Method for stably solidifying uranium element from source by utilizing mineral membrane formed by mediation of microorganisms

Abstract

The invention provides a method for stably solidifying uranium from the source by forming a mineral membrane through microbial mediation, and belongs to the technical field of heavy metal treatment. According to the method, the acidophilic iron oxidizing microorganisms are used for mediating the additional ferrous source to form the ore film on the surface of the uranium-containing waste, and the ore film comprises one or more of jarosite, goethite, magnetite, gypsum, diaspore or kaolinite, so that migration, release and acid regurgitation phenomena of radioactive metal element uranium in the uranium-containing waste can be effectively inhibited; and the uranium release risk is reduced from the source.

Description

Technical Field

[0001] The invention belongs to the technical field of heavy metal treatment, and in particular relates to a method for stabilizing and solidifying uranium elements from the source by forming a mineral film mediated by microorganisms. Background Art

[0002] Uranium tailings / tailings are wastes discharged after uranium resources are crushed, ground, and useful components are extracted. They are industrial waste slags that are inevitably produced during uranium mining and smelting, and are a long-lived, large-volume, low-radioactive solid waste. The grade of domestic uranium mines is generally low, resulting in a large amount of uranium tailings / tailings, which are mainly stored and disposed of by building reservoirs on the surface. Under the long-term weathering and leaching of these uranium tailings, the radioactive nuclides or heavy metals in them migrate and diffuse, causing pollution to the soil, water, and air; in particular, most of these uranium tailings are acidic, and the acids or acid radicals remaining in the tailings or waste slags accelerate the dissolution of uranium remaining in the ore, seriously polluting the surrounding water and soil environments.

[0003] Existing technology can use microbial reduction and fixation methods to treat uranium-containing wastes, but the crystals of tetravalent uranium compounds after reduction are too small and can be combined with colloids in the water to migrate together; if plant-microorganism combined remediation technology is used, the biggest challenge is that it is difficult to screen hyperaccumulators, which usually grow slowly. There are many factors that affect their remediation efficiency, including soil physical and chemical properties, uranium occurrence forms, added chelating agents, rhizosphere microbial community structure and its activity, etc., and they cannot be stably solidified; if microbial grouting solidification technology is used, it is difficult to penetrate into small pores, so the uranium in the surrounding particles is still in an unstable state, and most of the solidified uranium does not enter the stable mineral lattice, and is easily oxidized and dissolved and gradually migrates, becoming a potential uranium pollution source for the surrounding environment. In summary, the current methods for treating uranium-containing wastes cannot achieve stable solidification, and the uranium is still in an unstable state after treatment, and then pollutes the surrounding environment over time.

[0004] In view of this, it is necessary to design a method that can stabilize and solidify uranium elements from the source to treat uranium-containing waste. Summary of the invention

[0005] The purpose of the present invention is to provide a method for stabilizing and solidifying uranium elements from the source by forming a mineral film mediated by microorganisms. The method provided by the present invention can effectively inhibit the migration and release of radioactive metal elements uranium in uranium-containing waste and the acid regurgitation phenomenon, thereby reducing the risk of uranium release from the source.

[0006] The present invention provides the following technical solutions:

[0007] A method for stabilizing and solidifying uranium elements from the source by forming a mineral film mediated by microorganisms, comprising the following steps:

[0008] Acidophilic iron-oxidizing microorganisms are used to mediate the formation of a mineral film on the surface of uranium-containing waste by adding an external ferrous source.

[0009] Preferably, the acidophilic iron-oxidizing microorganism is one or more of Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, Leptospirillum ferrooxidans and Thermosulfurobacillus sulfoxidans.

[0010] Preferably, the uranium-containing waste includes one or more of uranium tailings, uranium tailings and uranium-containing waste rock.

[0011] Preferably, the added ferrous source is one or more of ferrous sulfate and pyrite.

[0012] Preferably, the method of using acidophilic iron-oxidizing microorganisms to mediate the addition of an external ferrous source to form a mineral film on the surface of uranium-containing waste comprises:

[0013] Crushing and screening the uranium-containing waste to obtain uranium-containing particles or powder;

[0014] Inoculating a bacterial liquid of an acidophilic iron-oxidizing microorganism into a medium containing ferrous iron for culturing to obtain a bacterial liquid;

[0015] inoculating the bacterial solution into an external ferrous source to obtain a passivation solution;

[0016] The uranium-containing particles or powder are passivated by using the passivation liquid to form a mineral film on the surface.

[0017] Preferably, the particle size of the uranium-containing particles or powder is less than 5 mm.

[0018] Preferably, the passivation treatment is carried out in a stirred reactor or a column percolation reactor; the initial pH value of the passivation solution is 1.5 to 5, and the temperature of the passivation treatment is 25° C. to 45° C.

[0019] Preferably, when the passivation treatment is carried out in a stirred reactor, the solid-liquid ratio of the passivation treatment is <15%, and the passivation time is not less than 6 hours; when the passivation treatment is carried out in a column filtration reactor, the solid-liquid ratio of the passivation treatment is <3:1, and the passivation time is not less than 10 days.

[0020] Preferably, the passivation solution also includes added cations;

[0021] The added cations are at least one or more of potassium ions, sodium ions or ammonium ions;

[0022] The ion molar ratio of the added ferrous source to the added cation is 3:0.5 to 3:2.

[0023] The invention also provides a passivation solution, comprising a culture solution of acidophilic iron-oxidizing microorganisms and an external ferrous source.

[0024] Beneficial effects:

[0025] The present invention provides a method for stabilizing and solidifying uranium elements from the source by forming a mineral film mediated by microorganisms. The present invention uses acidophilic iron oxidizing microorganisms to mediate the addition of an external ferrous source to form a mineral film on the surface of uranium-containing waste (the mineral film components include one or more of iron alum, goethite, magnetite, gypsum, diaspore or kaolinite), thereby reducing the diffusion of radioactive elements in uranium-containing waste. The present invention uses acidophilic iron oxidizing microorganisms to convert Fe(II) in uranium-containing waste or Fe(II) in solution into 2+ Oxidation, while releasing Fe 3+ and "metastable" uranium in tailings, while Fe 3+ Hydrolysis precipitation and covering the surface of uranium-containing waste, forming an iron film (Fe2O3 or Fe(OH)3 or goethite); at the same time, the phosphorus source in the ore makes UO2 2+ The uranyl phosphate can form a stable ternary complex with the iron film on the surface of the ore and crystallize and deposit on the surface of the waste. 2+ 、Al 3+ The uranyl phosphate ternary complex formed on the surface of the waste is then wrapped to form a mineral film; further, when the uranium-containing waste is passivated, cations (one or more of potassium ions, sodium ions or ammonium ions) are added, and the remaining Fe 3+ In SO4 2- and K + 、Na + or NH 4+ In the presence of cations such as uranium, a dense iron alum film can be formed to further wrap it, thereby forming a multi-layer stable mineral film, achieving the purpose of solidifying uranium-containing waste and long-term stabilization of the radioactive element uranium therein.

[0026] The method provided by the present invention can effectively inhibit the migration and release of the radioactive metal element uranium in uranium-containing waste and the acid reflux phenomenon, thereby reducing the risk of uranium release from the source; and this method can make up for the shortcomings of existing passivation methods, reduce the use of conventional passivation agents, reduce costs, avoid secondary pollution and eutrophication of water bodies, and has great significance for enriching the theoretical system of uranium mine environmental restoration and promoting the sustainable development of the uranium mining and metallurgy industry. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required to be used in the embodiments are briefly introduced below.

[0028] Figure 1 This is an electron microscope scanning image of a sample with a particle size less than 0.074 mm in Example 1 after biopassivation for 138 hours;

[0029] Figure 2 This is an electron microscope scanning image of the sample with a particle size of 0.074-0.1 mm in Example 1 after biopassivation for 138 hours;

[0030] Figure 3 The leached uranium concentration diagram of samples with different particle sizes after 138 hours of biopassivation;

[0031] Figure 4 The leached uranium concentration diagram obtained after 138h of biopassivation at different initial pH values ​​of the passivation solution;

[0032] Figure 5 The leached uranium concentrations obtained after 138 h of biopassivation at different temperatures;

[0033] Figure 6 The leached uranium concentration diagram obtained after 138h of biopassivation under different solid-liquid ratios (ratio of sample to passivation solution);

[0034] Figure 7 The electron microscope scanning images of the samples obtained after passivation treatment for 138 hours in Example 1 (sample particle size is less than 0.074 mm) and Comparative Example 1, wherein (a) is Comparative Example 1, and (b) is Example 1;

[0035] Figure 8 The pH change diagram and oil leaching diagram obtained from Example 1 (sample particle size is less than 0.074 mm) and Comparative Example 1, wherein (a) represents the acid regurgitation experiment and (b) represents the anti-leaching experiment. DETAILED DESCRIPTION

[0036] The present invention provides a method for stabilizing and solidifying uranium elements from the source by forming a mineral film mediated by microorganisms, comprising the following steps:

[0037] Acidophilic iron-oxidizing microorganisms are used to mediate the formation of a mineral film on the surface of uranium-containing waste by adding an external ferrous source.

[0038] In the present invention, the acidophilic iron-oxidizing microorganism is preferably one or more of Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, Leptospirillum ferrooxidans and Thermosulfurobacillus sulfoxidans.

[0039] The present invention has no particular limitation on the source of the acidophilic iron-oxygen microorganisms. Commercially available acidophilic iron-oxygen microorganisms can be used or the methods well known to those skilled in the art can be used to extract the acidophilic iron-oxygen microorganisms from acidic mine water and soil near coal mines. In a specific embodiment of the present invention, the source of the acidophilic iron-oxygen microorganisms is shown in Table 1.

[0040] Table 1 Sources of acidophilic iron-oxidizing microorganisms

[0041]

[0042] In the present invention, the uranium-containing waste preferably includes one or more of uranium tailings, uranium tailings and uranium-containing waste rocks; the uranium tailings are specifically tailings produced after uranium ore is leached by surface heap leaching or in-situ blasting.

[0043] In the present invention, the added ferrous source is preferably one or more of ferrous sulfate and pyrite.

[0044] In the present invention, the formation of a mineral film on the surface of uranium-containing waste by using acidophilic iron-oxidizing microorganisms to mediate the addition of an external ferrous source preferably includes:

[0045] Crushing and screening the uranium-containing waste to obtain uranium-containing particles or powder;

[0046] Inoculating the bacterial liquid of the acidophilic iron-oxygen microorganism into a medium containing ferrous iron for culturing to obtain a bacterial liquid;

[0047] inoculating the bacterial solution into an external ferrous source to obtain a passivation solution;

[0048] The uranium-containing particles or powder are passivated by using the passivation liquid to form a mineral film on the surface.

[0049] The present invention crushes and screens uranium-containing waste to obtain uranium-containing particles or powders. In the present invention, the particle size of the uranium-containing particles or powders is preferably 5 mm or less, specifically 0.074 mm or less, 0.074-0.1 mm, 2 mm or less, 0.3-0.9 mm, 2-0.9 mm or 2-3 mm.

[0050] The present invention inoculates acidophilic iron oxygen microorganism bacterial liquid into a ferrous iron-containing culture medium for culturing to obtain the bacterial liquid. In the present invention, the culture preferably includes activation culture and expansion culture in sequence; the inoculation amount of the acidophilic iron oxidizing microbial culture liquid in the activation culture is preferably 5-20%, specifically 6%, 10% or 15%; the ferrous content in the ferrous culture medium used in the activation culture is preferably 5-10 g / L, specifically 6 g / L, 8 g / L or 9 g / L; the volume of the culture medium used for the activation culture is preferably 100 mL; the activation culture is preferably carried out in a shaker; the conditions of the activation culture preferably include: an initial pH value of 1.5-3.5, specifically 2.0, 2.5 and 3.0, an initial temperature of 10-40°C, specifically 15°C, 20°C, 25°C, 30°C, 35°C or 40°C, and a shaker speed of 100-200 r / min, specifically 110 r / min, 150 r / min, 170 r / min or 190 r / min. During the activation culture process, it is preferred to count the number of viable cells using a hemocytometer every day. 8 ~10 9After the activation culture is completed, the activated culture solution is preferably inoculated into a ferrous medium for expansion culture, and the volume of the ferrous medium used for the expansion culture is preferably 6L; the inoculation amount and culture conditions of the expansion culture are preferably consistent with those of the activation culture, and are not repeated here; the expansion culture is preferably cultured until the bacterial concentration can reach 10 8 ~10 9 After the expansion culture is completed, the filter residue is preferably removed and the obtained filtrate is the bacterial liquid.

[0051] After obtaining the bacterial solution, the present invention inoculates the bacterial solution into an external ferrous source to obtain a passivation solution. In the present invention, when the external ferrous source is ferrous sulfate, it is preferably used in the form of an external ferrous source solution, and the concentration of ferrous ions in the external ferrous source solution is preferably 5 to 10 g / L, specifically 6 g / L, 8 g / L or 9 g / L; when the external ferrous source is pyrite, it is preferably ground to less than 200 mesh and then directly added to the bacterial solution; the bacterial concentration of the bacterial solution is about 5×10 8 / mL, the inoculation amount of the bacterial solution in the passivation solution is preferably 2% to 5%, specifically 3% or 4%; the passivation solution preferably also includes an added cation; the added cation is preferably one or more of potassium ions, sodium ions or ammonium ions; the ion molar ratio of the added ferrous source to the added cation is preferably 3:0.5 to 3:2, specifically 3:1 or 3:1.5. When the passivation solution includes an added cation, it is preferred to first mix the added ferrous source solution and the added cation, and then inoculate the bacterial solution into the resulting mixed solution.

[0052] After obtaining the passivation solution, the present invention uses the passivation solution to passivate the uranium-containing particles or powder to form a mineral film on the surface. In the present invention, the passivation treatment is preferably carried out in a stirred reactor or a column percolation reactor; the initial pH value of the passivation solution is 1.5 to 5, specifically 2, 3 or 4, and the temperature of the passivation treatment is 25°C to 45°C, specifically 30°C, 35°C or 40°C.

[0053] In the present invention, when the passivation treatment is carried out in a stirred reactor, the solid-liquid ratio of the passivation treatment is <15%, specifically 1%, 5% or 10%; the passivation time is not less than 6 hours, specifically 42 hours, 60 hours, 100 hours or 114 hours; when the passivation treatment is carried out in a column percolation reactor, the solid-liquid ratio of the passivation treatment is <3:1, specifically 2:1, 1:1 or 1:2; the passivation time is not less than 10 days, specifically 30 days, 50 days, 60 days or 80 days.

[0054] The present invention also provides the passivation solution described in the above technical solution, comprising acidophilic iron-oxidizing microorganisms and an external ferrous source.

[0055] The present invention uses acidophilic iron-oxidizing microorganisms to convert Fe(II) in uranium-containing waste or Fe in solution into 2+ Oxidation, while releasing Fe 3+ and "metastable" uranium in tailings, while Fe 3+ Hydrolysis precipitation and covering the surface of uranium-containing waste, forming an iron film (Fe2O3 or Fe(OH)3 or goethite); at the same time, the phosphorus source in the ore makes UO2 2+ The uranyl phosphate can form a stable ternary complex with the iron film on the surface of the ore and crystallize and deposit on the surface of the waste. 2+ 、Al 3+ The uranyl phosphate ternary complex formed on the surface of the waste is then wrapped to form a mineral film; further, when the uranium-containing waste is passivated, cations (one or more of potassium ions, sodium ions or ammonium ions) are added, and the remaining Fe 3+ In SO4 2- With K + 、Na + or NH 4+ In the presence of cations such as uranium, a dense iron alum film can be formed to further wrap it, thereby forming a multi-layer stable mineral film, achieving the purpose of solidifying uranium-containing waste and long-term stabilization of the radioactive element uranium therein.

[0056] In order to further illustrate the present invention, the method for stabilizing and solidifying uranium elements from the source by forming a mineral film mediated by microorganisms provided by the present invention is described in detail below in conjunction with the accompanying drawings and examples, but they should not be understood as limiting the scope of protection of the present invention.

[0057] Example 1

[0058] (1) The heap leaching uranium tailings were crushed and sieved to obtain samples with particle sizes less than 0.074 mm, 0.074-0.1 mm, 0.3-0.9 mm, 2-0.9 mm, and 2-3 mm, respectively.

[0059] (2) A 10% inoculum of Acidithiobacillus ferrooxidans was inoculated into 100 mL of 9K medium for activation culture. The initial pH value was 2.0, the temperature was 30°C, and the shaking speed was 170 r / min. The number of live cells was counted by hemocytometer every day. When the bacterial concentration reached 10 8 / mL, complete the activation culture and remove the filter residue.

[0060] (3) The activated cultured Acidithiobacillus ferrooxidans was inoculated into 6 L of 9K medium containing 9 g / L of ferrous iron at an inoculum size of 10% for expansion culture. The initial pH value was 2, the temperature was 30°C, and the shaking speed was 170 r / min. The number of live cells was counted by the hemocytometer method every day. When the bacterial solution concentration reached 10 8 / mL, complete the expansion culture, remove the filter residue, and obtain the concentrated bacterial liquid.

[0061] (4) Inoculate the Acidithiobacillus ferrooxidans bacterial solution into 150 mL of 44.7 g / L FeSO4·7H2O and K + The concentration of the bacterial solution in the passivation solution was 1×10 8 / mL, sulfuric acid was added to adjust the initial pH of the passivation solution to 2.0, and the treated passivation solution was injected into a stirred reactor filled with 1.5g of sample, and the passivation treatment was carried out for 138h under the conditions of solid-liquid ratio of 1%, shaking table speed of 170r / min and temperature of 30℃.

[0062] Figure 1 This is an electron microscope scanning image obtained after 138 hours of biopassivation of the sample with a particle size less than 0.074 mm in Example 1. It can be seen that there are no corrosion pits on the surface of the slag after 138 hours of biopassivation, and a smooth and dense passivation "protective layer" is formed.

[0063] Figure 2 This is an electron microscope scan obtained after 138 hours of biopassivation of the sample with a particle size of 0.074 to 0.1 mm in Example 1. It can be seen that there are no corrosion pits on the surface of the slag after 138 hours of biopassivation, and a "protective layer" is formed. Red, yellow, green and blue represent the four constituent elements of iron, potassium, oxygen and sulfur, which are the main constituent elements of the mineral film jarosite.

[0064] Figure 3 The following is a graph of uranium leaching concentrations obtained after 138 hours of biopassivation of samples with different particle sizes. The results show that the uranium in powder samples with a particle size of less than 0.074 mm and a particle size of 0.074 to 0.1 mm will be partially leached before 80 hours (the uranium concentration is about 14 mg / L, and the uranium in the solution can be recovered by ion exchange resin adsorption), and no leaching will occur in the following period. In addition, according to Figure 3 It can be seen that when the sample particle size is <0.1 mm, the mineral film wrapping can be completed in 42 hours, and when the sample particle size is 2-3 mm, the mineral film wrapping can be completed in 90 hours, indicating that the method of the present invention can quickly wrap the slag and prevent the radioactive metal from continuing to be leached, which is of great significance for the environmental management and protection of mining areas.

[0065] Example 2

[0066] (1) The heap leaching uranium tailings were crushed and sieved to obtain a sample with a particle size less than 0.074 mm.

[0067] (2) A 10% inoculum of Acidithiobacillus ferrooxidans was inoculated into 100 mL of 9K medium for activation culture. The initial pH value was 2.0, the temperature was 30°C, and the shaking speed was 170 r / min. The number of live cells was counted by hemocytometer every day. When the bacterial concentration reached 10 8 / mL, complete the activation culture and remove the filter residue.

[0068] (3) The activated cultured Acidithiobacillus ferrooxidans was inoculated into 6 L of 9K medium containing 9 g / L of ferrous iron at an inoculum size of 10% for expansion culture. The initial pH value was 2, the temperature was 30°C, and the shaking speed was 170 r / min. The number of live cells was counted by the hemocytometer method every day. When the bacterial solution concentration reached 10 8 / mL, complete the expansion culture, remove the filter residue, and obtain the concentrated bacterial liquid.

[0069] (4) Inoculate the Acidithiobacillus ferrooxidans bacterial solution into 150 mL of 44.7 g / L FeSO4·7H2O and K + The concentration of the bacterial solution in the passivation solution was 1×10 8 / mL, sulfuric acid was added dropwise to adjust the initial pH of the passivation solution to 1.5, 2, 3, 4, 5 and 6, respectively, and the treated passivation solution was injected into a stirred reactor filled with 1.5g of sample, and the passivation treatment was carried out for 138h under the conditions of a solid-liquid ratio of 1%, a shaking table speed of 170r / min and a temperature of 30℃.

[0070] Figure 4 The following is a graph of uranium leaching concentrations obtained after 138 hours of biopassivation at different initial pH values ​​of the passivation solution. The results show that when the initial pH value of the passivation solution is 2, the uranium in the sample is leached to a certain extent, but it reaches a stable point more quickly and there is no leaching in the following period of time. The other groups have an upward trend. This shows that this method can quickly encapsulate slag and prevent radioactive metals from continuing to be leached, which is of great significance for environmental management and protection in mining areas.

[0071] Example 3

[0072] (1) The heap leaching uranium tailings were crushed and sieved to obtain a sample with a particle size less than 0.074 mm.

[0073] (2) A 10% inoculum of Acidithiobacillus ferrooxidans was inoculated into 100 mL of 9K medium for activation culture. The initial pH value was 2.0, the temperature was 30°C, and the shaking speed was 170 r / min. The number of live cells was counted by hemocytometer every day. When the bacterial concentration reached 108 / mL, complete the activation culture and remove the filter residue.

[0074] (3) The activated cultured Acidithiobacillus ferrooxidans was inoculated into 6 L of 9K medium containing 9 g / L of ferrous iron at an inoculum size of 10% for expansion culture. The initial pH value was 2, the temperature was 30°C, and the shaking speed was 170 r / min. The number of live cells was counted by the hemocytometer method every day. When the bacterial solution concentration reached 10 8 / mL, complete the expansion culture, remove the filter residue, and obtain the concentrated bacterial liquid.

[0075] (4) Inoculate the Acidithiobacillus ferrooxidans bacterial solution into 150 mL of 44.7 g / L FeSO4·7H2O and K + The concentration of the bacterial solution in the passivation solution was 1×10 8 / mL, sulfuric acid was added dropwise to adjust the initial pH of the passivation solution to 2, and the treated passivation solution was injected into a stirred reactor filled with 1.5g of sample, and the passivation treatment was carried out for 138h at a solid-liquid ratio of 1%, a shaking table speed of 170r / min, and temperatures of 25℃, 30℃, 35℃, 40℃ and 45℃.

[0076] Figure 5 The following is a graph of uranium leaching concentrations obtained after 138 hours of biopassivation at different temperatures. The results show that when the temperature is 30°C, the slag passivation reaches a stable point faster and there is no leaching in the following period of time, while the other groups have an upward trend. This shows that this method can quickly encapsulate the slag and prevent the radioactive metal from continuing to be leached, which is of great significance for the environmental management and protection of mining areas.

[0077] Example 4

[0078] (1) The heap leaching uranium tailings were crushed and sieved to obtain a sample with a particle size less than 0.074 mm.

[0079] (2) A 10% inoculum of Acidithiobacillus ferrooxidans was inoculated into 100 mL of 9K medium for activation culture. The initial pH value was 2.0, the temperature was 30°C, and the shaking speed was 170 r / min. The number of live cells was counted by hemocytometer every day. When the bacterial concentration reached 10 8 / mL, complete the activation culture and remove the filter residue.

[0080] (3) The activated cultured Acidithiobacillus ferrooxidans was inoculated into 6 L of 9K medium containing 9 g / L of ferrous iron at an inoculum size of 10% for expansion culture. The initial pH value was 2, the temperature was 30°C, and the shaking speed was 170 r / min. The number of live cells was counted by the hemocytometer method every day. When the bacterial solution concentration reached 10 8 / mL, complete the expansion culture, remove the filter residue, and obtain the concentrated bacterial liquid.

[0081] (4) Inoculate the Acidithiobacillus ferrooxidans bacterial solution into 150 mL of 44.7 g / L FeSO4·7H2O and K + The concentration of the bacterial solution in the passivation solution was 1×10 8 / mL, sulfuric acid was added dropwise to adjust the initial pH of the passivation solution to 2, and the treated passivation solution was injected into a stirred reactor filled with 1.5g of sample, and the passivation treatment was carried out for 138h at a solid-liquid ratio of 1%, 5%, 10% and 15%, a shaking table speed of 170r / min, and a temperature of 30℃.

[0082] Figure 6 The following is a graph of uranium leaching concentration obtained after 138 hours of biopassivation at different solid-liquid ratios (ratio of powder sample to passivation solution). The results show that when the solid-liquid ratio is 1% to 5%, part of the uranium in the tailings is leached (the leaching solution is recovered using ion exchange resin), but it reaches a stable point faster and there is no leaching in the following period of time. The other groups have an upward trend. This shows that this method can quickly encapsulate the slag and prevent the radioactive metal from continuing to be leached, which is of great significance for the environmental management and protection of mining areas.

[0083] Comparative Example 1

[0084] (1) The heap leaching uranium tailings were crushed and sieved to obtain a sample with a particle size less than 0.074 mm.

[0085] (2) A 10% inoculum of Acidithiobacillus ferrooxidans was inoculated into 100 mL of 9K medium for activation culture. The initial pH value was 2.0, the temperature was 30°C, and the shaking speed was 170 r / min. The number of live cells was counted by hemocytometer every day. When the bacterial concentration reached 10 8 / mL, complete the activation culture and remove the filter residue.

[0086] (3) The activated cultured Acidithiobacillus ferrooxidans was inoculated into 6 L of 9K medium containing 9 g / L of ferrous iron at an inoculum size of 10% for expansion culture. The initial pH value was 2, the temperature was 30°C, and the shaking speed was 170 r / min. When the bacterial solution concentration reached 10 8 / mL, complete the expansion culture, remove the filter residue, and obtain the concentrated bacterial liquid.

[0087] (4) Add the bacterial solution of Acidithiobacillus ferrooxidans to 150 mL of deionized water. The bacterial solution concentration in the passivation solution is 1×10 8 / mL, sulfuric acid was added dropwise to adjust the initial pH of the solution to 2, and the treated solution was injected into a stirred reactor filled with 1.5g of sample, and the passivation treatment was carried out for 138h at a solid-liquid ratio of 1%, a shaking table speed of 170r / min, and a temperature of 30℃.

[0088] Figure 7 The electron microscope scanning images of the slag obtained after passivation treatment for 138 hours in Example 1 (sample particle size is less than 0.074 mm) and Comparative Example 1, wherein (a) is the slag without adding iron source and not bio-passivated, and (b) is the slag after adding iron source and bio-passivating. Figure 7 It can be seen that the slag without the addition of iron source has not undergone biopassivation and has obvious corrosion pits on the surface. The slag after the addition of iron source and biopassivation has no obvious corrosion pits on the surface and a "protective layer" is formed.

[0089] The passivated samples obtained in Example 1 and Comparative Example 1 were dried, respectively placed in 100 mL of natural water and acidic water with a pH of 2 (prepared by adding sulfuric acid to deionized water), and natural water acid regurgitation and anti-leaching experiments were carried out at a shaking speed of 170 r / min and a temperature of 30°C.

[0090] The results are as follows Figure 8 As shown, (a) represents the acid regurgitation test and (b) represents the anti-leaching test.

[0091] from Figure 8 As can be seen from (a) in the figure, the pH value of the slag after passivation in Example 1 changes stably and is maintained at about 4, while the pH value of the unpassivated slag in Comparative Example 1 continues to drop to about 2.3. Figure 8 As can be seen from (b), after 30 days of anti-leaching test, the maximum uranium leaching amount of the passivated slag in Example 1 does not exceed 0.035 mg / L, and the leaching amount of the unpassivated slag in Comparative Example 1 is 3 mg / L, which is nearly 100 times that of Example 1.

[0092] The above results show that the method provided by the present invention can form a mineral film on the surface of uranium-containing waste (the mineral film components include one or more of iron alum, goethite, magnetite, gypsum, diaspore or kaolinite), effectively inhibit the migration and release of the radioactive metal element uranium in the uranium-containing waste and the acid reflux phenomenon, and reduce the risk of uranium release from the source.

[0093] Although the above embodiment describes the present invention in detail, it is only a part of the embodiments of the present invention, not all of the embodiments. People can also obtain other embodiments based on this embodiment without creativity, and these embodiments all fall within the protection scope of the present invention.

Claims

1. A method for stabilizing and solidifying uranium from the source by forming a mineral film mediated by microorganisms, characterized in that: The following steps are involved: Acidophilic iron-oxidizing microorganisms are used to mediate the formation of a mineral film on the surface of uranium-containing waste by adding an external ferrous source.

2. The method according to claim 1, characterized in that The acidophilic iron-oxidizing microorganism is one or more of Acidithiobacillus ferrooxidans, Leptospirillum ferrooxidans, Leptospirillum ferrooxidans and Thermosulfurobacillus sulfoxidans.

3. The method according to claim 1 or 2, characterized in that: The uranium-containing waste includes one or more of uranium tailings, uranium tailings and uranium-containing waste rocks.

4. The method according to claim 1 or 2, characterized in that: The added ferrous source is one or more of ferrous sulfate and pyrite.

5. The method according to claim 1, characterized in that The method of forming a mineral film on the surface of uranium-containing waste by using acidophilic iron-oxidizing microorganisms to mediate the addition of an external ferrous source comprises: Crushing and screening the uranium-containing waste to obtain uranium-containing particles or powder; Inoculating a bacterial liquid of an acidophilic iron-oxidizing microorganism into a medium containing ferrous iron for culturing to obtain a bacterial liquid; inoculating the bacterial solution into an external ferrous source to obtain a passivation solution; The uranium-containing particles or powder are passivated by using the passivation liquid to form a mineral film on the surface.

6. The method according to claim 5, characterized in that The particle size of the uranium-containing particles or powder is less than 5 mm.

7. The method according to claim 5, characterized in that The passivation treatment is carried out in a stirred reactor or a column diafiltration reactor; The initial pH value of the passivation solution is 1.5-6, and the temperature of the passivation treatment is 25°C-45°C.

8. The method according to claim 7, characterized in that When the passivation treatment is carried out in a stirred reactor, the solid-liquid ratio of the passivation treatment is less than 15%, and the passivation time is not less than 6 hours; When the passivation treatment is carried out in a column filtration reactor, the solid-liquid ratio of the passivation treatment is <3:1, and the passivation time is not less than 10 days.

9. The method according to any one of claims 5 to 8, characterized in that: The passivation solution also includes added cations; The added cations are one or more of potassium ions, sodium ions or ammonium ions; The ion molar ratio of the added ferrous source to the added cation is 3:0.5 to 3:

2.

10. A passivation solution, characterized in that: Includes acidophilic iron-oxidizing microorganisms and an external source of ferrous iron.

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