Self-repairing supersulfur cement and preparation method thereof

Abstract

The present invention belongs to the field of geotechnical materials technology and relates to a self-healing supersulfur cement and its preparation method. The self-healing supersulfur cement comprises the following components by weight: 75%-85% slag, 10%-20% bio-modified phosphogypsum, and 1%-5% alkaline components. Industrial by-product phosphogypsum is pre-treated and bio-modified, and then used as a raw material for a microbial remediation agent to prepare the supersulfur cement. The supersulfur cement exhibits excellent self-healing capabilities and compressive strength.

Description

Technical Field

[0001] The present invention belongs to the technical field of geotechnical materials, and in particular relates to a self-repairing supersulfur cement and a preparation method thereof. Background Art

[0002] Phosphogypsum is a solid industrial byproduct produced during the wet process of phosphoric acid production. Despite the rapid development of my country's phosphate fertilizer industry, a significant amount of phosphogypsum remains discarded and accumulated. This massive accumulation of phosphogypsum not only consumes significant land resources but also pollutes the surrounding soil, water, and air. The five provinces with the highest phosphogypsum production in my country are Yunnan, Guizhou, Hubei, Sichuan, and Anhui, accounting for approximately 80% of the national output, with Yunnan accounting for approximately 25% of the total. Due to Yunnan's massive phosphogypsum production, coupled with its remote location, limited market reach, and a relatively late start in the comprehensive utilization of phosphogypsum, the comprehensive utilization rate is only approximately 20%. To address this, Yunnan Province has proposed a series of comprehensive phosphogypsum utilization plans. In 2022, Yunnan Province proposed the resource utilization of bulk industrial solid waste, utilizing phosphogypsum and other solid waste resources to produce new building materials. The focus is on promoting the comprehensive utilization of phosphogypsum and achieving breakthroughs in the comprehensive utilization of its sulfur, calcium, and fluorine resources.

[0003] The self-healing of concrete can be divided into autonomous healing and autogenous healing. Autogenous healing is caused by the continuous hydration of internal cement particles or the continuous reaction of materials with secondary hydration properties, while autonomous healing depends on the action of various healing agents, such as microcapsules, highly absorbent polymers and microbial self-repair. Summary of the Invention

[0004] The present invention addresses the shortcomings of existing technologies and provides a self-repairing supersulfur cement and its preparation method. Industrial by-product phosphogypsum is pre-treated and bio-modified to serve as a raw material for a microbial remediation agent for the preparation of supersulfur cement. The supersulfur cement exhibits excellent self-repairing capabilities and compressive strength.

[0005] To this end, the first aspect of the present invention provides a self-repairing supersulfur cement comprising the following components in weight percentage: 75%-85% slag, 10%-20% bio-modified phosphogypsum and 1%-5% alkaline component.

[0006] In some embodiments of the present invention, the self-repairing supersulfur cement comprises the following components in weight percentage: 75%-80% slag, 15%-20% bio-modified phosphogypsum and 3%-5% alkaline component.

[0007] According to the present invention, the self-repairing supersulfur cement comprises the following components in weight percentage: 80% slag, 15% bio-modified phosphogypsum and 5% alkaline component.

[0008] In some embodiments of the present invention, the alkaline component includes cement clinker.

[0009] The present invention utilizes industrial by-product phosphogypsum and pretreats it with biological agents to obtain bio-modified phosphogypsum. Most of the phosphorus and fluorine impurities and fixed heavy metals have been removed from the bio-modified phosphogypsum, and a large number of bacteria remain inside the bio-modified phosphogypsum, which has good biomineralization ability. The bio-modified phosphogypsum can be used as a raw material for microbial remediation agents to prepare supersulfur cement with good self-repairing ability and compressive strength.

[0010] The second aspect of the present invention provides a method for preparing the self-repairing supersulfur cement according to the first aspect of the present invention, comprising the following steps:

[0011] S1: using biological agents to modify phosphogypsum to obtain bio-modified phosphogypsum;

[0012] S2: The bio-modified phosphogypsum obtained in step S1 is mixed with slag and alkaline components according to weight percentage to prepare self-repairing supersulfur cement.

[0013] The biological agent of the present invention is used to induce the insoluble phosphorus and fluorine impurities in phosphogypsum to react with carbonate ions (CO3 2- ) preferentially reacts to form calcium carbonate precipitate, further removing phosphorus and fluorine impurities and reducing their content in phosphogypsum; and causing a large number of active nutritional bacteria to exist inside the phosphogypsum, which has good biomineralization ability and can be used as a microbial remediation agent.

[0014] In some embodiments of the present invention, the biological preparation comprises a Bacillus subtilis solution and a urea solution, and the volume ratio of the Bacillus subtilis solution to the urea solution is 1.5-2:1, preferably 1.5-1.8:1.

[0015] According to the present invention, the volume ratio of the Bacillus subtilis solution to the urea solution is 1.5:1.

[0016] In some embodiments of the present invention, the concentration of the Bacillus subtilis solution is 2.0×10 9 -3.9×10 11 cfu / mL, preferably 7.2×10 10 -3.9×10 11 cfu / mL; the concentration of the urea solution is 1-2 mol / L, preferably 1-1.5 mol / L.

[0017] According to the present invention, the concentration of the Bacillus subtilis solution is 2.0×10 9 cfu / mL, 7.2×10 10 cfu / mL or 3.9×10 11 cfu / mL; the concentration of the urea solution is 1 mol / L.

[0018] In some embodiments of the present invention, the method for culturing Bacillus subtilis comprises: inoculating a Bacillus subtilis solution into a liquid culture medium at an inoculation ratio of 1% by volume, and culturing the culture medium on a 36° C. constant temperature shaker at 150-300 rpm for 24-48 hours.

[0019] In some embodiments of the present invention, the liquid culture medium comprises 10.0 g / L peptone, 5 g / L yeast powder and 10 g / L sodium chloride, and the pH value is adjusted to 7.3±0.2 with 1 mol / L NaOH solution; the liquid culture medium is sterilized by autoclaving at 121°C for 20-30 min.

[0020] In some embodiments of the present invention, step S1 includes: mixing phosphogypsum and calcium hydroxide solution in proportion to obtain a phosphogypsum-calcium hydroxide suspension, and then mixing it with a biological agent in proportion.

[0021] In some embodiments of the present invention, the phosphogypsum may be untreated or unpretreated industrial by-product phosphogypsum.

[0022] In some embodiments of the present invention, the preparation of bio-modified phosphogypsum in step S1 comprises the following specific steps:

[0023] M1: Dry the fresh phosphogypsum at 50-70℃ for 12-18h, grind the dried phosphogypsum, and select the powder with a particle size of 60-80μm;

[0024] M2: Mix the phosphogypsum powder obtained in step M1 with a saturated calcium hydroxide solution in a solid-liquid ratio of 1:2-3, stir evenly, age for 20-24 hours, and adjust the pH value to 8.0±0.2 to obtain a phosphogypsum-calcium hydroxide suspension;

[0025] M3: Mix the phosphogypsum-calcium hydroxide suspension prepared in step M2 with the biological agent in a volume ratio of 1.3-1.6:1, stir evenly, ferment the phosphogypsum for 36-48 hours, and filter to obtain bio-modified phosphogypsum.

[0026] The present invention utilizes industrial by-product phosphogypsum and pre-treats it with Bacillus subtilis. The Bacillus subtilis metabolizes the urease to promote the hydrolysis of urea to generate NH4OH under alkaline conditions. 4+ and CO3 2- The bacterial surface and secreted extracellular polymers (EPS) provide nucleation sites and adsorb Ca 2+, and finally react to form calcium carbonate precipitate; it can effectively remove phosphorus and fluorine impurities and fixed heavy metals inside the phosphogypsum, and the large number of bacteria remaining in the biologically modified phosphogypsum can metabolize and mineralize under aerobic conditions to produce calcium carbonate precipitate, thereby filling and repairing cracks, and has good self-repairing properties.

[0027] In some embodiments of the present invention, in step M2, a saturated calcium hydroxide solution or distilled water is used to adjust the pH value.

[0028] According to the present invention, in step M2, the phosphogypsum powder and the saturated calcium hydroxide solution are mixed in a solid-liquid ratio of 1:2.

[0029] According to the present invention, in step M3, the phosphogypsum-calcium hydroxide suspension and the biological agent are mixed in a volume ratio of 1.3:1.

[0030] In some embodiments of the present invention, in step M3, the phosphogypsum is fermented at 36° C. for 36-48 hours, with regular stirring every 2 hours.

[0031] In some embodiments of the present invention, in step M3, a 500-mesh filter is used to filter out the gypsum powder, and the filtered phosphogypsum powder is dried at 40-45° C. for 6-8 hours.

[0032] In some embodiments of the present invention, the method for preparing the saturated calcium hydroxide solution includes: preparing a certain amount of calcium hydroxide at 20° C., placing it in a container, adding clean water and stirring evenly until it is completely dissolved; then filtering to remove suspended matter, transferring it to another container, adding a certain amount of dilute hydrochloric acid and stirring evenly until the solution becomes clear; finally, heating to boiling point, stirring evenly until the solution becomes saturated, and obtaining a saturated calcium hydroxide solution.

[0033] In the present invention, calcium hydroxide is used to adjust the pH of phosphogypsum and precipitate impurities such as soluble phosphorus, residual acid, and fluorine in the phosphogypsum, and at the same time provides a calcium source required for biomineralization.

[0034] Beneficial effects of the present invention:

[0035] (1) The present invention provides a self-repairing supersulfur cement, which utilizes industrial by-product phosphogypsum and undergoes pretreatment for biological modification. The content of phosphorus and fluorine impurities and fixed heavy metals in the bio-modified phosphogypsum is reduced, and a large number of bacteria are retained, which has good biomineralization ability and can be used as a raw material for microbial remediation agents to prepare supersulfur cement. The supersulfur cement has good self-repairing ability and compressive strength.

[0036] (2) The present invention provides a method for preparing self-repairing supersulfur cement, which uses Bacillus subtilis to pretreat industrial by-product phosphogypsum, and produces urease through Bacillus subtilis metabolism, which can promote the hydrolysis of urea to generate NH under alkaline conditions. 4+ and CO3 2- The bacterial surface and secreted extracellular polymers (EPS) provide nucleation sites and adsorb Ca 2+ , and finally react to form calcium carbonate precipitation; it can effectively remove phosphorus and fluorine impurities and fixed heavy metals inside the phosphogypsum, and the large number of bacteria remaining in the bio-modified phosphogypsum can metabolize and mineralize under aerobic conditions to produce calcium carbonate precipitation, thereby filling and repairing cracks, and has good self-repairing properties; as a raw material for microbial remediation agents, it can be used to prepare supersulfur cement, which can produce supersulfur cement with good self-repairing ability and compressive strength;

[0037] (3) The preparation method provided by the present invention has many advantages such as simple reaction, short processing time, no secondary pollution and low cost. It can make large-scale use of industrial by-product phosphogypsum, promote the comprehensive utilization of phosphogypsum resources, and solve environmental protection problems. DETAILED DESCRIPTION

[0038] In order to make the present invention easier to understand, the present invention will be described in detail below with reference to embodiments. These embodiments are only for illustration and do not limit the scope of application of the present invention.

[0039] Example 1

[0040] This embodiment provides a method for preparing bio-modified phosphogypsum, comprising the following specific steps:

[0041] M1: Dry fresh phosphogypsum at 60°C for 12 hours, grind the dried phosphogypsum, and select a powder with a particle size of 75 μm;

[0042] M2: Mix the phosphogypsum powder obtained in step M1 with a saturated calcium hydroxide solution in a solid-liquid ratio of 1:2, stir evenly, isolate from air and age for 24 hours, then measure the pH value, and adjust the pH value to 8.0±0.2 using distilled water or a saturated calcium hydroxide solution to obtain a phosphogypsum-calcium hydroxide suspension;

[0043] M3: Preparation of biological preparation: Inoculate the Bacillus subtilis solution into the liquid culture medium at a volume ratio of 1%, and shake at 150 rpm at 36°C for 24-48 hours; the liquid culture medium contains 10.0 g / L peptone, 5 g / L yeast powder, and 10 g / L sodium chloride, and the pH value is adjusted to 7.3±0.2 with 1 mol / L NaOH solution; sterilize the liquid culture medium at 121°C for 20 minutes; add a 2.0×10 9A Bacillus subtilis solution with a concentration of 1 cfu / mL and a urea solution with a concentration of 1 mol / L were mixed at a volume ratio of 1.5:1 to obtain a biological agent;

[0044] M4: Mix the phosphogypsum-calcium hydroxide suspension prepared in step M2 and the biological agent prepared in step M3 in a volume ratio of 1.3:1, stir evenly, and ferment the phosphogypsum in a constant temperature bacterial incubator at 36°C for 48 hours, stirring regularly every 2 hours, and then filter out the gypsum powder through a 500-mesh filter. Dry the filtered phosphogypsum powder in a constant temperature oven at 45°C for 6 hours to obtain bio-modified phosphogypsum.

[0045] The bio-modified phosphogypsum provided in this example is denoted as PG1.

[0046] Example 2

[0047] This example uses the same method as in Example 1 to prepare bio-modified phosphogypsum, with the only difference being that the concentration is 7.2×10 10 A Bacillus subtilis solution with a concentration of 1 cfu / mL and a urea solution with a concentration of 1 mol / L were mixed in a volume ratio of 1.5:1 to obtain a biological agent for treating phosphogypsum.

[0048] The bio-modified phosphogypsum provided in this example is denoted as PG2.

[0049] Example 3

[0050] This example uses the same method as in Example 1 to prepare bio-modified phosphogypsum, with the only difference being that the concentration is 3.9×10 11 A Bacillus subtilis solution with a concentration of 1 cfu / mL and a urea solution with a concentration of 1 mol / L were mixed in a volume ratio of 1.5:1 to obtain a biological agent for treating phosphogypsum.

[0051] The bio-modified phosphogypsum provided in this example is denoted as PG3.

[0052] Examples 4-6

[0053] Examples 4-6 provide a method for preparing self-repairing supersulfur cement, comprising: mixing the bio-modified phosphogypsum prepared in Example 3 with slag and an alkaline component in varying weight percentages to prepare self-repairing supersulfur cements, designated C1-C3. The formulations of self-repairing supersulfur cements C1-C3 are shown in Table 1.

[0054] Table 1 Self-repairing supersulfur cement C1-C3 ratio table

[0055] Self-repairing supersulfur cement PG3 (%) slag(%) Alkaline component (%) C1 10 85 5 C2 15 80 5 C3 20 75 5

[0056] Examples 7-8

[0057] Examples 7-8 provide a method for preparing a self-healing supersulfur cement, comprising: mixing the bio-modified phosphogypsum prepared in Examples 1-2 with slag and an alkaline component according to weight percentages, respectively. The prepared self-healing supersulfur cement is denoted as C4-C5. The formulation of self-healing supersulfur cement C4-C5 is shown in Table 2.

[0058] Table 2 Self-repairing supersulfur cement C4-C5 ratio

[0059]

[0060] Comparative Examples 1-3

[0061] Comparative Examples 1-3 provide the same method as Example 3 for preparing phosphogypsum, with the only difference being that the calcium hydroxide suspension and the biological agent are replaced by deionized water in equal proportions, or the biological agent is replaced by deionized water in equal proportions, or the biological agent is replaced by a preparation not inoculated with bacteria in equal proportions.

[0062] The phosphogypsum provided in Comparative Examples 1-3 is recorded as G1-G3.

[0063] The treatment reagents used in preparing bio-modified phosphogypsum in Example 3 and in preparing phosphogypsum in Comparative Examples 1-3 are shown in Table 3.

[0064] Table 3 Treatment reagent ratio table

[0065]

[0066] Comparative Examples 4-6

[0067] Comparative Examples 4-6 provide a method for preparing supersulfur cement, comprising: mixing the phosphogypsum prepared in Comparative Examples 1-3 with slag and an alkaline component according to weight percentages, respectively, to prepare supersulfur cements denoted as M1-M3. The proportions of supersulfur cements M1-M3 are shown in Table 4.

[0068] Table 4 Supersulfur cement M1-M3 ratio table

[0069] Supersulfur cement G1(％) G2(％) G3(％) slag(%) Alkaline component (%) M1 15 0 0 80 5 M2 0 15 0 80 5 M3 0 0 15 80 5

[0070] Test Example 1

[0071] Weigh 0.5 g of the biomodified phosphogypsum PG3 prepared in Example 3 and the phosphogypsum G1-G3 prepared in Comparative Examples 1-3, respectively, and place them in a sterilized cement-based material simulated void solution (calcium hydroxide 0.002 mol / L, potassium hydroxide 0.54 mol / L, sodium hydroxide 0.25 mol / L, potassium sulfate 0.003 mol / L), stir evenly, and place in a constant temperature incubator at 36 ° C ± 1 ° C. The calcium ion concentration C in the solution is measured every 4 h. t(mg / L) was measured three times until the solution calcium ion concentration remained constant. The mineralization capacity of the bio-modified phosphogypsum PG3 prepared in Example 3 and the phosphogypsums G1-G3 prepared in Comparative Examples 1-3 was determined and calculated according to the method in Appendix A of T / CECS 973-2021, Technical Specification for Microbial Self-Repairing Concrete. The results are shown in Table 5.

[0072] Table 5 Phosphogypsum mineralization capacity

[0073]

[0074]

[0075] As can be seen from the results in Table 5, the phosphogypsum G1-G3 prepared in Comparative Examples 1-3 basically have no biomineralization ability, while the bio-modified phosphogypsum prepared in the present invention has a strong mineralization ability; this shows that the present invention uses Bacillus subtilis to pretreat industrial by-product phosphogypsum, which can make the phosphogypsum have a strong mineralization ability and can be used as a raw material for microbial remediation agents for the preparation of supersulfur cement.

[0076] Test Example 2

[0077] The standard consistency water consumption of the control group was measured according to GB / T 1346-2011 "Test Method for Standard Consistency Water Consumption, Setting Time and Stability of Cement". The standard consistency water consumption was 175 ml, corresponding to a water-cement ratio of 0.35. The same water-cement ratio was used in each experimental group. The self-repairing supersulfur cement C2 prepared in Example 5 and the supersulfur cements M1-M3 prepared in Comparative Examples 4-6 were respectively cast in 70.7×70.7×70.7mm according to the standard consistency water consumption. 3 The compressive strength of the pure slurry cube specimens was measured after standard curing for 3 days, 7 days, and 28 days. The results are shown in Table 6.

[0078] Table 6 Compressive strength of supersulfur cement paste specimens (MPa)

[0079]

[0080] From the results in Table 6, it can be seen that the self-repairing supersulfur cement C2 prepared in Example 5 has higher compressive strength than the supersulfur cement M1-M3 prepared in Comparative Examples 4-6. There are a large number of phosphorus and fluorine impurities in the untreated phosphogypsum, which affects the compressive strength of the supersulfur cement. The present invention uses Bacillus subtilis to pretreat the industrial by-product phosphogypsum. After biological modification, there are still a large number of active nutritional bacteria in the phosphogypsum. Under suitable environmental conditions, the bacteria can metabolize normally, thereby inducing calcium carbonate precipitation, further reducing the phosphorus and fluorine impurity content in the phosphogypsum, and being used to prepare supersulfur cement will further form calcium carbonate precipitation, thereby improving the compressive strength of the supersulfur cement.

[0081] Test Example 3

[0082] The self-repairing supersulfur cements C1-C3 prepared in Examples 4-6 and supersulfur cements M1-M3 prepared in Comparative Examples 4-6 were respectively cast into 70.7×70.7×70.7mm 3 Cube specimens of the slurry were prepared and cured for 7 days. Each group of specimens was pre-cracked at 70% of their ultimate strength, selecting cracks with widths between 0.3 and 0.5 mm. The pre-cracked specimens were cured in a dry-wet cycle, first soaking them in water for 12 hours to heal, then air-drying them for 12 hours. The crack area repair rate for each selected crack in each specimen was measured and calculated using the method in Appendix C of T / CECS 973-2021, Technical Specification for the Application of Microbiological Self-Healing Concrete. The results are shown in Table 7.

[0083] Table 7 Crack area repair rate of test blocks

[0084]

[0085] The maximum crack repair width of each group of test blocks at 56 days was measured, and the results are shown in Table 8.

[0086] Table 8 Maximum crack repair width of the test block at 56 days

[0087] Supersulfur cement Maximum crack repair width (mm) C1 0.48 C2 0.78 C3 0.96 M1 0.08 M2 0.12 M3 0.09

[0088] As can be seen from the results in Tables 7 and 8, the self-repairing supersulfur cements C1-C3 prepared in Examples 4-6 have good crack self-healing effects. The present invention uses Bacillus subtilis to pretreat the industrial by-product phosphogypsum. The large number of bacteria remaining inside the bio-modified phosphogypsum induces a large amount of mineral precipitation, thereby sealing the cracks and giving the supersulfur cement good self-repairing properties. As the proportion of bio-modified phosphogypsum added increases, more bacteria and nutrients are introduced, and bacterial metabolism induces mineralization, resulting in higher calcium carbonate precipitation to seal the cracks, and the self-repairing properties of the prepared supersulfur cement are improved accordingly.

[0089] Test Example 4

[0090] The self-repairing supersulfur cements C2 and C4-5 prepared in Example 5 and Example 7-8, respectively, were measured and calculated using the same method as in Test Example 3 for the crack area repair rate of each test block. The results are shown in Table 9.

[0091] Table 9 Crack area repair rate of test blocks

[0092]

[0093] The maximum crack repair width of each group of test blocks at 56 days was measured, and the results are shown in Table 10.

[0094] Table 10 Maximum crack repair width of the test block at 56 days

[0095] Supersulfur cement Maximum crack repair width (mm) C4 0.28 C5 0.42 C2 0.78

[0096] The results in Tables 9 and 10 show that the self-healing properties of the resulting supersulfur cement improve as the bacterial concentration of the biological agent used to treat phosphogypsum increases. Using biological agents with high bacterial concentrations to treat phosphogypsum increases the amount of bacteria adsorbed by the phosphogypsum, allowing mineralization and metabolism to produce more calcium carbonate precipitation to seal cracks, thereby improving the self-healing properties of the supersulfur cement. However, when the bacterial concentration of the biological agent reaches a certain level, the phosphogypsum cannot adsorb any more bacteria, and the self-healing properties of the supersulfur cement stabilize at this level.

[0097] It should be noted that the embodiments described above are only used to explain the present invention and do not constitute any limitation of the present invention. The present invention has been described with reference to typical embodiments, but it should be understood that the words used therein are descriptive and explanatory words, rather than restrictive words. The present invention may be modified as specified within the scope of the claims of the present invention, and the present invention may be revised without departing from the scope and spirit of the present invention. Although the present invention described therein relates to specific methods, materials and embodiments, it does not mean that the present invention is limited to the specific examples disclosed therein. On the contrary, the present invention can be extended to all other methods and applications with the same function.

Claims

1. A method for preparing self-repairing supersulfur cement, characterized in that: The self-repairing supersulfur cement comprises the following components in weight percentage: 75%-85% slag, 10%-20% bio-modified phosphogypsum and 1%-5% alkaline component; The preparation method comprises the following steps: S1: Using biological agents to modify phosphogypsum to obtain bio-modified phosphogypsum; The specific steps are: M1: Dry the fresh phosphogypsum at 50-70℃ for 12-18h, grind the dried phosphogypsum, and select a powder with a particle size of 60-80μm; M2: Mix the phosphogypsum powder obtained in step M1 with a saturated calcium hydroxide solution in a solid-liquid ratio of 1:2-3, stir evenly, age for 20-24 hours, and adjust the pH value to 8.0±0.2 to obtain a phosphogypsum-calcium hydroxide suspension; M3: mixing the phosphogypsum-calcium hydroxide suspension prepared in step M2 with a biological agent in a volume ratio of 1.3-1.6:1, stirring evenly, fermenting the phosphogypsum at 36°C for 36-48 hours, and filtering to obtain bio-modified phosphogypsum; the biological agent comprises a Bacillus subtilis solution and a urea solution; the volume ratio of the Bacillus subtilis solution to the urea solution is 1.5-2:1; S2: The bio-modified phosphogypsum obtained in step S1 is mixed with slag and alkaline components according to weight percentage to prepare self-repairing supersulfur cement.

2. The preparation method according to claim 1, wherein The concentration of the Bacillus subtilis solution is 2.0×10 9 -3.9×10 11 cfu / mL; the concentration of the urea solution is 1-2 mol / L.

3. The preparation method according to claim 1, characterized in that The method for culturing Bacillus subtilis comprises: inoculating a Bacillus subtilis solution into a liquid culture medium at an inoculation ratio of 1% by volume, and culturing the culture medium on a 36° C. constant temperature shaker at 150-300 rpm for 24-48 hours; The liquid culture medium includes 10.0 g / L peptone, 5 g / L yeast powder and 10 g / L sodium chloride, and the pH value is adjusted to 7.3±0.2 with 1 mol / L NaOH solution; the liquid culture medium is sterilized by autoclaving at 121° C. for 20-30 minutes.

4. The preparation method according to claim 1, characterized in that In step M2, a saturated calcium hydroxide solution or distilled water is used to adjust the pH value.

5. The preparation method according to claim 1, characterized in that In the step M3, stirring is performed regularly every 2 hours.

6. The preparation method according to claim 1, characterized in that In the step M3, the gypsum powder is filtered out using a 500-mesh filter, and the filtered phosphogypsum powder is dried at 40-45° C. for 6-8 hours.

Images