Method for generating calcium carbonate through microorganism mineralization by exciting gypsum solid waste

Abstract

The invention discloses a method for generating calcium carbonate through microorganism mineralization by exciting gypsum solid waste, and belongs to the field of solid waste recycling. The method comprises the following steps: pretreating the gypsum solid waste; exciting the gypsum solid waste; preparing a microbial bacterial liquid; and mixing the microbial liquid with the excited calcium source. According to the method, the gypsum solid waste is used as a calcium source substitute for generating calcium carbonate through microbial mineralization, so that the problems of singleness and high price of a calcium source in a microbial mineralization technology are solved, and meanwhile, the gypsum solid waste can be greatly and reasonably recycled. Meanwhile, a new solution is provided for large-scale application of a microbial mineralization technology. Besides, the utilization of the gypsum solid waste can further reduce the cost of the technology, the pure-phase calcium carbonate can be generated through one-time microbial mineralization, CO2 gas does not need to be introduced, various chemical reagents do not need to be used, the process is simple, and the equipment requirement is low.

Description

Technical Field

[0001] The invention belongs to the field of solid waste resource utilization, and relates to a method for stimulating gypsum solid waste for microbial mineralization to generate calcium carbonate, specifically a method for using stimulated gypsum solid waste as a calcium source in combination with microorganisms to generate calcium carbonate. Background Art

[0002] Microbial induced calcium carbonate precipitation (MICP) is a natural biological mediated technology that has been increasingly used in soil remediation, slope treatment, island and reef construction, and cultural relics restoration. It is a new remediation technology that combines chemical fixation with microbial in-situ remediation. It mainly uses bacteria to induce the production of CaCO 3 Precipitation, precipitated CaCO 3 Filling in the pores in the soil, cementing the soil particles together and improving the strength of the soil. According to the study of document 1 "The Effect of Calcium Source on the Uniformity of Microbial Mineralized Cemented Sand Materials [J]" (Xu Xichen, Guo Hongxian, Cheng Xiaohui, Qiao Jing, Du Jianhang. Journal of Civil and Environmental Engineering (Chinese and English), 2024, 46(05): 57-63.), calcium chloride as a calcium source has the disadvantages of high cost and chloride ion erosion, which in turn affects the large-scale application of this technology. Therefore, finding a new calcium source to replace traditional calcium chloride is of great significance for microbial mineralization technology. Most of the replaceable calcium sources in the prior art are calcium acetate, calcium nitrate and calcium lactate, etc., but these calcium sources can only replace calcium chloride by changing the chemical reagents and still cannot effectively solve the problem of large-scale application. According to the research in document 2, "Principles of microbial mineralization reaction, deposition and destruction mechanisms and theories: research progress and challenges [J]" (Liu Hanlong, Zhao Chang, Xiao Yang. Journal of Geotechnical Engineering, 2024, 46(07): 1347-1358.), waste can be used as a substitute for calcium source, such as using acid to dissolve calcium-rich waste such as eggshells and limestone powder. Therefore, using calcium-rich solid waste materials for microbial mineralization to generate calcium carbonate is one of the effective ways to solve the large-scale application of this method.

[0003] Gypsum solid waste is a solid by-product derived from industrial production. Its main component is calcium sulfate dihydrate (CaSO 4 ·2H 2O), the annual amount of gypsum solid waste in the world can reach more than 500 million tons, and the amount of gypsum solid waste in China can also reach several tons. According to the research of document 3 "Research Progress on Recycling of Gypsum Solid Waste [J]" (Xin Xiangyu, Chen Guangli, Zhang Xiuzhi, et al. China Powder Technology, 2023, 29(01): 10-18.), the long-term stacking of gypsum solid waste will not only occupy a large amount of land resources, but also the residual free acid and heavy metals will cause serious pollution to the soil and water in the accumulation area, leading to the deterioration of the surrounding environment. Therefore, harmless treatment and comprehensive resource utilization of gypsum solid waste to produce high-value products that can be recycled not only has environmental benefits, but also can create economic value.

[0004] At present, there are many methods for the resource utilization of gypsum solid waste, among which preparing it into calcium carbonate is one of the main methods, but it still has some shortcomings. For example, in patent CN108408751A, ammonia water and phosphogypsum are mixed and CO is introduced into the mixture. 2 The gas is then filtered to obtain solid matter and ammonium sulfate solution. The solid matter is then repeated through the above steps until there is no change. The filtrate is heated to obtain calcium carbonate. However, this process is cumbersome and requires the use of multiple chemical reagents and the introduction of CO 2 To a certain extent, the gas will cause gas leakage and environmental impact. Patents CN116903017A and CN118289792A both use sodium gluconate solution as the extracting solution for calcium ions in phosphogypsum, and introduce CO into it. 2 Gas is used to obtain calcium carbonate. Although it reduces the preparation steps, it still requires the introduction of CO 2 Gases serve as reaction media, which often leads to the leakage of greenhouse gases.

[0005] In summary, the existing gypsum solid waste and microbial mineralization technologies have the following problems:

[0006] 1. The method of replacing traditional calcium sources in microbial mineralization technology is relatively simple and difficult to apply on a large scale;

[0007] 2. Gypsum solid waste occupies land resources, causes environmental pollution, and has low utilization rate;

[0008] 3. The process of preparing calcium carbonate from gypsum solid waste is complicated, with many chemical reagents and the introduction of CO 2 Gas poses a risk of leakage. Summary of the invention

[0009] The technical problem to be solved by the present invention is to overcome the problems pointed out in the background technology, that is, the purpose of the present invention is to provide a method for stimulating gypsum solid waste for microbial mineralization to generate calcium carbonate, which can realize the resource utilization of gypsum solid waste and replace the traditional calcium source in microbial mineralization technology, fully realizing the complementary advantages. After the gypsum solid waste is mineralized by microorganisms, calcium carbonate can be used as a green product for the resource utilization of gypsum solid waste and can also be a source of calcium carbonate for improving soil by microbial mineralization technology.

[0010] The object of the present invention is achieved by providing a method for stimulating gypsum solid waste to be used for microbial mineralization to produce calcium carbonate, comprising the following steps:

[0011] Step 1: Pretreatment of gypsum solid waste

[0012] Step 1.1, crushing the gypsum solid waste and passing it through a sieve with a pore size of 0.075 mm to 2 mm, then placing the sieved gypsum solid waste in an oven at a temperature of 45° C. to 55° C. for drying for 24 h to 48 h, taking out the dried gypsum solid waste powder and placing it in a container for standby use;

[0013] Step 2, Preparation of Calcium Source

[0014] Step 2.1, after preparing the activator and deionized water at a concentration of 0.5 mol / L to 1.5 mol / L, put them into a stirring device for a first stirring to obtain an activator solution; the first stirring rate is 700 rpm to 800 rpm, and the first stirring time is 5 min to 10 min;

[0015] Step 2.2, mixing the activator solution obtained in step 2.1 with the gypsum solid waste powder at a liquid-solid ratio of 5 to 20:1, and placing the mixture in a stirring device for a second stirring, wherein the second stirring rate is 700 rpm to 800 rpm, and the second stirring time is 25 min to 35 min;

[0016] Step 2.3, pouring the mixture of the activator solution treated in step 2.2 and the gypsum solid waste powder into a filter device with a pore size of 0.40 μm to 0.50 μm to obtain a leaching solution containing calcium ions, and removing insoluble impurities; the filtration time is 30 min to 60 min;

[0017] Step 2.4, mixing the leached solution from which the insoluble impurities of calcium ions are removed with urea to obtain an excited calcium source, the mass composition of which is 1000:12-15 in the above order;

[0018] Step 3, preparation of microbial culture liquid

[0019] Step 3.1, use the formula recommended by the American Type Culture Collection ATCC 1376 NH 4 -YE prepares the culture solution, then sterilizes the culture solution at 121°C to 123°C for 20min to 30min, and then places it on a clean bench for UV sterilization and ventilation, and waits for the culture solution to cool to room temperature before use;

[0020] Step 3.2, after the temperature of the culture solution drops to room temperature, take the culture solution into a container, add urease bacteria into the culture solution with a sterile pipette to obtain a bacterial solution, the volume ratio of urease bacteria to the culture solution is 1:100, and place the bacterial solution in a constant temperature shaking box for culturing; the constant temperature shaking box has an oscillation frequency of 160 rpm to 200 rpm, a temperature of 28° C. to 32° C., and a culturing time of 24 h to 48 h;

[0021] Step 3.3, after the culture is completed, measure the absorbance of the bacterial solution at a wavelength of 600nm, i.e., the OD600 value, and take out the bacterial solution when OD600=1.6-1.8 for later use;

[0022] The bacterial solution that has completed the above treatment is recorded as microbial bacterial solution;

[0023] Step 4: Preparation of calcium carbonate from microbial culture liquid and stimulating calcium source

[0024] Step 4.1, the microbial liquid and the stimulated calcium source are mixed evenly in a volume ratio of 1:1 to 8, and then the mixed solution is placed in a constant temperature incubator for static reaction, the temperature of the constant temperature incubator is 28°C to 32°C, and the reaction time is 48h to 56h;

[0025] Step 4.2, after the reaction is completed, pour the above mixed solution into a filtration device, filter to obtain a solid calcium carbonate product, then put the solid calcium carbonate product into an oven for drying, and grind the dried calcium carbonate solid through a 2mm to 1mm sieve to obtain the desired calcium carbonate product; the pore size of the filter membrane in the filtration device is 0.17μm to 0.27μm, the oven temperature is 100℃ to 110℃, and the baking time is 12h to 36h.

[0026] Preferably, the gypsum solid waste is any one of phosphogypsum, titanium gypsum and desulfurized gypsum.

[0027] Preferably, the stimulant is any one of sodium chloride, potassium chloride, ammonium chloride, ammonium acetate and sodium gluconate.

[0028] Preferably, the American Type Culture Collection recommends ATCC 1376 NH 4 -YE prepared culture solution composition: 20g yeast extract, 10g (NH 4 ) 2 SO 4, 0.13 mol / L Tris Buffer, add deionized water to 1 L, and adjust the culture medium pH to 9.0 with 1 mol / L HCl.

[0029] Preferably, the urease-producing bacteria is one of Bacillus pasteurianus, Sporosarcina pastoris, and Bacillus subtilis.

[0030] Preferably, the drying in step 4.2 means that the water content of the calcium carbonate product is less than 2%.

[0031] Compared with the prior art, the beneficial effects of the present invention include:

[0032] 1. The process flow of the present invention is simple. The present invention uses phosphogypsum as raw material and can directly extract calcium ions from gypsum solid waste using organic salts or inorganic salts. The reaction process is simple and the energy consumption is low.

[0033] 2. The present invention realizes the resource utilization of industrial waste. In the present invention, gypsum solid waste is a polluting industrial waste. Gypsum solid waste is introduced into microbial mineralization technology, and the generated calcium carbonate can be used as the green recycling of industrial waste.

[0034] 3. The present invention achieves the replacement of the traditional calcium source of MICP. The calcium ion solution after the gypsum solid waste is stimulated by an activator is used as the calcium source of the microbial mineralization technology, which can effectively utilize solid waste while reducing the application cost of the technology.

[0035] 4. The present invention is environmentally friendly to a certain extent. The present invention comprehensively utilizes gypsum solid waste, reduces land resource occupation, reduces environmental pollution, and has better environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a flow chart of the present invention.

[0037] Figure 2 This is a diagram of calcium carbonate precipitation of microbial mineralized phosphogypsum in an embodiment of the present invention.

[0038] Figure 3 This is the XRD diagram of calcium carbonate produced by microbial mineralization of phosphogypsum in an embodiment of the present invention. DETAILED DESCRIPTION

[0039] The method of the present invention is further described in detail below with reference to the embodiments.

[0040] Embodiment 1:

[0041] Figure 1 It is a flow chart of the present invention. From this figure, it can be seen that the present invention includes the following steps:

[0042] Step 1: Pretreatment of gypsum solid waste

[0043] Step 1.1, crush the gypsum solid waste and pass it through a sieve with an aperture of 0.075mm to 2mm, then place the sieved gypsum solid waste in an oven at a temperature of 45°C to 55°C for drying for 24h to 48h, take out the dried gypsum solid waste powder and put it into a container for later use.

[0044] The gypsum solid waste is any one of phosphogypsum, titanium gypsum and desulfurized gypsum.

[0045] In this embodiment, the gypsum solid waste is phosphogypsum, the aperture of the sieve is 2 mm, the oven temperature is 55° C., and the baking time is 48 h.

[0046] Step 2, Preparation of Calcium Source

[0047] Step 2.1, after preparing the activator and deionized water at a concentration of 0.5 mol / L to 1.5 mol / L, put them into a stirring device for a first stirring to obtain an activator solution; the first stirring rate is 700 rpm to 800 rpm, and the first stirring time is 5 min to 10 min;

[0048] Step 2.2, mixing the activator solution obtained in step 2.1 with the gypsum solid waste powder at a liquid-solid ratio of 5 to 20:1, and placing the mixture in a stirring device for a second stirring, wherein the second stirring rate is 700 rpm to 800 rpm, and the second stirring time is 25 min to 35 min;

[0049] Step 2.3, pouring the mixture of the activator solution treated in step 2.2 and the gypsum solid waste powder into a filter device with a pore size of 0.40 μm to 0.50 μm to obtain a leaching solution containing calcium ions, and removing insoluble impurities; the filtration time is 30 min to 60 min;

[0050] Step 2.4, mixing the leached solution from which the insoluble impurities of calcium ions are removed with urea to obtain an excited calcium source, the mass composition of which is 1000:12-15 in the above order.

[0051] The excitant is any one of sodium chloride, potassium chloride, ammonium chloride, ammonium acetate and sodium gluconate. In the present embodiment, the excitant is sodium gluconate.

[0052] In this embodiment, the concentration of the activator is 1 mol / L, the first stirring rate is 800 rpm, and the first stirring time is 8 minutes.

[0053] In this embodiment, the activator solution and the gypsum solid waste powder are mixed at a liquid-to-solid ratio of 20:1, the second stirring rate is 800 rpm, the second stirring time is 30 minutes, and the filtration time is 60 minutes.

[0054] In this embodiment, the pore size of the filter in the filter device is 0.45 μm, and the leaching solution for removing calcium ions from insoluble impurities is mixed with urea at a ratio of 1000:12.5.

[0055] Step 3, preparation of microbial culture liquid

[0056] Step 3.1, use the formula recommended by the American Type Culture Collection ATCC 1376NH 4 -YE prepares the culture solution, then sterilizes the culture solution at 121°C to 123°C for 20min to 30min, and then places it on a clean bench for UV sterilization and ventilation, and waits for the culture solution to cool to room temperature before use;

[0057] Step 3.2, after the temperature of the culture solution drops to room temperature, take the culture solution into a container, add urease bacteria into the culture solution with a sterile pipette to obtain a bacterial solution, the volume ratio of urease bacteria to the culture solution is 1:100, and place the bacterial solution in a constant temperature shaking box for culturing; the constant temperature shaking box has an oscillation frequency of 160 rpm to 200 rpm, a temperature of 28° C. to 32° C., and a culturing time of 24 h to 48 h;

[0058] Step 3.3, after the culture is completed, measure the absorbance of the bacterial solution at a wavelength of 600nm, i.e., OD600 value, and take out the bacterial solution for use when OD600 = 1.6-1.8;

[0059] The bacterial solution that has completed the above treatment is recorded as microbial bacterial solution.

[0060] The American Type Culture Collection recommends the formula ATCC 1376NH 4 -YE prepared culture solution composition: 20g yeast extract, 10g (NH 4 ) 2 SO 4 , 0.13 mol / L Tris Buffer, add deionized water to 1 L, and adjust the culture medium pH to 9.0 with 1 mol / L HCl.

[0061] The urease-producing bacteria is one of Bacillus pasteurianus, Bacillus sporosarcina, and Bacillus subtilis. In this embodiment, the urease-producing bacteria is Bacillus pasteurianus, and its American Type Culture Collection number is ATCC11859.

[0062] In this embodiment, the culture solution is sterilized at 121° C. for 30 min and is then cooled to room temperature for later use.

[0063] In this embodiment, the oscillation frequency is 180 rpm, the temperature of the constant temperature oscillation box is 30° C., and the incubation time is 48 h.

[0064] In this embodiment, OD600=1.7.

[0065] Step 4: Preparation of calcium carbonate from microbial culture liquid and stimulating calcium source

[0066] Step 4.1, the microbial liquid and the stimulated calcium source are mixed evenly in a volume ratio of 1:1 to 8, and then the mixed solution is placed in a constant temperature incubator for static reaction, the temperature of the constant temperature incubator is 28°C to 32°C, and the reaction time is 48h to 56h;

[0067] Step 4.2, after the reaction is completed, pour the above mixed solution into a filtration device, filter to obtain a solid calcium carbonate product, then put the solid calcium carbonate product into an oven for drying, and grind the dried calcium carbonate solid through a 2mm to 1mm sieve to obtain the desired calcium carbonate product; the pore size of the filter membrane in the filtration device is 0.17μm to 0.27μm, the oven temperature is 100℃ to 110℃, and the baking time is 12h to 36h.

[0068] In this embodiment, the drying in step 4.2 means that the water content of the calcium carbonate product is less than 2%.

[0069] In this embodiment, the volume ratio of the microbial liquid to the calcium source after stimulation is 1:4, the temperature of the constant temperature incubator is 30° C., and the reaction time is 48 hours.

[0070] In this embodiment, the oven temperature is 105° C., the baking time is 24 h, and the pore size of the filter membrane is a 2 mm sieve.

[0071] Embodiment 2:

[0072] In this embodiment, the activator is sodium chloride, and other aspects are exactly the same as those in Embodiment 1.

[0073] Embodiment 3:

[0074] In this embodiment, the activator is potassium chloride, and other aspects are exactly the same as those in Example 1.

[0075] Embodiment 4:

[0076] In this embodiment, the activator is ammonium chloride, and other aspects are exactly the same as those in Embodiment 1.

[0077] Embodiment 5:

[0078] In this embodiment, the activator is ammonium acetate, and other aspects are exactly the same as those in Embodiment 1.

[0079] Comparative Example 1:

[0080] Instead of using the calcium ion solution of activated phosphogypsum as the calcium source, only 0.25 mol / L calcium chloride solution is selected as the calcium source, mixed with the bacterial solution in a ratio of 1:4, and placed in a constant temperature and humidity curing box at a temperature of 30°C for reaction for 48 hours. The mixed solution is then filtered with a filtration device with a 0.22-micron filter membrane, and the obtained calcium carbonate solid is placed in an oven at 105°C for drying for 24 hours, and finally crushed through a 2 mm sieve.

[0081] Figure 2 This is a graph of calcium carbonate precipitation of microbial mineralized phosphogypsum in this embodiment. As can be seen from the figure, compared with the traditional microbial mineralization of calcium chloride to produce calcium carbonate precipitation, different stimulants can stimulate the phosphogypsum and microbial mineralization reaction to produce calcium carbonate precipitation, but the calcium carbonate precipitation content under different stimulants is slightly different. The results show that microbial mineralization technology can stimulate phosphogypsum to produce calcium carbonate precipitation, proving the feasibility of this method.

[0082] Figure 3 This is the XRD diagram of calcium carbonate produced by microbial mineralization of phosphogypsum in the embodiment of the present invention. Figure 2 The mineral composition analysis of the calcium carbonate precipitate generated in the process shows that compared with the XRD results of the traditional microbial mineralization of calcium chloride to generate calcium carbonate precipitate, the XRD results of the calcium carbonate precipitate generated by the reaction of phosphogypsum with different stimulants and microbial mineralization are consistent, all of which are pure phase calcite. The results show that the use of microbial mineralization of phosphogypsum can generate calcium carbonate crystals, thereby effectively recycling the solid waste phosphogypsum in a green way.

Claims

1. A method for stimulating gypsum solid waste to be used for microbial mineralization to produce calcium carbonate, characterized in that: The following steps are involved: Step 1: Pretreatment of gypsum solid waste Step 1.1, crushing the gypsum solid waste and passing it through a sieve with a pore size of 0.075 mm to 2 mm, then placing the sieved gypsum solid waste in an oven at a temperature of 45° C. to 55° C. for drying for 24 h to 48 h, taking out the dried gypsum solid waste powder and placing it in a container for standby use; Step 2, Preparation of Calcium Source Step 2.1, after preparing the activator and deionized water at a concentration of 0.5 mol / L to 1.5 mol / L, put them into a stirring device for a first stirring to obtain an activator solution; the first stirring rate is 700 rpm to 800 rpm, and the first stirring time is 5 min to 10 min; Step 2.2, mixing the activator solution obtained in step 2.1 with the gypsum solid waste powder at a liquid-solid ratio of 5 to 20:1, and placing the mixture in a stirring device for a second stirring, wherein the second stirring rate is 700 rpm to 800 rpm, and the second stirring time is 25 min to 35 min; Step 2.3, pouring the mixture of the activator solution treated in step 2.2 and the gypsum solid waste powder into a filter device with a pore size of 0.40 μm to 0.50 μm to obtain a leaching solution containing calcium ions, and removing insoluble impurities; The filtration time is 30min to 60min; Step 2.4, mixing the leached solution from which the insoluble impurities of calcium ions are removed with urea to obtain an excited calcium source, the mass composition of which is 1000:12-15 in the aforementioned order; Step 3, preparation of microbial culture liquid Step 3.1, prepare the culture medium using the formula ATCC 1376NH4-YE recommended by the American Type Culture Collection, sterilize the culture medium at 121°C to 123°C for 20min to 30min, place it on a clean bench for ultraviolet sterilization and ventilation, and wait for the temperature of the culture medium to drop to room temperature for use; Step 3.2, after the temperature of the culture solution drops to room temperature, take the culture solution into a container, add urease bacteria into the culture solution with a sterile pipette to obtain a bacterial solution, the volume ratio of urease bacteria to the culture solution is 1:100, and place the bacterial solution in a constant temperature shaking box for culturing; the constant temperature shaking box has an oscillation frequency of 160 rpm to 200 rpm, a temperature of 28° C. to 32° C., and a culturing time of 24 h to 48 h; Step 3.3, after the culture is completed, measure the absorbance of the bacterial solution at a wavelength of 600nm, i.e., the OD600 value, and take out the bacterial solution when OD600=1.6-1.8 for later use; The bacterial solution that has completed the above treatment is recorded as microbial bacterial solution; Step 4: Preparation of calcium carbonate from microbial culture liquid and stimulating calcium source Step 4.1, the microbial liquid and the stimulated calcium source are mixed evenly in a volume ratio of 1:1 to 8, and then the mixed solution is placed in a constant temperature incubator for static reaction, the temperature of the constant temperature incubator is 28°C to 32°C, and the reaction time is 48h to 56h; Step 4.2, after the reaction is completed, pour the above mixed solution into a filtration device, filter to obtain a solid calcium carbonate product, then put the solid calcium carbonate product into an oven for drying, and grind the dried calcium carbonate solid through a 2mm to 1mm sieve to obtain the desired calcium carbonate product; the pore size of the filter membrane in the filtration device is 0.17μm to 0.27μm, the oven temperature is 100℃ to 110℃, and the baking time is 12h to 36h.

2. The method for stimulating gypsum solid waste to produce calcium carbonate through microbial mineralization according to claim 1, characterized in that: The gypsum solid waste is any one of phosphogypsum, titanium gypsum and desulfurized gypsum.

3. The method for stimulating gypsum solid waste to produce calcium carbonate through microbial mineralization according to claim 1, characterized in that: The stimulant is any one of sodium chloride, potassium chloride, ammonium chloride, ammonium acetate and sodium gluconate.

4. The method for stimulating gypsum solid waste to produce calcium carbonate by microbial mineralization according to claim 1, characterized in that: The composition of the culture solution prepared by the American Type Culture Collection's recommended formula ATCC 1376NH4-YE is: 20g yeast extract, 10g (NH4)2SO4, 0.13mol / L Tris Buffer, deionized water is added to 1L, and the pH of the culture solution is adjusted to 9.0 with 1mol / L HCl.

5. The method for stimulating gypsum solid waste to produce calcium carbonate through microbial mineralization according to claim 1, characterized in that: The urease-producing bacteria is one of Bacillus pasteurianus, Sporosarcina pastoris and Bacillus subtilis.

6. The method for stimulating gypsum solid waste to produce calcium carbonate through microbial mineralization according to claim 1, characterized in that: The drying in step 4.2 means that the water content of the calcium carbonate product is less than 2%.

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