A new process for bioleaching of marmatite in high altitude tailings

Abstract

The present application relates to the technical field of metallurgical separation, and discloses a new process for bioleaching of iron-wurtzite in tailings in high-altitude areas, which comprises mixing tailings with a high-altitude adaptive leaching microbial flora obtained by simulating high-altitude environment gradient acclimatization to perform heap leaching, thereby obtaining iron and zinc-rich leach liquor; performing solid-liquid separation on the leach liquor, adjusting the pH value thereof, adding hydrogen peroxide to oxidize and precipitate iron ions, and obtaining zinc-rich solution after iron removal; using ammonium carbonate to adjust the pH value of the solution to precipitate zinc, thereby obtaining high-purity zinc carbonate product, and the residual liquid being ammonium sulfate liquid fertilizer which can be used in agriculture. By using the specific microbial flora, the problems of limited application of bioleaching technology in high-altitude areas and low leaching efficiency are solved, and the range of resource utilization is widened; in combination with efficient chemical iron removal and zinc precipitation technology, high zinc recovery rate and selective separation are realized, and the residual liquid is liquid fertilizer which can be used in agriculture, thereby providing an effective way for resource utilization.

Description

Technical Field

[0001] This invention relates to the field of metallurgical separation technology, specifically a novel process for bioleaching iron sphalerite from tailings in high-altitude areas. Background Technology

[0002] Tailings, as a byproduct of mining and mineral processing, are often rich in valuable metals such as zinc, and their effective recovery is of significant economic and environmental importance. Bioleaching, as a low-cost and environmentally friendly metal extraction technology, has received widespread attention in recent years. However, existing bioleaching technologies face numerous challenges when applied to high-altitude areas.

[0003] The extreme conditions prevalent at high altitudes, such as low temperatures, low oxygen partial pressures, and strong ultraviolet radiation, severely inhibit the growth activity and metabolic efficiency of traditional leaching microorganisms, resulting in slow leaching kinetics and low metal leaching rates, making it difficult to meet the demands of industrial production. This not only limits the effective utilization of complex tailings resources in high-altitude areas but also leads to the long-term accumulation of these metal-rich secondary resources, posing potential environmental risks. Furthermore, recovering valuable metals from iron-bearing sphalerite tailings leaching solutions faces complex subsequent separation and purification challenges. Bioleaching solutions typically contain high concentrations of iron ions; if these iron impurities are not efficiently removed, they will severely interfere with the subsequent separation and purification processes of valuable metals such as zinc, increasing reagent consumption and reducing product purity. Simultaneously, traditional processes lack effective utilization of the residual liquid after leaching, resulting in resource waste. Existing technologies often struggle to simultaneously guarantee high metal recovery rates and high product purity, leading to unsatisfactory overall process efficiency and economic benefits.

[0004] Furthermore, traditional tailings treatment methods, such as high-temperature metallurgy or leaching with strong acids and alkalis, are usually accompanied by high energy consumption, emissions of toxic and harmful gases (such as sulfur dioxide), and the generation of large amounts of acidic wastewater or solid waste, placing a heavy burden on the environment. These processes are not only costly to operate, but the secondary pollution they generate also runs counter to the current concept of green and sustainable development, necessitating the development of more environmentally friendly and efficient alternative technologies. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a novel bioleaching process for iron sphalerite in tailings from high-altitude areas. This process solves the comprehensive problems of existing bioleaching processes, such as poor applicability in high-altitude areas, low metal recovery rates, complex subsequent separation processes, and high environmental impact.

[0006] To achieve the above objectives, the present invention provides a novel bioleaching process for iron-bearing sphalerite in tailings from high-altitude areas, comprising:

[0007] (a) Bioleaching stage: The tailings are mixed with a high-altitude-adapted leaching microbial community to construct a ore heap, and heap leaching is carried out by spraying a bacterial suspension to obtain a leachate rich in iron and zinc; (b) Iron removal stage of leachate: The leachate is subjected to solid-liquid separation, and the pH value of the leachate is adjusted. At the same time, an oxidant is added to precipitate and separate iron ions to obtain a zinc-rich solution after iron removal; (c) Zinc recovery stage of chemical precipitation: Ammonium carbonate is added to the zinc-rich solution after iron removal, and the pH value of the solution is adjusted to 6.0-7.5 to convert zinc ions into zinc carbonate precipitate. After filtration, washing and drying, a high-purity zinc carbonate product is obtained. The residual liquid is ammonium sulfate liquid fertilizer, which can be directly used for agricultural production.

[0008] This invention provides a leaching microbial community specifically designed for high-altitude areas. Its preparation principle lies in simulating the extreme environmental pressure of high-altitude areas to screen and domesticate a microbial community that is tolerant to low temperature, low oxygen, strong ultraviolet radiation and high concentration of tailings slurry and has high leaching activity.

[0009] The specific process for obtaining this microbial community is as follows: First, the original microbial source was collected from mine water and slag in high-altitude, acidic copper mines. Then, it was enriched and cultured in a 9K basal medium with ferrous sulfate as the sole energy source. This step utilized the oxidizing ability of acidophilic iron-oxidizing bacteria (such as *Thiobacillus ferrooxidans* and *Leptospira ferrooxidans*) to rapidly expand the microbial population with iron-oxidizing potential. Following this, through multi-stage gradient acclimatization, the adaptability of the microbial community to the high-altitude environment and the target tailings was gradually enhanced.

[0010] Tailings concentration gradient acclimatization: Gradually increase the concentration of tailings powder in the culture system from 5% (w / v) to 20% (w / v) to force microorganisms to adapt to the high solid phase environment and maintain their leaching activity, and screen out strains that can function stably under high tailings load.

[0011] Hypoxia acclimatization: Dissolved oxygen concentration was controlled at a low level of 1.0-4.0 mg / L by introducing a mixture of nitrogen and air into the culture system. This condition simulated the hypoxic environment of high-altitude areas, prompting microorganisms to adjust their metabolic pathways and respiratory chain components to maintain efficient energy metabolism and mineral oxidation activity under limited oxygen supply.

[0012] Low-temperature acclimatization: The culture temperature is gradually reduced from 25℃ to 5-15℃. This step eliminates cold-intolerant strains by applying low-temperature pressure and enriches psychrophilic or facultative psychrophilic microorganisms that can maintain enzyme activity and growth and reproduction at lower temperatures, enabling them to work efficiently in the typical low-temperature environment of high-altitude areas.

[0013] Ultraviolet (UV) tolerance acclimation: During cultivation, intermittent low-intensity UVA lamps were used for irradiation. This measure simulated the stronger UV radiation at high altitudes, prompting microorganisms to develop more effective DNA repair mechanisms, antioxidant enzyme systems, or pigment protection mechanisms, thereby enhancing their resistance to UV radiation and ensuring their survival rate and activity in high-altitude open-air leaching environments.

[0014] After the above screening and domestication, the high-altitude adapted leaching microbial community was finally obtained. It can overcome the limiting factors such as low temperature, low oxygen, and strong ultraviolet radiation in high-altitude areas, and exhibits highly efficient bioleaching activity on iron and zinc minerals in the target tailings. After preservation and large-scale cultivation, this microbial community forms the active material component in the subsequent bioleaching process, with its microbial cell concentrate or bacterial suspension serving as the main leaching medium.

[0015] The bioleaching stage of this invention employs a heap leaching process. By optimizing the heap structure, tailings pretreatment, microbial inoculum size, liquid-to-solid ratio, and environmental control parameters, it aims to improve zinc leaching efficiency and shorten the leaching cycle. Its principle and innovation lie in:

[0016] Tailings pretreatment: Before bioleaching, the tailings particle size reaches 20%-85% less than 0.074 mm. Reducing the particle size increases the contact surface area between the minerals and microorganisms and their metabolic products, thereby improving the mineral dissolution rate and leaching efficiency. At the same time, by controlling the particle size, the permeability and liquid retention of the ore pile can be optimized, providing favorable conditions for the uniform distribution of the leachate and gas exchange.

[0017] Ore heap construction and aeration: Perforated PVC pipes are uniformly inserted vertically inside the ore heap for even air introduction. The diameter, perforation diameter, and perforation spacing of the PVC pipes are optimized (diameter 50-100mm, perforation diameter 5-10mm, perforation spacing 50-100mm). This structure ensures an adequate supply of oxygen inside the ore heap, providing the necessary conditions for the growth of aerobic leaching microorganisms and the iron oxidation reaction. Oxygen is a key substrate for the oxidation of ferrous ions by microorganisms such as *Thiobacillus ferrooxidans*. Precise control of the aeration rate (0.8-1.5 VVM) ensures a sufficient oxygen supply, maintaining microbial activity and the continuous progress of the leaching reaction.

[0018] Microbial community and inoculum: The high-altitude adapted leaching microbial community obtained in the first aspect was used. Its adaptability to the extreme high-altitude environment ensured the activity and stability of the microbial community under actual operating conditions. The mass ratio of tailings to active material components was 100:(0.5-5), and the initial concentration of the bacterial suspension was 1x10⁻⁶. 6 -1x10 8 Cells / mL, and 5.5-20.0 L / mL 3The liquid-to-solid ratio of tailings aims to quickly establish an efficient microbial ecosystem through reasonable microbial inoculation and initial liquid volume, shorten the leaching start-up time, maintain sufficient moisture during the leaching process, and promote material transport.

[0019] Environmental parameter control:

[0020] Temperature control: The leaching system temperature is controlled between 5-40℃. This range covers the low-temperature environment of high-altitude areas and the moderate temperature that microorganisms can reach through metabolic heat production, ensuring the optimal activity of leaching microorganisms (especially thermophilic and mesophilic acidophilic bacteria).

[0021] pH Maintenance: The pH value during the leaching process is maintained between 1.5 and 3.0. Under these acidic conditions, sphalerite can be indirectly oxidized by microorganisms. The generated ferrous ions act as oxidants, attacking the mineral lattice, while preventing premature hydrolysis and precipitation of ferrous ions at higher pH levels, thus preserving its oxidizing capacity. Monitoring and adjusting the pH (using dilute sulfuric acid or dilute sodium hydroxide) is crucial to ensuring a continuous and efficient leaching reaction.

[0022] Leaching time: The leaching time is set at 150-250 days. This time range has been optimized to ensure a high metal leaching rate while also taking into account production efficiency and reducing the time cost of cyclical operations.

[0023] The iron removal stage of the leaching solution in this invention aims to efficiently and selectively remove iron impurities from the leaching solution, providing a clean feed solution for subsequent zinc separation. Its principle and innovation lie in:

[0024] Synergistic effect of iron oxidation and hydrolysis precipitation: Bioleaches contain a large amount of ferrous ions. To remove iron, ferrous ions must first be oxidized to ferric ions, as ferric ions have a much stronger hydrolytic precipitation ability than ferrous ions. This process achieves rapid and efficient oxidation of ferrous ions by adding oxidants (hydrogen peroxide, sodium peroxide, and potassium permanganate, etc.) while adjusting the pH.

[0025] Specifically, hydrogen peroxide, sodium peroxide, and potassium permanganate, as strong oxidizing agents, can oxidize ferrous ions in the leachate to ferric ions. During this process, the amount of hydrogen peroxide used is precisely controlled to 1.2-1.5 times the theoretical amount required for ferrous ion oxidation to ensure sufficient oxidation and avoid affecting subsequent precipitation due to incomplete oxidation. Subsequently, the pH of the leachate is precisely adjusted to 3.0-4.5 using a lime slurry suspension. Within this pH range, ferric ions rapidly hydrolyze and precipitate as ferric hydroxide or other complex iron hydrolysis products. Ferric hydroxide is a hydrophobic colloid, easily flocculated and precipitated, thus removed through solid-liquid separation.

[0026] Selective precipitation: Within the pH range of 3.0-4.5, ferric ions preferentially precipitate, while zinc ions remain in the solution as soluble ions. This difference in pH sensitivity is key to achieving initial separation of iron and zinc. By optimizing the pH adjustment range, iron removal is maximized while zinc co-precipitation loss is minimized, ensuring the purity and recovery rate of the zinc-rich solution.

[0027] Efficient separation and solid-liquid separation: After the oxidation and precipitation processes, the generated iron sludge (mainly ferric hydroxide precipitate) is separated from the zinc-rich solution through static settling and filtration. This step ensures a clear solution after iron removal and reduces the impact of suspended solids on subsequent chemical precipitation processes.

[0028] This invention employs a chemical precipitation method to efficiently recover zinc from a zinc-rich solution after iron removal, while simultaneously utilizing the residual liquid for resource recovery. Its principle and innovation lie in utilizing the specific reaction between ammonium carbonate and zinc ions, combined with optimized process parameters, to achieve efficient zinc precipitation and product purification, with the byproduct being usable agricultural fertilizer. The principle of the chemical precipitation reaction: In the zinc-rich solution after iron removal, zinc ions exist in the form of soluble sulfate.

[0029] Adding ammonium carbonate as a precipitant to the solution causes a double displacement reaction between ammonium carbonate and zinc ions, forming zinc carbonate precipitate that is sparingly soluble in water. The reaction equation is as follows: ZnSO4 + (NH4)2CO3 → ZnCO3↓ + (NH4)2SO4. This reaction is characterized by high selectivity and a fast reaction rate. Under suitable pH and temperature conditions, zinc ions can be rapidly converted into zinc carbonate precipitate, while other trace impurity ions in the solution are unlikely to form precipitates, thus ensuring product purity.

[0030] Process parameter optimization: Ammonium carbonate dosage: Controlled to 1.1-1.3 times the theoretical amount required for zinc ion precipitation. Excess ammonium carbonate ensures sufficient zinc ion precipitation while avoiding reduced zinc recovery due to insufficient dosage. The excess can be removed through subsequent washing without affecting product quality. Reaction pH: Adjust the solution pH to 6.0-7.5. This pH range is the optimal condition for zinc carbonate precipitation, ensuring efficient zinc ion precipitation while preventing the formation of impurities such as zinc hydroxide, and preventing ammonium carbonate decomposition, thus improving precipitant utilization. Reaction temperature and stirring rate: The reaction temperature is controlled between 5-40℃. This temperature range accelerates the reaction rate, promotes zinc carbonate crystal growth, and facilitates subsequent filtration and separation. The stirring rate is set to 100-200 rpm to ensure thorough mixing of ammonium carbonate and the zinc-rich solution, avoiding incomplete precipitation or uneven product particle size caused by uneven local concentration.

[0031] Reaction time: Controlled within 1-3 hours to ensure the reaction reaches equilibrium and zinc ion precipitation is complete, while avoiding product agglomeration or impurity adsorption due to excessively long reaction times. Product purification and residual liquid utilization: After zinc carbonate precipitate is formed, solid-liquid separation is achieved through filtration. The precipitate is washed 2-3 times with deionized water to remove surface-adsorbed impurities such as ammonium sulfate, and then dried at 60-80℃ for 2-4 hours to obtain high-purity zinc carbonate product. The residual liquid after separation mainly consists of ammonium sulfate aqueous solution, which meets relevant agricultural fertilizer standards and can be directly used as liquid fertilizer for crop cultivation, realizing the resource utilization of leachate, reducing wastewater discharge, and improving the environmental and economic benefits of the process.

[0032] This invention provides a novel bioleaching process for iron-bearing sphalerite in tailings from high-altitude areas. It offers the following advantages:

[0033] 1. This process is designed for the environmental characteristics of high-altitude areas, such as low temperature, low oxygen, and strong ultraviolet radiation. It has developed and domesticated a high-altitude-adaptable leaching microbial community and combined with optimized heap leaching process parameters, enabling the process to operate stably and efficiently under harsh high-altitude conditions. This overcomes the problem of the limited application of traditional bioleaching technology in plateau areas, thereby bringing difficult-to-process secondary resources such as iron sphalerite tailings from high-altitude areas into the scope of effective utilization and improving the comprehensive resource recovery rate.

[0034] 2. This process, through refined pretreatment of tailings, increases the contact area between minerals and microorganisms. Combined with an efficient bioleaching process, it ensures maximum zinc dissolution. In the subsequent iron removal stage of the leaching solution, by controlling the pH value and adding an appropriate amount of oxidant, highly efficient and selective removal of iron ions is achieved, minimizing zinc co-precipitation loss. Finally, zinc is recovered using chemical precipitation. By optimizing key parameters such as precipitant dosage, pH value, and temperature, efficient precipitation and purification of zinc ions are achieved, yielding high-purity zinc carbonate. Simultaneously, ammonium sulfate liquid fertilizer is produced as a byproduct, improving the process's comprehensive resource utilization level and economic benefits.

[0035] 3. This invention employs bioleaching technology, which, compared to traditional high-temperature metallurgical or strong acid leaching methods, offers advantages such as low energy consumption, mild operating conditions, and no harmful gas emissions. The iron removal stage of the leaching solution utilizes lime slurry and hydrogen peroxide, resulting in relatively stable and easily treatable iron sludge. The chemical precipitation process for zinc recovery is simple to operate and low-cost, avoiding the high equipment investment and maintenance costs associated with complex technologies such as membrane separation. Furthermore, the residual liquid can be directly used as agricultural fertilizer, achieving zero wastewater discharge and resource recycling, minimizing chemical consumption and secondary pollution. Detailed Implementation

[0036] The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the preparation examples, examples, comparative examples, and test examples. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0037] Preparation Example 1:

[0038] Preparation Example 1: Screening and domestication of high-altitude adapted mineral leaching microbial communities

[0039] This preparation example aims to obtain a mixed microbial community that can adapt to extreme environments such as low temperature, low oxygen, and strong ultraviolet radiation in high-altitude areas and has highly efficient leaching activity on target tailings.

[0040] Sample collection and enrichment:

[0041] Five liters of water and one kilogram of slag were collected from acidic mine water in a high-altitude copper mining area (average altitude of about 3,000 meters).

[0042] In Preparation Example 1, 100 mL of water sample and 10 g of slag sample were inoculated into 500 mL of 9K basal medium (ammonium sulfate 3.0 g / L, potassium dihydrogen phosphate 0.5 g / L, magnesium sulfate heptahydrate 0.5 g / L, potassium chloride 0.1 g / L, calcium nitrate 0.01 g / L), with ferrous sulfate heptahydrate (concentration of 20-50 g / L) as the sole energy source. The initial pH of the medium was adjusted to 1.5-2.5 using dilute sulfuric acid.

[0043] The mixture was placed in a constant temperature shaker and enriched at 15-25℃ and 120-180 rpm / min until the solution turned a distinct brownish-yellow due to oxidation by ferrous ions.

[0044] Gradual acclimatization and tolerance enhancement:

[0045] The enriched bacterial culture was transferred to a new 9K medium at an inoculation rate of 10% (v / v), and sterilized tailings powder was added at the same time. The tailings concentration was started at 5% (w / v), and the mixture was passaged every 3-5 days to gradually increase the tailings slurry concentration to 10%, 15% and up to 20% (w / v).

[0046] During the domestication process, a high-altitude environment is gradually simulated. Specific measures include:

[0047] Hypoxia adaptation: The dissolved oxygen concentration is controlled at a low level of 1.0-4.0 mg / L by introducing a mixture of nitrogen and air into the culture system.

[0048] Low temperature adaptation: The culture temperature was gradually reduced from 25℃ to 5-15℃ to screen and enrich low temperature resistant strains.

[0049] UV tolerance: During the culture process, the culture system is intermittently irradiated with low-intensity UV lamps (UVA band, 320-400nm) (e.g., 0.5-2 hours per day) to enhance the bacterial community's resistance to UV radiation.

[0050] Activity screening and microbial community preservation:

[0051] At each stage of the acclimation process, the leaching rate of zinc from the tailings by the bacterial solution was periodically monitored. Acclimation was considered complete when the bacterial community maintained stable and efficient leaching activity under simulated high-altitude conditions and a tailings slurry concentration of 20% (w / v) (e.g., the zinc leaching rate reached a specific target within 15 days).

[0052] The domesticated active bacterial solution was mixed with glycerol in a 1:1 ratio, dispensed, and stored in an ultra-low temperature freezer at -80℃ as the original strain for subsequent bioleaching experiments.

[0053] The culture was stored in an ultra-low temperature freezer at -80°C and used as the original strain for subsequent bioleaching experiments. The active material components mentioned in subsequent examples refer to the bacterial concentrate (or bacterial suspension containing culture medium) obtained by centrifugation after thawing this culture and expanding its culture in 9K medium to the late logarithmic growth stage.

[0054] Examples 1-3:

[0055] Example 1:

[0056] This embodiment provides a novel bioleaching process for iron-bearing sphalerite in tailings from high-altitude areas, comprising the following steps:

[0057] Bioleaching stage:

[0058] Raw material preparation: Take 2500 kg (2.5 tons) of tailings sample, with 80% of the particles being less than 0.074 mm. Thoroughly mix the pretreated tailings with 12.5 kg of active material components, with a mass ratio of tailings to active material components of 100:0.5.

[0059] Ore pile construction: Construct the above mixture into a pile with a volume of approximately 2.5m³. 3 The leached ore pile is prepared by evenly inserting 5-8 perforated PVC pipes vertically inside the pile. Each PVC pipe has a diameter of 75mm and 7mm diameter holes drilled in its wall, spaced 75mm apart. The bottom of the PVC pipe is 100mm from the bottom of the ore pile, and the top extends 150mm above the surface of the pile.

[0060] Inoculation and Spray Leaching: The high-altitude adapted mineral leaching microbial community obtained in Preparation Example 1, after screening and domestication, was diluted with sterile 9K basal medium to prepare an initial concentration of 5 x 10⁻⁶. 6 A bacterial suspension of 1 cell / mL was applied. At a liquid-to-solid ratio of 1.25 L / kg tailings (approximately 3125 L of bacterial suspension in total), it was uniformly sprayed onto the top of the ore pile using a spray system. The initial pH of the leachate was adjusted to 2.0 by adding dilute sulfuric acid.

[0061] Environmental control and liquid circulation:

[0062] Temperature control: The temperature of the leaching system is stably controlled at 30±2℃ through heat exchangers inside the ore pile or external insulation measures.

[0063] Aeration control: Air is continuously introduced into the bottom of the ore pile and into the inserted PVC pipe by a blower, and the aeration rate is controlled at 1.0 VVM (that is, the ratio of the volume of air introduced per minute to the volume of the ore pile is 1:1).

[0064] Liquid circulation: After being collected from the bottom of the ore pile, the leachate is filtered to remove a small amount of particulate matter and then sprayed back to the top of the ore pile every 4 hours. During the circulation process, the pH value is maintained at 1.5-2.5 using dilute sulfuric acid or dilute sodium hydroxide solution based on pH monitoring results.

[0065] Leaching duration: The bioleaching process lasts for 160 days.

[0066] Process monitoring: During the leaching process, samples were taken every 24 hours to monitor the pH value (using a glass electrode pH meter), Eh value (using a Pt electrode Eh meter), dissolved oxygen content (using a dissolved oxygen meter), and system temperature of the leachate. Samples were taken every 2 days, and inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to analyze the concentration changes of major metal ions such as zinc and iron in the leachate. After leaching, tailings samples were taken from the ore pile, and the residual zinc content was analyzed using ICP-AES to calculate the leaching rate.

[0067] Leachate treatment and zinc recovery stage:

[0068] Iron impurity removal: The zinc-rich leachate collected after bioleaching is preliminarily filtered to remove suspended solids. Lime milk (e.g., 20% w / v calcium hydroxide suspension) is added to the filtrate and stirred slowly to raise the pH of the leachate to 3.8 ± 0.1.

[0069] During pH adjustment, an appropriate amount of oxidant (e.g., 30% hydrogen peroxide solution, the amount of which is 1.2-1.5 times the amount required for the theoretical oxidation of ferrous ions) is added to oxidize ferrous ions to ferric ions.

[0070] After stirring continuously for 1-2 hours, let it stand and settle for 4-6 hours, filter and separate the iron sludge (mainly iron hydroxide), and obtain a zinc-rich solution after iron removal.

[0071] Zinc recovery by chemical precipitation: The zinc-rich solution after iron removal is transferred to a reaction vessel and heated to 35±2℃, with a stirring rate of 150 rpm. Solid ammonium carbonate is slowly added to the solution, the amount added being 1.2 times the theoretical amount required for zinc ion precipitation. Simultaneously, the pH of the solution is adjusted to 6.5±0.2 using dilute ammonia or dilute sulfuric acid. After stirring for 2 hours, stirring is stopped, and the mixture is allowed to settle for 1 hour. Solid-liquid separation is then performed using a plate and frame filter press. The precipitate is washed three times with deionized water, each time using water equal to the wet weight of the precipitate. It is then dried at 70℃ for 3 hours to obtain a high-purity zinc carbonate product. The residual liquid after separation is ammonium sulfate liquid fertilizer. After testing its concentration and purity, it is directly used for farmland fertilization.

[0072] Example 2:

[0073] This embodiment provides a novel bioleaching process for iron sphalerite in tailings from high-altitude areas, including the following steps:

[0074] Bioleaching stage:

[0075] Raw material preparation: 2500 kg (2.5 tons) of tailings sample was pretreated to ensure that 50% of the particles were less than 0.074 mm. The pretreated tailings were then thoroughly mixed with 25 kg of active material components at a mass ratio of 100:1.

[0076] Ore pile construction: Construct the above mixture into a pile with a volume of approximately 1.5m³. 3 The leached ore pile. Three perforated PVC pipes are evenly inserted vertically inside the ore pile. Each PVC pipe has a diameter of 50 mm, and the pipe wall has holes with a diameter of 5 mm drilled in it, with a hole spacing of 100 mm. The bottom of the PVC pipe is 100 mm away from the bottom of the ore pile, and the top of the PVC pipe is 150 mm above the surface of the ore pile.

[0077] Inoculation and Spray Leaching: The high-altitude adapted mineral leaching microbial community obtained in Preparation Example 1 was diluted with sterile 9K basal medium to prepare an initial concentration of 1x10⁻⁶. 7 A bacterial suspension of cells / mL.

[0078] The liquid-to-solid ratio was 0.5 L / kg tailings (i.e., a total of approximately 1250 L of bacterial suspension), which was then evenly sprayed onto the top of the ore pile using a spray system. The initial pH of the leachate was adjusted to 1.8 by adding dilute sulfuric acid.

[0079] Environmental control and liquid circulation:

[0080] Temperature control: The temperature of the leaching system is stably controlled at 15±2℃ by external insulation of the ore pile or ambient temperature control.

[0081] Aeration control: Air is continuously introduced into the bottom of the ore pile and into the inserted PVC pipe by a blower, and the aeration rate is controlled at 0.8VVM (that is, the ratio of the volume of air introduced per minute to the volume of the ore pile is 0.8:1).

[0082] Liquid circulation: After being collected from the bottom of the ore pile, the leachate is filtered to remove a small amount of particulate matter and then sprayed back to the top of the ore pile every 4 hours. During the circulation process, the pH value is maintained at 1.5-2.0 using dilute sulfuric acid or dilute sodium hydroxide solution based on pH monitoring results.

[0083] Leaching duration: The bioleaching process lasts for 250 days.

[0084] Process monitoring: During the leaching process, samples were taken every 24 hours to monitor the pH, Eh, dissolved oxygen content, and system temperature of the leachate. Samples were taken every 3 days, and inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to analyze the concentration changes of major metal ions such as zinc and iron in the leachate. After leaching, tailings samples were taken from the ore heap, and the residual zinc content was analyzed using ICP-AES to calculate the leaching rate.

[0085] Leachate treatment and zinc recovery stage:

[0086] Iron impurity removal: The zinc-rich leachate collected after bioleaching is preliminarily filtered to remove suspended solids. Lime milk (e.g., 20% w / v calcium hydroxide suspension) is added to the filtrate and stirred slowly to raise the pH of the leachate to 3.0 ± 0.1.

[0087] During pH adjustment, an appropriate amount of oxidant (e.g., 30% hydrogen peroxide solution, the amount of which is 1.2 times the theoretical amount required for ferrous ion oxidation) is added to oxidize ferrous ions to ferric ions.

[0088] After stirring continuously for 2 hours, the mixture was allowed to stand and settle for 6 hours. The resulting iron sludge was then filtered and separated to obtain a zinc-rich solution after iron removal.

[0089] Chemical precipitation recovery of zinc:

[0090] The zinc-rich solution, after iron removal, was transferred to a reaction vessel and heated to 25±2℃, with a stirring rate of 100 rpm. Solid ammonium carbonate was slowly added to the solution, at an amount 1.1 times the theoretical amount required for zinc ion precipitation. Simultaneously, the pH of the solution was adjusted to 6.0±0.2 using dilute ammonia or dilute sulfuric acid. After stirring for 3 hours, stirring was stopped, and the mixture was allowed to settle for 1.5 hours. Solid-liquid separation was then performed using a plate and frame filter press. The precipitate was washed twice with deionized water, each time using 0.8 times the wet weight of the precipitate. It was then dried at 60℃ for 4 hours to obtain a high-purity zinc carbonate product. The remaining liquid after separation was ammonium sulfate liquid fertilizer, which, after passing inspection, was directly used in agricultural production.

[0091] Example 3:

[0092] This embodiment provides a novel bioleaching process for iron sphalerite tailings in high-altitude areas, including the following steps:

[0093] Bioleaching stage:

[0094] Raw material preparation: Take 2500 kg (2.5 tons) of tailings sample, with a particle size of 35% less than 0.074 mm. Thoroughly mix the pretreated tailings with 125 kg of active material components, with a tailings to active material component mass ratio of 100:5.

[0095] Ore pile construction: Construct the above mixture into a pile with a volume of approximately 5.0 m³. 3 The leached ore heap. 10-15 perforated PVC pipes are evenly inserted vertically and at a high density inside the ore heap. Each PVC pipe has a diameter of 100mm, with 10mm diameter holes drilled in its wall at 50mm intervals. The bottom of the PVC pipe is 100mm from the bottom of the ore heap, and the top extends 150mm above the surface of the ore heap.

[0096] Inoculation and Spray Leaching: The high-altitude adapted mineral leaching microbial community obtained in Preparation Example 1 was diluted with sterile 9K basal medium to prepare an initial concentration of 1x10⁻⁶. 8 A bacterial suspension of cells / mL.

[0097] The liquid-to-solid ratio of the tailings was 2.0 L / kg (i.e., a total of approximately 5000 L of bacterial suspension), which was then evenly sprayed onto the top of the ore pile using a spray system. The initial pH of the leachate was adjusted to 2.5 by adding dilute sulfuric acid.

[0098] Environmental control and liquid circulation:

[0099] Temperature control: The temperature of the leaching system is precisely controlled at 40±2℃ through a precise heat exchange system inside the ore pile.

[0100] Aeration control: Air is continuously introduced into the bottom of the ore pile and into the inserted PVC pipe by a high-flow blower, and the aeration rate is controlled at 1.5VVM (that is, the ratio of the volume of air introduced per minute to the volume of the ore pile is 1.5:1).

[0101] Liquid circulation: After being collected from the bottom of the ore pile, the leachate is filtered to remove a small amount of particulate matter and then sprayed back to the top of the ore pile every 4 hours. During the circulation process, the pH value is maintained at 2.0-3.0 using dilute sulfuric acid or dilute sodium hydroxide solution based on pH monitoring results.

[0102] Leaching duration: The bioleaching process lasts for 160 days.

[0103] Process monitoring: During the leaching process, samples were taken every 7 days to monitor the pH, Eh, dissolved oxygen content, and system temperature of the leachate. Samples were also taken daily, and inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to analyze the concentration changes of major metal ions such as zinc and iron in the leachate. After leaching, tailings samples were taken from the ore heap, and the residual zinc content was analyzed using ICP-AES to calculate the leaching rate.

[0104] Leachate treatment and zinc recovery stage:

[0105] Iron impurity removal: The zinc-rich leachate collected after bioleaching is preliminarily filtered to remove suspended solids. Lime milk (e.g., 20% w / v calcium hydroxide suspension) is added to the filtrate and stirred slowly to rapidly raise the pH of the leachate to 4.5 ± 0.1.

[0106] During pH adjustment, the addition of an oxidant (e.g., a 30% hydrogen peroxide solution, in an amount 1.5 times the theoretical amount required for ferrous ion oxidation) is precisely controlled to completely oxidize ferrous ions to ferric ions.

[0107] After stirring continuously for 1 hour, the mixture was allowed to stand and settle for 3 hours. The resulting iron sludge was then filtered and separated to obtain a zinc-rich solution after iron removal.

[0108] Chemical precipitation recovery of zinc:

[0109] The zinc-rich solution after iron removal was transferred to a reaction vessel and heated to 40±2℃, with a stirring rate of 200 rpm. Solid ammonium carbonate was slowly added to the solution, at an amount 1.3 times the theoretical amount required for zinc ion precipitation. Simultaneously, the pH of the solution was adjusted to 7.5±0.2 using dilute ammonia or dilute sulfuric acid. After stirring for 1 hour, stirring was stopped, and the mixture was allowed to settle for 0.5 hours. Solid-liquid separation was then performed using a plate and frame filter press. The precipitate was washed three times with deionized water, each time using 1.2 times the wet weight of the precipitate. It was then dried at 80℃ for 2 hours to obtain a high-purity zinc carbonate product. The residual liquid after separation was ammonium sulfate liquid fertilizer, which, after testing and confirming compliance with agricultural standards, was directly used for crop fertilization.

[0110] Comparative Examples 1-4:

[0111] Comparative Example 1: Pure Chemical Leaching

[0112] Compared to Example 1, the difference lies in that no microbial flora is inoculated during the leaching stage, the leachate contains no biological agents, and the leaching process relies entirely on chemical acid leaching. Specifically, the initial pH of the leachate is adjusted to 1.5-2.0 by adding pure sulfuric acid, and other environmental controls (such as temperature, aeration, and liquid circulation) and leaching time are the same as in Example 1. After leaching, the leachate treatment and zinc recovery stages are also the same as in Example 1.

[0113] Comparative Example 2: Bioleaching without aeration or PVC pipe assistance

[0114] Compared to Example 1, the difference lies in that continuous aeration is not performed during the bioleaching stage, and perforated PVC pipes are not inserted inside the ore pile to assist air circulation. That is, oxygen supply relies solely on natural diffusion from the surface of the ore pile. All other steps, including raw material preparation, ore pile construction (removing the PVC pipe portion), bacterial inoculation and spraying, temperature control, liquid circulation, leaching duration, and process monitoring, are the same as in Example 1. After leaching, the leachate treatment and zinc recovery stages are also the same as in Example 1.

[0115] Comparative Example 3: Bioleaching of non-high-altitude adapted microorganisms

[0116] Compared to Example 1, the difference lies in the microbial strain used in the bioleaching stage: *Acidithiobacillus ferrooxidans*, a strain routinely cultured in the laboratory, rather than the high-altitude adapted microbial community screened and domesticated in Example 1. The initial concentration of this strain, the inoculation method, and all operational parameters during the leaching process, including raw material preparation, ore pile construction, environmental control (temperature, aeration, liquid circulation), leaching duration, and process monitoring, are all the same as in Example 1. After leaching, the leachate treatment and zinc recovery stages are also the same as in Example 1.

[0117] Comparative Example 4: Iron Removal and Zinc Recovery Using Traditional Precipitation Methods

[0118] Compared to Example 1, the difference lies in the leachate treatment and zinc recovery stages. This comparative example does not use the ammonium carbonate chemical precipitation method, but instead employs the traditional sodium hydroxide precipitation method. Specifically, after removing iron impurities, sodium hydroxide solution is added to the solution to raise the pH to 8.0-9.0, causing zinc ions to precipitate as zinc hydroxide. After filtration, washing, and drying, the zinc hydroxide product is obtained. The residual liquid contains a high concentration of sodium salts and cannot be directly used in agriculture. All steps in its bioleaching stage are exactly the same as in Example 1.

[0119] Test Example 1-2:

[0120] Test Example 1:

[0121] Through a series of verification tests, the technical feasibility of the present invention in the process of extracting zinc and cobalt from high-altitude copper tailings and recovering zinc was clarified.

[0122] Determination of leaching rate of valuable metals:

[0123] Experimental Description: This test aims to quantify the leaching efficiency of zinc from tailings during bioleaching. The experiment was conducted according to the bioleaching process of one of the previously described embodiments. After bioleaching was started, 100 mL samples were drawn from the circulating leachate collected from the bottom of the ore heap every two days. The samples were filtered through a 0.45 μm filter membrane to remove suspended solids.

[0124] The concentration of zinc ions in the filtrate was quantitatively analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES). At the end of the leaching process, tailings samples were taken from the ore heap. After drying and grinding, the tailings samples underwent acid digestion pretreatment, followed by ICP-AES analysis to determine the residual zinc content. Based on the cumulative concentration of metal ions in the leachate and the residual metal content in the tailings, combined with the initial metal content of the tailings, the cumulative zinc leaching rate was calculated.

[0125] Table 1. Cumulative leaching rate of zinc during bioleaching

[0126] 16 8.50 32 18.00 48 32.00 64 48.00 80 62.00 96 72.50 112 78.00 128 80.80 144 81.20 160 81.28

[0127] Conclusion: The test results show that under the established bioleaching conditions, the cumulative leaching rate of zinc continuously increases over time. By the end of the leaching cycle, the zinc leaching rate reached 81.28%. This data indicates that the bioleaching method employed in this invention can effectively leach the target metal from high-altitude copper tailings. The improved leaching efficiency is mainly attributed to the metabolic activity of high-altitude adapted microbial communities and their sustained effect under optimized aeration and pH conditions, thereby promoting the decomposition of sulfide minerals and zinc oxide-containing minerals.

[0128] Dynamic monitoring of leaching process parameters:

[0129] Experimental Description: This test aims to monitor the dynamic changes of key physicochemical parameters during bioleaching to assess the stability and suitability of the leaching environment. The experiment was conducted according to the bioleaching process of one of the previously described embodiments.

[0130] After leaching is initiated, samples of the circulating leachate collected at the bottom of the ore heap are taken daily at a fixed time (e.g., 10:00 AM). The pH, Eh, and dissolved oxygen content of the leachate are measured in real time using a calibrated pH meter (glass electrode), redox potentiometer (Pt electrode), and dissolved oxygen meter. Simultaneously, a temperature sensor is used to record the internal temperature of the ore heap.

[0131] Table 2. Dynamic changes of key physicochemical parameters during bioleaching.

[0132] 16 2.05 425 3.1 29.5 32 2.12 458 2.9 30.1 48 2.08 471 3.2 29.8 64 2.15 492 2.8 30.3 80 2.01 510 3.0 30.0 96 2.18 525 2.7 30.5 112 2.07 538 3.1 30.2 128 2.10 545 2.9 29.9 144 2.03 553 3.0 30.4 160 2.11 560 2.8 30.1

[0133] Conclusion: The above data show that during the 160-day bioleaching process, the pH of the leachate remained within the suitable acidic range of 2.0-2.2, the redox potential continuously increased and remained at a high positive value (425-560 mV), the dissolved oxygen content was maintained at the level required for microbial activity (2.7-3.2 mg / L), and the system temperature was stably controlled at 29.5-30.5℃. The dynamic stability of these parameters confirms that the present invention, through optimized aeration, pH adjustment, and temperature control strategies, successfully created and maintained environmental conditions conducive to the activity of high-altitude adaptive leaching microbial communities, which is a prerequisite for achieving efficient leaching.

[0134] Microbial community structure analysis:

[0135] Experimental Description: This test aims to analyze the composition and dynamic succession of the microbial community during bioleaching to verify the effective role of high-altitude adaptive microbial communities. The experiment was conducted according to the bioleaching process of one of the previously described embodiments.

[0136] Samples were taken from the leachate on days 8, 80, and 160 after leaching was initiated. Microbial cells were collected by centrifugation, and microbial genomic DNA was subsequently extracted according to standard procedures. The extracted DNA was amplified by PCR of the 16S rRNA gene V3-V4 region and then sequenced using high-throughput sequencing. Bioinformatics analysis of the sequencing data was used to generate the species composition and relative abundance of the microbial community at different time points.

[0137] Table 3. Relative abundance changes of major genera in the microbial community during bioleaching.

[0138] Acidiphilium sp. 15.6 40.7 72.8 Sulfitobacter sp. 10.2 25.1 15.3 Leptospirillum sp. 5.8 18.9 7.1 Sulfolobus sp. 3.1 6.2 2.5 other 65.3 9.1 2.3

[0139] Conclusion: The test data show that the microbial community structure underwent significant succession during bioleaching. Species diversity was high in the initial stage, but as the leaching process progressed, the relative abundance of *Acidiphilium* sp. increased significantly from 15.6% to 72.8%, becoming the dominant genus. Simultaneously, *Sulfitobacter* sp. and *Leptospirillum* sp. also showed some presence and dynamic changes. This indicates that the present invention successfully enriched and maintained leaching microorganisms adapted to high-altitude environments, especially *Acidiphilium* sp., which dominated the leaching system. Its high abundance directly supported the oxidative dissolution of metal sulfides and zinc-containing minerals in the tailings, forming the core biological basis for achieving efficient metal leaching.

[0140] Mineral phase transformation analysis:

[0141] Experimental Description: This test aims to provide mineralogical evidence for the leaching mechanism by analyzing the mineral phase changes of tailings before and after bioleaching. The experiment was conducted according to the bioleaching process of one of the previously described embodiments.

[0142] Before bioleaching begins, the original tailings samples are taken, dried, and ground.

[0143] After the leaching process is completed, the treated tailings sample is taken, dried, and ground.

[0144] X-ray diffraction was used to analyze the phase composition of the raw tailings and final tailings samples. The characteristic diffraction peak intensities and 2θ values ​​of the main zinc-bearing mineral phases (such as sphalerite, hemimorphite, smithsonite, etc.) and the main iron-bearing sulfides (such as pyrite, pyrrhotite, etc.) were recorded.

[0145] Table 4. Changes in relative diffraction peak intensity of major mineral phases in tailings before and after bioleaching.

[0146] sphalerite 1856 312 Heterogeneous mineral 923 158 Pyrite 2130 487 carbonate minerals 350 295 quartz 6500 6450

[0147] Conclusion: X-ray diffraction analysis showed that after bioleaching, the intensity of characteristic diffraction peaks representing zinc-bearing minerals such as sphalerite and hemimorphite, as well as iron-bearing sulfide minerals such as pyrite, significantly decreased in the tailings samples. For example, the relative intensity of sphalerite decreased from 1856 to 312, and that of pyrite from 2130 to 487. In contrast, the diffraction peak intensity of quartz, an inert mineral, remained almost unchanged. This clearly indicates that during bioleaching, the crystal structure of the target zinc-bearing minerals and associated sulfide minerals underwent destruction and dissolution, thereby releasing valuable metal ions. This mineral phase transition data directly verifies the feasibility of the proposed method for metal extraction through a microbial-mediated mineral dissolution mechanism.

[0148] Numerical simulation analysis of seepage characteristics:

[0149] Experimental Description: This test aims to analyze the changes in seepage characteristics of the ore pile during long-term bioleaching in order to evaluate the stability and fluid transport efficiency of the ore pile.

[0150] A three-dimensional geometric model is established based on parameters such as the actual geometric dimensions of the ore pile, the initial particle size distribution of the tailings, compaction density, and porosity. Using Midas-GTSNX software, the aforementioned physical parameters are input, and spraying rates and bottom drainage conditions are applied to perform fluid dynamics calculations, analyzing the permeability distribution and liquid phase flow paths within the ore pile. By outputting the permeability coefficients and pressure gradients in different regions of the ore pile, the risk of localized blockage due to cementation is assessed.

[0151] Table 5. Variation of seepage coefficient and effective flow velocity in different areas of the ore pile

[0152] Top area <![CDATA[1.5x10 -5 ]]> <![CDATA[1.3x10 -5 ]]> 1.25 1.08 Central region <![CDATA[1.8x10 -5 ]]> <![CDATA[1.6x10 -5 ]]> 1.50 1.31 bottom area <![CDATA[1.3x10 -5 ]]> <![CDATA[1.1x10 -5 ]]> 1.08 0.90 Near PVC pipe <![CDATA[2.5x10 -5 ]]> <![CDATA[2.2x10 -5 ]]> 2.08 1.83

[0153] Conclusion: The simulation analysis of seepage characteristics shows that although the overall seepage coefficient and effective flow velocity of the ore pile decreased slightly throughout the entire bioleaching cycle, they remained within an acceptable range. For example, the seepage coefficient in the central region decreased from 1.8 x 10⁻⁶. -5 m / s decreased to 1.6 x 10 -5 m / s. In particular, the area near the PVC pipe consistently maintains a high permeability. This verifies that the present invention effectively maintains good permeability inside the ore pile by optimizing the ore pile construction (such as inserting PVC pipes) and aeration conditions, thereby ensuring the effective transport of leachate and oxygen and reducing the risk of decreased leaching efficiency due to slurry cementation.

[0154] Evaluation of iron impurity removal efficiency in leachate:

[0155] Experimental Description: This test aims to evaluate the effect of iron impurity removal technology on the iron ion concentration in bioleaching solutions. The experiment was conducted according to the leachate treatment process of one of the previously described embodiments.

[0156] Zinc-rich leachate samples were collected after bioleaching, and their initial iron ion concentration was determined using inductively coupled plasma atomic emission spectrometry (ICP-AES). The leachate was then subjected to pH adjustment and oxidation treatment, followed by sedimentation and filtration.

[0157] Take a sample of the filtrate after iron removal and measure the iron ion concentration again using inductively coupled plasma atomic emission spectrometry. Calculate the iron ion removal rate.

[0158] Table 6. Removal effect of iron impurities in leachate

[0159] initial leachate 18.5 Iron-removed filtrate 0.08 Iron removal rate (%) 99.57

[0160] Conclusion: Test data show that after pH adjustment and oxidation precipitation treatment according to the present invention, the iron ion concentration in the leachate decreased from the initial 18.5 g / L to 0.08 g / L, with an iron removal rate as high as 99.57%. This result indicates that the iron removal process adopted in the present invention can efficiently remove a large amount of iron ions from the leachate, effectively reducing the impact of iron on product purity during subsequent zinc recovery, and providing a pure feed solution for further zinc refining.

[0161] Performance evaluation of zinc recovery by chemical precipitation:

[0162] Experimental Description: This test aims to evaluate the effectiveness of zinc recovery via chemical precipitation, including zinc recovery rate, product purity, and the utilization value of residual liquid. The experiment was conducted according to the leachate treatment process of one of the previously described embodiments. A zinc-rich solution after iron removal was used as the feed liquid for chemical precipitation, and its zinc ion concentration was measured. Ammonium carbonate was added according to the set process parameters to carry out the precipitation reaction. After filtration, washing, and drying, zinc carbonate product was obtained. Inductively coupled plasma atomic emission spectrometry (ICP-AES) was used to analyze the zinc ion concentration in the feed liquid, the zinc content in the zinc carbonate product, and the impurity content, and the zinc recovery rate and product purity were calculated. The residual liquid was analyzed to detect the ammonium sulfate concentration and heavy metal content, and its feasibility for agricultural application was assessed.

[0163] Table 7. Performance Indicators of Zinc Recovery by Chemical Precipitation

[0164] Zinc concentration in feed solution (mg / L) 3500 Purity (%) of zinc carbonate product 99.3 Zinc recovery rate (%) 95.8 Iron impurity content of the product (mg / kg) 85 Residual liquid ammonium sulfate concentration (g / L) 180 Residual heavy metal content in liquid (mg / L) All are below the agricultural standard limit. Residual liquid agricultural applicability Meets liquid fertilizer standards and can be used directly.

[0165] Conclusion: The performance test results of this chemical precipitation method for zinc recovery show that the ammonium carbonate precipitation method can effectively separate zinc from impurities such as iron in the leachate, achieving a zinc recovery rate of 95.8% and a product purity of 99.3%. The residual liquid can be directly used as agricultural fertilizer. This data confirms that the chemical precipitation technology used in this invention can effectively separate zinc from impurities such as iron in the leachate, allowing the zinc-rich solution to be directly used for subsequent high-purity zinc recovery. This significantly improves the purity and recovery efficiency of the zinc product while reducing secondary pollution caused by traditional chemical precipitation methods.

[0166] Test Example 2:

[0167] The comparative tests aimed to comprehensively evaluate the performance advantages of the present invention compared to existing or alternative technologies, highlighting its innovation and efficiency in the leaching, separation, and recovery of valuable metals. All comparative tests were conducted under the conditions of the corresponding embodiments and comparative examples described above, and no microstructure characterization was performed.

[0168] Comparison of leaching efficiency of valuable metals:

[0169] Experimental Description: This test aims to compare the zinc leaching efficiency of the present invention (Examples 1, 2, and 3) with that of pure chemical leaching (Comparative Example 1), bioleaching without auxiliary aeration (Comparative Example 2), and bioleaching using non-high-altitude adapted microorganisms (Comparative Example 3).

[0170] Bioleaching or chemical leaching experiments were conducted according to the conditions specified in Examples 1, 2, 3, Comparative Examples 1, 2, and 3, respectively. At the end of the leaching process (according to the leaching time specified in each example / comparative example), tailings samples were collected from each experimental system, dried, and ground. The tailings samples were pretreated using acid digestion, and then the residual zinc content was analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES). Based on the zinc content in the original tailings and the residual zinc content in the tailings, the final zinc leaching rate in each system was calculated.

[0171] Table 8. Comparison of final zinc leaching rates under different leaching methods

[0172] Example 1 160 81.28 Example 2 250 70.15 Example 3 160 89.72 Comparative Example 1 (purely chemical) 160 40.18 Comparative Example 2 (No Aeration) 160 53.25 Comparative Example 3 (Non-adapted bacteria) 160 48.36

[0173] Conclusion: Comparative test results show that the embodiments of the present invention (Examples 1, 2, and 3) are significantly superior to the comparative examples in terms of zinc leaching efficiency. Example 3 achieved a zinc leaching rate of 89.72% within 160 days, while Examples 1 and 2 also exhibited good leaching performance. In contrast, Comparative Example 1 (pure chemical leaching) had the lowest leaching rate due to the lack of microbial catalysis. Comparative Example 2 (non-aeration bioleaching) suffered from limited oxygen supply, which inhibited microbial activity, resulting in a lower leaching efficiency than the embodiments of the present invention. Comparative Example 3 (non-altitude-adapted microbial bioleaching) also had a much lower leaching efficiency than the present invention because the microbial strain could not adapt to the extreme high-altitude environment. These data fully demonstrate that the present invention, by employing screened and domesticated high-altitude-adapted microbial communities, supplemented by optimized aeration and environmental control, can effectively improve the leaching efficiency of the target metal, surpassing traditional chemical methods and unoptimized bioleaching pathways.

[0174] Comparison of stability and persistence in the leaching process:

[0175] Experimental Description: This test aims to compare the stability of environmental parameters (such as pH value and Eh value) and the sustainability of leaching efficiency of the present invention and the comparative example during the leaching process.

[0176] Leaching experiments were conducted under the specified conditions of Example 1, Comparative Example 1, Comparative Example 2, and Comparative Example 3.

[0177] Throughout the leaching cycle, the pH and Eh values ​​of the leachate for each system were monitored every 3 days, and their trends were recorded. Simultaneously, samples were taken periodically (e.g., every 5 days) and the cumulative zinc concentration in the leachate was measured to assess the sustainability of the leaching rate.

[0178] Table 9. Comparison of pH and Eh stability and leaching rate for different leaching schemes

[0179] Example 1 160 2.11 0.08 505 35 0.0173 Comparative Example 1 160 1.85 0.25 380 60 0.0085 Comparative Example 2 160 2.52 0.15 420 48 0.0113 Comparative Example 3 160 2.30 0.12 400 55 0.0103

[0180] Conclusion: Data shows that Example 1 exhibited the best pH and Eh stability during the leaching cycle, with lower pH standard deviation (0.08) and Eh standard deviation (35mV) than other comparative examples, indicating that the leaching environment remained stable and conducive to the activity of leaching microorganisms. Correspondingly, Example 1 also had the highest average zinc leaching rate (0.128 gZn / kg tailings / day). Comparative Example 1 (pure chemical leaching) showed greater fluctuations in pH and Eh, with generally lower Eh values, which was unfavorable for oxidative leaching. Comparative Example 2 (no aeration) suffered from limited microbial activity due to oxygen deficiency, resulting in higher and more volatile pH values, and the Eh value was not effectively improved. Comparative Example 3 (non-adapted bacteria) had poor leaching environment stability and a lower leaching rate due to the inability of the bacterial species to adapt to the environment. These results confirm that the present invention, through the buffering effect of high-altitude adapted microbial communities and precise environmental control, can provide more stable and continuous leaching conditions, thereby ensuring long-term and efficient metal leaching.

[0181] Comparison of zinc and iron separation effects:

[0182] Experimental Description: This test aims to compare the effects of the ammonium carbonate chemical precipitation method (Example 1) and the traditional sodium hydroxide precipitation method (Comparative Example 4) on the zinc-iron separation efficiency and zinc product purity when treating zinc-rich leachate, and to compare the utilization value of the residual liquid. The zinc-rich leachate obtained from bioleaching was subjected to iron removal and zinc recovery treatment according to the specifications of Example 1 and Comparative Example 4, respectively. The zinc and iron contents in the iron-removed solution (Example 1) and the final zinc product (Comparative Example 4) were analyzed using inductively coupled plasma atomic emission spectrometry (ICP-AES). The iron removal rate and the purity of the zinc product (defined as the percentage of zinc in the total metal content) were calculated, and the composition and uses of the residual liquid were evaluated.

[0183] Table 10. Comparison of Zinc-Iron Separation Effects and Overall Performance of Different Separation Schemes

[0184] Example 1 (Ammonium carbonate precipitation) 99.57 85mg / kg (in the product) 99.3 95.8 Ammonium sulfate liquid fertilizer, for direct use in agriculture. Comparative Example 4 (Traditional Precipitation) 90.1 0.5% (in zinc precipitate) 85.6 88.0 Wastewater containing sodium salts needs to be treated before discharge.

[0185] Conclusion: The test results show that the ammonium carbonate chemical precipitation method (Example 1) used in this invention exhibits significant advantages in zinc-iron separation. Example 1 achieved an iron removal rate of 99.57% and a zinc product purity of 99.3%, with the residual liquid suitable for direct use as agricultural fertilizer. In contrast, Comparative Example 4 (traditional precipitation method), while also removing most of the iron, had lower iron removal rates (90.1%) and zinc product purity (85.6%) than Example 1, and the final zinc product still contained a high proportion of iron impurities (0.5%), affecting product quality. This indicates that the ammonium carbonate chemical precipitation method provides higher separation selectivity, effectively solving the problem of traditional precipitation methods failing to achieve efficient zinc-iron separation and high-purity zinc recovery, significantly improving the added value of zinc products and the economic efficiency of the recovery process.

[0186] Tailings grade comparison:

[0187] This test aims to compare the zinc residue level in the tailings after leaching of the present invention (Example 1) with that of comparative examples (Comparative Examples 1, 2, and 3) to evaluate the completeness of valuable metal extraction. Leaching experiments were conducted according to the conditions specified in Examples 1, 1, 2, and 3. The final tailings samples from each experimental system were dried, ground, and analyzed for zinc residue content using acid digestion inductively coupled plasma atomic emission spectrometry.

[0188] Table 11. Comparison of residual zinc grades in tailings from different leaching schemes

[0189] Example 1 0.064 Comparative Example 1 (purely chemical) 0.203 Comparative Example 2 (No Aeration) 0.159 Comparative Example 3 (Non-adapted bacteria) 0.176

[0190] Conclusion: The tailings grade comparison results show that the residual zinc grade in the tailings treated by the present invention (Example 1) is the lowest (0.064 wt%). This indicates that Example 1 can more thoroughly extract valuable metals from tailings, maximizing resource recovery. In contrast, the residual zinc grades in the tailings of Comparative Examples 1, 2, and 3 are significantly higher, reflecting the limitations of these methods in metal leaching efficiency, resulting in more valuable metals remaining in the tailings and causing resource waste. This result further emphasizes the superiority of the present invention in improving valuable metal recovery and reducing tailings grade, which is of great significance for realizing tailings resource utilization and reducing environmental impact.

Claims

1. A novel bioleaching process for iron-bearing sphalerite in tailings from high-altitude areas, characterized in that, include: (a) Bioleaching stage: The tailings are mixed with a high-altitude-adapted leaching microbial community to construct a ore pile, and heap leaching is carried out by spraying a bacterial suspension to obtain a zinc-rich leachate; (b) Iron removal stage of leaching solution: solid-liquid separation is performed on the leaching solution, and the pH value of the leaching solution is adjusted. At the same time, an oxidant is added to precipitate and separate iron ions to obtain a zinc-rich solution after iron removal. (c) Chemical precipitation recovery of zinc stage: Ammonium carbonate is added to the zinc-rich solution after iron removal, and the pH value of the solution is adjusted to 6.0-7.5 to convert zinc ions into zinc carbonate precipitate. After filtration, washing and drying, high-purity zinc carbonate product is obtained. The residual liquid is ammonium sulfate liquid fertilizer, which can be directly used in agricultural production.

2. The novel bioleaching process for iron sphalerite tailings in high-altitude areas according to claim 1, characterized in that, Before step (a), the tailings particle size is further reduced to 20%-85% less than 0.074 mm.

3. The novel bioleaching process for iron-bearing sphalerite in tailings from high-altitude areas according to claim 1, characterized in that, The high-altitude adapted mineral leaching microbial community described in step (a) is obtained through the following steps: The bacterial source was collected from high-altitude mining areas and enriched in 9K basal medium with ferrous sulfate heptahydrate as the sole energy source. Then, in a culture medium with added tailings powder, gradient acclimatization was carried out by gradually increasing the tailings slurry concentration, decreasing the dissolved oxygen concentration, decreasing the culture temperature, and intermittent ultraviolet irradiation to enhance the adaptability of the high-altitude leaching microbial community to the high-altitude environment and its leaching activity on the target tailings.

4. A novel bioleaching process for iron-bearing sphalerite in tailings from high-altitude areas, as described in claim 1, is characterized in that... In step (a), the mass ratio of the tailings to the high-altitude adaptive leaching microbial community is 100:(0.5-5); The initial concentration of the bacterial suspension was 1x10⁻⁶. 6 -1x10 8 Cells / mL, liquid-to-solid ratio of spray is 5.5-20.0 L / mL 3 Tailings.

5. A novel bioleaching process for iron-bearing sphalerite in tailings from high-altitude areas according to claim 1, characterized in that, In step (a), the temperature of the heap leaching is controlled at 5-40℃, the aeration rate is controlled at 0.8-1.5VVM, the pH value is maintained at 1.5-3.0, and the leaching time is 150-250 days.

6. A novel bioleaching process for iron-bearing sphalerite in tailings from high-altitude areas according to claim 1, characterized in that, In step (a), perforated PVC pipes are uniformly inserted vertically inside the ore pile for aeration. The diameter of the PVC pipes is 50-100mm, and holes with a diameter of 5-10mm are drilled on the pipe walls with a spacing of 50-100mm.

7. A novel bioleaching process for iron-bearing sphalerite in tailings from high-altitude areas according to claim 1, characterized in that, In step (b), lime milk is used to adjust the pH of the leachate to 3.0-4.

5. The oxidant is hydrogen peroxide, sodium peroxide and potassium permanganate, etc., and the amount of oxidant used is 1.2-1.5 times the amount required for theoretical oxidation of ferrous ions.

8. A novel bioleaching process for iron-bearing sphalerite in tailings from high-altitude areas according to claim 1, characterized in that, In step (c), the amount of ammonium carbonate added is 1.1-1.3 times the amount required for theoretical zinc ion precipitation, the reaction temperature is controlled at 15-40℃, the stirring rate is 100-200rpm, and the reaction time is 3-6 hours.