Method for modifying activated carbon to enhance biooxidation of arsenic-containing gold ores

Abstract

The application discloses a method for modifying activated carbon to strengthen biological oxidation of arsenic-containing gold ore, which comprises the following steps: adding finely ground arsenic-containing gold ore into a culture medium, then injecting ferrous iron sulfur bacillus and adding modified activated carbon, adjusting pH of the ore slurry to be acidic by using sulfuric acid, and placing the ore slurry under a certain temperature and rotating speed to perform biological oxidation for a certain time; the preparation method of the modified activated carbon comprises the following steps: adding activated carbon into sulfuric acid, uniformly mixing and placing for a certain time to obtain acid-oxidized activated carbon; the acid-oxidized activated carbon is completely cleaned by using distilled water, then is placed in an iron ion solution to prepare ferrous sulfate; the pH is maintained at 2.0-3.2, the activated carbon is filtered out after being placed for a certain time, and is dried to obtain modified activated carbon. The method is low in price, high in efficiency, simple in operation, and solves the technical problems of bacterial activity recession, low oxidation rate and long oxidation cycle of the existing biological oxidation method of arsenic-containing gold ore.

Description

Technical Field

[0001] This invention relates to the fields of biohydrometallurgy and mineral processing technology, specifically to a method for enhancing the bio-oxidation of arsenic-containing gold ore with modified activated carbon. Background Technology

[0002] In arsenic-bearing gold ores, gold typically exists as extremely fine particles or submicroscopic forms, or even as disseminated inclusions within the crystal lattice of arsenopyrite. Therefore, pre-oxidation treatment is necessary before leaching gold to expose the gold inclusions within the ore. Current pretreatment methods for arsenic-bearing gold ores include chemical oxidation, oxidative roasting, and biological oxidation. Biological oxidation, with its advantages of low investment, low pollution, and simple operation, has significant development and application prospects. The main gold-bearing mineral in arsenic-bearing gold ores is FeAsS. During bacterial leaching of arsenopyrite, the concentrations of iron and arsenic ions continuously increase, leading to the formation of a passivation film on the mineral surface. Furthermore, the toxicity of arsenic ions reduces the biological and oxidative activity of bacteria, thus prolonging the oxidation cycle. Therefore, reducing the toxicity of arsenic to bacteria is crucial for increasing the bacterial oxidation rate and shortening the leaching cycle.

[0003] Activated carbon has a large specific surface area, enabling it to adsorb not only organic compounds but also heavy metal ions and anions. Studies have shown that activated carbon can significantly improve the bioleaching rate of copper ions from chalcopyrite through simultaneous dissolution and adsorption. However, activated carbon has limited adsorption capacity for arsenic, although modification can significantly increase its arsenic loading in heavy metal wastewater. This suggests that modified activated carbon can simultaneously adsorb the concentrations of iron and arsenic ions in solution, inhibiting the formation of passivation films and reducing the toxicity of arsenic to bacteria. However, the enhancing effect of modified activated carbon on the bio-oxidation of arsenopyrite (a type of arsenopyrite) remains unknown. Summary of the Invention

[0004] In view of the above-mentioned shortcomings, the present invention provides a method for enhancing the biological oxidation of arsenic-containing gold ore with modified activated carbon. This method is inexpensive, efficient, simple and easy to operate, and solves the technical problems of bacterial activity decline, low oxidation rate and long oxidation cycle in existing biological oxidation methods for arsenic-containing gold ore.

[0005] To achieve the above objectives, the present invention provides a method for enhancing the bio-oxidation of arsenic-containing gold ore with modified activated carbon, comprising the following steps:

[0006] Finely ground arsenic-containing gold ore was added to a culture medium, then *Thiobacillus ferrooxidans* was injected, and modified activated carbon was added. The pH of the slurry was adjusted to acidic with sulfuric acid, and the slurry was placed under a certain temperature and rotation speed for a certain period of time for biological oxidation.

[0007] The method for preparing the modified activated carbon includes the following steps:

[0008] Step 1: Add activated carbon to sulfuric acid, mix well, and let stand for a certain period of time to obtain activated carbon after acid oxidation;

[0009] Step 2: The activated carbon obtained after acid oxidation is thoroughly washed with distilled water and then placed in an iron ion solution to prepare ferrous sulfate; the pH is then maintained at 2.0 to 3.2, and after a certain period of time, the activated carbon is filtered out and dried to obtain modified activated carbon.

[0010] According to one aspect of the present invention, the culture medium is 9K culture medium, the main components of which include: 3.0 g / L (NH4)2SO4, 0.5 g / L MgSO4·7H2O, 0.5 g / L K2HPO4·3H2O, 0.1 g / L KCl, 0.01 g / L Ca(NO3)2·4H2O, and 44.7 g / L FeSO4·7H2O.

[0011] According to one aspect of the invention, the arsenic-containing gold ore is finely ground to below -0.074 mm mesh.

[0012] According to one aspect of the present invention, the amount of the modified activated carbon is 1.5 to 2.5 g / L.

[0013] According to one aspect of the invention, the concentration of sulfuric acid in the slurry pH adjustment is 2-3 M.

[0014] According to one aspect of the invention, the pH of the slurry is adjusted to acidity of 1.5 to 2 using sulfuric acid.

[0015] According to one aspect of the present invention, the step of subjecting the slurry to bio-oxidation at a certain temperature and rotation speed for a certain period of time specifically involves subjecting the slurry to bio-oxidation at 20–40°C and 150–170 rpm for 6–8 days.

[0016] According to one aspect of the invention, in step 1, the sulfuric acid is 70% sulfuric acid, and the certain time is 1 hour.

[0017] According to one aspect of the present invention, in step 2, the concentration of the iron ion solution is 10 mM, the certain time is 20 minutes, and the drying temperature is 105°C.

[0018] The beneficial effects of this invention are:

[0019] Adding modified activated carbon to the slurry of arsenic-containing gold ore allows the ferrous ions in the modified activated carbon to undergo a displacement reaction with the arsenic ions and Fe(III) in the solution. This continuously adsorbs arsenic ions and Fe(III) in the solution, reducing the toxicity of arsenic to bacteria and inhibiting the formation of the passivation film of potassium ferric sulfate. At the same time, the release of Fe(II) reduces the redox potential, increasing the oxidation rate of arsenic-containing gold ore. This shortens the biological oxidation cycle by more than 3 days and increases the arsenic leaching rate by more than 15%. Moreover, this method is inexpensive, efficient, and easy to operate, solving the technical problems of bacterial activity decline, low oxidation rate, and long oxidation cycle in existing biological oxidation methods for arsenic-containing gold ore. Detailed Implementation

[0020] To make the present invention easier to understand, specific embodiments are described below to further illustrate the invention. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Unless otherwise defined, the technical terms used below have the same meaning as understood by those skilled in the art; unless otherwise specified, the raw materials and reagents involved herein can be purchased commercially or obtained by known methods.

[0021] It should be noted that the domesticated *Thiobacillus ferrooxidans* in the embodiments of this application were passaged more than three times in the arsenic-containing gold ore leaching solution of the corresponding embodiment of this application, with each passage lasting 5 to 7 days.

[0022] It should be noted that the *Acidithiobacillus ferrooxidans* used in this application was purchased. The *Acidithiobacillus ferrooxidans* used in this application is *Acidithiobacillus ferrooxidans* 23270, and its accession number is ATCC23270.

[0023] It should be noted that the composition of the arsenopyrite in the embodiments and comparative examples of this application is shown in Table 1 below:

[0024] Table 1. Multi-element analysis results of arsenopyrite (wt.%)

[0025]

[0026] Currently, pretreatment methods for arsenic-bearing gold ores include chemical oxidation, oxidative roasting, and biological oxidation. Biological oxidation, with its advantages of low investment, low pollution, and simple operation, has great development and application prospects. The main gold-bearing minerals in arsenic-bearing gold ores are FeAsS. During bacterial leaching of arsenopyrite, the concentrations of iron and arsenic ions continuously increase, leading to the formation of a passivation film on the mineral surface. Furthermore, the toxicity of arsenic ions reduces the biological and oxidative activity of bacteria, thus prolonging the oxidation cycle. Therefore, reducing the toxicity of arsenic to bacteria is key to improving the bacterial oxidation rate and shortening the leaching cycle. Activated carbon has a large specific surface area and can adsorb not only organic compounds but also heavy metal ions and anions. Studies have shown that activated carbon can significantly improve the bioleaching rate of copper ions in chalcopyrite through simultaneous dissolution and adsorption. However, activated carbon has limited adsorption capacity for arsenic.

[0027] To address the above problems, this invention provides a method for enhancing the bio-oxidation of arsenic-containing gold ore with modified activated carbon, comprising the following steps:

[0028] Finely ground arsenic-containing gold ore was added to a culture medium, then *Thiobacillus ferrooxidans* was injected, and modified activated carbon was added. The pH of the slurry was adjusted to acidic with sulfuric acid, and the slurry was placed under a certain temperature and rotation speed for a certain period of time for biological oxidation.

[0029] The method for preparing the modified activated carbon includes the following steps:

[0030] Step 1: Add activated carbon to sulfuric acid, mix well, and let stand for a certain period of time to obtain activated carbon after acid oxidation;

[0031] Step 2: The activated carbon obtained after acid oxidation is thoroughly washed with distilled water and then placed in an iron ion solution to prepare ferrous sulfate; the pH is then maintained at 2.0 to 3.2, and after a certain period of time, the activated carbon is filtered out and dried to obtain modified activated carbon.

[0032] Preferably, the culture medium is 9K medium, the main components of which include: 3.0 g / L (NH4)2SO4, 0.5 g / L MgSO4·7H2O, 0.5 g / L K2HPO4·3H2O, 0.1 g / L KCl, 0.01 g / L Ca(NO3)2·4H2O, and 44.7 g / L FeSO4·7H2O.

[0033] Preferably, the arsenic-containing gold ore is finely ground to below -0.074 mm mesh.

[0034] Preferably, the amount of modified activated carbon is 1.5 to 2.5 g / L.

[0035] Preferably, the concentration of sulfuric acid in the slurry pH adjustment is 2-3 M.

[0036] Preferably, the pH of the slurry is adjusted to acidity using sulfuric acid, specifically to 1.5 to 2.

[0037] Preferably, the step of subjecting the slurry to bio-oxidation at a certain temperature and rotation speed for a certain period of time specifically involves subjecting the slurry to bio-oxidation at 20–40°C and 150–170 rpm for 6–8 days.

[0038] Preferably, in step 1, the sulfuric acid is 70% sulfuric acid, and the specified time is 1 hour.

[0039] It should be noted that the purpose of mixing evenly and letting it stand for 1 hour in step 1 of the preparation method of modified activated carbon in this application is to increase the number of oxygen-containing photoenergy groups and the cation loading capacity on the surface of activated carbon.

[0040] Preferably, in step 2, the concentration of the iron ion solution is 10 mM, the time is 20 minutes, and the drying temperature is 105°C.

[0041] It should be noted that the pH in step 2 of the preparation method of modified activated carbon in this application is maintained at 2.0 to 3.2, and the purpose of letting it stand for 20 minutes is to allow ferrous ions to be fully adsorbed on the surface of the modified carbon.

[0042] The following detailed explanation is provided in conjunction with embodiments and comparative examples.

[0043] Example 1

[0044] 100 mL of 9K culture medium and 2 g of finely ground arsenopyrite (0.074 mm mesh) were added to a 250 mL Erlenmeyer flask. The pH of the solution was adjusted to 2.0 using 3M sulfuric acid. 15 mL of acclimated ferrooxidizobacterium oxidans was injected, and 0.2 g of modified activated carbon was added. After oxidation in a constant temperature incubator at 30 °C and 160 rpm for 6 days, the arsenic leaching rate was 88.67%. After oxidation for 8 days, the arsenic leaching rate was 94.23%.

[0045] Preparation of modified activated carbon:

[0046] Step 1: Add 2g of activated carbon to 100mL of 70% sulfuric acid, mix well and let stand for one hour to increase the number of oxygen-containing photoenergy groups and cation loading capacity on the surface of activated carbon.

[0047] Step 2: Thoroughly wash the acid-oxidized activated carbon with distilled water, then place it in 1L of 10mM ferrous ion solution (prepared with ferrous sulfate), maintain the pH at 2.0 to 3.2, and let it stand for 20 minutes to allow the ferrous ions to be fully adsorbed on the surface of the modified carbon. Filter out the activated carbon and dry it at 105℃.

[0048] Comparative Example 1

[0049] Add 100 mL of 9K culture medium and 2 g of finely ground arsenopyrite (0.074 mm mesh) to a 250 mL Erlenmeyer flask. Adjust the pH of the solution to 2.0 with 3M sulfuric acid. Inject 15 mL of acclimatized ferrooxidizobacterium oxysporum. After oxidizing for 10 days in a constant temperature incubator at 30 °C and 160 rpm, the arsenic leaching rate was 83.56%.

[0050] Comparative Example 2

[0051] 100 mL of 9K culture medium and 2 g of finely ground arsenopyrite (0.074 mm mesh) were added to a 250 mL Erlenmeyer flask. The pH of the solution was adjusted to 2.0 with 3 M sulfuric acid. 15 mL of acclimatized ferrooxidizobacterium oxygenase was injected, and 0.2 g of original activated carbon was added. After oxidation in a constant temperature incubator at 30 °C and 160 rpm for 10 days, the arsenic leaching rate was 86.38%.

[0052] Results analysis:

[0053] As shown in Example 1 and Comparative Examples 1-2, the modified activated carbon (Example 1) significantly shortened the leaching cycle of arsenic-containing gold ore during the bio-oxidation process of arsenopyrite from 10 days in Comparative Examples 1-2 to 6 days, and the arsenic leaching rate also significantly increased from 83.56% in Comparative Example 1 to 94.23%. Compared with Comparative Example 2, the modified activated carbon showed a greater effect on improving the arsenic leaching rate of arsenopyrite than the original activated carbon, indicating that the activated carbon modification was effective.

[0054] In summary, this invention can not only significantly shorten the leaching cycle of bio-oxidation of arsenic-containing gold ore, but also greatly increase the leaching rate of arsenic, thereby improving the gold recovery rate.

[0055] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for enhancing the bio-oxidation of arsenic-containing gold ore with modified activated carbon, characterized in that, Includes the following steps: Finely ground arsenic-containing gold ore was added to a culture medium, then *Thiobacillus ferrooxidans* was injected, and modified activated carbon was added. The pH of the slurry was adjusted to acidic with sulfuric acid, and the slurry was subjected to bio-oxidation at a certain temperature and rotation speed for a certain period of time. The amount of modified activated carbon was 1.5~2.5 g / L. The method for preparing the modified activated carbon includes the following steps: Step 1: Add activated carbon to sulfuric acid, mix well, and let stand for a certain period of time to obtain activated carbon after acid oxidation; Step 2: The activated carbon obtained after acid oxidation is thoroughly washed with distilled water and then placed in an iron ion solution to prepare ferrous sulfate; the pH is then maintained at 2.0 to 3.2, and after a certain period of time, the activated carbon is filtered out and dried to obtain modified activated carbon.

2. The method for enhancing the bio-oxidation of arsenic-containing gold ore with modified activated carbon according to claim 1, characterized in that, The culture medium is 9K medium, whose main components include: 3.0 g / L (NH4)2SO4, 0.5 g / L MgSO4·7H2O, 0.5 g / L K2HPO4·3H2O, 0.1 g / L KCl, 0.01 g / L Ca(NO3)2·4H2O, and 44.7 g / L FeSO4·7H2O.

3. The method for enhancing the bio-oxidation of arsenic-containing gold ore with modified activated carbon according to claim 1, characterized in that, The arsenic-bearing gold ore was finely ground to below -0.074 mm mesh.

4. The method for enhancing the bio-oxidation of arsenic-containing gold ore with modified activated carbon according to claim 1, characterized in that, The concentration of sulfuric acid in the slurry used to adjust the pH of the slurry is 2-3 M.

5. The method for enhancing the bio-oxidation of arsenic-containing gold ore with modified activated carbon according to claim 1, characterized in that, The pH of the slurry is adjusted to acidity using sulfuric acid, specifically to a level of 1.5 to 2.

6. The method for enhancing the bio-oxidation of arsenic-containing gold ore with modified activated carbon according to claim 1, characterized in that, The process of subjecting the slurry to bio-oxidation at a specific temperature and rotation speed for a specific period of time specifically involves subjecting the slurry to bio-oxidation at 20-40℃ and 150-170 rpm for 6-8 days.

7. The method for enhancing the bio-oxidation of arsenic-containing gold ore with modified activated carbon according to claim 1, characterized in that, In step 1, the sulfuric acid is 70% sulfuric acid, and the specified time is 1 hour.

8. The method for enhancing the bio-oxidation of arsenic-containing gold ore with modified activated carbon according to claim 1, characterized in that, In step 2, the concentration of the iron ion solution is 10 mM, the time is 20 minutes, and the drying temperature is 105°C.

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