Method for green and efficient recovery of gold from refractory gold ore

Abstract

The invention discloses a method for green and efficient recovery of gold from refractory gold ore. The green and efficient gold recovery method for the refractory gold ore comprises the following steps that biological oxidation pretreatment is conducted on the refractory gold ore, and biological oxidation ore pulp is obtained; adjusting the pH value of the biological oxidation ore pulp, standing for 1-3 days to carry out bacterial inactivation on the biological oxidation ore pulp, then adding a proper amount of iron-based ligand to adjust the potential of the biological oxidation ore pulp to a proper range, and then adding a proper amount of thiosulfate to carry out in-situ leaching to obtain leached ore pulp; and the leaching ore pulp is filtered and separated, and gold leaching liquid and leaching residues are obtained. According to the method for green and efficient gold recovery from the refractory gold ore, a biological oxidation pretreatment method and a weakly acidic iron-based thiosulfate in-situ leaching process are combined, acid-base conversion of ore pulp is not needed, and green and efficient leaching of gold in the refractory gold ore can be achieved with the low production cost and the short process.

Description

Technical Field

[0001] This invention relates to the fields of hydrometallurgy and precious metal production and processing technology, specifically to a green and efficient method for recovering gold from refractory gold ores. Background Technology

[0002] With the increasing depletion of easily processed gold ore resources, refractory gold ores (such as those containing sulfur and arsenic) have gradually become the main source of gold production in various countries around the world. Before leaching refractory gold ores, pretreatment operations such as roasting oxidation, biological oxidation, and pressure oxidation are usually required to break the gold encapsulation by associated minerals such as arsenopyrite. Among these pretreatment methods, biological oxidation has great development potential due to its advantages of being environmentally friendly and having low energy consumption. Currently, after biological oxidation, refractory gold ores are mainly leached using alkaline cyanidation. However, this process brings the following problems: First, the acidic slag (pH 1.5-2.0) produced by biological oxidation contains a large amount of soluble ions such as iron, arsenic, and sulfate. These substances will consume cyanide and oxygen rapidly, and the slurry needs to undergo additional acid-base conversion, resulting in high alkali consumption and a cumbersome process. Second, cyanide itself is highly toxic, posing a direct threat to the environment and human health. The cyanide-containing wastewater and cyanide tailings produced also have problems such as high treatment costs and difficulty in stockpiling.

[0003] To address the issue that cyanidation methods cannot meet current environmental requirements, the industry has developed various non-cyanide gold leaching agents. Among them, the thiosulfate leaching system is widely considered the most promising non-cyanide gold leaching technology due to its green and efficient characteristics. However, the traditional thiosulfate leaching system, which uses copper-ammonia complex ions as catalytic oxidants, suffers from the bottleneck of high thiosulfate consumption, making it difficult to balance economic efficiency and practicality. To overcome this challenge, some invention patents propose adding additives to the system or using other catalytic systems. For example, Chinese invention patent CN103740930B uses alkyltrimethyl quaternary ammonium salt as an additive, Chinese invention patent CN112961991A uses a copper-glycine system as a catalytic oxidant, and Chinese invention patent CN101824545A uses a copper-ethylenediamine system as a catalytic oxidant. However, these systems all leach under alkaline conditions (pH = 8–12), which still presents a mismatch with biological pretreatment processes (pH < 6). Summary of the Invention

[0004] To address the technical problems mentioned above, this invention provides a green and efficient method for recovering gold from refractory gold ores. This method achieves efficient gold leaching from refractory gold ores with lower production costs and a shorter process flow, and has significant industrial application value.

[0005] This invention provides a green and efficient method for recovering gold from refractory gold ores, comprising the following steps:

[0006] Step 1: Perform bio-oxidation pretreatment on refractory gold ore to obtain bio-oxidized slurry;

[0007] Step 2: Adjust the pH of the bio-oxidized mineral slurry, let it stand for 1-3 days to inactivate bacteria, then add an appropriate amount of iron-based ligand to adjust the potential of the bio-oxidized mineral slurry to a suitable range, and then add an appropriate amount of thiosulfate for in-situ leaching to obtain the leached mineral slurry.

[0008] Step 3: Filter and separate the leaching slurry to obtain gold leaching solution and leaching residue.

[0009] In a preferred embodiment of the green and efficient gold recovery method for refractory gold ore provided by the present invention, the biological oxidation pretreatment includes: adding 9K culture medium to the refractory gold ore at a liquid-solid ratio of 3:1 to 10:1, adjusting the pH to 1 to 2, then inoculating with an appropriate amount of bacteria, and treating at 30 to 45°C for 3 to 10 days to obtain a biological oxidation slurry.

[0010] In a preferred embodiment of the green and efficient gold recovery method for refractory gold mines provided by the present invention, the bacteria are one or more of the following: thiobacillus ferrooxidans, thiobacillus thiooxidans, leptospira ferrooxidans, and thiocyanate ferrooxidans. The inoculum amount of the bacteria is 5% to 20% of the volume of the 9K culture medium.

[0011] In a preferred embodiment of the green and efficient gold recovery method for refractory gold mines provided by the present invention, in step two, the pH of the bio-oxidation slurry is adjusted to 4-6.

[0012] In a preferred embodiment of the green and efficient gold recovery method for refractory gold mines provided by the present invention, in step two, after adding an appropriate amount of the iron-based ligand, the potential of the bio-oxidation slurry is adjusted to stabilize it at 200-350mV, and the amount of iron-based ligand added is 1-5 times the iron ion concentration in the bio-oxidation slurry.

[0013] In a preferred embodiment of the green and efficient gold recovery method for refractory gold ores provided by the present invention, the iron-based ligands include, but are not limited to, citrate, ethylenediaminetetraacetate, oxalate, and hydrocyanate, which can coordinate with iron ions and form complexes that are stable under acidic conditions.

[0014] In a preferred embodiment of the green and efficient gold recovery method for refractory gold ore provided by the present invention, the amount of thiosulfate added is 0.01-0.08 mol / L.

[0015] In a preferred embodiment of the green and efficient gold recovery method for refractory gold mines provided by the present invention, the thiosulfate includes, but is not limited to, sodium thiosulfate and potassium thiosulfate.

[0016] In a preferred embodiment of the green and efficient gold recovery method for refractory gold ore provided by the present invention, the in-situ leaching conditions are: leaching temperature 25-40℃, leaching time 8-24h, pulp pH 4-6.5, and rotation speed 250-350rpm.

[0017] Compared to existing technologies, the green and efficient gold recovery method for refractory gold ores provided by this invention has the following advantages: The bio-oxidation slurry produced during the process contains arsenate, sulfate, and sulfite ions, which effectively inhibit the decomposition of thiosulfate. Furthermore, the bio-oxidation slurry itself is rich in iron ions, which can be directly used as an oxidant in the gold leaching process. Only the addition of iron-based ligands is needed to achieve gold leaching, avoiding iron waste and reducing the cost of leaching raw materials. No solid-liquid separation is required, avoiding the generation of large amounts of acidic waste liquid and simplifying the operation process. In addition, the iron-based system can catalyze thiosulfate leaching under weakly acidic conditions, eliminating the need for acid-base conversion of the slurry and significantly reducing alkali consumption. Simultaneously, weakly acidic conditions are conducive to "alum breaking," i.e., the decomposition of potassium ferric sulfate phase. In summary, the green and efficient gold recovery method for refractory gold ores provided by this invention can achieve efficient gold leaching from refractory gold ores with lower production costs and a shorter process flow, possessing significant industrial application value. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0019] Figure 1 This is a flowchart of the green and efficient gold recovery method for refractory gold mines provided by the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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.

[0021] Please see Figure 1 , Figure 1 The flowchart illustrates the green and efficient gold recovery method for refractory gold mines provided by this invention.

[0022] The method for green and efficient gold recovery from refractory gold mines includes the following steps:

[0023] Step 1: Perform bio-oxidation pretreatment on refractory gold ore to obtain bio-oxidized slurry;

[0024] Specifically, the refractory gold ore includes, but is not limited to, refractory gold ore containing arsenic, carbon, copper, etc.

[0025] The biological oxidation pretreatment includes: adding 9K culture medium to the refractory gold ore at a liquid-solid ratio of 3:1 to 10:1, adjusting the pH to 1 to 2, then inoculating with an appropriate amount of bacteria, and treating at 30 to 45°C for 3 to 10 days to obtain a biological oxidation slurry;

[0026] The bacteria are one or more of the following: thiobacillus ferrooxidans, thiobacillus thiooxidans, leptospira ferrooxidans, and thiobacillus acidophilus. The inoculation amount of the bacteria is 5% to 20% of the volume of the 9K culture medium.

[0027] Step 2: Adjust the pH of the bio-oxidized mineral slurry, let it stand for 1-3 days to inactivate bacteria, then add an appropriate amount of iron-based ligand to adjust the potential of the bio-oxidized mineral slurry to a suitable range, and then add an appropriate amount of thiosulfate for in-situ leaching to obtain the leached mineral slurry.

[0028] Specifically, after adjusting the pH of the bio-oxidized mineral slurry to 4-6 and allowing it to stand for 1-3 days, the bacterial inactivation rate reaches over 90%.

[0029] After adding an appropriate amount of the iron-based ligand, the potential of the bio-oxidized slurry is adjusted to stabilize it at 200-350 mV. The amount of iron-based ligand added is 1-5 times the iron ion concentration in the bio-oxidized slurry.

[0030] The iron-based ligands include, but are not limited to, citrate, ethylenediaminetetraacetate, oxalate, and hydrocyanate, which can coordinate with iron ions and form complexes that are stable under acidic conditions; wherein, the citrate can react with iron ions to form Fe2(cit)2(OH)2 at pH = 4–7.9. 2- / Fe(cit) - The ethylenediaminetetraacetic acid salt can react with iron ions to form Fe(EDTA) under conditions of pH = 4 to 7.8. - / Fe(EDTA) 2- The oxalate can react with iron ions to form Fe(ox)3 under conditions of pH 4-6. 3- / Fe(ox) 0 The hydrocyanate can react with iron ions to form Fe(CN)6 under conditions of pH = 4 to 13. 3- / Fe(CN)6 4- ;

[0031] The thiosulfate includes, but is not limited to, sodium thiosulfate, potassium thiosulfate, etc., and the amount of thiosulfate added is 0.01-0.08 mol / L;

[0032] The in-situ leaching conditions are: leaching temperature 25–40℃, leaching time 8–24h, pulp pH 4–6.5, and rotation speed 250–350rpm;

[0033] Step 3: Filter and separate the leaching slurry to obtain gold leaching solution and leaching residue.

[0034] Unless otherwise specified, all raw materials used in this invention are commercially available products well known in the art.

[0035] The bio-oxidized slurry produced by this invention contains arsenate, sulfate, and sulfite ions, which can effectively inhibit the decomposition of thiosulfate. Furthermore, the bio-oxidized slurry itself is rich in iron ions, which can be directly used as an oxidant in the gold leaching process. Gold leaching can be achieved simply by adding iron-based ligands, avoiding iron waste and reducing the cost of leaching raw materials. No solid-liquid separation is required, avoiding the generation of large amounts of acidic waste liquid and simplifying the operation process. In addition, the iron-based system can catalyze thiosulfate leaching under weakly acidic conditions, eliminating the need for acid-base conversion of the slurry and significantly reducing alkali consumption. Simultaneously, weakly acidic conditions are conducive to the "alum breaking," i.e., the decomposition of potassium ferric sulfate phase. In summary, the green and efficient gold recovery method for refractory gold ores provided by this invention eliminates the need for acid-base conversion of the slurry, has low thiosulfate consumption, and can achieve efficient gold leaching from refractory gold ores with low production costs and a simplified process flow, possessing significant industrial application value.

[0036] The following detailed description of the green and efficient gold recovery method for refractory gold mines provided by the present invention, with reference to the embodiments, should not be construed as limiting the scope of protection of the present invention.

[0037] The raw materials used in the following examples and comparative examples are all refractory gold concentrates containing sulfur and arsenic in Hunan Province. The chemical composition analysis (wt.%) and phase distribution of gold in the gold concentrates are shown in Tables 1 and 2.

[0038] Table 1. Chemical composition analysis (wt.%) of a certain gold concentrate.

[0039]

[0040] *Unit g / t

[0041] Table 2 Distribution of gold phases in gold concentrate

[0042]

[0043] Unless otherwise specified, the following comparative examples and embodiments are performed as follows: 9K culture medium is added to a stirred tank along with a certain amount of gold concentrate, the liquid-to-solid ratio of the 9K culture medium to the gold concentrate is set to 2.5:1, the initial pH of the slurry is adjusted to 1.8 using diluted sulfuric acid, and then 15% Thiobacillus ferrooxidans (Tf) is inoculated. The mixture is treated for 10 days in a shaker at 160 rpm and 30°C to obtain bio-oxidized gold concentrate. The slurry was prepared by adjusting the pH of the bio-oxidized slurry to 5.5 and allowing it to stand for 3 days to inactivate the bacteria. A certain amount of iron-based ligand was added to the inactivated bio-oxidized slurry, and the slurry potential and pH were adjusted to 200–350 mV and 4–7, respectively. Then, a certain amount of sodium thiosulfate was added, and leaching was carried out at room temperature and 250–300 rpm for 24 hours. After leaching, the slurry was filtered to obtain a gold leachate. The concentration of gold in the leachate was measured, and the gold leaching rate was calculated. The concentration of thiosulfate before and after leaching was determined by iodometric titration, and the consumption rate of thiosulfate was calculated.

[0044] Comparative Example 1

[0045] (1) No bio-oxidation pretreatment is performed on the gold concentrate; instead, the gold concentrate and water are mixed to form a slurry with a liquid-to-solid ratio of 2.5:1.

[0046] (2) 0.5M sodium citrate and 0.03M sodium thiosulfate were added to the slurry in sequence to adjust the pH of the slurry to 3, 4, 5, 6 and 7 respectively, while keeping other leaching conditions unchanged. The results are shown in Table 3.

[0047] Table 3 shows the changes in gold leaching rate and thiosulfate consumption rate over time in Comparative Example 1.

[0048]

[0049] The results of multiple parallel experiments obtained using the above steps are as follows: When the gold concentrate is not pretreated by bio-oxidation, the leaching rate of gold by thiosulfate is low because the gold exists mainly in the form of encapsulated gold and no suitable catalytic oxidant is added; under the optimal condition of pH 5, the gold leaching rate is only 2.59%, and the consumption rate of thiosulfate is 4.76%.

[0050] Comparative Example 2

[0051] (1) Based on the above conditions, the gold concentrate was subjected to biological oxidation and the bacteria in the slurry were inactivated;

[0052] (2) Add 0.03M sodium thiosulfate, 0.02M copper sulfate, and 1M ammonia to the bio-oxidized slurry. Adjust the pH of the slurry with sodium hydroxide solution, while keeping other leaching conditions unchanged. The experimental results are shown in Table 4.

[0053] Table 4. Changes in gold leaching rate and thiosulfate consumption rate with pH in Comparative Example 2

[0054]

[0055] The results of multiple parallel experiments obtained using the above steps are as follows: using the traditional copper ammonia-catalyzed thiosulfate leaching process, when the pulp pH is 11, the gold leaching rate reaches 90% after 24 hours of leaching, at which point the thiosulfate consumption rate is as high as 49.82%. The traditional copper ammonia-catalyzed thiosulfate leaching process is quite sensitive to pulp pH and requires strongly alkaline leaching conditions to achieve a high gold leaching rate, which is not compatible with the acidic conditions of biological oxidation.

[0056] Example 1

[0057] (1) Based on the above conditions, the gold concentrate was subjected to biological oxidation and bacterial inactivation in the slurry, and the concentration of iron ions in the slurry was found to be 0.12 M;

[0058] (2) 0.5M sodium citrate and 0.03M sodium thiosulfate were added to the slurry in sequence to adjust the pH of the slurry to 3, 4, 5, 6 and 7 respectively, while keeping other leaching conditions unchanged. The results are shown in Table 5.

[0059] Table 5. Changes in gold leaching rate and thiosulfate consumption rate with pH in Example 1

[0060]

[0061] The results of multiple parallel experiments using the above steps are as follows: After bio-oxidation pretreatment of gold concentrate, without the addition of exogenous iron but only iron-based ligand citrate, the gold leaching rate reached 90% under acidic conditions of pH 3-6 after 24 hours of leaching. Under the optimal condition of pH 5, the gold leaching rate was 94.25%, with a thiosulfate consumption rate of only 3.77%. Compared with Comparative Example 1, the gold leaching rate can be increased by 40-50 times after bio-oxidation pretreatment. Compared with Comparative Example 2, the iron-based catalytic in-situ thiosulfate leaching process not only highly matches the acidic pulp conditions of the bio-oxidation pretreatment process, but also reduces the thiosulfate consumption rate by 10-15 times while achieving comparable or even higher gold leaching results.

[0062] Example 2

[0063] (1) Based on the above conditions, the gold concentrate was subjected to biological oxidation and bacterial inactivation in the slurry, and the concentration of iron ions in the slurry was found to be 0.12 M;

[0064] (2) 0.5M sodium oxalate and 0.03M sodium thiosulfate were added to the slurry in sequence to adjust the pH of the slurry to 3, 4, 5, 6 and 7 respectively, while keeping other leaching conditions unchanged. The results are shown in Table 6.

[0065] Table 6. Changes in gold leaching rate and thiosulfate consumption rate with pH in Example 2

[0066]

[0067] The results of multiple parallel experiments using the above steps are as follows: After bio-oxidation pretreatment of gold concentrate, without the addition of exogenous iron but only iron-based ligand oxalate, the gold leaching rate reached 90% under acidic to neutral conditions of pH 4-7 after 24 hours of leaching. Under the optimal condition of pH 5, the gold leaching rate was 96.45%, with a thiosulfate consumption rate of only 4.57%. Compared with Comparative Example 1, the gold leaching rate can be increased by 40-50 times after bio-oxidation pretreatment. Compared with Comparative Example 2, the iron-based catalytic in-situ thiosulfate leaching process not only highly matches the acidic pulp conditions of the bio-oxidation pretreatment process, but also reduces the thiosulfate consumption rate by 10-15 times while achieving comparable or even higher gold leaching results.

[0068] Example 3

[0069] (1) Based on the above conditions, the gold concentrate was subjected to biological oxidation and bacterial inactivation in the slurry, and the concentration of iron ions in the slurry was found to be 0.12 M;

[0070] (2) 0.15M disodium ethylenediaminetetraacetate and 0.03M sodium thiosulfate were added sequentially to the slurry to adjust the pH of the slurry to 3, 4, 5, 6 and 7 respectively, while keeping other leaching conditions unchanged. The results are shown in Table 7.

[0071] Table 7. Changes in gold leaching rate and thiosulfate consumption rate with pH in Example 3

[0072]

[0073] The results of multiple parallel experiments using the above steps are as follows: After bio-oxidation pretreatment of gold concentrate, without the addition of exogenous iron but only the iron-based ligand ethylenediaminetetraacetate, the gold leaching rate reached 90% under acidic to neutral conditions of pH 4-7 after leaching for 24 hours. Under the optimal condition of pH 6, the gold leaching rate was 95.86%, with a thiosulfate consumption rate of only 3.11%. Compared with Comparative Example 1, the gold leaching rate can be increased by 40-50 times after bio-oxidation pretreatment. Compared with Comparative Example 2, the iron-based catalytic in-situ thiosulfate leaching process not only highly matches the acidic pulp conditions of the bio-oxidation pretreatment process, but also reduces the thiosulfate consumption rate by 10-15 times while achieving comparable or even higher gold leaching results.

[0074] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A method for green and efficient recovery of gold from refractory gold ores, characterized in that, The method comprises the following steps: Step one, biological oxidation pretreatment of the refractory gold ore to obtain a biological oxidation ore slurry; Step two, adjusting the pH of the biological oxidation ore slurry, standing for 1-3 days to inactivate the bacteria in the biological oxidation ore slurry, then adding an appropriate amount of iron-based ligand to adjust the zeta potential of the biological oxidation ore slurry to a suitable range, and then adding an appropriate amount of thiosulfate for in-situ leaching to obtain a leaching ore slurry; Step three, filtering and separating the leaching ore slurry to obtain a gold leaching solution and a leaching residue.

2. The method of green efficient recovery of gold from refractory gold ore according to claim 1, characterized in that, The biological oxidation pretreatment comprises adding 9K culture solution to the refractory gold ore at a liquid-solid ratio of 3:1-10:1, adjusting the pH to 1-2, then inoculating an appropriate amount of bacteria, and treating at 30-45℃ for 3-10 days to obtain a biological oxidation ore slurry.

3. The method of green efficient recovery of gold from refractory gold ore according to claim 2, characterized in that, The bacteria are one or more of Acidithiobacillus ferrooxidans, Acidithiobacillus thiooxidans, Leptospirillum ferrooxidans and Sulfolobus acidocaldarius, and the inoculation amount of the bacteria is 5%-20% of the volume of the 9K culture solution.

4. The method of green efficient recovery of gold from refractory gold ore according to claim 1, characterized in that, In step two, the pH of the biological oxidation ore slurry is adjusted to 4-6.

5. The method of green efficient recovery of gold from refractory gold ore according to claim 1, characterized in that, In step two, after adding an appropriate amount of the iron-based ligand, the zeta potential of the biological oxidation ore slurry is adjusted to be stable at 200-350mV, and the addition amount of the iron-based ligand is 1-5 times the concentration of iron ions in the biological oxidation ore slurry.

6. The method of green efficient recovery of gold from refractory gold ore according to claim 1, characterized in that, The iron-based ligand includes but is not limited to citrate, ethylenediaminetetraacetate, oxalate and hydrocyanic acid salt which can coordinate with iron ions and form complexes stable under acidic conditions.

7. The method of green efficient recovery of gold from refractory gold ore according to claim 1, characterized in that, The addition amount of the thiosulfate is 0.01-0.08mol / L.

8. The method of green efficient recovery of gold from refractory gold ore according to claim 7, characterized in that, The thiosulfate includes but is not limited to sodium thiosulfate and potassium thiosulfate.

9. The method of green efficient recovery of gold from refractory gold ore according to claim 1, characterized in that, The leaching conditions of the in-situ leaching are a leaching temperature of 25-40℃, a leaching time of 8-24h, a slurry pH of 4-6.5, and a rotation speed of 250-350rpm.

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