Composite material as well as preparation method and application thereof

Abstract

The invention discloses a composite material as well as a preparation method and application thereof. The composite material comprises a core, a shell layer and a satellite body, the material of the core comprises an organic matter slow-release material; the material of the shell layer comprises a porous mineral material loaded with an electron shuttle, and the shell layer coats the core; the material of the satellite body comprises a Fe3O4 and iron reducing bacteria compound; and the satellite body is adsorbed on the surface of the shell layer. The composite material provided by the invention realizes integration of positioning, activation and slow release, can be actively anchored on the surface of a soil mineral needing to be activated, can accurately activate the soil mineral in situ and maintain the continuity of an iron reduction process, and releases fixed nutritional ingredients in soil.

Description

Technical Field

[0001] This invention relates to the field of agricultural and soil improvement technology, and in particular to a composite material, its preparation method, and its application. Background Technology

[0002] Soil is the foundation of agricultural production and ecosystem health, and its nutrient supply capacity directly determines crop yield and quality. For a long time, the main goals of soil improvement have been to enhance fertility, improve structure, regulate pH, and remediate pollution. However, traditional soil improvement techniques largely rely on adding exogenous fertilizers to the soil to supplement key nutrients such as nitrogen, phosphorus, and potassium. While this "exogenous input"-dominated model can increase the content of available nutrients in the soil in the short term, it also brings a series of prominent problems. Long-term excessive application of chemical fertilizers can easily lead to soil compaction, acidification, salinization, and microbial community imbalance, increase agricultural production costs, cause nutrient loss, and contribute to environmental problems such as eutrophication of water bodies.

[0003] The more fundamental technical bottleneck lies in the fact that existing soil improvement methods are significantly insufficient in their ability to efficiently and sustainably activate the inherent nutrients in the soil. In fact, most soils (especially some low- to medium-yield fields or obstacle soils) contain abundant potential nutrient reserves in their mineral lattices or organic matter, such as fixed, unavailable phosphorus and potassium micronutrients. These inherent nutrients are difficult for crops to directly absorb and utilize, leading to the paradoxical phenomenon of "rich soil but poor crops." Summary of the Invention

[0004] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, an object of the present invention is to provide a composite material. A second object of the present invention is to provide a method for preparing this composite material. A third object of the present invention is to provide applications of this composite material.

[0005] The inventive concept of this invention is as follows:

[0006] To address the problem that existing soil improvement technologies rely on exogenous fertilizers and cannot efficiently activate the soil's inherent nutrients, this invention provides a composite material. This material consists of an organic slow-release material as the core, a porous mineral material loaded with electron shuttles as the shell, and a Fe3O4@iron-reducing bacteria complex adsorbed on the surface of the shell to form satellites. This invention utilizes the organic matter in the core to provide electrons to the iron-reducing bacteria, and uses Fe3O4 and the porous mineral material to colonize the bacteria. In the anaerobic microenvironment of the soil, the iron reduction process is activated. An efficient electron transport chain is constructed through the electron shuttles to target and reduce iron / manganese oxides in the soil, thereby releasing the fixed phosphorus, potassium, and other nutrients in situ. The porous mineral material adsorbs and controls the slow release of these available nutrients. The high affinity of Fe3O4 in the satellite of this invention for soil iron oxides allows it to actively anchor itself on the surface of soil minerals (such as hematite and goethite) that need to be activated, thereby enabling the composite material to achieve precise activation "point-and-shoot". It can be well used to activate the inherent insoluble nutrients in acidic, gypsumy, and other soils with high iron and manganese oxide content. It can be used as a highly efficient soil conditioner in sustainable agriculture, significantly reducing the amount of chemical fertilizers used.

[0007] To achieve the above objectives, the present invention provides the following technical solution.

[0008] In a first aspect, the present invention provides a composite material comprising a core, a shell, and a satellite body; The core material includes organic slow-release materials; The shell material includes a porous mineral material that carries an electron shuttle, and the shell encapsulates the core. The satellite body is made of Fe3O4@iron-reducing bacteria complex, and the satellite body is adsorbed on the shell surface.

[0009] Specifically, the organic matter slow-release material acts as an initial electron donor, providing electrons to iron-reducing bacteria and activating the iron reduction process in the anaerobic microenvironment of the soil. The shell layer, which encapsulates the core and serves as an adsorption carrier for the satellite, comprises a porous mineral material loaded with electron shuttles. These electron shuttles construct an efficient electron transport chain, targeting and reducing soil iron / manganese oxides, thereby releasing fixed nutrients such as phosphorus and potassium in situ. The porous mineral material adsorbs and controls the slow release of these available nutrients. The satellite comprises a Fe3O4@iron-reducing bacteria complex, which, as a satellite, has the following multiple functions: (1) Targeted anchoring: Fe3O4 in the Fe3O4@iron-reducing bacteria complex has biomimetic properties and a natural high affinity for other iron oxides widely present in soil (such as hematite α-Fe2O3 and goethite α-FeOOH). This enables it to actively and firmly anchor on the surface of soil mineral particles that need to be activated, greatly shortening the distance of electron transfer and achieving precise spatial positioning that can "hit wherever it is pointed at". (2) Electron bridge: As a mixed valence mineral, Fe3O4 has excellent electronic conductivity. It can act as a nanowire between iron-reducing bacterial cell membrane proteins (such as C-type cytochrome) and soil solid minerals, making it easier for electrons to be transferred to soil iron minerals, thereby promoting the iron reduction process. (3) Energy buffering and cycling: Iron-reducing bacteria reduce Fe 3+ The generated Fe 2+ It is unstable in soil and can be oxidized or participate in other reactions. The Fe in Fe3O4... 2+ / Fe 3+ The cycle can act as a local redox buffer, which helps maintain the stability of the reaction microenvironment and prolong the duration of the activation reaction; (4) Indicative function: The black color of Fe3O4 can serve as a visual indicator of material distribution. In soil, if the local reduction conditions are strong, some Fe3O4 may be further reduced or transformed. Its magnetic strength or phase change can be monitored by specialized equipment. Therefore, the extent of the iron reduction reaction can be monitored, thereby controlling the amount of composite material applied.

[0010] In this invention, Fe3O4 is a multifunctional intelligent unit integrating "positioning", "electronic wire", "metabolic switch" and "structural stabilizer". It is not just a material component, but also a core engineering design to realize a series of advanced functions such as "precise spatial positioning", "time-on-demand response" and "efficient process catalysis".

[0011] Therefore, in contrast to traditional magnetic separation and recovery technologies, this invention takes a different approach, providing a composite material capable of precisely activating soil minerals in situ. Through a core-shell-satellite structure, it achieves a composite material integrating positioning, activation, and slow release. This material actively anchors itself to the surface of the soil minerals to be activated, achieving precise activation and maintaining the continuous iron reduction process, releasing nutrients fixed in the soil. This invention realizes a shift from "external fertilization" to "internal living," achieving the orderly slow release of organic carbon sources and the targeted colonization and protection of functional microorganisms. It can be effectively used to activate inherent insoluble nutrients in acidic, gypsum-rich, and other soils with high iron and manganese oxide content. It can serve as a highly efficient soil conditioner in sustainable agriculture, significantly reducing the amount of chemical fertilizers used.

[0012] Preferably, in the composite material, the core content is 35% to 45% by mass percentage, the shell content is 55% to 65%, and the satellite content is 3% to 10%.

[0013] More preferably, the core content in the composite material is 36% to 42% by mass percentage; even more preferably, the core content in the composite material is 37% to 40% by mass percentage.

[0014] More preferably, the shell content in the composite material is 57-63% by mass percentage; even more preferably, the shell content in the composite material is 58-62% by mass percentage.

[0015] More preferably, the content of the satellite in the composite material is 3% to 8% by mass percentage; even more preferably, the content of the satellite in the composite material is 4% to 6% by mass percentage.

[0016] Preferably, the organic matter slow-release material includes a rapidly degradable material and a structural support material; the rapidly degradable material includes at least one of polyhydroxyalkanoates, polylactic acid, starch, thermoplastic starch, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), and polymalic acid; the structural support material includes at least one of lignin, humic acid, cellulose, hemicellulose, biochar, and chitosan.

[0017] Preferably, the mass ratio of the rapidly degradable material to the structural support material is 1:(0.2~0.6); more preferably, the mass ratio of the rapidly degradable material to the structural support material is 1:(0.25~0.55); even more preferably, the mass ratio of the rapidly degradable material to the structural support material is 1:(0.3~0.5); and even more preferably, the mass ratio of the rapidly degradable material to lignin is 1:(0.35~0.48).

[0018] Preferably, the mass ratio of the electron shuttle to the porous mineral material is 1:(15~20); more preferably, the mass ratio of the electron shuttle to the porous mineral material is 1:(16~20); even more preferably, the mass ratio of the electron shuttle to the porous mineral material is 1:(17~20); and even more preferably, the mass ratio of the electron shuttle to the porous mineral material is 1:(18~20).

[0019] Preferably, the electron shuttle comprises at least one of sodium anthraquinone-2,6-disulfonate (AQDS), sodium anthraquinone-2-sulfonate, sodium anthraquinone-2-carboxylic acid, sodium anthraquinone-1,4-disulfonate, 2-hydroxy-1,4-naphthoquinone, ubiquinone, and phenazine-1-carboxylic acid.

[0020] Preferably, the porous mineral material includes at least one of attapulgite (ATP), sepiolite, bentonite, kaolin, zeolite, biochar, and activated carbon.

[0021] More preferably, the attapulgite is acid-modified attapulgite.

[0022] More preferably, the mesh size of the attapulgite is 100-400 mesh; even more preferably, the mesh size of the attapulgite is 150-350 mesh; and even more preferably, the mesh size of the attapulgite is 180-280 mesh.

[0023] Preferably, the iron-reducing bacteria include sulfur-reducing bacteria (Geobacterium thioreti). Geobacter sulfurreducens Metal-reducing bacteria (Geobacter metallireducens), Lovelacebacterium (Geobacter lovleyi) Oneda Sheva (Shewanella oneidensis MR-1) At least one of them.

[0024] Preferably, the adsorption method includes electrostatic adsorption or magnetic adsorption.

[0025] Preferably, the Fe3O4 in the Fe3O4@iron-reducing bacteria complex is in the form of nanoparticles.

[0026] Preferably, the mass ratio of Fe3O4 in the Fe3O4@iron-reducing bacteria complex in the satellite body is 30%~60%; more preferably, the mass ratio of Fe3O4 in the Fe3O4@iron-reducing bacteria complex in the satellite body is 40%~60%; and even more preferably, the mass ratio of Fe3O4 in the Fe3O4@iron-reducing bacteria complex in the satellite body is 50%~60%.

[0027] Preferably, the particle size of the core is 80-120 μm; more preferably, the particle size of the core is 80-110 μm; and even more preferably, the particle size of the core is 80-100 μm.

[0028] Preferably, the particle size of the composite material is 1.0 mm to 3.0 mm; more preferably, the particle size of the composite material is 1.2 mm to 2.8 mm; and even more preferably, the particle size of the composite material is 1.5 mm to 2.6 mm.

[0029] In a second aspect, the present invention provides a method for preparing the composite material described in the first aspect, comprising the following steps: granulating an organic slow-release material to obtain a core; coating the surface of the organic slow-release material with a porous mineral material loaded with an electron shuttle to form a shell; and then adsorbing the Fe3O4@iron-reducing bacteria complex onto the surface of the shell, and solidifying it to obtain the composite material.

[0030] Preferably, the organic matter slow-release material includes a rapidly degradable material and a structural support material, and the core preparation method is as follows: the rapidly degradable material and the structural support material are melt-blended and then granulated.

[0031] Preferably, the melt blending temperature is 150℃~170℃; more preferably, the melt blending temperature is 152℃~165℃; and even more preferably, the melt blending temperature is 155℃~162℃.

[0032] Preferably, the melt blending time is 7-15 min; more preferably, the melt blending time is 8-12 min; and even more preferably, the melt blending time is 9-11 min.

[0033] Preferably, the porous mineral material loaded with electron shuttle is prepared by adding the porous mineral material to a solution containing electron shuttle, stirring, and centrifuging to obtain the porous mineral material loaded with electron shuttle.

[0034] Preferably, the porous mineral material of the electron shuttle is attapulgite loaded with AQDS, which is prepared by the following method: natural attapulgite is calcined and modified with acid, then the modified attapulgite is dispersed in an AQDS ethanol solution and stirred, centrifuged and washed, and finally vacuum dried to obtain AQDS-ATP powder, which is the attapulgite loaded with AQDS.

[0035] Preferably, the calcination temperature is 400~500℃; more preferably, the calcination temperature is 420~480℃; and even more preferably, the calcination temperature is 440~460℃.

[0036] Preferably, the calcination time is 1-4 hours; more preferably, the calcination time is 1.5-3.5 hours; and even more preferably, the calcination time is 1.8-2.5 hours.

[0037] Preferably, the acid solution includes at least one of hydrochloric acid, sulfuric acid, or nitric acid.

[0038] Preferably, the solid-liquid ratio of the modified attapulgite to the AQDS ethanol solution is 1 g: (30~60) mL; more preferably, the solid-liquid ratio of the modified attapulgite to the AQDS ethanol solution is 1 g: (35~55) mL; even more preferably, the solid-liquid ratio of the modified attapulgite to the AQDS ethanol solution is 1 g: (45~52) mL.

[0039] Preferably, the Fe3O4@iron-reducing bacteria complex is prepared by placing wet iron-reducing bacteria cells in a container containing Fe 3 +The Fe3O4@iron-reducing bacteria were obtained by reacting with an anaerobic buffer solution containing electron donors and centrifuging.

[0040] Preferably, the Fe3O4@iron-reducing bacteria complex is prepared by the following method: Step 1: Inoculate the frozen bacterial strain into the culture medium and anaerobic culture to obtain iron-reducing bacteria solution; Step 2: Centrifuge the iron-reducing bacteria solution and resuspend the resulting wet bacterial mass in a solution containing Fe. 3+ The Fe3O4@iron-reducing bacteria complex was obtained by reacting the Fe3O4@iron-reducing bacteria complex in an anaerobic buffer solution containing electron donors, followed by centrifugation and washing after the reaction.

[0041] Preferably, the culture medium in step 1 comprises 1.5~2 g / L NH4Cl, 0.1~0.3 g / L KCl, 0.6~0.8 g / L NaH2PO4·H2O, 0.1~0.3 g / L NaCl, 1~2 mL / L vitamin solution, 1~2 mL / L trace element solution, 2.5~4 g / L NaHCO3, 10~20 mM sodium acetate and 20~40 mM sodium fumarate.

[0042] More preferably, the vitamin solution contains at least 20-40 μg / L biotin, 20-40 μg / L folic acid, 50-80 μg / L B1, or 1-5 μg / L vitamin B1. 12 .

[0043] More preferably, the trace element solution contains at least 500-800 μg / L Mn, 100-400 μg / L Fe, 100-300 μg / L Co, 100-300 μg / L Zn, 10-50 μg / L Cu or 10-50 μg / L Mo.

[0044] Preferably, in step 1, the specific method for anaerobic culture is as follows: 0.5-1 mL of frozen bacterial culture is inoculated into an anaerobic serum bottle containing 5-10 mL of culture medium; the culture is then incubated statically in the dark at 30°C for 3-7 days; and samples are taken to monitor the OD of the bacterial culture. 600 After inoculating to 0.1-0.2, transfer to new culture medium at an inoculation rate of 1-5% (v / v), continue static incubation at 30°C in the dark, and monitor the bacterial OD. 600 When the concentration reaches 0.6-0.8, the culture is stopped to obtain the iron-reducing bacteria culture. At this point, the bacteria are in the late logarithmic growth phase and have the strongest metabolic activity.

[0045] Preferably, in step 2, the electron donor includes at least one of sodium lactate, sodium acetate, and sodium formate.

[0046] Preferably, in step 2, Fe is present. 3+In the anaerobic buffer solution with electron donors, Fe 3+ The concentration is 7~15 nM; more preferably, in step 2, Fe is contained. 3+ In the anaerobic buffer solution with electron donors, Fe 3+ The concentration is 8~12 nM.

[0047] Preferably, in step 2, Fe is present. 3+ In the anaerobic buffer containing electron donors, the concentration of electron donors is 3-8 mM; more preferably, it contains Fe 3+ In the anaerobic buffer containing electron donors, the concentration of electron donors is 4-6 mM.

[0048] Preferably, the anaerobic buffer solution comprises an anaerobic phosphate buffer solution.

[0049] Preferably, in step 2, the reaction is carried out in a constant temperature shaker at a temperature of 28-32°C; more preferably, the reaction is carried out in a constant temperature shaker at a temperature of 29-31°C.

[0050] Preferably, in step 2, the reaction time is 45-55 hours; more preferably, the reaction time is 46-50 hours.

[0051] Preferably, in the preparation method of the composite material, a binder is used to coat the porous mineral material carrying the electron shuttle onto the core surface.

[0052] Thirdly, the present invention provides a soil conditioner comprising the composite material described in the first aspect.

[0053] Fourthly, the present invention provides the application of the composite material described in the first aspect or the soil conditioner described in the third aspect in soil remediation or agricultural production.

[0054] Preferably, the soil remediation includes activating nutrients in the soil and improving nitrogen fertilizer productivity.

[0055] Fifthly, the present invention provides a method for soil remediation, wherein the method comprises adding the soil conditioner described in the fourth aspect to the soil, wherein the soil conditioner accounts for 0.1% to 1.0% of the soil by mass.

[0056] The beneficial effects of this invention are: (1) This invention provides a composite material capable of precisely activating soil minerals in situ. It uses an organic slow-release material as the core and a porous mineral material loaded with electron shuttles as the shell, with Fe3O4@iron-reducing bacteria complex adsorbed on the surface of the shell to form satellites. This composite material integrates localization, activation, and slow release. It can actively anchor itself to the surface of the soil minerals to be activated, achieving precise activation and maintaining the continuous iron reduction process, releasing nutrients fixed in the soil.

[0057] (2) The preparation method of the composite material of the present invention is simple and convenient, the raw materials are readily available and environmentally friendly, and no complex equipment is required. The composite material can be constructed by using a coating granulator.

[0058] (2) This invention realizes the transformation from "external fertilization" to "internal life-oriented", realizes the orderly slow release of organic carbon source, the targeted colonization and protection of functional microorganisms, and can be used to activate the inherent insoluble nutrients in acidic, fertile and other soils with high iron and manganese oxide content. It can be used as an efficient soil conditioner in sustainable agriculture and significantly reduce the amount of chemical fertilizers applied. Attached Figure Description

[0059] Figure 1 This is a schematic diagram of the structure of the composite material in Embodiment 1 of the present invention.

[0060] Attached figures: 1 for core, 2 for shell, 3 for satellite body. Detailed Implementation

[0061] To enable those skilled in the art to better understand this application, the present invention will be further described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely preferred embodiments of the present invention, and the scope of protection of the present invention should be determined by the scope defined in the claims.

[0062] In the description of this invention, it should be noted that unless specific conditions are specified in the examples, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0063] The embodiments of the present invention used Geobacter sulfurreducens The strain was purchased from the American Type Culture Collection (ATCC), catalog number ATCC 51573.

[0064] Furthermore, to better illustrate the present invention, numerous specific details are provided in the following detailed embodiments. Those skilled in the art should understand that the present invention can be practiced without certain specific details. In some embodiments, materials, methods, and means well-known to those skilled in the art are not described in detail in order to highlight the spirit of the invention.

[0065] Example 1: Composite Materials A composite material, the structural schematic diagram of which is shown below. Figure 1 As shown, it includes a core 1, a shell 2, and satellites 3; wherein, the core 1 is made of polyhydroxyalkanoates and lignin; the shell 2 is made of attapulgite loaded with AQDS, and the shell 2 covers the core 1; the satellite 3 is made of Fe3O4@ Geobacter sulfurreducens The complex, satellite 3, is adsorbed on the surface of shell 2.

[0066] The above-mentioned composite material was prepared using the following method: S1: Preparation of Fe3O4@ Geobacter sulfurreducens complex: S1.1: Preparation of culture medium: The culture medium composition is 1.5 g / L NH4Cl, 0.1 g / L KCl, 0.6 g / L NaH2PO4·H2O, 0.1 g / L NaCl, and 1 mL / L vitamin solution (the vitamin solution contains 20 μg / L biotin, 20 μg / L folic acid, 50 μg / L VB1 and 1 μg / L VB2). 12 The medium consisted of 1 mL / L trace element solution (containing 500 μg / L Mn, 100 μg / L Fe, 100 μg / L Co, 100 μg / L Zn, 10 μg / L Cu, and 10 μg / L Mo), 2.5 g / L NaHCO3, 15 mM sodium acetate (as electron donor), and 30 mM sodium fumarate (as electron acceptor). The pH of the culture medium was 6.8–7.0.

[0067] S1.2: Strain expansion and culture: On the anaerobic operating table, inoculate 1 mL of frozen bacterial culture into an anaerobic serum bottle containing 10 mL of fresh culture medium prepared with S1.1. Incubate statically at 30°C in the dark for 3-7 days. During the incubation period, slight turbidity or black flocculent matter may be observed in the culture medium. Monitor the bacterial culture in the bottle. Once the bacterial cells in the bottle show stable growth (OD), the culture is considered complete. 600 The inoculum concentration was 0.1–0.2 g / L. The culture was then transferred to fresh culture medium at a 3% (v / v) inoculation rate, and subsequently incubated statically at 30°C in the dark while monitoring. The OD of the bacterial culture was then measured. 600 When the value is 0.6~0.8, Geobacter sulfurreducens At the late logarithmic growth stage, metabolic activity is at its peak, and culture is stopped to obtain... Geobacter sulfurreducens Bacterial solution.

[0068] S1.3: The obtained Geobacter sulfurreducensCentrifuge the bacterial culture to collect wet cells. Wash the wet cells with anaerobic phosphate buffer (50 mM, pH 7.0). Resuspend the washed wet cells in anaerobic buffer containing 10 mM FeCl3·6H2O and 5 mM sodium lactate (pH=7.0), and then react slowly in a shaker at 30°C for 48 hours. Geobacter sulfurreducens Using electrons provided by sodium lactate, Fe is converted into Fe through its unique reductase and extracellular polymeric substances. 3+ Nanoscale Fe3O4 particles were reduced and induced to attach to the bacterial cell surface and periplasmic space. After the reaction, the cells were washed three times by centrifugation with anaerobic PBS buffer to obtain Fe3O4@ Geobacter sulfurreducens The complex was stored anaerobically at 4°C for later use.

[0069] S2: Preparation of shell material (ATP loaded with AQDS): S2.1: Calcine 200-mesh natural attapulgite at 450℃ for 2 hours, then place it in 0.5 M HCl solution (solid-liquid ratio 1:10), stir at 60℃ for 4 hours, wash until neutral, and then dry to obtain modified attapulgite. S2.2: The modified attapulgite was dispersed in a 0.1 mM AQDS ethanol solution at a solid-liquid ratio of 1:50 and magnetically stirred for 24 hours under light-protected conditions. The solid was collected by centrifugation, washed with a small amount of ethanol to remove physically adsorbed AQDS, and finally vacuum dried at 60°C. The solid was then ground through a 200-mesh sieve to obtain AQDS-ATP powder, which is the shell material.

[0070] S3: Assembled polyhydroxyalkanoate (PHA)-lignin core S3.1: PHA and lignin are melt-blended in an internal mixer at 160°C for 10 minutes at a mass ratio of 7:3 to obtain a blend; S3.2: The blend is hot-pressed and crushed, and then mechanically granulated to form PHA-lignin microspheres with a particle size of 80-120μm, which are the core.

[0071] S4: Composite material assembly: S4.1: Using PHA-lignin microspheres as the substrate and a 2% (w / v) gelatin solution as the binder, AQDS-ATP powder and PHA-lignin microspheres are thoroughly mixed in a granulation and coating machine to ensure that the AQDS-ATP powder is uniformly coated on the surface of the PHA-lignin microspheres. The weight gain of the coating is controlled to be 150% of the core mass, thus forming particles with a shell coating the core. S4.2: When the coating is about to end and the shell surface still has an adhesive effect, apply Fe3O4@ Geobacter sulfurreducens The composite was mixed with the particles in S4.1, making Fe3O4@ Geobacter sulfurreducens Electrostatic adsorption occurs on the shell surface; S4.3: Adsorbed Fe3O4@ Geobacter sulfurreducens The particles were immersed in a 2% sodium alginate solution for 5 seconds, then removed and placed in a 0.5M CaCl2 solution for 30 seconds to crosslink and form a stable microcapsule structure. Finally, the particles were vacuum dried at 40°C to constant weight to obtain the composite material.

[0072] Example 2 The difference between this embodiment and Embodiment 1 is that the core material includes polylactic acid and cellulose, while the rest is the same as in Embodiment 1.

[0073] Example 3 The difference between this embodiment and Embodiment 1 is that the iron-reducing bacteria is metal-reducing Gastrobacterium, while the rest are the same as in Embodiment 1.

[0074] Example 4 The difference between this embodiment and Embodiment 1 is that the electron shuttle is 2-hydroxy-1,4-naphthoquinone, while the rest are the same as in Embodiment 1.

[0075] Example 5: Methods for Soil Remediation This embodiment provides a method for soil remediation: the composite material in Example 1 is applied to the soil as a soil conditioner, and the composite material accounts for 0.3% of the mass of the soil.

[0076] Actual test The composite materials used in Examples 1-4 exhibit similar technical effects as soil conditioners. Taking the composite material from Example 1 as an example, a 60-day pot experiment (with rice cultivation) was conducted using it as a soil conditioner on acidic red soil in southern China. The specific experimental method is as follows: 1. Soil preparation for testing: Soil collection: Select acidic red soil from the south, collect soil from the top layer (0~20cm), and remove visible plant residues and stones.

[0077] Soil pretreatment: air dry naturally, pass through a 2mm sieve, mix well and set aside. The soil pH is 5.5, the available phosphorus content is 5 mg / kg, the available potassium content is 78.3 mg / kg, and the Fe(II) content is 96.1 mg / kg.

[0078] 2. Experimental Design: Blank control group (CK group): No other materials were applied except for nitrogen fertilizer; Materials handling group: divided into two groups: TM group: The composite material in Example 1 of this invention; PM group: a loose mixture of raw materials A, B, and C; wherein raw material A is a powder (without melt granulation) of PHA and lignin mixed mechanically at a mass ratio of 7:3, and the amount of raw material A is the same as the core content in the TM group composite material; raw material B is the AQDS-ATP powder in Example 1, and the amount is the same as the AQDS-ATP content in the composite material of Example 1; raw material C is Fe3O4@ in Example 1. Geobacter sulfurreducens The powder obtained by freeze-drying the composite wet bacterial mud, with the same amount of raw material C as Fe3O4@ in the composite material of Example 1. Geobacter sulfurreducens The content of the complex.

[0079] Experimental replication: Each treatment group was replicated at least 3 times, using a completely randomized block design.

[0080] Potting procedure: Each pot was filled with 5 kg of pretreated soil, and 15 g of the TM group material and 15 g of the PM group material were added and mixed thoroughly. No additional material was added to the CK group. Then, the TM group, PM group, and CK group were all applied with an equal amount of nitrogen fertilizer (0.5 g / pot). Sterilized rice seeds were sown, and routine water management was implemented. All management conditions were the same for all treatment groups, and the experimental period was 60 days.

[0081] 3. Detection indicators and methods 3.1 Determination of available phosphorus content in soil: The second method (ammonium fluoride-hydrochloric acid extraction method) in NY / T 1121.7-2014 "Soil Testing Part 7: Determination of Available Phosphorus in Soil" was used for determination. The steps are as follows: (1) Extraction: Weigh a certain amount of air-dried soil sample, add the corresponding extractant (0.5M NaHCO3, pH8.5) at a soil-to-liquid ratio of 1:20, shake for 30 minutes, and filter to obtain the extract; (2) Color development and determination: Take an appropriate amount of extract, add molybdenum antimony color development agent, shake well and let stand for 30 minutes for color development. Use a UV-Vis spectrophotometer to measure the absorbance at a wavelength of 880 nm; (3) Calculation: Based on the standard curve, convert the absorbance value into the phosphorus concentration of the extract, and then calculate the available phosphorus content per unit mass of soil (mg / kg).

[0082] 3.2 Determination of available potassium content in soil: The ammonium acetate solution extraction-flame photometry method as described in NY / T 889-2004 "Determination of available and slow-release potassium content in soil" was used. The steps are as follows: (1) Extraction: Weigh the air-dried soil sample, add 1.0 mol / L neutral ammonium acetate solution at a soil-to-liquid ratio of 1:10, shake for 30 minutes, filter, and obtain green leaves; (2) Measurement: The emission intensity of potassium ions in the filtrate was directly measured using a flame photometer; (3) Calculation: Calculate the available potassium content (mg / kg) per unit mass of soil according to the standard curve.

[0083] 3.3 Determination of Fe(II) content in soil: The o-phenanthroline colorimetric method includes the following steps: (1) Fresh soil sample extraction: Weigh a fresh soil sample, add 0.5 M HCl solution in an anaerobic chamber at a soil-to-liquid ratio of 1:10, shake for 30 minutes, and immediately filter to obtain the filtrate; (2) Color development: Take a portion of the filtrate, add sodium acetate buffer to adjust the pH to a suitable range, and then add o-phenanthroline colorimetric reagent to make Fe²⁺ precipitate. + It forms an orange-red complex with phenanthroline; (3) Measurement: The absorbance was measured at a wavelength of 510 nm; (4) Calculation: Calculate the Fe content in the extract based on the standard curve. 2+ The concentration is then converted to the Fe(II) content per unit mass of soil (mg / kg).

[0084] 3.4 Measurement of total crop biomass: Measurement method: After harvesting rice crops, the above-ground parts (stems, leaves, grains) and underground parts (roots) are separated, washed with clean water, and then dried in an oven at 105℃ for 30 minutes, followed by continued drying at 65-70℃ for 48 hours until constant weight. The dry weight is measured using an electronic balance and recorded as the total biomass (g / pot) of each crop.

[0085] 3.5 Calculation of Nitrogen Fertilizer Partial Productivity: The partial productivity of nitrogen fertilizer is calculated using Formula I:

[0086] Formula I In Formula I, the amount of pure nitrogen applied by nitrogen fertilizer refers to the total mass of nitrogen (N) added to the soil through chemical nitrogen fertilizer, in grams; the total biomass of the crop refers to the total biomass of each plant, in grams.

[0087] 3.6 Calculation of Phosphorus Activation Efficiency: In this invention, phosphorus activation efficiency characterizes the ability of the composite material to activate the inherent insoluble phosphorus in the soil, and is calculated using Formula II:

[0088] Formula II In Formula II, the total phosphorus content in the soil is the value obtained by measuring the pretreated soil using the perchloric acid-sulfuric acid digestion method in NY / T 88-1988 "Determination of Total Phosphorus in Soil", and the unit is mg / kg; the available phosphorus content in the soil of the material treatment group is the value obtained by measuring the available phosphorus content in the soil of the TM group and PM group in 3.1, and the unit is mg / kg; the available phosphorus content in the soil of the blank control group is the value obtained by measuring the available phosphorus content in the soil of the blank control group in 3.1, and the unit is mg / kg.

[0089] 4. Test Results The experimental results are shown in Table 1.

[0090] In the experiment, the amount of pure nitrogen applied was 0.230 g, and the total phosphorus content in the soil was 150 mg / kg.

[0091] Table 1. Experimental results of different treatment groups detection indicators CK group TM Group PM Team Available phosphorus content in soil (mg / kg) 4.8 42.3 17.8 Soil available potassium content (mg / kg) 75.2 189.4 110.6 Soil Fe(II) content (mg / kg) 125 485 180.7 Phosphorus activation efficiency (%) - 25% 8.7% Rice biomass (g / pot) 15.6 41.8 24.7 Nitrogen fertilizer partial productivity (PFPN, g / g) 67.8 181.7 107.4 The values ​​in Table 1 are the average values ​​of the three repeated experimental groups.

[0092] As shown in Table 1, the composite material of Example 1 of the present invention has the following beneficial effects: (1) Highly efficient activation of inherent soil nutrients: Without additional application of phosphorus and potassium fertilizers, the available phosphorus and available potassium contents in the soil treated with the TM group of this invention reached 42.3 mg / kg and 189.4 mg / kg, respectively, which were significantly higher than those in the CK group. The phosphorus activation efficiency (the proportion of activated available phosphorus to total phosphorus in the soil) of the TM group reached 25%, which was much higher than that of the CK group. This proves that the composite material of Example 1 of this invention has a strong in-situ activation ability and can efficiently activate the inherent nutrients in the soil; (2) Confirmation of the core mechanism: The soil Fe(II) content in the TM group increased significantly to 485 mg / kg, which is nearly 4 times that of the CK group. This indicates that the composite material successfully drove the iron reduction process, which is also the fundamental reason for the activation of inherent nutrients in the soil; (3) Significantly promotes plant growth: The biomass of rice in the TM group was 168% higher than that in the CK group, proving that the nutrients activated by the composite material can be efficiently utilized by plants.

[0093] (4) Improved fertilizer utilization: Under the premise that all groups were given the same amount of nitrogen fertilizer in the experiment, the nitrogen fertilizer partial productivity (PFPN) of the TM group was as high as 181.7 g / g, which was more than 30% higher than that of the PM group (107.4 g / g). This shows that the benign rhizosphere microenvironment created by the composite material of the present invention simultaneously promotes the absorption and utilization of nitrogen, and achieves the synergistic effect of "increasing nitrogen with carbon (composite material core) and supplementing potassium with active phosphorus".

[0094] (5) Structural superiority: Compared with the CK group, although the PM group can improve the soil available phosphorus content, soil available potassium content, soil Fe(II) content and rice biomass to a certain extent, its effect is not as good as the TM group. This shows that although the applied material composition is the same, the present invention achieves the orderly slow release of organic carbon source, targeted colonization and protection of functional microorganisms, and spatial optimization of electron transport pathway through specific core, shell and satellite structure design. These structural synergistic effects cannot be achieved by simple physical mixing.

[0095] In summary, the composite material of the present invention integrates positioning, activation, and slow release, which can accurately activate soil minerals in situ and maintain the continuous iron reduction process, releasing nutrients fixed in the soil. The released nutrients can be effectively absorbed by crops, promoting crop growth.

[0096] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A composite material, characterized in that, The composite material includes a core, a shell, and a satellite body; The core material includes organic slow-release materials; The shell material includes a porous mineral material that carries an electron shuttle, and the shell covers the core. The satellite body is made of Fe3O4@iron-reducing bacteria complex, and the satellite body is adsorbed on the surface of the shell.

2. The composite material according to claim 1, characterized in that, In the composite material, the core content is 35%~45% by mass percentage, the shell content is 55%~65%, and the satellite content is 3%~10%.

3. The composite material according to claim 1, characterized in that, The organic matter slow-release material includes a rapidly degradable material and a structural support material; the rapidly degradable material includes at least one of polyhydroxyalkanoates, polylactic acid, starch, thermoplastic starch, poly(3-hydroxybutyrate-co-3-hydroxyvalerate), and polymalic acid; the structural support material includes at least one of lignin, humic acid, cellulose, hemicellulose, biochar, and chitosan. And / or, the electron shuttle comprises at least one of sodium anthraquinone-2,6-disulfonate, sodium anthraquinone-2-sulfonate, sodium anthraquinone-2-carboxylic acid, sodium anthraquinone-1,4-disulfonate, 2-hydroxy-1,4-naphthoquinone, ubiquinone, and phenazine-1-carboxylic acid; And / or, the porous mineral material includes at least one of attapulgite, sepiolite, bentonite, kaolin, zeolite, biochar, and activated carbon; And / or, the iron-reducing bacteria include sulfur-reducing *Geobacterium*. 、 At least one of Metal-Reducing Bacillus, Lovrebacterium, and Oneida Shiwab.

4. The composite material according to claim 1, characterized in that, The core has a particle size of 80-120 μm; And / or, the particle size of the composite material is 1.0~3.0 mm.

5. A method for preparing the composite material according to any one of claims 1 to 4, characterized in that, Includes the following steps: The organic slow-release material is granulated to obtain a core; a porous mineral material loaded with electron shuttles is coated on the surface of the core to form a shell; then the Fe3O4@iron-reducing bacteria complex is adsorbed onto the surface of the shell to form a satellite, and after curing, the composite material is obtained.

6. The method for preparing the composite material according to claim 5, characterized in that, The method for preparing the porous mineral material loaded with electron shuttle is to add the porous mineral material to a solution containing electron shuttle, stir, and centrifuge to obtain the porous mineral material loaded with electron shuttle.

7. The method for preparing the composite material according to claim 5, characterized in that, The preparation method of the Fe3O4@iron-reducing bacteria complex is to place the wet cells of iron-reducing bacteria in a container containing Fe 3+ The Fe3O4@iron-reducing bacteria were obtained by reacting with an anaerobic buffer solution containing electron donors and centrifuging.

8. A soil conditioner, characterized in that, The soil conditioner includes the composite material described in any one of claims 1 to 4.

9. The application of the composite material according to any one of claims 1 to 4 or the soil conditioner according to claim 8 in soil management or agricultural production.

10. A method for soil remediation, characterized in that, The soil conditioner according to claim 8 is applied to the soil, wherein the soil conditioner accounts for 0.1% to 1.0% of the soil by mass.

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