Method for regulating klebsiella to induce calcium carbonate precipitation to solidify uranium tailings by using xanthan gum

Abstract

The invention discloses a method for regulating Klebsiella to induce calcium carbonate precipitation to solidify uranium tailings by using xanthan gum, which comprises the following steps: 1) respectively and uniformly mixing xanthan gum with the mass of M gum and 1 / 2 M gum into uranium tailings to be reinforced to obtain a full / half sand-doped gum mixture; (2) inoculating the activated klebsiella into a liquid culture medium, and culturing to obtain a bacterium suspension for curing; (3) preparing a calcium acetate solution to obtain a fully-doped cementing solution for curing; weighing xanthan gum of which the mass is 1 / 2 M gum, equally dividing the xanthan gum into 14 equal parts, and dissolving the xanthan gum into a calcium acetate solution to obtain a semi-doping method cementing solution for curing; 4, the bacterial suspension and the corresponding full / semi-doped cementing fluid are injected into the full / semi-doped sand glue mixture to be reinforced, grouting is conducted 7 / 14 times, and the solidified uranium tailings are obtained.By means of the method, the mechanical strength, deformation resistance and integrity of a solidified body are remarkably improved, and performance emergence and directional optimization of the solidified body are promoted.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of sand reinforcement and tailings sand treatment, and particularly relates to a method for solidifying uranium tailings sand by inducing calcium carbonate precipitation of Klebsiella bacteria using xanthan gum. BACKGROUND

[0002] Uranium tailings are solid wastes produced after uranium mining and smelting processing, which have the characteristics of complex composition, large stock volume, small particle size, poor structural stability, and rich in radioactive nuclides and associated heavy metal elements. The uranium tailings dam formed by its accumulation is extremely easy to liquefy and destabilize under external disturbance, thereby causing serious threats to the downstream social economy and ecological system. Therefore, effective reinforcement measures are needed to improve the mechanical properties and structural stability of the uranium tailings dam to ensure its long-term safe and stable operation.

[0003] Traditional reinforcement methods such as cement grouting and chemical curing can improve soil stability and enhance its mechanical properties, but they still suffer from poor weather resistance, low environmental compatibility, and high curing costs. Furthermore, the highly alkaline (pH>12) curing process may lead to expansion and cracking of the solidified body in the later stages. In recent years, microbially induced carbonate precipitation (MICP) technology has attracted considerable attention as a novel reinforcement technique due to its environmental friendliness, cost-effectiveness, and compatibility of mineralized products with natural geological structures. MICP technology produces calcium carbonate precipitates through microbial mineralization. These precipitates, with certain cementing properties, adhere to the surface of soil particles or fill the interparticle spaces, thereby improving the mechanical strength and stability of the solidified body. However, existing MIP (Microbial Microbial Concentration Program) technology still has certain shortcomings in soil solidification: 1) Urease-producing bacteria are widely used as carbonate mineralizing bacteria, and their metabolic byproducts (such as ammonia and ammonium ions) during the microbial mineralization process pose potential risks to the environment; 2) Solidified bodies reinforced by MIP alone have limited overall mechanical strength and deformation resistance, making it difficult to meet engineering requirements; 3) The macroscopic mechanical properties of solidified bodies are closely related to the amount, crystal form, morphology, and particle size of calcium carbonate precipitates, but the microorganisms themselves have limited ability to regulate precipitation characteristics during the mineralization process, affecting the macroscopic mechanical properties of the solidified bodies. To overcome these limitations, admixtures are currently commonly used in conjunction with MIP technology for soil solidification. However, the characteristics of microorganisms and admixtures are relatively independent, and their correlation is weak. This results in the improvement of the mechanical properties of the solidified body being merely a simple superposition of different material properties, without forming an effective coupling mechanism. Therefore, the microbial mineralization process and precipitation characteristics are difficult to effectively control and optimize. At the same time, this uncoupled combination is prone to forming structural defects within the solidified body, affecting the homogeneity and long-term stability of the material. Furthermore, some additives pose environmental risks, limiting their application. Therefore, it is necessary to select a novel MIP solidification method that is simple in process, environmentally friendly, widely applicable, and can effectively overcome the aforementioned limitations, in order to achieve green and efficient solidification of uranium tailings. Summary of the Invention

[0004] The technical problem to be solved by this invention is to provide a method for regulating Klebsiella pneumoniae-induced calcium carbonate precipitation and solidification of uranium tailings. Due to the similarity of physical properties and chemical composition between xanthan gum and Klebsiella pneumoniae extracellular polysaccharides, this method uses xanthan gum as a functional substitute for Klebsiella pneumoniae extracellular polysaccharides, coupled with the regulatory effect of xanthan gum on Klebsiella pneumoniae-induced calcium carbonate precipitation, optimizes the dosage of xanthan gum and solidification process parameters, and thus directionally regulates the mineralization precipitation process and precipitation characteristics, significantly improving the mechanical strength, toughness and integrity of uranium tailings, and ultimately achieving emergent and directional optimization of the mechanical properties of uranium tailings. This method is simple, environmentally friendly and widely applicable.

[0005] This invention provides a method for regulating Klebsiella pneumoniae to induce calcium carbonate precipitation and solidify uranium tailings, comprising the following steps: (1) Calculate the total mass M of the uranium tailings to be reinforced based on the area and depth of the area to be reinforced and the physical properties of the uranium tailings. 砂 and total pore volume V 孔 ; with mass M 胶 Xanthan gum is uniformly mixed into the uranium tailings to be reinforced to obtain a fully mixed sand-based adhesive mixture; or 1 / 2 M by mass is mixed with xanthan gum. 胶 Xanthan gum was uniformly mixed into the uranium tailings to be reinforced to obtain a semi-sand-gum mixture; (2) Inoculate the activated Klebsiella pneumoniae into a liquid culture medium and culture it under certain conditions to obtain a bacterial suspension in the mid-to-late logarithmic phase. Adjust the pH of the bacterial suspension to 9-10 to obtain a bacterial suspension for solidification. (3) Prepare a calcium acetate solution of a certain concentration, adjust the pH value to 9-10, and obtain the fully doped cementitious solution; weigh 1 / 2M 胶 Xanthan gum was divided into 14 equal parts and dissolved in a calcium acetate solution of a certain concentration. The pH value was adjusted to 9-10 to obtain a semi-doped cementitious solution. (4) Solidification is carried out by in-situ infiltration grouting method. The bacterial suspension in step (2) and the fully doped cementing liquid in step (3) are injected sequentially into the fully doped sand-cement mixture in step (1). The bacterial suspension and the fully doped cementing liquid are injected in a total of 7 rounds to obtain solidified uranium tailings. Alternatively, solidification is carried out by in-situ infiltration grouting method. The bacterial suspension in step (2) and the semi-doped cementing liquid in step (3) are injected sequentially into the semi-doped sand-cement mixture in step (1). The bacterial suspension and the semi-doped cementing liquid are injected in a total of 14 rounds to obtain solidified uranium tailings.

[0006] In the method for solidifying uranium tailings, the mass is M. 胶 Xanthan gum and uranium tailings were mixed evenly to obtain a fully-doped sand-cement mixture. During grouting, a fully-doped cementitious solution without xanthan gum was used; this is a single-phase fully-doped curing method. The mass was 1 / 2 M. 胶 Xanthan gum and uranium tailings were mixed evenly to obtain a semi-doped sand-glue mixture. During grouting, a semi-doped cementing solution containing xanthan gum was used; this is a two-phase semi-doped curing method. In both curing methods, the mass of the uranium tailings to be reinforced and the total amount of xanthan gum added are the same.

[0007] The Klebsiella pneumoniae used in the method for solidifying uranium tailings is a mineralizing microorganism that can directly induce the formation of calcium carbonate by decomposing calcium acetate in an aerobic environment. Its metabolic byproducts are only CO2 and H2O, both of which are present in the aqueous phase and will not pose a risk to the environment.

[0008] The Klebsiella pneumoniae deposited at the China Center for Type Culture Collection, located at No. 299 Bayi Road, Wuchang District, Wuhan, Hubei Province (opposite to the First Affiliated Primary School of Wuhan University), Wuhan University Collection Center, accession number M20211523, is classified as follows: Klebsiella sp. 11027.

[0009] Xanthan gum, also known as xanthan gum, is an extracellular heteropolysaccharide produced by *Xanthomonas aeruginosa* through fermentation. Its main components are D-glucose, D-mannose, and D-glucuronic acid, in a mass ratio of approximately 2:2:1. It is a high-molecular-weight polysaccharide compound that exhibits similar physical properties and chemical composition to the extracellular polysaccharides of *Klebsiella pneumoniae*, thus serving as a functional substitute for *Klebsiella pneumoniae* extracellular polysaccharides. Large-scale production of xanthan gum involves fermentation of carbohydrates (such as corn starch) using *Xanthomonas aeruginosa* as a raw material.

[0010] Furthermore, the M 胶 The mass is 1.0%–1.4% M 砂 .

[0011] Furthermore, the OD of the bacterial suspension in step (2) 600 The concentration is 5.00–5.15, which contains metabolically active bacteria, extracellular polymers, carbonate and bicarbonate ions.

[0012] Furthermore, in step (2), the pH value of the bacterial solution is adjusted to 10.

[0013] Furthermore, in step (2), the liquid culture medium uses water as a solvent and includes 20 g / L sodium acetate solution and 4 g / L yeast extract; the natural pH of the liquid culture medium is 7.10–7.30.

[0014] Furthermore, the conditions in step (2) are as follows: culture in a constant temperature shaking incubator at a temperature of 30°C, a rotation speed of 100 rpm, and a culture time of 108-132 h.

[0015] Furthermore, the activation of Klebsiella pneumoniae in step (2) is achieved through the following steps: 1) Activation of bacterial strain: Take out the frozen glycerol seed tube from the -80℃ freezer and thaw it at room temperature. Inoculate the obtained glycerol seed solution into liquid culture medium and culture it under certain conditions for 24-36 h to obtain the first generation of activated bacterial solution. 2) Single colony culture: Take 1 ml of activated bacterial solution, spread it on the surface of solid culture medium and incubate it for 24-36 h, and observe the growth status of the colony. 3) Seed suspension preparation: Select single colonies with good growth status from 2) and transfer them to liquid culture medium and culture for 24-36 h to obtain seed suspension for large-scale culture.

[0016] The glycerol seed tube is a strain preservation tube prepared by glycerol cryopreservation. By using low temperature (-80℃) and glycerol to reduce ice crystal damage, the strain can be preserved for a long time (2-10 years).

[0017] Furthermore, the conditions in step 1) are a culture temperature of 30°C and a culture time of 24–36 h.

[0018] Furthermore, in step (3), the concentration of the calcium acetate solution of a certain concentration is 0.50 mol / L.

[0019] Furthermore, in step (4), the volume of bacterial suspension and the volume of cementing liquid injected in each round are both pore volumes V. 孔 0.6 times.

[0020] The beneficial effects of this invention are: 1) The Klebsiella pneumoniae used in this invention can directly induce calcium carbonate formation by decomposing calcium acetate under aerobic conditions. Its metabolic byproducts are only CO2 and H2O, both of which are present in the aqueous phase and pose no risk to the environment; therefore, it is an environmentally friendly MIP mineralizing bacterium. The mineralization mechanism of this bacterium is as follows: Ca(C2H3O2)2+ 4O2 CaCO3↓ + 3CO2(aq) + 3H2O 2) The xanthan gum used in this invention is a water-soluble heteropolysaccharide produced by Xanthomonas oryzae through fermentation. Its unique double helix tertiary structure gives it high viscosity and pseudoplasticity, which can bind loose sand particles into a whole and form initial strength. 3) When using the two-phase semi-doped solidification method to reinforce uranium tailings, part of the xanthan gum is directly mixed into the uranium tailings in the form of dry powder, while the other part is dissolved in the fully doped cementing solution to form a mixed cementing solution. This dry-wet combination method makes full use of the different functions of xanthan gum in the solid and liquid phases and improves the overall utilization rate of xanthan gum.

[0021] 4) In-situ infiltration grouting is employed to fully utilize the fluidity of the bacterial solution and cementing solution, enabling them to migrate and diffuse uniformly within the uranium tailings to be reinforced. This method achieves low-disturbance reinforcement of uranium tailings, ensuring not only the uniformity and controllability of the reinforcement effect but also effectively maintaining the stability of the original structure of the uranium tailings.

[0022] 5) During the curing process, xanthan gum significantly regulated the amount, crystal form, and particle size of Klebsiella pneumoniae-induced calcium carbonate precipitation. Compared with the MIP control group, the amount of calcium carbonate precipitation in the single-phase fully doped curing group and the two-phase semi-doped curing group increased by 194% and 77%, respectively. Single-phase fully doped curing was conducive to calcite formation, while two-phase semi-doped curing was conducive to the balance and stability of polymorphisms. The average particle size of calcium carbonate precipitation was significantly reduced and stabilized at around 4.0 μm. These optimizations in calcium carbonate precipitation characteristics help it to be evenly distributed in uranium tailings, fully filling the pores between sand grains, and improving the density and macroscopic mechanical properties of the tailings.

[0023] 6) The final curing effect of the solidified body is not significantly different when using different mixing methods and grouting cycles. This characteristic gives the uranium tailings solidification process good applicability and operational flexibility, allowing for flexible adjustment of mixing strategies and grouting cycles according to specific site conditions, achieving site-specific reinforcement control. Simultaneously, by combining real-time feedback on the curing effect of each cycle, the dosage of subsequent bacterial solution and cementing solution can be dynamically optimized while ensuring the solidification strength, thereby reducing material consumption and achieving a synergistic improvement in engineering efficiency and economic benefits.

[0024] 7) This invention utilizes xanthan gum to regulate Klebsiella pneumoniae-induced calcium carbonate precipitation, achieving the solidification of uranium tailings and constructing a ternary composite structure of "tailings particles-xanthan gum-calcium carbonate". The solidification mechanism is as follows: Xanthan gum, uniformly dispersed in the tailings, forms a three-dimensional flexible network structure between loose sand particles through bridging and adhesive properties, binding the loose sand particles together and providing initial structural strength and overall support for the system. Simultaneously, xanthan gum, relying on its own properties and regulation of the local microenvironment, controls the microbial mineralization process and precipitation characteristics, leading to a significant increase in calcium carbonate precipitation, a decrease in crystal size, a more regular morphology, and a more stable and balanced proportion of polymorphs. The mineralized calcium carbonate crystals exhibit a dual distribution and function: one part adheres to the surface of the sand particles and bridges adjacent sand particles, filling the pores between particles and reducing the system's porosity; the other part is anchored and adhered to the flexible framework, covering and encapsulating the network structure to form a rigid calcium carbonate cementing layer. Ultimately, the flexible xanthan gum network structure and rigid calcium carbonate particles intercalate to form a stable composite structure. Compared to the traditional "precipitation-cementation-filling" path in single MIP curing technology, this method improves the path by introducing xanthan gum, achieving "three-dimensional flexible network construction-mineralization process and property control-dual-effect cementation-directional filling." The precipitation of calcium carbonate induced by xanthan gum and Klebsiella pneumoniae is not a simple superposition of properties, but rather an improvement in the overall performance of the cured body through functional coupling and synergistic effects, enhancing structural integrity, long-term durability, mechanical load-bearing capacity, and deformation resistance, exhibiting a significant strengthening effect and performance emergence. Attached Figure Description

[0025] Figure 1The particle size distribution curve of uranium tailings; Figure 2 The unconfined compressive strength of cured bodies under different curing methods; Figure 3 Stress-strain curves of cured bodies under different curing methods; Figure 4 The percentage of different crystal forms of calcium carbonate precipitate under different curing methods; Figure 5 The amount and particle size of calcium carbonate precipitation under different curing methods; Figure 6 SEM images of cured bodies under different curing methods; Figure 7 The diagram shows the process flow diagrams for single-phase full-doping curing and two-phase half-doping curing.

[0026] Example 1 A method for solidifying uranium tailings by inducing calcium carbonate precipitation using xanthan gum-regulated Klebsiella pneumoniae is described in this embodiment, which employs a single-phase fully doped solidification method and mainly follows these steps: (1) Treatment of uranium tailings: The uranium tailings retrieved from the uranium tailings pond were dried in an oven at 105±5℃ until constant weight. The particle size distribution was obtained by sieving. Figure 1 Its average particle size (Dav) and effective particle size (D) 10 ) and limiting particle size (D 60 The specific gravity, average porosity, and average porosity of the uranium tailings were measured to be 0.329, 0.148, and 0.395 mm, respectively. The tailings were then tested and found to have a specific gravity of 2.56 and an average porosity of 0.345. (This information is for future reference.)

[0027] (2) Preparation of the sand column to be reinforced: A cylindrical polypropylene resin tube with an inner diameter of 39.1 mm and a height of 120 mm was used as a mold. After filling the sand-resin mixture, 50-mesh gauze and filter cotton were placed on the upper and lower surfaces of the sand column to prevent tailings loss. Stainless steel hose clamps were used for fixation, and the cut was sealed with hot melt adhesive. Weigh 150 g of the uranium tailings treated in step (1) into three portions, and add 1.50 g (1.0%), 1.80 g (1.2%) and 2.10 g (1.4%) of powdered xanthan gum to them respectively. After mixing evenly, the mixture was filled into the mold in three layers to obtain a single-phase fully doped sand column with a diameter of 39.1 mm and a height of 80 mm. Take 150 g of uranium tailings without xanthan gum and prepare sand columns of the same size according to the same process as the MICP control group.

[0028] (3) Preparation of bacterial suspension: a) Culture medium: Using deionized water as solvent, prepare a bacterial suspension containing 20 g / L sodium acetate, 4 g / L yeast extract, and a pH of 7.10-7.30. After sterilization at 121℃ for 20 min, take it out for use; b) Activation of bacterial strain: Take the frozen glycerol tube seed from the -80℃ freezer and thaw it at room temperature. Inoculate the thawed seed into 100 ml of culture medium and place it in a constant temperature shaking incubator at 30℃ and 100 rpm for 24 h; c) Single colony culture: Take 1 ml of the activated bacterial suspension from step b) and spread it on the surface of the solid culture medium and let it stand for 24 h to observe the growth status of the colony; d) Preparation of seed suspension: Select single colonies with good growth status from step c) and transfer them to liquid culture medium. Culture them under optimal conditions for 24 h to obtain the seed suspension for expansion culture; e) Solidification of bacterial suspension: Take the seed suspension from step d) and inoculate (2%, V / V) into the culture medium and culture it under optimal conditions for 120 min. h, to obtain the bacterial culture in the mid-to-late logarithmic phase, at which point the bacterial culture OD... 600 The pH was 5.00–5.15. The pH was adjusted to 10 using 0.50 M NaOH solution to obtain a bacterial suspension for consolidation, which was then set aside.

[0029] (4) Preparation of cementing solution: Using deionized water as solvent and calcium acetate as solute, prepare a calcium acetate solution with a concentration of 0.50 M, and adjust its pH to 10 with 0.50 M NaOH solution to obtain the fully doped cementing solution for later use.

[0030] (5) Sand column solidification: Different groups of sand column samples were solidified by permeation grouting. The total grouting volume in a single injection was 1.2 times the pore volume, i.e., 40 mL. 20 mL of bacterial suspension and 20 mL of cementing liquid were injected sequentially from the top of the sand column. After the injection was completed, the column was left to stand for 24 h before the next round of grouting was carried out. A total of 7 rounds of grouting were performed to finally obtain the solidified sand column of the MICP control group and the single-phase fully mixed group.

[0031] (6) Treatment of cured sand columns: The obtained sand columns were placed in an oven at 60-70℃ and dried for 48 h. The dried sand columns were then removed from the mold to obtain the cured sand columns of the MICP control group and the single-phase fully doped group with different xanthan gum content. (7) Mechanical properties of sand columns: Unconfined compressive strength tests were conducted on each group of sand columns, and their stress-strain curves were recorded. The results are as follows: Figure 2 and 3 As shown, the sand column in the MICP control group could not be formed. When using the single-phase full-doping curing method, its unconfined compressive strength was 1270-1486.7 kPa, and the peak strain was 4.1%-5.9%, exhibiting high compressive strength and resistance to deformation.

[0032] (8) Crystal form ratio of mineralized precipitate: The pulverized sample was characterized by XRD, and the polymorphism in the precipitate was quantitatively calculated using the Rietveld method. The results are as follows: Figure 4 As shown, the contents of calcite and aragonite in the precipitate of the MIP control group were 48.7% and 51.3%, respectively. When using the single-phase full-doping solidification method, the calcite content in the precipitate ranged from 54.4% to 62.6%. This indicates that xanthan gum can regulate and promote the formation of calcite.

[0033] (9) Quality and particle size of mineralized precipitate: The amount of calcium carbonate precipitate was determined by acid immersion method on the pulverized sample, and particle size was statistically analyzed and measured using ImageJ software. The results are as follows: Figure 5 As shown, the precipitation amount in the MIP control group was only 1.06 g / L, with a particle size of 9.40 μm. When using the single-phase full-doping solidification method, the calcium carbonate precipitation amount was 2.90–3.16 g / L, with a particle size of 4.40–5.13 μm. This indicates that the addition of xanthan gum significantly increases the precipitation amount and reduces the particle size, and the higher the xanthan gum dosage, the more significant the regulatory effect.

[0034] (10) Morphology after curing: The pulverized sample was characterized by SEM. The results are as follows: Figure 6 As shown, the original uranium tailings are irregularly angular and sub-circular with sharp edges, and the particles are dispersed without adhesion (A). When solidified using MIP alone, calcium carbonate crystals fill the pores between some particles, while a small number of particles are adhered by bacteria, metabolites, or mineralization products, resulting in relatively large pores between particles (B). When using the single-phase full-doping solidification method (C), xanthan gum forms a network structure between the loose sand particles and binds the loose sand particles into a whole. This network structure can trap and anchor some calcium carbonate precipitates, promoting their directional and uniform filling in the pores, thereby reducing the porosity of the system. At the same time, calcium carbonate crystals adhere to and gradually cover the flexible xanthan gum framework, forming a continuous rigid calcium carbonate cement layer. The solidified body has smaller pores and weaker connectivity, and the overall structure is dense and complete, ultimately forming a ternary intercalated composite structure of "xanthan gum-uranium tailings-calcium carbonate".

[0035] Example 2 A method for solidifying uranium tailings by inducing calcium carbonate precipitation using xanthan gum-regulated Klebsiella pneumoniae is described in this embodiment, which employs a two-phase semi-doped solidification method and mainly follows these steps: (1) Post-solidification sand column treatment: Uranium tailings sand retrieved from the uranium tailings pond surface was dried in an oven at 105±5℃ until constant weight. The particle size distribution was obtained using a sieving method. Figure 1 ), average particle size (Dav), effective particle size (D 10 ) and limiting particle size (D 60The specific gravity, average porosity, and average porosity of the uranium-bearing tailings were measured to be 0.329, 0.148, and 0.395 mm, respectively. (For future reference.)

[0036] (2) Preparation of the sand column to be reinforced: A cylindrical polypropylene resin tube with an inner diameter of 39.1 mm and a height of 120 mm was used as a mold. After filling the sand-resin mixture, 50-mesh gauze and filter cotton were placed on the upper and lower surfaces of the sand column to prevent tailings loss. Stainless steel hose clamps were used for fixation, and the cut was sealed with hot melt adhesive. Weigh 150 g of the uranium tailings treated in step (1) into three portions, and add 0.75 g (0.5%), 0.90 g (0.6%) and 1.05 g (0.7%) of powdered xanthan gum respectively. After mixing evenly, the mixture was filled into the mold in three layers to obtain a biphase semi-doped sand column with a diameter of 39.1 mm and a height of 80 mm. Take 150 g of uranium tailings without xanthan gum and prepare sand columns of the same size according to the same process as the MICP control group.

[0037] (3) Preparation of bacterial suspension: a) Culture medium: Using deionized water as solvent, prepare a bacterial culture medium containing 20 g / L sodium acetate, 4 g / L yeast extract, and natural pH value. After sterilization at 121℃ for 20 min, take it out for use; b) Activation of bacterial strain: Take the frozen glycerol tube seed from the -80℃ freezer and thaw it at room temperature. Inoculate the thawed seed into 100 ml of culture medium and place it in a constant temperature shaking incubator at 30℃ and 100 rpm for 24 h; c) Single colony culture: Take 1 ml of the activated bacterial suspension in step b) and spread it on the surface of the solid culture medium and let it stand for 24 h to observe the growth status of the colony; d) Preparation of seed suspension: Select single colonies with good growth status in step c) and transfer them to liquid culture medium. Incubate them under optimal conditions for 24 h to obtain the seed suspension for expansion culture; e) Solidification of bacterial suspension: Take the seed suspension in step d) and inoculate (2%, V / V) into the culture medium and incubate it under optimal conditions for 120 min. h, to obtain the bacterial culture in the mid-to-late logarithmic phase, at which point the bacterial culture OD... 600 The pH was 5.00–5.15. The pH was adjusted to 10 using 0.50 M NaOH solution to obtain a bacterial suspension for consolidation, which was then set aside.

[0038] (4) Preparation of cementing solution: Using deionized water as solvent and calcium acetate as solute, prepare a 0.50 M calcium acetate solution and adjust its pH to 10 using 0.50 M NaOH solution. Weigh 0.75 g (0.5%), 0.90 g (0.6%) and 1.05 g (0.7%) of powdered xanthan gum, divide them into 14 equal portions, and dissolve them in the calcium acetate solution to obtain a biphasic semi-doped cementing solution for later use.

[0039] (5) Sand column solidification: Different groups of sand column samples were solidified using the permeation grouting method. The total grouting volume in a single injection was 1.2 times the pore volume, i.e., 40 mL. 20 mL of bacterial suspension and 20 mL of cementing solution were injected sequentially from the top of the sand column. After grouting, the column was allowed to stand for 24 h before the next round of grouting was carried out. A total of 14 rounds of grouting were performed to obtain solidified sand columns of the MICP control group and the biphasic semi-doped group, respectively. During the solidification process, the total xanthan gum content was 0.50 g (1.0%), 1.80 g (1.2%), and 2.10 g (1.4%), respectively.

[0040] (6) Treatment of cured sand columns: The obtained sand columns were placed in an oven at 60-70℃ and dried for 48 h. The dried sand columns were removed and demolded to obtain the MICP control group sand columns and the biphasic semi-doped sand columns with different xanthan gum dosages.

[0041] (7) Mechanical properties of sand columns: Unconfined compressive strength tests were conducted on each group of sand columns, and their stress-strain curves were recorded. The results are as follows: Figure 2 and 3 As shown, the peak stress and strain of the sand column in the MIP control group were 88.5 kPa and 2.7%, respectively. When the two-phase semi-doped curing method was used, the unconfined compressive strength was 936-1498 kPa and the peak strain was 4.3%-4.8%, and the compressive strength and deformation resistance were significantly improved.

[0042] (8) Crystal form ratio of mineralized precipitate: The pulverized sample was characterized by XRD, and the polymorphism in the precipitate was quantitatively calculated using the Rietveld method. The results are as follows: Figure 4 The results show that the contents of calcite and aragonite in the precipitate are 72.1% and 27.9%, respectively. When the two-phase semi-doped solidification method is used, the crystal composition in the precipitate changes significantly: the contents of calcite and aragonite are 46.4%–50.7% and 53.6%–49.3%, respectively. This indicates that the contents of calcite and aragonite in the precipitate remain relatively balanced and stable.

[0043] (9) Quality and particle size of mineralized precipitate: The amount of calcium carbonate precipitate was determined by acid immersion method on the pulverized sample, and particle size was statistically analyzed and measured using ImageJ. The results are as follows: Figure 5 As shown, the precipitation amount in the MIP control group was only 1.89 g / L, with a particle size of 10.55 μm. When using the biphasic semi-doped curing method, the calcium carbonate precipitation amount was 2.32–2.97 g / L, with a particle size of 5.90–6.31 μm. This indicates that the addition of xanthan gum can significantly increase the precipitation amount and reduce the particle size.

[0044] (10) Morphology after curing: The pulverized sample was characterized by SEM. The results are as follows: Figure 6As shown, the original uranium tailings are irregularly angular and sub-circular with sharp edges, and the particles are dispersed without adhesion (A). In the MICP control group, calcium carbonate crystals fill the pores between some particles, while a small number of particles are adhered by bacteria, metabolites, or mineralization products, resulting in larger pores between particles (B). When using the two-phase semi-doped solidification method (D), xanthan gum forms a network structure between loose sand particles and binds the loose sand into a whole. This network structure can trap and anchor some calcium carbonate precipitates, promoting their directional and uniform filling in the pores, thereby reducing the system porosity. At the same time, calcium carbonate crystals adhere to and gradually cover the flexible xanthan gum framework, forming a continuous rigid calcium carbonate cement layer. The solidified body has smaller pores and weaker connectivity, and the overall structure is dense and complete, ultimately forming a ternary intercalated composite structure of "xanthan gum-uranium tailings-calcium carbonate".

[0045] The results of Examples 1 and 2 show that when using xanthan gum to regulate Klebsiella pneumoniae-induced calcium carbonate precipitation for solidification of uranium tailings, both the single-phase full doping method and the two-phase half-doping method exhibit significantly better solidification effects than the single MIP solidification method. Specifically, this is manifested in a significant increase in calcium carbonate precipitation, a significant decrease in precipitate particle size, a relatively stable proportion of polymorphic precipitates, and regular and uniform crystal morphology. The regulation and optimization of these microscopic properties significantly improve the overall integrity and macroscopic mechanical strength of the uranium tailings, and performance emergence is achieved through the coupling and synergy of the solidification process.

[0046] Those skilled in the art should understand that the discussion of any of the above embodiments is merely exemplary and is not intended to imply that the scope of protection of this application is limited to these examples; within the framework of this application, the technical features of the above embodiments or different embodiments can also be combined, the steps can be implemented in any order, and there are many other variations of different aspects of one or more embodiments of this application as described above, which are not provided in detail for the sake of brevity.

[0047] One or more embodiments in this application are intended to cover all such substitutions, modifications, and variations that fall within the broad scope of this application. Therefore, any omissions, modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of one or more embodiments in this application should be included within the protection scope of this application.

Claims

1. A method for regulating the precipitation of calcium carbonate induced by Klebsiella oxytoca for solidification of uranium tailings using xanthan gum, characterized by: The method comprises the following steps: (1) According to the area, depth and physical properties of the uranium tailings to be reinforced, the total mass M of the uranium tailings to be reinforced is calculated 砂 And the total pore volume V 孔 ; uniformly mix xanthan gum with a mass of M 胶 In the uranium tailings to be reinforced to obtain a full-sand glue mixture; or uniformly mix xanthan gum with a mass of 1 / 2 M 胶 In the uranium tailings to be reinforced to obtain a half-sand glue mixture; (2) inoculating the activated Klebsiella bacteria into a liquid culture medium, culturing under certain conditions to obtain a bacterial solution in the mid-late logarithmic phase, adjusting the pH value of the bacterial solution to 9-10 to obtain a bacterial suspension for solidification; (3) A certain concentration of calcium acetate solution is prepared, and the pH value is adjusted to 9-10 to obtain a full-mixing method cementing solution; 1 / 2 M 胶 of xanthan gum is divided into 14 equal parts, dissolved in a certain concentration of calcium acetate solution, and the pH value is adjusted to 9-10 to obtain a half-mixing method cementing solution; (4) solidifying by in-situ permeation grouting, sequentially injecting the bacterial suspension in step (2) and the full-mixing method cementing liquid in step (3) into the full-mixing sand glue mixture in step (1), co-grouting the bacterial solution and the full-mixing method cementing liquid for 7 cycles to obtain solidified uranium tailings; or solidifying by in-situ permeation grouting, sequentially injecting the bacterial suspension in step (2) and the semi-mixing method cementing liquid in step (3) into the semi-mixing sand glue mixture in step (1), co-grouting the bacterial solution and the semi-mixing method cementing liquid for 14 cycles to obtain solidified uranium tailings.

2. The method for regulating the precipitation of calcium carbonate induced by Klebsiella oxytoca to solidify uranium tailings using xanthan gum according to claim 1, characterized in that: The M 胶 mass is 1.0% - 1.4% M 砂 .

3. The method of claim 1, wherein the xanthan gum is used to regulate the precipitation of calcium carbonate induced by Klebsiella bacteria for solidification of uranium tailings. The OD of the bacterial suspension in step (2) 600 It ranges from 5.00 to 5.

15.

4. The method of claim 1, wherein the xanthan gum is used to regulate the precipitation of calcium carbonate induced by Klebsiella bacteria for solidification of uranium tailings. In step (2), the pH value of the bacterial solution is adjusted to 10.

5. The method for regulating Klebsiella-induced precipitation of calcium carbonate for solidification of uranium tailings using xanthan gum according to claim 1, characterized in that: In step (2), the liquid culture medium uses water as a solvent, and comprises 20 g / L of a sodium acetate solution and 4 g / L of yeast extract powder.

6. The method for regulating Klebsiella-induced precipitation of calcium carbonate for solidification of uranium tailings using xanthan gum according to claim 1, characterized in that: In step (2), the certain conditions are culturing in a constant-temperature shaking incubator, at a temperature of 30 DEG C, a rotation speed of 100 rpm, and a culturing time of 108-132 h.

7. The method of claim 1, wherein the xanthan gum is used to regulate the precipitation of calcium carbonate induced by Klebsiella bacteria for solidification of uranium tailings. The activation of the Klebsiella bacteria is achieved by the following steps: 1) strain activation: taking a frozen glycerol tube seed from a -80 DEG C refrigerator and thawing at room temperature, inoculating the obtained glycerol seed solution into a liquid culture medium and culturing under certain conditions for 24-36 h to obtain a primary activated bacterial solution; 2) single colony culture: taking 1 ml of the activated bacterial solution and spreading it on the surface of a solid culture medium and standing for culture for 24-36 h, and observing the growth state of the colonies; 3) seed suspension preparation: selecting a single colony with a good growth state in step 2) and transferring it into a liquid culture medium, and culturing for 24-36 h to obtain a seed suspension for expansion culture.

8. The method of claim 7, wherein the xanthan gum is used to regulate the precipitation of calcium carbonate induced by Klebsiella bacteria for solidification of uranium tailings. In step 1), the certain conditions are a culturing temperature of 30 DEG C and a culturing time of 24-36 h.

9. The method for regulating Klebsiella-induced precipitation of calcium carbonate for solidification of uranium tailings using xanthan gum according to claim 1, characterized in that: In step (3), the concentration of the calcium acetate solution is 0.50 mol / L.

10. The method of claim 1-9 for regulating Klebsiella-induced precipitation of calcium carbonate to solidify uranium tailings using xanthan gum, characterized in that: The volume of the bacteria suspension and the volume of the cementing liquid injected in each round of the step (4) are 0.6 times of the pore volume V 孔 .

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