A method for strengthening arsenic pyrite bioleaching and synchronously immobilizing arsenic from a biological source

Abstract

The application discloses a method for strengthening arsenic pyrite bioleaching and synchronously fixing arsenic by biological source, and belongs to the technical field of bio-metallurgy and mine environment treatment. The method is characterized by the following steps: domesticating acidophilic ferrous-oxidizing bacteria through an arsenic-containing pyrite culture medium, and then using the obtained arsenic-resistant domesticated bacteria solution to biosynthesize biological source Schimper mineral; mixing the prepared biological source Schimper mineral with target arsenic pyrite uniformly, and adding the arsenic-resistant domesticated bacteria solution to perform a bioleaching reaction, thereby realizing in-situ fixation of arsenic. The method uses the strong adsorption capacity of the biological source Schimper mineral to liquid-phase arsenic ions to quickly reduce the concentration of free arsenic, thereby removing the toxic inhibition of arsenic on acidophilic microorganisms and shortening the microbial adaptation period. Meanwhile, the Schimper mineral is partially dissolved in an acidic leaching environment to release Fe 3+ and As 5+ co-precipitate to form arsenic acid iron minerals, thereby realizing in-situ stabilization and fixation of arsenic.

Description

Technical Field

[0001] This invention relates to a method for bioleaching arsenopyrite, specifically a method for enhancing the bioleaching of arsenopyrite from bio-derived Scheres minerals and simultaneously fixing arsenic, belonging to the fields of biometallurgy and mine environmental remediation technology. Background Technology

[0002] Arsenic pyrite (FeAsS) is one of the most widely distributed arsenic-bearing sulfide minerals in nature, often occurring in association with gold, silver, copper, tin, and other polymetallic minerals. In gold mineral resources, arsenopyrite is one of the most typical gold-bearing minerals. Gold is often encapsulated in the arsenopyrite crystal lattice in a fine-grained or submicroscopic form. This encapsulation makes it difficult to directly recover gold using conventional cyanide leaching processes, with leaching rates typically below 30%. Therefore, pre-oxidation treatment of gold-bearing arsenopyrite to disrupt its crystal structure and dissociate the encapsulated gold is a crucial prerequisite for efficient gold recovery. Currently, pre-oxidation methods for gold-bearing arsenopyrite mainly include three categories: roasting oxidation, pressure oxidation, and biological oxidation. While roasting oxidation is a mature technology, it suffers from high energy consumption, severe arsenic-containing dust pollution, and the need for a supporting exhaust gas treatment system, resulting in high environmental pressure and operating costs. Pressure oxidation requires high-temperature and high-pressure conditions, placing high demands on equipment materials and incurring significant investment and maintenance costs. In contrast, bio-oxidation technology has advantages such as mild reaction conditions, low energy consumption, and environmental friendliness, and has become an important development direction in the field of pre-oxidation of refractory gold ores.

[0003] In biological oxidation systems, iron / sulfur oxidizing microorganisms such as *Acidithiobacillus ferrooxidans* are key biological factors driving the oxidative dissolution of arsenopyrite. These microorganisms oxidize Fe... 2+ Fe 3+ Sulfur oxides obtain energy from sulfate ions, and Fe is produced simultaneously. 3+ As a strong oxidizing agent, it further accelerates the chemical oxidation of arsenopyrite. However, the oxidation of arsenopyrite releases large amounts of highly toxic inorganic arsenic (As). 3+ And As 5+Arsenic ions accumulated in the liquid phase are significantly toxic to acidophilic microorganisms, inhibiting their growth and metabolic activity, forming a negative feedback loop of "oxidation-arsenic release-inhibition." This limits the oxidation rate and prolongs the oxidation cycle of arsenopyrite, severely restricting the industrial application efficiency of biological pre-oxidation technology. Meanwhile, in the gold extraction process from gold-bearing arsenopyrite, the oxidation liquid usually needs to enter the subsequent cyanide gold extraction process. However, the high concentration of arsenic in the liquid phase reacts with cyanide to form arsenic cyanide complexes, not only consuming large amounts of sodium cyanide and increasing reagent costs, but also reducing gold leaching efficiency and even causing the gold leaching process to fail. In traditional processes, arsenic-containing oxidation liquids need to undergo arsenic removal processes such as neutralization precipitation and iron salt flocculation before meeting emission standards or entering the subsequent gold extraction process. This process not only consumes large amounts of neutralizing agents (such as lime) and iron salts, generating large amounts of arsenic-containing waste residue and increasing solid waste disposal costs, but also has complex operating procedures and high control requirements; even slight negligence can lead to secondary arsenic release. If the simultaneous stabilization and fixation of arsenic during the oxidation process of arsenopyrite can be achieved, so that arsenic exists in the oxidation slag in the form of a stable mineral phase, the subsequent arsenic removal process can be greatly simplified, the consumption of reagents and the amount of waste slag generated can be reduced, and the economic efficiency and environmental friendliness of the metallurgical process can be significantly improved.

[0004] Schwertmannite is a secondary iron hydroxyl sulfate mineral widely found in acidic mine drainage (AMD) environments, with the chemical composition Fe8O8(OH)6(SO4)·nH2O. Schwertmannite possesses a large specific surface area (up to 100–200 m²). 2 The surface is rich in hydroxyl functional groups ( / g), and its unique tunnel structure contains exchangeable SO42-. 2- Ions, giving them an affinity for As 3+ And As 5+ It exhibits excellent adsorption performance, with a saturated adsorption capacity reaching 113.9 mg / g. Furthermore, Schiele minerals possess a degree of metastable behavior under acidic conditions, allowing for the slow dissolution and release of Fe in specific environments. 3+ However, current applications of Scheringer minerals are mainly focused on arsenic adsorption and removal in environmental remediation—for example, using biosynthesized Scheringer minerals to remove arsenic from groundwater—and there are no reports of systematic methods for using them as bioleaching promoters to enhance the oxidative leaching of gold-bearing arsenopyrite and simultaneously regulate arsenic fate. Establishing a Scheringer mineral-based bio-oxidation process for arsenopyrite could potentially solve the two key technical bottlenecks of "low oxidation efficiency" and "difficult arsenic treatment." Therefore, developing a method to enhance the bio-oxidation efficiency of gold-bearing arsenopyrite, shorten the oxidation cycle, and simultaneously achieve in-situ arsenic stabilization and fixation using Scheringer minerals has significant technical value and broad application prospects for improving resource utilization in refractory gold ores, simplifying subsequent metallurgical arsenic removal processes, and reducing production costs and environmental risks. Summary of the Invention

[0005] To address the problems existing in the prior art, the present invention aims to provide a method for enhancing the bioleaching of arsenopyrite with bio-derived Schehertz minerals and simultaneously fixing arsenic. This method involves acclimating *Thiobacillus acidophilus* to arsenic tolerance in a culture medium containing arsenopyrite, then using the resulting arsenic-tolerant acclimated bacterial solution to biosynthesize Schehertz minerals. The prepared bio-derived Schehertz minerals are then uniformly mixed with the target arsenopyrite, and the arsenic-tolerant acclimated bacterial solution is added to initiate a bioleaching reaction, thereby achieving in-situ solidification of arsenic.

[0006] To achieve the above-mentioned technical objectives, the present invention provides a method for bioleaching and simultaneous arsenic fixation of bio-derived Scheres mineral-enhanced arsenopyrite, comprising:

[0007] Step S1: Inoculate Acidophilus ferrooxidans into a culture medium containing arsenic pyrite powder for arsenic tolerance acclimatization culture to obtain arsenic tolerance acclimatized bacterial solution;

[0008] Step S2: Inoculate the arsenic-tolerant acclimatization bacteria solution into ferrous sulfate solution, and after cultivation, filter, wash and dry to obtain bio-derived Scheres mineral;

[0009] Step S3: Mix the bio-source Scheres ore and the target arsenopyrite at a mass ratio of 0.9~1.1:0.9~1.1, add arsenic-resistant acclimatization bacteria solution to construct a bioleaching system, carry out the bioleaching reaction, and fix arsenic in situ.

[0010] The initial bacterial concentration in the bioleaching system was 1×10⁻⁶. 7 ~4×10 7 per mL.

[0011] The method provided by this invention uses arsenic-tolerant acclimatization bacterial solution to obtain bio-derived Scheres minerals. It utilizes the strong adsorption capacity of Scheres minerals for liquid-phase arsenic ions to rapidly reduce the concentration of free arsenic, thereby relieving the toxic inhibitory effect of arsenic on acidophilic microorganisms and shortening the microbial adaptation period. Simultaneously, it utilizes the Fe released from the partial dissolution of Scheres minerals in an acidic leaching environment. 3+ With As 5+ Co-precipitation forms ferric arsenate minerals, achieving in-situ stabilization and fixation of arsenic, thereby solving the problems of arsenic toxicity leading to inhibited microbial activity, low oxidation rate, and long oxidation cycle in existing bioleaching of arsenic pyrite.

[0012] As a preferred embodiment, the arsenic-tolerant acclimatization process is as follows: *Acidithiobacillus ferrooxidans* is inoculated into 9K medium containing arsenic pyrite powder. After the microorganisms enter the logarithmic growth phase, the cells are collected by centrifugation and transferred to a new arsenic pyrite medium. This process is repeated 2-3 times. In this invention, too few subcultures may result in insufficient acclimatization and limited improvement in the strain's arsenic tolerance; too many subcultures not only prolong the process preparation time but also may cause the strain's specific adsorption / oxidation capacity on the arsenic pyrite surface to degrade with continuous subculturing. Therefore, 2-3 subcultures achieve the optimal balance between acclimatization effect and time cost.

[0013] As a preferred embodiment, the amount of arsenopyrite powder added to the culture medium is 4.5~5.5 g / L; the conditions for arsenic tolerance acclimatization culture are: temperature 25~35℃, shaking speed 150~200 rpm, and culture period 5~7 days.

[0014] As a preferred embodiment, the process for obtaining the bio-derived Scheres mineral is as follows: Step S2-1, washing the arsenic-resistant acclimatization bacterial solution with dilute sulfuric acid at pH=3.0~3.2 to remove residual iron ions, and diluting the bacterial concentration to 1×10⁻⁶. 8 ~4×10 8 Cells / mL;

[0015] Step S2-2: Adjust the pH of the ferrous sulfate solution to be the same as that of the cleaned arsenic-tolerant acclimatization bacterial solution using dilute sulfuric acid, and then proceed with inoculation, cultivation, washing, and drying in sequence to obtain the final product.

[0016] In the process of obtaining biogenic Scherstein minerals, if the initial bacterial concentration is too low, Fe... 2+ A long oxidation induction period prolongs the synthesis cycle; while an excessively high inoculum concentration may shorten the synthesis time, cell autolysis or accumulation of metabolites may interfere with the crystal growth of Schiele minerals.

[0017] As a preferred embodiment, the concentration of the ferrous sulfate solution is 0.15~0.20 mol / L; the culture conditions are: temperature 25~35℃, shaking speed 150~200 rpm, and culture time 2~4 days.

[0018] Too low a concentration of ferrous sulfate solution will result in low mineral yield and insufficient synthesis efficiency; too high a concentration may lead to Fe... 2+ Incomplete oxidation or excessive local supersaturation can produce iron precipitates that are not part of the Schiele mineral phase, such as jaundice iron alum, which affects the phase purity of the product and its arsenic adsorption performance.

[0019] As a preferred embodiment, the washing process is as follows: the mineral sample is washed 2-3 times with dilute sulfuric acid at pH 3.0-3.2 to remove adsorbed microorganisms and soluble iron.

[0020] The reason this invention controls the pH during the washing process is that when the pH is below 3.0, the Schiele mineral itself may undergo a certain degree of acid dissolution, leading to mineral loss and surface structure damage. Conversely, when the pH is above 3.2, Fe... 3+ Hydrolysis precipitation may occur, forming a non-Schätner mineral phase iron oxide / hydroxy oxide coating layer on the mineral surface, affecting the intrinsic adsorption properties of Schätner minerals. Furthermore, the pH of the washing solution should be consistent with the pH of the Schätner mineral synthesis system to maintain the surface chemical state of the minerals to the greatest extent.

[0021] As a preferred embodiment, the initial pH of the bioleaching system is ≤3.0; the bioleaching reaction time is 20-30 days.

[0022] As a preferred embodiment, the conditions for the bioleaching reaction are as follows: the initial pH of the bioleaching system is 2.0~2.5, the temperature is 25~35℃, and the shaking speed is 150~200 rpm.

[0023] Compared with the prior art, the beneficial technical effects of the technical solution provided by the present invention are as follows:

[0024] 1) The method provided by this invention utilizes bio-derived Scheres minerals to partially dissolve and release Fe while promoting the oxidation of arsenopyrite. 3+ With As in the liquid phase 5+ A co-precipitation reaction occurs, generating amorphous iron arsenate minerals, thereby achieving irreversible stabilization and fixation of arsenic. Furthermore, the arsenic is fixed in the leaching residue as a stable mineral phase, which can significantly reduce the consumption of subsequent neutralizing agents and iron salts, reduce the amount of arsenic-containing waste residue generated, and effectively reduce the risk of secondary arsenic release.

[0025] 2) The bio-derived Scheres mineral in the technical solution provided by this invention, with its high specific surface area and abundant surface hydroxyl functional groups, rapidly adsorbs As in the liquid phase during the initial stage of the leaching reaction. 3+ And As 5+ This method effectively reduces the concentration of free arsenic, relieves the toxic inhibition of arsenic on *Thiobacillus acidophilus*, shortens the microbial adaptation period from the conventional 10 days or more to 3-5 days, and advances the time for the microbial population to reach its maximum growth rate by more than 50%. Tests showed that under optimal conditions of a 1:1 mass ratio of Scheres' mineral to arsenopyrite and an initial pH of 2.0, the oxidation rate of arsenopyrite reached over 88.77% after 7 days of reaction, approximately 1.86 times that of the control group without Scheres' mineral.

[0026] 3) The technical solution provided by this invention utilizes a microbial-driven natural mineralization process, which does not require the addition of chemical oxidants or surfactants, thus avoiding secondary pollution. The Scheres mineral can be synthesized in situ by microorganisms, and the remaining raw materials are inexpensive and readily available. The process conditions are mild and easy to promote and apply on-site in mines. In addition, this invention can also adapt to the leaching requirements of arsenopyrite of different grades and particle sizes by adjusting the proportion of Scheres mineral. It can also be used in combination with other pre-oxidation technologies for refractory gold ores, and has good versatility and industrialization prospects. Attached Figure Description

[0027] Figure 1 These are graphs showing the changes in solution parameters during the leaching process in Example 1 and Comparative Examples 1-4 of the present invention.

[0028] in, Figure 1 a is the As leaching rate diagram. Figure 1 b represents As in the liquid phase 3+ The ratio of arsenic to total arsenic, Figure 1 c is the total iron concentration graph. Figure 1 d is the ferrous iron concentration graph. Figure 1 e represents the bacterial concentration graph. Figure 1 f is the pH graph of the solution;

[0029] Figure 2 The XRD patterns of arsenopyrite leaching after 7 days and 20 days in Example 1 and Comparative Examples 1-4 of this invention are shown; wherein, Figure 2 a is the XRD pattern after 7 days of leaching. Figure 2 b is the XRD pattern after 20 days of leaching;

[0030] Figure 3 This is a SEM-EDS image of the surface of arsenopyrite and secondary minerals after 20 days of reaction in Example 1 of the present invention.

[0031] in, Figure 3 Image a shows the SEM image and elemental composition of the surface of arsenopyrite and its secondary minerals. Figure 3 b is a map showing the Fe distribution on the surface of arsenopyrite and secondary minerals. Figure 3 c is the S distribution diagram on the surface of arsenopyrite and secondary minerals. Figure 3 d shows the As distribution on the surface of arsenopyrite and secondary minerals. Figure 3 e is a diagram showing the O distribution on the surface of arsenopyrite and secondary minerals;

[0032] Figure 4 These are the leaching parameter variation curves of Examples 1-3, Comparative Example 5, and their corresponding control groups without Schiele minerals of the present invention;

[0033] in, Figure 4 a is the As leaching rate diagram. Figure 4b represents As in the liquid phase 3+ The ratio to total arsenic, Figure 4 c is the total iron concentration graph. Figure 4 d represents the ferrous iron concentration graph;

[0034] Figure 5 The XRD patterns of Examples 1-3, Comparative Example 5, and their corresponding control groups without Schiele minerals are shown below.

[0035] in, Figure 5 a is the XRD pattern of Examples 1-3 and Comparative Example 5. Figure 5 b is the XRD pattern of the control group;

[0036] Figure 6 The images show SEM images and local EDS energy dispersive spectroscopy analysis of the surface morphology of arsenopyrite after 22 days of reaction in Examples 1-3 and Comparative Example 5 of this invention.

[0037] in, Figure 6 a is the SEM image of Comparative Example 5. Figure 6 b is the element percentage diagram for Comparative Example 5. Figure 6 c is the SEM image of Example 1. Figure 6 d is the element proportion diagram of Example 1. Figure 6 e is the SEM image of Example 2. Figure 6 f is the element proportion diagram of Example 2. Figure 6 g is the SEM image of Example 3. Figure 6 h is the element percentage diagram for Example 3. Detailed Implementation

[0038] The technical solution of the present invention will be further described in detail below with reference to specific embodiments, but the implementation of the present invention is not limited thereto. It should be understood that the following embodiments are only used to explain and illustrate the present invention, and do not constitute any limitation on the scope of protection of the present invention. All equivalent transformations, modifications and improvements made based on the concept and spirit of the present invention should be included within the scope of protection of the present invention.

[0039] Example 1

[0040] This embodiment provides a method for bioleaching and simultaneous arsenic fixation of bio-derived Scheres' mineral-enhanced arsenopyrite. The specific process is as follows:

[0041] 1) *Acidithiobacillus ferrooxidans* was inoculated into 9K medium containing arsenic pyrite powder at a concentration of 5 g / L. The culture conditions were: 30°C, 170 rpm shaking speed, and a culture period of 5 days. After the microorganisms entered the logarithmic growth phase, the cells were collected by centrifugation and transferred to fresh arsenic pyrite medium. This culture period was repeated three times to obtain an arsenic-tolerant bacterial culture adapted to a high-arsenic environment.

[0042] 2) Prepare a 0.16 mol / L FeSO4·7H2O solution, adjust the pH to 3.0 with dilute sulfuric acid, place it in a reaction vessel, centrifuge and concentrate the arsenic-tolerant acclimatization bacterial solution from step 1), wash twice with dilute sulfuric acid at pH 3.0 to remove residual iron ions, and set the initial bacterial concentration at 2 × 10⁻⁶. 8 Inoculate 1 / mL of the above ferrous sulfate solution; incubate at 30±2℃ and 170 rpm in a constant temperature shaker for 72 hours, during which Fe 2+ Oxidized by microorganisms to Fe 3+ Hydrolysis and precipitation form Schiele minerals; after the reaction is complete, the precipitate is collected by filtering with filter paper, and the mineral sample is washed twice with dilute sulfuric acid at pH 3.0 to remove adsorbed microorganisms and soluble iron. It is then dried in a vacuum drying oven to constant weight to obtain bio-derived Schiele minerals.

[0043] 3) Mix 0.25g of Schönbrunné mineral and 0.25g of arsenopyrite at a mass ratio of 1:1. Place the mixed mineral in a 250 mL Erlenmeyer flask, add the arsenic-tolerant acclimatization bacterial solution from step 1), and control the initial bacterial concentration in the reaction system to be 2 × 10⁻⁶. 7 The sample was prepared at a concentration of 100 samples per mL, and the initial pH of the system was adjusted to 3.0 with dilute sulfuric acid. The reaction system was then carried out in a constant temperature shaker at 30°C and 180 rpm for 20 days.

[0044] Comparative Example 1

[0045] This comparative example is exactly the same as Example 1, except that: 0.05 g of Schiele mineral and 0.45 g of arsenopyrite were used, with a mass ratio of 1:9.

[0046] Comparative Example 2

[0047] This comparative example is exactly the same as Example 1, except that: 0.45 g of Schiele mineral and 0.05 g of arsenopyrite were used, with a mass ratio of 9:1.

[0048] Comparative Example 3

[0049] This comparative example is exactly the same as Example 1, except that no Schiele minerals are added, and 0.50g of arsenopyrite is added.

[0050] Comparative Example 4

[0051] This comparative example is exactly the same as Example 1, except that: no Scheres minerals are added, no arsenic-tolerant acclimatization bacteria are inoculated, and 0.50 g of arsenopyrite is used.

[0052] In this invention, samples were periodically taken during the reaction period for Examples 1 and Comparative Examples 1-4. The total As concentration in the liquid phase was determined by hydride generation-atomic fluorescence spectrometry (HG-AFS), and the Fe concentration in the liquid phase was determined by o-phenanthroline spectrophotometry. 2+ The concentration of total Fe was determined by inductively coupled plasma optical emission spectrometry (ICP-OES), and the concentration of microorganisms was monitored by plate counting or hemocytometer method, with simultaneous recording of pH changes in the solution. After the reaction, the solid residue was collected for X-ray diffraction (XRD) and scanning electron microscopy-energy dispersive X-ray spectroscopy (SEM-EDS).

[0053] The characterization results show that in Comparative Example 3, the liquid-phase As leaching rate only began to rise rapidly after 240 h of reaction, indicating a relatively long adaptation period for the microorganisms. The bacterial concentration only began to increase significantly after 190 h; at 190 h, the oxidation rate of arsenopyrite in Comparative Example 3 was only 9.04%. In contrast, in Example 1 (Sch:Apy = 1:1), the bacterial concentration began to rise rapidly after approximately 14 h of reaction and continued to increase throughout the entire reaction cycle, significantly shortening the adaptation period from the conventional 10+ days to 3-5 days. The microbial growth trend in Comparative Example 1 was between that of Example 1 and Comparative Example 3, while the microbial growth in Comparative Example 2 was slow and fluctuated considerably. This may be due to the excessive Schöndorfite introducing a large amount of iron ions, interfering with the ion balance of the system and competing for adsorption sites on the microbial surface. These results demonstrate that the addition of Schöndorfite can effectively shorten the microbial adaptation period and promote early microbial proliferation by rapidly adsorbing liquid-phase arsenic ions and reducing the toxicity of free arsenic to microorganisms. Under a mass ratio of 1:1, the arsenic adsorption capacity provided by Scheres minerals is best matched with the arsenic release rate of arsenopyrite, thus resulting in optimal microbial growth.

[0054] Furthermore, after 190 h of reaction, the oxidation rate of arsenopyrite in Example 1 (1:1) reached 40.58%, significantly higher than the 9.04% in Comparative Example 3. XRD analysis further confirmed that after 20 days of reaction, the characteristic diffraction peaks of arsenopyrite in Example 1 had basically disappeared, while obvious arsenopyrite diffraction peaks remained in Comparative Example 3. It should be noted that, due to the strong arsenic adsorption capacity of Schiele minerals, the degree of mineral oxidation cannot be fully reflected solely by the liquid phase As leaching rate. Some of the arsenic released by oxidation is immediately adsorbed and fixed by Schiele minerals and does not enter the liquid phase. Therefore, the changes in solid phase mineral composition provided by XRD phase analysis are a more reliable means of evaluating the degree of oxidation.

[0055] Furthermore, after 478 h of reaction, the liquid-phase As concentration in Example 1 decreased by 41.58% from its peak value, indicating that the Scheresch mineral not only played a rapid adsorption and capture role for arsenic in the early stage of the reaction, but also converted arsenic into solid-phase ferric arsenate minerals through a dissolution-reprecipitation mechanism in the later stage of the reaction. XRD patterns showed that a large number of amorphous ferric arsenate minerals were generated in Example 1, while a sulfur-rich and iron-rich oxide layer was formed on the surface of the arsenopyrite in Comparative Example 3. SEM-EDS analysis showed that elemental S was mainly distributed in the amorphous oxidation products inside the surface shell of the arsenopyrite, while Fe and As were enriched in the shell region, indicating that the large number of lamellar products observed after 20 days of reaction were secondary iron-arsenic minerals that had detached from the oxide shell of the arsenopyrite surface. This result indicates that the secondary iron-oxygen minerals generated by the oxidation of arsenopyrite mediated by Scheresch minerals did not form a dense passivation layer on the surface of arsenopyrite, but tended to detach, thereby maintaining the continuous reactivity of the arsenopyrite surface.

[0056] Example 2

[0057] This embodiment is exactly the same as Example 1, except that the initial pH of the system is 2.5 and the reaction lasts for 22 days.

[0058] Example 3

[0059] This embodiment is exactly the same as Example 1, except that the initial pH of the system is 2.0 and the reaction lasts for 22 days.

[0060] Comparative Example 5

[0061] This comparative example is exactly the same as Example 1, except that the initial pH of the system is 3.5 and the reaction time is 22 days.

[0062] In addition, for Examples 2, 3 and Comparative Example 5, corresponding control groups without Schiele minerals were set up to periodically sample and monitor the concentrations of As and Fe in the liquid phase and pH. After the reaction, the solid residue was collected for XRD and SEM-EDS characterization.

[0063] Under all pH conditions, the leaching effect of the experimental group with added Schiele minerals was significantly better than that of the corresponding control group without Schiele minerals, and the oxidation effect of arsenopyrite was best at an initial pH of 2.0. Under the initial pH of 2.0, the oxidation rate of arsenopyrite in the experimental group was approximately 1.86 times that of the control group. After 7 days of reaction, the arsenic leaching rate of the experimental group reached 88.77%, while the arsenic leaching rate of the control group only reached its maximum value of 85.64% after 13 days of reaction, indicating that the oxidation initiation was significantly delayed. The effect of the initial pH of the system on the oxidation efficiency can be understood from the following two aspects: Firstly, a lower pH is conducive to the proton-promoted dissolution of arsenopyrite and the Fe... 3+ Stability (inhibition of Fe) 3+ Hydrolysis precipitation), causing Fe3+ / Fe 2+ The oxidizing power of the redox couple is fully utilized; on the other hand, the suitable pH range for the growth of *Acidithiobacillus acidophilus* is approximately 2.0–3.0, with pH 2.0–2.5 being the optimal activity range for this strain, resulting in active microbial metabolism and Fe... 2+ High oxidation rate can maintain a high Fe content. 3+ The replenishment rate, through the synergistic effect of both factors, results in the maximum oxidation rate of arsenopyrite at pH 2.0.

[0064] After 22 days of reaction, the As concentration in the liquid phase of Example 3 decreased by 50.07% from its peak value, while the As concentration in the control group decreased by only 26.34%, indicating that the presence of Schiele minerals significantly enhanced the arsenic fixation effect. SEM-EDS and XRD analyses showed that the oxide layer on the surface of arsenopyrite dissolved rapidly at pH 2.0, and the resulting secondary ferric arsenate minerals were amorphous mineral phases. At higher pH conditions (pH 3.0–3.5), although the arsenic adsorption capacity of Schiele minerals still played a role, the Fe... 3+ Easier to hydrolyze and precipitate, the dissolution-reprecipitation kinetics of Schiele minerals are slowed down, and the oxidation rate of arsenopyrite itself is low, resulting in a decrease in the overall arsenic fixation efficiency.

[0065] Furthermore, in Examples 1-3 of this invention, liquid phase Fe 2+ The concentration remained at extremely low levels (<0.005 g / L), indicating that *Acidithiobacillus acidophilus* maintained high activity and was able to rapidly oxidize arsenopyrite to release Fe. 2+ Oxidized to Fe 3+ Effectively maintained Fe 3+ / Fe 2+ The redox cycle continues. The trend of total Fe concentration first increasing and then decreasing over time is consistent with the arsenic release-fixation kinetics, i.e., in the early stage, the oxidation and dissolution of arsenopyrite dominates, and total Fe continuously increases; in the later stage, mineral precipitation (ferric arsenate, Schiele mineral secondary phase) gradually becomes dominant, and the total Fe concentration decreases. The solution pH first decreases and then tends to stabilize or slightly increase during the reaction, reflecting the dynamic balance between acid production from mineral dissolution and acid consumption from secondary mineral precipitation.

Claims

1. A method for bioleaching and simultaneous arsenic fixation of arsenic-enhanced pyrite from bio-derived Scheres minerals, characterized in that, include: Step S1: Inoculate Acidophilus ferrooxidans into a culture medium containing arsenic pyrite powder for arsenic tolerance acclimatization culture to obtain arsenic tolerance acclimatized bacterial solution; Step S2: Inoculate the arsenic-tolerant acclimatization bacteria solution into ferrous sulfate solution, and after cultivation, filter, wash and dry to obtain bio-derived Scheres mineral; Step S3: Mix the bio-source Scheres ore and the target arsenopyrite at a mass ratio of 0.9~1.1:0.9~1.1, add arsenic-resistant acclimatization bacteria solution to construct a bioleaching system, carry out the bioleaching reaction, and fix arsenic in situ. The initial bacterial concentration in the bioleaching system was 1×10⁻⁶. 7 ~4×10 7 per mL.

2. The method for bioleaching and simultaneous arsenic fixation of bio-derived Scheres mineral-enhanced arsenopyrite according to claim 1, characterized in that: The process of arsenic-resistant acclimatization culture is as follows: Acidophilic ferrooxidizobacterium is inoculated into 9K medium containing arsenic pyrite powder. After the microorganisms enter the logarithmic growth phase, the cells are collected by centrifugation and transferred to a new medium containing arsenic pyrite. This process is repeated 2 to 3 times to obtain the desired arsenic-resistant acclimatization culture.

3. The method for bioleaching and simultaneous arsenic fixation of bio-derived Scheres mineral-enhanced arsenopyrite according to claim 2, characterized in that: The amount of arsenopyrite powder added to the culture medium is 4.5~5.5 g / L; the conditions for arsenic tolerance acclimatization culture are: temperature 25~35℃, shaking speed 150~200 rpm, and culture period 5~7 days.

4. The method for bioleaching and simultaneous arsenic fixation of bio-derived Scheres mineral-enhanced arsenopyrite according to claim 1, characterized in that: The process of obtaining the bio-derived Schiele mineral is as follows: Step S2-1: Wash the arsenic-resistant acclimatization bacteria solution with dilute sulfuric acid (pH 3.0-3.2) to remove residual iron ions, and dilute the bacterial concentration to 1×10⁻⁶. 8 ~4×10 8 cells / mL; Step S2-2: Adjust the pH of the ferrous sulfate solution to be the same as that of the cleaned arsenic-tolerant acclimatization bacterial solution using dilute sulfuric acid, and then proceed with inoculation, cultivation, washing, and drying in sequence to obtain the final product.

5. A method for bioleaching and simultaneous arsenic fixation of bio-derived Scheres mineral-enhanced arsenopyrite according to claim 1 or 4, characterized in that: The concentration of the ferrous sulfate solution is 0.15~0.20 mol / L; the culture conditions are: temperature 25~35℃, shaking speed 150~200 rpm, and culture time 2~4 days.

6. The method for bioleaching and simultaneous arsenic fixation of bio-derived Scheres mineral-enhanced arsenopyrite according to claim 1, characterized in that: The washing process is as follows: the mineral sample is washed 2-3 times with dilute sulfuric acid with pH=3.0~3.2 to remove adsorbed microorganisms and soluble iron.

7. The method for bioleaching and simultaneous arsenic fixation of bio-derived Scheres mineral-enhanced arsenopyrite according to claim 1, characterized in that: The initial pH of the bioleaching system is ≤3.0; the bioleaching reaction time is 20-30 days.

8. A method for bioleaching and simultaneous arsenic fixation of bio-derived Scheres mineral-enhanced arsenopyrite according to claim 1 or 7, characterized in that: The conditions for the bioleaching reaction are as follows: the initial pH of the bioleaching system is 2.0~2.5, the temperature is 25~35℃, and the shaking speed is 150~200rpm.

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