In-situ leaching uranium mining underground water restoration reduction barrier test device and test method

Abstract

The invention discloses an in-situ leaching uranium mining groundwater restoration reduction barrier test device and test method, and the device and method can perform simulation reduction on the water flow characteristics and the reduction process of groundwater under the condition of lower cost, and perform related experiments on the basis. A replaceable core pipe column module is innovatively added into the device, simulation sampling analysis can be conveniently carried out on an underground core area, and the problems that a polluted core solid sample is difficult to take in actual in-situ leaching uranium mining activity and an underground core solid sample cannot be directly analyzed in other underground water test devices are solved.

Description

Technical Field

[0001] The present invention is applied to the field of in-situ uranium leaching groundwater remediation and scientific research simulation test, and particularly relates to a reduction barrier test device and a test method for in-situ uranium leaching groundwater remediation. Background Art

[0002] 1. Environmental issues during in-situ leaching of uranium

[0003] In-situ uranium leaching involves injecting a leachate into a uranium ore layer underground, dissolving the uranium ore and then bringing it back to the surface through extraction wells for extraction. However, during the leachate circulation process, uranium, heavy metals, and other radioactive substances can easily diffuse into the groundwater system, causing environmental contamination. In particular, the soluble hexavalent form of uranium (U(VI)) can cause persistent contamination in aquatic environments and pose a threat to biological health. Therefore, effectively remediating groundwater at the end of or during mining operations has become an urgent issue.

[0004] 2. Limitations of existing repair methods

[0005] Traditional groundwater remediation methods include pump-and-treat technology, chemical reduction, and bioremediation. While these technologies can reduce pollutant concentrations to a certain extent, they have the following limitations:

[0006] Extraction-treatment technology: requires large-scale extraction of groundwater, has high operating costs, and has the problem of low remediation efficiency.

[0007] Chemical reduction: By injecting a reducing agent (such as hydrogen sulfide or reduced iron powder) into the ground, the soluble form of uranium is reduced to an insoluble form. However, the diffusion and reaction of the reducing agent underground are difficult to precisely control and can easily cause secondary contamination of the underground environment.

[0008] Bioremediation: Although uranium reduction can be achieved through microbial metabolism, bioremediation takes a long time, and the environmental conditions in groundwater (such as redox potential and pH value) are difficult to control.

[0009] Therefore, the application effect of existing technologies in groundwater remediation is limited, and there is an urgent need to develop an efficient and low-cost remediation method and device.

[0010] 3. Introduction of barrier reduction technology

[0011] Reduction barrier technology is an innovative groundwater remediation method. It aims to establish a permeable reduction barrier, allowing contaminated groundwater to undergo chemical reduction reactions as it flows through the barrier, degrading or removing harmful pollutants and forming copolymer precipitation, which reduces the porosity of the subsurface rock and soil and the diffusion rate of various contaminating heavy metal ions. For uranium-contaminated groundwater, the core of the reduction barrier is to use permeable materials (such as zero-valent iron, sulfide, activated carbon, etc.) to reduce hexavalent uranium ions (U(VI)) to tetravalent uranium (U(IV)), thereby precipitating and retaining the uranium within the barrier, preventing further migration.

[0012] 4. Experimental device design and function

[0013] To verify the effectiveness of the reduction barrier in actual scenarios, a test device for the remediation of groundwater from in-situ uranium leaching was developed. This device is used for small-scale testing and simulates actual underground environments. The technical background of the device mainly includes the following aspects:

[0014] Selection of permeable rock sand materials: Depending on the target pollutants (such as uranium, heavy metals, etc.), different reducing agents or materials are selected to ensure that they can fully react when groundwater flows through the barrier.

[0015] Structural design: The test device typically includes an underground injection well, an extraction well, a reduction barrier, and a monitoring system. The structural design should consider the groundwater flow rate, direction, and quality to ensure the effectiveness of the reduction barrier.

[0016] On-site monitoring and feedback control: By installing test monitoring wells, the concentration of pollutants in groundwater and its changes are measured in real time, and the amount and frequency of reducing agent injection are adjusted to ensure the stable operation of the system.

[0017] The existing reduction barrier test device still has the following shortcomings that need to be improved:

[0018] (1) The existing reduction barrier test equipment cannot perform sampling and analysis on core samples, and the simulation analysis effect is weak;

[0019] (2) The existing reduction barrier test equipment is not flexible enough to install and operate. It is difficult to operate when deploying different scales and types of polluted areas, and it is difficult to quickly adjust to different conditions during the experimental stage.

[0020] Based on the above problems, the inventors have conducted in-depth research on a test device and a test method for the remediation of groundwater reduction barriers in in-situ uranium leaching, in the hope of designing a test device and a test method for the remediation of groundwater reduction barriers in in-situ uranium leaching that can solve the above problems. Summary of the Invention

[0021] In order to overcome the above problems, the inventors conducted intensive research and designed a test device and test method for groundwater remediation and reduction barrier in in situ uranium leaching. The device and method can simulate the water flow characteristics and reduction process of groundwater at a relatively low cost, and conduct relevant experiments on this basis. The device innovatively adds a replaceable core string module to facilitate simulated sampling and analysis of underground core areas, solving the problems of difficulty in obtaining contaminated core solid samples in actual in situ uranium leaching activities and the inability to directly analyze underground core solid samples in other groundwater test devices, thereby completing the present invention.

[0022] Specifically, the present invention provides a test device for remediation of groundwater reduction barriers in in-situ leaching of uranium, the device comprising:

[0023] A bottom plate 1 and a baffle plate 2 surrounding the bottom plate 1, wherein a plurality of pipe units 3 are vertically arranged on the bottom plate 1.

[0024] A receiving space is formed by the bottom plate 1 and the baffle plate 2 to receive ore, sand, soil and water simulating the ground environment; the plurality of pipe units 3 are distributed in a ring shape in the receiving space;

[0025] The pipe unit 3 includes an inner pipe 31 located in the middle and a plurality of outer pipes 32 surrounding the inner pipe 31 and abutting against each other. An inner pipe opening area 311 is provided on the side wall of the lower end of the inner pipe 31; an outer pipe opening area 321 is provided on the side wall of the lower end of each outer pipe 32. A plurality of through holes are densely formed in the inner pipe opening area 311 and the outer pipe opening area 321.

[0026] The inner tube 31 controls the inflow and outflow of water in the containing space, and the outer tube 32 is filled with ore or sand, and the ore or sand in the outer tube 32 can be pumped out upward, thereby simulating the extraction of underground solid samples by pumping out the ore or sand in the outer tube 32 upward.

[0027] The outer dimensions of the plurality of outer tubes 32 are consistent. When the plurality of outer tubes 32 and the inner tube 31 are assembled into the pipeline unit 3 , the height positions of the inner tube opening area 311 and the outer tube opening area 321 are consistent.

[0028] The inner tube opening area 311 is cylindrical and surrounds the inner tube 31.

[0029] The outer tube opening area 321 is cylindrical and surrounds the outer tube 32;

[0030] Among them, the flow path of water in the test device is: water enters from the end of the inner tube 31, passes through the inner tube opening area 311 and the outer tube opening area 321, enters the outer tube 32, and then enters the containing space outside the pipeline unit 3 through the outer tube opening area 321. After reaching another pipeline unit 3, it reverses the above flow path and is discharged from the inner tube 31 of the pipeline unit.

[0031] In the pipeline unit 3 , one end of each outer tube 32 abuts against the bottom plate 1 , and a detachable sealing end cover is provided on the other end. The outer tube 32 is sealed at both ends by the bottom plate 1 and the sealing end cover.

[0032] A plurality of through holes are provided on the bottom plate 1 , the number of the through holes being the same as the number of the pipe units 3 and the inner tubes 31 , and the bottom end of each inner tube 31 abuts against the through hole;

[0033] Removable sealing end covers are provided at the top end of the inner tube 31 and the bottom end of the through hole, so that water can flow in and out through the top or bottom of the inner tube 31 .

[0034] The multiple outer tubes 32 that abut against each other together surround and form a water flow space for accommodating the inner tube 31.

[0035] The pipeline unit 3 also includes a sealing cover 33 installed on the inner side of multiple outer tubes 32. A through hole is opened in the middle of the sealing cover 33 for the inner tube 31 to pass through. The sealing cover 33 and the bottom plate 1 jointly seal the water flow space at the upper and lower ends.

[0036] Wherein, in the receiving space, the plurality of pipe units 3 are arranged to form at least four layers of nested ring structures;

[0037] In the four-layer ring structure, a group of pipe units 3 located in the center is the first-layer ring structure, 3-5 groups of pipe units 3 on the periphery thereof constitute the second-layer ring structure, 6-10 groups of pipe units 3 on the periphery of the second-layer ring structure constitute the third-layer ring structure, and 10-14 groups of pipe units 3 on the periphery of the third-layer ring structure constitute the fourth-layer ring structure.

[0038] The present invention also provides a method for testing the reduction barrier of groundwater for in-situ uranium leaching, which is implemented by the above-mentioned device for testing the reduction barrier of groundwater for in-situ uranium leaching.

[0039] The method comprises the following steps:

[0040] Step 1: Prepare ore / sand soaked in contaminated water according to the type and quantity of rock and sand to be simulated;

[0041] Step 2, sample loading, i.e., filling the inner circle of the holding space with ore / sand soaked in contaminated water and ore / sand soaked in uncontaminated water, and filling the outer circle of the holding space with ore / sand soaked in uncontaminated water; filling clay above the inner and outer circles to simulate the surface soil layer and seal; preferably, the inner circle covers the third layer of the annular structure formed by the pipe unit 3; the outer circle covers the fourth layer of the annular structure formed by the pipe unit 3;

[0042] Step 3, uniformly contaminated water; that is, injecting contaminated water from the inner tube 31 of the first layer of the annular structure, and opening the partially sealed end cap on the inner tube 31 of the third layer of the annular structure;

[0043] Step 4: injecting a reducing agent to form a reduction barrier; that is, injecting the reducing agent from the inner tube 31 of the second ring structure, and opening the sealed end cap of each inner tube 31 in the third ring structure; preferably, taking a water sample to determine the injection status of the reducing agent;

[0044] Step 5, determine the effect of the reduction barrier; that is, inject contaminated water from the inner tube 31 of the first-layer annular structure, and open the partially sealed end cover on the inner tube 31 of the fourth-layer annular structure; preferably, extract water samples and solid samples at different positions on the contaminated water flow path according to a predetermined frequency to obtain the effect of the original barrier.

[0045] The beneficial effects of the present invention include:

[0046] (1) The in-situ uranium leaching groundwater remediation reduction barrier test device and test method provided by the present invention innovatively adds a replaceable core string module, which facilitates simulated sampling and analysis of the underground core area, solving the problem that it is difficult to obtain contaminated core solid samples in actual in-situ uranium leaching activities and that other groundwater test devices cannot directly analyze underground core solid samples. Traditional test devices and test methods cannot directly mine ore but use chemical reagents for leaching, which naturally makes it difficult to obtain contaminated core samples on site.

[0047] (2) The in situ leaching uranium groundwater remediation reduction barrier test device and test method provided by the present invention adopt a modular design, the device can be flexibly assembled, and is applicable to contaminated areas of different sizes, facilitating rapid adjustment of various conditions during the experimental stage;

[0048] (3) The test device and test method for groundwater remediation of uranium in situ leaching provided by the present invention can realize automatic control and dynamically adjust the injection speed and amount of the reducing agent according to the monitoring data, thereby avoiding the uncertainty in manual operation.

[0049] (4) The reduction barrier test device and test method for groundwater remediation in in situ uranium leaching provided by the present invention have broad application prospects, particularly in the mining, nuclear, and chemical industries. Its core advantages lie in its low cost, high efficiency, and strong sustainability. As the demand for groundwater remediation increases, this device may become one of the important technologies in the field of pollution control, providing a reliable solution for groundwater remediation in future in situ uranium leaching areas. BRIEF DESCRIPTION OF THE DRAWINGS

[0050] Figure 1 This is a schematic diagram of the overall structure of the groundwater remediation reduction barrier test device for in-situ leaching uranium provided by the present invention;

[0051] Figure 2 A top view of the test device for remediation of groundwater reduction barriers for in-situ leaching of uranium provided by the present invention;

[0052] Figure 3 A side view of the test device for remediation of groundwater reduction barriers for in-situ leaching of uranium provided by the present invention;

[0053] Figure 4 This is a schematic structural diagram of a pipeline unit in the groundwater remediation reduction barrier test device for in-situ uranium leaching provided by the present invention;

[0054] Figure 5 A schematic diagram showing the flow path of contaminated water in step 3 of an embodiment of the present invention is shown;

[0055] Figure 6 Schematic diagram showing the formation position of the reduction barrier in step 4 of an embodiment of the present invention;

[0056] Figure 7 A schematic diagram showing the locations of the sampling points in step 5 of the embodiment of the present invention is shown;

[0057] Figure 8 A schematic diagram showing the pH variation of the chemical reduction barrier in an embodiment of the present invention is shown;

[0058] Figure 9 A schematic diagram showing the variation of the chemical reduction barrier Eh in an embodiment of the present invention is shown;

[0059] Figure 10 A schematic diagram of pH prediction of the effectiveness of the chemical reduction barrier in an embodiment of the present invention is shown.

[0060] Description of Reference Numerals

[0061] 1- bottom plate, 2- baffle plate, 3- pipe unit, 31- inner pipe, 311- inner pipe opening area, 32- outer pipe, 321- outer pipe opening area, 33- sealing cover, DETAILED DESCRIPTION

[0062] The present invention will be described in further detail below with reference to the accompanying drawings and examples, through which the features and advantages of the present invention will become more clearly understood.

[0063] The word "exemplary" is used exclusively herein to mean "serving as an example, example, or illustration." Any embodiment described herein as "exemplary" is not necessarily to be construed as preferred or advantageous over other embodiments. Although various aspects of the embodiments are shown in the drawings, the drawings are not necessarily drawn to scale unless otherwise indicated.

[0064] The present invention provides a test device for the restoration of groundwater reduction barriers in uranium in situ leaching. Figure 1 、 Figure 2 、 Figure 3 and Figure 4 As shown in , the device includes:

[0065] A base plate 1 and a baffle plate 2 surrounding the base plate 1, multiple groups of pipe units 3 are vertically arranged on the base plate 1, the base plate is preferably a circular plate, and the base plate 1 and the baffle plate 2 are preferably transparent organic glass plates; the height of the pipe unit is slightly higher than the height of the baffle plate 2, so that when the device is filled with ore sand, the outer pipe or inner pipe in the pipe unit can still be easily taken out.

[0066] A receiving space is formed by the bottom plate 1 and the baffle plate 2 to receive ore, sand, soil and water simulating the ground environment; the plurality of pipe units 3 are distributed in a ring shape in the receiving space;

[0067] The pipeline unit 3 includes an inner tube 31 located in the middle and a plurality of outer tubes 32 surrounding the outside of the inner tube 31 and abutting against each other. An inner tube opening area 311 is provided on the side wall of the lower end of the inner tube 31; an outer tube opening area 321 is provided on the side wall of the lower end of each outer tube 32, and a plurality of through holes are densely opened on the inner tube opening area 311 and the outer tube opening area 321; the number of the through holes is large, and 150-200 holes can be arranged on the opening area of ​​a tube, and the hole diameter is small to ensure that water can pass through.

[0068] The inner tube 31 is used to control the inflow and outflow of water in the containing space, and the outer tube 32 is filled with ore or sand, and the ore or sand in the outer tube 32 can be drawn out upward, thereby simulating the extraction of underground solid samples by drawing out the ore or sand in the outer tube 32 upward. The type of ore and sand in the outer tube can also be replaced by drawing out the outer tube 32 and replacing it, so as to simulate geological environments under different conditions.

[0069] Preferably, in order to facilitate the upward extraction of the ore or sand in the outer tube 32, the outer tube 32 is constructed as a double-layer structure in this application. Specifically, the outer tube 32 comprises a base tube and a movable tube nested within the base tube. The base tube is embedded and fixed in the receiving space. The outer diameter of the movable tube is substantially the same as the inner diameter of the base tube, and the movable tube can slide up and down within the base tube. The ore or sand filled in the outer tube 32 is actually filled in the movable tube, allowing it to be extracted upward relative to the base tube along with the movable tube. The base tube and the movable tube are both provided with through-holes in the opening area 321 of the outer tube 32, and are interconnected. The movable tube is slightly longer than the base tube to facilitate extraction of the movable tube. When the movable tube is not being extracted, the movable tube and the base tube can be considered as one tube, namely, the outer tube.

[0070] In a preferred embodiment, the outer dimensions of the plurality of outer tubes 32 are consistent. When the plurality of outer tubes 32 and the inner tube 31 are assembled into the pipeline unit 3, the height positions of the inner tube opening area 311 and the outer tube opening area 321 are consistent, that is, the opening areas are adjacent to each other.

[0071] Preferably, the inner tube opening area 311 is cylindrical and surrounds the inner tube 31, and the outer tube opening area 321 is cylindrical and surrounds the outer tube 32;

[0072] By setting up the opening area, the flow path of water in the test device is as follows: water enters from the end of the inner tube 31, passes through the inner tube opening area 311 and the outer tube opening area 321, enters the outer tube 32, and then enters the containing space outside the pipeline unit 3 through the outer tube opening area 321. After reaching another pipeline unit 3, it reverses the above flow path and is discharged from the inner tube 31 of the pipeline unit; specifically, the reversal is: water enters the outer tube opening area 321 of the outer tube 32 into the outer tube 32, and then passes through the outer tube opening area 321 and the inner tube opening area 311 into the inner tube 31, and finally is discharged from the inner tube 31 to the outside of the containing space.

[0073] In a preferred embodiment, in the pipeline unit 3, one end of each outer tube 32 abuts against the base plate 1, and a detachable sealing end cover is provided on the other end. The outer tube 32 is sealed at the upper and lower ends by the base plate 1 and the sealing end cover. The outer tube 32 is filled with soaked mineral sand. After sealing the outer tube 32, it can ensure that the water therein is not easy to flow, achieving an effect similar to stabilizing groundwater, and the sealing end cover can be removed. After removal, it can form a communicating vessel with the transparent inner tubes in other pipeline units, so that the water in the containing space flows along the communicating vessel, achieving an effect similar to flowing groundwater.

[0074] In a preferred embodiment, a plurality of through holes are formed on the bottom plate 1, the number of the through holes being the same as the number of the pipe units 3 and the inner tubes 31, and the bottom end of each inner tube 31 abuts against the through hole; the through holes on the bottom plate 1 allow both the upper and lower ends of the inner tube 31 to be transparent, allowing water to flow in and out of both ends;

[0075] Removable sealing end caps are provided at the top end of the inner tube 31 and the bottom end of the through hole, so that water can flow in and out through the top or bottom of the inner tube 31, or both can be sealed to prevent water from flowing.

[0076] In a preferred embodiment, the plurality of outer tubes 32 abutting against each other together surround and form a water passage space for accommodating the inner tube 31.

[0077] The piping unit 3 also includes a sealing cover 33 mounted inside the plurality of outer tubes 32. A through-hole is defined in the center of the sealing cover 33 for the inner tubes 31 to pass through. The sealing cover 33 and the bottom plate 1 together seal the water flow space at both ends. Only after the water flow space is sealed can water flow back and forth between the inner tubes 31 and the outer tubes 32. Furthermore, the sealing cover 33 can also be used to assist in securing the outer tubes 32, providing a position limit for extraction and placement of the outer tubes 32.

[0078] In a preferred embodiment, in the receiving space, the plurality of pipe units 3 are arranged to form at least four layers of nested ring structures;

[0079] In the four-layer ring structure, the group of pipe units 3 located in the center is the first ring structure, the 3-5 groups of pipe units 3 on the periphery of the first ring structure constitute the second ring structure, the 6-10 groups of pipe units 3 on the periphery of the second ring structure constitute the third ring structure, and the 10-14 groups of pipe units 3 on the periphery of the third ring structure constitute the fourth ring structure. When more pipe units are provided, a fifth or even sixth ring structure can be added accordingly; preferably, as Figure 1 、 Figure 2 and Figure 3 As shown in , the second-layer ring structure includes 4 groups of pipeline units, the third-layer ring structure includes 8 groups of pipeline units, and the fourth-layer ring structure includes 12 groups of pipeline units. Figure 2 The dotted line portion in FIG shows an example of the specific location of the four-layer ring structure.

[0080] The present invention also provides a method for testing the remediation of groundwater reduction barriers in uranium in situ leaching, which is implemented using the aforementioned uranium in situ leaching groundwater remediation and reduction barrier testing apparatus. The method comprises the following steps:

[0081] Step 1: Prepare ore / sand soaked in contaminated water according to the type and quantity of rock and sand to be simulated;

[0082] Step 2: Sample loading. This involves filling the inner ring of the containment space with ore / sand soaked in contaminated water and ore / sand soaked in uncontaminated water, and the outer ring with ore / sand soaked in uncontaminated water. Clay is then placed above the inner and outer rings to simulate surface soil and seal the space. This clay can also simulate surface runoff to study the impact of surface runoff on groundwater contamination and remediation.

[0083] Preferably, the inner ring covers the third layer of the annular structure formed by the pipe units 3; the outer ring covers the fourth layer of the annular structure formed by the pipe units 3; more preferably, a temporary cylindrical baffle is placed in the receiving space, the inner side of which is the inner ring and the outer side is the outer ring, and after the inner ring and the outer ring are respectively filled with ore sand, the cylindrical baffle is removed;

[0084] Due to the installation of multiple sets of pipe units, the device can simulate the flow of groundwater under different water level conditions, including the water flow velocity in the horizontal and vertical directions; because the outer tube can be filled with mineral sand, the device can also simulate the flow path of groundwater under different geological conditions, including the permeability of various soils and rocks.

[0085] Step 3, uniformly contaminate the water; that is, inject contaminated water from the inner tube 31 of the first-layer annular structure, and open the partially sealed end cover on the inner tube 31 of the third-layer annular structure; make the contaminated water flow from the first-layer annular structure toward the third-layer annular structure, simulating the flow process of contaminated water; thereby being able to accurately control the injection concentration and rate of different pollutants to simulate the situation of the actual pollution source; being able to simulate different types of pollutants, such as heavy metals, organic matter, etc.; and also being able to simulate the transmission and diffusion process of different pollutants in groundwater.

[0086] Step 4: Injecting a reducing agent to form a reduction barrier; that is, injecting the reducing agent from the inner tube 31 of the second ring structure, and opening the sealed end cap of each inner tube 31 in the third ring structure; preferably, taking a water sample to determine the injection status of the reducing agent; in this process, by controlling the water injection speed of the inner tube 31, the concentration and rate of the reducing agent injection can be precisely controlled;

[0087] Step 5, determine the effect of the reduction barrier; that is, inject contaminated water from the inner tube 31 of the first-layer annular structure, and open the partially sealed end cover on the inner tube 31 of the fourth-layer annular structure; preferably, extract water samples and solid samples at different positions on the contaminated water flow path at a predetermined frequency to obtain the effect of the original barrier, so as to simulate various groundwater remediation technologies, such as biological remediation and chemical remediation processes and monitor them; be able to monitor the changes in pollutant concentration in groundwater during the remediation process and evaluate the remediation effect.

[0088] Through sampling, the concentration changes of various pollutants in groundwater can be monitored in real time. Sampling devices are provided to collect groundwater samples at different times and locations for subsequent analysis. Furthermore, the groundwater remediation process can be debugged and optimized based on the experimental results.

[0089] Example

[0090] Use Figure 1 、 Figure 2 and Figure 3 A method for remediating reduction barrier of groundwater for in-situ leaching uranium is carried out using a test device for remediating reduction barrier of groundwater for in-situ leaching uranium, the method comprising the following steps:

[0091] Step 1: Prepare ore / sand soaked in contaminated water according to the type and quantity of rock and sand to be simulated;

[0092] Step 2: Place a cylindrical baffle in the holding space. The area enclosed by the cylindrical baffle is the inner circle, which covers the third ring structure composed of the pipe unit. Fill the interior of the cylindrical baffle with a 25 cm high ore / sand soaked in contaminated water, specifically, a 5 cm high ore layer weighing about 42 kg. A 0.5 cm high layer of 120-160 mesh sand weighing about 9 kg is laid above and below the ore layer. A 1 cm high layer of 80-120 mesh sand weighing about 18 kg is laid on both sides of the 120-160 mesh sand layer. A 6 cm high layer of 40-80 mesh sand weighing about 45 kg is laid on both sides of the 80-120 mesh sand layer. A 6 cm high layer of 26-40 mesh sand weighing about 109 kg is laid on both sides of the 40-80 mesh sand layer. A 25 cm high layer of 26-40 mesh sand weighing about 208 kg soaked in uncontaminated water is filled above the ore / sand soaked in contaminated water.

[0093] The area outside the cylindrical baffle is the outer ring, which is filled with a 50 cm high, 785 kg 26-40 mesh sand layer soaked in uncontaminated water;

[0094] Fill the inner and outer circles with 10cm of red clay weighing approximately 425kg to simulate the surface soil layer and seal it;

[0095] Step 3: Inject contaminated water from the inner tube of the first ring structure, and open the sealed end caps of the four inner tubes on the third ring structure, and these four inner tubes are not adjacent to each other; inject 50L of contaminated water, control the flow rate at 3.47ml / min, and achieve uniform saturation in about 10 days; the flow path of the contaminated water is as follows: Figure 5 As shown in;

[0096] Step 4: Inject the reducing agent from the inner tube of the second ring structure, open the sealed end cap of each inner tube in the third ring structure, and take water samples from the inner tube of the third ring structure for analysis and testing. A total of 100L of reducing agent is required. The injection rate of a single inner tube is about 1ml / min, and a total of 20 days are required. The location of the reduction barrier is as follows: Figure 6 As shown in;

[0097] Step 5: Inject contaminated water into the inner tubes of the first annular structure, and open the sealed end caps of the four inner tubes of the fourth annular structure, with the four inner tubes separated by two sets of pipe units. The contaminated water is injected into the inner tubes at a flow rate of 3.5-5 ml / min for a total of 77 days.

[0098] like Figure 7 As shown in , sampling point A is located 25 cm away from the inner tube of the first annular structure, and solid samples are taken on the 10th, 20th, 30th, 40th, 50th and 60th days, and liquid samples are taken at the same time; sampling point B is located 35.4 cm away from the inner tube of the first annular structure, and solid samples are taken on the 14th, 24th, 34th, 44th, 54th and 64th days, and liquid samples are taken at the same time; sampling point C is located 50 cm away from the inner tube of the first annular structure, and solid samples are taken on the 20th, 30th, 40th, 50th, 60th and 70th days, and liquid samples are taken at the same time; sampling point D is located 56 cm away from the inner tube of the first annular structure, and solid samples are taken on the 23rd, 33rd, 43rd, 53rd, 63rd and 73rd days, and liquid samples are taken at the same time; sampling point E is located 67 cm away from the inner tube of the first annular structure, and solid samples are taken on the 27th, 37th, 47th, 57th, 67th and 77th days, and liquid samples are taken at the same time;

[0099] The test results of the above sampling are:

[0100]

[0101]

[0102]

[0103]

[0104] According to the above test results, the pH of the chemical reduction barrier was fitted based on the generalized additive model, and the fitting results are shown in Table 1. When the chemical reduction barrier was completed (December 28, 2023), the overall average pH was approximately 8.03 (P < 0.001), and there was no significant correlation with the plane spatial distance (P = 0.769), indicating that the chemical reduction barrier was relatively uniform in spatial distribution. Figure 8As shown in the figure. In the early and middle stages of acid water injection, the fitting results at the two time points of 2024.01.10 and 2024.02.15 show that the coefficient of determination (Adjusted R2) reached 1, indicating that the GAM model has a good fit for the process of chemical reduction barrier. The pH at the injection center is approximately 3.2, and the pH in the lower semicircle is significantly lower than that in the upper semicircle, indicating that homogeneity decreases when the chemical reduction barrier takes effect. In the later period, the coefficient of determination of the fitting model at the two time points of 2024.03.15 and 2024.04.01 decreased to 0.36-0.42, indicating that the fitting effect gradually decreased in the later period.

[0105] Table 1 GAM model fitting parameters of chemical reduction barrier pH

[0106]

[0107] Distribution law of chemical reduction barrier Eh changes:

[0108] The Eh of the chemical reduction barrier was fitted, and the fitting results are shown in Table 2. When the chemical reduction barrier was completed (December 28, 2023), the intercept value of Eh was not significant, and there was no significant correlation with the plane space distance (P = 0.769). In the early and middle period of acid water injection, the fitting results at the two time points of January 10, 2024 and February 15, 2024 showed that the determination coefficient of the Eh fitting model was Adjusted R 2 It reached 1, which is similar to the pH simulation results mentioned above, indicating that the GAM model has a better fitting effect in the process of chemical reduction barrier. The Eh of the injection center is about 215, and the radiation diffusion gradually decreases to the surrounding areas. After 2024.03.15, the Eh of the injection center decreased to 86.6 and gradually diffused to the surrounding areas, with an overall average Eh of 19.13. By 2024.04.01, the overall average Eh increased to 28.7. Figure 9 As shown in .

[0109] Table 2 GAM model fitting parameters of chemical reduction barrier Eh

[0110]

[0111]

[0112] Prediction of Chemical Reduction Barrier Effectiveness:

[0113] The GAM model was fitted based on pH, distance from the center, and time data. The model fitting parameters are shown in Table 3. The fitting values ​​of the intercept term β0 and parameter term S(t, d) of the model were statistically significant (P<0.001). The model determination coefficient R 2is 0.81, and the explanation of time and distance from the center for pH is greater than 83.7%, indicating that the model can effectively extrapolate the timeliness of the chemical reduction barrier of the reaction. Based on 3 months of experimental data ( Figure 10 The red dashed line in the middle) and the effect of chemical reduction barrier after 6 months are extrapolated, such as Figure 10 As shown, according to the current flow rate of the test, after 340 days ( Figure 10 The pH at the edge of the 150 cm diameter chemical reduction barrier drops to 3, which is consistent with the original water, indicating that the chemical reduction barrier will be completely ineffective at this time.

[0114] Table 3 Fitting parameters of chemical reduction barrier GAM model (pH~t+d)

[0115]

[0116] The GAM model was fitted based on Eh, distance from the center and time data. Similar to the pH fitting results, the fitting values ​​of the intercept term β0 and parameter term S(t, d) of the model were statistically significant (P<0.001), and the model determination coefficient R 2 is 0.81, and the explanation of time and distance from the center for pH is greater than 83.6%, indicating that the model can effectively extrapolate the timeliness of the chemical reduction barrier of the reaction. Based on 3 months of experimental data ( Figure 10 The red dotted line in the middle) is used to extrapolate the chemical reduction barrier effect for 6 months. According to the current flow rate of the test, after 350 days ( Figure 10 The Eh at the edge of the 150 cm diameter chemical reduction barrier rises to 230 mV, which is consistent with the original water, indicating that the chemical reduction barrier will completely fail at this time.

[0117] Estimating the long-term effectiveness of the reduction barrier under realistic conditions:

[0118] According to the geological report, the permeability coefficients of the first and second cyclic aquifers of the Kuteltai (512) deposit at Factory 737 are 0.09-0.24 m / d, the permeability coefficient of the fifth cyclic aquifer is 0.52-1.16 m / d, and the permeability coefficient of the seventh cyclic aquifer is 0.29 m / d. The groundwater gradient is 0.02-0.03. The groundwater flow rate in each aquifer is 0.00225-0.006 m / d for the first and second cyclic aquifers, 0.013-0.029 m / d for the fifth cyclic aquifer, and 0.00725 m / d for the seventh cyclic aquifer.

[0119] The radius of hole No. 1 of the expanded test reduction barrier is 15 mm, and the average flow rate of the modified hole in the test is 2.83 ml / min. The average flow rate is now converted into cubic millimeters per day, that is, = 2.83*60*24*1000 = 4.075*106 mm3 / d. The flow rate is equal to the flow rate divided by the cross-sectional area. Therefore, the average flow rate is 4.075*106 / (π*202) = 3243 mm / d = 3.243 m / d. Taking the maximum flow rate of the V aquifer as 0.029 m / d, it can be calculated that the flow rate of the indoor expanded reduction barrier test is about 112 times the maximum flow rate of the V aquifer in the actual 737 mining area. That is, 100 days in the reduction barrier can be regarded as equivalent to 47.85 years of natural attenuation process in the 737 mining area, and 340 days corresponds to 162.7 years. This shows that under natural conditions, it takes at least 47 years for the reduction barrier to begin to undergo significant reduction, and 162 years for its function to completely fail.

[0120] According to the above embodiments, the reduction barrier test device and test method for groundwater remediation in in situ uranium leaching provided in this application can effectively simulate the working state of the reduction barrier and provide strong data support for subsequent actual groundwater remediation work.

[0121] The present invention has been described above with reference to preferred embodiments, but these embodiments are merely exemplary and serve only as illustrations. On this basis, various replacements and improvements can be made to the present invention, all of which fall within the scope of protection of the present invention.

Claims

1. A test device for remediation of groundwater reduction barriers in in-situ leaching of uranium, characterized in that: The device includes: A bottom plate (1) and a baffle plate (2) surrounding the bottom plate (1), wherein a plurality of pipe units (3) are vertically arranged on the bottom plate (1). A receiving space is formed by a bottom plate (1) and a baffle plate (2) to receive ore, sand, soil, and water simulating a stratum environment; the plurality of pipe units (3) are distributed in a ring shape within the receiving space; The pipeline unit (3) comprises an inner tube (31) located in the middle and a plurality of outer tubes (32) surrounding the outer portion of the inner tube (31) and abutting against each other. An inner tube opening area (311) is provided on the side wall at the lower end of the inner tube (31); an outer tube opening area (321) is provided on the side wall at the lower end of each outer tube (32), and a plurality of through holes are densely provided on the inner tube opening area (311) and the outer tube opening area (321); The inner tube (31) controls the inflow and outflow of water in the containing space, and the outer tube (32) is filled with ore or sand, and the ore or sand in the outer tube (32) can be drawn out upward, thereby simulating the extraction of underground solid samples by drawing out the ore or sand in the outer tube (32) upward.

2. The in-situ uranium leaching groundwater remediation reduction barrier test device according to claim 1, characterized in that: The outer dimensions of the plurality of outer tubes (32) are consistent. When the plurality of outer tubes (32) and the inner tube (31) are assembled into a pipeline unit (3), the height positions of the inner tube opening area (311) and the outer tube opening area (321) are consistent.

3. The in situ leaching uranium groundwater remediation reduction barrier test device according to claim 2, characterized in that: The inner tube opening area (311) is cylindrical and surrounds the inner tube (31). The outer tube opening area (321) is cylindrical and surrounds the outer tube (32).

4. The in-situ uranium leaching groundwater remediation reduction barrier test device according to claim 3, characterized in that: The flow path of water in the test device is as follows: water enters from the end of the inner tube (31), passes through the inner tube opening area (311) and the outer tube opening area (321), enters the outer tube (32), and then enters the receiving space outside the pipeline unit (3) through the outer tube opening area (321). After reaching another pipeline unit (3), the water reverses the above flow path and is discharged from the inner tube (31) of the pipeline unit.

5. The groundwater remediation reduction barrier test device for in-situ uranium leaching according to claim 1, characterized in that: In the pipeline unit (3), one end of each outer tube (32) abuts against the bottom plate (1), and a detachable sealing end cover is provided on the other end. The outer tube (32) is sealed at both the upper and lower ends by the bottom plate (1) and the sealing end cover.

6. The in-situ uranium leaching groundwater remediation reduction barrier test device according to claim 1, characterized in that: A plurality of through holes are provided on the bottom plate (1), the number of the through holes being consistent with the number of the pipe units (3) and the inner tubes (31), and the bottom end of each inner tube (31) abuts against the through hole; Removable sealing end covers are provided at the top end of the inner tube (31) and the bottom end of the through hole, so that water can flow in and out through the top or bottom of the inner tube (31).

7. The groundwater remediation reduction barrier test device for in-situ uranium leaching according to claim 1, characterized in that: The multiple outer tubes (32) that abut against each other together surround and form a water flow space for accommodating the inner tube (31). The pipeline unit (3) further comprises a sealing cover (33) mounted on the inner side of the plurality of outer tubes (32); a through hole for the inner tube (31) to pass through is provided in the middle of the sealing cover (33); the sealing cover (33) and the bottom plate (1) are used to seal the water flow space at both ends.

8. The groundwater remediation reduction barrier test device for in-situ uranium leaching according to claim 1, characterized in that: In the receiving space, the plurality of pipe units (3) are arranged to form at least four layers of nested annular structures; In the four-layer annular structure, a group of pipeline units (3) located in the center constitutes a first-layer annular structure, 3-5 groups of pipeline units (3) on the periphery thereof constitute a second-layer annular structure, 6-10 groups of pipeline units (3) on the periphery of the second-layer annular structure constitute a third-layer annular structure, and 10-14 groups of pipeline units (3) on the periphery of the third-layer annular structure constitute a fourth-layer annular structure.

9. A test method for remediation of reduction barriers in groundwater during in-situ leaching of uranium, characterized in that: The method is realized by the in-situ uranium leaching groundwater remediation reduction barrier test device described in any one of claims 1 to 8.

10. The method for remediation of groundwater reduction barrier in in situ leaching of uranium according to claim 9, characterized in that: The method comprises the following steps: Step 1: Prepare ore / sand soaked in contaminated water according to the type and quantity of rock and sand to be simulated; Step 2, sample loading, i.e., filling the inner circle of the holding space with ore / sand soaked in contaminated water and ore / sand soaked in uncontaminated water, and filling the outer circle of the holding space with ore / sand soaked in uncontaminated water; filling clay above the inner and outer circles to simulate the surface soil layer and seal; preferably, the inner circle covers the third layer of the annular structure composed of the pipe unit (3); the outer circle covers the fourth layer of the annular structure composed of the pipe unit (3); Step 3, uniformly contaminate the water; that is, inject contaminated water into the inner tube (31) of the first layer of the annular structure, and open the partially sealed end cap on the inner tube (31) of the third layer of the annular structure; Step 4, injecting a reducing agent to form a reduction barrier; that is, injecting the reducing agent from the inner tube (31) of the second layer of the annular structure, and opening the sealing end cap of each inner tube (31) in the third layer of the annular structure; preferably, taking a water sample to know the injection status of the reducing agent; Step 5, determining the effect of the reduction barrier; that is, injecting contaminated water from the inner tube (31) of the first layer of the annular structure, and opening a portion of the sealed end cap on the inner tube (31) of the fourth layer of the annular structure; preferably, extracting water samples and solid samples at different positions on the contaminated water flow path at a predetermined frequency to obtain the effect of the original barrier.

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