Method for bioleaching of low-grade copper ores

Abstract

This application provides a bioleaching method for low-grade copper ore, comprising the following steps: crushing copper-bearing ore and pyrite separately, screening to obtain copper ore powder and iron ore powder, mixing the copper ore powder and iron ore powder and piling them in a heap leaching column, and burying vertical pipes in the heap to obtain a heap; spraying the heap with acid, then inoculating with leaching bacteria solution to carry out the heap leaching process; the leaching process uses raffinate for circulating leaching. The method of this application uses bioleaching to treat low-grade copper ore, which has the advantages of high leaching rate, low pollution, water conservation, and ease of operation. It overcomes the disadvantages of traditional flotation methods for separating low-grade copper ore, which are not only difficult to process but also have extremely low flotation yields, making it difficult to obtain high-grade copper concentrate.

Description

Technical Field

[0001] This application relates to the field of bioleaching technology, and in particular to a bioleaching method for low-grade copper ore. Background Technology

[0002] Copper, as a primary raw material for modern industrial development, is a vital strategic resource for nations. Its applications in manufacturing are widespread, encompassing light industry, machinery, electrical engineering, defense, and construction. Copper ore, the world's third most consumed metal, typically exists in the Earth's crust as sulfide minerals, with chalcopyrite being the most common. Flotation is the primary method for beneficiating chalcopyrite to achieve enrichment. Pyrometallurgical copper smelting is the main method for processing chalcopyrite flotation concentrates; however, traditional pyrometallurgical processes cause severe air pollution. Furthermore, pyrometallurgical beneficiation processes are complex, requiring large quantities of flotation reagents and generating significant amounts of wastewater, resulting in severe environmental pollution. The smelting process is also energy-intensive. Moreover, separating low-grade copper ore using flotation is not only difficult but also yields extremely low flotation returns, making it challenging to obtain high-grade copper concentrates. Summary of the Invention

[0003] This application provides a bioleaching method for low-grade copper ore to solve the problems of high processing difficulty and extremely low flotation yield when separating low-grade copper ore using traditional flotation methods, making it difficult to obtain high-grade copper concentrate.

[0004] This application provides a method for bioleaching low-grade copper ore, comprising the following steps:

[0005] The copper-bearing ore and pyrite are crushed and sieved to obtain copper ore powder and iron ore powder. They are then mixed and piled in a heap leaching column, and vertical pipes are buried in the ore pile to obtain the ore pile.

[0006] The leaching process involves spraying the ore pile with acid and then inoculating it with leaching bacteria solution.

[0007] The leaching process utilizes raffinate for circulating leaching operations;

[0008] The copper ion concentration of the leachate is sampled and analyzed periodically. When the copper ion concentration of the leachate is greater than 1.13 g / L, the leachate is extracted for further extraction. The raffinate after extraction is returned to the ore pile for continued drip leaching. When the copper ion concentration of the leachate is less than 1.13 g / L, the leachate is directly returned to the ore pile for continued drip leaching.

[0009] The method described in this application has the following beneficial effects:

[0010] 1) The method of this application utilizes the bio-oxidation of leaching microorganisms to convert copper elements in copper ore into copper ions for leaching. This method eliminates the need for expensive flotation reagents, and the leaching solution is recycled after extraction, thus saving water resources and reducing or even eliminating wastewater generation and discharge. Furthermore, the method eliminates the need for complex operations such as aeration and stirring during copper leaching, thus also saving energy and simplifying the operation process.

[0011] 2) In this application, a circulating leaching process is employed. When the leaching solution is returned to the ore heap, its pH value, iron ion concentration, and trace element content are all within a relatively stable range. Through continuous circulation, this system can effectively buffer drastic changes in the composition of the leaching solution caused by fluctuations in mineral dissolution, thereby maintaining the pH value and redox potential within the ore heap at levels most suitable for the growth and metabolic activities of leaching microorganisms. This stable environment ensures the high activity and sustainability of the microbial community, avoiding the inhibition or death of microbial activity due to sudden environmental changes, thus guaranteeing efficient copper ore leaching.

[0012] 3) In this application, the raffinate generated during the extraction process is reused as the main leaching agent for heap dripping, realizing the recycling of the leaching agent within the system. This recycling method significantly reduces the amount of fresh acid and process water replenishment, thereby reducing reagent costs and water consumption in the leaching process. Simultaneously, the raffinate itself contains residual sulfuric acid, iron ions dissolved from the heap, and trace elements required for microbial growth. Returning it to the system not only recovers these valuable components but also maintains the chemical stability of the leaching system.

[0013] Optionally, both copper ore powder and iron ore powder are passed through a 30mm sieve, and the proportion of 20-30mm particles in the copper ore powder and iron ore powder is greater than 30%, while the proportion of -5mm particles is less than 10%.

[0014] The proportion of iron ore powder added to the ore pile is 5-10%.

[0015] Optionally, the acid solution is sulfuric acid with a concentration of 6~12g / L, and the pH of the leaching bacteria solution is 1.8~2.0.

[0016] Optionally, the leaching bacteria include *Thiobacillus ferrooxidans*, and the leaching bacteria solution is selected and propagated by the following method:

[0017] The *Acidithiobacillus ferrooxidans* strain was cultured in 9K medium for 10... 7 The concentration of cfu / ml was used to obtain the culture solution.

[0018] After sterilizing five 250mL Erlenmeyer flasks at high temperature, 10mL of the culture solution was placed in each flask and added to 90mL of sterile selective culture medium. 50wt%H2SO4 was added to adjust the pH to 1.8. The flasks were then placed in a constant temperature shaker and cultured at a temperature of 35~40℃ and a rotation speed of 150r / min.

[0019] In the previous generation, choose the darkest color, Fe 2+ The strain with the highest conversion rate was enriched for three generations. The enriched leaching bacteria were then subcultured for a total of six generations at inoculum rates of 10%, 9%, 8%, 7%, 6%, and 5% of the previous generation to obtain a pure strain.

[0020] After propagating the pure strain, a mineral leaching bacterial solution with an inoculation rate of 15-20% was prepared.

[0021] Optionally, the selection medium includes a first culture medium and a second culture medium;

[0022] The first culture medium consists of 0.1g KCl, 3.0g (NH4)2SO4, 0.5g MgSO4·7H2O, 0.5g K2HPO4, and 0.01g Ca(NO3)2 dissolved in 800mL deionized water, and 50wt% H2SO4 is added dropwise to adjust the pH to 2.0.

[0023] The second culture medium consists of 44.2g FeSO4·7H2O dissolved in 200mL deionized water, and 50wt% H2SO4 added dropwise to adjust the pH to 2.0;

[0024] The first and second culture solutions were mixed and sterilized to obtain the selection culture medium.

[0025] Optionally, the specifications of the heap leaching column are Φ1.5×10.0m, the height of the ore heap is 1~9m, and the distribution density of the vertical pipes is 8~10 pipes / m. 2 All of them have equally spaced openings on the side.

[0026] Optionally, during the leaching process, the dripping rate is 8~12 L / m³. 2 • h, initially the dripping period is 72~80h, the interval is 45~48h, repeated 3~5 times, then the dripping period is 40~48h, the interval is 40~48h until the dripping ends;

[0027] During each interval of the leaching process, ventilation is provided into the ore pile once through a vertical pipe, with a ventilation rate of 12-14 L / m³. 2 •h, the duration of a single ventilation session is 2~2.5h.

[0028] Optionally, the leachate may be extracted using an extractant formulated from one or more of hydroxamic acid, aldoxime, ketoxime and amine oxime.

[0029] Optionally, the pH of the raffinate is maintained at 1.8 to 2.0.

[0030] Optionally, the temperature of the ore pile is maintained at 35-40°C during the leaching process. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application are described clearly and completely below. Obviously, the described embodiments are only some, not all, of the embodiments of this application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without creative effort are also within the scope of protection of this application.

[0032] This application provides a method for bioleaching low-grade copper ore, comprising the following steps:

[0033] The copper-bearing ore and pyrite are crushed and sieved to obtain copper ore powder and iron ore powder. The copper ore powder and iron ore powder are mixed and piled in a heap leaching column, and vertical pipes are buried in the ore pile to obtain the ore pile.

[0034] The leaching process involves spraying the ore pile with acid and then inoculating it with leaching bacteria solution.

[0035] The leaching process utilizes raffinate for circulating leaching operations;

[0036] The copper ion concentration of the leachate is sampled and analyzed periodically. When the copper ion concentration of the leachate is greater than 1.13 g / L, the leachate is extracted for further extraction. The raffinate after extraction is returned to the ore pile for continued drip leaching. When the copper ion concentration of the leachate is less than 1.13 g / L, the leachate is directly returned to the ore pile for continued drip leaching.

[0037] In this application, after copper ore powder and iron ore powder are mixed in a certain proportion, an ultrasonic operation is performed. The mixed copper ore powder and iron ore powder are placed in water and treated with an ultrasonic frequency of 24~40kHz for 0.5~1h.

[0038] It should also be noted that when unqualified leachate is returned for dripping, the same dripping system as that for raffinate is adopted. Unqualified leachate can be dripped alone or mixed with raffinate for dripping.

[0039] The copper ore referred to in this application is copper waste rock or primary sulfide copper ore with a grade of 0.130~0.5%.

[0040] The method described in this application has the following beneficial effects:

[0041] 1) The method of this application utilizes the bio-oxidation of leaching microorganisms to convert copper elements in copper ore into copper ions for leaching. This method eliminates the need for expensive flotation reagents, and the leaching solution is recycled after extraction, thus saving water resources and reducing or even eliminating wastewater generation and discharge. Furthermore, the method eliminates the need for complex operations such as aeration and stirring during copper leaching, thus also saving energy and simplifying the operation process.

[0042] 2) In this application, a circulating leaching process is employed. When the leaching solution is returned to the ore heap, its pH value, iron ion concentration, and trace element content are all within a relatively stable range. Through continuous circulation, this system can effectively buffer drastic changes in the composition of the leaching solution caused by fluctuations in mineral dissolution, thereby maintaining the pH value and redox potential within the ore heap at levels most suitable for the growth and metabolic activities of leaching microorganisms. This stable environment ensures the high activity and sustainability of the microbial community, avoiding the inhibition or death of microbial activity due to sudden environmental changes, thus guaranteeing efficient copper ore leaching.

[0043] 3) In this application, the raffinate generated during the extraction process is reused as the main leaching agent for heap dripping, realizing the recycling of the leaching agent within the system. This recycling method significantly reduces the amount of fresh acid and process water replenishment, lowering reagent costs and water consumption in the leaching process. Simultaneously, the raffinate itself contains residual sulfuric acid, iron ions dissolved from the heap, and trace elements required for microbial growth. Returning it to the system not only recovers these valuable components but also maintains the chemical stability of the leaching system.

[0044] Optionally, both copper ore powder and iron ore powder are passed through a 30mm sieve, and the proportion of 20-30mm particles in the copper ore powder and iron ore powder is greater than 30%, while the proportion of -5mm particles is less than 10%.

[0045] The proportion of iron ore powder added to the ore pile is 5-10%.

[0046] In this application, both copper ore powder and iron ore powder are sieved through a 30mm sieve, meaning the maximum particle size does not exceed 30mm. Sieving ensures uniform particle size and avoids excessively large particles that reduce the leaching rate or excessively small particles that cause compaction of the ore pile, affecting permeability. The particle size distribution requires that particles in the 20-30mm size range account for more than 30% of the total. This size range helps balance surface area and porosity, promoting the flow of solution and air in the ore pile. Simultaneously, particles in the -5mm size range account for less than 10%, meaning the proportion of fine particles is controlled to be low. This prevents excessively fine particles from accumulating and clogging or forming dead zones, resulting in poor aeration of the ore pile, which in turn affects the colonization and proliferation of leaching bacteria, leading to poor leaching uniformity. The proportion of iron ore powder added to the ore heap is 5-10% by weight. The purpose of adding pyrite is that during bioleaching, ferric ions play a major role in eroding and stripping copper. The iron compound in pyrite is mainly ferrous disulfide, which produces ferrous ions after leaching. These ferrous ions can then be utilized by leaching bacteria through chemoenergetic reactions and oxidized back to ferric ions. Therefore, the addition of pyrite provides sulfur and iron, serving as an energy substrate for leaching bacteria while also promoting bacterial growth and oxidation reactions. In practice, it has been found that too low a proportion of pyrite is insufficient to maintain microbial activity, while too high a proportion can lead to excessive acid production or iron precipitation, affecting leaching selectivity. The selection of these parameters collectively optimizes the physical structure (such as porosity and permeability) and chemical environment (such as the sulfur-iron ratio) of the ore heap, ensuring a stable and efficient leaching process. Strict control of particle size distribution helps reduce short-circuiting or local saturation of the leachate, while the design of the blending ratio can improve leaching efficiency.

[0047] Optionally, the acid solution is sulfuric acid with a concentration of 6~12g / L, and the pH of the leaching bacteria solution is 1.8~2.0.

[0048] In this application, the acid solution is sulfuric acid with a concentration of 6-12 g / L. This concentration range ensures that the pH is maintained in an acidic environment suitable for microbial activity (pH 1.8-2.0 in this application), while avoiding excessively high concentrations that could lead to ore surface passivation and environmental toxicity. Furthermore, sulfuric acid has the advantages of low cost and good compatibility with microorganisms. A sulfuric acid concentration of 6-12 g / L provides sufficient hydrogen ions to dissolve copper minerals and adjusts the acidity of the ore pile, promoting subsequent bacterial colonization. The pH of the leaching bacteria solution is 1.8-2.0, which is the optimal growth condition for leaching bacteria (such as *Thiobacillus ferrooxidans*), ensuring bacterial activity and oxidation capacity. Too low a pH is detrimental to bacterial growth, while too high a pH leads to a reduced mineral dissolution rate. Adjusting the pH of the bacterial solution before inoculation ensures consistency with the pH conditions of the bacteria in the solution, preventing sudden environmental changes that could hinder bacterial adaptation and affect bacterial colonization and growth. The aforementioned parameters work synergistically to provide a consistent acidic environment for the ore heap during the spraying stage and ensure rapid adaptation of microorganisms to the environment after inoculation, thereby accelerating the leaching start-up phase and guaranteeing leaching efficiency. This scheme reduces uncertainties in the leaching process and improves the repeatability and efficiency of the method by precisely controlling chemical and biological conditions.

[0049] Optionally, the leaching bacteria include *Thiobacillus ferrooxidans*, and the leaching bacteria solution is selected and propagated by the following method:

[0050] The *Acidithiobacillus ferrooxidans* strain (commercially available or isolated from acidic wastewater from local mines) was cultured in 9K medium for 10... 7 The concentration of cfu / ml was used to obtain the culture solution.

[0051] After sterilizing five 250mL Erlenmeyer flasks at high temperature, 10mL of the culture solution was placed in each flask and added to 90mL of sterile selective culture medium. 50wt%H2SO4 was added to adjust the pH to 1.8. The flasks were then placed in a constant temperature shaker and cultured at a temperature of 35~40℃ and a rotation speed of 150r / min.

[0052] In the previous generation, choose the darkest color, Fe 2+ The strain with the highest conversion rate was enriched for three generations. The enriched leaching bacteria were then subcultured for a total of six generations at inoculum rates of 10%, 9%, 8%, 7%, 6%, and 5% of the previous generation to obtain a pure strain.

[0053] After propagating the pure strain, a mineral leaching bacterial solution with an inoculation rate of 15-20% was prepared.

[0054] In this application, *Acidithiobacillus ferrooxidans* can be derived from local acidic mine water, commercially available strains, or samples from a collection center.

[0055] In this application, the leaching bacteria include *Thiobacillus ferrooxidans* (AFFE).At.f This bacterium, *Thiobacillus acidophilus*, can oxidize ferrous iron and sulfides, producing sulfuric acid and ferric ions, thus promoting the dissolution of copper minerals. In this application, the breeding and propagation method obtains highly active strains through multiple generations of culture. The specific steps include: first, culturing the *Thiobacillus acidophilus* strain in 9K medium to 10... 7 CFU / ml was used to cultivate the bacterial culture to a concentration sufficient for adequate inoculum size. 9K medium is a standard bacterial culture medium providing essential nutrients. Next, five 250mL Erlenmeyer flasks were sterilized at high temperature (e.g., 121℃, 15-20 minutes) to eliminate contamination. 10mL of the culture from each flask was placed in 90mL of sterile selective culture medium, for a total volume of 100mL, a dilution ratio of 1:10. 50wt% H₂SO₄ was added to adjust the pH to 1.8 to screen for acid-resistant strains. The flasks were then placed in a constant-temperature shaker with an operating temperature set to 35-40℃ (close to the optimal growth temperature for this bacterium) and a rotation speed of 150 rpm to provide uniform aeration and mixing. The darkest color and Fe content were selected from the previous generation. 2+ The strain with the highest conversion rate was subjected to three generations of enrichment culture. Darker color indicates higher bacterial density and more oxidation products. (Fe) 2+ High conversion rate indicates strong oxidative activity; enrichment culture enhances strain purity and activity. The enriched leaching bacteria were subcultured for six generations at inoculum rates of 10%, 9%, 8%, 7%, 6%, and 5% of the previous generation to obtain pure strains. Finally, the pure strains were propagated to prepare a leaching bacterial solution with an inoculum rate of 15-20%. Propagation was achieved through standard fermentation, and the 15-20% (mass percentage) inoculum ensured sufficient initial bacterial count in the ore pile. This method, through multiple generations of selection, improved the adaptability and efficiency of the strain, providing a reliable microbial source for the leaching process.

[0056] Optionally, the selection medium includes a first culture medium and a second culture medium;

[0057] The first culture medium consists of 0.1g KCl, 3.0g (NH4)2SO4, 0.5g MgSO4·7H2O, 0.5g K2HPO4, and 0.01g Ca(NO3)2 dissolved in 800mL deionized water, and 50wt% H2SO4 is added dropwise to adjust the pH to 2.0.

[0058] The second culture medium consists of 44.2g FeSO4·7H2O dissolved in 200mL deionized water, and 50wt% H2SO4 added dropwise to adjust the pH to 2.0;

[0059] The first and second culture solutions were mixed and sterilized to obtain the selection culture medium.

[0060] In this application, the first and second culture media are mixed and then sterilized (e.g., autoclaved) to obtain a selective culture medium, ensuring uniform nutrient distribution. This culture medium composition is based on a modified standard 9K medium, providing optimized growth conditions, and [Fe...]. 2+ The concentration was controlled using FeSO4·7H2O to support the metabolic needs of *Thiobacillus ferrooxidans*. Sterilization eliminated interference from other microorganisms to ensure the purity of the strain and to guarantee the reproducibility and efficiency of the selection process.

[0061] Optionally, the specifications of the heap leaching column are Φ1.5×10.0m, the height of the ore heap is 1~9m, and the distribution density of the vertical pipes is 8~10 pipes / m. 2 All of them have equally spaced openings on the side.

[0062] In this application, the height of the ore pile is 1-9 meters, and the height range is flexible. The height affects the solution residence time and ventilation efficiency, and it is necessary to avoid excessive height leading to compaction or excessive height leading to insufficient utilization. The distribution density of the vertical pipes is 8-10 pipes / m. 2 This involves installing 8 to 10 vertical pipes (Φ50~100mm pipes) per square meter of ore pile area. These vertical pipes improve the gas-liquid distribution within the ore pile; their density ensures uniform coverage and prevents localized dead zones. All vertical pipes have equally spaced openings on their sides to facilitate air and solution infiltration into the ore pile, and the equal spacing promotes uniform flow. These parameters collectively optimize the ore pile structure, enhance mass and heat transfer efficiency during the leaching process, reduce the risk of short circuits or blockages, and thus improve leaching consistency and rate. In this application, the bottom of the vertical pipe is 15~20cm from the bottom of the ore pile, and the top extends 5~10cm above the ore pile.

[0063] Optionally, during the leaching process, the dripping rate is 8~12 L / m³. 2 • h, initially the dripping period is 72~80h, the interval is 45~48h, repeated 3~5 times, then the dripping period is 40~48h, the interval is 40~48h until the dripping ends;

[0064] During each interval of the leaching process, ventilation is provided into the ore pile once through a vertical pipe, with a ventilation rate of 12-14 L / m³. 2 •h, the duration of a single ventilation session is 2~2.5h.

[0065] In this application, the dripping period refers to the continuous spraying time, the interval period refers to the settling time after spraying is stopped, and the drip rate is 8~12L / m. 2•h, meaning 8 to 12 liters of solution are dripped per unit area per hour. This range balances the supply of leaching agent with the permeability of the ore pile, avoiding excessive flow rate which would affect leaching efficiency or insufficient flow rate which would lead to incomplete reaction. Initially, the dripping period is 72-80 hours, with an interval of 45-48 hours, repeated 3-5 times. The longer initial dripping period is used to saturate the ore pile and initiate bacterial activity, while the interval period allows the solution to fully permeate the ore pile. Repeating the reaction 3-5 times ensures stable initial leaching. Afterward, the dripping period is 40-48 hours, with an interval of 40-48 hours until the dripping ends. The later dripping period can be adjusted according to the leaching progress, while the intervals remain similar to maintain cyclical balance. During each interval of the leaching process, ventilation is provided to the ore pile once through a vertical pipe at a ventilation rate of 12-14 L / m². 2 The ventilation duration is 2-2.5 hours per cycle. Ventilation provides oxygen, which acts as an electron acceptor for bacterial oxidation, promoting sulfur and iron oxidation. The ventilation volume and duration ensure sufficient oxygen concentration inside the ore pile, preventing anaerobic conditions from affecting bacterial activity. Vertical pipes, acting as ventilation channels, optimize gas distribution. These parameters, by controlling the liquid-to-gas ratio and timing, improve the leaching rate and copper dissolution efficiency while reducing energy consumption.

[0066] In this application, the redox potential of the raffinate should be maintained at 550~600mv. If the redox potential of the raffinate after copper extraction is greater than 600mv, the saponified P204-sulfonated kerosene extraction system can be used to extract ferric iron. Among them, the volume content of P204 in the organic phase is 20~25%.

[0067] Optionally, the leachate may be extracted using an extractant formulated from one or more of hydroxamic acid, aldoxime, ketoxime and amine oxime.

[0068] In this application, the extractant comprises one or more of hydroxamic acids, aldoximes, ketoximes, and amine oximes; these are all organic extractants used for the extraction of copper ions. Hydroxamic acids (such as the LIX series) exhibit high selectivity for copper ions, forming complexes; aldoximes and ketoximes (such as Acorga reagents) provide similar functions, and amine oximes may also be used for specific copper species. One or more combinations are selected based on the leachate composition to improve copper recovery. The extraction operation is performed when the copper ion concentration in the leachate is greater than 1.13 g / L; the extractant extracts copper from the aqueous phase, and the raffinate is returned to the ore heap.

[0069] Optionally, the pH of the raffinate is maintained at 1.8 to 2.0.

[0070] In this application, the raffinate is the solution returned to the ore pile after extraction. Maintaining the pH within this range ensures compatibility with the ore pile environment and avoids pH fluctuations affecting bacterial activity or mineral dissolution. A pH of 1.8–2.0 is selected and maintained by adding acid or a buffer. This pH prevents the raffinate from having a high pH, ​​which would make it difficult to break down the passivation film on the mineral powder surface and thus affect leaching efficiency.

[0071] Optionally, the temperature of the ore pile is maintained at 35-40°C during the leaching process.

[0072] In this application, the temperature range represents the optimal growth temperature for mineral-leaching bacteria (such as *Thiobacillus ferrooxidans*), promoting microbial metabolism and oxidation rates. Temperatures below 35°C slow the reaction, while temperatures above 40°C may lead to bacterial inactivation or enzyme denaturation. Temperature maintenance can be achieved through environmental control, ventilation regulation, or external heat exchange. Specific Implementation Example 1

[0073] S101. Crush the copper-bearing ore and pyrite separately and pass them through a 30mm sieve to obtain copper ore powder and iron ore powder. The proportion of 20-30mm particles in the copper ore powder and iron ore powder shall be greater than 30%, and the proportion of -5mm particles shall be less than 10%. Mix the copper ore powder and iron ore powder and pile them in a heap leaching column with a pile height of 1-9m. Place 10 columns / m in the ore pile. 2 The vertical pipes are laid at a certain density, and the proportion of iron ore powder mixed in the ore pile is 5% (by weight).

[0074] S102, First use sulfuric acid with a concentration of 6 g / L at 8 L / m 2 The ore pile was sprayed with a flow rate of ·h for 24h, and then inoculated with a leaching bacteria solution with a pH of 1.8~2.0 (the inoculation amount of leaching bacteria in the leaching bacteria solution was 20%) to carry out the leaching process. During the leaching process, the temperature of the ore pile was maintained at 35~40℃.

[0075] S103. The leaching and heaping process uses raffinate with a pH of 1.8~2.0 for circulating leaching. During the leaching and heaping process, the drip rate of raffinate is 8L / m³. 2 The initial dripping period was 72 hours, with a 45-hour interval, repeated three times. Afterward, the dripping period was 40 hours, with a 40-hour interval until the dripping process ended. During each interval of the leaching process, ventilation was provided to the ore pile once through a vertical pipe, with a ventilation rate of 12 m³ / m². 2 •h, the duration of a single ventilation session is 2.5h.

[0076] The copper ion concentration in the leachate was periodically sampled and analyzed. When the copper ion concentration in the leachate was greater than 1.13 g / L, the leachate was extracted for further extraction. The raffinate after extraction was returned to the ore heap for continued drip leaching. When the copper ion concentration in the leachate was less than 1.13 g / L, the leachate was directly returned to the ore heap for continued drip leaching. The leaching rate was measured to be 85.71%. Example 2

[0077] S201. Crush the copper-bearing ore and pyrite separately and pass them through a 30mm sieve to obtain copper ore powder and iron ore powder. The proportion of 20-30mm particles in the copper ore powder and iron ore powder is greater than 30%, and the proportion of -5mm particles is less than 10%. Mix the copper ore powder and iron ore powder and pile them in a heap leaching column with a pile height of 1-9m. Place 8 columns per m in the ore pile. 2 The vertical pipes are laid at a certain density, and the proportion of iron ore powder mixed in the ore pile is 10% (by weight).

[0078] S202, First use sulfuric acid with a concentration of 12 g / L at a flow rate of 12 L / m 2 The ore pile was sprayed with a flow rate of ·h for 20h, and then inoculated with a leaching bacteria solution with a pH of 1.8~2.0 (the inoculation amount of leaching bacteria in the leaching bacteria solution was 20%) for leaching process. During the leaching process, the temperature of the ore pile was maintained at 35~40℃.

[0079] S203. The leaching and heaping process uses raffinate with a pH of 1.8~2.0 for circulating leaching. During the leaching and heaping process, the drip rate of raffinate is 12L / m³. 2 The initial dripping period was 80 hours, with a 48-hour interval, repeated 5 times. Afterward, the dripping period was 48 hours, with a 48-hour interval until the dripping process ended. During each interval of the leaching process, ventilation was provided to the ore pile once through a vertical pipe at a rate of 14 L / m³. 2 •h, the duration of a single ventilation session is 2 hours.

[0080] The copper ion concentration in the leachate was periodically sampled and analyzed. When the copper ion concentration in the leachate was greater than 1.13 g / L, the leachate was extracted for further extraction. The raffinate after extraction was returned to the ore heap for continued drip leaching. When the copper ion concentration in the leachate was less than 1.13 g / L, the leachate was directly returned to the ore heap for continued drip leaching. The leaching rate was measured to be 83.69%. Example 3

[0081] S301. The copper-bearing ore and pyrite are crushed and passed through a 30mm sieve to obtain copper ore powder and iron ore powder. The proportion of 20-30mm particles in the copper ore powder and iron ore powder is greater than 30%, and the proportion of -5mm particles is less than 10%. The copper ore powder and iron ore powder are mixed and piled in a heap leaching column with a pile height of 1-9m. Nine columns are placed in the ore pile at a spacing of 1m. 2The vertical pipes are laid at a certain density, and the proportion of iron ore powder mixed in the ore pile is 8% (by weight).

[0082] S302, first use sulfuric acid with a concentration of 9 g / L at a flow rate of 10 L / m 2 The ore pile was sprayed with a flow rate of ·h for 22h, and then inoculated with a leaching bacteria solution with a pH of 1.8~2.0 (the inoculation amount of leaching bacteria in the leaching bacteria solution was 15~20%), and the leaching process was carried out. During the leaching process, the temperature of the ore pile was maintained at 35~40℃.

[0083] S303. The leaching and heaping process uses raffinate with a pH of 1.8~2.0 for circulating leaching. During the leaching and heaping process, the drip rate of raffinate is 10L / m³. 2 The initial dripping period was 75 hours, with an interval of 46 hours, repeated four times. Afterward, the dripping period was 45 hours, with an interval of 45 hours until the dripping process ended. During each interval of the leaching process, ventilation was provided to the ore pile once through a vertical pipe at a rate of 13 L / m³. 2 •h, the duration of a single ventilation session is 2.25h.

[0084] The copper ion concentration in the leachate was periodically sampled and analyzed. When the copper ion concentration in the leachate was greater than 1.13 g / L, the leachate was extracted for further extraction. The raffinate after extraction was returned to the ore heap for continued drip leaching. When the copper ion concentration in the leachate was less than 1.13 g / L, the leachate was directly returned to the ore heap for continued drip leaching. The leaching rate was measured to be 82.14%.

[0085] Comparative Example 1

[0086] The remaining operations were the same as in Example 3, except that the ore piles were all composed of copper ore powder. The measured leaching rate was 76.48%.

[0087] Comparative Example 2

[0088] The remaining operations were the same as in Example 3, except that conventional 9K medium was used as the selection medium for the leaching bacteria (the selection method was the same as in Example 3, except that conventional 9K medium was used as the selection medium). The leaching rate was measured to be 72.69%.

[0089] The mineral-leaching bacteria in Examples 1 to 3 and Comparative Example 1 were selected using the selection method and selection culture medium of this application.

[0090] The Wushan copper mine and pyrite mine in Inner Mongolia were selected as experimental subjects. The copper ore mainly consisted of chalcocite and chalcopyrite (copper grade of 0.155%). Experiments were conducted using the methods described in Examples 1-3 and Comparative Examples 1 and 2. The chalcopyrite leaching efficiency in Examples 1-3 and Comparative Examples 1 and 2 was statistically analyzed and recorded in Table 1. The calculation formula is as follows:

[0091] Leaching rate = Cu in leachate2+ Concentration / (Total mass of leached ore × Copper mass percentage)

[0092] Table 1

[0093]

[0094] As shown in Table 1, the copper leaching rate of the method in this application is above 82%, while the leaching rate of Comparative Example 1 without pyrite is significantly lower. This demonstrates that incorporating pyrite into the method of this application can effectively improve the leaching rate. The results of Comparative Example 2 show that the leaching efficiency of the strain obtained by conventional 9K culture medium is lower than that of the scheme in this application.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A method for bioleaching low-grade copper ore, characterized in that, Includes the following steps: The copper-bearing ore and pyrite are crushed and sieved to obtain copper ore powder and iron ore powder. The copper ore powder and pyrite are mixed and piled in a heap leaching column, and a vertical pipe is buried in the ore pile to obtain the ore pile. The leaching process involves spraying the ore pile with acid and then inoculating it with leaching bacteria solution. The leaching process utilizes raffinate for circulating leaching operations; The copper ion concentration of the leachate is sampled and analyzed periodically. When the copper ion concentration of the leachate is greater than 1.13 g / L, the leachate is extracted for extraction. The raffinate after extraction is returned to the ore pile for continued drip leaching. When the copper ion concentration of the leachate is less than 1.13 g / L, the leachate is directly returned to the ore pile for continued drip leaching. The leaching bacteria include *Thiobacillus ferrooxidans*, and the leaching bacteria solution is selected and propagated through the following method: The Acidithiobacillus ferrooxidans strain is cultured in 9K medium to 10 7 cfu / ml to obtain a cultured bacterial solution; After sterilizing five 250mL Erlenmeyer flasks at high temperature, 10mL of the culture solution was placed in each flask and added to 90mL of sterile selective culture medium. 50wt%H2SO4 was added to adjust the pH to 1.

8. The flasks were then placed in a constant temperature shaker and cultured at a temperature of 35~40℃ and a rotation speed of 150r / min. In the previous generation, choose the darkest color, Fe 2+ The strain with the highest conversion rate was enriched for three generations. The enriched leaching bacteria were then subcultured for a total of six generations at inoculum rates of 10%, 9%, 8%, 7%, 6%, and 5% of the previous generation to obtain a pure strain. After propagating the pure strain, a mineral leaching bacterial solution with an inoculation amount of 15-20% was prepared. The selection culture medium includes a first culture medium and a second culture medium; The first culture medium consists of 0.1g KCl, 3.0g (NH4)2SO4, 0.5g MgSO4·7H2O, 0.5g K2HPO4, and 0.01g Ca(NO3)2 dissolved in 800mL deionized water, and 50wt% H2SO4 is added dropwise to adjust the pH to 2.0; The second culture medium consists of 44.2 g FeSO4·7H2O dissolved in 200 mL of deionized water, and 50 wt% H2SO4 added dropwise to adjust the pH to 2.0; The first and second culture solutions were mixed and sterilized to obtain the selection culture medium.

2. The bioleaching method for low-grade copper ore according to claim 1, characterized in that, Both the copper ore powder and the iron ore powder are sieved through a 30mm sieve, and the proportion of particles with a size of 20-30mm in the copper ore powder and iron ore powder is greater than 30%, while the proportion of particles with a size of -5mm is less than 10%. The proportion of iron ore powder added to the ore pile is 5-10%.

3. The bioleaching method for low-grade copper ore according to claim 1, characterized in that, The acid solution is sulfuric acid with a concentration of 6~12g / L, and the pH of the leaching bacteria solution is 1.8~2.

0.

4. The bioleaching method for low-grade copper ore according to claim 1, characterized in that, The specifications of the heap leaching column are Φ1.5×10.0m, the height of the ore heap is 1~9m, and the distribution density of the vertical pipes is 8~10 pipes / m. 2 All of them have equally spaced openings on the side.

5. The bioleaching method for low-grade copper ore according to claim 1, characterized in that, During the leaching process, the drip rate is 8~12 L / m³. 2 • h, initially the dripping period is 72~80h, the interval is 45~48h, repeated 3~5 times, then the dripping period is 40~48h, the interval is 40~48h until the dripping ends; During each interval of the leaching process, ventilation is provided into the ore pile once through a vertical pipe, with a ventilation rate of 12-14 L / m³. 2 •h, the duration of a single ventilation session is 2~2.5h.

6. The bioleaching method for low-grade copper ore according to claim 1, characterized in that, The leachate is extracted using an extractant formulated with one or more of hydroxamic acid, aldoxime, ketoxime and amine oxime.

7. The bioleaching method for low-grade copper ore according to any one of claims 1-6, characterized in that, The pH of the raffinate is maintained at 1.8 to 2.

0.

8. The bioleaching method for low-grade copper ore according to any one of claims 1-6, characterized in that, The temperature of the ore pile is maintained at 35~40℃ during the leaching process.

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