Sandstone uranium in-situ leaching interface reaction microfluidic visual analysis method

Abstract

The application provides a sandstone uranium mine in-situ leaching interface reaction microfluidic visual analysis method, and belongs to the cross field of uranium mining, microfluidic and fluorescence sensing. The real sandstone uranium mine core is processed into a slice and embedded into a transparent microfluidic chip to prepare a real sandstone uranium mine microfluidic geological chip. A leaching solution containing an oxidizing agent and a uranyl ion fluorescent probe is prepared and injected into the transparent microfluidic geological chip to generate a fluorescent signal. Under ultraviolet excitation, a fluorescence time sequence image is continuously collected. Based on a fluorescence intensity uranium concentration calibration curve, a uranyl ion concentration field data set is obtained by pixel-by-pixel inversion. Parameters such as instantaneous reaction rate, reaction front migration speed and cumulative leaching rate are calculated. The method realizes real-time, in-situ and visual quantitative analysis of the uranium mine in-situ leaching interface reaction at a real pore scale for the first time. The method has the advantages of high geological authenticity, high space-time resolution and synchronous output of multiple parameters, and provides a reliable technical platform for in-situ leaching process optimization and kinetic model construction.

Description

Technical Field

[0001] This application relates to the interdisciplinary technical fields of uranium mining and metallurgy, microfluidics and fluorescence sensing, and in particular to a microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching. Background Technology

[0002] In-situ leaching is the main method for mining uranium in sandstone uranium deposits. Essentially, it involves the leaching solution seeping through a porous medium and undergoing solid-liquid interface oxidation with the uranium-bearing minerals. Complexation reaction, through the injection of leaching agent into the ore layer, dissolves uranium minerals to form soluble uranyl ions (UO2²). + The leaching agent is then recovered through pumping wells. Therefore, the key to optimizing the leaching process lies in understanding the flow path of the leaching agent at the pore scale, the local dissolution kinetics of uranium, and the migration law of the reaction front.

[0003] Currently, traditional research methods, including column leaching experiments and batch reaction experiments, often rely solely on detecting the concentration of the leachate at the outlet to infer the reaction process. The entire seepage and chemical reaction within the core remains a "black box," preventing researchers from directly observing the fluid-solid coupling process of the leachate in the actual rock pores. Furthermore, they cannot obtain, in real-time and in-situ, the precise location, migration rate, and dynamic changes in the concentration gradient of uranium ions at the pore scale. Reaction rates typically depend on model fitting, resulting in significant errors. This lack of microscopic visualization data severely restricts the accurate construction of in-situ leaching chemical reaction kinetic models and the optimization of leaching processes.

[0004] In recent years, microfluidic technology has provided a new means for pore-scale simulation, but existing studies mostly focus on flow or adsorption behavior in porous media, lacking real-time visualization and quantitative analysis of uranium oxidation processes. On the one hand, most microfluidic models use etched glass or artificial structures, which cannot reproduce the occurrence state and mineral composition of real uranium ore; on the other hand, uranyl ions are invisible under a microscope, and traditional sampling followed by ICP... MS testing methods also cannot achieve spatially resolved real-time monitoring, making it difficult to capture instantaneous changes in the leaching process. Therefore, existing technologies struggle to simultaneously achieve uranium (IV) to uranyl (UO2²) transformation within the pore structure of real minerals. + In-situ identification of reaction interfaces, continuous dynamic tracking of reaction interfaces, and spatially resolved quantitative inversion of reaction rates. Summary of the Invention

[0005] One of the objectives of this application is to provide a microfluidic visualization analysis method for the interfacial reaction of sandstone uranium ore leaching, aiming to solve the problem that existing methods cannot visualize the microfacial reaction of leaching in situ. This method introduces real ore into a microfluidic chip, combined with a uranyl ion-specific fluorescent probe, enabling in-situ, real-time, and visualized tracking of the entire process of leaching agent flow, uranyl ion release and migration. This allows for direct observation of the uranium oxidation reaction location, real-time tracking of the reaction interface migration rate, and quantitative inversion of uranium ion concentration and reaction rate.

[0006] The technical solution of this application is: A microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching includes the following steps: Preparation of a real sandstone uranium ore microfluidic geological chip: Real core samples were collected from a target sandstone-type uranium ore deposit, and thin sections of uranium ore rock were prepared; the thin sections of uranium ore rock were encapsulated on a transparent microfluidic chip to prepare a real sandstone uranium ore microfluidic geological chip; Construction of the leaching solution and uranyl ion fluorescent probe system: A leaching solution simulating in-situ leaching conditions was prepared, comprising an oxidant and a leaching agent (such as acidic, alkaline, and neutral leaching solutions); a uranyl ion (UO2²) fluorescent probe system was selected. + A fluorescent probe molecule with highly specific response and capable of producing fluorescence enhancement effect is used to prepare an leaching solution by mixing the fluorescent probe molecule with a leaching solution, or it can be prepared separately as a developing solution; wherein, the fluorescent probe can react with UO2² + After binding, a fluorescent signal is generated, and the fluorescence intensity of the fluorescent signal is quantitatively related to the uranium concentration, so that the leaching solution can generate a fluorescent signal, and the fluorescence intensity of the generated fluorescent signal is quantitatively related to the uranium concentration; Visualization simulation of in-situ leaching micro-interface reactions: The prepared microfluidic geological chip is placed on the observation stage of a laser confocal microscope or fluorescence microscope. A micro-injection pump is used to inject the prepared leaching solution into the microfluidic geological chip at a set leaching flow rate, allowing it to flow through the uranium ore rock thin section. This generates a fluorescence signal to simulate the in-situ leaching seepage process, and the visualization simulation of the in-situ leaching micro-interface reactions is performed. Specifically, the leaching agent, driven by pressure, flows through the pore network of the uranium ore rock thin section and undergoes an oxidative complexation reaction with the uranium-bearing minerals within the pore network, generating uranyl ions (UO2²⁻). + The leachate flows through the uranium ore rock sheet and then exits through the outlet microchannel in the microfluidic geological chip and is collected for subsequent offline verification and analysis. Real-time acquisition and processing of fluorescence time series images: During the leaching process, the microfluidic geological chip is excited by an ultraviolet excitation light source, and the spatial distribution image of fluorescence signal in the core pores of the uranium ore rock thin section is continuously acquired at preset time intervals to obtain fluorescence time series images of fluorescence intensity changing with time and space. Data analysis and chemical reaction kinetics calculations: Based on a pre-established fluorescence intensity-uranium concentration calibration curve, the obtained fluorescence time-series images are inverted pixel-by-pixel into a real-time uranium concentration dataset showing the change of the uranium ion concentration field over time; based on the real-time uranium concentration dataset, at least one of the following quantitative parameters is calculated: Instantaneous reaction rate at each spatial location; The migration rate of the leaching reaction front; Cumulative leaching rate.

[0007] As one technical solution of this application, a real core sample is collected from a target sandstone-type uranium deposit. The real core sample is cut, polished, and made into a thin slice of the uranium ore rock with a thickness of 100~500μm and a surface roughness of Ra≤10μm. The polished uranium ore rock thin slice is placed in an ultrasonic cleaner, cleaned with deionized water to remove surface debris, and dried for later use. The uranium ore rock thin slice is bonded and encapsulated between two transparent microfluidic chips (such as glass or PDMS), forming a closed microfluidic geological chip with transparent optical material layers on both the top and bottom surfaces. This constructs a microfluidic geological chip that retains the real mineral composition and pore structure and has a light-transmitting observation interface.

[0008] As one technical solution of this application, the top and bottom surfaces of the microfluidic chip are both glass or polydimethylsiloxane material layers, and are provided with positioning grooves that match the uranium ore rock sheet; the uranium ore rock sheet is encapsulated in the positioning grooves corresponding to the two microfluidic chips by laser melting bonding, and together they form a microfluidic geological chip with transparent optical material layers on both the top and bottom surfaces.

[0009] As one technical solution of this application, the leaching solution includes an oxidizing agent and a leaching agent, wherein the oxidizing agent includes H2O2 and the leaching agent includes sulfuric acid.

[0010] As one technical solution of this application, the uranyl ion fluorescent probe is selected from one of the following: A complex formed by a lanthanide ion and an organic ligand, wherein the molar ratio of the lanthanide ion to the organic ligand is 1:1 to 3, and the lanthanide ion is Eu³. + or Tb³ + The organic ligand is thiophenecarboxyltrifluoroacetone, o-phenanthroline, or a mixture thereof; Functionalized quantum dots or carbon dots with surface-modified amide oxime groups; A ratiometric fluorescent probe with dual emission wavelengths.

[0011] As one technical solution of this application, the concentration of the uranyl ion fluorescent probe in the leaching solution is 0.1–10 μmol / L, and the leaching solution is an acidic, alkaline, or neutral leaching agent.

[0012] As one technical solution of this application, the excitation wavelength of the ultraviolet excitation light source is 260–425 nm.

[0013] As one technical solution of this application, the excitation wavelength of the ultraviolet excitation light source is 337nm or 365nm.

[0014] As one technical solution of this application, the ultraviolet excitation source is placed above the microfluidic geological chip, and a fluorescence microscope or a high-sensitivity CMOS camera is placed below or above the microfluidic geological chip. A bandpass filter is installed in front of the lens, and the center wavelength of the bandpass filter matches the emission wavelength of the fluorescent probe (the emission peak of the uranyl ion fluorescent probe is located at 500–550 nm). During the leaching process, uranyl ions in the leachate specifically bind to the fluorescent probe in situ, forming a fluorescent complex and exciting characteristic fluorescence. The fluorescence microscope or the high-sensitivity CMOS camera is turned on, and fluorescence time-series images are continuously acquired at preset time intervals to record the evolution of the spatial distribution of fluorescence intensity in the core pores of the uranium ore rock thin section over time. The acquired fluorescence time-series images are preprocessed sequentially, including background subtraction, noise filtering, and image registration, so as to observe the spatial distribution of fluorescence signals in real time and obtain a fluorescence time-series image sequence that changes over time.

[0015] As one technical solution of this application, the preset time interval for acquiring the fluorescence time series image is 10–300 seconds, and the spatial resolution is 1–10 μm / pixel.

[0016] As one technical solution of this application, data analysis and chemical reaction kinetics calculation specifically include the following steps: Establish a calibration curve between fluorescence intensity and uranyl ion concentration: Under the same excitation and acquisition conditions as those used in the actual experiment, a series of uranyl ion standard solutions with known concentrations (e.g., 0.1, 0.5, 1.0, 5.0, 10.0 μmol / L) were prepared, and fluorescence time-series images were acquired under the same excitation and acquisition conditions. The fluorescence intensity-uranium concentration calibration curve was obtained by fitting the images. ; In the formula: CThe concentration of uranyl ions; α For calibration coefficients; I Fluorescence intensity; I 0 represents background fluorescence; β For calibration coefficients; Pixel-by-pixel quantification and visualization of uranyl ion concentration field: The fluorescence intensity values ​​of each pixel in the real-time acquired fluorescence time-series images are extracted using image processing software. These values ​​are then substituted pixel by pixel into the aforementioned fluorescence intensity-uranyl ion concentration calibration curve, thereby converting the fluorescence time-series images into uranyl ion concentration data and generating a pseudo-color image of the uranyl ion concentration field with spatiotemporal resolution. This enables real-time quantitative determination of uranium concentration at each spatial location (resolution down to the micrometer level). Combined with the ICP-MS verification results of the leachate collected by the microchannel at the outlet of the microfluidic geological chip, the calibration curve can be further corrected and the accuracy of the method can be evaluated. Reaction interface migration speed: The location of the solid-phase interface in the core was determined using image recognition methods, the change of the solid-phase interface location over time was tracked, and the migration rate of the reaction interface was calculated using the following formula: ; In the formula: v front The migration speed of the reaction front; Time interval The positional change of the corresponding reaction front within the interior; For time intervals.

[0017] Spatial distribution of local chemical reaction rates: By combining the rate of change of uranium ion concentration over time (dC / dt), the micro-interface chemical reaction rate at the core pore scale is calculated and output.

[0018] In the formula: R(x,t) x-axis of the core x The instantaneous reaction rate at the point; C(x,y,t) for t The concentration of uranyl ions at each of the aforementioned spatial locations at time t; t For time; By calculation, a reaction rate distribution map can be obtained, which can intuitively show the difference in the rate of uranium dissolution at different locations in the core, thereby identifying highly reactive regions and reaction-retarded regions. Real-time calculation of cumulative leaching rate: Spatial integration of the uranium amide ion concentration field within the core region of the uranium ore thin section yields the change in the total amount of uranium leached from the core over time: ; In the formula: Q(t) This represents the total amount of uranium that has been leached from the rock core. C(x, y, t) for t The concentration of uranyl ions at each of the aforementioned spatial locations at time t; x The x-axis is used for coordinates. y The vertical axis is used as the coordinate. Will Q(t) After normalization, the cumulative leaching rate curve is obtained: ; In the formula: Cumulative leaching rate; Q(t) This represents the total amount of uranium that has been leached from the rock core. Q 总 The total amount of uranium in the core is generally determined by acid digestion of the core, followed by pre-determination using ICP-MS. This curve can be directly compared and verified with the outlet sampling analysis results of traditional column immersion experiments.

[0019] As one technical solution of this application, it also includes multi-parameter coupling and process optimization, which includes the following operation steps: By changing the following process parameters—leaching agent type, leaching agent flow rate (0.1–10 μL / min), leaching agent composition, and core sample type (sandstone of different grades and mineral compositions)—and repeating the above steps in sequence, leaching kinetic data under different conditions were obtained. Based on this, a correlation model of process parameters, pore-scale flow, and uranium leaching kinetics was established, and the optimal leaching process conditions were predicted based on the model to guide actual uranium leaching production.

[0020] The beneficial effects of this application are: (1) This invention innovatively combines microfluidic technology with uranyl ion-specific fluorescent probes, and for the first time realizes real-time in-situ imaging of uranium concentration distribution at the pore scale during leaching. It transforms the previously invisible uranium ion dissolution process into an intuitive fluorescent signal, completely breaking the black box state of traditional experiments. It can clearly observe the preferential flow path of the leaching agent in the complex pore network, the non-uniform advancement of the leaching reaction front, the evolution of pore structure caused by local mineral dissolution, as well as the preferential flow channels and local leaching differences, and realizes real-time high-definition imaging of the location of chemical reaction and concentration gradient.

[0021] (2) This invention has the ability to perform quantitative analysis with high spatiotemporal resolution. Its microfluidic geological chip reduces the consumption of samples and reagents to microliters. The spatial resolution of fluorescence imaging can reach the micrometer level, and the temporal resolution can be controlled at the millisecond level. Through the pre-established fluorescence intensity-uranium concentration calibration curve, each fluorescence time series image can be converted into a uranyl ion concentration distribution map pixel by pixel, realizing the leap from qualitative color reading to quantitative data reading. Based on the fluorescence time series image data of the concentration field, the instantaneous reaction rate of each pixel can be calculated to generate a reaction rate distribution map, thereby accurately identifying hot spots (rapid leaching zone) and dead zones (slow or non-leaching zone) in the core. At the same time, traditional macroscopic kinetics can only measure the overall average reaction rate, while this method can accurately track the position of the reaction front in the micrometer-level pores and directly obtain the chemical reaction rate at the local interface, providing unprecedented low-level accurate data for the correction of the multi-scale geo-percolation-chemical coupling (THMC) model.

[0022] (3) The present invention can output multiple key kinetic parameters in a single experiment, including: the migration speed of the leaching reaction front, the cumulative leaching rate curve, the chemical reaction rate of the micro-interface, and the spatiotemporal evolution of the uranium concentration field; at the same time, it can obtain spatial distribution information through fluorescence time series images, and collect the effluent in the outlet microchannel of the microfluidic geological chip for chemical analysis, realizing dual verification of process visualization and result quantification.

[0023] (4) This invention provides an efficient process optimization platform, which can quickly establish a quantitative relationship between process parameters and leaching efficiency by changing the type of leaching agent, flow rate (0.1–10 μL / min), leaching agent formulation, and core samples with different grades and mineral compositions, and predict the optimal leaching process conditions, providing data support for actual uranium leaching production; this invention is applicable to comparative studies under various conditions and has wide applicability and scalability.

[0024] (5) This invention uses real sandstone uranium ore thin sections to construct a microfluidic geological chip, which fully preserves the original rock's pore structure, mineral composition and uranium occurrence form, and abandons the traditional regular photolithography pore model (such as glass etching or silicon-based model), and restores the heterogeneity, mineral symbiosis and surface wettability of the original ore to the greatest extent. This extremely high geological authenticity makes the measured leaching kinetic parameters have direct engineering guidance value for actual in-situ leaching processes. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0026] Figure 1 This is a schematic diagram of a thin section of uranium ore rock provided in an embodiment of this application; Figure 2 This is a schematic diagram of a microfluidic chip provided in an embodiment of this application; Figure 3 This is a schematic diagram of a microfluidic geological chip provided in an embodiment of this application; Figure 4 A schematic diagram of the in-situ leaching micro-interface reaction experiment between the fluorescence detection module and the microfluidic geological chip provided in this embodiment of the application. Figure 5 This is a schematic diagram illustrating the relationship between fluorescence intensity and uranyl ion concentration, provided in an embodiment of this application. Figure 6 This is a schematic diagram illustrating the linear relationship between fluorescence intensity change and uranyl ion concentration, provided in the embodiments of this application. Figure 7 A pore-scale uranyl ion concentration cloud map provided for an embodiment of this application.

[0027] Icons: 1-Uranium ore rock thin section; 2-Microfluidic chip; 3-Microfluidic geological chip; 4-Ultraviolet excitation source; 5-Injection pump; 6-Uranium amide ion fluorescent probe; 7-Fluorescence microscope; 8-Camera. Detailed Implementation

[0028] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can typically be arranged and designed in various different configurations.

[0029] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0030] It should be noted that similar labels and letters in the following figures indicate similar items. Therefore, once an item is defined in one figure, it does not need to be further defined and explained in subsequent figures.

[0031] In the description of this application, it should be noted that the terms "upper" and "lower" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, or the orientation or positional relationship in which the product of the invention is usually placed when in use. They are only used to facilitate the description of this application and to simplify the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0032] Furthermore, in this application, unless otherwise expressly specified and limited, "above or below" the first feature may include direct contact between the first and second features, or contact between the first and second features through another feature between them. Moreover, "above," "over," and "on" the first feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the first feature includes the first feature located at the lower outer periphery of the second feature and diagonally below it, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0033] Furthermore, terms such as "horizontal" and "vertical" do not imply that components must be absolutely horizontal or suspended, but rather that they can be slightly tilted. For example, "horizontal" simply means that its direction is more horizontal than "vertical," and does not mean that the structure must be completely horizontal, but can be slightly tilted.

[0034] In the description of this application, it should also be noted that, unless otherwise expressly specified and limited, the terms "set up," "connected," and "linked" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0035] Example: Please refer to Figure 1 (Refer to) Figures 2 to 7 This application provides a microfluidic visualization analysis method for the interfacial reaction of sandstone uranium ore in in-situ leaching. This method uses a core sample of a sandstone uranium ore as the research object and is applied to the visualization and quantitative analysis of the sandstone uranium ore during sulfuric acid leaching. It aims to solve the problem of the inability to visualize the microfacial reaction in in-situ leaching in existing methods. In this embodiment, this method is used to conduct an acid leaching experiment, and the specific implementation steps are as follows: (1) Preparation of real sandstone uranium ore microfluidic geological chip 3: Real core samples were collected from the target sandstone uranium ore with a uranium grade of 0.05%; the real core samples were cut into ultrathin rock slices with a thickness of 100–500 μm (0.5 mm was selected in this embodiment) and prepared into uranium ore rock slices 1. The slices were polished on both sides until the surface roughness was less than 10 μm; the polished uranium ore rock slices 1 were placed in an ultrasonic cleaner, cleaned with deionized water to remove surface debris, and dried for later use; the processed uranium ore rock slices 1 were encapsulated between two PDMS microfluidic chips (the upper and lower surfaces of the PDMS microfluidic chip 2 are transparent optical material layers) by laser melting bonding, thereby forming a closed microfluidic unit and jointly constructing a microfluidic geological chip 3 that retains the real mineral composition and pore structure. (2) Construction of the leaching solution and uranyl ion fluorescent probe 6 system: An acidic leaching solution simulating in-situ leaching conditions was prepared, containing an oxidant (H2O2) and a leaching agent (sulfuric acid); in this embodiment, the sulfuric acid concentrations were set to 0.5 g / L, 1.0 g / L, and 2.0 g / L (pH = 1.5–2.5); uranyl ion (UO2²) was selected. + Fluorescent probes with highly specific responses, such as Eu³ + A thiophenecarboxylic acid trifluoroacetone (TTA) complex or Salen derivative was dissolved in a leaching solution, with the probe concentration set at 5–10 μmol / L, to form a leaching solution for acidic leaching experiments; the fluorescent probe reacted with UO2² + After binding, it produces green fluorescence, and the fluorescence intensity is quantitatively related to the uranium concentration; (3) Visual simulation of in-situ leaching micro-interface reaction: The microfluidic geological chip 3 is placed on the observation stage of the fluorescence microscope 7 or the laser confocal microscope. The leaching solution containing the fluorescent probe is injected into the chip at a set flow rate (2 μL / min in this embodiment) using the micro-injection pump 5 to simulate the in-situ leaching process. The leaching solution flows through the pore network of the uranium rock thin section 1 under pressure and undergoes an oxidative complexation reaction with the uranium-containing minerals to generate uranyl ions. The leaching solution is collected through the outlet microchannel on the microfluidic geological chip 3 for subsequent ICP-MS verification analysis. (4) Real-time acquisition and processing of fluorescence time series images: An ultraviolet excitation source 4 (a 365nm LED is used in this embodiment) is set above the microfluidic geological chip 3, and a high-sensitivity CMOS camera 8 is set above the microfluidic geological chip 3. A bandpass filter is installed in front of the lens, and the center wavelength of the bandpass filter matches the probe emission peak (uranyl ion emission peak 500–550nm). The microscope is turned on to continuously acquire fluorescence time series images at time intervals of 30 milliseconds (or 10 milliseconds) to record the evolution of the spatial distribution of fluorescence intensity in the core pores over time. The acquired fluorescence time series images are preprocessed by background subtraction, noise filtering and image registration. (5) Data analysis and chemical reaction kinetics calculations: First, a fluorescence intensity-uranyl ion concentration calibration curve was established: using a series of uranyl ion standard solutions with known concentrations (e.g., 0.1, 0.5, 1.0, 5.0, 10.0 μmol / L), fluorescence time-series images were obtained under the same excitation and acquisition conditions, and the following relationship was obtained by fitting: ; In the formula: C The concentration of uranyl ions; α For calibration coefficients; I Fluorescence intensity; I 0 represents background fluorescence; β For calibration coefficients; The experimental fluorescence time series image obtained in step (4) is converted pixel by pixel into uranyl ion concentration to generate a spatiotemporally resolved concentration field pseudo-color image; the accuracy is verified by combining the ICP-MS results obtained from the leachate flowing out of the outlet microchannel of the microfluidic geological chip 3 with the calibration curve. Secondly, the spatial distribution of chemical reaction rates at the microscopic interface was analyzed: By combining the rate of change of uranium ion concentration over time (dC / dt), the micro-interface chemical reaction rate at the core pore scale is calculated and output.

[0036] In the formula: R(x,t) x-axis of the core x The instantaneous reaction rate at the point; C(x,y,t) for t The concentration of uranyl ions at each of the aforementioned spatial locations at time t; t For time; By calculation, a reaction rate distribution map can be obtained, which can intuitively show the difference in the rate of uranium dissolution at different locations in the core, thereby identifying highly reactive regions and reaction-retarded regions. Next, the migration rate of the reaction interface is calculated: the location of the solid-phase interface in the core is determined by image recognition methods, the change of the interface location over time is tracked, and the migration rate of the reaction interface is calculated. ; In the formula: v front The migration speed of the reaction front; Time interval The positional change of the corresponding reaction front within the interior; For time intervals; Finally, the cumulative leaching rate was calculated in real time: the uranyl ion concentration field in the core region of uranium rock thin section 1 was spatially integrated to obtain the change in the total amount of uranium leached from the core over time. ; In the formula: Q(t) This represents the total amount of uranium that has been leached from the rock core. C(x, y, t) for t The concentration of uranyl ions at each of the aforementioned spatial locations at time t; x The x-axis is used for coordinates. y The vertical axis is used as the coordinate. Will Q(t) After normalization, the cumulative leaching rate curve is obtained: ; In the formula: Cumulative leaching rate; Q(t) This represents the total amount of uranium that has been leached from the rock core. Q 总 The total amount of uranium in the core is generally determined by acid digestion of the core, followed by pre-determination using ICP-MS. This curve can be directly compared and verified with the outlet sampling analysis results of traditional column immersion experiments; (6) Multi-parameter coupling and process optimization: Change the type of leaching agent (acidic, alkaline or neutral), flow rate (0.1–10 μL / min), leaching agent formulation and core samples of different grades, and repeat steps (1) to (5) in sequence to establish a correlation model of process parameters-pore scale flow-uranium leaching kinetics and predict the optimal leaching process conditions.

[0037] The experimental results and verification conclusions obtained from the above-mentioned microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching are as follows: Depend on Figures 5-6It was observed that under UV excitation, green fluorescence signals appeared in the core pores, with the intensity gradually increasing with leaching time. Fluorescence time-series images showed that the leachate preferentially flowed along the high-permeability channels (primary microfractures and coarse-grained sand layers) in the core, forming a "preferred flow" phenomenon; the fluorescence signals in these channels appeared first and increased rapidly, while the signals in low-permeability areas were delayed and increased slowly. At 120 minutes of leaching, the fluorescence signal suddenly weakened in some pores, corresponding to pore blockage caused by particle migration resulting from mineral dissolution.

[0038] Depend on Figures 5-7 The pixel-by-pixel inversion map of uranium concentration shows that the uranium concentration in the preferential flow channel reaches its peak (approximately 8.2 μmol / L) within 30 minutes, while the peak in the low-permeability region (1.5 μmol / L) occurs after 90 minutes. Local reaction rate calculations indicate that approximately 15% of the high-permeability region contributes about 60% of the total leaching; the reaction rate in the low-permeability region is only 1 / 5 to 1 / 10 of that in the high-permeability region. Defining a uranium concentration of 4 μmol / L as the reaction front, tracking data shows that after its formation at the inlet, the front advances towards the outlet at an average speed of 0.8 μm / min. Upon encountering the low-permeability region, it exhibits "flow around," with the migration speed decreasing to 0.2 μm / min. Integrating the concentration field yields a cumulative leaching rate of 47.3% over 240 minutes, which is highly consistent with the ICP-MS result (45.8%) at the outlet of the concurrent column leaching experiment, with a relative error of less than 3%.

[0039] In the control experiment (using leaching solution without fluorescent probe), the correlation coefficient R² between the uranium concentration of the leaching solution collected at the outlet of the microfluidic geological chip 3, measured by ICP-MS, and the average concentration at the outlet obtained from the fluorescence time series image inversion was 0.96, confirming that the fluorescent probe does not affect the normal progress of the leaching reaction and the inversion results are accurate and reliable.

[0040] This embodiment fully demonstrates the visualization and kinetic quantification capabilities of the method of the present invention in the in-situ leaching process of real sandstone uranium deposits, verifying its practical value in optimizing in-situ leaching processes. In this method, a real sandstone uranium core is processed into a thin uranium rock section 1 and embedded in a transparent microfluidic chip 2, preserving the original pore structure and mineral composition. A leaching solution containing an oxidant and a uranyl ion-specific fluorescent probe is prepared and injected into the microfluidic chip 2, causing tetravalent uranium to oxidize and generate uranyl ions, which then bind in situ to the probe to produce a fluorescence signal. The real sandstone uranium microfluidic geological chip 3 continuously acquires fluorescence time-series images under ultraviolet excitation, and the fluorescence intensity is used to determine the fluorescence signal. The uranium concentration calibration curve is inverted pixel-by-pixel to obtain a uranyl ion concentration field dataset with micron-level spatial resolution, which is then used to calculate kinetic parameters such as instantaneous reaction rate, reaction front migration velocity, and cumulative leaching rate. Simultaneously, this embodiment achieves, for the first time, real-time, in-situ, and visualized quantitative analysis of uranium ore in-situ leaching interface reactions at the real pore scale. It boasts advantages such as high geological realism, high spatiotemporal resolution, and simultaneous output of multiple parameters, providing a reliable technical platform for in-situ leaching process optimization and kinetic model construction. Furthermore, this embodiment uses real sandstone uranium ore thin sections to construct a microfluidic geological chip 3, completely preserving the pore structure, mineral composition, and uranium occurrence morphology of the original rock. It abandons traditional regular photolithographic pore models (such as glass etching or silicon-based models), maximally restoring the heterogeneity, mineral coexistence, and surface wettability of the original ore. This extremely high geological realism makes the measured leaching kinetic parameters have direct engineering guidance value for actual in-situ leaching processes.

[0041] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching, characterized in that, Includes the following steps: Real core samples were collected from the target sandstone-type uranium deposit, and thin sections of uranium ore were prepared. The thin sections of uranium ore were then encapsulated on a transparent microfluidic chip to prepare a real sandstone-type uranium ore microfluidic geological chip. A leaching solution is prepared by mixing a leaching solution with a uranyl ion fluorescent probe, so that the leaching solution generates a fluorescent signal, and the fluorescence intensity of the generated fluorescent signal is quantitatively related to the uranium concentration; The leachate is injected into the microfluidic geological chip and flows through the uranium ore rock thin section to generate a fluorescent signal to simulate the in-situ leaching and seepage process, and to visualize the microscopic interface reaction of the in-situ leaching. During the leaching process, the microfluidic geological chip is excited by an ultraviolet excitation light source, and the spatial distribution image of the fluorescence signal in the core pores of the uranium ore rock thin section is continuously acquired at preset time intervals to obtain a fluorescence time series image of fluorescence intensity changing with time and space. Based on a pre-established fluorescence intensity-uranium concentration calibration curve, the obtained fluorescence time-series image is inverted pixel-by-pixel into a real-time uranium concentration dataset showing the change of the uranium acyl ion concentration field over time; based on the real-time uranium concentration dataset, at least one of the following quantitative parameters is calculated: Instantaneous reaction rate at each spatial location; The migration rate of the leaching reaction front; Cumulative leaching rate.

2. The microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching according to claim 1, characterized in that, The real core sample is cut, polished, and made into a thin sheet of uranium ore rock with a thickness of 50~500μm and a surface roughness of Ra≤10μm. The thin sheet of uranium ore rock is placed in an ultrasonic cleaner, cleaned with deionized water to remove surface debris, and dried. The thin sheet of uranium ore rock is bonded and encapsulated between two transparent microfluidic chips, forming a microfluidic geological chip with transparent optical material layers on both the top and bottom surfaces.

3. The microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching according to claim 1, characterized in that, The top and bottom surfaces of the microfluidic chip are both glass or polydimethylsiloxane material layers, and are provided with positioning grooves that match the uranium ore rock sheet; the uranium ore rock sheet is encapsulated in the positioning grooves corresponding to the two microfluidic chips, and together they form the microfluidic geological chip with transparent optical material layers on both the top and bottom surfaces.

4. The microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching according to claim 1, characterized in that, The uranyl ion fluorescent probe is selected from one of the following: Complexes formed by lanthanide ions and organic ligands, wherein the lanthanide ions are Eu³ + or Tb³ + The organic ligand is thiophenecarboxyltrifluoroacetone, o-phenanthroline, or a mixture thereof; Functionalized quantum dots or carbon dots with surface-modified amide oxime groups; A ratiometric fluorescent probe with dual emission wavelengths.

5. The microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching according to claim 1, characterized in that, The concentration of the uranyl ion fluorescent probe in the leachate is 0.1–10 μmol / L.

6. The microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching according to claim 1, characterized in that, The excitation wavelength of the ultraviolet excitation source is 260–425 nm.

7. The microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching according to claim 6, characterized in that, The ultraviolet excitation source has an excitation wavelength of 337 nm or 365 nm.

8. The microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching according to claim 1, characterized in that, The fluorescence signal in the core pores of the uranium ore rock thin section was acquired by a fluorescence microscope or a CMOS camera, with a bandpass filter installed in front of the lens; the center wavelength of the bandpass filter matched the emission wavelength of the uranyl ion fluorescent probe, and the emission peak of the uranyl ion fluorescent probe was located at 500–550 nm.

9. The microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching according to claim 1, characterized in that, The preset time interval for acquiring the fluorescence time series images is 10–300 seconds, and the spatial resolution is 1–10 μm / pixel.

10. The microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching according to claim 1, characterized in that, The fluorescence intensity-uranium concentration calibration curve was established in the following manner: Under the same excitation and acquisition conditions consistent with actual experimental operating parameters, a series of uranyl ion standard solutions of known concentrations were prepared, and fluorescence time-series images were acquired under the same excitation and acquisition conditions. The fluorescence intensity-uranium concentration calibration curve was obtained by fitting the images. ； In the formula: C The concentration of uranyl ions; α For calibration coefficients; I Fluorescence intensity; I 0 represents background fluorescence; β This is the calibration coefficient.

11. The microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching according to claim 1, characterized in that, Instantaneous reaction rate at each of the aforementioned spatial locations R(x,y,t) The following formula is used to calculate and generate a spatial distribution map of the reaction rate, which is then used to identify differences in leaching activity in different regions of the core of the uranium ore rock thin section: ； In the formula: R(x,y,t) The instantaneous reaction rate at each of the aforementioned spatial locations; C(x,y,t) Let be the concentration of uranyl ions at each of the aforementioned spatial locations at time t; t For time.

12. The microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching according to claim 1, characterized in that, The leaching reaction front is calculated by tracking the change in the position of the solid-phase interface of the core over time to determine the migration rate. ； In the formula: v front The migration speed of the reaction front; Time interval The positional change of the corresponding reaction front within the interior; For time intervals.

13. The microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching according to claim 1, characterized in that, The cumulative leaching rate η(t) Calculated using the following formula: ； In the formula: η(t) Cumulative leaching rate C(x,y,t) for t The concentration of uranyl ions at each of the aforementioned spatial locations at time t; x The x-axis is used for coordinates. y The vertical axis is used as the coordinate. Q 总 This represents the total amount of uranium in the rock core.

14. The microfluidic visualization analysis method for interfacial reactions in sandstone uranium ore leaching according to claim 1, characterized in that, It also includes parameter coupling and process optimization, the steps of which include: By changing the process parameters and repeating the steps in claim 1 in sequence, leaching kinetic data under different conditions are obtained; a correlation model of process parameters-pore-scale flow-uranium leaching kinetics is established, and the optimal leaching process conditions are predicted based on the correlation model to guide actual uranium leaching production; wherein, the process parameters include leaching agent type, leaching agent flow rate, leaching agent composition and core sample type.

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