Method for in-situ leaching mining of sandstone uranium ore

Abstract

The invention discloses a method for in-situ leaching mining of sandstone uranium ore, the concentration of bicarbonate radical ions in ore bed water in the sandstone uranium ore is lower than 0.5 g / L, the sandstone uranium ore comprises yttrium-containing uranium ore, and the carbonate content is 1.5%-2.5%; the ore bed water serves as a solvent, 500 mL of leaching agents with different pH values adjusted through sulfuric acid are prepared, and the concentration of hydrogen peroxide in the leaching agents is 2 g / L; and determining the maximum pH value when the uranium ore in the slice sample is corroded by using the leaching agents with different pH values, and taking the maximum pH value as a critical pH value. The leaching agent with the critical pH value is used for exploiting the sandstone uranium ore, corrosion to gangue minerals in the leaching process can be reduced, the number of formed colloids and CaSO4 precipitates is reduced, the precipitates are prevented from blocking an ore bed, in addition, the method can be used for target corrosion of the refractory uranium ore, and therefore efficient leaching is achieved.

Description

Technical Field

[0001] This invention relates to the field of sandstone uranium mining technology, specifically to a method for in-situ leaching mining of sandstone uranium. Background Technology

[0002] Sandstone uranium deposits are my country's most important natural uranium resources. However, in recent years, sandstone uranium deposits with high carbonate content, where uranium mainly occurs as refractory uranium minerals (including yttrium uranium), and low bicarbonate ion concentration in the ore bed water have encountered difficulties in in-situ leaching using existing carbon dioxide + oxygen leaching processes. This manifests as long leaching times, low leaching rates, and low uranium concentrations in the leachate. Through experimental research, the inventors have concluded that acid leaching exhibits better leaching performance than carbon dioxide + oxygen leaching. However, using existing acid leaching methods—i.e., sulfuric acid + a fixed amount of oxidant, primarily oxygen or hydrogen peroxide—can lead to increased acid consumption and ore bed blockage in ores with high carbonate content.

[0003] Therefore, how to reduce acid consumption and ore layer blockage when using acid leaching to leach the aforementioned sandstone uranium ore has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0004] To address the aforementioned problems, this invention provides a method for in-situ leaching mining of sandstone uranium ore. The sandstone uranium ore contains uranium-bearing minerals with a bicarbonate ion concentration below 0.5 g / L and a carbonate content of 1.5%-2.5%. Using the ore water as a solvent, 500 mL leaching agents with different pH values ​​adjusted by sulfuric acid are prepared, each containing a hydrogen peroxide concentration of 2 g / L. The maximum pH value at which uranium minerals dissolve in thin-section samples is determined using leaching agents with different pH values, and this value is taken as the critical pH value. Mining sandstone uranium ore using a leaching agent with this critical pH value reduces the dissolution of gangue minerals during leaching, decreases the formation of colloids and CaSO4 precipitates, and prevents precipitate blockage of the ore layer. Furthermore, this method can target and dissolve refractory uranium minerals, resulting in highly efficient leaching.

[0005] This application provides a method for in-situ leaching mining of sandstone uranium ore, wherein the concentration of bicarbonate ions in the ore seam water is less than 0.5 g / L; the sandstone uranium ore includes yttrium-bearing uranium and has a carbonate content of 1.5%-2.5%; the method includes:

[0006] The sandstone uranium ore was prepared into thin section samples;

[0007] Using the mineral water as a solvent, 500 mL leaching agents with different pH values ​​adjusted by sulfuric acid were prepared respectively, and the hydrogen peroxide concentration in the leaching agents was 2 g / L;

[0008] Leaching experiments were conducted on the thin-film sample using leaching agents with different pH values ​​to determine the maximum pH value of the leaching agent when uranium minerals in the thin-film sample were dissolved. The maximum pH value of the leaching agent when uranium minerals were dissolved was taken as the critical pH value for uranium mineral dissolution.

[0009] During mining operations, a leaching agent with the aforementioned critical pH value is added to the ore-bearing aquifer for in-situ leaching of sandstone uranium ore to obtain a leachate.

[0010] In surface hydrometallurgical processes, the leachate is treated on the surface using a bicarbonate-type strong base anion exchange resin.

[0011] In some embodiments, the step of conducting leaching experiments on the sheet sample using leaching agents of different pH values ​​includes:

[0012] The thin-film samples were placed in 500 mL leaching agents with different pH values. During the leaching experiment, the leaching agents were stirred using a stirrer. After the experiment, the thin-film samples were taken out from different leaching agents, washed with distilled water, and dried. They were then observed under a scanning electron microscope to determine whether the uranium minerals in the thin-film samples had been dissolved.

[0013] The maximum pH value of the leaching agent when the uranium mineral in the thin-film sample is dissolved is taken as the critical pH value of the uranium mineral.

[0014] In some embodiments, the stirring time is 8 hours.

[0015] In some embodiments, the mixture is stirred for 8 hours using a stirrer, wherein the speed of the stirrer is set to 60-80 r / min.

[0016] In some embodiments, the different pH values ​​include 1, 2, 3, 4, and 5.

[0017] In some embodiments, the critical pH value is 3.

[0018] This invention provides a method for in-situ leaching mining of sandstone uranium ore, wherein the concentration of bicarbonate ions in the ore layer water is less than 0.5 g / L, and the sandstone uranium ore includes yttrium-bearing uranium with a carbonate content of 1.5%-2.5%. Using the ore layer water as a solvent, 500 mL leaching agents with different pH values ​​adjusted by sulfuric acid are prepared, and the hydrogen peroxide concentration in the leaching agents is 2 g / L. The maximum pH value for the dissolution of uranium minerals in thin-section samples is determined using leaching agents with different pH values, and this value is taken as the critical pH value. Using a leaching agent with this critical pH value for mining sandstone uranium ore can reduce the dissolution of gangue minerals during the leaching process, reduce the amount of colloids and CaSO4 precipitates formed, and avoid precipitation clogging the ore layer. Furthermore, this method can target and dissolve refractory uranium minerals, thereby achieving efficient leaching. Attached Figure Description

[0019] Figure 1 An exemplary diagram shows a comparison of the leaching effects of a conventional acid leaching process and a carbon dioxide + oxygen leaching process according to some embodiments;

[0020] Figure 2 An exemplary diagram comparing the leaching effects of sulfuric acid and sodium sulfate according to some embodiments is shown;

[0021] Figure 3 An exemplary flowchart illustrates a method for in-situ leaching mining of sandstone uranium ore according to some embodiments;

[0022] Figure 4 Exemplary before-and-after comparison images of etched sheet samples in three groups of acid leaching experiments at pH 3, 4 and 5, provided according to some embodiments, are shown. Detailed Implementation

[0023] Sandstone uranium deposits are my country's most important natural uranium resources. However, in recent years, sandstone uranium deposits with high carbonate content, where uranium mainly occurs in the form of refractory uranium minerals (including yttrium uranium) and low concentration of bicarbonate ions in the ore water have been found to be difficult to leach using the traditional carbon dioxide + oxygen leaching process. This results in problems such as long leaching time, low leaching rate, and low uranium concentration in the leachate.

[0024] After careful research, the inventors discovered that the aforementioned problems with acid leaching and carbon dioxide + oxygen leaching processes stem primarily from a lack of understanding of the leaching reaction mechanism. For example: 1. Some researchers considered the oxidizing performance of the oxidant a key factor, focusing on enhancing its oxidizing properties by selecting oxidants with stronger oxidizing capabilities, such as sodium thiosulfate, or increasing dissolved oxygen in the ore bed water through nanobubbles. 2. Others focused on developing complexes with high coordination stability constants, attempting to enhance the complexation of uranium from uranium minerals by developing ligands that can form more stable complexes with uranyl, such as some multidentate ligands. However, new reagent types can lead to ore bed water pollution and alterations to hydrometallurgical processes. 3. In in-situ leaching mining of sandstone uranium deposits, the material composition and structure of the ore, as well as the composition of the ore bed water, also significantly influence the selection of the leaching process; existing acid leaching and carbon dioxide + oxygen leaching processes do not consider this factor. Therefore, identifying the key parameters for controlling leaching in traditional acid leaching and carbon dioxide + oxygen leaching processes, and then precisely regulating them to develop refractory deposits, would be an effective approach.

[0025] Through experimental research, the inventors concluded that the acid method has a better leaching effect than the carbon dioxide + oxygen leaching process. However, when using the existing acid method, i.e. sulfuric acid + a fixed amount of oxidant, the oxidant is mainly oxygen or hydrogen peroxide. When facing ores with high carbonate content, it will cause increased acid consumption and cause ore layer blockage.

[0026] Therefore, how to reduce acid consumption and ore layer blockage when using acid leaching to leach the aforementioned sandstone uranium ore has become a technical problem that urgently needs to be solved by those skilled in the art.

[0027] To address the aforementioned technical problems, this application provides a method for in-situ leaching mining of sandstone uranium ore. The sandstone uranium ore contains uranium-bearing minerals, with a bicarbonate ion concentration in the ore bed water below 0.5 g / L and a carbonate content of 1.5%-2.5%. Using the ore bed water as a solvent, 500 mL leaching agents with different pH values ​​adjusted by sulfuric acid are prepared, and the hydrogen peroxide concentration in the leaching agent is 2 g / L. The maximum pH value at which uranium minerals dissolve in thin-section samples is determined using leaching agents with different pH values, and this value is taken as the critical pH value. Using a leaching agent with this critical pH value for mining sandstone uranium ore can reduce the dissolution of gangue minerals during leaching, decrease the amount of colloids and CaSO4 precipitates formed, and prevent precipitates from clogging the ore bed. Furthermore, this method can target and dissolve refractory uranium minerals, thereby achieving efficient leaching.

[0028] Before determining the method for in-situ leaching mining of sandstone uranium ore in the embodiments of this application, the inventors first compared the leaching effects of acid leaching with carbon dioxide + oxygen leaching process.

[0029] The experimental procedure included: preparing a leaching agent of 5 g / L H₂SO₄ + 2 g / L H₂O₂; observing thin-section samples using SEM (scanning electron microscopy) before the experiment (the preparation of thin-section samples is described below) to locate uranium minerals, observe their morphology, and determine their composition. The thin-section samples were placed in 500 ml of the prepared leaching agent (5 g / L H₂SO₄ + 2 g / L H₂O₂), with the mineral-containing side facing upwards. The solution was stirred using a stirrer at a speed generally set to 60-80 r / min to avoid shaking the sample in the aqueous solution. The experiment lasted for two days. Another thin-section sample was placed in a beaker containing 500 ml of mineral-rich water, again with the mineral-containing side facing upwards. The beaker was placed in a high-pressure reactor, and carbon dioxide was first introduced at 0.4 MPa for 4 hours, after which the addition of carbon dioxide was stopped. Then, oxygen at 2 MPa was introduced until the experiment ended, with a test period of one week. During the experiment, the solution was stirred using a stirrer at a speed of 60 r / min. After the experiment, the thin-film samples from both groups were removed from the leaching agent, washed with distilled water, and then air-dried. Finally, the area observed before the leaching experiment was re-examined using a scanning electron microscope to identify the uranium mineral dissolution characteristics, compare the degree of dissolution of uranium minerals under the two leaching conditions, and select the optimal leaching process.

[0030] In one specific embodiment, the Telaobao uranium deposit has a high carbonate content (over 2% wt), with uranium mainly existing in the form of yttrium-bearing uranium, and the bicarbonate concentration in the ore layer water is approximately 0.23 g / L. First, massive ore samples from the Telaobao deposit were prepared into thin sections, which were then observed using a scanning electron microscope (SEM) to locate the uranium minerals, observe their morphology, and determine their composition. The SEM-observed sections were then placed in 500 ml of a solution containing 5 g / L H₂SO₄ + 2 g / L H₂O₂, with the mineral-containing side facing upwards, and leached for 2 days. Simultaneously, another section was placed in a beaker containing 500 ml of ore layer water, again with the mineral side facing upwards. The beaker was placed in a high-pressure reactor, and carbon dioxide was first introduced at 0.4 MPa for 4 hours. After stopping the introduction of carbon dioxide, oxygen was introduced at 2 MPa. The solution was stirred using a stirrer throughout the experiment until the leaching was completed. The entire experimental cycle lasted one week. After the experiment, the thin slices from both groups were removed from the solution, rinsed with distilled water, dried, and then observed again using a scanning electron microscope. Figure 1 As shown, the results indicate that the acid method has a better leaching effect, and the acid method is preferred for leaching this deposit. Therefore, the method in the embodiments of this application is based on the acid method and has been improved and optimized.

[0031] Before determining the method for in-situ leaching mining of sandstone uranium ore in this application embodiment, the inventors prepared a 7.2 g / L sodium sulfate solution (maintaining the same sulfate concentration as the 5 g / L sulfuric acid solution) and a 2 g / L hydrogen peroxide solution. During the experiment, the thin-section sample after SEM observation was placed in 500 ml of the prepared 7.2 g / L Na₂SO₄ + 2 g / L H₂O₂ solution, with the mineral-containing side of the thin-section sample facing upwards. The solution was stirred using a stirrer, with the rotation speed generally set to 60-80 r / min to avoid shaking the thin-section sample in the aqueous solution. The experiment lasted for 2 days. After the experiment, the thin-section sample was removed from the solution, washed with distilled water, and dried. Finally, the area observed before the leaching experiment was re-examined using a scanning electron microscope to identify the area observed before the leaching experiment. The dissolution characteristics of the uranium minerals were analyzed, and the degree of dissolution was compared with that under the leaching conditions of 5 g / L H₂SO₄ + 2 g / L H₂O₂ solution to determine the effectiveness of the hydrogen ion acidolysis.

[0032] In one specific embodiment, the Traaobao uranium deposit was used. Massive ore samples from the Traaobao uranium deposit were prepared into thin sections. The sections, after SEM observation, were placed in 500 ml of a solution containing 7.2 g / L sodium sulfate and 2 g / L hydrogen peroxide, with the mineral-containing side of the section facing upwards. The solution was stirred using a stirrer at a speed of 60-80 rpm to avoid agitation of the section in the aqueous solution. The experiment lasted for two days. After the experiment, the sections were removed from the solution, washed with distilled water, and dried. Finally, the area observed before the leaching experiment was re-examined using a scanning electron microscope to identify and compare the uranium mineral dissolution characteristics, such as… Figure 2 As shown, the results indicate that sodium sulfate solutions with equal sulfate concentrations cannot dissolve uranium minerals, confirming that hydrogen ions have a crucial influence on the dissolution of uranium minerals in this deposit.

[0033] After determining that the acid leaching process is more effective than the carbon dioxide + oxygen leaching process, and that hydrogen ions have a crucial influence on the dissolution of uranium minerals, the inventors continued to study methods for in-situ leaching mining of sandstone uranium deposits. Figure 3 A flowchart of a method for in-situ leaching mining of sandstone uranium ore according to some embodiments is illustrated. The method includes steps S100-S500.

[0034] S100. Prepare the sandstone uranium ore into thin section samples.

[0035] In this embodiment, a leaching process is determined for sandstone uranium ore where the concentration of bicarbonate ions in the ore bed water is below 0.5 g / L, and the sandstone uranium ore includes yttrium-bearing uranium and has a carbonate content of 1.5%-2.5%. Sandstone uranium ore mainly occurs as yttrium-bearing uranium, which is more difficult to leach than pitchblende or crystalline uranium ore.

[0036] In this embodiment of the application, preparing the sandstone uranium ore into a thin-slice sample may include: preparing the massive sandstone uranium ore into a thin-slice sample consisting only of a glass slide.

[0037] To ensure the smooth progress of the experiment, it was first necessary to determine whether uranium minerals were present in the thin-section sample before the experiment was conducted. Specifically, scanning electron microscopy was used to observe the thin-section sample to locate the uranium minerals, observe their morphology, and determine their composition.

[0038] S200. Using the mineral water as a solvent, prepare 500 mL leaching agents with different pH values ​​adjusted by sulfuric acid, wherein the hydrogen peroxide concentration in the leaching agents is 2 g / L.

[0039] In one example, leaching agents with pH values ​​of 1, 2, 3, 4, 5 and 6 and a hydrogen peroxide concentration of 2 g / L were prepared using mineral water as a solvent.

[0040] S300. Using leaching agents with different pH values, leaching experiments are conducted on the thin-film sample to determine the maximum pH value of the leaching agent when the uranium minerals in the thin-film sample are dissolved, and the maximum pH value of the leaching agent when the uranium minerals are dissolved is taken as the critical pH value for uranium mineral dissolution.

[0041] In this embodiment, the uranium mineral is yttrium-bearing uranium stone.

[0042] In some embodiments, the critical pH value is 3.

[0043] In some embodiments, the step of conducting leaching experiments on the sheet sample using leaching agents of different pH values ​​includes:

[0044] The thin-film samples were placed in 500 mL leaching agents with different pH values. During the leaching experiment, the leaching agents were stirred using a stirrer. After the experiment, the thin-film samples were taken out from different leaching agents, washed with distilled water, and dried. They were then observed under a scanning electron microscope to determine whether the uranium minerals in the thin-film samples had been dissolved.

[0045] In some embodiments, the stirring time is 8 hours.

[0046] In this embodiment, the uranium mineral-containing side of the thin-slice sample is placed face up in the leaching agent. The leaching solution is stirred using a stirrer at a speed of 60-80 rpm to avoid agitation of the thin slice in the aqueous solution. The experiment lasts for 8 hours. After the leaching experiment, the thin-slice sample is removed from the leaching solution, washed with distilled water, and dried. Scanning electron microscopy is then used to re-observe the uranium mineral areas observed before the leaching experiment, and to analyze whether the uranium minerals have been dissolved. If the uranium minerals have been dissolved, it indicates that the deposit can be effectively mined under these conditions.

[0047] The maximum pH value of the leaching agent when the uranium mineral in the thin-film sample is dissolved is taken as the critical pH value of the uranium mineral.

[0048] For example, when leaching at pH 3 and hydrogen peroxide concentration of 2 g / L, uranium minerals in thin-film samples are etched. When leaching solutions obtained by mixing sulfuric acid solution and hydrogen peroxide solution at pH 4 and 5 cannot etch the thin-film samples, pH 3 is taken as the critical pH value, which can reduce the amount of sulfuric acid used in subsequent applications.

[0049] S400. During mining, a leaching agent with the critical pH value is added to the ore-bearing aquifer to carry out in-situ leaching mining of sandstone uranium ore, thereby obtaining a leaching solution.

[0050] In this embodiment, mineral water exists in the mineral-bearing aquifer.

[0051] S500. In the hydrometallurgical process on the ground, the leachate is treated on the ground using a bicarbonate-type strong base anion exchange resin.

[0052] The bicarbonate-type strong basic anion exchange resin can be the bicarbonate-type strong basic anion exchange resin produced by Hereger.

[0053] In this embodiment, the sandstone uranium ore is characterized by a high carbonate content (≥1.5%). The addition of sulfuric acid solution will cause the dissolution of carbonate minerals, increasing the calcium ion concentration in the ore layer water. Because sulfuric acid is continuously added during the leaching process, the sulfate concentration in the ore layer water continuously increases, eventually forming calcium sulfate precipitate that blocks the ore layer. Therefore, in this embodiment, a bicarbonate-type strong base anion exchange resin is used for uranyl adsorption. The resin effectively reduces the sulfate concentration while adsorbing uranyl, alleviating the formation of calcium sulfate precipitate. The functional group of the bicarbonate-type strong base anion exchange resin is a quaternary ammonium group (R4N). + Bicarbonate-type strong basic anion exchange resin can be represented as 2R4N. + HCO3 - Uranium typically exists as an ammonium sulfate complex anion, namely [UO2(SO4)2]. 2- UO2 2+ It is a uranyl ion. When a bicarbonate-type strong basic anion exchange resin and [UO2(SO4)2] are used... 2- When the mineral water comes into contact with the ore layer, an ion exchange reaction occurs. 2R⁴N + For negatively charged [UO2(SO4)2] 2- It has a stronger affinity than HCO3. - It has a stronger affinity, thus [UO2(SO4)2] 2-It is adsorbed by bicarbonate-type strong basic anion exchange resin, reducing the sulfate concentration.

[0054] The reaction principle is: 2R 4N + HCO3 - +[UO2(SO4)2] 2- →(R4N + )2·[UO2(SO4)2] 2- +2HCO3 - .

[0055] In one specific embodiment, the Teraobao uranium deposit has a high carbonate content (over 2% wt), with uranium mainly existing in the form of yttrium-bearing uranium, and the bicarbonate concentration in the ore bed water is approximately 0.23 g / L. First, the Teraobao blocky samples were prepared into thin sections for scanning electron microscopy (SEM) observation to locate uranium minerals, observe their morphology, and determine their composition. Sulfuric acid solutions with a hydrogen peroxide concentration of 2 g / L and pH values ​​of 1, 2, 3, 4, and 5 were prepared. During the experiment, the thin sections observed under SEM were placed in beakers containing 500 ml of each pH value, with the mineral-containing side of the section facing upwards. The sulfuric acid + hydrogen peroxide solution was stirred using a stirrer at a speed generally set to 70 rpm to avoid shaking the section in the aqueous solution. The experiment lasted for two days. After the leaching experiment, the sections were removed from the solution, washed with distilled water, and dried. Finally, SEM observation was performed again to locate the areas observed before the leaching experiment and analyze the uranium mineral dissolution characteristics. The observation results are as follows: Figure 4 As shown, Figure 4 The data shows that uranium minerals showed virtually no dissolution at pH values ​​of 4 and 5, indicating that they could not be effectively dissolved under these conditions. However, significant dissolution occurred at pH 3, suggesting that pH is a key parameter controlling leaching in this deposit, and that pH 3 is the threshold (critical pH) for effective leaching. At pH 3, the sulfuric acid concentration was approximately 5 × 10⁻⁶. -4 At this sulfate concentration of mol / L, the calcium ion concentration at calcium sulfate saturation is approximately 0.73 g / L, which is lower than the local calcium ion concentration in the ore bed water. The average porosity of this deposit is approximately 27%, and the average density is approximately 1.88 g / cm³. 3The ore contains approximately 2% wt% calcium carbonate. Therefore, the calcium ion concentration in the ore bed water during calcium carbonate dissolution is approximately 1.39 g / L. Although this value exceeds the saturation calcium ion concentration at pH=3, the conversion of calcium carbonate to calcium sulfate in the ore is limited. Firstly, the amount of calcium sulfate produced is roughly equal to the amount of calcium carbonate dissolved, with a molar ratio of 1:1. Furthermore, calcium sulfate has a higher solubility than calcium carbonate, thus its impact on the permeability of the ore bed is limited. Secondly, under pH=3 conditions, the dissolution of calcite (i.e., calcium carbonate) in the gangue minerals is relatively slow, preventing the formation of large amounts of precipitation within a short time and distance that could cause severe local blockage. Scanning electron microscopy (SEM) images reveal that, except for uranium minerals, other minerals show no signs of dissolution.

[0056] With subsequent well washing and resin leaching, the amount of calcium sulfate precipitated around the well and on the resin will gradually decrease. Under this precise pH-controlled leaching, ore layer blockage can be effectively controlled. Conversely, if the current acid leaching method uses a sulfuric acid concentration of 5 g / L, the calcium ion concentration reaches 7.1 × 10⁻⁶. -3 A calcium ion concentration of g / L will cause precipitation, which can lead to rapid precipitation over short distances and cause irreversible blockage damage to the mineral layer.

[0057] The method in this application utilizes a sulfuric acid solution with a critical pH value to adjust the pH of the ore bed water, combined with an oxidant to achieve leaching. The core of this method lies in the fact that during acid leaching, the sulfuric acid solution not only provides ligands, but more importantly, the acidolysis of hydrogen ions effectively dissolves sparingly soluble uranium ore, promoting uranium leaching. Precise control of the sulfuric acid solution's pH value can effectively reduce calcite dissolution or lower its dissolution rate, thus reducing acid consumption and precipitate formation. Furthermore, the use of a bicarbonate-type strong-base anion exchange resin for uranyl adsorption can reduce the sulfate concentration in the ore bed water, thereby alleviating ore bed blockage.

[0058] This application provides a method for in-situ leaching mining of sandstone uranium ore. The concentration of bicarbonate ions in the ore layer water of the sandstone uranium ore is less than 0.5 g / L. The sandstone uranium ore includes yttrium-bearing uranium and has a carbonate content of 1.5%-2.5%. Using the ore layer water as a solvent, 500 mL leaching agents with different pH values ​​adjusted by sulfuric acid are prepared, and the hydrogen peroxide concentration in the leaching agents is 2 g / L. The maximum pH value for the dissolution of uranium minerals in thin-section samples is determined using leaching agents with different pH values, and this value is taken as the critical pH value. Using leaching agents with this critical pH value to mine sandstone uranium ore can reduce the dissolution of gangue minerals during the leaching process, reduce the amount of colloids and CaSO4 precipitates formed, and avoid precipitation clogging the ore layer. In addition, this method can target and dissolve refractory uranium minerals, thereby achieving efficient leaching.

[0059] It will be readily understood by those skilled in the art that the above-described advantageous methods can be freely combined and superimposed without conflict. The above are merely preferred embodiments of this application and are not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application. The above are merely preferred embodiments of this application. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the technical principles of this application, and these improvements and modifications should also be considered within the protection scope of this application.

Claims

1. A method for in-situ leaching mining of sandstone uranium ore, characterized in that, The concentration of bicarbonate ions in the ore water of the sandstone uranium deposit is less than 0.5 g / L; the sandstone uranium deposit includes yttrium-bearing uranium and has a carbonate content of 1.5%-2.5%; the method includes: The sandstone uranium ore was prepared into thin section samples; Using the mineral water as a solvent, prepare 500 mL leaching agents with different pH values ​​adjusted by sulfuric acid, wherein the hydrogen peroxide concentration in the leaching agent is 2 g / L; Leaching experiments were conducted on the thin-film sample using leaching agents with different pH values ​​to determine the maximum pH value of the leaching agent when uranium minerals in the thin-film sample were dissolved. The maximum pH value of the leaching agent when uranium minerals were dissolved was taken as the critical pH value for uranium mineral dissolution. During mining operations, a leaching agent with the aforementioned critical pH value is added to the ore-bearing aquifer for in-situ leaching of sandstone uranium ore to obtain a leachate. In surface hydrometallurgical processes, the leachate is treated on the surface using a bicarbonate-type strong base anion exchange resin.

2. The method according to claim 1, characterized in that, The steps of conducting leaching experiments on the thin-film samples using leaching agents with different pH values ​​include: The thin-film samples were placed in 500 mL leaching agents with different pH values. During the leaching experiment, the leaching agents were stirred using a stirrer. After the experiment, the thin-film samples were taken out from different leaching agents, washed with distilled water, and dried. They were then observed under a scanning electron microscope to determine whether the uranium minerals in the thin-film samples had been dissolved. The maximum pH value of the leaching agent when the uranium mineral in the thin-film sample is dissolved is taken as the critical pH value of the uranium mineral.

3. The method according to claim 2, characterized in that, The stirring time is 8 hours.

4. The method according to claim 3, characterized in that, Stir for 8 hours using a stirrer, wherein the speed of the stirrer is set to 60-80 r / min.

5. The method according to claim 1, characterized in that, The different pH values ​​include 1, 2, 3, 4 and 5.

6. The method according to claim 1, characterized in that, The critical pH value is 3.

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