4·7H2O 0.4-0.6 g / L, KCl 0.05-0.15 g / L, Ca(NO3)2 0.005-0.015 g / L, and K2HPO4 0.40-0.60 g / L.

7. A method for enhancing chalcopyrite bioleaching based on regulating redox potential and free radical effect in an oxygen environment according to claim 1, 2, 3, 4, 5 or 6, characterized in that: The conditions for the microbial leaching are: pH 2.0±0.2, temperature 30±2° C., and stirring speed 150-200 rpm.

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