Preparation method and application of magnetic biochar coupling degradation bacteria immobilized gel microspheres

Abstract

The application relates to a preparation method and application of a magnetic biochar coupling degradation bacteria immobilized gel microsphere, and relates to the technical field of water and soil treatment. The application is aimed at solving the problems of competition of local microorganisms, severe environmental conditions and unstable genomes when the microorganisms are used alone to degrade atrazine in soil, and the difficulty in separating the microorganisms and carbon materials from the soil. Method: sodium alginate is added to deionized water, and is fully dissolved through ultrasonic stirring; after high-temperature sterilization, the sodium alginate solution is cooled to room temperature; magnetic biochar and bacterial suspension are added to the sodium alginate solution to obtain an MBC-cell mixture; the MBC-cell mixture is added dropwise to the sterilized calcium chloride solution; after calcification for 24-24.5 hours, the magnetic biochar coupling degradation bacteria immobilized gel microsphere is obtained after being washed for 3-5 times. The application can obtain a preparation method and application of a magnetic biochar coupling degradation bacteria immobilized gel microsphere.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of water and soil treatment, and particularly relates to a preparation method and application of a magnetic biochar coupled degradation bacterium immobilized gel microsphere. BACKGROUND

[0002] Atrazine (ATZ) is a representative triazine herbicide and one of the most commonly used herbicides in China. It is low cost and highly efficient, and is applied in corn, sorghum and sugarcane fields. Due to its mobility, long-term persistence and difficulty in natural degradation, it can still be detected in the environment after several years of application. Therefore, the accumulation of ATZ in soil can easily cause phytotoxicity to subsequent sensitive crops such as soybean, wheat and rice. At the same time, the residual ATZ in soil can be absorbed by plant roots and combined with the plastoquinone binding protein in plant photosystem II, resulting in oxidative damage and eventually leading to plant death. In addition, ATZ also has ecotoxicological effects on biological processes such as soil enzyme activity, soil microbial composition and microbial diversity, thereby affecting its effectiveness on plants. Therefore, it is crucial to develop an efficient method to remove residual ATZ in soil.

[0003] Currently, there are many methods to remove ATZ, including zero-valent metal oxidation degradation, photolysis, advanced oxidation and bioremediation. Among them, bioremediation based on microbial degradation has attracted widespread attention due to its environmental friendliness and complete degradation. A large number of microorganisms (bacteria and fungi) capable of degrading ATZ have been isolated and identified, such as Pseudomonas, Arthrobacter, Aspergillus fumigatus and Fusarium roseum. However, although free cells of microorganisms can effectively degrade ATZ under laboratory conditions, many factors limit the survival and bioaugmentation efficiency of ATZ during in-situ remediation, including competition from indigenous microorganisms, severe environmental conditions and instability of the genome. Various toxic and harmful substances in soil, such as heavy metals, organic matter and synthetic chemicals, can inhibit the growth of bacteria, and local microorganisms in soil can also compete with bacteria for nutrients. Therefore, it is necessary to develop a suitable carrier to avoid direct contact between bacteria and toxic and harmful substances.

[0004] Immobilization techniques, especially encapsulation of specific degrading bacteria in biopolymer gels or hydrogels, have been of interest due to the removal of organic pollutants through adsorption and biodegradation processes. Sodium alginate (SA) is a low-cost polysaccharide with natural biocompatibility and biodegradability, which has been widely used for microbial bio-embedding. Immobilization of microbial cells can improve the survival ability and drug resistance of bacteria under extreme conditions. Therefore, the preparation of microbial gel microspheres may be a promising strategy to improve bacterial activity. However, with the improvement of bacterial activity, the contact area of bacteria with soil pollutants may be reduced. Therefore, functional materials are needed to improve the adsorption capacity of ATZ during the embedding process. Biochar (BC) is a stable carbonaceous material, which has been used to remove organic pollutants due to its huge surface area and active functional groups. However, the adsorption capacity and recovery performance of the original BC have certain limitations. SUMMARY

[0005] The purpose of the present application is to solve the problems of competition with indigenous microorganisms, severe environmental conditions and genomic instability when microorganisms are used alone to degrade atrazine in soil, and the difficulty of separating microorganisms and carbon materials from soil, and to provide a preparation method and application of a magnetic biochar coupled degradation bacteria immobilized gel microsphere.

[0006] A preparation method of a magnetic biochar coupled degradation bacteria immobilized gel microsphere, which is carried out according to the following steps:

[0007] Step one, preparation of bacterial suspension:

[0008] Acinetobacter lwoffii strain DNS32 is inoculated into inorganic salt medium at an inoculation amount of 1-1.2%; after shaking culture at a temperature of 29.5-30.5℃ for 47-49h, the cells are harvested at the logarithmic phase, and centrifuged at a speed of 10000-10005r / min for 5-5.5min to obtain wet cells, which are then resuspended with sterile water to obtain a bacterial suspension;

[0009] Step two, preparation of magnetic biochar:

[0010] Corn straw powder is placed in a tube furnace and pyrolyzed at 500-505℃ under a nitrogen atmosphere for 2-2.05h to obtain biochar; the biochar is mixed with a ferric salt mixed solution, then ammonia water is added, and the pH is adjusted to 11-12, and then mechanically stirred for 60-65min to obtain a ferric-carbon precipitate; the mass of the corn straw powder, the volume of the ferric salt mixed solution and the volume of the ammonia water are (10-10.5)g:(398-402)mL:(9.5-10.5)mL; after washing, drying and grinding the ferric-carbon precipitate, a magnetic biochar is obtained;

[0011] Step three, preparation of magnetic biochar coupled degradation bacteria immobilized gel microspheres:

[0012] Sodium alginate is added to deionized water, ultrasonic stirring is carried out until complete dissolution, and after high-temperature sterilization, it is cooled to room temperature to obtain a sodium alginate solution; the magnetic biochar and bacterial suspension are added to the sodium alginate solution to obtain an MBC-cell mixed solution, the mass ratio of the magnetic biochar, wet cells in the bacterial suspension and sodium alginate in the sodium alginate solution is (2.0-2.2) g:(2.0-2.2) g:(1.95-2.05) g; the MBC-cell mixed solution is added dropwise to the sterilized calcium chloride solution, and after calcification for 24-24.5 h, the immobilized microspheres are obtained, the volume ratio of the MBC-cell mixed solution to the sterilized calcium chloride solution is (98-100):(198-200); the immobilized microspheres are washed for 3-5 times to obtain magnetic biochar coupled degradation bacteria immobilized gel microspheres.

[0013] The application of a kind of magnetic biochar coupled degradation bacteria immobilized gel microspheres, the magnetic biochar coupled degradation bacteria immobilized gel microspheres are used to remove atrazine.

[0014] The beneficial effects of the present application are:

[0015] The present application uses sodium alginate to bio-embed magnetic biochar and DNS32 degrading bacteria, successfully prepares magnetic biochar coupled degradation bacteria immobilized gel microspheres, which can effectively improve the tolerance and survival ability of DNS32 degrading bacteria in water / soil environment, and at the same time, DNS32 degrading bacteria still have good activity in a larger pH range, lower / higher environmental temperature and higher pollutant stress, so as to efficiently remove ATZ. In addition, the embedding process is combined with magnetic biochar, which effectively solves the problems of traditional adsorbents / microorganisms, such as difficult to recover, easy to cause secondary pollution to the environment, in the process of soil application. The prepared magnetic biochar coupled degradation bacteria immobilized gel microspheres provide a promising remediation method for realizing efficient removal and recovery of atrazine in water and soil.

[0016] The present application can obtain a preparation method and application of magnetic biochar coupled degradation bacteria immobilized gel microspheres. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The figure shows the influence of dosage on the removal of ATZ by DNS32, MBC-P and DMBC-P in Example 1, a represents DNS32, b represents MBC-P, and c represents DMBC-P;

[0018] Figure 2Figures showing the effect of initial pH on the performance of DNS32, MBC-P and DMBC-P in removing ATZ in Example 1, a represents DNS32, b represents MBC-P, and c represents DMBC-P;

[0019] Figure 3 Figures showing the effect of initial pH on the performance of DNS32, MBC-P and DMBC-P in removing ATZ in Example 1, a represents DNS32, b represents MBC-P, and c represents DMBC-P;

[0020] Figure 4 Figures showing the effect of initial pH on the performance of DNS32, MBC-P and DMBC-P in removing ATZ in Example 1, a represents DNS32, b represents MBC-P, and c represents DMBC-P;

[0021] Figure 5 Figures showing the effect of different remediation agents on the remediation of atrazine-contaminated soil, a represents CK, b represents DNS32, c represents MBC-P, and d represents DMBC-P. DETAILED DESCRIPTION

[0022] Specific embodiment one: the preparation method of the magnetic biochar coupled degradation bacteria immobilized gel microspheres in this embodiment is carried out according to the following steps:

[0023] Step one, preparation of bacterial suspension:

[0024] The Acinetobacter lwoffii strain DNS32 is inoculated into the inorganic salt culture medium at an inoculation amount of 1-1.2%; after being cultured at a temperature of 29.5-30.5℃ for 47-49h, the cells are harvested at the logarithmic phase, and the wet cells are obtained by centrifugation at a speed of 10000-10005r / min for 5-5.5min; the bacterial cells are resuspended with sterile water to obtain the bacterial suspension;

[0025] Step two, preparation of magnetic biochar:

[0026] The corn straw powder is placed in a tube furnace and pyrolyzed at 500-505℃ under a nitrogen atmosphere for 2-2.05h to obtain biochar; the biochar is mixed with a ferrous salt mixed solution, then ammonia water is added, the pH is adjusted to 11-12, and mechanical stirring is performed for 60-65min to obtain a ferrocyanide precipitate; the mass of the corn straw powder, the volume of the ferrous salt mixed solution, and the volume of the ammonia water are in the ratio of (10-10.5)g:(398-402)mL:(9.5-10.5)mL; after washing, drying and grinding, the ferrocyanide precipitate is obtained to obtain the magnetic biochar;

[0027] Step three, preparation of magnetic biochar coupled degradation bacteria immobilized gel microspheres:

[0028] Sodium alginate was added into deionized water, and ultrasonic stirring was performed until it was completely dissolved, and then the solution was sterilized at high temperature and cooled to room temperature to obtain a sodium alginate solution; magnetic biochar and bacterial suspension were added into the sodium alginate solution to obtain an MBC-cell mixture, and the mass ratio of the magnetic biochar, wet cells in the bacterial suspension and sodium alginate in the sodium alginate solution was (2.0-2.2) g:(2.0-2.2) g:(1.95-2.05) g; the MBC-cell mixture was added dropwise into a sterilized calcium chloride solution, and after calcification for 24-24.5 h, immobilized microspheres were obtained, and the volume ratio of the MBC-cell mixture to the sterilized calcium chloride solution was (98-100):(198-200); the immobilized microspheres were washed for 3-5 times to obtain magnetic biochar-coupled degradation bacteria immobilized gel microspheres.

[0029] Fe3O4 has the advantages of stable chemical properties, high adsorption capacity and good saturation magnetization, and the use of magnetized BC can not only improve its adsorption capacity for pollutants, but also separate the material from the soil to avoid secondary pollution and realize the reuse of the material. Therefore, the synthesis of magnetic biochar-coupled degradation bacteria immobilized gel microspheres can make up for the shortcomings of each other and achieve efficient removal of organic pollutants.

[0030] Specific implementation method two: the difference between this implementation method and specific implementation method one is that the inorganic salt medium in step one is composed of 1.55-1.65 g / L K2HPO4, 0.35-0.45 g / L KH2PO4, 0.15-0.25 g / L MgSO4, 0.08-0.12 g / L NaCl, 2.9-3.1 g / L glucose and 98-102 g / L ATZ, and the inorganic salt medium is sterilized at 121℃ for 30 min before use.

[0031] The other steps are the same as those in specific implementation method one.

[0032] Specific implementation method three: the difference between this implementation method and specific implementation method one or two is that 1-1.05 mL of sterile water is used to resuspend the bacteria in step one.

[0033] The other steps are the same as those in specific implementation method one or two.

[0034] Specific implementation method four: the difference between this implementation method and any one of specific implementation methods one to three is that the corn straw powder in step two is prepared according to the following steps: the corn straw is washed, dried, ground into a powder with a particle size of 2.0-2.05 mm, and the corn straw powder is obtained.

[0035] The other steps are the same as those in specific implementation methods one to three.

[0036] Embodiment five: the difference between this embodiment and one of embodiments one to four is that in step two, the corn straw powder is heated to 500℃ at a heating rate of 10℃ / min.

[0037] The other steps are the same as embodiments one to four.

[0038] Embodiment six: the difference between this embodiment and one of embodiments one to five is that in step two, the iron salt mixed solution is mixed by FeSO4 solution and FeCl3 solution, the molar ratio of Fe 2+ in FeSO4 solution to Fe 3+ in FeCl3 is 2:1, and the molar concentration of Fe 2+ is 0.1 mol / L.

[0039] The other steps are the same as embodiments one to five.

[0040] Embodiment seven: the difference between this embodiment and one of embodiments one to six is that in step three, the mass of sodium alginate to the volume of deionized water is (1.95-2.05)g:(100-102)mL.

[0041] The other steps are the same as embodiments one to six.

[0042] Embodiment eight: the difference between this embodiment and one of embodiments one to seven is that in step three, the mass fraction of calcium chloride in the sterilized calcium chloride solution is 1.95-2.05%.

[0043] The other steps are the same as embodiments one to seven.

[0044] Embodiment nine: the difference between this embodiment and one of embodiments one to eight is that in step three, the immobilized microspheres are washed with a sodium chloride solution with a concentration of 0.9-0.95%.

[0045] The other steps are the same as embodiments one to eight.

[0046] Embodiment ten: an application of a magnetic biochar-coupled degradation bacteria immobilized gel microsphere, the magnetic biochar-coupled degradation bacteria immobilized gel microsphere is used for removing atrazine.

[0047] The following examples are used to verify the beneficial effects of the present application:

[0048] Example 1: a preparation method of a magnetic biochar-coupled degradation bacteria immobilized gel microsphere, which is carried out according to the following steps:

[0049] Step one, preparation of a bacteria suspension:

[0050] Acinetobacter lwoffii strain DNS32 was inoculated into mineral salt medium (MSM) at 1% inoculation amount, and after being cultured at 30℃ for 48h, the cells were harvested at the logarithmic phase, and the optical density at 600nm was measured to be 0.9-1.0. The cells were centrifuged at 10000r / min for 5min to obtain wet cells, and then the cells were resuspended with 1-1.05mL sterile water to obtain a bacterial suspension.

[0051] The Acinetobacter lwoffii strain DNS32 is a strain capable of growing with atrazine as the sole nitrogen source, and has been preserved in China General Microbiological Culture Collection Center with the preservation number of CGMCC NO.5365.

[0052] The mineral salt medium is composed of 1.6g / L K2HPO4, 0.4g / L KH2PO4, 0.2g / L MgSO4, 0.1g / L NaCl, 3g / L glucose and 100g / L ATZ, and is made up with deionized water. The mineral salt medium is sterilized at 121℃ for 30min before use.

[0053] Step two, preparation of magnetic biochar:

[0054] The corn stalks were washed, dried and ground into 2.0-2.05mm powder to obtain corn stalk powder. The corn stalk powder was placed in a tube furnace and heated to 500℃ at a heating rate of 10℃ / min, and then pyrolyzed at 500℃ under nitrogen atmosphere for 2h to obtain biochar (BC). 10g of the biochar was mixed with 400mL of iron salt mixed solution, and then 10mL of ammonia water was added, and the pH was adjusted to 12. After mechanical stirring for 60min, an iron-carbon precipitate was obtained. The iron salt mixed solution was prepared by mixing FeSO4 solution and FeCl3 solution, and the molar ratio of Fe 2+ in the FeSO4 solution to Fe 3+ in the FeCl3 solution was 2:1, and the molar concentration of Fe 2+ was 0.1mol / L. After washing, drying and grinding, the magnetized iron-carbon precipitate was obtained as magnetic biochar (MBC).

[0055] Step three, preparation of magnetic biochar-coupled degradation bacteria immobilized gel microspheres:

[0056] 2 g of sodium alginate was added to 100 mL of deionized water, and ultrasonic stirring was performed until complete dissolution. After high-temperature sterilization, the solution was cooled to room temperature to obtain a sodium alginate solution. 2 g of magnetic biochar and a bacterial suspension containing 2 g of wet cells were added to the sodium alginate solution to obtain an MBC-cell mixture. The MBC-cell mixture was added dropwise to 200 mL of sterilized calcium chloride solution (w / v), and the mass fraction of calcium chloride was 2%. After calcification for 24 h, immobilized microspheres were obtained. The immobilized microspheres were washed three times with a 0.9% sodium chloride solution to obtain magnetic biochar-coupled degradation bacteria immobilized gel microspheres (DMBC-P), which were stored in a 4°C refrigerator for later use. Magnetic biochar immobilized microspheres (MBC-P) without DNS32 cells were prepared in the same way as the control.

[0057] Test section:

[0058] The DNS32 bacterial suspension, magnetic biochar immobilized gel microspheres, and magnetic biochar-coupled degradation bacteria immobilized gel microspheres prepared in Example 1 were used to perform experiments on the effects of dosage, initial pH value, initial ATZ concentration, and temperature on ATZ removal, as well as ATZ pollution remediation in soil. The specific conclusions are as follows:

[0059] 1. Dosage:

[0060] Removal process: 100-102 mg / L of ATZ contaminated solution was prepared, and 1%, 2%, 3%, 4%, and 5% dosages of DNS32, MBC-P, and DMBC-P were added to the contaminated solution after high-pressure sterilization. The solution was incubated at 30°C in a constant-temperature shaker for 48 h.

[0061] Figure 1 The figure shows the effects of dosage on the removal of ATZ by DNS32, MBC-P, and DMBC-P in Example 1. a represents DNS32, b represents MBC-P, and c represents DMBC-P. As shown in Figure 1 the figure, when the dosage is in the range of 1-3%, the removal rate of DMBC-P is the highest compared to DNS32 and MBC-P. As the dosage increases, the removal rate of MBC-P gradually increases, but only by about 16%, while the removal rates of DNS32 and DMBC-P remain basically the same. When the dosage is 3%, the removal rate of DMBC-P is about 99%, and it is basically the same as the removal rate when the dosage is 4% and 5%, indicating that a smaller dosage can also have the same removal effect on ATZ, which reflects its environmental friendliness.

[0062] 2. pH value:

[0063] Removal process: 100-102 mg / L ATZ contaminated solution was prepared, and the pH value of the solution was adjusted to 3.3, 4.3, 5.3, 6.3 and 7.3 respectively by using 1 mol / L HCl, and 3% dosage of DNS32, MBC-P and DMBC-P were added to the contaminated solution after high pressure sterilization. Under the condition of 30℃, the culture was shaken in a constant temperature shaker for 48h.

[0064] Figure 2 The figure shows the effect of initial pH value on the removal of ATZ by DNS32, MBC-P and DMBC-P in Example 1, a represents DNS32, b represents MBC-P, and c represents DMBC-P; as shown in Figure 2 The optimal growth pH value of DNS32 is 7.3, and as the pH value decreases, the degradation rate of ATZ by the degrading bacteria DNS32 also gradually decreases to below 60%, which is because the degrading bacteria DNS32 is a neutral and slightly alkaline bacteria, and therefore the growth of DNS32 is not conducive in acidic conditions. The removal rate of ATZ by the DMBC-P system is not only the best at pH 7.3, but also significantly higher than that of DNS32 and MBC-P system at pH 3.3-6.3, maintaining at 75-99%. It is proved that the use of SA for embedding immobilization in the present application improves the activity of the bacteria under the stress of adverse environmental factors from the outside, and at the same time improves the removal performance of the immobilized microspheres to ATZ.

[0065] 3. Initial concentration:

[0066] Removal process: 30-33 mg / L, 60-63 mg / L, 100-103 mg / L, 120-123 mg / L and 140-143 mg / L ATZ contaminated solution was prepared respectively, and 3% dosage of DNS32, MBC-P and DMBC-P was added to the contaminated solution after high pressure sterilization. Under the condition of 30℃, the culture was shaken in a constant temperature shaker for 48h.

[0067] Figure 3 The figure shows the effect of initial concentration of ATZ on the removal of ATZ by DNS32, MBC-P and DMBC-P in Example 1, a represents DNS32, b represents MBC-P, and c represents DMBC-P; as shown in Figure 3As shown, the removal rate of MBC-P system for ATZ gradually increased with the increase of initial concentration and finally reached adsorption equilibrium, with the removal rate being about 21%-22%, which was caused by the limited specific surface area and pore structure. Meanwhile, when the concentration was low, the free bacteria DNS32 had good removal performance for ATZ, but ATZ had a certain stress on the bacteria, so that the removal rate of ATZ decreased obviously from more than 98% to less than 50% with the increase of ATZ concentration. The removal effect of DMBC-P for ATZ remained the best at each concentration, being always more than 90% and being up to 99% at the highest. It is proved that compared with DNS32, the removal performance of DMBC-P in the application for ATZ has a certain promoting effect.

[0068] 4. Temperature:

[0069] Removal process: 100-102 mg / L ATZ contaminated solution was prepared, and after high-pressure sterilization, 3% dosage of DNS32, MBC-P and DMBC-P were added into the contaminated solution respectively, and then the culture was shaken in a constant temperature shaker at 10℃, 20℃, 30℃, 40℃ and 50℃ for 48 h.

[0070] Figure 4 The figure shows the influence of temperature on the removal performance of DNS32, MBC-P and DMBC-P for ATZ in Example 1, a represents DNS32, b represents MBC-P, and c represents DMBC-P. Figure 4 As shown, overall, with the increase of temperature, the removal of ATZ by DNS32, MBC-P and DMBC-P three systems showed a trend of first increasing and then decreasing. Among them, between 10-30℃, the removal performance of DNS32 for ATZ was relatively good, being about 35-80%; while at 40-50℃, the removal rate decreased greatly, being about 25-30%, which was because the degradation bacteria of DNS32 was a low-temperature tolerant bacteria, and compared with high-temperature condition, low-temperature was more conducive to the growth and reproduction of the strain, and when the temperature was too high, it would inhibit the growth of bacteria and even cause the death of part of the cells. While DMBC-P had high removal rate for ATZ at low or high temperature, being more than 95% at the highest, and the removal performance was very excellent, which also showed that the magnetic biochar coupled with degradation bacteria immobilized gel microspheres could effectively improve the negative influence of different environmental conditions on free bacteria / adsorbent, and improve the removal effect of ATZ.

[0071] 5. Soil experiment:

[0072] Experimental conditions: The collected soil was naturally air-dried at room temperature, sieved through a 20-mesh screen to remove impurities, then a certain amount of ATZ powder was dissolved in a small amount of acetone and mixed with the soil to obtain 20-22 mg / kg of ATZ artificially contaminated soil. After 2-3 days of volatilization in a fume hood, it was used for subsequent experiments. In this study, three parallel samples were tested simultaneously for each treatment. In the soil with a water content of 60%, the material was added at a dosage of 0.5%. Four treatment groups were set up: CK, DNS32, MBC-P and DMBC-P. 1-1.1 g of soil sample was taken at 0, 1, 3 and 5 days, and the process of adding 10 mL of methanol, ultrasonic extraction for 2 h, centrifugation for 10 min, nitrogen blowing of the supernatant, and adding 10 mL of chloroform to constant volume was used to determine the residual concentration of ATZ in the soil by gas chromatograph, to explore the repair effect of DMBC-P on ATZ contaminated soil.

[0073] Figure 5 The figure shows the repair effect of different repair agents on atrazine contaminated soil, a represents CK, b represents DNS32, c represents MBC-P, and d represents DMBC-P; as shown in Figure 5 With the extension of incubation time, compared with CK, DNS32, MBC-P and DMBC-P all reduced the concentration of ATZ in the soil to different extents. The removal rate of MBC-P on ATZ increased from 40% to 58% and remained basically unchanged, because the adsorption of MBC-P and ATZ in the soil, including pore filling, electrostatic attraction and π-π stacking, would be affected by the relatively limited pore structure, adsorption sites and contact area of MBC-P itself. In addition, the removal effect of DNS32 and DMBC-P on ATZ in the soil increased with time, and DMBC-P had a faster removal rate than the free bacteria alone, and could completely remove 20-22 mg / kg of ATZ in 5 days. Moreover, the magnetic biochar coupled with degradation bacteria immobilized gel microspheres also had excellent magnetic recovery performance, and after the completion of pollution remediation, the added immobilized microspheres could be recovered at a rate of 95-98% or more by using an external magnet. In summary, for ATZ contaminated soil, the magnetic biochar coupled with degradation bacteria immobilized gel microspheres of the present application is a repair agent with high efficiency and practical application prospect.

Claims

1. A method for preparing a magnetic biochar-coupled degradation bacteria immobilized gel microsphere, characterized in that The preparation method is carried out according to the following steps: Step one, preparation of bacterial suspension: Acinetobacter baumannii strain DNS32 is inoculated into inorganic salt culture medium, and the inoculation amount is 1-1.2%; after being cultured at a temperature of 29.5-30.5 ℃ for 47-49 h, the cells are harvested at the logarithmic phase, and the wet cells are obtained by centrifugation at a speed of 10,000-10,005 r / min for 5-5.5 min, then the bacterial cells are resuspended with sterile water to obtain the bacterial suspension; The inorganic salt culture medium in step one is composed of 1.55-1.65 g / L K2HPO4, 0.35-0.45 g / L KH2PO4, 0.15-0.25 g / L MgSO4, 0.08-0.12 g / L NaCl, 2.9-3.1 g / L glucose and 98-102 g / L ATZ, and the inorganic salt culture medium is sterilized at 121 ℃ for 30 min before use; Step two, preparation of magnetic biochar: The corn straw powder is placed in a tube furnace and pyrolyzed at 500-505 ℃ under a nitrogen atmosphere for 2-2.05 h to obtain biochar; the biochar is mixed with a ferric salt mixed solution, then ammonia water is added, and the pH is adjusted to 11-12, and then mechanical stirring is carried out for 60-65 min to obtain a ferric-carbon precipitate; the mass of the corn straw powder, the volume of the ferric salt mixed solution and the volume of the ammonia water are (10-10.5) g:(398-402) mL:(9.5-10.5) mL; after washing, drying and grinding, the ferric-carbon precipitate is obtained to obtain the magnetic biochar; The iron salt mixed solution in step two is mixed from FeSO4 solution and FeCl3 solution, the molar ratio of Fe 2+ in FeSO4 solution to Fe 3+ in FeCl3 is 2:1, and the molar concentration of Fe 2+ is 0.1 mol / L; Step three, preparation of magnetic biochar coupled degradation bacteria immobilized gel microspheres: Sodium alginate is added to deionized water, and ultrasonic stirring is carried out until it is completely dissolved; after high-temperature sterilization, it is cooled to room temperature to obtain a sodium alginate solution; the magnetic biochar and the bacterial suspension are added to the sodium alginate solution to obtain an MBC-cell mixed solution; the mass ratio of the magnetic biochar, the wet cells in the bacterial suspension and the sodium alginate in the sodium alginate solution is (2.0-2.2) g:(2.0-2.2) g:(1.95-2.05) g; the MBC-cell mixed solution is added dropwise to the sterilized calcium chloride solution, and the calcium is calcined for 24-24.5 h to obtain the immobilized microspheres; the volume ratio of the MBC-cell mixed solution to the sterilized calcium chloride solution is (98-100):(198-200); the immobilized microspheres are washed 3-5 times to obtain the magnetic biochar coupled degradation bacteria immobilized gel microspheres, which are used for removing atrazine.

2. The method for preparing magnetic biochar coupled with degrading bacteria immobilized gel microspheres according to claim 1, characterized in that... 1-1.05 mL of sterile water is used to resuspend the bacterial cells in step one.

3. The method for preparing magnetic biochar coupled with degrading bacteria immobilized gel microspheres according to claim 1, characterized in that... The corn straw powder in step two is prepared according to the following steps: the corn straw is washed and dried, and then ground into a powder with a particle size of 2.0-2.05 mm to obtain the corn straw powder.

4. The method according to claim 1, wherein the method is characterized by In step two, the corn straw powder is heated to 500 ℃ at a heating rate of 10 ℃ / min.

5. The method according to claim 1, wherein the method is characterized by In step three, the mass ratio of sodium alginate to deionized water is (1.95-2.05) g:(100-102) mL.

6. The method according to claim 1, wherein the method is characterized by The mass fraction of calcium chloride in the sterilized calcium chloride solution in step three is 1.95-2.05%.

7. The method for preparing magnetic biochar coupled with degrading bacteria immobilized gel microspheres according to claim 1, characterized in that... The immobilized microspheres are washed with a sodium chloride solution with a concentration of 0.9-0.95% in step three.

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