A method for leaching a nickel-cobalt-copper sulfide ore under near-neutral pH conditions

Abstract

The application discloses a method for leaching nickel-cobalt-copper sulfide ore under near-neutral pH conditions, comprising the following steps: domestication and culture of near-neutral pH condition microbes; construction of a near-neutral biological leaching system (a biological-ligand leaching system); leaching of nickel-cobalt-copper sulfide ore; and finally obtaining a leaching solution containing valuable metal ions such as nickel, cobalt and copper. In the method, the pH value of the near-neutral microbial-ligand leaching system is 5-9, thereby avoiding the pollution risk and repair problem of a traditional acid leaching site. Meanwhile, biological oxidation avoids the use of a chemical oxidizing agent. In addition, the near-neutral environment of the method effectively overcomes the problems of a conventional acid system, such as large acid consumption and deterioration of heap permeability when leaching high calcium and magnesium alkaline gangue content nickel-cobalt-copper sulfide ore, and finally realizes selective and efficient extraction of valuable elements. The method for leaching nickel-cobalt-copper sulfide ore under near-neutral pH conditions has simple equipment, simple operation, is environment-friendly, and is conducive to industrialization popularization and application.

Description

Technical Field

[0001] This invention belongs to the field of mineral processing and hydrometallurgy, and specifically relates to a method for leaching nickel-cobalt-copper sulfide ores under near-neutral pH conditions. Background Technology

[0002] In my country, nickel, cobalt, and copper often coexist in complex and closely related environments, with high content of calcium-magnesium alkaline gangue minerals, forming high-calcium-magnesium, low-grade sulfide nickel-cobalt-copper ores, whose development and utilization are of great significance. These high-calcium-magnesium, low-grade sulfide nickel-cobalt-copper ores also generally exhibit characteristics such as large variations in oxidation rate (oxygen-sulfur mixture), high binding rate, high clay content, diverse mineral types, and fine particle size. For such ores, the traditional flotation-pyrometallurgical route is extremely difficult to achieve economical and clean efficient utilization due to poor technical indicators, high production costs, complex processes, and environmental pollution.

[0003] Biometallurgy (bioleaching) primarily involves leaching valuable metal elements under relatively mild conditions such as ambient temperature and pressure through the direct and indirect action of acidophilic microorganisms (pH typically less than 2), followed by separation and recovery from the leachate. Biometallurgy holds significant importance for the economic and clean efficient utilization of low-grade complex mineral resources due to its advantages in low cost, low carbon footprint, and environmental friendliness. However, for high-calcium and magnesium, low-grade sulfide nickel-cobalt-copper ores, traditional acidic bioleaching requires pre-acidification of the ore with large amounts of sulfuric acid. Furthermore, the significant leaching of alkaline gangue can lead to persistent deterioration of the leaching heap permeability, passivation of the valuable mineral leaching interface, and excessively high calcium and magnesium content in the leachate, presenting formidable bottlenecks and challenges. Additionally, acidic bioleaching sites subsequently exposed to acidic conditions face the risk of soil, surface water, and groundwater pollution, requiring substantial human and material resources for remediation.

[0004] Meanwhile, existing reports on bioleaching under moderately alkaline conditions mostly employ heterotrophic microorganisms, utilizing organic acids and biological ligands produced by their metabolism for leaching. However, organic acids have a weak destructive effect on the ore structure, and the production of biological ligands is extremely low, with limited binding effect on target metal ions, resulting in extremely low leaching rates and lacking commercial application value. Summary of the Invention

[0005] The purpose of this invention is to provide a method for leaching nickel-cobalt-copper ore under near-neutral pH conditions. Based on the principle of bio-oxidation-complexation / coordination synergistic reaction, this bioleaching method cleanly and efficiently leaches nickel-cobalt-copper ore, avoiding the site pollution risks associated with traditional acidic bioleaching. At the same time, this invention also avoids the large-scale dissolution of alkaline gangue during the leaching process.

[0006] This invention provides a method for leaching nickel-cobalt-copper sulfide ore under near-neutral pH conditions, comprising the following steps:

[0007] S1. Microorganisms were inoculated into a composite culture medium containing nickel-cobalt-copper sulfide ore powder for domestication and cultivation, and centrifuged to obtain bacterial sludge;

[0008] S2. The bacterial sludge obtained in step S1 is inoculated into a composite culture medium containing reduced sulfur for amplification culture, filtered, and a bacterial suspension is obtained.

[0009] S3. Add ligand to the bacterial suspension obtained in step S2, adjust the pH, and obtain the microbial-ligand extractant;

[0010] S4. Mix the nickel-cobalt-copper sulfide ore with the microbial-ligand leaching agent obtained in step S3, perform bioleaching, and then perform solid-liquid separation to obtain a leachate containing valuable nickel-cobalt-copper metal ions.

[0011] Furthermore, in step S1, the microorganisms include one or more of the following: autotrophic, heterotrophic, or facultative sulfur-oxidizing microorganisms that prefer near-neutral pH conditions.

[0012] Among them, autotrophic microorganisms include Thiomicrorhabdus, Halothiobacillus, Sulfurimonas, Mesorhizobium, Thiobacillus, Thermithiobacillus, and Thiomicrospira microorganisms;

[0013] Heterotrophic microorganisms include Bacillus, Citreicella, and Limnobacter.

[0014] Facultative microorganisms include those of the genera *Thioclava* and *Thiomonas*.

[0015] The microorganisms can oxidize reducing sulfur substances such as thiosulfates, sulfides, elemental sulfur, or tetrasulfates under conditions of pH 4–10.5, temperature -1–45℃, and salinity 0–100 g / L NaCl.

[0016] Preferably, the culture conditions for the microorganisms are: pH 5-9, temperature 25-35℃, and salinity 20-35 g / L NaCl.

[0017] The matrix of the composite culture medium containing nickel-cobalt-copper sulfide ore powder includes a carbon source, a nitrogen source, inorganic salts, vitamins, and nickel-cobalt-copper sulfide ore powder; wherein the amount of carbon source is 10-100 mmol / L based on carbon content, the amount of nitrogen source is 10-100 mmol / L based on nitrogen content, and the amount of inorganic salts meets the requirement that the content of phosphorus, potassium, magnesium, and calcium is 0.01-20 mmol / L.

[0018] The carbon source includes one or more of the following: calcium carbonate, acetic acid, succinic acid, malic acid, lactic acid, pyruvic acid, citric acid, propionic acid, butyric acid, gluconic acid, glycolic acid, glyoxylic acid, ethanol, glycerol, mannitol, sorbitol, glucose, fructose, maltose, sucrose, L-arabinose, D-cellobiose, starch, proline, lysine, alanine, glutamic acid, glutamine, aspartic acid, asparagine, leucine, and arginine.

[0019] Nitrogen sources include one or more of the following: soybean meal, corn steep liquor, yeast extract, yeast powder, nitrates, urea, and ammonium salts.

[0020] Inorganic salts include inorganic salts from carbon and nitrogen sources, potassium dihydrogen phosphate, dipotassium hydrogen phosphate, tricalcium phosphate, potassium chloride, calcium nitrate, magnesium sulfate, and sodium chloride;

[0021] Vitamins include biotin (vitamin H), pyridoxine (vitamin B6), and thiamine (vitamin B1), all of which are used in amounts of 10–100 μmol / L.

[0022] The content of nickel-cobalt-copper sulfide ore powder in the matrix of the composite culture medium containing nickel-cobalt-copper sulfide ore powder is 1-20 g / L.

[0023] The composite culture medium containing nickel-cobalt-copper sulfide ore powder is prepared from deionized water or artificial seawater. Specifically, the artificial seawater composition is as follows: NaCl 26.726 g / L, MgCl2 2.26 g / L, MgSO4 3.248 g / L, CaCl2 1.153 g / L, NaHCO3 0.198 g / L, KCl 0.721 g / L, NaBr 0.058 g / L, H3BO3 0.058 g / L, Na2SiO3 0.0024 g / L, Na2Si4O9 0.0015 g / L, H3PO4 0.002 g / L, Al2Cl6 0.013 g / L, NH3 0.002 g / L, LiNO3 0.0013 g / L.

[0024] The acclimatization and cultivation process conditions are as follows: cultivation time is 10 to 60 days, cultivation temperature is 25 to 35°C, pH is adjusted to 5 to 9 using 1 mol / L hydrochloric acid and 1 mol / L sodium hydroxide solution, acclimatization is carried out in a shake flask at a speed of 160 to 180 rpm, and aeration is not required;

[0025] The centrifugation speed is 9000-11000 rpm, and the time is 18-22 minutes.

[0026] Furthermore, in step S2, the matrix of the composite culture medium containing reducing sulfur includes a carbon source, a nitrogen source, inorganic salts, vitamins, and reducing sulfur substances, wherein the carbon source, nitrogen source, inorganic salts, vitamins, and their preparation method are the same as those in the composite culture medium containing nickel-cobalt-copper sulfide ore powder in step S1.

[0027] The reducing sulfur substance includes one or more of sodium thiosulfate, pyrite, and elemental sulfur; the content of the reducing sulfur substance in the composite culture medium containing reducing sulfur is 1-20 g / L.

[0028] The amplification culture process conditions are as follows: culture time is 1 to 10 days, culture temperature is 25 to 35°C, pH is adjusted to 5 to 9 using 1 mol / L hydrochloric acid and 1 mol / L sodium hydroxide solution, amplification culture is carried out in a shake flask at a speed of 170 rpm, and no aeration is required.

[0029] The viable count of the bacterial suspension is 10. 9 ~10 10 pcs / ml;

[0030] Furthermore, in step S3, the ligand includes one or more of aspartic acid, glycine, citric acid and its salts, hypozinotriacetic acid and its salts, iminodiacetic acid and its salts, ethylenediaminetetraacetic acid and its salts, diethylenetriamine, and diethylenetriaminepentaacetic acid.

[0031] After the addition of the ligand, the concentration of the ligand in the solution is 1–50 g / L.

[0032] After mixing, adjust the pH range to 5–9;

[0033] Furthermore, in step S4, the bioleaching process conditions are as follows: liquid-to-solid ratio of 10:(0.1-3), leaching time of 10-60 days, leaching temperature of 25-35℃, pH adjusted to 5-9 using 1 mol / L hydrochloric acid and 1 mol / L sodium hydroxide solution, leaching carried out in a shake flask at a rotation speed of 200 rpm, without aeration. The principle of this invention:

[0034] This invention utilizes the sulfur oxidation capacity of microbial metabolic activities to disrupt the crystal structure of nickel-cobalt-copper sulfide ores. Then, it selectively combines biological metabolites and added ligands with released valuable metal ions to ensure their stable existence in a near-neutral solution environment. This invention combines biological oxidation with the combination of valuable metal ions with biological or chemical ligands, achieving the bioleaching of metal sulfides under near-neutral conditions. This avoids the bottlenecks and challenges that are difficult to overcome in conventional acidic systems, such as large acid consumption, continuous deterioration of the permeability of the leaching pile, passivation of the leaching interface of valuable minerals, and excessively high calcium and magnesium content in the leachate. It also avoids the pollution risks and remediation problems of acidic sites after leaching.

[0035] The beneficial effects of this invention are:

[0036] (1) The method of the present invention utilizes the synergistic effect of biological oxidation, biological metabolites and chemical ligands under near-neutral conditions to avoid the pollution risk and remediation problem of acidic sites after leaching.

[0037] (2) The method of the present invention achieves selective and efficient extraction of valuable elements in sulfide nickel-cobalt-copper ores with high calcium and magnesium content in alkaline gangue, effectively overcoming the difficult problems of large acid consumption, continuous deterioration of the permeability of the leaching pile, passivation of the leaching interface of valuable minerals, and excessive calcium and magnesium content in the leaching solution in conventional acidic systems.

[0038] (3) The microorganisms used in this invention are widely found in nature and have the advantages of being green, environmentally friendly, and low-cost;

[0039] (4) The biological oxidation method of the present invention replaces the use of chemical oxidants, which can effectively alleviate environmental pollution pressure and achieve clean and efficient extraction of valuable elements in nickel-cobalt-copper sulfide ores.

[0040] (5) The microorganisms used in this invention generally have high NaCl tolerance, so seawater can be used instead of fresh water during the leaching process, which is beneficial to saving fresh water resources;

[0041] (6) The method for leaching nickel-cobalt-copper sulfide ore under near-neutral conditions of the present invention uses simple equipment, is easy to operate, is environmentally friendly, and is conducive to industrial promotion and application. Detailed Implementation

[0042] To make the technical means, creative features, objectives, and effects of this invention readily understandable, the invention is further described below with reference to specific embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0043] In this invention, the liquid-to-solid ratio is expressed in mL / g, and the grade is the mass fraction of the element.

[0044] The selected No. 1 nickel-cobalt-sulfide copper ore has the following grades: Ni 1.01%, Co 0.05%, Cu 1.26%, Mg 19.2%; the selected No. 2 nickel-cobalt-sulfide copper ore has the following grades: Ni 1.69%, Co 0.07%, Cu 0.38%, Mg 15.0%. Both are crushed and finely ground to less than 200 mesh, and 1-30g are evenly taken and placed in a 250mL conical flask.

[0045] Example 1

[0046] Halothiobacillus neapolitanus MCCC 1A18420 was inoculated into a composite culture medium containing nickel-cobalt-copper sulfide ore powder prepared with deionized water. The medium was acclimatized and cultured at pH 7 for 15 days. The culture was then filtered and centrifuged to obtain bacterial sludge. The specific formula of the composite culture medium containing nickel-cobalt-copper sulfide ore powder prepared with deionized water was: (NH4)2SO4 3.0 g / L, MgSO47H2O 0.5 g / L, K2HPO4 0.5 g / L, KCl 0.1 g / L, Ca(NO3)2 0.01 g / L, NaCl 25 g / L, yeast extract 0.2 g / L, and No. 1 ore powder 20 g / L.

[0047] The bacterial sludge was then inoculated into a composite culture medium containing reducing sulfur prepared with deionized water for amplification culture for 7 days, and the bacterial suspension was obtained by filtration (bacterial concentration not less than 3.0 × 10⁸ cells / mL); the specific formula of the composite culture medium containing reducing sulfur prepared with deionized water is as follows: (NH₄)₂SO₄ 3.0 g / L, MgSO₄7H₂O 0.5 g / L, K₂HPO₄ 0.5 g / L, KCl 0.1 g / L, Ca(NO₃)₂ 0.01 g / L, NaCl 25 g / L, yeast extract powder 0.2 g / L, sodium thiosulfate 3 g / L;

[0048] A microbial-ligand leaching agent was prepared by adding 1 g of iminodiacetic acid ligand to 100 mL of bacterial suspension and adjusting the pH to 7. Then, the ore was leached using the microbial-ligand leaching agent at a leaching solution-to-solid ratio of 100:1 (for No. 1 nickel-cobalt-sulfide ore). The leaching process was carried out in a constant-temperature shaker at 30℃ and 200 rpm. The leaching solution was collected after 20 days. ICP-AES analysis of the leaching solution showed that the leaching rates of Ni, Co, and Cu were 80.6%, 77.1%, and 35.7%, respectively, while the leaching rate of the impurity element Mg was only 3.0%.

[0049] Example 2

[0050] The same microbial suspension as in Example 1 was used to leach No. 2 nickel-cobalt-copper sulfide ore using the same leaching process as in Example 1, yielding a leachate. ICP-AES analysis of the leachate showed leaching rates of 82.1% for Ni, 74.9% for Co, and 32.3% for Cu, while the leaching rate of the impurity element Mg was only 4.0%.

[0051] Comparative Example 1

[0052] Take 100 mL of sterile culture medium, add 1 g of iminodiacetic acid ligand, adjust the pH to 7 to prepare a chemical leaching agent, and leach the ore according to the same leaching process as in Example 1. The leaching solution was tested by ICP-AES, and the leaching rates of Ni, Co and Cu were 40.2%, 37.4% and 15.0%, respectively.

[0053] Comparative Example 2

[0054] 100 mL of the same microbial suspension as in Example 1 was taken without the addition of ligands and the ore was leached using the same leaching process as in Example 1. The leaching solution was tested by ICP-AES and the leaching rates of Ni, Co and Cu were found to be 0.3%, 0.01% and 0%, respectively.

[0055] Based on the results of Examples 1, 2, 1, and 2, we can see that the leaching effects of Examples 1 and 2 are similar and significantly better than those of Comparative Examples 1 and 2. This indicates that the bio-ligand leaching agent composed of *Salmonella naples* combined with iminodiacetic acid ligand has a synergistic effect. Furthermore, the similar effects on nickel-cobalt-copper sulfide ores No. 1 and No. 2 demonstrate the stability and universality of this bio-leaching agent.

[0056] Example 3

[0057] A mixture of *Citreicella thiooxidans* MCCC 1A13021 and *Thioclavapacifica* MCCC 1A03188 was inoculated into a composite culture medium containing nickel-cobalt-copper sulfide ore powder prepared with artificial seawater and acclimated at pH 7 for 20 days. The culture was then filtered and centrifuged to obtain bacterial sludge. The specific formula of the composite culture medium containing nickel-cobalt-copper sulfide ore powder prepared with artificial seawater was as follows: (NH4)2SO4 3.0 g / L, K2HPO4 0.5 g / L, citric acid 5 g / L, soybean meal 0.5 g / L, and No. 2 mineral powder 50 g / L were added to the artificial seawater.

[0058] The bacterial sludge was then inoculated into a composite culture medium containing reduced sulfur prepared from artificial seawater and cultured for 7 days. The culture was then filtered to obtain a bacterial suspension (bacterial concentration approximately 3.0 × 10⁻⁶). 9(number / mL); the specific formula of the composite culture medium containing reduced sulfur prepared from artificial seawater is as follows: on the basis of artificial seawater, add (NH4)2SO4 3.0 g / L, K2HPO4 0.5 g / L, citric acid 5 g / L, soybean meal powder 0.5 g / L, sodium thiosulfate 3 g / L and elemental sulfur 5 g / L.

[0059] A microbial-ligand leaching agent was prepared by adding 1g of iminodiacetic acid ligand and 1g of sodium ethylenediaminetriacetate ligand to 100mL of bacterial suspension and adjusting the pH to 7. Then, the ore was leached using the microbial-ligand leaching agent at a solid-liquid ratio of 100:2 (for No. 1 nickel-cobalt-sulfide ore). The leaching process was carried out in a constant-temperature shaker at 35℃ and 200rpm. The leachate was collected after 20 days of leaching. ICP-AES analysis of the leachate showed that the leaching rates of Ni, Co, and Cu were 88.9%, 87.4%, and 40.1%, respectively, while the leaching rate of the impurity element Mg was only 5.2%.

[0060] Example 4

[0061] The same microbial suspension as in Example 3 was used to leach No. 2 nickel-cobalt-copper sulfide ore using the same leaching process as in Example 3, yielding a leachate. ICP-AES analysis of the leachate showed leaching rates of 90.4% for Ni, 89.9% for Co, and 45.1% for Cu, while the leaching rate of the impurity element Mg was only 4.9%.

[0062] Comparative Example 3

[0063] Take 100 mL of sterile culture medium, add 1 g of iminodiacetic acid ligand and 1 g of sodium ethylenediaminetriacetate ligand, adjust the pH to 7 to prepare a chemical leaching agent, and leach the ore according to the same leaching process as in Example 3. The leaching solution was tested by ICP-AES, and the leaching rates of Ni, Co and Cu were 58.7%, 57.6% and 35.6%, respectively.

[0064] Comparative Example 4

[0065] 100 mL of the same microbial suspension as in Example 3 was taken without the addition of ligands and the ore was leached using the same leaching process as in Example 3. The leaching solution was tested by ICP-AES, and the leaching rates of Ni, Co and Cu were found to be 0.5%, 0.1% and 0.1%, respectively.

[0066] Combining the results of Examples 3 and 4, and Comparative Examples 3 and 4, we can see that the leaching effects of Examples 3 and 4 are similar and significantly better than those of Comparative Examples 3 and 4. This indicates that the bio-ligand leaching agent composed of a mixture of *Citrus sulfadiazine* and *Bacillus thuringiensis*, along with iminodiacetic acid ligands and sodium ethylenediaminetriacetate ligands, has a synergistic effect. Furthermore, the similar effects on nickel-cobalt-copper sulfide ores No. 1 and No. 2 demonstrate the stability and universality of this bio-leaching agent. In addition, Examples 3 and 4 demonstrate the feasibility of using seawater instead of freshwater to prepare the culture medium.

[0067] Example 5

[0068] Thiomicrobacterium sediminis MCCC 1A14511, Sulfurimonas lithotrophica MCCC 1A14739, and Citreicella thiooxidans MCCC 1A13021 were inoculated into a composite culture medium containing nickel-cobalt-copper sulfide ore powder and acclimated at pH 7.8 for 20 days. The resulting bacterial sludge was obtained by filtration and centrifugation. The specific formula of the composite culture medium containing nickel-cobalt-copper sulfide ore powder was as follows: (NH4)2SO4 3.0 g / L, MgSO47H2O 0.5 g / L, K2HPO4 0.5 g / L, KCl 0.1 g / L, Ca(NO3)2 0.01 g / L, NaCl 20 g / L, acetic acid 3 g / L, yeast extract 0.5 g / L, and No. 1 ore powder 20 g / L.

[0069] The bacterial sludge was then inoculated into a composite medium containing reducing sulfur for amplification culture for 7 days, and the bacterial suspension was obtained by filtration (bacterial concentration of approximately 2.0 × 10⁹ CFU / mL). The specific formula of the composite medium containing reducing sulfur was as follows: (NH₄)₂SO₄ 3.0 g / L, MgSO₄·7H₂O 0.5 g / L, K₂HPO₄ 0.5 g / L, KCl 0.1 g / L, Ca(NO₃)₂ 0.01 g / L, NaCl 20 g / L, acetic acid 3 g / L, yeast extract 0.5 g / L, and elemental sulfur 10 g / L.

[0070] 2g of sodium ethylenediaminetriacetate ligand was added to 100mL of bacterial suspension to adjust the pH to 7.8, thus preparing a microbial-ligand leaching agent. Then, the ore was leached using the microbial-ligand leaching agent at a leaching solution-to-solid ratio of 100:1 (for No. 1 nickel-cobalt-sulfide ore). The leaching process was carried out in a constant-temperature shaker at 28℃ and 200rpm. The leaching solution was collected after 50 days. ICP-AES analysis of the leaching solution showed that the leaching rates of Ni, Co, and Cu were 83.6%, 81.7%, and 39.9%, respectively, while the leaching rate of the impurity element Mg was only 6.3%.

[0071] Example 6

[0072] The same microbial suspension as in Example 5 was used to leach No. 2 nickel-cobalt-copper sulfide ore using the same leaching process as in Example 5, yielding a leachate. ICP-AES analysis of the leachate showed leaching rates of 89.7% for Ni, 87.4% for Co, and 42.1% for Cu, while the leaching rate of the impurity element Mg was only 5.8%.

[0073] Comparative Example 5

[0074] Take 100 mL of sterile culture medium, add 2 g of sodium ethylenediaminetriacetate ligand, adjust the pH to 7.8 to prepare a chemical leaching agent, and leach the ore according to the same leaching process as in Example 5. The leaching solution was tested by ICP-AES, and the leaching rates of Ni, Co and Cu were 50.3%, 51.6% and 33.1%, respectively.

[0075] Comparative Example 6

[0076] 100 mL of the same microbial suspension as in Example 5 was taken without the addition of ligands and the ore was leached using the same leaching process as in Example 5. The leaching solution was tested by ICP-AES, and the leaching rates of Ni, Co and Cu were found to be 0.6%, 0.2% and 0.1%, respectively.

[0077] Based on the results of Examples 5, 6, 5, and 6, we can see that the leaching effects of Examples 5 and 6 are similar and significantly better than those of Comparative Examples 5 and 6. This indicates that the bio-ligand leaching agent composed of a mixture of sediment-derived Thiobacillus, inorganic nutrient Thiobacillus, and sulfur-oxidizing Lemonobacterium, combined with sodium ethylenediaminetriacetate ligand, has a synergistic effect. Furthermore, the similar effects on No. 1 and No. 2 sulfide nickel-cobalt-copper ores demonstrate the stability and universality of this bio-leaching agent.

[0078] Example 7

[0079] Thioclavia pacifica MCCC 1A03188, Thioclavia sediminis MCCC 1A14511, Sulfurimonas lithotrophica MCCC 1A14739, Citreicella thiooxidans MCCC 1A13021, and a mixture of Halothiobacillus neapolitanus MCCC 1A18420 were inoculated into a composite medium containing nickel-cobalt-copper sulfide ore powder. The medium was acclimatized and cultured at pH 7.5 for 20 days. The resulting bacterial sludge was obtained by filtration and centrifugation. The specific formulation of the composite medium containing nickel-cobalt-copper sulfide ore powder was: (NH4)2SO4 3.0 g / L, MgSO4·7H2O 0.5 g / L, K2HPO4 0.5 g / L, KCl... 0.1 g / L, Ca(NO3)2 0.01 g / L, NaCl 25 g / L, acetic acid 5 g / L, yeast extract 0.5 g / L, No. 1 mineral powder 50 g / L;

[0080] The bacterial sludge was then inoculated into a composite medium containing reducing sulfur for amplification culture for 10 days, and the bacterial suspension was obtained by filtration (bacterial concentration of approximately 4.0 × 10⁹ cells / mL). The specific formula of the composite medium containing reducing sulfur was as follows: (NH₄)₂SO₄ 3.0 g / L, MgSO₄·7H₂O 0.5 g / L, K₂HPO₄ 0.5 g / L, KCl 0.1 g / L, Ca(NO₃)₂ 0.01 g / L, NaCl 25 g / L, acetic acid 5 g / L, yeast extract 0.5 g / L, sodium thiosulfate 3 g / L, and pyrite 5 g / L.

[0081] A microbial-ligand leaching agent was prepared by adding 1 g of sodium ethylenediaminetriacetate ligand and 1.5 g of glycine ligand to 100 mL of bacterial suspension and adjusting the pH to 7.5. Then, the ore was leached using the microbial-ligand leaching agent at a solid-liquid ratio of 100:5 (for No. 1 nickel-cobalt-sulfide ore). The leaching process was carried out in a constant-temperature shaker at 30℃ and 200 rpm. The leachate was collected after 50 days of leaching. ICP-AES analysis of the leachate showed that the leaching rates of Ni, Co, and Cu were 85.0%, 83.3%, and 45.7%, respectively, while the leaching rate of the impurity element Mg was only 6.5%.

[0082] Example 8

[0083] The same microbial suspension as in Example 7 was used to leach No. 2 nickel-cobalt-copper sulfide ore using the same leaching process as in Example 7, resulting in a leachate. ICP-AES analysis of the leachate showed leaching rates of 88.8% for Ni, 87.9% for Co, and 46.0% for Cu, while the leaching rate of the impurity element Mg was only 6.0%.

[0084] Comparative Example 7

[0085] Take 100 mL of sterile culture medium, add 1 g of sodium ethylenediaminetriacetate ligand and 1.5 g of glycine ligand, adjust the pH to 7.5 to prepare a chemical leaching agent, and leach the ore according to the same leaching process as in Example 7. The leaching solution was tested by ICP-AES, and the leaching rates of Ni, Co and Cu were 50.5%, 48.1% and 30.2%, respectively.

[0086] Comparative Example 8

[0087] 100 mL of the same microbial suspension as in Example 7 was taken without the addition of ligands and the ore was leached using the same leaching process as in Example 7. The leaching solution was tested by ICP-AES, and the leaching rates of Ni, Co and Cu were found to be 0.6%, 0.3% and 0.1%, respectively.

[0088] Based on the results of Examples 7, 8, 7, and 8, we can see that the leaching effects of Examples 7 and 8 are similar and significantly better than those of Comparative Examples 7 and 8. This indicates that the bio-ligand leaching agent composed of a mixture of *Thiobacillus paclitaxel*, *Thiobacillus thuringiensis*, *Thiomonas hydrophila*, *Citrus thiooxidans*, and *Thiobacillus naples*, combined with sodium ethylenediaminetriacetate ligand and glycine ligand, has a synergistic effect. The similar effects on sulfide nickel-cobalt-copper ores No. 1 and No. 2 demonstrate the stability and universality of this bio-leaching agent.

Claims

1. A method for leaching nickel-cobalt-copper sulfide ores under near-neutral pH conditions, characterized in that, Includes the following steps: S1. Microorganisms were inoculated into a composite culture medium containing nickel-cobalt-copper sulfide ore powder for domestication and cultivation, and centrifuged to obtain bacterial sludge; S2. The bacterial sludge obtained in step S1 is inoculated into a composite culture medium containing reduced sulfur for amplification culture, filtered, and a bacterial suspension is obtained. S3. Add ligand to the bacterial suspension obtained in step S2, adjust the pH, and obtain the microbial-ligand extractant; S4. Mix the nickel-cobalt-copper sulfide ore with the microbial-ligand leaching agent obtained in step S3, perform bioleaching, and then perform solid-liquid separation to obtain a leachate containing valuable nickel-cobalt-copper metal ions. In step S1, the microorganisms include one or more of the following: autotrophic sulfur-oxidizing microorganisms, heterotrophic sulfur-oxidizing microorganisms, or facultative sulfur-oxidizing microorganisms that prefer near-neutral pH conditions. In step S3, the ligand includes one or more of aspartic acid, glycine, citric acid and its salts, hypozinotriacetic acid and its salts, iminodiacetic acid and its salts, ethylenediaminetetraacetic acid and its salts, diethylenetriamine, and diethylenetriaminepentaacetic acid.

2. The method for leaching nickel-cobalt-copper sulfide ore under near-neutral pH conditions according to claim 1, characterized in that, The microorganisms can oxidize thiosulfates, sulfides, elemental sulfur, or tetrasulfates under conditions of pH 4 to 10.5, temperature -1 to 45°C, and salinity 0 to 100 g / L NaCl.

3. The method for leaching nickel-cobalt-sulfide copper ore under near-neutral pH conditions according to claim 1, characterized in that, The matrix of the composite culture medium containing nickel-cobalt-copper sulfide ore powder includes a carbon source, a nitrogen source, inorganic salts, vitamins, and nickel-cobalt-copper sulfide ore powder; wherein the amount of carbon source is 10~100 mmol / L based on carbon content, the amount of nitrogen source is 10~100 mmol / L based on nitrogen content, and the amount of inorganic salts meets the requirement that the content of phosphorus, potassium, magnesium, and calcium is 0.01~20 mmol / L.

4. The method for leaching nickel-cobalt-sulfide copper ore under near-neutral pH conditions according to claim 3, characterized in that, Carbon sources include one or more of the following: calcium carbonate, acetic acid, succinic acid, malic acid, lactic acid, pyruvic acid, citric acid, propionic acid, butyric acid, gluconic acid, glycolic acid, glyoxylic acid, ethanol, glycerol, mannitol, sorbitol, glucose, fructose, maltose, sucrose, L-arabinose, D-cellobiose, starch, proline, lysine, alanine, glutamic acid, glutamine, aspartic acid, asparagine, leucine, and arginine. Nitrogen sources include one or more of the following: soybean meal, corn steep liquor, yeast extract, yeast powder, nitrates, urea, and ammonium salts. Vitamins include vitamin H, vitamin B6, and vitamin B1, and the dosage is 10~100μmol / L; The content of nickel-cobalt-copper sulfide ore powder in the matrix of the composite culture medium containing nickel-cobalt-copper sulfide ore powder is 1~20 g / L; The composite culture medium containing nickel-cobalt-copper sulfide ore powder is prepared from deionized water or artificial seawater.

5. The method for leaching nickel-cobalt-sulfide copper ore under near-neutral pH conditions according to claim 4, characterized in that, The artificial seawater composition is as follows: NaCl 26.726 g / L, MgCl2 2.26 g / L, MgSO4 3.248 g / L, CaCl2 1.153 g / L, NaHCO3 0.198 g / L, KCl 0.721 g / L, NaBr 0.058 g / L, H3BO3 0.058 g / L, Na2SiO3 0.0024 g / L, Na2Si4O9 0.0015 g / L, H3PO4 0.002 g / L, Al2Cl6 0.013 g / L, NH3 0.002 g / L, LiNO3 0.0013 g / L.

6. The method for leaching nickel-cobalt-copper sulfide ore under near-neutral pH conditions according to claim 1, characterized in that, The acclimatization and cultivation process conditions are as follows: cultivation time is 10-60 days, cultivation temperature is 25-35℃, pH is adjusted to 5-9 using 1 mol / L hydrochloric acid and 1 mol / L sodium hydroxide solution, acclimatization is carried out in a shake flask at a speed of 160-180 rpm, and aeration is not required; The centrifugation speed is 9000~11000 rpm, and the time is 18~22 minutes.

7. The method for leaching nickel-cobalt-sulfide copper ore under near-neutral pH conditions according to claim 1, characterized in that, In step S2, the matrix of the composite culture medium containing reduced sulfur includes a carbon source, a nitrogen source, inorganic salts, vitamins, and reduced sulfur substances, wherein the carbon source, nitrogen source, inorganic salts, vitamins, and their preparation methods are the same as those in the composite culture medium containing nickel-cobalt-copper sulfide ore powder in step S1. The reducing sulfur substance includes one or more of sodium thiosulfate, pyrite, and elemental sulfur; the content of the reducing sulfur substance in the composite culture medium containing reducing sulfur is 1~20 g / L; The amplification culture process conditions are as follows: culture time is 1 to 10 days, culture temperature is 25 to 35°C, pH is adjusted to 5 to 9 using 1 mol / L hydrochloric acid and 1 mol / L sodium hydroxide solution, amplification culture is carried out in a shake flask at a speed of 170 rpm, and no aeration is required; The viable count of the bacterial suspension is 10. 9 ~10 10 per milliliter.

8. The method for leaching nickel-cobalt-copper sulfide ore under near-neutral pH conditions according to claim 1, characterized in that, After adding the ligand, the concentration of the ligand in the solution is 1~50g / L; after mixing, the pH range is adjusted to 5~9.

9. The method for leaching nickel-cobalt-copper sulfide ore under near-neutral pH conditions according to claim 1, characterized in that, In step S4, the process conditions for bioleaching are as follows: liquid-to-solid ratio of 10:(0.1~3), leaching time of 10~60 days, leaching temperature of 25~35℃, pH adjusted to 5~9 using 1 mol / L hydrochloric acid and 1 mol / L sodium hydroxide solution, leaching is carried out in a shake flask at a rotation speed of 200 rpm, and aeration is not required.