Method for uranium leaching and extraction by MICP with CO2 phased regulation

Abstract

The present application relates to the technical field of uranium mining, in particular to a method for MICP synergistic in-situ leaching of uranium by CO2 phased regulation. The method comprises the following steps: reducing the pressure of in-situ leaching liquid to 0.1-0.15 MPa; introducing a MICP front reactor and inoculating microbial liquid to remove calcium; adsorbing and recovering uranium in the liquid through a resin adsorption tower; introducing a MICP rear reactor and inoculating microbial liquid to regenerate bicarbonate; performing pre-filtration, sterilization treatment and microfiltration, introducing mixed gas containing CO2 and O2, adjusting the pH value and pressurizing, and then reinjecting into the uranium ore layer, with the CO2 partial pressure in the reinjection liquid being controlled at 0.3-0.5 MPa. The present application has systematic advantages in improving uranium recovery rate, reducing scaling risk, replacing exogenous carbonate, realizing safe reinjection of tail liquid and CO2 recycling, and provides reliable support for green and efficient uranium mining.

Description

Technical Field

[0001] This invention relates to the field of uranium mining technology, and in particular to a method for uranium mining using a phased CO2-controlled MIP-coordinated in-situ leaching process. Background Technology

[0002] As a vital strategic energy resource, the green and efficient mining of uranium is crucial for ensuring energy security. CO2+O2 in-situ leaching technology has become the mainstream development method for sandstone-type uranium deposits due to its environmental friendliness and low cost. This technology involves injecting a leaching agent containing CO2 (typically at a partial pressure of 0.3-0.5 MPa) into the ore layer, causing CO2 to react with groundwater to form bicarbonate (HCO3-). - ), and then react with uranyl ions (UO2) 2+ This combines to form soluble [UO2(CO3)3] 4- Complexes are formed, thereby increasing the uranium leaching rate.

[0003] However, this process still faces a series of technical bottlenecks in its practical application. Infiltration solutions generally contain high concentrations of calcium ions (Ca). 2+ (Typically 100-500 mg / L), which readily reacts with [UO2(CO3)3] during leaching. 4- The complex further complexes to form electrically neutral Ca2UO2(CO3)3, which is difficult to be adsorbed. 0 Ternary complexes significantly reduce the extraction efficiency of uranium in subsequent resin adsorption processes. Simultaneously, calcium ions react with carbonate ions to form calcium carbonate precipitates on the resin surface, causing resin blockage and contamination. This not only affects adsorption capacity but also incurs high costs associated with frequent resin replacement. Traditional chemical calcium removal methods (such as adding Na₂CO₃) can partially reduce calcium concentration, but they introduce additional impurity ions, causing secondary pollution, and are costly and uneconomical. Furthermore, for low-carbonate uranium aquifers ([HCO₃⁻]), - [<100mg / L] To maintain sufficient leaching capacity, it is often necessary to continuously add exogenous ammonium bicarbonate, which not only increases the cost of raw material procurement and transportation, but also increases the complexity of the process and the environmental burden. Summary of the Invention

[0004] The purpose of this invention is to address the problems existing in the prior art by providing a staged CO2-controlled MIP-coordinated in-situ leaching method for uranium mining. This method employs a staged CO2 control strategy to achieve efficient calcium removal and bicarbonate regeneration. The method of this invention demonstrates systematic advantages in improving uranium recovery rate, reducing scaling risk, replacing exogenous carbonates, achieving safe reinjection of tailings, and recycling CO2, providing reliable technical support for the green and efficient mining of uranium.

[0005] To achieve the above objectives, this invention provides a CO2-stage controlled MIP-coordinated uranium leaching method, comprising the following steps:

[0006] S1. The leaching solution is subjected to depressurization treatment to reduce its pressure to 0.1-0.15 MPa;

[0007] S2. The leaching extract after the decompression treatment in S1 is introduced into the MICP pre-reactor and inoculated with the first microbial inoculum to remove calcium ions from the liquid.

[0008] S3. The liquid treated by S2 is passed through a resin adsorption tower to adsorb and recover uranium.

[0009] S4. The tail liquid after uranium extraction by adsorption in S3 is introduced into the MICP post-reactor and inoculated with a second microbial culture to regenerate bicarbonate.

[0010] S5. The tailings after S4 are pre-filtered, sterilized and micro-filtered in sequence to obtain reinjection fluid that meets the reinjection standards.

[0011] S6. A mixed gas containing CO2 and O2 is introduced into the reinjection fluid after S5 treatment, its pH value is adjusted and pressurized, and then reinjected into the uranium ore layer; wherein, the partial pressure of CO2 in the reinjection fluid is controlled to be 0.3-0.5 MPa.

[0012] Preferably, in S1, the pressure reduction is achieved through a stepped pressure relief device, which includes multiple pressure relief tanks connected in series.

[0013] Preferably, in S2, the effective microbial species in the first microbial culture solution is Bacillus pasteurellii, and the inoculation amount of the first microbial culture solution is 4%-8%;

[0014] In S2, the reaction occurs at a pH of 9.0-10.0, a temperature of 20-35℃, and a time of 1-3 hours.

[0015] Preferably, in step S3, the flow rate of the liquid through the resin adsorption tower is 2-3 BV / h; and the uranium concentration in the tail liquid after adsorption is completed is not higher than 0.5 mg / L.

[0016] Preferably, in S4, the effective microbial species in the second microbial culture solution is Bacillus pasteurellii, and the inoculation amount of the second microbial culture solution is 4%-8%;

[0017] In S4, the reaction is carried out at a pH of 9.0-10.0, a temperature of 20-35℃, and a time of 0.5-2h.

[0018] Preferably, in S5, the pore size of the pre-filter is 45-55 micrometers; the pore size of the microfilter is 0.12-0.32 micrometers.

[0019] Preferably, in S5, the sterilization treatment is ultraviolet sterilization, the irradiation time is 20-30 min, and the total number of colonies in the reinjection solution after sterilization treatment does not exceed 10 CFU / mL.

[0020] Preferably, in step S6, the pH of the reinjection fluid is adjusted to 6.5-7.5 by introducing a mixture of CO2 and O2 gas.

[0021] The present invention also provides a CO2-stage controlled MICP-coordinated uranium leaching system for realizing the CO2-stage controlled MICP-coordinated uranium leaching method, comprising a leachate depressurization device, a MICP pre-reactor, a resin adsorption tower, a MICP post-reactor, a tailings treatment unit, and a pressurized reinjection unit connected in sequence.

[0022] Preferably, the urease activity monitoring probes are installed in the MICP pre-reactor and the MICP post-reactor, and are linked to the microbial culture replenishment system.

[0023] The beneficial effects of this invention are as follows:

[0024] 1. This invention provides a method for uranium mining using a phased CO2-controlled MICP-coordinated in-situ leaching process, comprising the following steps: S1. Depressurizing the in-situ leaching fluid to reduce its pressure to 0.1-0.15 MPa; S2. Introducing the depressurized in-situ leaching fluid from S1 into a MICP pre-reactor and inoculating it with a first microbial culture to remove calcium ions from the liquid; S3. Passing the liquid treated in S2 through a resin adsorption tower to adsorb and recover uranium; S4. Introducing the tailings after uranium extraction from S3 into a MICP post-reactor and inoculating it with a second microbial culture to regenerate bicarbonate; S5. Performing pre-filtration, sterilization, and microfiltration sequentially on the tailings treated in S4 to obtain a reinjection fluid that meets reinjection standards; S6. Introducing a mixed gas containing CO2 and O2 into the reinjection fluid treated in S5, adjusting its pH value, pressurizing it, and then reinjecting it into the uranium ore layer; wherein the partial pressure of CO2 in the reinjection fluid is controlled to be 0.3-0.5 MPa. This invention is based on MICP (Microbial Induced Carbonate Precipitation) technology and employs a staged CO2 control strategy to achieve efficient calcium removal and bicarbonate regeneration. By reducing the pressure of the leaching solution to 0.1 MPa, a suitable growth and metabolic environment is provided for the microorganisms in the MICP pre-reactor, thereby efficiently inducing calcium carbonate precipitation, improving the calcium removal rate, and effectively avoiding the risk of resin scaling. After this step, the uranium adsorption rate of the resin adsorption tower remains at an extremely high level. In the MICP post-reactor, the microbial metabolic process significantly increases the bicarbonate concentration in the adsorption tailings, replacing the reliance on externally added ammonium bicarbonate in traditional processes. This not only ensures continuous and efficient uranium leaching capacity but also significantly reduces raw material costs and logistical burden. Through tailings treatment measures of "pre-filtration, sterilization, microfiltration, and pH adjustment," the problems of microbial proliferation and chemical precipitation leading to clogging of permeability channels in the ore layer are effectively prevented. After reinjection, the ore layer permeability is maintained at over 95%, achieving a safe closed-loop circulation of the leaching solution.

[0025] 2. In addition, the CO2 released during the depressurization process is condensed, dehydrated, compressed and liquefied, and then fed back to the pressurized inlet of the leaching section, forming an endogenous CO2 circulation loop. This significantly reduces the consumption of purchased CO2, lowers the system operating cost, and improves the green and low-carbon level of the process.

[0026] 3. Through a linkage control mechanism including urease activity monitoring, online uranium concentration detection, and automatic replenishment of microbial culture, the system achieves precise control over key aspects such as the MIP reaction, resin adsorption, and tail liquid treatment, ensuring stable operation and efficient output of the process under a wide range of calcium ion loads.

[0027] In summary, this invention demonstrates systematic advantages in improving uranium recovery rate, reducing scaling risk, replacing exogenous carbonates, achieving safe reinjection of tailings liquid, and recycling CO2, providing reliable technical support for green and efficient uranium mining. Attached Figure Description

[0028] Figure 1 This is a schematic diagram of the MICP-coordinated uranium leaching process with CO2 staged regulation in this invention. Detailed Implementation

[0029] This invention provides a CO2-stage controlled MICP-coordinated uranium leaching method, comprising the following steps:

[0030] S1. The leaching solution is subjected to depressurization treatment to reduce its pressure to 0.1-0.15 MPa;

[0031] S2. The leaching extract after the decompression treatment in S1 is introduced into the MICP pre-reactor and inoculated with the first microbial inoculum to remove calcium ions from the liquid.

[0032] S3. The liquid treated by S2 is passed through a resin adsorption tower to adsorb and recover uranium.

[0033] S4. The tail liquid after uranium extraction by adsorption in S3 is introduced into the MICP post-reactor and inoculated with a second microbial culture to regenerate bicarbonate.

[0034] S5. The tailings after S4 are pre-filtered, sterilized and micro-filtered in sequence to obtain reinjection fluid that meets the reinjection standards.

[0035] S6. A mixed gas containing CO2 and O2 is introduced into the reinjection fluid after S5 treatment, its pH value is adjusted and pressurized, and then reinjected into the uranium ore layer; wherein, the partial pressure of CO2 in the reinjection fluid is controlled to be 0.3-0.5 MPa.

[0036] MICP stands for Microbial Induced Carbonate Precipitation.

[0037] In this invention, in S1, the pressure reduction process is achieved through a stepped pressure relief device, which includes multiple pressure relief tanks connected in series.

[0038] In this invention, the multi-stage pressure relief tanks connected in series include at least two stages of pressure relief tanks connected in series. The last stage pressure relief tank is equipped with an online CO2 partial pressure monitoring instrument to monitor and ensure that the CO2 partial pressure after pressure reduction meets the MICP process requirements.

[0039] In this invention, the final stage pressure relief tank is also connected to an N2 buffer system, which is used to introduce N2 to precisely control and maintain the CO2 partial pressure less than or equal to 0.03 MPa.

[0040] In this invention, the gas (mainly CO2) released by the stepped pressure relief device enters the closed-loop recovery unit: the unit first condenses and dehydrates the gas to remove the water it carries; then it is compressed and liquefied to form high-density liquid CO2; finally, the liquid CO2 is transported through pipeline to the inlet of the pressurization system of the leaching section, and is injected into the ore layer under pressure together with the freshly replenished CO2.

[0041] In this invention, in S2, the effective microbial strain in the first microbial culture is Bacillus pasteurellii, with the preservation number CGMCC No. 1.3687 (corresponding ATCC number 11859). This strain can be obtained publicly from the China General Microbiological Culture Collection Center (CGMCC).

[0042] In this invention, the preparation method of the first microbial inoculum in step S2 is as follows:

[0043] First, open the ampoule containing vacuum-freezed Bacillus pasteurellii. Using a sterile pipette, add 0.3-0.5 mL of 0907 urea medium (composition: 5 g / L peptone, 3 g / L meat extract, 20 g / L urea, pH 7.0) to the ampoule. Gently shake to fully dissolve the freeze-dried bacteria, forming a bacterial suspension. Then, transfer the entire bacterial suspension to a slant of 0907 urea solid medium (composition: 5 g / L peptone, 3 g / L meat extract, 20 g / L urea, 15 g / L agar, pH 7.0) and incubate statically at 29-31°C for 24-48 hours. After cultivation, single colonies were picked from the plates and inoculated into Erlenmeyer flasks containing 50-100 mL of 0907 urea liquid medium (composition: 5 g / L peptone, 3 g / L meat extract, 20 g / L urea, pH 7.0). The flasks were then incubated at 29-31℃ and 150-200 rpm for 12-16 hours to obtain the seed culture. Finally, the seed culture was transferred at an inoculation rate of 1-5% (v / v) to fresh 0907 urea liquid medium (composition: 5 g / L peptone, 3 g / L meat extract, 20 g / L urea, pH 7.0). The culture was continued under the same conditions (29-31℃, 150-200 rpm) for 8-12 hours until the OD600 value reached 0.9-1.1, at which point the first microbial culture was obtained.

[0044] In this invention, in S2, the inoculation amount of the first microbial solution (the inoculation amount of the microbial solution refers to the percentage of the volume of the microbial solution to the volume of the leaching liquid after the decompression treatment in S1) is 4%-8%.

[0045] In this invention, during S2, urea is added simultaneously as a metabolic substrate when inoculating the first microbial culture. The amount of urea added is determined based on the molar concentration of calcium ions in the leaching solution and the target calcium removal efficiency.

[0046] In this invention, the molar ratio of urea to calcium ions is controlled at 1.0-1.2:1.

[0047] In this invention, in S2, the pH of the reaction is 9.0-10.0, the temperature is 20-35℃, and the time is 1-3h.

[0048] In this invention, in step S3, the resin adsorption tower is filled with a strongly basic anion exchange resin, and the particle size of the strongly basic anion exchange resin is 0.4-0.6 mm.

[0049] In this invention, in step S3, an online uranium concentration monitoring instrument is installed at the outlet of the resin adsorption tower and is linked to the adsorption flow rate control system; the flow rate of the liquid through the resin adsorption tower is 2-3 BV / h; and the uranium concentration in the tail liquid obtained after adsorption is not higher than 0.5 mg / L.

[0050] In this invention, in step S4, the effective microbial strain in the second microbial culture is *Bacillus pasteurellii*, with the accession number CGMCC No. 1.3687 (corresponding ATCC number 11859). This strain can be publicly obtained from the China General Microbiological Culture Collection Center (CGMCC).

[0051] In this invention, the preparation method of the second microbial culture in step S4 is as follows:

[0052] First, open the ampoule containing vacuum-freezed Bacillus pasteurellii. Using a sterile pipette, add 0.3-0.5 mL of 0907 urea medium (composition: 5 g / L peptone, 3 g / L meat extract, 20 g / L urea, pH 7.0) to the ampoule. Gently shake to fully dissolve the freeze-dried bacteria, forming a bacterial suspension. Then, transfer the entire bacterial suspension to a slant of 0907 urea solid medium (composition: 5 g / L peptone, 3 g / L meat extract, 20 g / L urea, 15 g / L agar, pH 7.0) and incubate statically at 29-31°C for 24-48 hours. After cultivation, single colonies are picked from the plates and inoculated into Erlenmeyer flasks containing 50-100 mL of 0907 urea liquid medium (composition: 5 g / L peptone, 3 g / L meat extract, 20 g / L urea, pH 7.0). The flasks are then incubated at 29-31℃ and 150-200 rpm for 12-16 hours to obtain the seed culture. Finally, the seed culture is transferred at an inoculation rate of 1-5% (v / v) to fresh 0907 urea liquid medium (composition: 5 g / L peptone, 3 g / L meat extract, 20 g / L urea, pH 7.0). The culture is continued under the same conditions (29-31℃, 150-200 rpm) for 8-12 hours until the OD600 value reaches 0.9-1.1, at which point the second microbial culture is obtained.

[0053] In this invention, in S4, the inoculation amount of the second microbial solution is 4%-8% (the inoculation amount of the microbial solution refers to the percentage of the volume of the microbial solution relative to the volume of the tail liquid after uranium extraction in S3).

[0054] In this invention, in step S4, the pH of the reaction is 9.0-10.0, the temperature is 20-35℃, and the time is 0.5-2h.

[0055] In this invention, in S5, the pore size of the pre-filter is 45-55 micrometers; the pore size of the microfilter is 0.12-0.32 micrometers.

[0056] In this invention, in step S5, the sterilization process is ultraviolet sterilization, which uses ultraviolet light with a wavelength of 254nm to ensure the elimination of biological activity. The sterilization system integrates an automatic mechanical scraping and chemical cleaning system to automatically remove dirt from the surface of the ultraviolet lamp tube, ensuring that the sterilization intensity remains stable. The sterilization time is 20-30 minutes, and the total number of colonies in the reinjection solution after the sterilization process does not exceed 10 CFU / mL.

[0057] In this invention, in step S6, the pH value of the reinjection fluid is adjusted to 6.5-7.5 by introducing a mixed gas of CO2 and O2.

[0058] In this invention, in S6, maintaining the CO2 partial pressure at 0.3-0.5 MPa is beneficial for promoting bicarbonate leaching of uranium.

[0059] In this invention, the exhaust port at the top of the sterilization tank is connected to a condensation sterilization device to cool and biologically intercept the waste gas generated during the sterilization process. The treated clean waste gas is finally introduced into the CO2 recovery unit to realize the recycling of resources and the closed-loop control of waste gas.

[0060] The present invention also provides a CO2-stage controlled MICP-coordinated uranium leaching system for realizing the CO2-stage controlled MICP-coordinated uranium leaching method, comprising a leachate depressurization device, a MICP pre-reactor, a resin adsorption tower, a MICP post-reactor, a tailings treatment unit, and a pressurized reinjection unit connected in sequence.

[0061] In this invention, the tail liquid treatment unit includes a pre-filter, a sterilization tank, a microfilter, and a pH adjustment tower; the pH adjustment tower is equipped with a CO2 and O2 mixed gas inlet and an online pH sensor.

[0062] In this invention, the leachate depressurization device is used to reduce the total pressure inside the pipe of the leaching extract; the tailings treatment unit is used to perform pre-filtration, sterilization, microfiltration and pH adjustment on the tailings in sequence.

[0063] In this invention, urease activity monitoring probes are installed in the MICP pre-reactor and MICP post-reactor, and are linked to the microbial culture replenishment system.

[0064] In this invention, the urease activity monitoring probe characterizes urease activity in real time by monitoring changes in solution conductivity, specifically as the change in conductivity every 5 minutes. The activity index is used as an indicator; when the activity index is lower than 0.1 mS / (cm·min), the device is automatically triggered and linked with the microbial liquid replenishment system to add microbial liquid to the reactor.

[0065] Taking a multi-stage series pressure relief tank as an example (e.g., a three-stage series pressure relief tank), the schematic diagram of the MICP-coordinated uranium leaching process with CO2 staged regulation in this invention is shown below. Figure 1 As shown.

[0066] The present invention will be further described below with reference to embodiments. Unless otherwise defined, the technical or scientific terms used in this invention should have the ordinary meaning understood by one of ordinary skill in the art. The features mentioned above or in the specific examples mentioned in this invention can be combined arbitrarily, and these specific embodiments are only used to illustrate the invention and are not intended to limit the scope of the invention.

[0067] In the following embodiments of the present invention, the strongly basic anion exchange resin filled in the resin adsorption tower was provided by Langfang Woheng Chemical Co., Ltd., specifically 201×7 (717) strongly basic anion exchange resin. The preparation process of the Bacillus pasteurellii bacterial suspension is as follows: First, open the ampoule containing vacuum freeze-dried Bacillus pasteurellii, and use a sterile pipette to draw 0.3 mL of 0907 urea medium (composition: peptone 5 g / L, meat extract 3 g / L, urea 20 g / L, pH 7.0) and drop it into the ampoule. Gently shake to fully dissolve the freeze-dried bacteria and form a bacterial suspension. Then, transfer the entire bacterial suspension to a slant of 0907 urea solid medium (composition: peptone 5 g / L, meat extract 3 g / L, urea 20 g / L, agar 15 g / L, pH 7.0) and incubate statically at 30°C for 36 h. After cultivation, a single colony was picked from the plate and inoculated into an Erlenmeyer flask containing 75 mL of 0907 urea liquid medium (composition: 5 g / L peptone, 3 g / L meat extract, 20 g / L urea, pH 7.0). The flask was then incubated at 30°C and 175 rpm for 14 h to obtain the seed culture. Finally, the seed culture was transferred at an inoculation rate of 3% (v / v) to fresh 0907 urea liquid medium (composition: 5 g / L peptone, 3 g / L meat extract, 20 g / L urea, pH 7.0). The culture was continued under the same conditions (30°C, 175 rpm) for 10 h until the OD600 value reached 1.0, thus obtaining the *Bacillus pasteurellis* bacterial culture.

[0068] Example 1

[0069] This embodiment provides a CO2-stage controlled MIP-coordinated uranium leaching method, comprising the following steps:

[0070] The leaching solution is depressurized by a stepped pressure relief device (three pressure relief tanks connected in series), which gradually reduces the pressure from 0.4 MPa to 0.3 MPa, 0.2 MPa and 0.1 MPa. At the same time, N2 buffer gas is introduced into the last pressure relief tank to make the CO2 partial pressure less than 0.03 MPa.

[0071] The depressurized leaching extract was introduced into the MICP pre-reactor and inoculated with Bacillus pasteurellium culture (6% inoculum). Urea was added as a metabolic substrate, and the molar ratio of urea to calcium ions in the leaching extract was controlled at 1.1:1. The reaction was then started, and the pH of the system was naturally increased by the microbial hydrolysis of urea. The pH was finely adjusted by adding dilute alkaline solution (0.1 mol / L sodium hydroxide solution) or dilute acid solution (0.1 mol / L hydrochloric acid solution) dropwise through the pH automatic control system to stabilize the pH value at 9.0 during the reaction. The reaction was carried out at 30°C for 2 hours.

[0072] The liquid obtained from the reaction is passed through a resin adsorption tower filled with strongly basic anion exchange resin (particle size of 0.5 mm) at a flow rate of 2.5 BV / h to adsorb and recover uranium.

[0073] The tailings after uranium adsorption and extraction were introduced into the MICP post-reactor and inoculated with Bacillus pasteurellii culture (inoculation amount of 6%). The reaction was started, and the pH was finely adjusted by adding dilute alkali solution (0.1 mol / L sodium hydroxide solution) or dilute acid solution (0.1 mol / L hydrochloric acid solution) dropwise through the pH automatic control system to stabilize the pH value of the reaction process at 9.0. The reaction was carried out at 30°C for 2 hours.

[0074] Finally, the treated tailings are sequentially subjected to pre-filtration (50 micrometers pore size), sterilization (254nm ultraviolet sterilization for 20 minutes), and microfiltration (0.22 micrometers pore size) to remove bacteria and particulate matter, resulting in reinjection fluid that meets reinjection standards.

[0075] A mixed gas containing CO2 and O2 is introduced into the reinjection fluid, its pH value is adjusted to 6.5-7.5 and pressurized, and then reinjected into the uranium ore layer; wherein the partial pressure of CO2 in the reinjection fluid is controlled to be 0.4 MPa.

[0076] The changes in key parameters at different stages in this embodiment are shown in Table 1.

[0077] Table 1. Changes in key parameters at different stages in Example 1

[0078]

[0079] In this embodiment, the uranium concentration in the leaching solution was 30 mg / L, the calcium ion concentration was 40 mg / L, the bicarbonate concentration was 1000 mg / L, and the pH was 6.8. After the MIP pretreatment, the effluent quality was significantly improved: the calcium ion concentration decreased to 7.61 ± 2.83 mg / L, and the calcium removal rate reached 81%, effectively controlling the risk of resin scaling. Simultaneously, under the action of microbial metabolism, the bicarbonate concentration increased to 1091.67 ± 38.19 mg / L, achieving in-situ enhancement of the leaching components. During this stage, the uranium concentration remained at 28.62 ± 0.18 mg / L, with a loss rate of only 4.6%, indicating that the calcium removal process had minimal impact on uranium recovery. Subsequently, the liquid entered the resin adsorption tower, where uranium was adsorbed and recovered using a strongly basic anion exchange resin. After treatment, the uranium concentration in the tailings decreased to 0.28 ± 0.07 mg / L, and the uranium adsorption rate reached as high as 97.8%, fully verifying the effect of the MIP pretreatment on calcium removal and its enhancement of resin adsorption performance. During this process, bicarbonate is consumed in the adsorption reaction, reducing its concentration to 788.33±37.53 mg / L, and the pH correspondingly decreases to 6.33±0.08. In the post-MICP reaction, bicarbonate is efficiently replenished, and its concentration significantly recovers to 1975.00±25.00 mg / L, fully capable of replacing added ammonium bicarbonate; the calcium ion concentration further decreases to 5.02±0.54 mg / L at this stage. Finally, the tailings, after pre-filtration, sterilization, and microfiltration, achieve a uranium concentration as low as 0.18±0.01 mg / L and a total bacterial count below 10 CFU / mL. Finally, a mixture of CO2 and O2 is introduced to adjust the pH to 6.5-7.5 before reinjecting it into the uranium deposit.

[0080] The above water quality data show that this method successfully produces efficient, safe and economical regenerated leaching agent. After reinjection, the permeability of the ore layer is maintained at more than 95%, realizing the recycling of leaching agent and stable system operation.

[0081] Example 2

[0082] This embodiment provides a CO2-stage controlled MIP-coordinated uranium leaching method, which follows the same procedure as Embodiment 1, except for the key parameters. Specifically, the changes in key parameters at different stages in this embodiment are shown in Table 2.

[0083] Table 2. Changes in key parameters at different stages in Example 2

[0084]

[0085] Example 3

[0086] This embodiment provides a CO2-stage controlled MIP-coordinated uranium leaching method, which follows the same procedure as Embodiment 1, except for the key parameters. Specifically, the changes in key parameters at different stages in this embodiment are shown in Table 3.

[0087] Table 3. Changes in key parameters at different stages in Example 3

[0088]

[0089] As shown in Table 3, even with an initial calcium ion concentration of 200 mg / L in the leaching solution, the calcium ion concentration significantly decreased to 16.24 ± 1.70 mg / L after treatment with the MIP process. This demonstrates that the process maintains extremely high calcium removal efficiency even under high calcium ion concentration conditions, effectively curbing the risk of resin scaling. Simultaneously, the uranium concentration at the outlet of the subsequent resin adsorption unit decreased to 0.24 ± 0.04 mg / L, fully verifying the reliable role of efficient calcium removal in ensuring the resin adsorption performance.

[0090] Example 4

[0091] This embodiment provides a CO2-stage controlled MIP-coordinated uranium leaching method, which follows the same procedure as Embodiment 1, except for the key parameters. Specifically, the changes in key parameters at different stages in this embodiment are shown in Table 4.

[0092] Table 4. Changes in key parameters at different stages in Example 4

[0093]

[0094] As can be seen from the data in Table 4, under extreme conditions where the initial calcium ion concentration in the leaching solution is as high as 400 mg / L, the calcium ion concentration can still be reduced to 18.59 ± 3.27 mg / L after treatment with MIP using this process, and the subsequent resin adsorption unit still maintains an extremely high uranium adsorption rate. This fully demonstrates that the process of this invention can still maintain stable and reliable operation under high calcium load conditions.

[0095] Therefore, this invention employs the aforementioned method and system for uranium mining using a phased CO2-controlled MIP (Micro-Induced Polymerization) leaching approach. This phased CO2 control strategy achieves efficient calcium removal and bicarbonate regeneration. The method of this invention demonstrates systematic advantages in improving uranium recovery rate, reducing scaling risk, replacing exogenous carbonates, achieving safe tailings reinjection, and recycling CO2, providing reliable technical support for green and efficient uranium mining.

[0096] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the technical solutions of the present invention, and these modifications or equivalent substitutions cannot cause the modified technical solutions to deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for uranium extraction using a phased CO2-controlled MIP-coordinated leaching process, characterized in that, Includes the following steps: S1. The leaching solution is subjected to depressurization treatment to reduce its pressure to 0.1-0.15 MPa; S2. The leaching extract after the decompression treatment in S1 is introduced into the MICP pre-reactor and inoculated with the first microbial inoculum to remove calcium ions from the liquid. S3. The liquid treated by S2 is passed through a resin adsorption tower to adsorb and recover uranium. S4. The tail liquid after uranium extraction by adsorption in S3 is introduced into the MICP post-reactor and inoculated with a second microbial culture to regenerate bicarbonate. S5. The tailings after S4 are pre-filtered, sterilized and micro-filtered in sequence to obtain reinjection fluid that meets the reinjection standards. S6. A mixed gas containing CO2 and O2 is introduced into the reinjection fluid treated in S5, its pH value is adjusted and pressurized, and then reinjected into the uranium ore layer; wherein, the partial pressure of CO2 in the reinjection fluid is controlled to be 0.3-0.5 MPa; In S2, the effective microbial species in the first microbial culture solution is Bacillus pasteurellii, and the inoculation amount of the first microbial culture solution is 4%-8%; In S2, the reaction occurs at a pH of 9.0-10.0, a temperature of 20-35℃, and a time of 1-3 hours. In S4, the effective microbial species in the second microbial culture solution is Bacillus pasteurellii, and the inoculation amount of the second microbial culture solution is 4%-8%; In S4, the reaction is carried out at a pH of 9.0-10.0, a temperature of 20-35℃, and a time of 0.5-2h. In S5, the pore size of the pre-filter is 45-55 micrometers; the pore size of the microfilter is 0.12-0.32 micrometers. In S5, the sterilization process is ultraviolet sterilization, with an irradiation time of 20-30 minutes. After the sterilization process, the total number of colonies in the reinjection solution does not exceed 10 CFU / mL.

2. The CO2-stage controlled MIP-coordinated uranium leaching method according to claim 1, characterized in that, In S1, pressure reduction is achieved through a stepped pressure relief device, which includes multiple pressure relief tanks connected in series.

3. The CO2-stage controlled MIP-coordinated uranium leaching method according to claim 1, characterized in that, In S3, the flow rate of the liquid through the resin adsorption tower is 2-3 BV / h; the uranium concentration in the tail liquid after adsorption is completed is not higher than 0.5 mg / L.

4. The CO2-stage controlled MIP-coordinated uranium leaching method according to claim 1, characterized in that, In S6, the pH of the reinjection fluid is adjusted to 6.5-7.5 by introducing a mixture of CO2 and O2 gas.

5. A CO2-stage controlled MIP-coordinated uranium leaching system, used to implement the CO2-stage controlled MIP-coordinated uranium leaching method according to any one of claims 1-4, characterized in that, It includes a leachate depressurization device, a MICP pre-reactor, a resin adsorption tower, a MICP post-reactor, a tail liquid treatment unit, and a pressurized reinjection unit, all connected in sequence.

6. The CO2-stage controlled MIP-coordinated uranium leaching system according to claim 5, characterized in that, The MICP pre-reactor and MICP post-reactor are equipped with urease activity monitoring probes, which are linked to the microbial culture replenishment system.

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