Phosphogypsum-based lightweight aggregate embedding microorganisms and preparation method and application thereof

Abstract

The application relates to the technical field of building material preparation, and discloses phosphogypsum-based light aggregate embedding microorganisms and a preparation method and application thereof. The preparation method of the phosphogypsum-based light aggregate embedding microorganisms comprises the following steps: (1) mixing phosphogypsum powder, slag powder and steel slag powder to obtain a mixture; (2) placing the mixture in a granulating device, spraying an alkali activator, and stirring to obtain nascent alkali-activated aggregate; and (3) naturally curing and constant-temperature and constant-humidity curing the nascent alkali-activated aggregate, and the mass ratio of the phosphogypsum powder, the slag powder and the steel slag powder is 60-70:30-40:0-10. The phosphogypsum-based light aggregate embedding microorganisms prepared by the application can not only serve as aggregate in mortar and concrete, but also can be applied to the self-repairing effect of cracks in mortar and concrete, and is suitable for more types.

Description

Technical Field

[0001] This invention relates to the field of building material preparation technology, specifically to a phosphogypsum-based lightweight aggregate containing embedded microorganisms, its preparation method, and its application. Background Technology

[0002] Phosphogypsum is an industrial solid waste generated during the wet-process phosphoric acid production process. Simultaneously, with the rapid development of the phosphate fertilizer industry, phosphogypsum emissions have increased dramatically. Landfilling phosphogypsum releases harmful impurities such as fluorine, phosphorus, organic matter, heavy metals, and radioactive elements, seriously endangering the environment. Considering the abundant content of phosphogypsum, recycling it as a building material is a promising direction. The CaSO4·2H2O content in phosphogypsum is generally above 85%, making it a potential source of calcium sulfate. Existing research has demonstrated that phosphogypsum can be used as a cement retarder, for example, as a soil conditioner, building gypsum, and road filler; however, the comprehensive utilization rate of phosphogypsum remains below 40%. Cement and concrete are currently the most in-demand building materials, and utilizing phosphogypsum as a raw material for cement and concrete is considered an effective way to treat this solid waste. This aims to reduce the use of natural resources such as clay and shale and to utilize solid waste as a raw material for resource recovery. In recycling strategies, the production of lightweight concrete and mortar aggregates has great practical application potential, especially given the anticipated shortage of natural raw materials such as sand, gravel, and crushed stone.

[0003] Concrete structures inevitably develop cracks due to deformation, creep, fatigue, drying shrinkage, and freeze-thaw cycles. These cracks not only reduce the strength of the concrete structure but also provide pathways for corrosive substances from the environment to penetrate into the concrete. Early shrinkage cracking can be mitigated through quality control of raw materials and adjustment of the mixture composition, such as adding fine limestone particles, using expansion agents, using superabsorbent polymers, optimizing particle size distribution, and adding fibers. However, the crack resistance of these preventive measures may not be sufficient to cope with the actual environment in which concrete is used, especially late-stage cracking under extreme climate and mechanical conditions. Once cracks occur, surface cracks can be repaired manually, but internal and inaccessible cracks are often difficult to manage. Furthermore, traditional repair techniques, such as sealing, grouting, and coatings, are often unsuitable, expensive, time-consuming, and sometimes prone to failure. Therefore, self-healing is a very attractive concept for infrastructure because it allows cracks to heal without any external intervention, and it has received considerable attention in many field applications and trials. Thus, crack repair in concrete structures has always been a research topic in the field of concrete and mortar materials. Among the many methods for repairing concrete or mortar cracks, the use of bacteria to repair concrete cracks has attracted much attention.

[0004] To maintain the vitality of bacteria in concrete and mortar, it is necessary to protect the bacteria or bacterial spores by encapsulation or fixation with a carrier before the concrete and mortar cracks. Immobilized microorganism technology uses physical or chemical methods to combine free microorganisms with specific carriers, fixing them within a certain spatial area. This increases the concentration of microbial cells, buffers the toxicity of external substances to the cells, and thus enhances the self-healing ability of concrete and mortar. Many carriers and methods are used for immobilization, and the effects of immobilization on the self-healing ability of concrete and mortar vary greatly depending on the type of carrier and the combination method. For example, bacteria can be encapsulated in materials such as expanded clay, diatomaceous earth, polyurethane, ceramic particles, silica gel, graphite nanosheets, clay particles, expanded perlite, and cellulose fibers. However, this method suffers from low encapsulation efficiency, high strain leakage rate leading to low strain activity, and affects the self-healing ability of concrete and mortar.

[0005] Therefore, how to adjust and optimize the preparation method of phosphogypsum-based lightweight aggregate with embedded microorganisms, improve the embedding efficiency of the strains, ensure the activity of the strains, and enhance their self-healing ability for concrete and mortar is a technical problem that urgently needs to be solved in this field. Summary of the Invention

[0006] In view of this, the present invention provides a phosphogypsum-based lightweight aggregate with good particle shape, high compressive strength of the cylinder, moderate porosity, and high water absorption.

[0007] Furthermore, the present invention provides a method for preparing phosphogypsum-based lightweight aggregate with embedded microorganisms.

[0008] Furthermore, the present invention provides an application of phosphogypsum-based lightweight aggregate containing embedded microorganisms in concrete or mortar materials.

[0009] In a first aspect, the present invention provides a method for preparing phosphogypsum-based lightweight aggregate, comprising the following steps:

[0010] (1) A mixture is obtained by mixing phosphogypsum powder, slag powder and steel slag powder;

[0011] (2) Place the above mixture in a granulation device, spray in an alkali activator, stir, and obtain nascent alkali activated aggregate;

[0012] (3) The primary alkali-activated aggregate is subjected to natural curing and constant temperature and humidity standard curing to obtain the desired product;

[0013] The mass ratio of the phosphogypsum powder, slag powder, and steel slag powder is 60-70:30-40:0-10.

[0014] In one optional embodiment, the mass ratio of the mixture to the alkali activator is 1:0.25-0.51.

[0015] In one optional embodiment, the alkaline activator is at least one of the following solutions:

[0016] Calcium hydroxide suspension, wherein the calcium hydroxide suspension is prepared according to a CaO:water mass ratio of 1:5-6;

[0017] Sodium water glass with a water glass modulus of 2.5-3.1;

[0018] A mixture of sodium silicate and sodium hydroxide solution at a mass ratio of 0.3-1.5:1, wherein before mixing, the water glass modulus of the sodium silicate is 0.947-3.23 and the concentration of the sodium hydroxide is 4mol / L-6mol / L;

[0019] A mixture of sodium sulfate solution and sodium hydroxide solution in a molar ratio of 1:4-6, wherein before mixing, the concentration of the sodium sulfate solution is 0.8 mol / L-1 mol / L and the concentration of the sodium hydroxide solution is 4 mol / L-6 mol / L.

[0020] In one optional embodiment, in step (2), the stirring includes stirring at 55 r / min-75 r / min for 15 min-20 min.

[0021] In one optional implementation, in step (3), the temperature for natural curing is 20℃-30℃, the relative humidity is 35%-65%, and the curing time is 1d-2d.

[0022] In one optional implementation, in step (3), the temperature of the constant temperature and humidity standard curing is 19℃-21℃, the relative humidity is 85%-95%, and the curing time is 2d-3d.

[0023] Secondly, the present invention provides a phosphogypsum-based lightweight aggregate prepared by the above preparation method.

[0024] Thirdly, the present invention provides a method for preparing phosphogypsum-based lightweight aggregate with embedded microorganisms, comprising the following steps: pretreating the above-mentioned phosphogypsum-based lightweight aggregate; immersing the pretreated phosphogypsum-based lightweight aggregate in a cementing solution and a composite solidifying agent, respectively, to obtain the aggregate.

[0025] In one optional embodiment, the pretreatment step includes sterilizing the phosphogypsum-based lightweight aggregate at a temperature of 120°C-121°C for 20-40 minutes.

[0026] In one optional embodiment, the cementing solution contains 17 g / L to 23 g / L of urea and 0.1 mol / L to 0.5 mol / L of calcium salt solution.

[0027] In one optional embodiment, the calcium salt is at least one of calcium acetate, calcium nitrate, calcium chloride, and calcium lactate.

[0028] In one optional embodiment, the mass ratio of the pretreated phosphogypsum-based lightweight aggregate to the volume ratio of the cementitious liquid is 0.6-0.74:1, with a ratio of g / mL.

[0029] In one alternative embodiment, the soaking time in the cementing solution is 8-12 hours.

[0030] In one optional embodiment, the composite solidifying agent comprises a gel aqueous solution and a carbonate mineralizing bacterial solution.

[0031] In one optional embodiment, the gel is at least one of sodium alginate, gum arabic, xanthan gum, gelatin, carrageenan, and sodium silicate.

[0032] In one optional embodiment, the mass fraction of the gel in the gel aqueous solution is 3wt%-5wt%.

[0033] In one optional embodiment, the carbonate mineralizing bacteria is at least one of Bacillus subtilis, Bacillus alkalophilus, Bacillus spheroidae, Bacillus curvatureis, Bacillus coleoprothiolane, Bacillus pseudostrongylus, Bacillus thuringiensis, Bacillus licheniformis, Bacillus mucilaginosus, Bacillus circulans, Bacillus megaterium, and boron-lysine-resistant Bacillus.

[0034] In one optional embodiment, the concentration of the carbonate mineralizing bacteria solution is 10. 8 CFU / mL-10 9 CFU / mL.

[0035] In one optional embodiment, the volume ratio of the gel aqueous solution to the carbonate mineralizing bacteria solution is 1:1-2.

[0036] In one optional embodiment, the mass ratio of the pretreated phosphogypsum-based lightweight aggregate to the volume ratio of the composite solidifying agent is 0.6-0.8:1, with a ratio of g / mL.

[0037] In one optional embodiment, the soaking in the compound solidified agent includes soaking for 12-24 hours at 23℃-28℃ and 0.7bar-1.5bar.

[0038] In one optional embodiment, the preparation method of the carbonate mineralizing bacteria solution includes: selecting a single colony of carbonate mineralizing bacteria and culturing it at 26℃-29℃ and 170rpm-220rpm for 48h-72h to obtain the original bacterial solution; centrifuging the original bacterial solution and resuspending it in sterile physiological saline to obtain the carbonate mineralizing bacteria solution, which is then stored at 4℃ for later use.

[0039] Fourthly, the present invention provides a phosphogypsum-based lightweight aggregate containing microorganisms prepared by the above method.

[0040] Fifthly, the present invention provides the application of the above-mentioned microbial-embedded phosphogypsum-based lightweight aggregate in self-healing mortar or concrete.

[0041] This invention involves mixing dry materials and then placing them into a pelletizing disc with an alkali activator. The pelletizing mechanism of this process is that the addition of the alkali activator wets the materials as the pelletizing disc rotates. As the pelletizing disc rotates, the materials collide with each other and with the baffles, rolling into pellets. A rotation speed of 55r / min-75r / min is used to make the wet materials adhere to each other and roll to form pellets with a diameter of 2mm-3mm.

[0042] The purpose of natural curing is to allow the lightweight aggregate to hydrate and harden, thus giving it a certain degree of internal structural stability. Standard curing with constant temperature and humidity accelerates hardening and further improves the strength of the lightweight aggregate.

[0043] Compared with the prior art, the technical solution of the present invention has the following advantages:

[0044] 1. The preparation method of phosphogypsum-based lightweight aggregate provided by the present invention includes the following steps: phosphogypsum powder, slag powder, and steel slag powder are mixed and placed in a granulation device, then an alkali activator is sprayed in and stirred to obtain nascent alkali-activated aggregate; the nascent alkali-activated aggregate is then subjected to natural curing and constant temperature and humidity standard curing to obtain the final product. The mass ratio of phosphogypsum powder, slag powder, and steel slag powder is 60-70:30-40:0-10. This invention utilizes the catalytic principle of alkali activator and granulation technology. The activator accelerates the hydration reaction rate of phosphogypsum powder, slag powder, and steel slag powder to form a hydrated gel product (CSH). The phosphogypsum-based lightweight aggregate prepared by this method has good particle shape, high compressive strength of the cylinder, moderate porosity, and high water absorption. Simultaneously, the moderate porosity, high water absorption, and strong adsorption capacity help form a stable network structure, providing conditions for the subsequent adsorption of carbonate mineralizing bacteria. Furthermore, this preparation method is simple, economical, and easily industrialized. Phospholipid-based lightweight aggregates can not only be used as aggregates in mortar and concrete, but also for self-repairing cracks in mortar and concrete, making them applicable to a wider range of types.

[0045] 2. The method for preparing phosphogypsum-based lightweight aggregate with embedded microorganisms provided by the present invention involves immersing the phosphogypsum-based lightweight aggregate in a cementing solution, causing the pores and surface of the lightweight aggregate to adsorb a large amount of calcium ions and urea; immersing the aggregate in a composite solidifying agent, allowing the gel in the composite solidifying agent to rapidly react with the calcium ions adsorbed on the lightweight aggregate and encapsulate them around the phosphogypsum-based lightweight aggregate, achieving a good cross-linking effect. Simultaneously, the gel encapsulates carbonate mineralizing bacteria and fixes them inside and on the surface of the phosphogypsum-based lightweight aggregate, effectively improving the encapsulation efficiency of the carbonate mineralizing bacteria and ensuring bacterial activity. This provides a relatively stable living environment for the carbonate mineralizing bacteria, increases the temperature adaptability range of the strain, and also enhances the strain's buffering capacity against acid-base changes, effectively improving the strain's self-repair efficiency.

[0046] 3. The method for preparing phosphogypsum-based lightweight aggregate for embedding microorganisms provided by the present invention controls the ratio of the mass of the pretreated phosphogypsum-based lightweight aggregate to the volume of the cementing liquid, and the ratio of the mass of the pretreated phosphogypsum-based lightweight aggregate to the volume of the composite solidifying agent, so that no secondary pollution is generated during the gel embedding of microorganisms.

[0047] 4. The method for preparing phosphogypsum-based lightweight aggregate with embedded microorganisms provided by the present invention involves soaking the aggregate in the cementing solution for 8-12 hours, which allows the calcium salt and gel to crosslink better, avoids incomplete crosslinking, and avoids reducing the mechanical strength and activity of carbonate mineralizing bacteria of the phosphogypsum-based lightweight aggregate with embedded microorganisms. Attached Figure Description

[0048] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0049] Figure 1 This is a flowchart of the preparation method of phosphogypsum-based lightweight aggregate with embedded microorganisms according to an embodiment of the present invention.

[0050] Figure 2 This is a flowchart of the strain activity test and leakage situation of the phosphogypsum-based lightweight aggregate with embedded microorganisms according to the present invention.

[0051] Figure 3 This is a schematic diagram of the crack-making method of the present invention.

[0052] Figure 4 This is a schematic diagram of the crack healing process of the mortar in the experimental example of this invention. Detailed Implementation

[0053] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0054] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0055] On one hand, the method for preparing phosphogypsum-based lightweight aggregate provided by this invention includes the following steps: phosphogypsum powder, slag powder, and steel slag powder are mixed and placed in a granulation device, then an alkali activator is sprayed in and stirred to obtain nascent alkali-activated aggregate; the nascent alkali-activated aggregate is then subjected to natural curing and constant temperature and humidity standard curing to obtain the desired aggregate. The mass ratio of phosphogypsum powder, slag powder, and steel slag powder is 60-70:30-40:0-10. This invention utilizes the catalytic principle of alkali activator and granulation technology to prepare the aggregate. The activator accelerates the hydration reaction rate of phosphogypsum powder, slag powder, and steel slag powder, forming a hydrated gel product (CSH). The phosphogypsum-based lightweight aggregate prepared by this method has good particle shape, high compressive strength of the cylinder, moderate porosity, and high water absorption rate. Simultaneously, the moderate porosity, high water absorption rate, and strong adsorption capacity help form a stable network structure, providing conditions for the subsequent adsorption of carbonate mineralizing bacteria. Furthermore, this preparation method is simple, economical, and easily industrialized. Phospholipid-based lightweight aggregates can not only be used as aggregates in mortar and concrete, but also for self-repairing cracks in mortar and concrete, making them applicable to a wider range of types.

[0056] On the other hand, the method for preparing phosphogypsum-based lightweight aggregate with embedded microorganisms provided by the present invention involves immersing the phosphogypsum-based lightweight aggregate in a cementing solution, causing the pores and surface of the lightweight aggregate to adsorb a large number of calcium ions and urea; immersing it in a composite solidifying agent, causing the gel in the composite solidifying agent to react rapidly with the calcium ions adsorbed on the lightweight aggregate and wrap around the phosphogypsum-based lightweight aggregate, achieving a good cross-linking effect. At the same time, the gel encapsulates carbonate mineralizing bacteria and fixes them inside and on the surface of the phosphogypsum-based lightweight aggregate, effectively improving the encapsulation efficiency of carbonate mineralizing bacteria and ensuring bacterial activity, providing a relatively stable living environment for carbonate mineralizing bacteria, increasing the temperature adaptation range of the strain, and also enhancing the strain's buffering capacity against acid-base changes, effectively improving the strain's self-repair efficiency.

[0057] The present invention will be further described in detail below with reference to specific embodiments, which should not be construed as limiting the scope of protection claimed by the present invention.

[0058] The Bacillus subtilis used in the embodiments of the present invention was purchased from Beijing Biotechnology Collection Center, with the number CMCC(B)63501.

[0059] The alkalophilic Bacillus used in the embodiments of the present invention was purchased from the Shanghai Microbiological Preservation Center, with the number SHBCCD17302.

[0060] The Bacillus spheroidae used in the embodiments of the present invention were purchased from the Shanghai Microbiological Preservation Center, with the number ATCC4525.

[0061] The Bacillus curvatureus used in the embodiments of the present invention was purchased from the Shanghai Microbial Preservation Technology Center, with the number SHBCC D10996 Y6.

[0062] The Bacillus coli used in the embodiments of the present invention was purchased from the Shanghai Microbiological Preservation Center, with the number DSM6307.

[0063] The *Bacillus pseudostrongylus* used in this embodiment of the invention was purchased from the Beijing Biotechnology Collection Center, with the number ATCC700159.

[0064] The Bacillus thuringiensis used in this embodiment of the invention was purchased from the Beijing Biotechnology Collection Center, with the number CGMCC1.16.

[0065] The Bacillus licheniformis used in the embodiments of the present invention was purchased from Beijing Biotechnology Collection Center, with the number ATCC11946.

[0066] The Bacillus mucilaginosus used in the embodiments of the present invention was purchased from the Shanghai Microbiological Preservation Center, with the number AS1.232.

[0067] The Bacillus circulans used in the embodiments of the present invention was purchased from the Shanghai Microbiological Preservation Center, with the number ATCC4516.

[0068] The Bacillus megaterium used in the embodiments of the present invention was purchased from the Shanghai Microbiological Preservation Center, with the number ACCC11107.

[0069] The boron-resistant lysine-tolerant Bacillus used in the embodiments of the present invention was purchased from the Shanghai Microbial Preservation Technology Center, with the number ATCCBAA-1146.

[0070] The phosphogypsum powder used in this invention is 200-300 mesh; the slag powder used in this invention is granulated blast furnace slag powder, a high-quality mortar admixture, obtained by drying and grinding granulated blast furnace slag conforming to GB / T203 standards to obtain 1200-1340 mesh powder. The finely ground blast furnace slag comes from molten iron slag quenched in water and can be activated by an alkaline activator with a pH of 12-13. The slag powder used in this invention is grade S95. The steel slag powder is grade one, 200-300 mesh.

[0071] This invention provides an application of phosphogypsum-based lightweight aggregate containing embedded microorganisms in mortar or concrete, applicable at temperatures of 15℃-45℃ and pH of 9-12.

[0072] Example 1

[0073] This embodiment provides a phosphogypsum-based lightweight aggregate with encapsulated microorganisms, comprising the following steps:

[0074] The preparation method of phosphogypsum-based lightweight aggregate includes the following steps:

[0075] (1) Weigh 1200g of phosphogypsum powder and 800g of slag powder and add them to a mixer and stir evenly to obtain a mixture.

[0076] (2) Start the disc granulator and set the rotation speed to 60 r / min. First, put the mixture into the disc granulator, and then spray 515 g of alkali activator into the disc granulator. Run the disc granulator at a speed of 60 r / min for 20 min to obtain the initial alkali activated aggregate. The alkali activator is a mixture of sodium water glass (water glass modulus of 2) and sodium hydroxide (concentration of 5 mol / L) with a mass ratio of 1.5:1.

[0077] (3) The nascent alkali-activated aggregate was first naturally cured for 1 day, and then subjected to constant temperature and humidity standard curing for 2 days to obtain phosphogypsum-based lightweight aggregate P60-SC40, in which the content of phosphogypsum powder was 60wt% and the content of slag powder was 40wt%. The temperature of natural curing was 25℃ and the relative humidity was 55%; the temperature of constant temperature and humidity standard curing was 20℃ and the relative humidity was 95%.

[0078] like Figure 1 The process shown, for microbially encapsulated phosphogypsum-based lightweight aggregate, includes the following steps:

[0079] After sterilizing phosphogypsum-based lightweight aggregate at 120℃ for 20 min and cooling to room temperature, 1200 g of the sterilized phosphogypsum-based lightweight aggregate P60-SC40 was added to a sealed bottle containing 1700 mL of cementing solution (cementing solution consisting of 0.3 mol / L calcium acetate solution and 18 g / L urea) and soaked for 12 h. It was then dried at room temperature for 1 h. Finally, it was transferred to a composite solidification agent (composite solidification agent consisting of 850 mL of 4 wt% sodium alginate and 850 mL of 10% sodium alginate solution). 9 The microorganism-encapsulated phosphogypsum-based lightweight aggregate, denoted as A1, was obtained by drying the microorganism-encapsulated phosphogypsum-based lightweight aggregate in a solution of CFU / mL carbonate mineralizing bacteria at 28℃ and +1 bar for 12 hours.

[0080] This invention employs a dilution plate counting method to prepare carbonate-mineralizing bacterial suspension: First, *Bacillus pasteurellii* is cultured in 4000 mL of sterile UYE medium at 28°C and 170 rpm for 72 h to obtain the original bacterial suspension. Then, the original bacterial suspension is centrifuged at 7000 rpm for 10 min to obtain bacterial pellets, which are then resuspended in sterile physiological saline to obtain a concentration of 10. 9 The CFU / mL carbonate mineralizing bacteria culture was stored at 4°C for later use; the sterile UYE medium included 20 g / L urea and 20 g / L yeast extract.

[0081] Example 2

[0082] This embodiment provides a phosphogypsum-based lightweight aggregate with encapsulated microorganisms, comprising the following steps:

[0083] The preparation method of phosphogypsum-based lightweight aggregate includes the following steps:

[0084] (1) Weigh 1200g of phosphogypsum powder, 700g of slag powder and 100g of steel slag powder and add them to a mixer and stir evenly to obtain a mixture.

[0085] (2) Start the disc granulator and set the rotation speed to 55 r / min. First, put the mixture into the disc granulator, and then spray 525 g of Ca(OH)2 suspension into the disc granulator. Run the machine at 55 r / min for 15 min to obtain the initial alkali activated aggregate. The Ca(OH)2 suspension is prepared according to the mass ratio of CaO to water of 1:6.

[0086] (3) The nascent alkali-activated aggregate was first naturally cured for 2 days, and then subjected to constant temperature and humidity standard curing for 3 days to obtain phosphogypsum-based lightweight aggregate P60-SC35-SP5, in which the content of phosphogypsum powder was 60wt%, the content of slag powder was 35wt%, and the content of steel slag powder was 5wt%. The natural curing temperature was 20℃ and the relative humidity was 60%; the constant temperature and humidity standard curing temperature was 19℃ and the relative humidity was 90%.

[0087] like Figure 1 The process shown, for microbially encapsulated phosphogypsum-based lightweight aggregate, includes the following steps:

[0088] After sterilizing phosphogypsum-based lightweight aggregate at 120℃ for 20 min and cooling to room temperature, 1200 g of the sterilized phosphogypsum-based lightweight aggregate P60-SC35-SP5 was added to a sealed bottle containing 1800 mL of cementing solution (cementing solution consisting of 0.5 mol / L calcium chloride solution and 20 g / L urea) and soaked for 8 h. It was then dried at room temperature for 1 h. Finally, it was transferred to a composite solidification agent (composite solidification agent consisting of 900 mL of 3 wt% xanthan gum and 900 mL of 10% xanthan gum). 8The microorganism-encapsulated phosphogypsum-based lightweight aggregate, denoted as A2, was obtained by drying in an oven at 25°C and +1.5 bar for 24 hours in a CFU / mL carbonate mineralizing bacteria solution until constant weight was achieved.

[0089] This invention employs the dilution plate counting method to prepare carbonate-mineralizing bacterial suspension: First, *Bacillus megaterium* is cultured in 4000 mL of sterile UYE medium at 27°C and 170 rpm for 48 h to obtain the original bacterial suspension. Then, the original bacterial suspension is centrifuged at 5000 rpm for 10 min to obtain bacterial pellets, which are then resuspended in sterile physiological saline solution to obtain a concentration of 10%. 8 The CFU / mL carbonate mineralizing bacteria culture was stored at 4°C for later use. The sterile UYE medium consisted of 20 g / L urea and 20 g / L yeast extract.

[0090] Example 3

[0091] This embodiment provides a phosphogypsum-based lightweight aggregate with encapsulated microorganisms, comprising the following steps:

[0092] The preparation method of phosphogypsum-based lightweight aggregate includes the following steps:

[0093] (1) Weigh 1200g of phosphogypsum powder, 600g of slag powder and 200g of steel slag powder and add them to a mixer and stir evenly to obtain a mixture.

[0094] (2) Start the disc granulator and set the rotation speed to 70 r / min. First, put the mixture into the disc granulator, and then spray 515 g of alkali activator into the disc granulator. Run the disc granulator at a speed of 70 r / min for 18 min to obtain the initial alkali activated aggregate. The alkali activator is sodium water glass (water glass modulus is 3).

[0095] (3) The nascent alkali-activated aggregate was first naturally cured for 1 day, and then subjected to constant temperature and humidity standard curing for 3 days to obtain phosphogypsum-based lightweight aggregate P60-SC30-SP10, in which the content of phosphogypsum powder was 60wt%, the content of slag powder was 30wt%, and the content of steel slag powder was 10wt%. The natural curing temperature was 27℃ and the relative humidity was 50%; the constant temperature and humidity standard curing temperature was 21℃ and the relative humidity was 90%.

[0096] like Figure 1 The process shown, for microbially encapsulated phosphogypsum-based lightweight aggregate, includes the following steps:

[0097] After sterilizing phosphogypsum-based lightweight aggregate at 121℃ for 20 min and cooling to room temperature, 1200 g of the sterilized phosphogypsum-based lightweight aggregate P60-SC30-SP10 was added to a sealed bottle containing 1900 mL of cementing solution (0.2 mol / L calcium lactate solution and 21 g / L urea) and soaked for 12 h. It was then dried at room temperature for 1 h. Finally, it was transferred to a composite solidification agent (composite solidification agent includes 950 mL of 5 wt% gum arabic and 950 mL of 10%... 9 The microorganism-encapsulated phosphogypsum-based lightweight aggregate, denoted as A3, was obtained by drying the microorganism-encapsulated aggregate in a solution of CFU / mL carbonate mineralizing bacteria at 25℃ and +1.2 bar for 24 hours and then drying it in an oven to constant weight.

[0098] This invention employs a dilution plate counting method to prepare carbonate-mineralizing bacterial suspension: First, *Bacillus coli* is cultured in 4000 mL of sterile UYE medium at 26°C and 200 rpm for 48 h to obtain the initial bacterial suspension. Then, the initial bacterial suspension is centrifuged at 4000 rpm for 10 min to obtain bacterial pellets, which are then resuspended in sterile physiological saline to obtain a concentration of 10. 9 The CFU / mL carbonate mineralizing bacteria culture was stored at 4°C for later use. The sterile UYE medium consisted of 20 g / L urea and 20 g / L yeast extract.

[0099] Example 4

[0100] This embodiment provides a phosphogypsum-based lightweight aggregate with encapsulated microorganisms, comprising the following steps:

[0101] The preparation method of phosphogypsum-based lightweight aggregate includes the following steps:

[0102] (1) Weigh 1400g of phosphogypsum powder and 600g of slag powder and add them to a mixer and stir evenly to obtain a mixture.

[0103] (2) Start the disc granulator and set the rotation speed to 65 r / min. First, put the mixture into the disc granulator, and then spray 525 g of alkali activator into the disc granulator. Run the disc granulator at a speed of 65 r / min for 17 min to obtain the initial alkali activated aggregate. The alkali activator is a mixture of sodium sulfate solution (1 mol / L) and sodium hydroxide solution (5 mol / L) (molar ratio of 1:5).

[0104] (3) The nascent alkali-activated aggregate was first naturally cured for 2 days, and then subjected to constant temperature and humidity standard curing for 2 days to obtain phosphogypsum-based lightweight aggregate P70-SC30, in which the content of phosphogypsum powder was 70wt% and the content of slag powder was 30wt%. The temperature of natural curing was 23℃ and the relative humidity was 55%; the temperature of constant temperature and humidity standard curing was 20℃ and the relative humidity was 95%.

[0105] like Figure 1 The process shown, for microbially encapsulated phosphogypsum-based lightweight aggregate, includes the following steps:

[0106] After sterilizing the phosphogypsum-based lightweight aggregate at 121℃ for 20 min and cooling it to room temperature, 1200g of the sterilized phosphogypsum-based lightweight aggregate P70-SC30 was added to a composite solidification agent (the composite solidification agent consisted of 900mL of 4wt% gelatin and 900mL of 10... 8 The microorganism-embedded phosphogypsum-based lightweight aggregate was soaked in a solution of CFU / mL carbonate mineralizing bacteria at 24℃ and +1.3 bar for 24 hours, then dried at room temperature for 1 hour. It was then transferred to a sealed bottle containing 1800 mL of cementing solution (0.4 mol / L calcium lactate solution and 19 g / L urea) and soaked for 24 hours. Finally, it was dried in an oven to constant weight to obtain the microorganism-embedded phosphogypsum-based lightweight aggregate, denoted as A4.

[0107] This invention employs a dilution plate counting method to prepare carbonate-mineralizing bacterial suspension: First, *Bacillus pseudosturcium* is cultured in 4000 mL of sterile UYE medium at 29°C and 170 rpm for 72 h to obtain the original bacterial suspension. Then, the original bacterial suspension is centrifuged at 6000 rpm for 10 min to obtain bacterial pellets, which are then resuspended in sterile physiological saline to obtain a concentration of 10. 8 The CFU / mL carbonate mineralizing bacteria culture was stored at 4°C for later use. The sterile UYE liquid culture medium consisted of 20 g / L urea and 20 g / L yeast extract.

[0108] Comparative Example 1

[0109] This comparative example provides a method for preparing phosphogypsum-based lightweight aggregate, comprising the following steps:

[0110] (1) Weigh 1200g of phosphogypsum powder and 800g of steel slag powder and add them to a mixer and stir evenly to obtain a mixture.

[0111] (2) Start the disc granulator and set the rotation speed to 60 r / min. First, put the mixture into the disc granulator, and then spray 515 g of Ca(OH)2 suspension into the disc granulator. Run the machine at 60 r / min for 20 min to obtain the initial alkali activated aggregate. The Ca(OH)2 suspension is prepared according to the mass ratio of CaO to water of 1:6.

[0112] (3) The nascent alkali-activated aggregate was first naturally cured for 1 day, and then subjected to constant temperature and humidity standard curing for 2 days to obtain phosphogypsum-based lightweight aggregate P60-SP40, in which the content of phosphogypsum powder was 60wt% and the content of steel slag powder was 40wt%. The temperature of natural curing was 25℃ and the relative humidity was 55%; the temperature of constant temperature and humidity standard curing was 20℃ and the relative humidity was 95%.

[0113] Comparative Example 2

[0114] This comparative example provides a method for preparing phosphogypsum-based lightweight aggregate, comprising the following steps:

[0115] (1) Weigh 1400g of phosphogypsum powder, 500g of slag powder and 100g of cement and add them to a mixer and mix them evenly to obtain a mixture.

[0116] (2) Start the disc granulator and set the speed to 60 r / min. First, put the mixture into the disc granulator, and then spray 510 g of water into the disc granulator. Run the disc granulator at a speed of 60 r / min for 20 min to obtain the initial cold-bonded aggregate.

[0117] (3) The nascent cold-bonded aggregate was first naturally cured for 1 day, and then subjected to constant temperature and humidity standard curing for 2 days to obtain phosphogypsum-based lightweight aggregate P70-SC25-C5, in which the content of phosphogypsum powder was 70wt%, the content of slag powder was 25wt%, and the content of cement was 5wt%. The natural curing temperature was 25℃ and the relative humidity was 55%; the constant temperature and humidity standard curing temperature was 20℃ and the relative humidity was 95%.

[0118] Comparative Example 3

[0119] This comparative example provides a method for preparing phosphogypsum-based lightweight aggregate, comprising the following steps:

[0120] (1) Weigh 1400g of phosphogypsum powder, 300g of fly ash and 300g of slag powder and add them to a mixer and mix evenly to obtain a mixture.

[0121] (2) Start the disc granulator and set the rotation speed to 60 r / min. First, put the mixture into the disc granulator, and then spray 515 g of Ca(OH)2 suspension into the disc granulator. Run the machine at 60 r / min for 20 min to obtain the initial alkali activated aggregate. The Ca(OH)2 suspension is prepared according to the mass ratio of CaO to water of 1:6.

[0122] (3) The nascent alkali-activated aggregate was first naturally cured for 1 day, and then subjected to constant temperature and humidity standard curing for 2 days to obtain phosphogypsum-based lightweight aggregate P70-SC15-F15, in which the content of phosphogypsum powder was 70wt%, the content of fly ash was 15wt%, and the content of slag powder was 15wt%. The natural curing temperature was 25℃ and the relative humidity was 55%; the constant temperature and humidity standard curing temperature was 20℃ and the relative humidity was 95%.

[0123] Comparative Example 4

[0124] This comparative example provides a method for preparing phosphogypsum-based lightweight aggregate, comprising the following steps:

[0125] (1) Weigh 1000g of phosphogypsum powder, 600g of slag powder and 400g of steel slag powder and add them to a mixer and stir evenly to obtain a mixture.

[0126] (2) Start the disc granulator and set the rotation speed to 60 r / min. First, put the mixture into the disc granulator, and then spray 515 g of Ca(OH)2 suspension into the disc granulator. Run the machine at 60 r / min for 20 min to obtain the initial alkali activated aggregate. The Ca(OH)2 suspension is prepared according to the mass ratio of CaO to water of 1:6.

[0127] (3) The nascent alkali-activated aggregate was first naturally cured for 1 day, and then subjected to constant temperature and humidity standard curing for 2 days to obtain phosphogypsum-based lightweight aggregate P50-SC30-SP20, in which the content of phosphogypsum powder was 50wt%, the content of slag powder was 30wt%, and the content of steel slag powder was 20wt%. The natural curing temperature was 25℃ and the relative humidity was 55%; the constant temperature and humidity standard curing temperature was 20℃ and the relative humidity was 95%.

[0128] Experimental Example 1

[0129] The phosphogypsum-based lightweight aggregates prepared in Examples 1-4 of this invention were tested for apparent density, compressive strength of cylinder, grading and water absorption according to "Lightweight aggregates and their test methods Part 1: Lightweight aggregates" (GB / T17431.1-2010). The results are shown in Table 1.

[0130] Table 1 Performance test results of phosphogypsum-based lightweight aggregate

[0131]

[0132] As can be seen from the table above, the lower the apparent density, the stronger the water absorption. The phosphogypsum-based lightweight aggregates prepared in Comparative Examples 1 and 4 have a high content of steel slag, resulting in low compressive strength of the aggregate cylinder. Comparative Example 2 uses phosphogypsum-based cold-bonded aggregates containing 5 wt% cement, which also results in low compressive strength of the cylinder, indicating that the phosphogypsum-based cold-bonded aggregates with 5 wt% cement do not hydrate and harden as quickly as the alkali-activated aggregates of this invention, and their strength development is slow. In Comparative Example 3, 15 wt% fly ash is used, which significantly reduces the compressive strength of the aggregate cylinder.

[0133] Experimental Example 2

[0134] Preliminary experiments were conducted using phosphogypsum-based lightweight aggregate with and without microorganisms. The flowchart for the bacterial activity test and leakage analysis of the microorganism-embedded phosphogypsum-based lightweight aggregate is shown below. Figure 2 As shown.

[0135] This study investigated the bacterial activity test of phosphogypsum-based lightweight aggregate. The specific method involved pulverizing either 7g of phosphogypsum-based lightweight aggregate with or without microorganisms in a mortar until the fineness was below 1.18mm. The aggregate was then placed in 30mL of 20g / L urea solution for urease activity testing. Urease activity and pH changes in both phosphogypsum-based and un-microorganism-embedded aggregates were measured at 0h, 6h, 12h, 18h, 24h, 30h, and 36h. The results are shown in Tables 2-5. The gel is insoluble in water, isolating it from external environmental influences; if the gel is not broken, urease activity cannot be tested.

[0136] The preparation steps of phosphogypsum-based lightweight aggregate without microorganism encapsulation include: taking 14g of dried phosphogypsum-based lightweight aggregate prepared in Examples 1-4, sterilizing it at 120℃ for 20min, then soaking it in a sealed bottle containing 100mL of 0.5M calcium acetate solution for 12h, and drying it at room temperature for 1h; then transferring it to 100mL of a mixed solution of sterile water and 5wt% sodium alginate at a volume ratio of 1:1, maintaining it at 28℃ and +1bar for 12h, and then drying it in an oven to constant weight, thus obtaining phosphogypsum-based lightweight aggregate without microorganism encapsulation, denoted as B1-B4 respectively. 7g of this was used for strain activity testing, and the other 7g was used for leakage testing.

[0137] Table 2. Results of phosphogypsum-based light aggregate urease activity tests on microorganisms prepared in the examples.

[0138]

[0139] Table 3. pH changes of phosphogypsum-based lightweight aggregates with embedded microorganisms prepared in the examples.

[0140]

[0141] Table 4. Results of urease activity test in phosphogypsum-based light aggregate without microorganisms.

[0142]

[0143] Table 5. pH changes in phosphogypsum-based lightweight aggregates without microorganisms.

[0144]

[0145]

[0146] Table 2 shows that after 24 hours, the urea decomposition concentrations of A1, A2, A3, and A4 were 17.5 g / L, 17.6 g / L, 18.8 g / L, and 18.7 g / L, respectively. More than 80% (minimum urea decomposition value / initial urea concentration × 100%) of the urea in A1-A4 was decomposed. Table 4 shows that B1-B4 lacked encapsulated carbonate mineralizing bacteria, thus failing to decompose urea. The carbonate mineralizing bacteria used in this invention are urease-producing bacteria, which hydrolyze urea into carbonates through a metabolic process for repairing cracks in mortar or concrete.

[0147] The pH values ​​of B1-B4 (bacterial-free control samples) at 0 h were 10.9, 10.7, 10.7, and 10.8, respectively (Table 5). The pH values ​​of A1-A4 at 0 h were 10.86, 10.68, 10.73, and 10.82, respectively. The addition of carbonate mineralizing bacteria affected the pH values ​​of all phosphogypsum-based lightweight aggregate carrier solutions. After soaking for 24 h, the pH values ​​of A1-A4 were buffered to 9.70-9.79 (Table 3). The encapsulated strains were active, which led to the pH buffering, reaching a suitable level for strain growth and fermentation. This indicates that the bacteria have a certain self-regulating ability and strong alkali resistance.

[0148] Bacterial leakage tests were conducted using phosphogypsum-based lightweight aggregates with embedded microorganisms. Before injecting the cell suspension into the phosphogypsum-based lightweight aggregates, the cell concentration was measured. The initial cell count was then converted from cell CFU / mL to cell CFU / g phosphogypsum-based lightweight aggregates by dividing the cell count by the mass of the phosphogypsum-based lightweight aggregates; this value was recorded as L1. The microorganism-embedded phosphogypsum-based lightweight aggregates were then immersed in demineralized water and agitated. The cell concentration in the water was measured using flow cytometry. The cell count was then converted from cell CFU / mL to cell CFU / g phosphogypsum-based lightweight aggregates by dividing the cell count by the mass of the phosphogypsum-based lightweight aggregates; this value was recorded as L2. Therefore, the leakage percentage = L2 / L1 × 100%.

[0149] The specific steps are as follows: 7g of phosphogypsum-based lightweight aggregate containing microorganisms was soaked in 30mL of demineralized water and then placed on a vibration table at 120r / min for 1h. The bacterial concentration was tested by flow cytometer. The average leakage rate of 3 tests is shown in Table 6.

[0150] Table 6. Results of bacterial leakage test on phosphogypsum-based lightweight aggregate containing embedded microorganisms.

[0151]

[0152]

[0153] In all cases, the amount of phosphogypsum-based lightweight aggregate in each group was set to 7g in the experiments on bacterial viability and leakage. The number of carbonate mineralizing bacteria embedded in the phosphogypsum-based lightweight aggregate depended on the water absorption rate of the phosphogypsum-based lightweight aggregate in Table 1. The higher the water absorption rate, the higher the porosity, and the more carbonate mineralizing bacteria could be embedded. As can be seen from Table 6, the leakage rate of bacteria after encapsulation was 13%-17%, and the leakage rates of A1, A2, A3, and A4 were relatively similar. This is because the phosphogypsum-based lightweight aggregate with embedded microorganisms significantly reduced the bacterial leakage caused by the pore structure and pore size of the phosphogypsum-based lightweight aggregate. The size of carbonate mineralizing bacteria is 2μm-3μm. The high porosity of phosphogypsum-based lightweight aggregate makes it an ideal habitat for carbonate mineralizing bacteria (the pore size ranges of A1, A2, A3, and A4 are 1μm-6μm, 2μm-7μm, 4μm-7μm, and 3μm-10μm, respectively; the mercury porosimetry (MIP) is 24%, 25%, 28%, and 30%, respectively; and the proportion of pores with a pore size of 4μm-10μm is 60%, 63%, 69%, and 72%, respectively).

[0154] The high bacterial activity and low leakage rate of A1, A2, A3, and A4 are due to the good biocompatibility of the gel, its insolubility in water, and its mild gelation conditions (the gel reacts rapidly with calcium ions adsorbed on phosphogypsum-based lightweight aggregate, thereby encapsulating the bacteria) and firmly fixing them inside and on the surface of the lightweight aggregate, making it difficult for the bacteria to escape, thus improving the self-healing effect of the mortar.

[0155] Experimental Example 3

[0156] To evaluate the biomineralization properties of phosphogypsum-based lightweight aggregates embedded with microorganisms, this invention prepares mortar specimens and tests their self-healing ability by observing the crack surface and measuring the crack width. The mortar preparation steps include: A1-A4 are brought to a saturated surface-dry state before use; 698kg / m 3 Sand, 765kg / m 3 Examples 1-4 show the preparation of A1-A4 or unencapsulated microorganism-based phosphogypsum lightweight aggregates B1-B4 with a density of 738.24 kg / m³. 3 The phosphogypsum-based binder was mixed in a mortar mixer for 0.5 minutes, and then 215.32 kg / m³ of binder was added. 3 Stir water for 2 minutes, pour into a 100mm × 50mm (d × H) cylindrical mold, and vibrate on a vibration table for 20 seconds to obtain good flowability and compaction. Wrap the sample with plastic film and the mold to prevent drying, cure at room temperature for 24 hours, and then store in a standard curing chamber for 28 days until the test age, to prepare mortar specimens C1-C4 (corresponding to A1-A4) and D1-D4 (corresponding to B1-B4); wherein, the phosphogypsum-based binder contains 307.6 kg / m³ 3Phosphogypsum powder, 276.84 kg / m³ 3 Slag powder, 30.76 kg / m³ 3 Ordinary Portland cement, all specimens were induced to develop cracks using the splitting method (e.g. Figure 3 As shown in the figure, the splitting specimens were secured with self-locking metal straps, and silicone films of different thicknesses were embedded into the cracks to form cracks of different widths. Healing was tested after 0 days, 14 days, and 28 days (curing was conducted in a standard curing room at 18℃-22℃ and 90%-100% humidity). The results are shown in Table 7 and [Table data would be inserted here]. Figure 4 As shown.

[0157] Table 7. Test results of self-healing ability of each mortar specimen.

[0158]

[0159] From Table 7 and Figure 4 The initial crack width was found to be 0.31 mm–1.24 mm. The gel isolated the external environment and embedded carbonate-mineralizing bacteria in the pores and surface of the phosphogypsum-based lightweight aggregate. When cracks appeared in the mortar, the bacteria were released to repair them. The crack width gradually decreased with increasing healing time, and the number of CaCO3 crystals increased, filling the entire crack with a tight bond strength from single to multiple layers. Simultaneously, the hydration of the slag powder produced a new crystal-matrix interface (flocculent CSH gel and needle-like ettringite), which helped the crystals bridge the cracks again. This healing mechanism enhanced the flexural stiffness of the concrete samples because the crystallized CaCO3 strengthened the continuity of the crack interface. Furthermore, after 28 days of standard curing, the uniaxial compressive strength was almost completely recovered. Cracks D1, D2, D3, and D4 were not completely repaired, with crack widths of 1.17 mm, 0.48 mm, 0.15 mm, and 0.71 mm, respectively. This was because complete repair was not possible without the addition of mineralizing bacteria. The slight healing of cracks in D1-D4 is due to the high activity and high CaO content of the slag in the self-healing mortar containing slag powder, which is conducive to the precipitation of calcite. In addition, due to the hydration reaction between unhydrated cement particles in the mortar and external water, the carbonation process of calcium hydroxide can occur in cracks of relatively small width, producing calcium carbonate precipitation.

[0160] The 28-day compressive strength of mortar specimens C1-C4 (corresponding to A1-A4) and D1-D4 (corresponding to B1-B4) shows that the phosphogypsum-based lightweight aggregate, after being encapsulated with carbonate mineralizing bacteria such as Bacillus megaterium, Bacillus corydalis, and Bacillus pseudostrongylus in gel, is compatible with the cementitious system and can improve the strength and durability of the mortar mixture.

[0161] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing phosphogypsum-based lightweight aggregate with encapsulated microorganisms, characterized in that, The process includes the following steps: pretreating the phosphogypsum-based lightweight aggregate; soaking the pretreated phosphogypsum-based lightweight aggregate in a cementing solution, and then transferring it to a composite solidifying agent for further soaking. The preparation method of the phosphogypsum-based lightweight aggregate includes the following steps: (1) A mixture is obtained by mixing phosphogypsum powder, slag powder and steel slag powder; (2) Place the above mixture in a granulation device, spray in an alkali activator, stir, and obtain nascent alkali-activated aggregate; (3) The primary alkali-activated aggregate is then subjected to natural curing and constant temperature and humidity standard curing to obtain the final product; The mass ratio of the phosphogypsum powder, slag powder, and steel slag powder is 60-70:30-40:0-10; The pretreatment step includes sterilizing the phosphogypsum-based lightweight aggregate at a temperature of 120℃-121℃ for 20min-40min. The cementing solution contains 17 g / L-23 g / L of urea and 0.1 mol / L-0.5 mol / L of calcium salt solution; The composite solidified bacterial agent includes a gel aqueous solution and a carbonate mineralized bacterial solution; The gel is at least one of sodium alginate, gum arabic, xanthan gum, gelatin, and carrageenan.

2. The method for preparing phosphogypsum-based lightweight aggregate with embedded microorganisms according to claim 1, characterized in that, The calcium salt is at least one of calcium acetate, calcium nitrate, calcium chloride, and calcium lactate; And / or, the mass ratio of the pretreated phosphogypsum-based lightweight aggregate to the volume ratio of the cementitious liquid is 0.6-0.74:1, with a ratio of g / mL; And / or, the soaking time in the cementing solution is 8h-24h.

3. The method for preparing phosphogypsum-based lightweight aggregate with embedded microorganisms according to claim 1, characterized in that, The mass fraction of gel in the gel aqueous solution is 3wt%-5wt%; And / or, the carbonate mineralizing bacteria are at least one of Bacillus subtilis, Bacillus alkalophilus, Bacillus spheroidae, Bacillus curvatureis, Bacillus coleus, Bacillus kohlii, Bacillus pseudostrongylus, Bacillus thuringiensis, Bacillus licheniformis, Bacillus mucilaginosus, Bacillus circumferentialis, Bacillus megaterium, and boron-lysine-resistant Bacillus. And / or, the concentration of the carbonate mineralizing bacteria solution is 10. 8 CFU / mL-10 9 CFU / mL; And / or, the volume ratio of the gel aqueous solution to the carbonate mineralizing bacteria solution is 1:1-2; And / or, the mass ratio of the pretreated phosphogypsum-based lightweight aggregate to the volume ratio of the composite solidifying agent is 0.6-0.8:1, with a ratio of g / mL; And / or, soaking in the compound solidified bacterial agent includes: soaking at 23℃-28℃ and 0.7bar-1.5bar for 12h-24h; And / or, the method for preparing the carbonate mineralizing bacteria solution includes: selecting a single colony of carbonate mineralizing bacteria and culturing it at 26℃-29℃ and 170rpm-220rpm for 48h-72h to obtain the original bacterial solution; centrifuging the original bacterial solution and resuspending it in sterile physiological saline to obtain the carbonate mineralizing bacteria solution, which is then stored at 4℃ for later use.

4. The method for preparing phosphogypsum-based lightweight aggregate with embedded microorganisms according to claim 1, characterized in that, The mass ratio of the mixture to the alkaline activator is 1:0.25-0.51; And / or, the base activator is at least one of the following solutions: Calcium hydroxide suspension, wherein the calcium hydroxide suspension is prepared according to a CaO:water mass ratio of 1:5-6; Sodium silicate with a water glass modulus of 2.5-3.1; A mixture of sodium silicate and sodium hydroxide solution in a mass ratio of 0.3-1.5:

1. Before mixing, the sodium silicate has a water glass modulus of 0.947-3.23 and a sodium hydroxide concentration of 4 mol / L-6 mol / L. A mixture of sodium sulfate solution and sodium hydroxide solution in a molar ratio of 1:4-6, wherein before mixing, the concentration of the sodium sulfate solution is 0.8 mol / L-1 mol / L and the concentration of the sodium hydroxide solution is 4 mol / L-6 mol / L.

5. The method for preparing phosphogypsum-based lightweight aggregate with embedded microorganisms according to claim 1, characterized in that, In step (2), the stirring includes stirring at 55r / min-75r / min for 15min-20min; And / or, in step (3), the temperature of natural curing is 20℃-30℃, the relative humidity is 35%-65%, and the curing time is 1d-2d; And / or, the temperature for the constant temperature and humidity standard curing is 19℃-21℃, the relative humidity is 85%-95%, and the curing time is 2-3 days.

6. A phosphogypsum-based lightweight aggregate containing encapsulated microorganisms, prepared by the preparation method according to any one of claims 1-5.

7. The application of the microbial-embedded phosphogypsum-based lightweight aggregate as described in claim 6 in self-healing mortar or concrete.

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