Combined repairing agent for immobilizing soil antimony by microbial functional bacteria reinforced iron modified charcoal and preparation method thereof

Abstract

The invention belongs to the technical field of soil heavy metal pollution remediation, and discloses a combined remediation agent for immobilizing soil antimony by microbial functional bacteria reinforced iron modified biochar, and the remediation agent comprises the following components by mass: 60% of iron modified biochar, 30% of functional bacteria microcapsules, 5% of a humic acid activator, and 5% of montmorillonite. Antimony-resistant functional bacteria are encapsulated by adopting a microencapsulation technology to form functional bacteria microcapsules so as to physically protect thalli, and cane sugar is assisted to provide initial energy so as to enhance the soil survival colonization potential of the thalli; meanwhile, simple mixing is abandoned, the iron modified biochar carrier, the functional bacterium microcapsules and montmorillonite powder are subjected to dry mixing by adopting a gradient compounding process, then humic acid activation liquid is uniformly sprayed, and sucrose powder is supplemented so as to promote close contact and spatial distribution matching of the functional bacterium microcapsules, the carrier and a humic acid nutrient source; humic acid synergistically enhances the complexing ability of antimony and assists in activating the functional bacteria, and a synergistic system of iron-modified charcoal chemical immobilization and microencapsulated functional bacteria microbial oxidation is constructed.

Description

Technical Field

[0001] The present invention belongs to the technical field of soil heavy metal pollution remediation, and specifically relates to a combined remediation agent for fixing soil antimony by enhancing iron-modified biochar with microbial functional bacteria, and a preparation method thereof. Background Art

[0002] Soil heavy metal pollution refers to the phenomenon that heavy metals accumulate excessively in the soil due to human activities, such as industrial production, agricultural activities and irrational disposal of domestic waste, and their content exceeds the soil background value or environmental quality standard, thereby causing harm to the soil ecosystem, crop growth and human health. Heavy metals in the soil are difficult to degrade, easy to accumulate, and highly toxic. They can be transmitted and enriched through the food chain, threatening ecological security and human health.

[0003] Due to human activities, antimony pollution is becoming increasingly common. Current soil antimony pollution remediation technology has significant limitations. Although single iron-modified biochar can improve the adsorption capacity of antimony, its immobilization efficiency is limited by the saturation of surface active sites and insufficient long-term stability. Although metal-resistant functional bacteria have the potential for antimony form transformation, exogenous bacterial agents are easily inhibited by biological competition in complex soil environments, have difficulty colonizing, and are difficult to maintain activity. Existing combined remediation strategies mostly use simple physical mixing of biochar and microorganisms, which fails to solve the problem of synergy between functional bacteria and carrier interfaces, resulting in easy loss of bacteria, inhibition of metabolic activity, and low efficiency of microbial-driven oxidation of antimony Sb(III)→Sb(V). In addition, the technical system lacks regulation of soil microecology and fails to effectively activate the synergistic antimony fixation function of soil microorganisms. The spatial mismatch between the biochar carrier and the functional bacteria further weakens the remediation efficiency, so it needs to be improved. Summary of the Invention

[0004] In response to the shortcomings of the existing technology, the present invention provides a combined repair agent for fixing soil antimony by using microbial functional bacteria to enhance iron-modified biochar and a preparation method thereof, which has the advantage of synergistic enhancement.

[0005] To achieve the above-mentioned purpose, the present invention provides the following technical solution: a combined remediation agent for fixing soil antimony by using microbial functional bacteria to enhance iron-modified biochar, wherein the remediation agent is composed of the following components by mass percentage: 60% iron-modified biochar, 30% functional bacteria microcapsules, 5% humic acid activator, and 5% montmorillonite.

[0006] The preparation method of a combined remediation agent for fixing soil antimony by enhancing iron-modified biochar with microbial functional bacteria comprises the following steps:

[0007] Step 1: Preparation of iron-modified biochar carrier

[0008] Corn stalks are used, moldy and pest-infested parts are removed, and the stalks are crushed into 10-20cm segments in a crusher. They are then transferred to a grinder for secondary crushing, with the length of the fragments controlled within the range of 2-5mm. The fragments are then placed in an ultrasonic cleaning tank to remove dust and soluble impurities. After draining, they are spread flat on stainless steel trays and placed in a blast drying oven at a constant temperature of 80℃ for 24 hours until the moisture content of the material drops below 5%.

[0009] Weigh FeSO4·7H2O crystals, dissolve in deionized water to make a 0.5 mol / L solution, add 1% ascorbic acid to prevent Fe 2+ Oxidation: Dry straw fragments and iron salt solution are added to the reactor at a mass ratio of 1:10. The stirrer is started and the mixing speed is maintained at 120 revolutions per minute. The mixture is heated in a water bath at a constant temperature of 80°C for three hours to ensure that the iron ions fully penetrate into the microporous structure of the straw.

[0010] After the reaction, the solid and liquid phases were immediately separated by filtration. The modified straw was transferred to a vacuum drying oven, set at 110°C and a vacuum degree of minus 0.09 MPa, and dried for 24 hours to constant weight. It was then placed in a tubular pyrolysis furnace, and high-purity nitrogen was introduced to create an oxygen-free environment. The temperature was raised to 450°C at a rate of 5°C per minute, and pyrolysis was carried out at a constant temperature for two hours. The modified straw was naturally cooled to room temperature to obtain a specific surface area greater than 200m 2 / g, iron-modified biochar with an iron content of more than 8%;

[0011] Step 2: Expansion of the dual-bacteria system of antimony-resistant functional bacteria

[0012] Ochrobacter oryzae and Bacillus subtilis strains were inoculated into beef extract peptone liquid medium, respectively, and cultured at 130 rpm in a constant temperature shaker at 30°C for 48 hours to achieve bacterial activation and biomass amplification. The activated bacterial liquid was mixed in a 1:1 volume ratio and inoculated into a 50 L fermenter. The dissolved oxygen content was controlled at 30% and the pH value was 7.0. The culture was carried out at 30°C for 36 hours, and the cells were collected by centrifuge at 12,000 rpm and washed three times with physiological saline to obtain a total viable bacterial count of more than 1 × 10 9 CFU / mL composite bacterial sludge;

[0013] Step 3: Microencapsulation of functional bacteria

[0014] Weigh sodium alginate powder and dissolve it in strictly sterilized deionized water to prepare a sodium alginate colloidal solution with a mass concentration of 2%. Place the colloidal solution in an autoclave and sterilize it at 121°C for 20 minutes to completely kill any possible bacteria. Then, mix the sodium alginate colloidal solution with the composite bacterial sludge prepared in step 2 in a volume ratio of 3:1. Use sterile instruments to fully stir under a sterile operating environment to ensure that the bacterial sludge is evenly dispersed in the sodium alginate solution to form a uniform mixed bacterial solution. The mixing process should be gentle to avoid shear force damaging the bacteria.

[0015] After the mixed bacterial solution is prepared, it is immediately subjected to ionic crosslinking and curing to form microcapsules. The mixed bacterial solution is transferred to a constant pressure dripping device. Under constant pressure control, the mixed bacterial solution is dripped at a steady rate into a CaCl2 solution with a mass concentration of 2%. After the droplets fall into the CaCl2 solution, the calcium ions will quickly undergo an ion exchange reaction with the sodium alginate molecules to form a water-insoluble calcium alginate gel network, thereby wrapping and curing the internal bacterial mud to form microcapsules; the entire dripping and curing process lasts for 30 minutes to ensure that all microcapsules are fully and evenly crosslinked and cured; after curing is completed, the formed microcapsules are collected and separated from the CaCl2 solution using a sterile sieve with an appropriate pore size. After the collected microcapsules are immediately rinsed three times with a large amount of sterile deionized water to thoroughly remove the residual CaCl2 and unreacted substances on the surface, and finally the functional bacterial microcapsules are obtained;

[0016] Step 4: Gradient compounding of repair agents

[0017] First, the dry materials are evenly mixed. 60 parts of the iron-modified biochar prepared in step 1, 30 parts of the functional bacteria microcapsules obtained in step 3, and 5 parts of montmorillonite powder pre-crushed to 200 mesh are accurately weighed. The three dry solid materials are put into the silo of the three-dimensional mixer.

[0018] After the dry base mixing is completed, the liquid phase activation stage begins. Accurately weigh 5 parts of humic acid powder and dissolve it in deionized water ten times its mass. Stir until completely dissolved to prepare a humic acid activation solution with a mass concentration of 5%. This activation solution is evenly sprayed in the form of fine atomization onto the dry base mixture in the three-dimensional mixer running at a low speed through a spray device.

[0019] After the liquid phase activation is completed, carbon source enhancement is immediately carried out by adding 5 parts of sucrose powder to the mixed material. Sucrose, as a fast-acting carbon source easily utilized by microorganisms, provides initial energy for the functional bacteria embedded in the microcapsules, promoting their rapid colonization and metabolic activities after application to the soil. After adding sucrose, the three-dimensional mixer is maintained at a speed of 25 revolutions per minute for 15 minutes to ensure that the newly added sucrose powder is fully and evenly dispersed in the humidified material without agglomeration. At this time, all solid and liquid components of the repair agent have completed gradient compounding, forming a pre-finished product that is physically mixed and uniform and has biochemical activity.

[0020] Step 5: Finalization and stabilization of finished products

[0021] First, a low-temperature drying process is performed. The mixed composite material is evenly spread on a clean stainless steel tray. The tray is transferred to a hot air circulation drying oven. The drying temperature is set to 40 degrees Celsius. The circulating fan is turned on to ensure that the hot air flows fully on the surface of the material. The drying is continued for 12 hours to slowly remove moisture and avoid high temperature damage to the activity of the functional bacteria microcapsules. The material status needs to be monitored regularly during the drying process until its moisture content is stably reduced to below 10%. At this time, the material texture is loose and does not clump, making it easy to crush and process later.

[0022] After drying, the particle size classification process begins. The dried block repair agent material is put into the roller crusher for crushing. The crushing force is controlled by adjusting the roller spacing to make the material initially deagglomerated. The crushed material is transferred to the vibrating screening machine. Standard sieves with apertures of 0.5 mm and 2.0 mm are used for grading and screening. Particles with a particle size range of 0.5 mm to 2.0 mm are collected as qualified finished products. This particle size range ensures that the repair agent has good soil permeability and application uniformity. For particles larger than 2.0 mm, they need to be returned to the crusher for reprocessing, and fine powders with a particle size of less than 0.5 mm are removed to ensure the consistency and physical stability of the product. Finally, inert packaging is carried out to ensure the stable performance of the product during the storage period.

[0023] Preferably, the crushed material in step 1 is put into an ultrasonic cleaning tank with deionized water as the medium and cleaned three times at a frequency of 4000 Hz, each time for fifteen minutes, so as to completely remove dust and soluble impurities.

[0024] Preferably, after the sodium alginate colloidal solution in step 3 is sterilized, it is necessary to cool the colloidal solution naturally to 40°C.

[0025] Preferably, the mixed bacterial solution in step 3 is added dropwise to the CaCl 2 When adding a solution, the droplet size must be precisely controlled during the addition process to ensure that the diameter of the formed droplets is controlled within the range of 1 mm to 2 mm.

[0026] Preferably, the speed of the three-dimensional mixer in step 4 is set to 25 revolutions per minute, the equipment is started for thorough mixing, and the mixing process lasts for 30 minutes.

[0027] Preferably, the spraying process in step 4 needs to control the addition rate and atomization effect to ensure that the liquid is evenly absorbed by the dry base material and avoid local over-wetting and agglomeration.

[0028] Preferably, the material laying thickness in step five is controlled within 5 cm, and the material laying thickness must be uniform.

[0029] Preferably, the mixed bacterial solution in step 3 is added dropwise to the CaCl 2When the solution is added dropwise, the container containing the CaCl2 solution needs to be placed on a magnetic stirrer to maintain gentle but continuous magnetic stirring.

[0030] Compared with the prior art, the application has the following beneficial effects:

[0031] By adopting the microencapsulation technology to encapsulate the antimony-resistant functional bacteria to form functional bacteria microcapsules to physically protect the bacteria and supplement the initial energy source with sucrose, the soil survival and colonization potential of the bacteria is enhanced, and the gradient compounding process is adopted to discard simple mixing, dry mix the iron-modified biochar carrier, the functional bacteria microcapsules and the montmorillonite powder, uniformly spray the humic acid activation liquid, and then supplement the sucrose powder to promote the close contact and space distribution matching of the functional bacteria microcapsules, the carrier and the humic acid nutrient source, and the humic acid cooperatively enhances the antimony complexing capacity and assists in activating the functional bacteria, so that a synergistic system of the iron-modified biochar chemical fixation and the microencapsulated functional bacteria microbial oxidation is constructed to drive the antimony oxidation process and improve the combined passivation efficiency of the toxic antimony, and the rhizosphere healthy microecosystem is reconstructed, the plant antioxidant defense system and nutrient absorption efficiency are strengthened, and the synergistic effect of long-term stable treatment of soil antimony pollution and safe production of crops is achieved. DETAILED DESCRIPTION

[0032] All other embodiments obtained by a person of ordinary skill in the art without creative labor on the basis of the embodiments in the application belong to the protection scope of the application.

[0033] The embodiment of the application provides a microbial functional bacteria reinforced iron-modified biochar combined remediation agent for fixing soil antimony, and the remediation agent is composed of the following components in percentage by mass: iron-modified biochar 60%, functional bacteria microcapsules 30%, humic acid activator 5%, and montmorillonite 5%.

[0034] The iron-modified biochar serves as a carrier material, fixes Sb through Fe-O-Sb complexation, reduces bioavailability, embeds the Sb-resistant bacterial group through the functional bacteria microcapsules, the humic acid activator promotes the reconstruction of the rhizosphere microbial community, enhances the activity of the bacterial group, and the montmorillonite can prevent the microcapsules from breaking, release the bacterial agent, and adsorb free Sb.

[0035] The preparation method of the microbial functional bacteria reinforced iron-modified biochar combined remediation agent for fixing soil antimony comprises the following steps:

[0036] Step one: preparation of the iron-modified biochar carrier

[0037] Corn stalks are used, the moldy and diseased parts are removed, the corn stalks are coarsely crushed to 10-20 cm segments by a crusher, and then the corn stalks are transferred into a pulverizer for secondary crushing, the length of the crushed material is controlled in the range of 2-5 mm, the crushed material is put into an ultrasonic cleaning tank to remove dust and soluble impurities, the crushed material is drained and laid on a stainless steel tray, and then the tray is placed into a forced air drying oven for constant temperature drying at 80 DEG C for 24 hours until the water content of the material is reduced to less than 5%.

[0038] Weigh FeSO4·7H2O crystals, dissolve in deionized water to make a 0.5 mol / L solution, add 1% ascorbic acid to prevent Fe 2+ Oxidation: Dry straw fragments and iron salt solution are added to the reactor at a mass ratio of 1:10. The stirrer is started and the mixing speed is maintained at 120 revolutions per minute. The mixture is heated in a water bath at a constant temperature of 80°C for three hours to ensure that the iron ions fully penetrate into the microporous structure of the straw.

[0039] After the reaction, the solid and liquid phases were immediately separated by filtration. The modified straw was transferred to a vacuum drying oven, set at 110°C and a vacuum degree of minus 0.09 MPa, and dried for 24 hours to constant weight. It was then placed in a tubular pyrolysis furnace, and high-purity nitrogen was introduced to create an oxygen-free environment. The temperature was raised to 450°C at a rate of 5°C per minute, and pyrolysis was carried out at a constant temperature for two hours. The modified straw was naturally cooled to room temperature to obtain a specific surface area greater than 200m 2 / g, iron-modified biochar with an iron content of more than 8%;

[0040] Step 2: Expansion of the dual-bacteria system of antimony-resistant functional bacteria

[0041] Ochrobacter oryzae and Bacillus subtilis strains were inoculated into beef extract peptone liquid medium, respectively, and cultured at 130 rpm in a constant temperature shaker at 30°C for 48 hours to achieve bacterial activation and biomass amplification. The activated bacterial liquid was mixed in a 1:1 volume ratio and inoculated into a 50 L fermenter. The dissolved oxygen content was controlled at 30% and the pH value was 7.0. The culture was carried out at 30°C for 36 hours, and the cells were collected by centrifuge at 12,000 rpm and washed three times with physiological saline to obtain a total viable bacterial count of more than 1 × 10 9 CFU / mL composite bacterial sludge;

[0042] Step 3: Microencapsulation of functional bacteria

[0043] Weigh sodium alginate powder and dissolve it in strictly sterilized deionized water to prepare a sodium alginate colloidal solution with a mass concentration of 2%. Place the colloidal solution in an autoclave and sterilize it at 121°C for 20 minutes to completely kill any possible bacteria. Then, mix the sodium alginate colloidal solution with the composite bacterial sludge prepared in step 2 in a volume ratio of 3:1. Use sterile instruments to fully stir under a sterile operating environment to ensure that the bacterial sludge is evenly dispersed in the sodium alginate solution to form a uniform mixed bacterial solution. The mixing process should be gentle to avoid shear force damaging the bacteria.

[0044] After the mixed bacteria solution is prepared, ion exchange solidification is immediately performed to form microcapsules. The mixed bacteria solution is transferred to a constant pressure dropping device. Under the control of constant pressure, the mixed bacteria solution is dropped into a 2% CaCl2 solution at a stable rate. After the droplets fall into the CaCl2 solution, the calcium ions will rapidly exchange with the sodium alginate molecules to form a calcium alginate gel network that is insoluble in water, thereby encapsulating and solidifying the bacterial slurry inside to form microcapsules. The entire dropping and solidification process lasts for 30 minutes to ensure that all microcapsules are fully and uniformly cross-linked and solidified. After solidification is completed, a sterile screen with appropriate pore size is used to collect and separate the formed microcapsules from the CaCl2 solution. The collected microcapsules need to be immediately rinsed with a large amount of sterile deionized water for three times to completely remove the residual CaCl2 and unreacted substances on the surface, and finally obtain the functional bacteria microcapsules;

[0045] Step four: Gradient compounding of repair agent

[0046] First, uniformly mix the dry base materials. Accurately weigh 60 parts of iron-modified biochar prepared in step one, 30 parts of functional bacteria microcapsules obtained in step three, and 5 parts of montmorillonite powder pre-crushed to 200 mesh. Put the above three dry solid materials into the hopper of the three-dimensional mixer together;

[0047] After the dry base mixing is completed, the liquid activation stage is entered. Accurately weigh 5 parts of humic acid powder and dissolve it in ten times the mass of deionized water. Stir until completely dissolved to prepare a 5% humic acid activation solution. Spray this activation solution in the form of fine mist evenly onto the dry base mixture in the three-dimensional mixer running at low speed through a spraying device;

[0048] After the liquid activation is completed, immediately perform carbon source reinforcement. Add 5 parts of sucrose powder to the mixed materials. Sucrose serves as a readily available carbon source for microorganisms, providing initial energy for the functional bacteria embedded in the microcapsules to promote their rapid colonization and metabolic activity after being applied to the soil. After adding sucrose, continue to run the three-dimensional mixer at a speed of 25 revolutions per minute for 15 minutes to ensure that the newly added sucrose powder is evenly dispersed in the already humidified materials without aggregation. At this time, all solid and liquid components of the repair agent have completed gradient compounding, forming a pre-product that is physically mixed uniformly and has biochemical activity;

[0049] Step five: product shaping and stabilization

[0050] First, a low-temperature drying process is performed. The mixed composite material is evenly spread on a clean stainless steel tray. The tray is transferred to a hot air circulation drying oven. The drying temperature is set to 40 degrees Celsius. The circulating fan is turned on to ensure that the hot air flows fully on the surface of the material. The drying is continued for 12 hours to slowly remove moisture and avoid high temperature damage to the activity of the functional bacteria microcapsules. The material status needs to be monitored regularly during the drying process until its moisture content is stably reduced to below 10%. At this time, the material texture is loose and does not clump, making it easy to crush and process later.

[0051] After drying, the particle size classification process begins. The dried block repair agent material is put into the roller crusher for crushing. The crushing force is controlled by adjusting the roller spacing to make the material initially deagglomerated. The crushed material is transferred to the vibrating screening machine. Standard sieves with apertures of 0.5 mm and 2.0 mm are used for grading and screening. Particles with a particle size range of 0.5 mm to 2.0 mm are collected as qualified finished products. This particle size range ensures that the repair agent has good soil permeability and application uniformity. For particles larger than 2.0 mm, they need to be returned to the crusher for reprocessing, and fine powders with a particle size of less than 0.5 mm are removed to ensure the consistency and physical stability of the product. Finally, inert packaging is carried out to ensure the stable performance of the product during the storage period.

[0052] First, corn straw is used as raw material, which is crushed, ultrasonically cleaned, and dried, then impregnated with a FeSO4 solution containing ascorbic acid, and then vacuum-dried and pyrolyzed in a nitrogen atmosphere at 450°C to obtain high-specific-surface-area iron-modified biochar; secondly, Bacillus oryzae and Bacillus subtilis are activated and mixed and fermented in a 1:1 ratio, and a highly active composite bacterial sludge is obtained by centrifugation; the bacterial sludge is then mixed with sterilized sodium alginate colloid, and 1-2mm functional bacterial microcapsules are precisely formed by dripping CaCl2 solution; then, the iron-modified biochar, functional bacterial microcapsules and montmorillonite powder are dry-mixed, humic acid activation solution is sprayed in, and sucrose carbon source is added to complete the gradient compounding; finally, 0.5-2.0mm granular finished products are obtained after low-temperature drying at 40°C and crushing and screening.

[0053] In step 1, the crushed material is put into an ultrasonic cleaning tank with deionized water as the medium and cleaned three times at a frequency of 4000 Hz, each time for fifteen minutes, so as to completely remove dust and soluble impurities.

[0054] The dust and soluble impurities in the straw fragments are thoroughly removed by three cleanings with 4000Hz ultrasonic waves, ensuring that the subsequent iron ions can fully penetrate into the clean straw microporous structure, thereby improving the loading efficiency and specific surface area of ​​the iron-modified biochar.

[0055] In step 3, after the sodium alginate colloidal solution is sterilized, it is necessary to cool the colloidal solution naturally to 40°C.

[0056] After sterilization is completed, the colloidal solution is cooled to avoid high temperature damage to the subsequently added bacteria.

[0057] In step 3, the mixed bacterial solution is added dropwise to the CaCl 2 When adding a solution, the droplet size must be precisely controlled during the addition process to ensure that the diameter of the formed droplets is controlled within the range of 1 mm to 2 mm.

[0058] The diameter of the droplets formed by the addition of the mixed bacterial liquid is precisely controlled to be within the range of 1-2 mm to ensure the uniform size of the microcapsules, which can not only effectively encapsulate the bacteria to prevent leakage, but also maintain a moderate thickness of the gel layer to ensure the survival rate and activity release efficiency of the functional bacteria in the soil.

[0059] In step 4, the speed of the three-dimensional mixer is set to 25 revolutions per minute, the equipment is started for thorough mixing, and the mixing process lasts for 30 minutes.

[0060] The multi-dimensional motion trajectory of the three-dimensional mixer ensures that material particles with different specific gravities and shapes are highly evenly dispersed, laying a uniform dry basis for the subsequent addition of liquid components.

[0061] Among them, the spraying process in step 4 needs to control the addition rate and atomization effect to ensure that the liquid is evenly absorbed by the dry base material and avoid local over-wetting and agglomeration.

[0062] The moisture content of the entire mixed system is precisely controlled at 15% by spraying. The addition of humic acid can not only activate the activity of functional bacteria, but also enhance the complexing ability of the repair agent on antimony.

[0063] Among them, the material laying thickness in step five is controlled within 5 cm, and the material laying thickness must be uniform.

[0064] By controlling the thickness of the material in the stainless steel tray to within 5 cm, the drying efficiency and uniformity are guaranteed, and incomplete drying caused by over-thickness is avoided.

[0065] In step 3, the mixed bacterial solution is added dropwise to the CaCl 2 When adding the solution, the container containing the CaCl2 solution should be placed on a magnetic stirrer to maintain gentle but continuous magnetic stirring.

[0066] By continuously rotating at a low speed, the solution can be kept flowing without destroying the newly formed microcapsules.

[0067] It should be noted that, in this document, relational terms such as first and second, etc., are used only to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "comprises," "comprising," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that includes a list of elements includes not only those elements but also other elements not explicitly listed, or elements inherent to such process, method, article, or apparatus.

[0068] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A combined remediation agent for soil antimony fixation using iron-modified biochar enhanced by microbial functional bacteria, characterized in that: The repair agent is composed of the following components measured by mass percentage: 60% of iron-modified biochar, 30% of functional bacteria microcapsules, 5% of humic acid activator, and 5% of montmorillonite.

2. A method for preparing a combined remediation agent for fixing soil antimony by enhancing iron-modified biochar with microbial functional bacteria, characterized in that: The following steps are involved: Step 1: Preparation of iron-modified biochar carrier Corn stalks are used, moldy and pest-infested parts are removed, and the stalks are crushed into 10-20cm segments in a crusher. They are then transferred to a grinder for secondary crushing, with the length of the fragments controlled within the range of 2-5mm. The fragments are then placed in an ultrasonic cleaning tank to remove dust and soluble impurities. After draining, they are spread flat on stainless steel trays and placed in a blast drying oven at a constant temperature of 80℃ for 24 hours until the moisture content of the material drops below 5%. Weigh FeSO4·7H2O crystals, dissolve in deionized water to make a 0.5 mol / L solution, add 1% ascorbic acid to prevent Fe 2+ Oxidation: Dry straw fragments and iron salt solution are added to the reactor at a mass ratio of 1:

10. The stirrer is started and the mixing speed is maintained at 120 revolutions per minute. The mixture is heated in a water bath at a constant temperature of 80°C for three hours to ensure that the iron ions fully penetrate into the microporous structure of the straw. After the reaction, the solid and liquid phases were immediately separated by filtration. The modified straw was transferred to a vacuum drying oven, set at 110°C and a vacuum degree of minus 0.09 MPa, and dried for 24 hours to constant weight. It was then placed in a tubular pyrolysis furnace, and high-purity nitrogen was introduced to create an oxygen-free environment. The temperature was raised to 450°C at a rate of 5°C per minute, and pyrolysis was carried out at a constant temperature for two hours. The modified straw was naturally cooled to room temperature to obtain a specific surface area greater than 200m 2 / g, iron-modified biochar with an iron content of more than 8%; Step 2: Expansion of the dual-bacteria system of antimony-resistant functional bacteria Ochrobacter oryzae and Bacillus subtilis strains were inoculated into beef extract peptone liquid medium, respectively, and cultured at 130 rpm in a constant temperature shaker at 30°C for 48 hours to achieve bacterial activation and biomass amplification. The activated bacterial liquid was mixed in a 1:1 volume ratio and inoculated into a 50 L fermenter. The dissolved oxygen content was controlled at 30% and the pH value was 7.

0. The culture was carried out at 30°C for 36 hours, and the cells were collected by centrifuge at 12,000 rpm and washed three times with physiological saline to obtain a total viable bacterial count of more than 1 × 10 9 CFU / mL composite bacterial sludge; Step 3: Microencapsulation of functional bacteria Weigh sodium alginate powder and dissolve it in strictly sterilized deionized water to prepare a sodium alginate colloidal solution with a mass concentration of 2%. Place the colloidal solution in an autoclave and sterilize it at 121°C for 20 minutes to completely kill any possible bacteria. Then, mix the sodium alginate colloidal solution with the composite bacterial sludge prepared in step 2 in a volume ratio of 3:

1. Use sterile instruments to fully stir under a sterile operating environment to ensure that the bacterial sludge is evenly dispersed in the sodium alginate solution to form a uniform mixed bacterial solution. The mixing process should be gentle to avoid shear force damaging the bacteria. After the mixed bacterial solution is prepared, it is immediately subjected to ionic crosslinking and curing to form microcapsules. The mixed bacterial solution is transferred to a constant pressure dripping device. Under constant pressure control, the mixed bacterial solution is dripped at a steady rate into a CaCl2 solution with a mass concentration of 2%. After the droplets fall into the CaCl2 solution, the calcium ions will quickly undergo an ion exchange reaction with the sodium alginate molecules to form a water-insoluble calcium alginate gel network, thereby wrapping and curing the internal bacterial mud to form microcapsules; the entire dripping and curing process lasts for 30 minutes to ensure that all microcapsules are fully and evenly crosslinked and cured; after curing is completed, the formed microcapsules are collected and separated from the CaCl2 solution using a sterile sieve with an appropriate pore size. After the collected microcapsules are immediately rinsed three times with a large amount of sterile deionized water to thoroughly remove the residual CaCl2 and unreacted substances on the surface, and finally obtain functional bacterial microcapsules; Step 4: Gradient compounding of repair agents First, the dry materials are evenly mixed. 60 parts of the iron-modified biochar prepared in step 1, 30 parts of the functional bacteria microcapsules obtained in step 3, and 5 parts of montmorillonite powder pre-crushed to 200 mesh are accurately weighed. The three dry solid materials are put into the silo of the three-dimensional mixer. After the dry base mixing is completed, the liquid phase activation stage begins. Accurately weigh 5 parts of humic acid powder and dissolve it in deionized water ten times its mass. Stir until completely dissolved to prepare a humic acid activation solution with a mass concentration of 5%. This activation solution is evenly sprayed in the form of fine atomization onto the dry base mixture in the three-dimensional mixer running at a low speed through a spray device. After the liquid phase activation is completed, carbon source enhancement is immediately carried out by adding 5 parts of sucrose powder to the mixed material. Sucrose, as a fast-acting carbon source easily utilized by microorganisms, provides initial energy for the functional bacteria embedded in the microcapsules, promoting their rapid colonization and metabolic activities after application to the soil. After adding sucrose, the three-dimensional mixer is maintained at a speed of 25 revolutions per minute for 15 minutes to ensure that the newly added sucrose powder is fully and evenly dispersed in the humidified material without agglomeration. At this time, all solid and liquid components of the repair agent have completed gradient compounding, forming a pre-finished product that is physically mixed and uniform and has biochemical activity. Step 5: Finalization and stabilization of finished products First, a low-temperature drying process is performed. The mixed composite material is evenly spread on a clean stainless steel tray. The tray is transferred to a hot air circulation drying oven. The drying temperature is set to 40 degrees Celsius. The circulating fan is turned on to ensure that the hot air flows fully on the surface of the material. The drying is continued for 12 hours to slowly remove moisture and avoid high temperature damage to the activity of the functional bacteria microcapsules. The material status needs to be monitored regularly during the drying process until its moisture content is stably reduced to below 10%. At this time, the material texture is loose and does not clump, making it easy to crush and process later. After drying, the particle size classification process begins. The dried block repair agent material is put into the roller crusher for crushing. The crushing force is controlled by adjusting the roller spacing to make the material initially deagglomerated. The crushed material is transferred to the vibrating screening machine. Standard sieves with apertures of 0.5 mm and 2.0 mm are used for grading and screening. Particles with a particle size range of 0.5 mm to 2.0 mm are collected as qualified finished products. This particle size range ensures that the repair agent has good soil permeability and application uniformity. For particles larger than 2.0 mm, they need to be returned to the crusher for reprocessing, and fine powders with a particle size of less than 0.5 mm are removed to ensure the consistency and physical stability of the product. Finally, inert packaging is carried out to ensure the stable performance of the product during the storage period.

3. The method for preparing the combined remediation agent for fixing soil antimony by iron-modified biochar enhanced by microbial functional bacteria according to claim 2, characterized in that: The crushed material in step 1 is put into an ultrasonic cleaning tank with deionized water as the medium and cleaned three times at a frequency of 4000 Hz, each time for fifteen minutes, so as to completely remove dust and soluble impurities.

4. The method for preparing the combined remediation agent for fixing soil antimony by iron-modified biochar enhanced by microbial functional bacteria according to claim 2, characterized in that: After the sodium alginate colloidal solution in step 3 is sterilized, it is necessary to cool the colloidal solution naturally to 40°C.

5. The method for preparing the combined remediation agent for fixing soil antimony by iron-modified biochar enhanced by microbial functional bacteria according to claim 2, characterized in that: The mixed bacterial solution in step 3 is added dropwise to the CaCl 2 When adding a solution, the droplet size must be precisely controlled during the addition process to ensure that the diameter of the formed droplets is controlled within the range of 1 mm to 2 mm.

6. The method for preparing the combined remediation agent for fixing soil antimony by iron-modified biochar enhanced by microbial functional bacteria according to claim 2, characterized in that: The speed of the three-dimensional mixer in step 4 is set to 25 revolutions per minute, and the equipment is started for thorough mixing, and the mixing process lasts for 30 minutes.

7. The method for preparing the combined remediation agent for fixing soil antimony by iron-modified biochar enhanced by microbial functional bacteria according to claim 2, characterized in that: The spraying process in step 4 requires controlling the addition rate and atomization effect to ensure that the liquid is evenly absorbed by the dry base material and to avoid local over-wetting and agglomeration.

8. The method for preparing the combined remediation agent for fixing soil antimony by iron-modified biochar enhanced by microbial functional bacteria according to claim 2, characterized in that: The material laying thickness described in step 5 is controlled within 5 cm, and the material laying thickness must be uniform.

9. The method for preparing the combined remediation agent for fixing soil antimony by iron-modified biochar enhanced by microbial functional bacteria according to claim 2, characterized in that: The mixed bacterial solution in step 3 is added dropwise to the CaCl 2 When adding the solution, the container containing the CaCl2 solution should be placed on a magnetic stirrer to maintain gentle but continuous magnetic stirring.