Carbonate precipitation method for co-precipitation of uranium tailings consolidation and nuclide fixation and application thereof

Abstract

The application discloses a carbonate precipitation uranium tailings reinforcement and nuclide fixation co-precipitation method and application thereof, and belongs to the technical field of uranium tailing pond treatment. The method comprises the following steps: screening, identifying and domesticating a uranium tailings indigenous urea-decomposing strain HK-1 (Sporosarcina sp.), and optimizing the culture conditions of the strain by a response surface method; mixing high-activity bacterial liquid, a coagulation control agent, a calcium source and urea to construct a synergistic mineralization system; injecting the mineralization system into compacted uranium tailings by a permeation grouting method; and realizing the reinforcement of the uranium tailings and the co-precipitation fixation of uranium by constant-temperature and constant-humidity curing. The application significantly enhances the mechanical strength of the uranium tailings and the stability of nuclide fixation by improving the utilization rate of the calcium source and controlling the calcium carbonate crystal form by using the coagulation control agent. Under the optimal conditions, the compressive strength of the uranium tailings reinforced body can reach 1.986 MPa, the uranium removal rate can reach 84.3%, and the TCLP leaching rate is the lowest at 8.55%, so that the synergistic treatment of mechanical reinforcement and nuclide retardation is realized.

Description

Technical Field

[0001] This invention belongs to the field of uranium tailings dam management technology, specifically relating to a method for co-precipitation of uranium tailings reinforced by carbonate precipitation and radionuclide fixation, and its application. Background Technology

[0002] Uranium tailings ponds are a major source of radioactive pollution generated during uranium mining and processing. The uranium tailings deposited in these ponds not only have poor mechanical stability, making them prone to geological disasters such as landslides and dust storms, but also contain radioactive nuclides such as uranium that can easily migrate with rainwater, posing long-term and serious environmental and health risks to the surrounding soil, groundwater, and ecosystems. Currently, the remediation of uranium tailings requires simultaneously addressing two major challenges: mechanical reinforcement and nuclide containment. Traditional physical covering and chemical stabilization methods often suffer from limitations such as high costs, susceptibility to secondary pollution, or poor long-term effectiveness.

[0003] Microbial-induced carbonate precipitation, as an environmentally friendly biomineralization method, promotes calcium carbonate precipitation through microbial metabolites and has shown potential in the fields of soil and rock reinforcement and heavy metal ion fixation. However, when this technology is directly applied to uranium tailings with complex composition and harsh environment, problems such as low calcium source utilization efficiency, insufficient amount of calcium carbonate precipitate generated, limited uranium fixation capacity, and poor stability of solidification products are common, resulting in insignificant improvement in reinforcement strength and easy secondary dissolution of nuclides.

[0004] Existing studies have attempted to improve the MICP process by optimizing strain culture conditions and adjusting reactant ratios. However, these improvements mostly focus on enhancing single performance aspects and have failed to fundamentally and synergistically improve calcium source conversion efficiency, precipitation crystallinity, and nuclide immobilization stability. Furthermore, conventional commercially available engineered strains have poor adaptability to the high-radiation, low-nutrient environment of uranium tailings, making it difficult to maintain efficient and sustained mineralization activity, thus limiting the field application effectiveness of this technology.

[0005] Therefore, developing an improved MICP technology that can simultaneously enhance the mechanical properties of uranium tailings and achieve long-term nuclide stability has become an urgent need in the field of uranium tailings dam management. A new method is urgently needed that can effectively regulate the mineralization process, improve the environmental adaptability of bacterial strains, and promote the synergistic effect of mechanical reinforcement and nuclide fixation. Summary of the Invention

[0006] This invention provides a method for co-precipitation of uranium tailings with carbonate precipitation and nuclide fixation, and its application. First, a uranium-tolerant indigenous bacterial strain HK-1 is screened and domesticated, and its culture conditions are optimized to obtain a highly active bacterial solution. Then, the bacterial solution is mixed with a coagulation regulator, a calcium source, and urea to construct a synergistic mineralization system. Finally, uranium tailings are injected through a permeation grouting method, and after curing, a solidified body with high strength and low leaching rate is formed. This method significantly improves the utilization rate of the calcium source and the crystallinity of calcium carbonate through coagulation regulation, simultaneously achieving enhanced mechanical properties of uranium tailings and long-term stable fixation of uranium nuclides.

[0007] On the one hand, the present invention provides a method for co-precipitation of uranium tailings reinforced by carbonate precipitation and radionuclide fixation, employing the following technical solution: A method for co-precipitation of uranium tailings reinforced by carbonate precipitation and radionuclide fixation includes the following steps: (1) Screening, identification and domestication of indigenous urea-lysin strains in uranium tailings: Uranium tailings samples were taken from the target uranium tailings pond. The dominant strain was identified by enrichment, screening, purification and 16S rRNA gene sequencing. The uranium-tolerant strain HK-1 was obtained through gradient uranium tolerance acclimatization. (2) Optimization of culture conditions for strain HK-1: The culture conditions of strain HK-1 were optimized using response surface methodology to obtain a highly active bacterial culture. (3) Construction of a synergistic mineralization system with coagulation regulators: The highly active bacterial solution obtained in step (2) is mixed with a coagulation regulator, a calcium source, and urea to construct a coagulation regulator-synergistic mineralization system; the coagulation regulator is selected from one or more of polyvinyl alcohol, soluble starch, sodium citrate, and sodium alginate. (4) Uranium tailings reinforcement and uranium fixation co-precipitation treatment: The uranium tailings were loaded into a mold and compacted. The coagulation-regulating synergistic mineralization system constructed in step (3) was injected into the uranium tailings using the permeation grouting method. After constant temperature and humidity curing, the reinforcement of the uranium tailings and the co-precipitation fixation of uranium were completed.

[0008] Preferably, in step (1), the uranium tailings sample is taken at a depth of 0-0.5 m, and after sampling, impurities are removed and the sample is sieved through a 2 mm sieve; the enrichment medium contains 5 g / L beef extract, 10 g / L peptone, 5 g / L NaCl, and pH 7.3; the solid screening medium contains 1 g / L peptone, 1 g / L glucose, 5 g / L NaCl, 2 g / L KH2PO4, 15 g / L agar, 4 mL / L 0.2% phenol red solution, 20 g / L urea, 2 mg / L uranium concentration, and pH 6.8.

[0009] Preferably, in step (1), the gradient uranium tolerance acclimatization involves inoculating strain HK-1 into an acclimatization medium containing uranium at a concentration of 10 mg / L, culturing for 48 h per round, and completing multiple rounds of acclimatization.

[0010] Preferably, in step (2), the optimal culture conditions are: culture time 18 h, pH 7.9, inoculum size 4%, and culture temperature 30℃; the resulting highly active bacterial solution has a urease activity ≥ 2.5 mmol / L / min and a bacterial solution concentration OD 600 ≥1.6.

[0011] Preferably, in step (3), the mass concentration of the coagulation regulator is: 2% polyvinyl alcohol, 2% soluble starch, 2% sodium citrate, and 0.2% sodium alginate; the calcium source is calcium chloride with a concentration of 0.5 mol / L; and the molar ratio of urea concentration to calcium source concentration is 1:1.

[0012] Preferably, the coagulation regulator is 2% polyvinyl alcohol.

[0013] Preferably, in step (4), the dry density of the compacted uranium tailings is 1.6~1.8 g / cm³. 3 The grouting time for infiltration grouting is 30-60 minutes, and the injection volume is 10 mL of bacterial solution and 40 mL of cementing solution per sample. The curing conditions are: temperature 30℃, relative humidity 80%, and time 14 days.

[0014] On the other hand, the present invention also provides an application of a co-precipitation method for uranium tailings reinforcement with carbonate precipitation and nuclide fixation in the management of uranium tailings ponds.

[0015] This invention also provides a uranium tailings solidification method, which adopts the following technical solution: A uranium tailings solid, prepared by the above method, has a compressive strength ≥1.986 MPa and a TCLP leaching rate of uranium ≤8.55%.

[0016] In summary, the beneficial effects of the present invention are as follows: This invention provides a method for co-precipitating uranium tailings with carbonate precipitation and radionuclide fixation, and its application. By screening and acclimatizing the native uranium-tolerant strain HK-1 for uranium tailings, the adaptability and mineralization activity of the microorganisms under harsh environments are significantly enhanced. Optimizing culture conditions using response surface methodology simultaneously improves the strain's urease activity and uranium tolerance, laying a foundation for efficient mineralization. Simultaneously, an innovative coagulation regulator (such as polyvinyl alcohol) is introduced to control the crystallization process and crystal composition of calcium carbonate precipitation, significantly improving calcium source utilization efficiency and precipitation yield, thereby enhancing the mineralization effect at the source.

[0017] This method ultimately achieves a highly efficient synergy between mechanical reinforcement and nuclide fixation of uranium tailings. On the one hand, coagulation regulation promotes the formation of highly crystalline, stable calcite-type calcium carbonate, significantly improving the compressive and shear strength of the solidified body. On the other hand, through a dual mechanism of co-precipitation and surface adsorption, uranium is stably fixed in the calcium carbonate lattice or encapsulation layer, greatly reducing its exchangeable state ratio and leaching toxicity, effectively blocking nuclide migration, and providing a reliable technical approach for the long-term and green remediation of uranium tailings ponds. Attached Figure Description

[0018] Figure 1 SEM image of strain HK-1; Figure 2A graph showing the bacterial tolerance to uranium; Figure 3 Image A in the image is a SEM image of the sediment induced by unacclimated conventional culture. Figure 3 Image B in the image is a SEM image of the precipitation induced by culture of undomesticated uranium. Figure 3 The image in C is a SEM image of the precipitation induced by uranium culture. Figure 4 This represents the change in calcium ion concentration within the mineralization system. Figure 5 The compressive strength of the reinforced uranium tailings sample; Figure 6 The shear strength parameters of the reinforced uranium tailings sample; Figure 7 This is a SEM image of a typical solidified object. Figure 8 SEM morphology of polyvinyl alcohol co-addition solids; Figure 9 SEM image of sodium citrate. Figure 10 SEM image of sodium alginate. Figure 11 SEM image of the effect of soluble starch; Figure 12 In Figure A, the XRD pattern of the solidified material without a coagulation regulator is shown. Figure 12 Image B is the XRD pattern of 2% polyvinyl alcohol with MICP solidification. Figure 13 In diagram A, the XRD full spectrum comparison of solidification by different coagulation regulators is shown. Figure 13 Image B is a magnified comparison of the characteristic peaks of the calcite crystal plane. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to the embodiments.

[0020] Example Example 1 The specific steps for screening, identifying, and acclimatizing indigenous urea-lysing strains from uranium tailings are as follows: S1. Take uranium tailings samples from a uranium tailings pond at a depth of 0-0.5 m, remove impurities, pass through a 2 mm sieve, weigh 10 g of tailings sample and add it to 100 mL of enrichment medium, and incubate at 30℃ and 150 r / min for 72 h with shaking. The enrichment medium consists of: 5 g / L beef extract, 10 g / L peptone, 5 g / L NaCl, and deionized water, with the pH adjusted to 7.3.

[0021] S2. The enriched bacterial solution was serially diluted to 10-6 times. 0.1 mL of the diluted solution was inoculated into a solid selection medium (1 g / L peptone, 1 g / L glucose, 5 g / L NaCl, 2 g / L KH2PO4, 15 g / L agar, 4 mL / L 0.2% phenol red solution, 20 g / L urea, 2 mg / L uranium concentration, pH adjusted to 6.8). The medium was incubated at 30℃ for 48 h. Single colonies that were red, large in diameter and smooth in surface were selected. The dominant strain was obtained by 7 streak plate purifications.

[0022] S3. Observation using a scanning electron microscope revealed that the strain is rod-shaped, with a single strain length of approximately 1.69 μm. Genomic DNA was extracted from the strain, and 16S rRNA gene sequencing was performed. The sequencing results showed the highest sequence similarity to *Bacillus* genus in GenBank, and the strain was named HK-1. Its scanning electron microscope image is shown below. Figure 1 As shown.

[0023] S4. Strain HK-1 was inoculated into an acclimatization medium containing 10 mg / L uranium. Each round of culture lasted 48 hours. After seven rounds of acclimatization, the strain could still grow normally at a uranium concentration of 2 mg / L, and the uranium removal rate was increased by 42% compared with that before acclimatization.

[0024] like Figure 2 As shown, after multiple rounds of gradient uranium tolerance acclimation, the uranium removal rate of strain HK-1 in the uranium-containing environment increased significantly by 42% compared with that before acclimation. This indicates that the acclimation process effectively enhanced the survival ability and metabolic activity of the strain under uranium stress, laying the foundation for its efficient and stable performance in inducing precipitation and radionuclide fixation in the subsequent mineralization system.

[0025] Example 2 The optimization of culture conditions for strain HK-1 was carried out through the following steps: A Box-Behnken response surface methodology was used, with incubation time (17–19 h), pH (7.5–8.5), inoculum size (3%–5%), and incubation temperature (25–35 °C) as independent variables and uranium removal rate and mineralization rate as response values. The specific parameters are shown in Table 1.

[0026] Table 1. Response Surface Design Factors and Levels

[0027] The optimal culture conditions were determined by Design-Expert software analysis: culture time 18 h, pH 7.9, inoculum size 4%, and culture temperature 30℃. Under these conditions, the bacterial culture had a urease activity ≥2.5 mmol / L / min, a bacterial concentration OD600 ≥1.6, a uranium removal rate of 44.03%, and a mineralization rate of 58.68%.

[0028] like Figure 3 As shown, SEM morphology comparison visually demonstrates the decisive influence of uranium stress acclimatization on the microstructure of MIP-induced calcium carbonate precipitates: Figure 3 A represents the irregular, blocky aggregates formed by undomesticated bacteria under normal culture conditions; Figure 3 B represents the precipitate formed under uranium-containing culture conditions. The precipitate is mainly composed of irregular rhomboid and elliptical aggregates with a thin layer of calcium carbonate on the surface. Figure 3 The precipitate induced by the uranium-tolerant strain HK-1 in strain C consists of large square and rhomboid particles and regular polygonal structures, with smooth crystal surfaces and tight cementation. This result indicates that acclimation effectively enhances the strain's uranium tolerance, enabling it to induce the formation of calcium carbonate with a stable calcite crystal form, providing a key microstructural basis for subsequent efficient mechanical hardening and stable uranium fixation.

[0029] Example 3 The specific steps for constructing a synergistic mineralization system using coagulation regulators are as follows: Take 100 mL of the highly active bacterial solution obtained in Example 2, add a certain amount of polyvinyl alcohol (concentration range (ordinary group) 0%-2%), 55 g / L anhydrous calcium chloride (final concentration 0.5 mol / L), and 30 g / L urea (molar ratio with calcium source 1:1) to dissolve and stir. Mix the two in a 1:4 ratio, stir evenly, and let stand for 10 min to obtain a coagulation-regulating synergistic mineralization system.

[0030] Polyvinyl alcohol has a deposition effect on the concentration of calcium ions in the system as follows: Figure 4 As shown, its deposition pattern was most similar to that of the control group, with relatively low deposition in the early stage and gradually increasing in the later stage. Since its calcium ion coagulation mechanism mainly accelerates calcium deposition by increasing bacterial nucleation sites, polyvinyl alcohol has a significant advantage in terms of mineralization stability and structural integrity. After 168 h of reaction, the calcium ion retention under the synergistic effect of different polyvinyl alcohol concentrations were 0.34 mol / L, 0.26 mol / L, and 0.19 mol / L, respectively, which improved the deposition effect by 19%, 38.1%, and 54.8% compared with the control group.

[0031] Example 4 The specific steps for uranium tailings reinforcement and uranium co-precipitation treatment are as follows: S1. Load the uranium tailings into a mold measuring 39.1 mm × 80 mm, and compact them in layers until the dry density is 1.7 g / cm³. 3 .

[0032] S2. Place the mold at room temperature for 24 hours to stabilize. Then, inject the coagulation-regulating and synergistic mineralization system liquid in batches. The injection volume is 10 mL of bacterial solution and 40 mL of cementing solution, and ensure that the mineralization system penetrates evenly.

[0033] S3. Remove the mold and place it in a constant temperature and humidity chamber at 30℃ and 80% relative humidity for 14 days to complete the treatment.

[0034] Example 5 The synergistic effects of different coagulant regulators were compared using the same steps as in Examples 1-4. The only difference was that in Example 3, sodium citrate, sodium alginate, and soluble starch were selected as coagulant regulators, with their addition concentrations controlled at 2%, 0.2%, and 2%, respectively. Other conditions remained unchanged, and the mineralization precipitation rate, uranium removal rate, and solidification performance under different coagulant regulators were tested.

[0035] Table 2 shows the synergistic reinforcement effects of different coagulation regulators (2% sodium citrate, 0.2% sodium alginate, 2% soluble starch, and 2% polyvinyl alcohol) and a control group without coagulation regulators. Data shows that all coagulation regulators significantly improved uranium removal rate (83.3%-84.8%) and compressive strength (0.971-1.986 MPa), and reduced TCLP leaching rate (8.55%-13.55%). Among them, 2% polyvinyl alcohol achieved the best overall performance while maintaining a high uranium removal rate (84.3%), the optimal compressive strength (1.986 MPa), and the lowest leaching rate (8.55%). The control group without coagulation regulators showed significantly lower values ​​in all indicators, demonstrating the crucial role of coagulation regulators in improving the synergistic reinforcement and fixation effect of MIPs.

[0036] Table 2. Relevant characteristics of added solids in each experimental group

[0037] Test case Test Example 1 The performance of the uranium tailings solidified material after the treatment in Example 4 was tested. The compressive strength was tested using an unconfined pressure gauge (model TKA-WXY-1F), and the shear strength was tested using a strain-controlled triaxial apparatus (model TKA-TTS-3).

[0038] like Figure 5 As shown, under the synergistic effect of polyvinyl alcohol, the compressive strength of uranium tailings samples increases with the increase of synergistic concentration. The results show that the compressive strength of the sample at 2% concentration reaches 1.986 MPa, which is 67.7% higher than that of the ordinary reinforcement group. Compared with the same group, the strength of the high concentration increases by 0.788 MPa compared with the low concentration. The good biocompatibility of polyvinyl alcohol is of great help to promote the improvement of the strength and stiffness of the solidified uranium tailings.

[0039] Regarding the shear strength of the solidified specimen, such as Figure 6As shown, compared with the shear parameters of the unreinforced specimens, the shear strength of the uranium tailings specimens reinforced with MIP was significantly improved. The cohesion of the conventionally reinforced group was 4.79 times higher than that of the unreinforced specimens, and the internal friction angle was 1.58 times higher. The cohesion and internal friction angle of the reinforced specimens with 2% polyvinyl alcohol reached a maximum of 142.127 kPa and 59.089°, respectively. The cohesion was 5.8 times higher than that of the conventionally reinforced and unreinforced specimens, respectively, and the internal friction angle was also improved, increasing by 1.2 times and 18.2 times, respectively. This indicates that the distribution of CaCO3 precipitation inside the uranium tailings was more uniform under the synergistic effect of polyvinyl alcohol, and the cementation and mineralization performance between the precipitation and the uranium tailings particles was better.

[0040] Test Example 2 The occurrence morphology of uranium in the solidified sample of Example 4 was detected by a continuous stepwise chemical extraction method. The morphology and structure of the CaCO3 precipitate in Examples 4 and 5 were characterized by scanning electron microscopy. The crystal composition of calcium carbonate in Examples 4 and 5 was identified and quantified by X-ray diffraction. The results are as follows: Compared to unreinforced samples, the proportion of exchangeable uranium decreased by 20.54%–28.96% in all reinforced samples, while the proportion of carbonate-bound uranium increased by 18.18%–23.11%. The proportion decreased to 8.52% in samples reinforced with 2% polyvinyl alcohol (PVA). The TCLP toxicity characteristic leaching method was used to determine the migration rate of uranium before and after reinforcement. The lowest leaching rate (8.55%) was achieved with 2% PVA, representing a 67.9% and 45.5% improvement in uranium stability compared to unreinforced and conventional reinforcement, respectively.

[0041] Example 4: The morphology and structure of CaCO3 precipitates varied considerably among the different experimental groups. The microscopic morphology results are as follows: Figure 7 , 8 As shown, under ordinary reinforcement, CaCO3 mainly presents as small, round or irregular particles and aggregates, and the precipitate does not completely encapsulate the uranium tailings particles. With the synergistic effect of 2% polyvinyl alcohol, the reinforced structure has good overall integrity, and the CaCO3 precipitate mainly presents as square or stepped cemented aggregates. The precipitate structure layer is thicker and effectively encapsulates and covers the uranium tailings particles. Morphologically, the crystals are mainly calcite, and the cementation stability between particles is better than that of spherical aggregates. There are also certain pores on the surface of the structure.

[0042] Example 5: SEM images of the solidified body under the synergistic reinforcement of various coagulation regulators. Figure 9 , 10As shown in Figures 11 and 2, the microstructure of the mineralized products regulated by 2% sodium citrate is mostly spherical, with a simple interconnection mode. The precipitate structure is relatively dense, without destructive pores or penetrating cracks. The cemented precipitate regulated by 0.2% sodium alginate mainly exhibits independently aggregated calcite-type calcium carbonate crystals with a rough surface structure, but poor cementation between calcite crystals. The combined morphology is similar to that under the synergistic effect of sodium citrate. The microstructure of the cemented mineralized products regulated by 2% soluble starch is a rough-surfaced, spherical and dumbbell-shaped aggregate, mainly composed of irregular square structures tightly cemented together. Some small round particles are attached between the square protruding pores, resulting in a large specific surface area.

[0043] Figure 12 XRD pattern comparison visually demonstrates the crucial role of coagulation regulators in controlling the crystal form of calcium carbonate: Figure 12 A shows that in ordinary MIP solids without coagulation regulators, the calcite characteristic peaks are weak, and the crystal form is mainly aragonite, which has poor stability; while Figure 12 Figure B shows that, with the synergistic effect of 2% polyvinyl alcohol, the characteristic peaks of calcite are significantly enhanced, indicating a substantial increase in its crystal form ratio. This crystal form transformation explains, from a crystal structure perspective, the intrinsic reason why the polyvinyl alcohol synergistic group has the best mechanical strength (1.986 MPa) and the lowest leaching rate (8.55%), as the thermodynamically stable calcite crystal form provides a stronger cementation and a more stable nuclide fixation environment.

[0044] Figure 13 By comparing the XRD full spectrum and characteristic peaks, the effects of different coagulation regulators on the crystal structure of calcium carbonate were systematically demonstrated: Figure 13 The XRD full spectrum comparison of A shows that all coagulation regulator groups (sodium citrate, sodium alginate, soluble starch, and polyvinyl alcohol) showed characteristic diffraction peaks of calcium carbonate at specific positions, but the peak shapes and intensities differed. Figure 13 B focuses on the magnified image of the main characteristic peak of calcite (104 crystal plane), which further reveals that the calcite characteristic peak of the 2% polyvinyl alcohol and 2% soluble starch group has the highest intensity and the sharpest peak shape. This indicates that these two regulators can most effectively induce the formation of a stable calcite crystal with high crystallinity. This is directly related to its excellent compressive strength and low leaching rate in macroscopic properties (Table 2). From a crystallographic perspective, this proves that coagulation regulation is the core mechanism for improving the synergistic reinforcement and uranium fixation stability of MIP.

[0045] The above are all preferred embodiments of the present invention and are not intended to limit the scope of protection of the present invention. Therefore, all equivalent changes made in accordance with the structure, shape and principle of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A method for co-precipitation of uranium tailings reinforced by carbonate precipitation and radionuclide fixation, characterized in that, Includes the following steps: (1) Screening, identification and domestication of indigenous urea-lysin strains in uranium tailings: Uranium tailings samples were taken from the target uranium tailings pond. The dominant strain was identified by enrichment, screening, purification and 16S rRNA gene sequencing. The uranium-tolerant strain HK-1 was obtained through gradient uranium tolerance acclimatization. (2) Optimization of culture conditions for strain HK-1: The culture conditions of strain HK-1 were optimized using response surface methodology to obtain a highly active bacterial culture. (3) Construction of a synergistic mineralization system with coagulation regulators: The highly active bacterial solution obtained in step (2) is mixed with a coagulation regulator, a calcium source, and urea to construct a coagulation regulator-synergistic mineralization system; the coagulation regulator is selected from one or more of polyvinyl alcohol, soluble starch, sodium citrate, and sodium alginate. (4) Uranium tailings reinforcement and uranium fixation co-precipitation treatment: The uranium tailings were loaded into a mold and compacted. The coagulation-regulating synergistic mineralization system constructed in step (3) was injected into the uranium tailings using the permeation grouting method. After constant temperature and humidity curing, the reinforcement of the uranium tailings and the co-precipitation fixation of uranium were completed.

2. The method for co-precipitation of uranium tailings reinforced by carbonate precipitation and radionuclide fixation according to claim 1, characterized in that, In step (1), the uranium tailings sample is taken at a depth of 0-0.5 m, and after sampling, impurities are removed and the sample is sieved through a 2 mm sieve. The enrichment medium contains 5 g / L beef extract, 10 g / L peptone, 5 g / L NaCl, and pH 7.

3. The solid screening medium contains 1 g / L peptone, 1 g / L glucose, 5 g / L NaCl, 2 g / L KH2PO4, 15 g / L agar, 4 mL / L 0.2% phenol red solution, 20 g / L urea, 2 mg / L uranium concentration, and pH 6.

8.

3. The method according to claim 1, characterized in that, In step (1), the gradient uranium tolerance acclimatization involves inoculating strain HK-1 into an acclimatization medium containing uranium at a concentration of 10 mg / L, culturing for 48 hours per round, and completing the acclimatization process through multiple rounds.

4. The method according to claim 1, characterized in that, In step (2), the optimal culture conditions are: culture time 18 h, pH 7.9, inoculum size 4%, and culture temperature 30℃; the urease activity of the obtained highly active bacterial solution is ≥2.5 mmol / L / min, and the bacterial solution concentration OD 600 ≥1.

6.

5. The method according to claim 1, characterized in that, In step (3), the mass concentration of the coagulation regulator is: 2% polyvinyl alcohol, 2% soluble starch, 2% sodium citrate, and 0.2% sodium alginate; the calcium source is calcium chloride with a concentration of 0.5 mol / L; and the molar ratio of urea concentration to calcium source concentration is 1:

1.

6. The method according to claim 5, characterized in that, The coagulation regulator is 2% polyvinyl alcohol.

7. The method according to claim 1, characterized in that, In step (4), the dry density of the compacted uranium tailings is 1.6~1.8 g / cm³; the grouting time for the infiltration grouting is 30~60 min, and the injection volume is 10 mL of bacterial solution and 40 mL of cementing solution per sample; the curing conditions are: temperature 30℃, relative humidity 80%, and time 14 days.

8. The application of the method as described in any one of claims 1-7 in the management of uranium tailings ponds.

9. A solidified form of uranium tailings, characterized in that, Prepared by the method described in any one of claims 1-7, the compressive strength is ≥1.986 MPa and the TCLP leaching rate of uranium is ≤8.55%.

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