Phosphogypsum-based slow-release fertilizer and preparation method thereof

Abstract

The invention discloses an ardealite-based slow release fertilizer and a preparation method thereof, the ardealite-based slow release fertilizer comprises: a core layer, the core layer comprises ardealite and a complex microbial inoculant; in the phosphogypsum, the content of fluoride is less than or equal to 0.1 wt%, and the content of phosphorus pentoxide is more than or equal to 0.1 wt%; the complex microbial inoculants comprise phosphorophilic bacteria; and the material of the coating layer comprises a scene response material. Therefore, according to the ardealite-based slow release fertilizer, the utilization rate of ardealite can be effectively increased, and meanwhile, the slow release performance of the slow release fertilizer is further optimized.

Description

Technical Field

[0001] The present invention belongs to the technical field of phosphogypsum resource utilization, and particularly relates to a calcium-sulfur-phosphorus-silicon slow-release fertilizer based on phosphogypsum and a preparation method thereof. Background Art

[0002] The popularization of chemical fertilizers has played a key role in increasing agricultural production and income. However, traditional phosphate fertilizer production technologies have significant defects. For example, calcium magnesium phosphate fertilizer needs to be sintered at a high temperature of 1400 °C, and the energy consumption per ton of product is as high as 1.2 tons of standard coal, and the utilization rate of available phosphorus (citrate-soluble phosphorus) is only 15-20%; fluorine-containing waste gas is generated during the production of superphosphate, and the fluorine escape rate exceeds 30%. At the same time, a large amount of phosphogypsum by-products are difficult to handle; existing slow-release fertilizers such as sulfur-coated urea have a burst release effect, and the release amount in the first week exceeds 40%, and the coating material is non-degradable, making it difficult to meet the nutrient requirements of crops. At present, countries around the world are seeking new fertilizer sources by means of high-tech.

[0003] Phosphogypsum is the main by-product generated during the production of phosphate fertilizers, and its comprehensive utilization rate is insufficient. Phosphogypsum is rich in calcium (CaO 28-32%), sulfur (SO 3 40-45%), silicon (SiO 2 5-8%) and trace elements (P 2 O 5 0.1-0.5%), and has potential value for resource utilization. However, its fluorine content is as high as 1.0-2.5% (calculated as F), and direct agricultural use will cause soil fluorine pollution. Traditional landfill disposal not only occupies a large amount of land, but also has the risk of fluoride leaching, resulting in the fluoride concentration in groundwater exceeding the standard rate by more than 30%. In addition, in the existing technology, there are also bottleneck problems such as insufficient purification of phosphogypsum, mismatch between nutrient release and crop requirements, and low survival rate of microorganisms in bio-fertilizers. Therefore, how to efficiently and environmentally treat and utilize phosphogypsum and improve its efficiency in agricultural production has become an urgent technical problem to be solved. Summary of the Invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art to a certain extent. For this reason, the present invention provides a phosphogypsum-based slow-release fertilizer and a preparation method thereof. The phosphogypsum-based slow-release fertilizer of the present invention can effectively improve the utilization rate of phosphogypsum, and at the same time further optimize the slow-release performance of the slow-release fertilizer.

[0005] Therefore, in the first aspect of the present invention, the present invention proposes a phosphogypsum-based slow-release fertilizer, comprising: a core layer, the core layer comprising phosphogypsum and a composite microbial agent; in the phosphogypsum, the fluoride content ≤ 0.1 wt%, and the phosphorus pentoxide content ≥ 0.1 wt%; the composite microbial agent includes phosphorus-loving bacteria; a coating layer, the material of the coating layer includes a scene-responsive material. Thus, the present invention effectively improves the utilization rate of phosphogypsum and optimizes the slow-release performance of the slow-release fertilizer.

[0006] In some embodiments, in phosphogypsum, the fluoride content is 0 to 0.1 wt%, and the phosphorus pentoxide content is 0.1 to 5 wt%; and / or, the scenario-responsive material includes any one of a moisture-responsive material, a temperature-responsive material, a pH-responsive material, a microbial degradation-responsive material, a photo-degradation-responsive material, a time-controlled material, a mechanical damage-responsive material, and a temperature-sensitive / photo-sensitive dual-responsive material; and / or, the coating layer includes any one of a PLA-g-AA / humic acid composite film, a sulfur-polylactic acid bilayer film, an EVA-g-MAA film, a sulfur-polycaprolactone composite film, and a PNIPAM-SrAl 2 O 4 :Eu 2+ / Dy 3+ composite film.

[0007] In some embodiments, the composite bacterial agent further includes functional bacteria, and the functional bacteria include at least one of silicate bacteria, salt-tolerant bacteria, potassium-dissolving bacteria, nitrogen-fixing bacteria, and sulfur-oxidizing bacteria; and / or, the composite bacterial agent further includes a magnetic nanocarrier, and the magnetic nanocarrier includes Fe 3 O 4 @SiO 2 .

[0008] In some embodiments, the phosphogypsum-based slow-release fertilizer further includes a slow-release layer located between the core layer and the coating layer; the phosphogypsum-based slow-release fertilizer satisfies at least one of the following: (a) the slow-release layer includes at least one of zeolite and biochar; (b) the core layer further includes thermally activated attapulgite, modified silicon slag, and humic acid organic fertilizer.

[0009] In a second aspect of the present invention, the present invention provides a method for preparing a phosphogypsum-based slow-release fertilizer, which includes the following steps: inoculating a composite bacterial agent into phosphogypsum and performing fermentation treatment to obtain fermentation microspheres; forming the fermentation microspheres into a core layer and forming a coating layer outside the core layer to obtain a slow-release fertilizer precursor; and drying the slow-release fertilizer precursor to obtain the phosphogypsum-based slow-release fertilizer. Thus, according to the method for preparing a phosphogypsum-based slow-release fertilizer of the present invention, a slow-release fertilizer with excellent slow-release performance can be prepared, thereby effectively improving the utilization rate of phosphogypsum and reducing the burst release rate of the slow-release fertilizer at the same time.

[0010] In some embodiments, the preparation method further includes: forming a slow-release layer between the core layer and the coating layer; the slow-release layer includes at least one of zeolite and biochar; and / or, in the step of inoculating a composite bacterial agent into phosphogypsum, it further includes: adding attapulgite, modified silicon slag, and humic acid organic fertilizer, mixing to obtain a mixture.

[0011] In some embodiments, the preparation method satisfies at least one of the following: (1) the mass ratio of phosphogypsum, thermally activated attapulgite, modified silicon slag, and humic acid organic fertilizer is (40 - 90)∶(5 - 30)∶(5 - 20)∶(10 - 30); (2) the thermally activated attapulgite is calcined at 450 - 550 °C; (3) the specific surface area of the modified silicon slag ≥ 250 m 2 / g, the first pore diameter is 2 - 5 nm, and the second pore diameter is 20 - 50 nm; (4) the D50 particle size of the core layer is 0.5 - 2 mm.

[0012] In some embodiments, the composite bacterial agent includes phosphate - loving bacteria and functional bacteria; the composite bacterial agent satisfies at least one of the following: (A) the mass ratio of phosphate - loving bacteria to the functional bacteria is 1∶(1 - 3); (B) the addition amount of the composite bacterial agent is 5 - 10% of the mass of the mixture; (D) the cell concentration of the composite bacterial agent ≥ 1×10 9 CFU / g; (E) the composite bacterial agent further includes 0.5 - 2 wt% magnetic nanocarriers.

[0013] In some embodiments, the conditions for fermentation treatment include: the first fermentation is carried out at 35 - 38 °C for 20 - 24 h, the second fermentation is carried out at 25 - 28 °C for 45 - 50 h, and ultrasonic waves of 35 - 45 kHz are applied every 4 - 6 h, and the power density of the ultrasonic waves is 0.3 - 0.7 W / cm 2 。

[0014] In some embodiments, the coating layer includes any one of PLA - g - AA / humic acid composite film, sulfur - polylactic acid bilayer film, EVA - g - MAA film, sulfur - polycaprolactone composite film, PNIPAM - SrAl 2 O 4 :Eu 2+ / Dy 3+ composite film.

[0015] Compared with the prior art, the beneficial technical effects achieved by the present invention are as follows:

[0016] (1) In the present invention, the purified phosphogypsum is used as a raw material for slow - release fertilizers. Phosphogypsum is beneficial to reducing soil fluorine pollution while retaining elements such as phosphorus, calcium, and silicon, effectively improving the utilization rate of phosphogypsum and enhancing its efficacy in agricultural production.

[0017] (2) The present invention constructs a slow - release fertilizer with a three - layer structure including a "core layer - slow - release layer - coating layer". The raw materials such as modified silicon slag and thermally activated attapulgite contained in the core layer have gradient pores, thus constructing a double slow - release network of "gradient pores (mesopores of modified silicon slag)+nano - pipelines (attapulgite)", significantly reducing the burst release rate of the slow - release fertilizer and avoiding fertilizer waste.

[0018] (3) The phosphorus gypsum-based slow-release fertilizer of the present invention uses a scenario-responsive material as the coating, which can select or adapt the coating type according to the actual use scenario, thereby constructing a "gradient pore - bacteria-mineral synergy - scenario response" slow-release system, achieving precise nutrient release and precise matching with crop requirements, and developing multi-scenario adaptable formulations, effectively improving the utilization rate of phosphorus gypsum and further improving the slow-release performance of the slow-release fertilizer.

[0019] Additional aspects and advantages of the present invention will be given in part in the following description, will become apparent in part from the following description, or will be learned through the practice of the present invention. Detailed implementation manners

[0020] The embodiments of the present invention will be described in detail below. The embodiments described below are exemplary and are only used to explain the present invention and should not be construed as a limitation of the present invention.

[0021] It should be noted that the terms "first" and "second" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance or implicitly specifying the quantity of the indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of such features. Further, in the description of the present invention, unless otherwise specified, the meaning of "plurality" is two or more.

[0022] In the ranges disclosed herein, the endpoints and any values are not limited to the exact ranges or values, and these ranges or values should be understood to include values close to these ranges or values. For numerical ranges, between the endpoint values of each range, between the endpoint values of each range and individual point values, and between individual point values, they can be combined with each other to obtain one or more new numerical ranges, and these numerical ranges should be regarded as specifically disclosed herein.

[0023] In this document, the term "comprising" or "including" is an open expression, that is, it includes the content specified by the present invention, but does not exclude other aspects of the content.

[0024] In the first aspect of the embodiments of the present invention, the present invention provides a phosphorus gypsum-based slow-release fertilizer, comprising: a core layer, the core layer includes phosphorus gypsum and a composite bacterial agent; in the phosphorus gypsum, the fluoride content ≤ 0.1 wt%, and the phosphorus pentoxide content ≥ 0.1 wt%; the composite bacterial agent includes phosphorus-loving bacteria; a coating layer, the material of the coating layer includes a scenario-responsive material.

[0025] In the embodiments of the present invention, phosphogypsum is used as the main raw material of the slow-release fertilizer. The phosphogypsum of the present invention has been purified, so the fluoride content of the phosphogypsum is ≤0.1%, and the phosphorus pentoxide content is ≥0.1%. Its low fluoride content avoids soil fluoride pollution and at the same time has abundant phosphorus. In addition, the phosphogypsum also contains abundant calcium, sulfur, silicon and other elements, which can provide the necessary nutrient elements for the growth of crops. The phosphorus-loving bacteria in the composite bacterium agent play a role in decomposing the phosphorus element in the phosphogypsum. A large amount of insoluble phosphorus is contained in the phosphogypsum, and the phosphorus-loving bacteria convert the insoluble phosphorus into soluble phosphorus by secreting organic acids and phosphatases, thereby improving the utilization rate of phosphate fertilizer. Therefore, using phosphogypsum in the preparation of slow-release fertilizers can not only solve the comprehensive utilization problem of phosphogypsum, but also improve the soil, improve quality and efficiency, and improve the efficiency of phosphogypsum in agricultural production.

[0026] The phosphogypsum-based slow-release fertilizer of the embodiments of the present invention includes a core layer and a coating layer structure. Among them, the phosphogypsum and the composite bacterium agent contained in the core layer serve as the core nutrient sources of the slow-release fertilizer and provide fertilizers for crops; the coating layer material includes a scenario-responsive material, and this type of material can automatically adjust the nutrient release rate according to changes in environmental conditions (such as temperature, humidity, pH value, microbial activity, etc.), so as to achieve more precise nutrient supply and optimize the slow-release effect. Thus, the present invention effectively improves the utilization rate of phosphogypsum and optimizes the slow-release performance of the slow-release fertilizer.

[0027] In some embodiments of the present invention, in the phosphogypsum, the fluoride content is 0-0.1 wt%, and the phosphorus pentoxide content is 0.1-5 wt%; and / or, the scenario-responsive material includes any one of a moisture-responsive material, a temperature-responsive material, a pH-responsive material, a microbial degradation-responsive material, a photo-degradation-responsive material, a time-controlled material, a mechanical damage-responsive material, a temperature-sensitive-photo-sensitive dual-responsive material; and / or, the coating layer includes any one of a PLA-g-AA / humic acid composite film (polylactic acid grafted acrylic acid / humic acid composite film), a sulfur-polylactic acid double-layer film, an EVA-g-MAA film (ethylene-vinyl acetate copolymer grafted methacrylic acid film), a sulfur-polycaprolactone composite film, a PNIPAM-SrAl 2 O 4 :Eu 2+ / Dy 3+ / Dy composite film (poly-N-isopropylacrylamide-strontium aluminate: europium (II) ions / dysprosium (III) ions).

[0028] In the present invention, the phosphogypsum in the phosphogypsum-based slow-release fertilizer has a low fluorine content, avoiding soil fluorine pollution, and at the same time has a high phosphorus content, meeting the growth requirements of crops. The scene-responsive material of the coating layer can be selected or adapted according to actual usage requirements, so as to automatically adjust the nutrient release rate and obtain a slow-release fertilizer with excellent slow-release performance. Thus, the present invention effectively improves the utilization rate of phosphogypsum and further optimizes the slow-release performance of the slow-release fertilizer.

[0029] As an example, the water-responsive material includes at least one of polyvinyl alcohol and polyacrylamide.

[0030] As an example, the temperature-responsive material includes at least one of PLA-g-AA / humic acid composite film, polyethylene, and polypropylene.

[0031] As an example, the pH-responsive material includes at least one of polyacrylic acid materials and EVA-based pH-responsive membranes.

[0032] As an example, the microbially degradable material includes at least one of starch, cellulose, and biodegradable polymers.

[0033] As an example, the photo-degradable material includes at least one of photo-degradable plastics.

[0034] As an example, the time-controlled material includes at least one of sulfur-chitosan composite film, epoxy resin, and polyurethane.

[0035] As an example, the mechanically damaged-responsive material includes at least one of sulfur-polycaprolactone composite film, sulfur-polylactic acid bilayer film, brittle resin, or composite material.

[0036] As an example, the thermosensitive-photosensitive dual-responsive material includes PNIPAM-SrAl 2 O 4 :Eu 2+ / Dy 3+ composite film.

[0037] In some embodiments of the present invention, the composite bacterium agent includes phosphorus-loving bacteria and functional bacteria. The functional bacteria include at least one of silicate bacteria, salt-tolerant bacteria, potassium-dissolving bacteria, nitrogen-fixing bacteria, and sulfur-oxidizing bacteria; and / or, the composite bacterium agent further includes a magnetic nano-carrier, and the magnetic nano-carrier includes Fe 3 O 4 @SiO 2 .

[0038] The composite microbial agent in the embodiments of the present invention includes phosphorus-solubilizing bacteria and functional bacteria. The phosphorus-solubilizing bacteria have the ability to solubilize phosphorus, and can convert the insoluble phosphorus in phosphogypsum into soluble phosphorus by secreting organic acids and phosphatases, thereby improving the utilization rate of phosphate fertilizers. The functional bacteria can adapt to specific soil environments (such as acidic, alkaline or saline-alkali soils) or have a certain specific function (such as nitrogen-fixing bacteria). These strains can act synergistically with the phosphorus-solubilizing bacteria to further enhance the activity of the microbial community in the soil and promote the circulation and utilization of other nutrients in the soil. The magnetic nanocarrier Fe 3 O 4 @SiO 2 in the composite microbial agent not only has good dispersibility, can form a composite structure with the fertilizer coating material to enhance the controlled-release performance of the fertilizer, but also can supplement the iron element required by bacteria. Thus, the present invention effectively improves the utilization rate of phosphogypsum and optimizes the slow-release performance of the slow-release fertilizer.

[0039] In some embodiments of the present invention, the phosphogypsum-based slow-release fertilizer further includes a slow-release layer located between the core layer and the coating layer; the phosphogypsum-based slow-release fertilizer satisfies at least one of the following: (a) the slow-release layer includes at least one of zeolite and biochar; (b) the core layer further includes thermally activated attapulgite, modified silicon slag and humic acid organic fertilizer.

[0040] In the present invention, the slow-release fertilizer further includes a slow-release layer, which can control the release rate of nutrients, so that the nutrients in the fertilizer can be slowly and stably released according to the needs of crops, thereby improving the fertilizer utilization rate and reducing nutrient loss.

[0041] The thermally activated attapulgite and modified silicon slag contained in the core layer have a gradient pore structure and strong adsorption properties, and can effectively adsorb and fix nutrients in the fertilizer, such as nitrogen, phosphorus, potassium, etc., thereby controlling the release rate of nutrients to synchronize with the absorption needs of crops and improving the slow-release performance of the fertilizer and improving the soil structure. In addition, the modified silicon slag can also provide silicon elements to improve soil air permeability. The humic acid organic fertilizer further provides fertility for the slow-release fertilizer, and can not only improve the utilization rate and slow-release performance of the fertilizer during the production of the slow-release fertilizer, but also significantly improve the soil structure and crop growth environment.

[0042] The coating layer can be selected according to the actual use scenario or adapted to the corresponding materials of the scenario to automatically adjust the release rate of nutrients and obtain a slow-release fertilizer with excellent slow-release performance.

[0043] Thus, the phosphogypsum-based slow-release fertilizer of the present invention includes a three-layer structure of "core layer - slow-release layer - coating layer", constructing a "gradient pore - bacteria-mineral synergy - scenario response" slow-release system, realizing the precise release of nutrients and the precise matching with crop needs. Thereby effectively reducing the burst release rate and further improving the slow-release performance of the slow-release fertilizer.

[0044] In a second aspect of the present invention, a method for preparing a phosphorus gypsum-based slow-release fertilizer is proposed, comprising the following steps: inoculating a composite bacterial agent into phosphorus gypsum and performing fermentation treatment to obtain fermentation microspheres; forming a core layer with the fermentation microspheres and forming a coating layer outside the core layer to obtain a slow-release fertilizer precursor; and drying the slow-release fertilizer precursor to obtain the phosphorus gypsum-based slow-release fertilizer.

[0045] Thus, according to the method for preparing a phosphorus gypsum-based slow-release fertilizer of the present invention, a slow-release fertilizer with excellent slow-release performance can be prepared, thereby effectively improving the utilization rate of phosphorus gypsum and reducing the burst release rate of the slow-release fertilizer.

[0046] In some embodiments of the present invention, the preparation method further comprises: forming a slow-release layer between the core layer and the coating layer; the slow-release layer comprises at least one of zeolite and biochar; and / or, in the step of inoculating the composite bacterial agent into the phosphorus gypsum, it further comprises: adding heat-activated attapulgite, modified silicon slag and humic acid organic fertilizer, and mixing to obtain a mixture.

[0047] According to the preparation method provided by the embodiments of the present invention, a slow-release fertilizer with a three-layer structure of "core layer - slow-release layer - coating layer" can be prepared, and a slow-release system of "gradient pore channels - bacteria-mineral synergy - scenario response" is constructed, so as to realize the precise matching of nutrient release and crop requirements, be applicable to multiple scenarios, and effectively improve the utilization rate of phosphorus gypsum.

[0048] In some embodiments of the present invention, the preparation method satisfies at least one of the following: (1) the mass ratio of phosphorus gypsum, attapulgite, modified silicon slag and humic acid organic fertilizer is (40-90):(5-30):(5-20):(10-30); (2) the attapulgite is calcined at 450-550 °C; (3) the specific surface area of the modified silicon slag ≥ 250 m 2 / g, the first pore diameter is 2-5 nm, and the second pore diameter is 20-50 nm; (4) the D50 particle size of the core layer is 0.5-2 mm.

[0049] When the preparation method of the phosphorus gypsum-based slow-release fertilizer provided by the embodiments of the present invention satisfies the above conditions at the same time, it is beneficial to prepare a phosphorus gypsum-based slow-release fertilizer with excellent performance. Among them, the modified silicon slag has both a relatively large second pore diameter and a relatively small first pore diameter. This gradient pore channel structure can achieve fine control of the nutrient release rate, improve the slow-release efficiency of the fertilizer, and at the same time cooperate with the scenario-responsive material of the coating layer. Thus, the core layer structure of the phosphorus gypsum-based slow-release fertilizer of the present invention has a double slow-release network of "gradient pore channels (modified silicon slag) + nano-pore channels (attapulgite)", further controlling the precise matching of nutrient release and crop requirements, being applicable to multiple scenarios, effectively improving the utilization rate of phosphorus gypsum, and optimizing the slow-release performance of the slow-release fertilizer.

[0050] As an example, the D50 particle size is 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, 2 mm, etc.

[0051] In some embodiments of the present invention, the preparation method of the modified silicon slag includes: (1) subjecting fly ash to gradient acid leaching, and the gradient acid leaching includes: first performing treatment with sulfuric acid at 0.4 - 0.6 mol / L, and then performing treatment with oxalic acid at 0.1 - 0.3 mol / L, with a solid-liquid ratio of 1:(4 - 6); (2) then performing microwave puffing treatment at 700 - 900 W for 2 - 5 min to form the modified silicon slag with a bimodal pore size distribution.

[0052] In some embodiments of the present invention, the composite bacterial agent includes phosphorus-loving bacteria and functional bacteria; the composite bacterial agent satisfies at least one of the following: (A) the mass ratio of phosphorus-loving bacteria to functional bacteria is 1:(1 - 3); (B) the addition amount of the composite bacterial agent is 5 - 10% of the mass of the mixture; (D) the cell concentration of the composite bacterial agent ≥ 1×10 9 CFU / g; (E) the composite bacterial agent further includes 0.5 - 2 wt% magnetic nanocarriers.

[0053] When the preparation method of the phosphogypsum-based slow-release fertilizer provided by the embodiments of the present invention simultaneously satisfies the above conditions, the composite bacterial agent will have excellent microbial properties, which can not only improve the nutrient utilization rate and crop yield, but also improve the soil structure and enhance the stress resistance of crops. Thus, the slow-release performance of the slow-release fertilizer will be further optimized.

[0054] As an example, the mass ratio of phosphorus-loving bacteria to functional bacteria is 1:1, 1:1.5, 1:2, 1:2.5, 1:3, etc.

[0055] As an example, the addition amount of the composite bacterial agent is 5%, 6%, 7%, 8%, 9%, 10% of the mass of the mixture, etc.

[0056] As an example, the magnetic nanocarrier in the composite bacterial agent is 0.5 wt%, 0.7 wt%, 0.9 wt%, 1.0 wt%, 1.2 wt%, 1.4 wt%, 1.6 wt%, 1.8 wt%, 2 wt%, etc.

[0057] In some specific embodiments of the present invention, the magnetic nanocarrier includes Fe 3 O 4 @SiO 2 .

[0058] Thus, the magnetic nanocarrier Fe 3 O 4 @SiO 2, not only has good dispersibility, can form a composite structure with the fertilizer coating material to enhance the controlled-release performance of the fertilizer, but also can supplement the iron element required by bacteria.

[0059] In some embodiments of the present invention, the coating layer includes any one of PLA-g-AA / humic acid composite film, sulfur-polylactic acid double-layer film, EVA-g-MAA film, sulfur-polycaprolactone composite film, PNIPAM-SrAl 2 O 4 :Eu 2+ / Dy 3+ composite film. Thus, the slow-release performance of the slow-release fertilizer can be further improved.

[0060] In some embodiments of the present invention, the conditions for fermentation treatment include: performing the first fermentation at 35-38 °C for 20-24 h, performing the second fermentation at 25-28 °C for 45-50 h, applying ultrasonic waves at 35-45 kHz every 4-6 h, and the power density of the ultrasonic waves is 0.3-0.7 W / cm 2 .

[0061] The fermentation treatment conditions provided by the embodiments of the present invention, firstly, the fermentation in two stages can promote the growth of microorganisms, and at the same time help to activate various enzymes in the microorganisms, which is beneficial to the decomposition and transformation of organic matter by the bacteria; secondly, the ultrasonic waves with a power density of 0.3-0.7 W / cm2 can break the aggregates in the fermentation broth, make the microorganisms and the substrate fully mixed, and will not cause excessive damage to the microbial cells, thereby shortening the fermentation cycle, reducing the production cost, and improving the production efficiency. Thus, the utilization rate of phosphogypsum will be further improved, and the slow-release performance of the slow-release fertilizer will be optimized.

[0062] In some embodiments of the present invention, the fermentation treatment is carried out in a dynamic fermentation system, and the dynamic fermentation system includes an on-line near-infrared spectrometer, an automatic turning device, and an ultrasonic module. The on-line near-infrared spectrometer is mainly used to monitor the decomposition degree of organic matter in real time (accuracy ±2%), the automatic turning device is triggered when the oxygen concentration <5%, and the frequency of the ultrasonic module is adjustable from 20 to 60 kHz.

[0063] In some embodiments of the present invention, unless otherwise specified, the phosphogypsum is prepared with reference to the patent CN118206147A.

[0064] The solutions of the present invention will be explained below with reference to the embodiments. Those skilled in the art will understand that the following embodiments are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. For those without specific technical or conditions noted in the embodiments, the techniques or conditions described in the literature in the art or according to the product specifications are followed. For the reagents or instruments without indicating the manufacturer, they are all conventional products that can be obtained through commercial purchase.

[0065] Example 1: Preparation of special fertilizer for strawberry

[0066] (1) Raw material mixing: 60 kg of phosphogypsum (F content ≤ 0.10%, P 2 O 5 content of 0.28%), 18kg thermally activated attapulgite (calcined at 550℃, with a specific surface area of ​​380m 2 / g), 12kg modified silicon slag (pore volume is 0.68cm 3 / g), 15kg humic acid organic fertilizer (HA≥45%) and mix thoroughly.

[0067] (2) Bacterial agent compounding: 7.5 kg of compound bacterial agent (the mass ratio of phosphatophilic bacteria to silicate bacteria was 1:2, and the number of viable bacteria was 3×10 9 CFU / g), and then add 0.15kg Fe 3 O 4 @SiO 2 Nanocarriers.

[0068] (3) Fermentation treatment: The mixture was fermented at 38 °C for 24 h, then cooled to 28 °C for secondary fermentation for 48 h, during which 40 kHz ultrasound (0.5 W / cm 2 ) to obtain fermentation microspheres.

[0069] (4) Granulation and coating: The fermentation microspheres (particle size D50 = 0.8 mm) formed the core layer, zeolite and biochar formed the sustained release layer, and PLA-g-AA / humic acid film (thickness 65 μm, Tg = 32° C.) formed the coating layer.

[0070] (5) Drying treatment: Infrared-microwave coupled drying method was used, the drying temperature was 55°C, and the drying time was 1.5 h. A temperature-sensitive phosphogypsum-based slow-release fertilizer was obtained.

[0071] The phosphogypsum-based slow-release fertilizer of the present invention and conventional fertilizer (control) were used to fertilize strawberries in the growing period, and the growth conditions of the strawberries were compared.

[0072] Test results: The strawberry-specific fertilizer of this embodiment accurately controls the calcium release window period through the 32°C phase change membrane, so that the calcium supply during the fruit expansion period reaches 0.35 mg / grain / day, which is 2.1 times higher than that of conventional fertilizers, and effectively reduces the rate of deformed fruit to 3.2% (the control is 18.6%). It can be seen from the test results that the coating material (PLA-g-AA / humic acid film) of the strawberry-specific fertilizer of this embodiment has a temperature-sensitive property. When the ambient temperature is about 32°C, the release of calcium is accurately controlled. At the same time, phosphogypsum also provides strawberries with sufficient magnesium, phosphorus, silicon and other elements, which not only effectively improves the utilization rate of phosphogypsum, but also can be a slow-release fertilizer, accurately control the calcium release window period, and promote strawberry growth. The test data is shown in Table 1.

[0073] Table 1 Comparison of the effects of phosphogypsum-based slow-release fertilizer for strawberries and conventional fertilizers (control) in Example 1

[0074] Index The present invention Control Phosphorus utilization rate (%) 58.3 36.7 Fruit Vc content (mg / 100g) 82.6 65.4 Soil fluoride increment (ppm) 0.8 5.2 Fruit deformity rate (%) 3.2 18.6

[0075] Example 2: Preparation of saline-alkali land improvement fertilizer

[0076] (1) Raw material mixing: 60 kg of phosphogypsum (F content ≤ 0.10%, P 2 O 5 content of 0.28%), 18kg thermally activated attapulgite (calcined at 550℃, with a specific surface area of ​​380m 2 / g), 12kg modified silicon slag (pore volume is 0.68cm 3 / g), 15kg humic acid organic fertilizer (HA≥45%), and 0.5kg 5% biochar-based ion exchanger (CEC 220cmol / kg) were fully mixed.

[0077] (2) Bacterial agent compounding: 7.5 kg of compound bacterial agent was inoculated into the mixed raw materials, wherein the mass ratio of phosphophilic bacteria to halophilic bacteria (Halomonas venusta) was 1:3, and the number of viable bacteria was 3×10 9 CFU / g), and then add 0.15kg Fe 3 O 4 @SiO 2 Nanocarriers.

[0078] (3) Fermentation treatment: The mixture was fermented at 38°C for 24 h, then cooled to 28°C for secondary fermentation for 48 h, during which 40 kHz ultrasound (0.5 W / cm 2 ) to obtain fermentation microspheres.

[0079] (4) Granulation and coating: The fermentation microspheres (particle size D50 = 0.8 mm) formed the core layer, the zeolite and biochar formed the slow-release layer, and the EVA-g-MAA film layer formed the coating layer.

[0080] (5) Drying treatment: Infrared-microwave coupling drying method is adopted, the drying temperature is 55 °C, and the drying time is 1.5 h. The phosphogypsum-based slow-release fertilizer is obtained.

[0081] The phosphogypsum-based slow-release fertilizer of the present invention and a conventional fertilizer (control) are used to fertilize and improve saline-alkali land planted with alfalfa, and the changes in the soil and alfalfa are recorded.

[0082] Test results: The saline-alkali land improvement fertilizer of this example triggers the expansion of membrane pores (swelling rate ≥ 300%) when the pH > 8.5 through the EVA-g-MAA film layer of the coating material, and releases Ca 2+ 28 mg / kg of soil per day, combined with the Na + efflux effect of salt-tolerant bacteria (Halomonas venusta) (survival rate 87.5%), so that the sodium adsorption ratio (SAR) of the soil in the first season of alfalfa planting is reduced from 18.2 to 6.8 (a decrease of 63%), the soil structure is improved, the emergence rate is increased to 82.5% (control 37.4%), and the calcium utilization rate reaches 45.3% (control 12.1%). Moreover, when the EC of the soil > 5 mS / cm, the slow-release rate of the slow-release fertilizer is automatically down-regulated, which can avoid nutrient waste, reduce salt stress, improve soil health, extend fertilizer efficiency and adapt to extreme conditions. The test data are shown in Table 2.

[0083] Table 2 Comparison of the effects of the saline-alkali land improvement phosphogypsum-based slow-release fertilizer and the conventional fertilizer (control) in Example 2

[0084] Index The present invention Control Soil SAR 6.8 18.2 Alfalfa yield (kg / ha) 4850 1620 Emergence rate (%) 82.5 37.4 Phosphogypsum utilization rate (%) 85.3 35.1 Calcium utilization rate (%) 45.3 12.1

[0085] Example 3: Preparation of special fertilizer for rice

[0086] (1) Raw material mixing: 65 kg of phosphogypsum (F content ≤ 0.10%, P 2 O 5 content is 0.28%), 20 kg of thermally activated attapulgite (calcined at 600 °C, specific surface area is 420 m 2 / g), 15 kg of modified silicon slag (loaded with nano-SiO 2 ), and 20 kg of humic acid organic fertilizer (containing ammonium lignosulfonate) are fully mixed.

[0087] (2) Bacterial agent compounding: 6 kg of compound bacterial agent is inoculated into the mixed raw materials, in which the mass ratio of phosphate-solubilizing bacteria to silicate bacteria (Bacillus mucilaginosus CICC 10325) is 1:1, and the total viable count is 2.8×10 9 CFU / g, and then 0.03 kg of Fe 3 O 4 @SiO 2 nano-carrier is added.

[0088] (3) Fermentation treatment: The mixture raw materials are subjected to proliferation fermentation at 35°C for 24 h, and then cooled to 25°C for secondary fermentation for 48 h. During this period, 40 kHz ultrasonic waves (0.5 W / cm 2 ) are applied every 4 h to obtain fermented microspheres.

[0089] (4) Granulation and coating: The fermented microspheres (particle size D50 = 0.5 mm) form the core layer, zeolite (ZSM-5 type) and rice husk biochar (specific surface area 380 m 2 / g) are compounded at a mass ratio of 3:1 to form a slow-release layer, and a sulfur-polylactic acid double-layer film (outer hydrophobic angle 108°) forms the coating layer.

[0090] (5) Drying treatment: Surface treatment is carried out with a hydrophobic modifier and then drum drying. The drying temperature is 75°C and the drying time is 2.5 h. A phosphorus gypsum-based slow-release fertilizer is obtained.

[0091] The phosphorus gypsum-based slow-release fertilizer for rice of the present invention and a conventional fertilizer (control) are used to fertilize rice during the growth period, and the growth conditions of the rice are compared.

[0092] Test results: The special fertilizer for rice in this example, through the synergistic effect of the gradient slow-release silicon technology and the sulfur-polylactic acid double-layer film (contact angle 108°) of the coating layer, the release rate of silicon element is synchronized with the tillering period of rice (release peak at 30 - 45 days, 0.25 mg / granule·day), so that the silicon deposition amount at the base of the rice stem reaches 12.3 mg / cm 2 (control 5.8 mg / cm2), achieving the effect of anti-lodging. And the sulfur-polylactic acid double-layer film is used for coating, which has a hydrophobic effect, and the hydrophobic film layer extends the slow-release period in the paddy field environment by 40%. In addition, the flexural strength of the rice is increased by 41%, the lodging rate is reduced from 19.3% (control) to 5.1%, and the selenium content of the rice is increased to 0.16 mg / kg (control 0.08 mg / kg), meeting the standard of selenium-rich rice (GB / T 22499-2008). The test data are shown in Table 3.

[0093] Table 3 Comparison of the effects of the special phosphorus gypsum-based slow-release fertilizer for rice and the conventional fertilizer (control) in Example 3

[0094] Index The present invention Control Tiller number (per plant) 18.2±1.5 12.7±1.2 Lodging rate (%) 5.1 19.3 <![CDATA[Silicon deposition amount in plants (mg / cm 2 )]]> 12.3 5.8 Rice selenium content (mg / kg) 0.16±0.02 0.08±0.01

[0095] Example 4: Preparation of special fertilizer for wheat

[0096] (1) Raw material mixing: 50 kg of phosphorus gypsum (F content ≤ 0.10%, P 2 O 5 content is 0.28%), 25 kg of heat-activated attapulgite (loaded with nitrate reductase), 10 kg of modified silicon slag (pore volume is 0.7 cm 3(g), and mix thoroughly with 15 kg of humic acid organic fertilizer (containing nitrification inhibitor DCD).

[0097] (2) Bacterial agent compounding: Inoculate 10 kg of compound bacterial agent into the mixed raw materials, where the mass ratio of phosphorus-loving bacteria to nitrogen-fixing bacteria (Azotobacter chroococcum CGMCC 1.176) is 1:3, and the viable bacteria count is 3×10 9 CFU / g), and then add 0.15 kg of Fe 3 O 4 @SiO 2 nano-carrier.

[0098] (3) Fermentation treatment: The mixture of raw materials is subjected to proliferation fermentation at 38°C for 24 h, and then cooled to 28°C for secondary fermentation for 48 h. During this period, 40 kHz ultrasonic waves (0.5 W / cm 2 ) are applied every 4 h to obtain fermented microspheres.

[0099] (4) Granulation and coating: The fermented microspheres (particle size D50 = 2 mm) form the core layer, and zeolite, biochar, and nano-hydroxyapatite for nitrogen control (NH 4 + adsorption capacity ≥ 120 mg / g) form the slow-release layer, and the temperature-sensitive and photosensitive dual-responsive membrane of PNIPAM-SrAl 2 O 4 :Eu 2+ / Dy 3+ forms the coating layer (light transmittance > 80% at 25°C, light transmittance < 20% above 30°C).

[0100] (5) Drying treatment: Adopt the infrared-microwave coupling drying method, the drying temperature is 55°C, and the drying time is 1.5 h. Obtain the phosphorus gypsum-based slow-release fertilizer.

[0101] Use the wheat-specific phosphorus gypsum-based slow-release fertilizer of the present invention and a commercially available controlled-release fertilizer (control) to fertilize wheat in the growth period, and compare the growth conditions of wheat.

[0102] Test results: The wheat-specific fertilizer in this example has the effect of controlling nitrogen and preventing excessive vegetative growth in wheat. In this example, the nitrogen control layer of nano-hydroxyapatite (NH 4 + adsorption capacity ≥ 120 mg / g) and the temperature-sensitive and photosensitive dual-responsive membrane (light transmittance < 20% above 30°C) act synergistically to accurately control the nitrogen release amount at the jointing stage to 1.0 ± 0.2 mg / granule·day. The photosensitive membrane inhibits ineffective tillering in the later growth stage of wheat. The ineffective tillering is reduced by 58%, the 1000-grain weight reaches 45.3 g (38.7 g for the control), the protein content is increased to 13.8% (11.2% for the control), and the nitrogen fertilizer utilization rate is increased to 61.5% (42.3% for the control). The test data are shown in Table 4.

[0103] Table 4 Comparison of the effects of phosphogypsum-based slow-release fertilizer for wheat and conventional fertilizer (control) in Example 3

[0104] Index The present invention Control 1000-grain weight (g) 45.3±1.2 38.7±1.5 Protein content (%) 13.8 11.2 Nitrogen fertilizer utilization rate (%) 61.5 42.3

[0105] Example 5: Fertilizer for corn

[0106] (1) Raw material mixing: 70 kg of phosphogypsum (F content ≤ 0.10%, P 2 O 5 The content is 0.28%), 18kg of heat-activated attapulgite (loaded with nano ZnO), 12kg of modified silicon slag (pore size 5-50nm), and 15kg of humic acid organic fertilizer (containing γ-aminobutyric acid) are fully mixed.

[0107] (2) Bacterial agent compounding: 9.2 kg of compound bacterial agent was inoculated into the mixed raw materials, wherein the mass ratio of phosphophilic bacteria: silicate bacteria: potassium-dissolving bacteria was 1:1:1, and the number of viable bacteria was 3×10 9 CFU / g), and then add 0.18kg Fe 3 O 4 @SiO 2 Nanocarriers.

[0108] (3) Fermentation treatment: The mixture was fermented at 38°C for 24 h, then cooled to 28°C for secondary fermentation for 48 h, during which 40 kHz ultrasound (0.5 W / cm 2 ) to obtain fermentation microspheres.

[0109] (4) Granulation and coating: Fermentation microspheres (particle size D50 = 1.5 mm) are formed into a core layer, zeolite, biochar and potassium feldspar powder (K 2 O≥8%) forms a sustained-release layer, and a sulfur-polycaprolactone composite film (compressive strength ≥50N / particle) forms a coating layer.

[0110] (5) Drying treatment: Infrared-microwave coupling drying method was used, the drying temperature was 55° C., and the drying time was 1.5 h. The phosphogypsum-based slow-release fertilizer was obtained.

[0111] The phosphogypsum-based slow-release fertilizer for corn of the present invention and a commercially available controlled-release fertilizer (control) were used to fertilize corn in the growing period, and the growth conditions of the corn were compared.

[0112] Test results: For the special maize fertilizer in this example, potassium element is added to the slow-release layer, and it can work synergistically through the silicon-potassium co-slow-release technology (silicon release rate: 0.18 mg / granule·day, potassium release rate: 0.22 mg / granule·day) and the sulfur-polycaprolactone high-strength coating (compressive strength ≥ 50 N / granule). The silicon-potassium co-slow-release makes the maize stem diameter reach 2.85 cm (control: 2.12 cm), the flexural strength increase by 35%, and the grain yield increase to 11,250 kg / ha (control: 8,650 kg / ha). Moreover, due to its high compressive strength, the sulfur-polycaprolactone high-strength coating can avoid the premature rupture and fertilizer release caused by the extrusion of fertilizer granules due to the well-developed maize roots, thus exhibiting good slow-release performance. The γ-aminobutyric acid contained in the humic acid organic fertilizer further enhances the drought stress resistance, and the relative leaf water content is maintained at 78.5% under drought stress (control: 61.2%). The test data are shown in Table 5.

[0113] Table 5 Comparison of the effects of the special phosphorus gypsum-based slow-release fertilizer for maize and conventional fertilizer (control) in Example 5

[0114] Index The present invention Control Stem diameter (cm) 2.85±0.2 2.12±0.3 Grain yield (kg / ha) 11250 8650 Lodging rate (%) 3.8 17.6

[0115] Example 6: Preparation of special garlic fertilizer

[0116] (1) Raw material mixing: Thoroughly mix 55 kg of phosphorus gypsum (S ≥ 18%), 20 kg of heat-activated attapulgite (loaded with Thiobacillus), 15 kg of modified silicon slag (containing 0.5% wt sodium selenate), and 20 kg of humic acid organic fertilizer (added with alliin precursor).

[0117] (2) Bacterial agent compounding: Inoculate 5.5 kg of compound bacterial agent into the mixed raw materials, where the mass ratio of phosphorus-philic bacteria to sulfur-oxidizing bacteria (Thiobacillus thioparus CICC 10380) is 1:1, and the viable bacteria count is 3×10 9 CFU / g), and then add 0.11 kg of Fe 3 O 4 @SiO 2 nano-carrier.

[0118] (3) Fermentation treatment: The mixture of raw materials is subjected to proliferation fermentation at 38°C for 24 h, and then cooled to 28°C for secondary fermentation for 48 h. During this period, 40 kHz ultrasonic waves (0.5 W / cm 2 ) are applied every 4 h to obtain fermented microspheres.

[0119] (4) Granulation and coating: The fermented microspheres (particle size D50 = 0.8 mm) form the core layer, zeolite, biochar, and nano-sulfur powder (particle size 200 nm) form the slow-release layer, and the sulfur-chitosan composite film forms the coating layer.

[0120] (5) Drying treatment: The infrared-microwave coupling drying method is adopted, the drying temperature is 55 °C, and the drying time is 1.5 h. The phosphogypsum-based slow-release fertilizer is obtained.

[0121] The garlic-specific phosphogypsum-based slow-release fertilizer of the present invention and a commercially available controlled-release fertilizer (control) are used to fertilize garlic during the growth period, and the growth conditions of garlic are compared.

[0122] Test results: The garlic-specific fertilizer in this example uses the synergistic effect of sulfur-chitosan composite film and nano-selenium technology. When the sulfur-chitosan composite film is used as the coating, its slow-release period is synchronized with the bulb swelling period of garlic, enabling the targeted release of sulfur elements. During the bulb swelling period of garlic, the release proportion of sulfur elements reaches 75%, the bulb diameter reaches 6.5 cm (control 5.2 cm), the activity of alliin synthase is increased by 2.1 times, the allicin content is increased to 4.8 mg / g (control 3.1 mg / g), the soil sulfur residue is reduced to 12.3 ppm (control 35.6 ppm), and the selenium biofortification efficiency reaches 82.4% (meeting the selenium-rich food standard of GB 1903.28-2018). The test data are shown in Table 6.

[0123] Table 6 Comparison of the effects of the garlic-specific phosphogypsum-based slow-release fertilizer and the conventional fertilizer (control) in Example 6

[0124] Index The present invention Control Garlic bulb diameter (cm) 6.5±0.3 5.2±0.4 Allicin content (mg / g) 4.8±0.2 3.1±0.3 Soil sulfur residue (ppm) 12.3 35.6

[0125] As can be seen from the above examples, the present invention constructs a "gradient pore-microbe-mineral synergy-scenario response" slow-release system by deeply purifying phosphogypsum and compounding it with various functional materials, realizing the precise release of nutrients and the precise matching with the needs of crops. At the same time, the present invention develops multi-scenario adaptation formulas, effectively improving the utilization rate of phosphogypsum, and providing new ideas for the resource utilization of phosphogypsum and the development of slow and controlled release fertilizer technologies.

[0126] In the description of this specification, the description referring to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples. In addition, without conflict, those skilled in the art can combine and combine the different embodiments or examples described in this specification and the features of different embodiments or examples.

[0127] Although the embodiments of the present invention have been shown and described above, it can be understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those of ordinary skill in the art can make changes, modifications, substitutions, and variations to the above embodiments within the scope of the present invention.

Claims

1. A phosphogypsum-based slow-release fertilizer, characterized in that: include: A core layer, the core layer comprising phosphogypsum and a composite bacterial agent; in the phosphogypsum, a fluoride content of ≤0.1wt%, and a phosphorus pentoxide content of ≥0.1wt%; and the composite bacterial agent comprising phosphatophilic bacteria; The envelope layer comprises a scene responsive material.

2. The phosphogypsum-based slow-release fertilizer according to claim 1, characterized in that: The phosphogypsum has a fluoride content of 0-0.1 wt% and a phosphorus pentoxide content of 0.1-5 wt%; And / or, the scene responsive material includes any one of a moisture responsive material, a temperature responsive material, a pH responsive material, a microbial degradable material, a photodegradable material, a time-controlled material, a mechanical damage responsive material, and a temperature-sensitive-photosensitive dual-responsive material; And / or, the coating layer includes PLA-g-AA / humic acid composite film, sulfur-polylactic acid double-layer film, EVA-g-MAA film, sulfur-polycaprolactone composite film, PNIPAM-SrAl2O4:Eu 2+ / Dy 3+ Any of the composite membranes.

3. The phosphogypsum-based slow-release fertilizer according to claim 2, characterized in that: The composite bacterial agent also includes functional bacteria, and the functional bacteria include at least one of silicate bacteria, salt-tolerant bacteria, potassium-dissolving bacteria, nitrogen-fixing bacteria, and sulfur-oxidizing bacteria; And / or, the composite bacterial agent further comprises a magnetic nanocarrier, and the magnetic nanocarrier comprises Fe3O4@SiO2.

4. The phosphogypsum-based slow-release fertilizer according to any one of claims 1 to 3, characterized in that: The phosphogypsum-based slow-release fertilizer further includes a slow-release layer, and the slow-release layer is located between the core layer and the coating layer; the phosphogypsum-based slow-release fertilizer satisfies at least one of the following: (a) the sustained-release layer comprises at least one of zeolite and biochar; (b) The core layer further comprises heat-activated attapulgite, modified silicon slag and humic acid organic fertilizer.

5. The method for preparing the phosphogypsum-based slow-release fertilizer according to any one of claims 1 to 4, characterized in that: The following steps are involved: Inoculating composite bacterial agents into phosphogypsum for fermentation to obtain fermentation microspheres; The fermented microspheres are formed into a core layer, and a coating layer is formed outside the core layer to obtain a slow-release fertilizer precursor; The slow-release fertilizer precursor is dried to obtain the phosphogypsum-based slow-release fertilizer.

6. The preparation method according to claim 5, characterized in that: Also includes: forming a sustained-release layer between the core layer and the coating layer; The sustained-release layer includes at least one of zeolite and biochar; And / or, the step of inoculating the composite bacterial agent into the phosphogypsum further includes: adding attapulgite, modified silicon slag, and humic acid organic fertilizer, and mixing to obtain a mixture.

7. The preparation method according to claim 6, characterized in that: The preparation method satisfies at least one of the following: (1) The mass ratio of the phosphogypsum, heat-activated attapulgite, modified silicon slag, and humic acid organic fertilizer is (40-90): (5-30): (5-20): (10-30); (2) The thermally activated attapulgite is calcined at 450-550° C.; (3) The specific surface area of ​​the modified silicon slag is ≥250m 2 / g, the first pore size is 2-5nm, and the second pore size is 20-50nm; (4) The D50 particle size of the core layer is 0.5 to 2 mm.

8. The preparation method according to claim 6, characterized in that: The composite bacterial agent includes phosphophilic bacteria and functional bacteria; the composite bacterial agent satisfies at least one of the following: (A) the mass ratio of the phosphophilic bacteria to the functional bacteria is 1:(1-3); (B) The amount of the composite bacterial agent added is 5 to 10% of the mass of the mixture; (D) The bacterial concentration of the composite bacterial agent is ≥ 1×10 9 CFU / g; (E) The composite bacterial agent also includes 0.5-2 wt% of magnetic nanocarriers.

9. The preparation method according to any one of claims 5 to 8, characterized in that: The fermentation treatment conditions include: performing the first fermentation at 35-38°C for 20-24 hours, performing the second fermentation at 25-28°C for 45-50 hours, applying 35-45kHz ultrasonic waves every 4-6 hours, and the power density of the ultrasonic waves is 0.3-0.7W / cm 2 .

10. The preparation method according to any one of claims 5 to 9, characterized in that: The coating layer includes PLA-g-AA / humic acid composite film, sulfur-polylactic acid double-layer film, EVA-g-MAA film, sulfur-polycaprolactone composite film, PNIPAM-SrAl2O4:Eu 2+ / Dy 3+ Any of the composite membranes.