Green in-situ leaching uranium mining method through sodium persulfate acid process oxidation

Abstract

The invention belongs to the technical field of uranium mining, and particularly relates to a sodium persulfate acid oxidation green in-situ leaching uranium mining method. The method comprises the following steps: (1) exploring and pretreating an ore bed; (2) arranging an injection well and an extraction well; (3) preparing an acidic leaching solution; (4) injecting a leaching solution; (5) in-situ leaching circulation and monitoring; and (6) post-harvest treatment. The novel green acid in-situ leaching uranium mining method is developed, the oxidation rate of tetravalent uranium can be greatly increased, the uranium leaching rate is increased, and compared with an existing acid leaching method, the uranium leaching rate is remarkably increased, and environmental protection is achieved.

Description

Technical Field

[0001] The invention belongs to the technical field of uranium mining, and in particular relates to a green in-situ leaching method for uranium using a sodium persulfate acid oxidation process. Background Art

[0002] With the growing demand for uranium resources and increasingly stringent environmental protection requirements, traditional uranium mining methods such as open-pit and underground mining face numerous challenges, including severe damage to surface vegetation, large waste volumes, and potential groundwater contamination. In-situ uranium leaching (SLS) is gaining attention as a more advanced mining method, primarily for sandstone uranium deposits. The main SLS methods for sandstone uranium deposits include acid leaching, alkaline leaching, and CO2+O2 neutral leaching.

[0003] CN101429860 introduces a desalination and low-reagent leaching method for uranium, which dissolves HCO3 in desalinated water. - The preparation of a leachate containing 250-350 mg / L of O₂ effectively leaches uranium. CN102900418 describes a CO₂+O₂ in-situ uranium leaching method using bicarbonate-type groundwater. However, this in-situ uranium leaching process still has shortcomings in oxidant selection, environmental protection, and leaching optimization.

[0004] CN202411271657.1 discloses a leachate and method for acid leaching of uranium ore: a leachate for acid leaching of uranium ore, the components of the leachate include: an acid compound, an oxidant, a fluorine salt compound and water. The acid compound includes at least one of sulfuric acid, hydrochloric acid or nitric acid. The oxidant includes at least one of hydrogen peroxide, potassium permanganate, sodium persulfate and sodium hypochlorite. The uranium leaching mechanism of the comparative document leachate is mainly as follows: during acid leaching, the oxidant provides a high oxidation potential, oxidizes the tetravalent uranium mineral into hexavalent, and the hexavalent uranium ions are complexed and dissolved with sulfate. However, our experiments found that as the NaF / Na2S2O8 ratio increases, the uranium leaching rate becomes lower, and the addition of fluorine salt compounds (such as sodium fluoride) will reduce the uranium leaching rate of the sodium persulfate system ( Figure 4 ). Summary of the Invention

[0005] The present invention aims to solve the above problems and to provide a green uranium leaching method using sodium persulfate acid oxidation, which can not only efficiently leach uranium but also minimize environmental impact.

[0006] To this end, a first aspect of the present invention provides a method for green in-situ leaching of uranium using a sodium persulfate acid oxidation process. In the method, the acidic leaching solution is:

[0007] 0.05-0.15mol / L sulfuric acid, 0.05-0.2mol / L sodium persulfate.

[0008] In the present invention, the mechanism of uranium oxidation leaching by sodium persulfate acid method is mainly as follows:

[0009] Sulfuric acid provides H during in-situ leaching of uranium. + , the hexavalent uranium ions are complexed with sulfate and dissolved, and sodium persulfate oxidizes tetravalent uranium to hexavalent uranium to enhance the leaching of uranium. The chemical mechanism is shown in chemical reaction formulas (1) to (5);

[0010] UO3+H2SO4→UO2SO4+H2O (1)

[0011] 2UO2+2H2SO4+Na2S2O8→2UO2SO4+2H2O+Na2SO4+SO2 (2)

[0012] SO2+H2O→H2SO3 (3)

[0013] Na2S2O8+2Fe 2+ →2Fe 3+ +Na2SO4+SO4 2- (4)

[0014] 2Fe 3+ +H2SO4+UO2→UO2SO4+2Fe 2+ +2H + (5)

[0015] As a preferred embodiment, the green uranium leaching method using sodium persulfate acid oxidation comprises:

[0016] (1) Use geological exploration methods to survey and pre-process mineral layers;

[0017] (2) Reasonable arrangement of injection wells and extraction wells based on the characteristics of the ore layer;

[0018] (3) preparing acidic leaching solution;

[0019] (4) injecting the leachate into the ore layer while controlling the injection parameters;

[0020] (5) Establish an in-situ leaching cycle and monitor key parameters in real time to adjust the process;

[0021] (6) Extract uranium from the produced fluid and perform post-mining remediation of the ore layer.

[0022] As a further preferred solution, step (1) includes: determining the location, thickness, porosity of the uranium ore layer and the geological and hydrological conditions around the ore layer, performing appropriate pretreatment on the target ore layer, unblocking partially blocked ore layer pores, improving the permeability of the ore layer, and ensuring that subsequent leaching solution can flow smoothly.

[0023] According to the present invention, in a specific embodiment, step (1) includes: using advanced geophysical detection methods, such as high-precision seismic exploration, transient electromagnetic method, etc., to accurately determine the location, thickness, porosity of the uranium ore layer and the geological and hydrological conditions around the ore layer, and appropriately pre-treating the target ore layer. By means of high-pressure water jetting or mild chemical dissolution (such as mild pre-acidification), the operation intensity is controlled to unclog partially blocked ore layer pores, improve the permeability of the ore layer, and ensure that the subsequent leaching solution can flow smoothly, but the operation intensity needs to be controlled to avoid the collapse of the ore layer structure.

[0024] As a further preferred solution, step (2) includes: rationally designing the layout of the injection well and the extraction well based on the characteristics of the ore layer and the principles of fluid mechanics, with the injection well adopting a multi-layer screen structure; the extraction well is arranged at a suitable position downstream of the ore layer fluid and is equipped with a high-efficiency extraction device and a flow control device.

[0025] According to the present invention, in a specific embodiment, step (2) includes: according to the characteristics of the ore layer and the principles of fluid mechanics, the layout of the injection well and the extraction well is reasonably designed, the injection well adopts a multi-layer screen structure, the outer screen has high strength and corrosion resistance to prevent well wall collapse and chemical erosion; the inner screen finely controls the pore size to ensure that the injection fluid is evenly dispersed into the ore layer; the extraction well is arranged at a suitable position downstream of the ore layer fluid, and is equipped with an efficient extraction device that can monitor and control the extraction flow in real time to maintain the pressure balance in the ore layer.

[0026] According to the present invention, in a specific embodiment, step (3) includes: preparing a special acidic leaching solution at a surface liquid distribution station, using sulfuric acid as the base acid, controlling its concentration at 0.05-0.15 mol / L, adding an appropriate amount of sodium persulfate, controlling its concentration at 0.05-0.2 mol / L, and ensuring its complete dissolution and uniform distribution through mixing means such as stirring and ultrasound to avoid excessive acidification of the ore layer due to excessive acidity.

[0027] As a further preferred solution, step (4) comprises: slowly injecting the prepared acidic leaching solution into the ore layer through the injection well, with the initial injection rate preferably controlled at 4-8m 3 / h.

[0028] According to the present invention, in a specific embodiment, step (4) comprises: using a high-pressure pump to slowly inject the prepared acidic leaching solution into the ore layer through the injection well, and the injection rate is dynamically adjusted according to the permeability of the ore layer, and the initial injection rate is controlled at 4-8m 3 / h, and the injection pressure is monitored in real time during the process to prevent excessive pressure from causing formation rupture.

[0029] As a further preferred embodiment, step (5) includes: the acidic leachate undergoes an oxidative leaching reaction with the uranium ore within the ore layer to generate a uranium-containing solution that flows toward the extraction well; key parameters in the extracted solution are monitored in real time by an automated monitoring system; and the acidic leachate formulation and injection rate are adjusted in a timely manner according to changes in uranium concentration. The key parameters include at least one of injection pressure, uranium concentration, and pH.

[0030] In step (5), under normal circumstances, when the uranium concentration is less than 10 mg / L, the concentration and / or injection pressure of sulfuric acid and / or sodium persulfate in the acidic leachate are adjusted to increase the uranium concentration in the leachate. For example, both the concentration of sulfuric acid and sodium persulfate and the injection pressure may be adjusted; alternatively, only the concentration of sulfuric acid and sodium persulfate may be adjusted without adjusting the injection pressure; alternatively, only the concentration of sulfuric acid may be adjusted while also adjusting the injection pressure.

[0031] According to the present invention, in a specific embodiment, step (5) includes: the acidic leaching solution undergoes an oxidation leaching reaction with the uranium ore in the ore layer to generate a uranium-containing solution that flows toward the extraction well, and the key parameters in the extracted solution are monitored in real time by an automated monitoring system, and the acidic leaching solution formula and injection rate are adjusted in a timely manner according to changes in uranium concentration.

[0032] As a further preferred solution, step (6) includes: transporting the extracted uranium-containing solution to a ground processing workshop to extract uranium; and repairing the ore layer after uranium mining.

[0033] According to the present invention, in a specific embodiment, step (6) includes: transporting the extracted uranium-containing solution to a ground processing workshop, extracting uranium using mature processes such as ion exchange and solvent extraction to achieve resource recovery; repairing the ore layer after uranium mining, injecting an appropriate amount of alkaline neutralizing solution (such as calcium hydroxide suspension) into the ore layer to neutralize residual acidic substances and restore the ecological environment of the ore layer to a state close to its original state.

[0034] Compared with the prior art, the present invention has at least the following beneficial effects:

[0035] The present invention develops a new green acid in-situ leaching method for uranium, which can greatly improve the oxidation rate of quadrivalent uranium and thus improve the uranium leaching rate. Compared with the existing acid leaching method, the uranium leaching rate is significantly improved and is environmentally friendly.

[0036] When sodium persulfate is used to leach difficult-to-leach uranium ores using acid oxidation, it oxidizes the insoluble tetravalent uranium in the ore into acid-soluble hexavalent uranium, thereby increasing the uranium leaching rate. Solid sodium persulfate is safe and easy to store, and its elements are all present in the uranium ore itself, without the introduction of other impurities. This makes it more environmentally friendly than commonly used oxidants such as ferric chloride and potassium permanganate.

[0037] The refined post-mining restoration of the ore layer effectively solves environmental problems such as groundwater pollution and ore layer acidification that may be caused by in-situ uranium leaching, ensuring the sustainable use of the ore layer and complying with the concept of green mining development.

[0038] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are specifically listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 It shows the schematic diagram of the "seven-point type" unit pumping layout in the Xinjiang uranium exploration area;

[0040] Figure 2 It shows the schematic diagram of the "five-point" one-unit pumping layout of the Inner Mongolia uranium exploration area;

[0041] Figure 3 It shows the schematic diagram of the "five-point" two-unit pumping layout of the Inner Mongolia uranium exploration area;

[0042] Figure 4 The relationship between the uranium leaching rate and the NaF / Na2SO8 mass ratio is shown. DETAILED DESCRIPTION

[0043] In the following description, a number of specific details are provided to provide a more thorough understanding of the technical solutions provided by the present invention. However, it is obvious to those skilled in the art that the technical solutions provided by the present invention can be implemented without one or more of these details.

[0044] In an embodiment of the present invention, the green in-situ leaching method of uranium using sodium persulfate acid oxidation comprises:

[0045] (1) Use geological exploration methods to survey and pre-process mineral layers;

[0046] Use advanced geophysical detection methods, such as high-precision seismic exploration and transient electromagnetic methods, to accurately determine the location, thickness, porosity of the uranium ore layer and the geological and hydrological conditions around the ore layer, and conduct appropriate pretreatment of the target ore layer. Through high-pressure water jets or mild chemical dissolution (such as mild pre-acidification) and other methods, control the operation intensity, dredge partially blocked ore layer pores, improve the permeability of the ore layer, and ensure that the subsequent leaching solution can flow smoothly. However, the operation intensity needs to be controlled to avoid the collapse of the ore layer structure.

[0047] (2) Reasonable arrangement of injection wells and extraction wells based on the characteristics of the ore layer;

[0048] Based on the characteristics of the ore layer and the principles of fluid mechanics, the layout of the injection wells and extraction wells is rationally designed. The injection well adopts a multi-layer screen structure. The outer screen has high strength and corrosion resistance to prevent well wall collapse and chemical erosion; the inner screen finely controls the pore size to ensure that the injected liquid is evenly dispersed into the ore layer; the extraction well is arranged at a suitable position downstream of the ore layer fluid and is equipped with an efficient extraction device that can monitor and control the extraction flow in real time to maintain the pressure balance in the ore layer.

[0049] (3) preparing acidic leaching solution;

[0050] Prepare special acidic leaching solution at the ground liquid distribution station, use sulfuric acid as the base acid, control its concentration at 0.05-0.15 mol / L, add appropriate amount of sodium persulfate, control its concentration at 0.05-0.2 mol / L, and ensure its complete dissolution and uniform distribution through stirring, ultrasound and other mixing methods to avoid excessive acidification of the ore layer due to local high acidity.

[0051] (4) injecting the leachate into the ore layer while controlling the injection parameters;

[0052] Use a high-pressure pump to slowly inject the prepared acidic leaching solution into the ore layer through the injection well, and the initial injection rate is controlled at 4-8m 3 / h, and the injection pressure is monitored in real time during the process to prevent excessive pressure from causing formation rupture.

[0053] (5) Establish an in-situ leaching cycle and monitor key parameters in real time to adjust the process;

[0054] The acidic leachate undergoes an oxidative leaching reaction with the uranium ore within the ore layer, generating a uranium-containing solution that flows toward the extraction well. An automated monitoring system monitors key parameters in the extracted solution in real time, adjusting the acidic leachate formulation and injection parameters based on changes in uranium concentration. Specifically, when the uranium concentration falls below 10 mg / L, adjustments are made to the sulfuric acid and sodium persulfate concentrations, as well as the injection pressure, to increase the uranium concentration in the leachate and improve the uranium recovery rate. Key parameters include at least one of injection pressure, uranium concentration, and pH.

[0055] (6) Extract uranium from the produced fluid and perform post-mining remediation of the ore layer.

[0056] The extracted uranium-containing solution is transported to the ground processing workshop, where mature processes such as ion exchange and solvent extraction are used to extract uranium to achieve resource recovery; the ore layer after uranium mining is repaired and an appropriate amount of alkaline neutralizing solution (such as calcium hydroxide suspension) is injected into the ore layer to neutralize residual acidic substances and restore the ecological environment of the ore layer to a state close to its original state.

[0057] Wherein, the parts not shown are conventional technical means in this field.

[0058] Example 1:

[0059] In the Xinjiang uranium exploration area, geological exploration has determined that the ore layer is located at a depth of 400-450 meters underground, with an average thickness of 5 meters, an average uranium grade of 0.05%, and a porosity of about 20%. After pre-treating the pores of the ore layer with high-pressure water jets, six injection wells and one extraction well were drilled in a "seven-point" layout ( Figure 1 ). Prepare an acidic leaching solution with a concentration of 0.1 mol / L sulfuric acid and 0.05 mol / L sodium persulfate on the ground, and 3 / h injection rate into the ore layer. Real-time monitoring of the extracted liquid revealed that the uranium concentration increased slowly, so the concentration of sodium persulfate was adjusted to 0.01mol / L and sulfuric acid to 0.15mol / L, and the injection rate was increased to 5m 3 After mining was completed, calcium hydroxide suspension was injected to repair the ore layer. Testing showed that the water quality and soil indicators of the ore layer gradually returned to normal, with an average uranium concentration of 53 mg / L and a uranium leaching rate of 76%.

[0060] Example 2:

[0061] In the Inner Mongolia uranium exploration area, geological exploration has determined that the ore layer is located at a depth of 300-400 meters underground, with an average thickness of 8 meters, an average uranium grade of 0.04%, and a porosity of about 23%. After pre-treating the pores of the ore layer with high-pressure water jets, four injection wells and one extraction well were drilled in a "five-point" layout ( Figure 2 ). Prepare an acidic leaching solution with a concentration of 0.1 mol / L sulfuric acid and 0.05 mol / L sodium persulfate on the ground, and 3 The ore layer was injected at a rate of / h. After the extraction liquid was monitored in real time and the uranium concentration was found to be increasing slowly, the concentration of sodium persulfate was adjusted to 0.075mol / L and sulfuric acid to 0.15mol / L, and the injection rate was increased to 7m 3 After mining was completed, calcium hydroxide suspension was injected to repair the ore layer. Tests showed that the water quality and soil indicators of the ore layer gradually returned to normal, with an average uranium concentration of 37 mg / L and a uranium leaching rate of 85%.

[0062] Example 3:

[0063] In the Inner Mongolia uranium exploration area, geological exploration has determined that the ore layer is located at a depth of 100-200 meters underground, with an average thickness of 10 meters, an average uranium grade of 0.02%, and a porosity of about 27%. After pre-treating the pores of the ore layer with high-pressure water jets, six injection wells and two extraction wells were drilled in a "five-point" layout ( Figure 3 ). Prepare an acidic leaching solution with a sulfuric acid concentration of 0.1 mol / L and a sodium persulfate concentration of 0.05 mol / L on the ground, and 3 The uranium concentration in the extracted liquid was found to be increasing slowly after real-time monitoring. The injection rate was increased to 10m3 / h. 3After mining was completed, calcium hydroxide suspension was injected to repair the ore layer. Testing showed that the water quality and soil indicators of the ore layer gradually returned to normal, with an average uranium concentration of 19 mg / L and a uranium leaching rate of 92%.

[0064] It can be seen from a number of embodiments that the present invention can stably achieve clean and efficient uranium leaching under different geological conditions, and has broad prospects for promotion and application.

[0065] Comparative Example:

[0066] The basic control conditions were the same as those in Example 1, and the concentrations of sulfuric acid and sodium persulfate were the same as those in Example 1. The relationship between the uranium leaching rate and the mass ratio of NaF / Na2S2O8 was investigated.

[0067] That is, the difference from Example 1 is that NaF is additionally added.

[0068] Figure 4 The relationship between the uranium leaching rate and the NaF / Na2S2O8 mass ratio is shown. Figure 4 In the figure, the horizontal axis is the mass ratio of NaF / Na2S2O8 (g / g), ranging from 0.0 to 2.0. The vertical axis is the uranium leaching rate (%), ranging from about 50% to 80%. Figure 4 It can be seen that:

[0069] Initial stage (NaF / Na2S2O8 < 0.5): leaching efficiency is high (about 71% to 76%);

[0070] Transition stage (NaF / Na2S2O8≈0.5~1.0): leaching efficiency decreases significantly (about 66%~71%);

[0071] Stable stage (NaF / Na2S2O8>1.0): the leaching efficiency tends to be flat (about 61% to 66%).

[0072] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention shall be included within the scope of protection of the present invention.

Claims

1. A green uranium leaching method using sodium persulfate acid oxidation, characterized in that: In the sodium persulfate acid oxidation green uranium leaching method, the acidic leaching solution is: 0.05-0.15mol / L sulfuric acid, 0.05-0.2mol / L sodium persulfate.

2. The method for green uranium leaching by sodium persulfate acid oxidation according to claim 1, characterized in that: The initial injection rate of acidic leachate is 4-8m 3 / h.

3. The method for green uranium leaching by sodium persulfate acid oxidation according to claim 1, characterized in that: The green uranium leaching method using sodium persulfate acid oxidation comprises: (1) Use geological exploration methods to survey and pre-process mineral layers; (2) Reasonably arrange injection wells and extraction wells according to the characteristics of the ore layer; (3) preparing acidic leaching solution; (4) injecting the leachate into the ore layer while controlling the injection parameters; (5) Establish an in-situ leaching cycle and monitor key parameters in real time to adjust the process; (6) Extract uranium from the produced fluid and perform post-mining remediation of the ore layer.

4. The method for green uranium leaching using sodium persulfate acid oxidation according to claim 3, wherein: Step (1) includes: Determine the location, thickness, porosity of the uranium ore layer and the geological and hydrological conditions around the ore layer, conduct appropriate pretreatment of the target ore layer, dredge some of the blocked ore layer pores, improve the ore layer permeability, and ensure that the subsequent leaching solution can flow smoothly.

5. The method for green uranium leaching using sodium persulfate acid oxidation according to claim 3, characterized in that: In step (1), the pretreatment is performed by high-pressure water jet or mild pre-acidification.

6. The method for green uranium leaching using sodium persulfate acid oxidation according to claim 3, characterized in that: Step (2) includes: Based on the characteristics of the ore layer and the principles of fluid mechanics, the layout of the injection well and the extraction well is rationally designed. The injection well adopts a multi-layer screen structure; the extraction well is arranged at a suitable position downstream of the ore layer fluid and is equipped with a high-efficiency extraction device and a flow control device.

7. The method for green uranium leaching using sodium persulfate acid oxidation according to claim 3, characterized in that: Step (5) includes: The acidic leaching solution undergoes an oxidation leaching reaction with the uranium ore in the ore layer, generating a uranium-containing solution that flows toward the extraction well. The key parameters in the extracted solution are monitored in real time through an automated monitoring system, and the acidic leaching solution formula and injection rate are adjusted in a timely manner according to changes in uranium concentration.

8. The method for green uranium leaching using sodium persulfate acid oxidation according to claim 7, characterized in that: The key parameters include at least one of injection pressure, uranium concentration, and pH.

9. The method for green uranium leaching using sodium persulfate acid oxidation according to claim 8, characterized in that: When the uranium concentration is lower than 10 mg / L, the concentration of sulfuric acid and / or sodium persulfate in the acidic leaching solution and / or the injection pressure are adjusted to increase the uranium concentration in the leaching solution.

10. The method for green uranium leaching using sodium persulfate acid oxidation according to claim 3, characterized in that: Step (6) includes: The extracted uranium-containing solution is transported to the ground processing workshop to extract uranium; the ore layer after uranium mining is repaired.

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