A three-stage gradient porous carbon nest particle capable of capturing near-surface microbial aerosols and a preparation method thereof

Abstract

The present application relates to the technical field of soil microbial remediation carrier materials, and proposes a three-stage gradient pore carbon nest particle capable of capturing near-surface microbial aerosols and a preparation method thereof.The three-stage gradient pore carbon nest particle is a homogeneous porous structure body, the particle size of the three-stage gradient pore carbon nest particle is 3-6 mm, and a three-stage gradient communicating pore system of micropores-mesopores-macropores is formed inside the three-stage gradient pore carbon nest particle; the pore size of the micropores is 0.02-0.5 microns; the pore size of the mesopores is 1-10 microns; and the pore size of the macropores is 20-100 microns.The three-stage gradient pore carbon nest particle provided by the present application can selectively enrich beneficial bacteria and inhibit soil-borne indigenous bacteria, and at the same time, a biological protection circle layer with a radius of 5-8 mm is formed at the particle-soil interface.

Description

Technical Field

[0001] This invention relates to the field of soil microbial remediation carrier materials technology, specifically to a three-level gradient porous carbon nest particle capable of capturing near-surface microbial aerosols and its preparation method. Background Technology

[0002] Near-surface atmosphere contains a large number of soil-derived microbial aerosols (such as Bacillus, Actinomycetes, and nitrogen-fixing bacteria), which are important sources of replenishment for soil microbial communities. By capturing and colonizing near-surface microbial aerosols, it is possible to effectively replenish and restore the microbial diversity of degraded soils, which is an important pathway for soil ecological restoration.

[0003] However, existing particles capable of capturing near-surface microbial aerosols still have shortcomings. They cannot achieve differentiated capture and colonization of microorganisms of different sizes, nor do they have an active chemotactic induction mechanism. Furthermore, existing particles cannot distinguish between beneficial and harmful bacteria, allowing both to enter the particle indiscriminately. After pathogenic fungi colonize inside the carrier, they not only consume nutrients but may also secrete toxins that inhibit the activity of beneficial bacteria, causing the carrier to become a sanctuary for native bacteria rather than a home for beneficial bacteria.

[0004] Therefore, it is essential to develop a particle that can capture near-surface microbial aerosols. Summary of the Invention

[0005] This invention proposes a three-level gradient porous carbon nest particle that can capture near-surface microbial aerosols and its preparation method. The three-level gradient porous carbon nest particle provided by this invention can selectively enrich beneficial bacteria and inhibit soil-borne indigenous bacteria, while forming a biological protective layer with a radius of 5 to 8 mm at the particle-soil interface.

[0006] The technical solution of the present invention is as follows: According to one aspect of the present invention, a three-level gradient porous carbon nest particle capable of capturing near-surface microbial aerosols is proposed. The three-level gradient porous carbon nest particle is a homogeneous porous structure with a particle size of 3-6 mm. The three-level gradient porous carbon nest particle forms a three-level gradient interconnected pore system of micropores-mesopores-macropores inside. The pore size of the micropores is 0.02~0.5μm; The diameter of the central hole is 1~10μm; The pore size of the macropore is 20~100μm.

[0007] In the above technical solution, the total pore volume of the three-level gradient porous carbon nest particles accounts for 28% to 35% of the total pore volume of the three-level gradient porous carbon nest particles, the micropores account for 8% to 12% of the total pore volume, the mesopores account for 18% to 22% of the total pore volume, and the macropores account for 55% to 65% of the total pore volume.

[0008] In the above technical solution, the three-level gradient porous carbon nest particles include the following raw materials in parts by weight: 40-65 parts of earthworm castings composite carbon matrix, 10-20 parts of diatomaceous earth, 8-15 parts of rice husk ash, 20-30 parts of attapulgite, 5-10 parts of hydrated alumina, 5-10 parts of bentonite, 3-8 parts of zeolite, and 3-8 parts of organic-inorganic composite binder.

[0009] In the above technical solution, the earthworm castings composite carbon matrix is ​​an inactivated earthworm castings composite carbon matrix, which is obtained by sequentially subjecting earthworm castings to high-temperature aerobic fermentation and high-temperature drying inactivation treatment.

[0010] In the above technical solution, the temperature of the high-temperature aerobic fermentation pile is 60~70℃, the time of the high-temperature aerobic fermentation is 15~20 days, the temperature of the high-temperature drying is 105℃, and the time of the high-temperature drying is 90~120 minutes.

[0011] In the above technical solution, the organic-inorganic composite adhesive includes sodium alginate, pregelatinized starch and silica sol in a mass ratio of 2:2:4~5.

[0012] According to another aspect of the present invention, the present invention also provides a method for preparing the above-mentioned three-level gradient porous carbon nest particles capable of capturing near-surface microbial aerosols, comprising the following steps: mixing the earthworm castings composite carbon matrix, diatomaceous earth, rice husk ash, hydrated alumina, bentonite and zeolite evenly, adding aged attapulgite, stirring and spraying the organic-inorganic composite binder, granulating, drying and cooling to obtain the three-level gradient porous carbon nest particles.

[0013] In the above technical solution, the granulation tilt angle is 45°~55°, the granulation rotation speed is 22~28 r / min, and the granulation time is 25~30 min.

[0014] In the above technical solution, the drying is a three-stage drying process, with different temperatures for the first, second, and third stages of drying, and the same drying time for the first, second, and third stages.

[0015] In the above technical solution, the temperature of the first drying stage is 48~52℃, the drying time of the first drying stage is 85~95min, the temperature of the second drying stage is 65~75℃, the drying time of the second drying stage is 85~95min, the temperature of the third drying stage is 100~110℃, and the drying time of the third drying stage is 85~95min.

[0016] Compared with existing technologies, this invention provides a homogeneous porous particle with a three-level gradient interconnected pore structure of micropores, mesopores, and macropores. The three levels of pores have clearly defined functions and synergistic effects. The micropores store carbon and chemotactic signals, the mesopores provide for the colonization and reproduction of microorganisms, and the macropores allow airborne microbial aerosols to enter and exchange gases, forming a complete functional chain of capture-colonization-reproduction-release. This enables differentiated capture and colonization of microorganisms of different sizes, increases the colonization of beneficial bacteria in the three-level gradient porous carbon nest particle, and improves the interception rate of native bacteria. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this invention more apparent, the invention is described in detail below. It should be understood that the invention is not limited to the description herein.

[0018] Third-order gradient porous carbon nest particles In this invention, the three-level gradient porous carbon nest particles are homogeneous porous structures with a particle size of 3-6 mm. The internal structure of these particles forms a three-level gradient interconnected pore system consisting of micropores, mesopores, and macropores. The micropores, with a diameter of 0.02-0.5 μm, originate from the natural microporous structure of diatomaceous earth, nanopores formed by the dehydration and transformation of hydrated alumina, and nanoscale gaps formed by the accumulation of silica sol particles, serving as long-term storage of organic carbon sources and chemotactic signaling substances. The mesopores, with a diameter of 1-10 μm, originate from the natural mesoporous structure of the earthworm castings composite carbon matrix and capillary pores formed by powder accumulation and binder shrinkage during granulation, serving as the core area for microbial colonization and reproduction, providing habitat sites for beneficial bacteria with a diameter of 0.5 μm-3 μm. The macropores, with a diameter of 20-100 μm, originate from the micron-scale honeycomb skeleton structure of rice husk ash and macroscopic gaps between particles during granulation, serving as capture channels and gas exchange channels for airborne microbial aerosols.

[0019] In this invention, the total pore volume of the three-level gradient porous carbon nest particles accounts for 28% to 35% of the total pore volume of the three-level gradient porous carbon nest particles, micropores account for 8% to 12% of the total pore volume, mesopores account for 18% to 22% of the total pore volume, and macropores account for 55% to 65% of the total pore volume.

[0020] The three-level gradient porous carbon nest particles of the present invention comprise the following raw materials in parts by weight: 40-65 parts of earthworm castings composite carbon matrix, 10-20 parts of diatomaceous earth, 8-15 parts of rice husk ash, 20-30 parts of attapulgite, 5-10 parts of hydrated alumina, 5-10 parts of bentonite, 3-8 parts of zeolite, and 3-8 parts of organic-inorganic composite binder.

[0021] In natural ecosystems, microorganisms of different sizes have different niche requirements: bacteria (0.5μm~3μm) need micron-sized pores as habitats, actinomycete hyphae (0.5μm~1.2μm) need continuous channels for extension, and fungal hyphae (>10μm) need even more space for diffusion and growth. Single-pore size carrier materials cannot simultaneously meet the differentiated colonization needs of these three types of microorganisms, failing to achieve differentiated capture and colonization of microorganisms of different sizes. If the pore size is too small, bacteria cannot migrate in; if the pore size is too large, the bacteria are leached away by irrigation water. Furthermore, the lack of dedicated macroporous channels adapted to fungal hyphae growth makes it difficult for hyphae to diffuse outwards. Moreover, existing particles rely solely on passive physical adsorption and fixation of bacteria on the carrier surface, lacking the ability to actively attract microorganisms and release signals, resulting in low capture efficiency and a long colonization initiation cycle. However, this invention provides a homogeneous porous particle with a three-tiered gradient of micropores, mesopores, and macropores. Each pore level has a clear functional division: micropores store carbon and chemotactic signals, mesopores provide for microbial colonization and reproduction, and macropores allow airborne microbial aerosols to enter and facilitate gas exchange. This achieves the selective capture and colonization of beneficial indigenous bacteria in near-surface microbial aerosols without the addition of any exogenous functional bacteria, relying entirely on the particle's own pore structure and endogenous chemotactic substances. This simultaneously inhibits the entry and survival of harmful bacteria, preventing the carrier from becoming a haven for indigenous bacteria. No exogenous functional bacteria are added throughout the process, eliminating the need for a dedicated microbial agent production line, and there is no shelf-life limitation for live bacteria; the finished product can be stored for a long period.

[0022] In this invention, the mechanism by which the three-level gradient porous carbon nest particles achieve directional screening is as follows: (1) Size exclusion: The pore size is 1~10μm, which allows beneficial bacteria of 0.5μm~3μm to enter and colonize, while pathogenic fungal spores of ≥10μm are physically blocked outside the particle and cannot enter the core colonization area, effectively preventing the particle from becoming a sanctuary for indigenous bacteria; (2) Acidic microenvironment: The pH range inside the particles is 5.5 to 6.8. The main contributors are humic acid, attapulgite and hydrated alumina. Both attapulgite and hydrated alumina are acidic surface materials, which are suitable for the colonization and reproduction of beneficial bacteria and inhibit the growth of pathogenic fungi that prefer neutral to slightly alkaline environments. (3) Antibacterial effect of hydrated alumina: The active alumina formed after the dehydration of hydrated alumina releases trace amounts of Al. 3+It can disrupt the integrity of the cell wall of pathogenic fungi, interfere with the function of their cell membrane ion channels, and inhibit spore germination and hyphal growth; its effect is limited to the microenvironment within the particle and will not spread to the surrounding soil to cause ecological disturbance. Beneficial bacteria can also affect Al. 3+ Its tolerance is significantly higher than that of pathogenic fungi, and its antibacterial effect is mainly against harmful fungi; (4) Active suppression after colonization by beneficial bacteria: After beneficial bacteria successfully enter the pores inside the particle and colonize, they multiply in large numbers in the pores and quickly occupy all the effective colonization space inside the particle. This prevents the subsequent harmful bacteria from establishing a population due to the lack of attachment sites. The beneficial bacteria consume the organic carbon source, nitrogen source and trace elements slowly released inside the particle, so that the harmful bacteria cannot obtain the nutrients required for germination and reproduction after entering the particle. During the reproduction process, the beneficial bacteria continuously secrete antibacterial metabolites into the microenvironment, including organic acids (lactic acid, acetic acid, citric acid, etc.) to maintain and strengthen the weakly acidic microenvironment, bacteriocins (lipopeptide and polypeptide antibiotics) to target and inhibit the synthesis of cell walls of pathogenic fungi, siderophores chelate iron ions in the environment to cause iron deficiency stress in native bacteria, and hydrolytic enzymes (chitinase, β-1,3-glucanase) decompose the cell walls of pathogenic fungi. The colonized beneficial bacteria actively suppress native bacteria through space competition, nutrient competition and secretion of antibacterial metabolites. From the outside of the particle to the inside of the particle and then to the soil outside the particle, a complete closed loop of interception-inhibition-colonization-diffusion functions is formed, which together achieves selective capture and colonization of beneficial bacteria and multi-level, long-term inhibition of harmful bacteria.

[0023] In this invention, beneficial bacteria colonizing the interior of the particles continuously release antibacterial metabolites to the exterior of the particles during their reproduction, forming an antibacterial active zone with a radius of 5-8 mm at the particle-soil interface. Within this zone, the activity of pathogenic microorganisms is continuously inhibited. Unlike traditional chemical fungicides, this mechanism is continuously strengthened with the continuous reproduction of beneficial bacteria, achieving a long-lasting, self-reinforcing disease-suppressing effect without causing resistance in indigenous bacteria.

[0024] In this invention, the natural microporous structure of diatomaceous earth, the natural mesoporous structure of earthworm castings composite carbon matrix, and the micron-sized honeycomb skeleton and nano-sized stacked pores of rice husk ash constitute the basic framework of the three-level pore structure. The capillary pores formed between particles during the granulation process of powders of different fineness mainly contribute to the mesoporous region. The organic-inorganic composite binder added during granulation undergoes pore-forming behavior during drying. Sodium alginate, in its wet state, fills the spaces between powder particles in a gel-like state. After drying at 105℃, the gel volume shrinks drastically, leaving 1-10 μm micron-sized gaps in its original positions, directly contributing to the mesoporous region. Pregelatinized starch, after absorbing water and swelling, fills the spaces between particles in a paste-like state. After drying, the starch molecular chains collapse and harden, shrinking in volume to form porous starch skeleton pores with a pore size distribution of 1-10 μm, also contributing to the mesoporous region. Silica sol nano-SiO2 particles form a three-dimensional gel network during drying, with the accumulation between the particles forming a large number of <50 nm nano-sized gaps, contributing to the lower half of the microporous region. Hydrated alumina dehydrates under heating conditions, transforming into a gel. Further dehydration forms activated alumina. During dehydration, changes in the crystal structure create regular nanopores of 5-10 nm, further enriching the microporous system. The binder shrinks in volume during drying, generating shrinkage stress. This stress is transmitted to the surrounding powder particles through the colloid-particle interface. As drying continues, tensile stress gradually accumulates. When this stress exceeds the interfacial bonding strength, micron-level separation occurs between the colloid and particles, forming new pore channels at the previously tightly contacted interface, thus constructing a three-tiered, interconnected pore system of micropores, mesopores, and macropores.

[0025] In this invention, bentonite can adsorb sodium ions, and zeolite can adsorb ammonium ions.

[0026] Earthworm castings composite carbon matrix In this invention, earthworm castings composite carbon matrix is ​​a precursor of composite carbon nest (CCN). It is a carrier material that naturally integrates the triple functions of mesoporous structure, chemotactic signaling substances, and process adaptability of signaling substances after inactivation. It has high cation exchange capacity and huge internal specific surface area. Its honeycomb micropores can efficiently load and colonize beneficial functional bacteria, while also having a size sieving function, which can selectively intercept the infection path of indigenous bacteria. The mesoporous structure comes from the dual effects of mechanical grinding of earthworm intestine and microbial pore-forming. The chemotactic signaling substances include small molecule active peptides, free amino acids, fulvic acid, and plant endogenous hormones.

[0027] In this invention, the earthworm castings composite carbon matrix is ​​an inactivated earthworm castings composite carbon matrix, obtained by sequentially subjecting earthworm castings to high-temperature aerobic fermentation and high-temperature drying inactivation treatment. This process essentially eliminates the background microbial community while retaining chemotactic active substances such as small molecule active peptides, fulvic acid, and plant endogenous hormones. The carrier after this dual inactivation treatment becomes a sterile nutrient chamber—containing organic matter and chemotactic signaling substances to attract target native bacteria, while preventing other bacteria from competing for the ecological niche. The high-temperature aerobic fermentation pile temperature is 60-70℃, the fermentation time is 15-20 days, and the high-temperature drying temperature is 105℃, with a drying time of 90-120 minutes.

[0028] In this invention, the high-temperature aerobic fermentation stage kills most of the heat-sensitive vegetative cells (conventional saprophytic bacteria, indigenous bacteria, etc.), while simultaneously decomposing complex organic matter into small-molecule active peptides, amino acids, fulvic acid, and other plant-active substances. The high-temperature drying stage thoroughly kills any remaining spores, reducing the total viable count of the carrier to ≤1.0×10⁻⁶. 4 CFU / g. After dual inactivation treatment, the background microbial community in the earthworm castings composite carbon matrix was essentially eliminated, while the small molecule active peptides, fulvic acid, and chemotactic substances such as plant endogenous hormones, as well as the intact villous structure and organic matter skeleton, were completely preserved. The treated carrier became a sterile nutrient chamber. It has both organic matter and chemotactic signaling substances to attract target native bacteria, and no background bacteria compete for the ecological niche.

[0029] If carriers using organic materials such as earthworm castings are not effectively sterilized, their inherent microbial communities will preferentially occupy the pores within the particles, competing for niches with the target native bacteria and severely interfering with the capture and colonization of the target microbial community. The primacy effect in microbial ecology indicates that the species that first occupies a particular niche will exclude later occupants through resource competition and metabolic regulation. If unsterilized carriers are used, the large number of saprophytic bacteria (102) will further contribute to this problem. 7 ~10 8 Within days of leaving the factory, the CFU / g particles will occupy all the pores. Regardless of where they are subsequently distributed, these particles will carry pre-existing factory-pre-existing bacteria, not the functional microbial community of the target soil. Therefore, achieving an absolutely sterile, empty-nest state is a necessary prerequisite for ensuring the effective colonization of the target functional microbial community.

[0030] In this invention, earthworm castings are the final product of earthworms' digestion and decomposition of organic matter. Their formation involves a triple process: mechanical grinding by the earthworm's intestines (producing organic particles of uniform size), digestion by intestinal microorganisms (decomposing large organic molecules into smaller, more active substances), and mixing with earthworm secretions (rich in various plant endogenous hormones and enzymes). This biological process endows earthworm castings with multiple irreplaceable natural properties, all naturally integrated into the same material, specifically: (1) Structural mesoporous characteristics: The mechanical grinding of earthworm intestines makes the particle size distribution of earthworm castings highly uniform (mainly concentrated in the range of 80-200 mesh), and after accumulation, a large number of mesoporous channels of 1-10 μm are formed; the pore-forming effect of intestinal microorganisms further increases the density and connectivity of mesopores. The uniformity and stability of this mesoporous structural characteristic cannot be stably reproduced by any other organic material (compost, decomposed straw, peat, edible fungi residue, etc.). The pore distribution of ordinary compost is disordered, peat is mainly macropores and lacks mesopores, and coconut shell charcoal is mainly micropores; (2) A complete spectrum of chemotactic signaling molecules: Earthworm castings contain a complete spectrum of chemotactic signaling molecules: small molecule active peptides (molecular weight 500-3000 Da, which are potent signaling molecules for bacterial chemotaxis), free amino acids (containing more than 17 common amino acids, providing a broad spectrum of chemotactic signals), fulvic acid (molecular weight 300-1000 Da, which has both chemotactic signaling and nutrient chelation functions), and plant endogenous hormones (indoleacetic acid, gibberellin, cytokinins, etc., derived from earthworm secretions and symbiotic microbial metabolism). The completeness and diversity of this signaling spectrum cannot be replaced by any purification of a single signaling substance (such as adding fulvic acid or amino acids alone); (3) Process adaptability of retaining signaling substances after inactivation: Chemotactic signaling substances in earthworm castings exist in small molecule form and have high thermal stability. After dual inactivation treatment of high-temperature aerobic fermentation above 60℃ and high-temperature drying at 105℃, the background microbial community is basically eliminated, but chemotactic signaling substances such as small molecule active peptides, amino acids, fulvic acid and endogenous hormones are still completely retained. In contrast, although large molecule organic matter exists after inactivation of ordinary compost, small molecule signaling substances have been largely lost or transformed into inert forms, losing their chemotactic and inducing bacterial activity; (4) The pore walls of the earthworm castings composite carbon matrix have a unique villous structure: the formation temperature of earthworm castings is always maintained at room temperature (not exceeding 35℃), and the fibrous structure, polysaccharide chains, and protein skeleton of organic matter are all completely preserved. When the pores of earthworm castings are magnified to the micrometer level, what is seen is not a smooth mineral wall, but a three-dimensional network structure woven by organic matter fibers, humic acid colloids, microbial extracellular polymers, and mineral particles, which is densely distributed on the pore walls, forming a large number of fluffy and fibrous microscopic protrusions—that is, the villous structure. No high-temperature sintered material (including sintered particles of Japanese volcanic black soil) has this structure, and its pore walls are smooth mineral surfaces. The villous structure physically intercepts the bacterial community in the microbial aerosol, and the bacteria are entangled, hooked, and retained. Subsequently, the active functional groups lock the bacteria on the pore walls through hydrogen bonds and ion exchange, significantly improving the capture efficiency.

[0031] Hydrated alumina In this invention, hydrated alumina serves as both a skeleton reinforcing material and an active component of the binder in the formulation, and its colloidal form, together with the binder component, participates in the bonding and pore formation during the granulation process. Organic-inorganic composite adhesives In this invention, the organic-inorganic composite adhesive comprises sodium alginate, pregelatinized starch, and silica sol in a mass ratio of 2:2:4~5. During the drying process, the adhesive contributes to the formation of the pore structure simultaneously through volume shrinkage and chemical transformation. Conventionally, adhesives are considered to only play a bonding role, and their volume shrinkage after drying is regarded as a defect. However, this invention reveals that, under specific formulation and process conditions, the drying shrinkage stress of the adhesive can actively pull the surrounding powder particles to produce micron-level displacement, forming uniformly interconnected pore channels within the particles.

[0032] The present invention also provides a method for preparing a three-level gradient porous carbon nest particle that can capture near-surface microbial aerosols, as described above, comprising the following steps: mixing earthworm castings composite carbon matrix, diatomaceous earth, rice husk ash, hydrated alumina, bentonite and zeolite evenly, adding aged attapulgite, stirring and spraying the organic-inorganic composite binder, granulating, drying and cooling to obtain three-level gradient porous carbon nest particles.

[0033] In this invention, the aging of attapulgite specifically includes: mixing attapulgite with water at a mass ratio of 1:0.6~1, stirring to form a slurry, and allowing it to stand for aging for 25~40 minutes. The water is at room temperature. Attapulgite is a layered silicate mineral. When water is added for aging, water molecules enter the interlayer, expanding the interlayer spacing and forming a cardboard-like network structure, which is the water-resistant steel skeleton of the particles. When mixing the organic-inorganic composite adhesive, sodium alginate and pregelatinized starch are first dissolved in water at 45°C. The amount of water added is 3~5 times the mass of sodium alginate and pregelatinized starch. After stirring evenly, silica sol is added, and after mixing evenly, the organic-inorganic composite adhesive is obtained.

[0034] In this invention, earthworm castings composite carbon matrix, diatomaceous earth, rice husk ash, hydrated alumina, bentonite, and zeolite are mixed evenly for 5-10 minutes. Aged attapulgite is then added and stirred for 3-5 minutes. An organic-inorganic composite binder is then added in stages via atomized spraying, with droplet size ≤100μm. Spraying is paused for 10-15 seconds after 3-5 seconds to allow for sufficient water penetration. The mixture is kneaded until it can be formed into a ball by hand but crumbles easily when lightly pressed with a thumb. The mixture is then fed into a disc granulator at an inclination angle of 45°-55° and a rotation speed of 22-28 r / min for 25-30 minutes. The granulated particles are then subjected to three stages of drying and cooled to below 35°C to obtain three-level gradient porous carbon nest particles. The particles are prepared using a one-step forming and rolling granulation process, resulting in a homogeneous internal structure without any layered interfaces.

[0035] In this invention, the temperatures of the first, second, and third drying stages are different, while the drying times are the same. The temperature of the first drying stage is 48-52°C, preferably 50°C, and the drying time is 85-95 min, preferably 90 min. The temperature of the second drying stage is 65-75°C, preferably 70°C, and the drying time is 85-95 min, preferably 90 min. The temperature of the third drying stage is 100-110°C, preferably 105°C, and the drying time is 85-95 min, preferably 90 min.

[0036] The three-level gradient porous carbon nest particles prepared by this invention can capture near-surface microbial aerosols and are suitable for application scenarios such as soil surface application in facility farmland, orchards, degraded farmland restoration, and saline-alkali land improvement. When used in soil surface application and capturing near-surface microbial aerosols, the particles are applied to the soil surface with a thickness of 1cm to 2cm.

[0037] Unless otherwise specified, the following embodiments and comparative examples are as follows: Earthworm castings composite carbon matrix: organic matter content 70%~85%, total humic acid 28%~40%, total viable bacteria count ≤1.0×10⁻⁶ 4 CFU / g; Diatomaceous earth: 200 mesh, specific surface area ≥20m² 2 / g, micropore diameter 0.1~0.2μm; Rice husk ash: 100 mesh, SiO2 ≥ 85%, specific surface area ≥ 50 m² 2 / g, containing micron-sized honeycomb pores (approximately 10μm) and nano-sized stacked pores (<50nm).

[0038] Attapulgite: 200 mesh, montmorillonite content ≥70%; Hydrated alumina: 300 mesh, monohydrate alumina content ≥95%; Bentonite: 200 mesh, hydrogen-based, blue absorption ≥30g / 100g; Zeolite: 200 mesh, clinoptilolite content ≥80%.

[0039] Example 1 The three-gradient porous carbon nest particles consist of the following raw materials in parts by weight: 40 parts earthworm castings composite carbon matrix, 10 parts diatomaceous earth, 8 parts rice husk ash, 20 parts attapulgite, 5 parts hydrated alumina, 5 parts bentonite, 3 parts zeolite, and 3 parts organic-inorganic composite binder. The organic-inorganic composite adhesive comprises sodium alginate, pregelatinized starch, and silica sol in a mass ratio of 2:2:4. A method for preparing three-level gradient porous carbon nest particles capable of capturing near-surface microbial aerosols includes the following steps: S1. Earthworm castings are subjected to high-temperature aerobic fermentation, with the pile temperature controlled at 60℃ for 20 days. After fermentation, the material is dried in hot air at 105℃ for 9 minutes. After drying, the material is crushed and passed through a 100-mesh sieve to obtain earthworm castings composite carbon matrix. Attapulgite powder is taken and added to room temperature water at a powder-to-water ratio of 1:0.6. The mixture is stirred into a slurry and allowed to stand for 25 minutes to age, resulting in aged attapulgite. Sodium alginate and pregelatinized starch are taken and added to 45℃ warm water and stirred until completely dissolved. The amount of warm water added is 4 times the combined mass of sodium alginate and pregelatinized starch. Silica sol is then added and mixed evenly to obtain an organic-inorganic composite binder. S2. Add earthworm castings composite carbon matrix, diatomaceous earth, rice husk ash, hydrated alumina, bentonite, and zeolite to a mixer and stir at low speed for 5 minutes until the color is uniform. Add aged attapulgite and stir for 3 minutes. Then, add the organic-inorganic composite binder in batches by atomizing spray (droplet size ≤100μm). After spraying for 3 seconds, pause for 10 seconds to allow the moisture to fully penetrate. Knead until it can be formed into a ball by hand and can be easily broken down by light pressure with the thumb. Then, put it into a disc granulator with an inclination angle of 45°, a rotation speed of 22r / min, and a granulation time of 30 minutes. Dry the granulated particles sequentially at 50℃ for 90 minutes, 70℃ for 90 minutes, and 105℃ for 90 minutes. The output moisture content is ≤10%. After drying, let it cool naturally to ≤35℃ to obtain three-level gradient porous carbon nest particles.

[0040] Example 2 The three-gradient porous carbon nest particles consist of the following raw materials in parts by weight: 52 parts earthworm castings composite carbon matrix, 15 parts diatomaceous earth, 10 parts rice husk ash, 25 parts attapulgite, 8 parts hydrated alumina, 8 parts bentonite, 5 parts zeolite, and 5 parts organic-inorganic composite binder. The organic-inorganic composite adhesive comprises sodium alginate, pregelatinized starch, and silica sol in a mass ratio of 2:2:4. A method for preparing three-level gradient porous carbon nest particles capable of capturing near-surface microbial aerosols includes the following steps: S1. Earthworm castings are subjected to high-temperature aerobic fermentation, with the pile temperature controlled at 65℃ for 18 days. After fermentation, the material is dried in hot air at 105℃ for 110 minutes. After drying, the material is crushed and passed through a 100-mesh sieve to obtain earthworm castings composite carbon matrix. Attapulgite powder is taken and added to room temperature water at a powder-to-water ratio of 1:0.8. The mixture is stirred into a slurry and allowed to stand for 32 minutes to age, resulting in aged attapulgite. Sodium alginate and pregelatinized starch are added to 45℃ warm water and stirred until completely dissolved. The amount of warm water added is 4 times the combined mass of sodium alginate and pregelatinized starch. Silica sol is then added and mixed evenly to obtain an organic-inorganic composite binder. S2. Add earthworm castings composite carbon matrix, diatomaceous earth, rice husk ash, hydrated alumina, bentonite, and zeolite to a mixer and stir at low speed for 8 minutes until the color is uniform. Add aged attapulgite and stir for 4 minutes. Then, add the organic-inorganic composite binder in batches by atomizing (droplet size ≤100μm). Spray for 4 seconds and pause for 12 seconds to allow the moisture to fully penetrate. Knead until it can be formed into a ball by hand and can be easily broken down by light pressure with the thumb. Then, put it into a disc granulator with an inclination angle of 50°, a rotation speed of 25r / min, and a granulation time of 28 minutes. Dry the granulated particles sequentially at 50℃ for 90 minutes, 70℃ for 90 minutes, and 105℃ for 90 minutes. The output moisture content is ≤10%. After drying, let it cool naturally to ≤35℃ to obtain three-level gradient porous carbon nest particles.

[0041] Example 3 The three-gradient porous carbon nest particles consist of the following raw materials in parts by weight: 65 parts earthworm castings composite carbon matrix, 20 parts diatomaceous earth, 15 parts rice husk ash, 30 parts attapulgite, 10 parts hydrated alumina, 10 parts bentonite, 8 parts zeolite, and 8 parts organic-inorganic composite binder. The organic-inorganic composite adhesive comprises sodium alginate, pregelatinized starch, and silica sol in a mass ratio of 2:2:5; A method for preparing three-level gradient porous carbon nest particles capable of capturing near-surface microbial aerosols includes the following steps: S1. Earthworm castings are subjected to high-temperature aerobic fermentation, with the pile temperature controlled at 70℃ for 20 days. After fermentation, the material is dried in hot air at 105℃ for 120 minutes. After drying, the material is crushed and passed through a 100-mesh sieve to obtain earthworm castings composite carbon matrix. Attapulgite powder is taken and added to room temperature water at a powder-to-water ratio of 1:1. The mixture is stirred into a slurry and allowed to stand for 40 minutes to age, resulting in aged attapulgite. Sodium alginate and pregelatinized starch are taken and added to 45℃ warm water and stirred until completely dissolved. The amount of warm water added is 4 times the combined mass of sodium alginate and pregelatinized starch. Silica sol is then added and mixed evenly to obtain an organic-inorganic composite binder. S2. Add earthworm castings composite carbon matrix, diatomaceous earth, rice husk ash, hydrated alumina, bentonite, and zeolite to a mixer and stir at low speed for 10 minutes until the color is uniform. Add aged attapulgite and stir for 5 minutes. Then, add the organic-inorganic composite binder in batches by atomizing spray (droplet size ≤100μm). Spray for 5 seconds and pause for 15 seconds to allow the moisture to fully penetrate. Knead until it can be formed into a ball by hand and can be easily broken down by light pressure with the thumb. Then, put it into a disc granulator with an inclination angle of 55°, a rotation speed of 28r / min, and a granulation time of 25 minutes. Dry the granulated particles sequentially at 50℃ for 90 minutes, 70℃ for 90 minutes, and 105℃ for 90 minutes. The output moisture content is ≤10%. After drying, let it cool naturally to ≤35℃ to obtain three-level gradient porous carbon nest particles.

[0042] Example 4 Compared with Example 2, in this example, the three-level gradient porous carbon nest particles include the following raw materials in parts by weight: 52 parts of earthworm castings composite carbon matrix, 15 parts of diatomaceous earth, 25 parts of attapulgite, 8 parts of hydrated alumina, 8 parts of bentonite, 5 parts of zeolite, and 5 parts of organic-inorganic composite binder.

[0043] Example 5 Compared with Example 2, in this example, the three-level gradient porous carbon nest particles include the following raw materials in parts by weight: 52 parts of earthworm castings composite carbon matrix, 10 parts of rice husk ash, 25 parts of attapulgite, 8 parts of hydrated alumina, 8 parts of bentonite, 5 parts of zeolite, and 5 parts of organic-inorganic composite binder.

[0044] Example 6 Compared with Example 2, in this example, the three-level gradient porous carbon nest particles include the following raw materials in parts by weight: 52 parts of earthworm castings composite carbon matrix, 25 parts of attapulgite, 8 parts of hydrated alumina, 8 parts of bentonite, 5 parts of zeolite, and 5 parts of organic-inorganic composite binder.

[0045] Example 7 Compared to Example 2, in this example, the earthworm castings composite carbon matrix is ​​earthworm castings, which have not undergone high-temperature aerobic fermentation and high-temperature drying inactivation treatment. The total viable bacteria count in the earthworm castings is 8.7 × 10⁻⁶. 7 CFU / g, spore detection was 2.1×10 6 CFU / g.

[0046] Example 8 Compared with Example 2, in this example, a method for preparing a three-level gradient porous carbon nest particle that can capture near-surface microbial aerosols includes step S1: high-temperature aerobic fermentation of earthworm castings, controlling the pile temperature at 65°C for 18 days, and after fermentation, crushing the material and passing it through a 100-mesh sieve to obtain an earthworm castings composite carbon matrix; taking attapulgite powder, adding room temperature water at a powder-to-water ratio of 1:0.8, stirring into a slurry, and letting it stand for 32 minutes to obtain aged attapulgite; taking sodium alginate and pregelatinized starch, adding 45°C warm water and stirring until completely dissolved, the amount of warm water added being 4 times the combined mass of sodium alginate and pregelatinized starch, and then adding silica sol and mixing evenly to obtain an organic-inorganic composite binder.

[0047] Example 9 Compared with Example 2, in this example, a method for preparing a three-level gradient porous carbon nest particle that can capture near-surface microbial aerosols includes step S1: drying earthworm castings with hot air at 105°C for 110 min, crushing the dried material, and passing it through a 100-mesh sieve to obtain an earthworm castings composite carbon matrix; taking attapulgite powder, adding room temperature water at a powder-to-water ratio of 1:0.8, stirring into a slurry, and allowing it to stand for 32 min to obtain aged attapulgite; taking sodium alginate and pregelatinized starch, adding 45°C warm water and stirring until completely dissolved, the amount of warm water added being 4 times the combined mass of sodium alginate and pregelatinized starch, and then adding silica sol and mixing evenly to obtain an organic-inorganic composite binder.

[0048] Example 10 Compared with Example 2, in this example, the granulated particles are dried at 50°C for 135 min and at 70°C for 135 min in sequence, and the rest are the same as in Example 2.

[0049] Example 11 Compared with Example 2, in this example, the granulated particles are dried at 50°C for 135 min and at 105°C for 135 min in sequence, and the rest is the same as in Example 2.

[0050] Example 12 Compared with Example 2, in this example, the granulated particles are dried at 70°C for 135 min and at 105°C for 135 min in sequence, and the rest is the same as in Example 2.

[0051] Example 13 Compared with Example 2, in this example, the granulated particles are dried at 105°C for 270 min in sequence, and the rest of the process is the same as in Example 2.

[0052] Example 14 Compared with Example 2, in this example, the granulated particles are dried sequentially at 30°C for 90 min, 50°C for 90 min, and 90°C for 90 min, with the remaining parts being the same as in Example 2.

[0053] Example 15 Compared with Example 2, in this example, the granulated particles are dried sequentially at 70°C for 90 min, at 90°C for 90 min, and at 120°C for 90 min, with the remaining parts being the same as in Example 2.

[0054] Experimental Example 1 The three-level gradient porous carbon nest particles prepared in Examples 1-15 were spread on the soil surface with a thickness of 1.5 cm. After 15 days, samples were taken to test the microbial composition inside the particles. The colonization of beneficial bacteria and the interception rate of indigenous bacteria in the three-level gradient porous carbon nest particles prepared in Examples 1-9 were detected and recorded in Table 1. The colonization of beneficial bacteria in the three-level gradient porous carbon nest particles prepared in Examples 10-15 were detected and recorded in Table 2. The method for detecting the colonization of beneficial bacteria is as follows: Weigh 10.0 g of intact granule sample and place it in a sterile Erlenmeyer flask containing 90 mL of sterile physiological saline. Shake at 120 r / min for 5 min to elute soil microorganisms adsorbed on the surface of the granules. Discard all eluent, remove the granules, and rinse them three times with 50 mL of sterile pure water for 10 s each time to thoroughly remove residual microorganisms on the surface. Drain and set aside. Place the sterilized clean granules in a sterile mortar and grind them gently until they are in uniform powder form. Transfer all the powder to 90 mL of sterile physiological saline and shake at 200 r / min for 30 min at a constant temperature to fully disperse the colonizing bacteria inside the pores of the granules, thus preparing 10 g of beneficial bacteria colonization. 1 Gradient bacterial suspension, diluted with sterile physiological saline to 10 1 The bacterial suspension was serially diluted 10-fold to prepare multiple gradient dilutions. 100 μL of each gradient dilution was evenly spread onto NA nutrient agar plates, with three technical parallel plates for each dilution. The plates were labeled and inverted in a 30°C incubator for 48 hours in the dark. Plates with colony counts between 30 and 300 CFU were selected for counting. Plates with excessive, insufficient, or contaminated colonies were discarded. Microscopic observation was performed after counting to eliminate interference from small fungal colonies and ensure that only beneficial bacteria were counted. The average value of the three sets of biological parallel samples was taken as the final result. Beneficial bacteria colony count = average plate colony count × dilution factor × 100. Method for detecting the interception rate of indigenous bacteria: Under aseptic conditions, accurately weigh 10.0 g of the intact test particle sample and place it in a 90 mL sterile saline Erlenmeyer flask. Gently shake at 120 r / min for 5 min to elute only the pathogenic fungal spores attached to the particle surface, obtaining a microbial suspension on the outside of the particle. Perform a 10-fold serial dilution of the suspension, and take 100 μL of each dilution to spread on Bengal Red / PDA fungal agar plates. Set up three technical replicates for each dilution. Incubate at 28 ℃ inverted for 72 h. Select effective plates of 30~300 CFU to count the total number of colonies and convert them to obtain the pathogenic fungal content on the outside of the particle, which is recorded as N0. Collect the intact particles after shaking, wash three times with sterile pure water to remove residual spores on the surface, grind the particles into powder, add 90 mL of sterile saline, shake at 200 r / min for 30 min to fully extract the residual fungal spores inside the particles, and perform a 10-fold serial dilution of the suspension, taking 100 μL of each dilution to spread on a Bengal Red / PDA fungal agar plate. μL of the diluted solution was spread onto Bengal Red / PDA fungal culture plates, with three technical replicates for each dilution. The plates were incubated at 28 °C for 72 h in an inverted manner. Plates with effective CFU (30–300 CFU) were selected for colony counting. The total colony count was calculated, and the pathogenic fungal penetration content inside the particles was determined, denoted as μL. Take an equal amount of unspread granules from the original blank soil and follow the complete fungal testing procedure described above to test the background pathogenic fungi content of the soil itself, which is recorded as Nblank and used to eliminate background interference from the soil matrix. N0 ′ =N0 Nblank (corrected true spore exposure on particle surface). N1 ′ =N1 Nblank (corrected number of actual penetrating spores inside the particle). Note: If the corrected value is negative, it will be calculated as 0. Indigenous bacteria interception rate = ; Note: After correction, N1 ′ When the value is 0, it is determined that no pathogenic fungal spores are detected inside the particle under this detection condition, and the interception rate is 100%.

[0055] The test results are shown in Tables 1 and 2: Table 1 Performance test results of Examples 1-9

[0056] Table 2 Performance test results of Examples 10-15

[0057] As shown in Tables 1 and 2, comparing Example 2 with Examples 4-6, it was found that removing one or both of rice husk ash and diatomaceous earth affected the pore size of the three-gradient porous carbon nest particles, resulting in a decrease in the colonization of beneficial bacteria and a decrease in the interception rate of indigenous bacteria.

[0058] Comparing Examples 2 and Examples 7-9, it can be seen that Example 7 did not undergo high-temperature aerobic fermentation and high-temperature drying inactivation treatment. The background microbial community occupied more than 99% of the pores, and the target indigenous bacteria could not colonize. High-temperature aerobic fermentation alone could not completely kill the spores, and high-temperature drying alone, although retaining more signal substances, did not completely kill the spores. When high-temperature aerobic fermentation and high-temperature drying inactivation were carried out simultaneously, although the retention rate of signal substances was slightly lower, complete sterility was achieved, and the target bacteria capture amount was the highest.

[0059] Comparing Examples 2 and 10-15, it can be seen that direct drying in one stage causes rapid evaporation of moisture, and the adhesive network does not have time to shrink slowly before penetrating cracks occur; the two-stage method lacks a step, resulting in insufficient shrinkage of the adhesive or excessive temperature difference, leading to cracks; the low-temperature combination has a good appearance but is not thoroughly dried, resulting in insufficient particle strength; the high-temperature combination has surface charring and severe cracks. When the three-stage drying method of this scheme is adopted, the gel of sodium alginate and pregelatinized starch is fully shrunk and pores are formed, while cracks are avoided, and the colonization of beneficial bacteria and the interception rate of indigenous bacteria are both improved.

[0060] Experimental Example 2 The three-level gradient porous carbon nest particles prepared in Example 2 were spread on the soil surface to a thickness of 1.5 cm. Samples were taken at 7, 15, and 30 days to detect the microbial composition of the soil inside and around the particles. Particle samples were aseptically cut open, and soil samples were collected from the inside of the particles (mesoporous region), the particle surface, and at different distances (2 mm, 5 mm, 8 mm, and 10 mm) for plate counting and microbial identification.

[0061] The test results are shown in Table 3: Table 3 Performance test results of Example 2

[0062] Note: The abundance of pathogenic fungi is expressed as a relative value of 1.0 for the control soil without granules.

[0063] Table 3 shows that beneficial bacteria rapidly colonize and continuously multiply inside the particles, while pathogenic fungi were never detected inside the particles. The abundance of pathogenic fungi in the soil at distances of 2 mm, 5 mm, and 8 mm from the particles was significantly lower than that of the control. The inhibitory effect was strongest at 2 mm (pathogen abundance decreased to 0.28), followed by 5 mm (0.41), and still showed a significant inhibitory effect at 8 mm (0.72). The inhibitory effect decreased at 10 mm (0.93). This confirms the existence of the biological protective layer in the particles of this invention, with an antibacterial activity area radius of approximately 8 mm and an effective antibacterial core area radius of approximately 5 mm.

[0064] Experimental Example 3 The three-level gradient porous carbon nest particles prepared in Example 2 were spread on the surface of soil with continuous cropping obstacles to a thickness of 1.5 cm, at a rate of 820 kg per mu (approximately 667 square meters). Soil microbial composition and crop growth indicators were measured at 30, 60, and 90 days. The total number of beneficial bacteria in the soil before application was 5.2 × 10⁻⁶. 5 CFU / g, soil pathogenic fungal abundance (relative value) was 1.0, crop plant height growth rate (relative control) was not applicable, and soil-borne disease incidence rate was 32%.

[0065] The test results are shown in Table 4: Table 4 Performance test results of Example 2

[0066] As shown in Table 4, after applying the granules of this invention, beneficial bacteria in the soil continued to proliferate, the abundance of pathogenic fungi continued to decrease, crop growth was significantly improved, and the incidence of soil-borne diseases decreased from 32% to 7%, verifying the complete microecological regulation function of the granules of this invention: selectively capturing beneficial bacteria, actively inhibiting harmful bacteria, and forming a biological protective layer.

[0067] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A three-level gradient porous carbon nest particle capable of capturing near-surface microbial aerosols, characterized in that, The three-level gradient porous carbon nest particles are homogeneous porous structures with a particle size of 3~6mm. The three-level gradient porous carbon nest particles form a three-level gradient interconnected pore system of micropores-mesopores-macropores inside. The pore size of the micropores is 0.02~0.5μm; The diameter of the central hole is 1~10μm; The pore size of the macropore is 20~100μm.

2. The three-level gradient porous carbon nest particle capable of capturing near-surface microbial aerosols according to claim 1, characterized in that, The total pore volume of the three-level gradient porous carbon nest particles accounts for 28% to 35% of the total pore volume of the three-level gradient porous carbon nest particles, the micropores account for 8% to 12% of the total pore volume, the mesopores account for 18% to 22% of the total pore volume, and the macropores account for 55% to 65% of the total pore volume.

3. The three-level gradient porous carbon nest particle capable of capturing near-surface microbial aerosols according to claim 1, characterized in that, The three-level gradient porous carbon nest particles comprise the following raw materials in parts by weight: 40-65 parts earthworm castings composite carbon matrix, 10-20 parts diatomaceous earth, 8-15 parts rice husk ash, 20-30 parts attapulgite, 5-10 parts hydrated alumina, 5-10 parts bentonite, 3-8 parts zeolite, and 3-8 parts organic-inorganic composite binder.

4. The three-level gradient porous carbon nest particle capable of capturing near-surface microbial aerosols according to claim 3, characterized in that, The earthworm castings composite carbon matrix is ​​an inactivated earthworm castings composite carbon matrix, which is obtained by sequentially subjecting earthworm castings to high-temperature aerobic fermentation and high-temperature drying inactivation treatment.

5. A three-level gradient porous carbon nest particle capable of capturing near-surface microbial aerosols according to claim 4, characterized in that, The temperature of the high-temperature aerobic fermentation pile is 60~70℃, the high-temperature aerobic fermentation time is 15~20 days, the high-temperature drying temperature is 105℃, and the high-temperature drying time is 90~120 minutes.

6. A three-level gradient porous carbon nest particle capable of capturing near-surface microbial aerosols according to claim 3, characterized in that, The organic-inorganic composite adhesive comprises sodium alginate, pregelatinized starch, and silica sol in a mass ratio of 2:2:4~5.

7. A method for preparing a three-level gradient porous carbon nest particle capable of capturing near-surface microbial aerosols, used to prepare the three-level gradient porous carbon nest particle capable of capturing near-surface microbial aerosols as described in any one of claims 1 to 6, characterized in that, Includes the following steps: The earthworm castings composite carbon matrix, diatomaceous earth, rice husk ash, hydrated alumina, bentonite and zeolite are mixed evenly, aged attapulgite is added, and after stirring, the organic-inorganic composite binder is sprayed on. After granulation, drying and cooling, the three-level gradient porous carbon nest particles are obtained.

8. The method for preparing three-level gradient porous carbon nest particles capable of capturing near-surface microbial aerosols according to claim 7, characterized in that, The granulation tilt angle is 45°~55°, the granulation rotation speed is 22~28 r / min, and the granulation time is 25~30 min.

9. The method for preparing a three-level gradient porous carbon nest particle capable of capturing near-surface microbial aerosols according to claim 7, characterized in that, The drying process is a three-stage drying process, with different temperatures for the first, second, and third stages, and the same drying time for each stage.

10. The method for preparing a three-level gradient porous carbon nest particle capable of capturing near-surface microbial aerosols according to claim 9, characterized in that, The temperature of the first drying stage is 48~52℃, and the drying time is 85~95min. The temperature of the second drying stage is 65~75℃, and the drying time is 85~95min. The temperature of the third drying stage is 100~110℃, and the drying time is 85~95min.

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