Nutritional moisturizing ceramsite as well as preparation method, application and application method thereof

Abstract

The invention provides nutritional moisturizing ceramsite as well as a preparation method, application and an application method.The method comprises the following steps: firstly, uniformly mixing sieved power plant fly ash with commercial cement, solid nutrition powder and coal gangue powder, and adding hydrogen peroxide to obtain porous ceramsite; the preparation method comprises the following steps: adsorbing a nutritional agent by porous ceramsite, wrapping the porous ceramsite with phosphorylated chitosan, carrying out hydroformylation and alkynylation, and reacting with the modified microcapsule to obtain the nutritional moisturizing ceramsite. The invention also provides an application of the nutritional moisturizing ceramsite in desertification soil improvement. According to the application method of the nutritional moisturizing ceramsite in desertification soil improvement, the nutritional moisturizing ceramsite is divided into large, medium and small ceramsite according to the particle size, and directly covers a desertification land to form a nutritional moisturizing ceramsite layer in a big-end-up form, a uniform form, an interlayer form, a mixed form or a uniform mixing form. The nutritional moisturizing ceramsite prepared by the invention can improve soil fertility and promote plant growth.

Description

Technical Field

[0001] The present invention belongs to the technical field of ceramsite preparation, and particularly relates to a nutrient and moisture-retaining ceramsite, a preparation method thereof, an application and an application method. Background Art

[0002] As a major country in power production and consumption, the discharge and utilization of fly ash from power plants in China have always been a highly concerned issue. In recent years, with the gradual standardization and institutionalization of national air governance, significant progress has been made in dust removal, desulfurization, and denitrification technologies in thermal power plants, which has also led to a year-on-year increase in fly ash production. Although the comprehensive utilization rate of fly ash in China has reached a relatively high level, there is still room for improvement. With the acceleration of industrialization and the increase in energy consumption, the output of fly ash will continue to grow. Therefore, strengthening the research on the comprehensive utilization of fly ash, promoting advanced technologies and experiences, and improving the added value and market competitiveness of fly ash are of great significance for promoting the development of circular economy and reducing environmental pollution.

[0003] In addition, China attaches great importance to the problem of desertification and has taken a series of effective measures to address it. By implementing major ecological projects such as the construction of the "Three-North" Shelter Forest System and the comprehensive management of desertification, the expansion of sandy land has been reduced. However, we are also clearly aware that desertification control remains a long-term and arduous task. Therefore, we need to actively research and develop advanced desertification control technologies and models to further improve the ecological environment and drive the economic development of desertified areas.

[0004] Currently, there are still many difficulties in the comprehensive utilization of fly ash from power plants and the improvement of desertified soil in China, which are as follows: The difficulties in the utilization of power plant fly ash are mainly reflected in the following aspects: (1) Large amount of fly ash generated and great treatment pressure: With the rapid development of the power industry, the amount of fly ash generated by coal-fired power plants has increased sharply. If a large amount of fly ash cannot be effectively treated, it will bring huge pressure to the environment, including occupying land resources, polluting water bodies and the atmosphere, etc. Therefore, how to efficiently and economically treat and utilize fly ash has become an urgent problem to be solved. (2) Contradiction between market demand and supply: There is an obvious contradiction between the market demand and supply of fly ash. Especially in winter, in the northern regions during the heating season, the unit load rate of thermal power plants is relatively high, and the fly ash emissions reach the highest value in a year. However, at this time, most building material factories, commercial concrete mixing stations, etc. are basically shut down, and the market demand is the lowest, resulting in an imbalance between the supply and demand of fly ash. This seasonal impact makes the utilization of fly ash more difficult. (3) Uneven regional utilization: There are also problems of uneven regional utilization of fly ash. In some regions, due to the large number of thermal power plants and the large output of fly ash, while the local market demand is limited, the utilization rate of fly ash is relatively low. On the contrary, in some regions, although the number of thermal power plants is small, the market demand is strong, and the utilization rate of fly ash is relatively high. This problem of uneven regional utilization increases the difficulty of cross-regional transportation and treatment of fly ash. (4) Single comprehensive utilization method of fly ash: At present, the comprehensive utilization method of fly ash is relatively single and mainly concentrated in the building materials industry. Although fly ash can be used to prepare building materials products such as commercial cement and concrete, this method has limited demand for fly ash and there are technical bottlenecks and cost problems. Therefore, more comprehensive utilization methods of fly ash need to be explored. (5) Technology and process need to be further improved: The comprehensive utilization technology and process of fly ash still need to be further improved and optimized. At present, some advanced comprehensive utilization technologies of fly ash are still in the research and development stage and have not been industrialized. At the same time, there are still some problems in the actual application of existing technologies and processes, such as low efficiency and high cost, which need to be further improved and perfected.

[0005] The difficulties in desertified soil improvement are mainly reflected in the following aspects: (1) Drought and less rainfall: In desertified areas, the precipitation is usually extremely low, the soil is extremely dry, and there is a lack of water required for plant growth. Such an extremely arid environment makes it extremely difficult to improve the soil and restore vegetation. (2) Sand and wind erosion: In desertified areas, sand and wind activities are frequent, with strong winds and long durations. Sand and wind not only cause soil erosion but also bury the vegetation under the photovoltaic panels, affecting the growth and survival rate of the vegetation. (3) Poor soil quality: Desertified land usually has poor soil quality, low organic matter content, and lack of nutrients, which is not conducive to plant growth. (4) High cost: The cost of desertified soil improvement is usually high. Large amounts of capital investment are required in all aspects, including land leveling, soil improvement, vegetation planting, and irrigation system construction. In addition, due to the vast area of desertified land and the large amount of improvement work, the cost is also increased. (5) Sustainable development: Desertified soil improvement needs to achieve sustainable development. This requires that the improvement measures should not only be able to improve the land quality in the short term but also be able to maintain soil fertility and vegetation cover in the long term to prevent the recurrence of desertification problems.

[0006] In summary, the utilization of power plant fly ash faces many difficulties and challenges. In order to promote the comprehensive utilization and sustainable development of fly ash, it is urgent to develop a method that can utilize fly ash on a large scale, efficiently, and with high value in combination with the current social development. At the same time, the difficulties in desertified soil improvement lie in multiple aspects such as extreme natural environment (drought, less rainfall, strong wind and sand), poor soil quality, high cost, and low sustainability.

[0007] The comprehensive utilization of fly ash has become a research hotspot. However, most traditional utilization methods focus on the field of building materials (pursuing the characteristics of low density, high strength, and low water absorption), and there are few reports on the improvement of desertified soil. For example, CN112552021A discloses "a fly ash ceramsite and its preparation method", and fly ash ceramsite is obtained by sintering. Its bulk density is 450-750 kg / m3, with low water absorption and a strength of 8.5 MPa. However, it does not have nutritional and water retention properties and is difficult to be applied to the improvement of desertified soil. CN 110484267A discloses "a mineral soil conditioner produced from fly ash and its preparation method". The water content of the obtained mineral soil conditioner is less than 2 wt%, the content of citric acid-soluble silicon dioxide is above 15 wt%, the content of citric acid-soluble calcium oxide is greater than 25 wt%, the content of citric acid-soluble potassium oxide is greater than 4 wt%, the content of citric acid-soluble magnesium oxide is greater than 2 wt%, the total effective component of nutrients is not less than 80 wt%, and the pH value is 9-12. This process has more steps, mainly focusing on the removal process of heavy metals in fly ash, and filter residues containing heavy metals are generated during the process, which increases its production cost and makes it difficult to consume fly ash on a large scale. In addition, the main nutrient component in this conditioner is potassium, lacking nitrogen and phosphorus among the three major elements for plant growth, and its water retention property is unknown. Whether it can be applied to the improvement of desert soil remains to be discussed. There are reports that directly applying fly ash to the land for soil improvement has achieved good results. However, in extremely arid and sandy desertified areas, if fly ash is directly applied to the land, the fly ash will disperse in the air with the wind, causing serious air pollution. Therefore, it is not feasible to directly use fly ash for the treatment of desertified land.

[0008] Therefore, it is an urgent need to develop a nutrient and moisture-retaining ceramsite that has both nutritional and water retention properties and can be used for the improvement of desertified soil. Summary of the Invention

[0009] The technical problem to be solved by the present invention is to provide a nutrient and moisture-retaining ceramsite, its preparation method, application and application method in view of the above-mentioned deficiencies of the prior art. This nutrient and moisture-retaining ceramsite not only realizes the large-scale and resource utilization of fly ash from power plants, an industrial waste, but also provides an innovative way for the ecological restoration of soil improvement in desertified areas using fly ash from power plants. Through a special process, fly ash from power plants is transformed into a nutrient and moisture-retaining ceramsite with a unique structure and composition, and then has the functions of nutrient release and water retention. After being applied to the improvement of desertified soil, it can effectively improve the physical and chemical properties of the soil, enhance soil fertility, and promote plant growth.

[0010] To solve the above technical problems, the present invention provides the following technical solutions: A preparation method of a nutrient and moisture-retaining ceramsite, comprising the following steps: S1. Sieve fly ash from a power plant to obtain fly ash, mix the fly ash with commercial cement, solid nutrient powder and coal gangue powder, and stir evenly to obtain ceramsite powder; add hydrogen peroxide and mix evenly to obtain porous ceramsite powder; S2, mixing the auxiliary agent, the nutrient agent and the deionized water uniformly to obtain a nutrient solution; S3, granulating and aging the ceramsite powder obtained in S1 and immersing it in the nutrient solution in S2 to obtain nutrient ceramsite; S4, using phosphorylated chitosan to encapsulate the nutritional ceramsite obtained in S3, and then reacting it with amino alkynyl groups to obtain alkynyl ceramsite after formylation with sodium periodate; S5, obtaining modified microcapsules using sodium alginate as the wall material and paraffin as the core material; S6, mixing the acetylated ceramsite and the modified microcapsule to obtain the nutrient-moisturizing ceramsite.

[0011] Preferably, the components of the fly ash from the power plant in S1 are 40-70% silicon dioxide, 15-25% aluminum oxide, 3-10% iron oxide, 1-7% calcium oxide, 0.5-2% potassium oxide and impurities by weight, and the impurities include titanium dioxide and phosphorus pentoxide; the sieve specification for screening the fly ash from the power plant is 40 mesh, and the components of the solid nutrient powder are 15 parts of apatite and 85 parts of phosphogypsum by weight; the commercial cement is 32.5, 32.5R, 42.5, 42.5R, 52.5, 5 Any one of eight strength grades: 2.5R, 62.5 and 62.5R; the stirring speed is 100r / min and the time is 60min; the mass ratio of the fly ash, the commercial cement, the solid nutrient powder and the coal gangue powder is (75-94.4): (0.1-5): (0.5-5): (5-15); the granulation in S3 uses a disc granulator, and the speed of the disc granulator is 50-200r / min; the hydrogen peroxide is 0.02-0.1 times the mass of the ceramsite powder.

[0012] Preferably, the auxiliary agent in S2 is any one of the alkyl imidazole ionic liquids; the concentration of the alkyl imidazole ionic liquid is 0.01-0.05 mol / L; the nutrient agent is a mixture of any one or more of dipotassium hydrogen phosphate, potassium dihydrogen phosphate, monoammonium phosphate, diammonium phosphate and ammonium sulfate, and the concentrations of the dipotassium hydrogen phosphate, potassium dihydrogen phosphate, monoammonium phosphate, diammonium phosphate and ammonium sulfate are all 0.01-0.5 mol / L.

[0013] The chemical structure of alkyl imidazole ionic liquid is:

[0014] Preferably, the preparation method of the nutrient ceramsite in S3 is as follows: granulate and age the ceramsite powder obtained in S1, then immerse it in the nutrient solution in S2, with a liquid-solid ratio of (10 - 20):1, oscillate at room temperature for 4 - 5 h, and obtain the nutrient ceramsite after drying; the aging temperature is 20 - 40 °C and the time is 24 - 72 h; the particle size of the nutrient ceramsite is 3 - 20 mm.

[0015] Preferably, the preparation method of the alkynylated ceramsite in S4 is as follows: mix chitosan, urea, and phosphoric acid in a mass ratio of 1:(5 - 7):(50 - 60), react at 110 - 120 °C for 3 - 4 h, cool to room temperature, and obtain phosphorylated chitosan through ethanol precipitation, acetone washing, and drying; dissolve the phosphorylated chitosan in pure water to obtain a phosphorylated chitosan solution, immerse the nutrient ceramsite in the phosphorylated chitosan solution, stir at room temperature for 2 - 3 h, add a crosslinking agent and react for 30 - 40 min, and obtain pre-modified ceramsite through washing and drying; the mass ratio of phosphorylated chitosan, pure water, crosslinking agent, and nutrient ceramsite is 1:(100 - 120):(1 - 1.5):(1 - 2); the crosslinking agent is obtained by mixing glutaraldehyde and calcium chloride in a mass ratio of 1:(4 - 5); immerse the pre-modified ceramsite in an oxidation solution, with a liquid-solid ratio of (10 - 20):1 mL / g, and the oxidation solution is a sodium periodate solution with a concentration of 0.3 - 1.0 g / mL; under light-shielded conditions, stir and react at room temperature for 2 - 3 h, then add ethylene glycol to quench, continue to stir for 15 - 20 min, and obtain aldehyde-functionalized ceramsite through washing with pure water and saturated sodium carbonate solution and drying; dissolve 1-amino-3-butyne in an acetic acid-sodium acetate buffer solution with pH = 4.0 - 5.0, and the concentration of 1-amino-3-butyne in the acetic acid-sodium acetate buffer solution is 0.1 - 0.5 M; immerse the aldehyde-functionalized ceramsite in the above buffer solution, with a liquid-solid ratio of (10 - 20):1 mL / g; react at room temperature for 4 - 6 h under light-shielded conditions; obtain the alkynylated ceramsite through filtration, washing, and drying.

[0016] Preferably, the preparation method of the modified microcapsules in S5 is as follows: Dissolve sodium alginate in 2-(N-morpholino)ethanesulfonic acid buffer solution with a pH of 5.5 - 6.5, and successively add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and stir at room temperature for activation for 1 h; Dropwise add 2-azidoethylamine at a dropping rate of 0.1 mL / min, continue to react in the dark at room temperature for 20 - 24 h, dialyze for 5 - 6 days and then freeze-dry to obtain azido sodium alginate; The mass ratio of sodium alginate, 2-(N-morpholino)ethanesulfonic acid buffer solution, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, and 2-azidoethylamine is 1:(70 - 80):(0.5 - 0.7):(0.2 - 0.4):(0.6 - 0.8); Mix azido sodium alginate, calcium carbonate, and pure water according to a mass ratio of 1:(0.8 - 1.0):(100 - 120), add paraffin with a mass 1 - 2 times that of azido sodium alginate and an emulsifier with a mass 0.1 - 0.2 times that of paraffin with a mass 1 - 2 times that of azido sodium alginate. The emulsifier is Span 80; Emulsify at a high speed of 8000 - 10000 rpm at 60 - 65 °C for 10 - 20 min to obtain the primary emulsion. Drop the primary emulsion into the petroleum ether-acetic acid mixture at a dropping rate of 0.6 mL / min, stir for 30 - 40 min, then add calcium chloride solution and continue to stir for 2 - 3 h, and obtain the modified microcapsules after filtration, washing, and drying. The petroleum ether-acetic acid mixture is obtained by mixing petroleum ether and acetic acid according to a volume ratio of 100:1.

[0017] Preferably, the preparation method of the nutrient and moisture-retaining ceramsite is as follows: Ultrasonically disperse the alkynylated ceramsite, modified microcapsules, catalyst solution, and phosphate buffer solution for 10 - 20 min, react at room temperature in the dark for 6 - 12 h, add 0.1 M ethylenediaminetetraacetic acid solution, continue to stir for 30 - 40 min, and obtain the nutrient and moisture-retaining ceramsite after suction filtration, washing with phosphate buffer solution, deionized water, and ethanol, and drying; The mass ratio of the alkynylated ceramsite, modified microcapsules, catalyst solution, phosphate buffer solution, and 0.1 M ethylenediaminetetraacetic acid solution is 1:(0.5 - 0.7):(3 - 4):(5 - 6); The catalyst solution is obtained by mixing copper sulfate and sodium ascorbate according to a volume ratio of 1:2.

[0018] The present invention also provides a nutrient and moisture-retaining ceramsite prepared by the preparation method of the nutrient and moisture-retaining ceramsite according to any one of the above.

[0019] The present invention also provides the application of the above nutrient and moisture-retaining ceramsite in desertified soil improvement.

[0020] The present invention also provides an application method of the above nutrient and moisture-retaining ceramsite in desertified soil improvement, which is characterized by including the following steps: S1. Divide the nutrient - moisturizing ceramsite according to particle size into: small ceramsite with a particle size of 3 - 7 mm, medium ceramsite with a particle size of 8 - 12 mm, and large ceramsite with a particle size of 13 - 20 mm; S2. Directly cover any one or a mixture of the small ceramsite, medium ceramsite, and large ceramsite in S1 on the desertified land to form a nutrient - moisturizing ceramsite layer with a thickness of 300 - 400 mm; S3. The nutrient - moisturizing ceramsite layer formed in S2 is divided into five forms: the form of large - sized at the top and small - sized at the bottom, the uniform form, the interlayer form, the mixed form, and the mixing - uniform form.

[0021] Preferably, the form of large - sized at the top and small - sized at the bottom in S3 is: lay any two or three of the small ceramsite, medium ceramsite, and large ceramsite in the form of large - sized at the top and small - sized at the bottom; The uniform form is: lay the small ceramsite, medium ceramsite, or large ceramsite; The interlayer form is: select any two of the small ceramsite, medium ceramsite, and large ceramsite to be laid in three layers, with the middle layer being ceramsite of one particle size and the upper and lower layers being ceramsite of another particle size; The mixed form is: mix the small ceramsite, medium ceramsite, and large ceramsite evenly according to the mass ratio of 60:30:10, and then lay them; The mixing - uniform form is: mix the small ceramsite, medium ceramsite, and large ceramsite with the desertified soil to be treated evenly according to the mass ratio of (4 - 5):(3 - 4):(1 - 3):100, and lay them on the desertified land to form a ceramsite - desertified - soil mixing - uniform layer.

[0022] The present invention has the following advantages compared with the prior art: Compared with traditional ceramsite mainly applied in the building materials field, which mainly pursues the performance of low density, high strength, and low water absorption, the nutrient - moisturizing ceramsite prepared by the present invention is mainly aimed at the improvement of desertified soil, expanding the large - scale utilization field of power plant fly ash.

[0023] When preparing the nutrient - moisturizing ceramsite of the present invention, aging porous ceramsite is prepared by using hydrogen peroxide as a foaming agent. The porous ceramsite is immersed in the nutrient solution so that the porous ceramsite adsorbs nutrient elements on the inner and outer surfaces of the pores. Phosphorylated chitosan forms a film layer with antibacterial and moisturizing properties on the surface of the ceramsite in the presence of a cross - linker. During the formation of this film layer, phosphorus element, one of the nutrient elements, is also introduced. Sodium periodate is used to oxidize the surface chitosan film layer to generate aldehyde groups, and the aldehyde groups and 1 - amino - 3 - butyne react to generate Schiff base, introducing alkynyl groups on the surface of the ceramsite. The formation of Schiff base also has good antibacterial properties; Secondly, using phase change material paraffin wax as the core material, sodium alginate azide as the wall material, and calcium ions as the cross-linking agent, sodium alginate azide microcapsules with both phase change energy storage and click chemistry modification potential are generated; sodium alginate azide microcapsules and ceramsite containing alkynyl groups generate triazole structures with antibacterial properties through click chemical reactions, thereby connecting the phase change microcapsule structure to the surface of the ceramsite. The phase change microcapsules can absorb or release latent heat through solid-liquid phase changes, and are used in desert areas with large temperature differences between day and night. The porous structure of the ceramsite itself can adsorb moisture, while the phase change microcapsules can reduce evaporation through temperature regulation. The combination of the two forms a dual-effect water retention system, which can further improve the moisture retention performance of the ceramsite.

[0024] When modifying the ceramsite in the present invention, the raw materials used are mainly natural polymer materials with good hydrophilic and moisture retention properties, and phosphorus and nitrogen nutrient elements are introduced during the modification process. Chitosan, Schiff base, and triazole are also used for co-antibacterial. This function can, to a certain extent, inhibit the invasion of pathogenic bacteria on plant roots, maintain soil health, and promote plant growth.

[0025] Considering the differences in the original soil composition and soil particle size in different desertification areas, the present invention provides five typical nutrient and moisture-retaining ceramsite layer structures to meet the needs of different desertification land treatment and vegetation growth, and at the same time can effectively prevent strong winds and high winds in desertification areas from blowing sand and dust into the air, thereby reducing the occurrence of sandstorms and sand-raising weather.

[0026] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. Description of the Drawings

[0027] Figure 1 is a schematic structural diagram of the nutrient and moisture-retaining ceramsite layer.

[0028] Figure 2 is a photo of the nutrient and moisture-retaining ceramsite prepared by the present invention. Detailed Embodiments

[0029] The technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0030] The concentration of hydrogen peroxide in the following examples and comparisons is 30 wt%. Example 1:

[0031] A thermal power plant in Ningxia Hui Autonomous Region has an annual output of 1.5 million tons of fly ash. The fly ash from this power plant contains 55.59 wt% of silicon dioxide, 1.86 wt% of potassium oxide, 21.39 wt% of aluminum oxide, 6.54 wt% of calcium oxide, 6.49 wt% of iron oxide, and the rest are impurities, including titanium dioxide and phosphorus pentoxide. Heavy metals such as lead, cadmium, mercury, and copper are not detected.

[0032] This embodiment provides a method for preparing nutrient - moisturizing ceramsite, which includes the following steps: S1. Pass the fly ash from the power plant through a 40 - mesh sieve to obtain fly ash; mix the fly ash with commercial cement of strength grade 32.5, solid nutrient powder, and coal gangue powder, and use a cylindrical mixer to stir for 60 min at a rotation speed of 100 r / min to obtain ceramsite powder; add hydrogen peroxide and mix evenly to obtain porous ceramsite powder; The components of the solid nutrient powder are 15 parts of apatite and 85 parts of phosphogypsum by weight; the addition amount of the solid nutrient powder is 3.5 wt%, the addition amount of coal gangue is 7.5 wt%, the addition amount of commercial cement is 2.5 wt%, and the addition amount of fly ash is 86.5 wt%; the mass of the hydrogen peroxide is 0.03 times that of the ceramsite powder; S2. Mix 1 - methyl - 3 - hexylimidazolium chloride, dipotassium hydrogen phosphate, diammonium phosphate, and deionized water evenly to obtain a nutrient solution; the concentration of 1 - methyl - 3 - hexylimidazolium chloride is 0.02 mol / L; the concentrations of dipotassium hydrogen phosphate and diammonium phosphate are both 0.05 mol / L; S3. Put the porous ceramsite powder obtained in S1 into a disk granulator with a rotation speed of 75 r / min for granulation, carry out aging for 48 h at a temperature of 35°C, immerse it in the nutrient solution in S2, with a liquid - solid ratio of 10:1, oscillate at room temperature for 5 h, and dry to obtain nutrient ceramsite with particle sizes of 5 mm, 10 mm, and 15 mm; S4. Mix chitosan, urea, and phosphoric acid in a mass ratio of 1:5:50, react at 120 °C for 4 h. After cooling to room temperature, precipitate with ethanol, wash with acetone, and dry to obtain phosphorylated chitosan. Dissolve the phosphorylated chitosan in pure water to obtain a phosphorylated chitosan solution. Immerse the nutrient ceramsite in the phosphorylated chitosan solution and stir at room temperature for 3 h. Add a crosslinking agent and react for 40 min. Wash and dry to obtain pre-modified ceramsite. The mass ratio of phosphorylated chitosan, pure water, crosslinking agent, and nutrient ceramsite is 1:100:1:1. The crosslinking agent is obtained by mixing glutaraldehyde and calcium chloride in a mass ratio of 1:4. Immerse the pre-modified ceramsite in the oxidation solution with a liquid-solid ratio of 10:1 mL / g. The oxidation solution is a sodium periodate solution with a concentration of 0.3 g / mL. Under dark conditions, stir and react at room temperature for 3 h, then add ethylene glycol to quench, continue to stir for 20 min, wash with pure water and saturated sodium carbonate solution, and dry to obtain aldehyde-functionalized ceramsite. Dissolve 1-amino-3-butyne in an acetic acid-sodium acetate buffer solution with pH = 5.0, and the concentration of 1-amino-3-butyne in the acetic acid-sodium acetate buffer solution is 0.5 M. Immerse the aldehyde-functionalized ceramsite in the above buffer solution with a liquid-solid ratio of 10:1 mL / g. React at room temperature under dark conditions for 6 h. Filter, wash, and dry to obtain alkynyl-functionalized ceramsite; S5. Dissolve sodium alginate in a 2-(N-morpholino)ethanesulfonic acid buffer solution with pH 5.5, sequentially add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and stir and activate at room temperature for 1 h. Dropwise add 2-azidoethylamine at a dropping rate of 0.1 mL / min, continue to react at room temperature in the dark for 24 h, dialyze for 6 days, and then freeze-dry to obtain azido-functionalized sodium alginate. The mass ratio of sodium alginate, 2-(N-morpholino)ethanesulfonic acid buffer solution, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, and 2-azidoethylamine is 1:70:0.5:0.2:0.6. Mix azido-functionalized sodium alginate, calcium carbonate, and pure water in a mass ratio of 1:0.8:100, add paraffin with a mass 1 time that of azido-functionalized sodium alginate and an emulsifier with a mass 0.1 times that of paraffin with a mass 1 time that of azido-functionalized sodium alginate. The emulsifier is Span 80. Emulsify at 60 °C at a high speed of 10000 rpm for 20 min to obtain the primary emulsion. Dropwise add the primary emulsion to a petroleum ether-acetic acid mixture at a dropping rate of 0.6 mL / min, stir for 40 min, then add a calcium chloride solution and continue to stir for 3 h. Filter, wash, and dry to obtain modified microcapsules. The petroleum ether-acetic acid mixture is obtained by mixing petroleum ether and acetic acid in a volume ratio of 100:1; S6. Ultrasonically disperse the alkynylated ceramsite, modified microcapsules, catalyst solution, and phosphate buffer solution for 20 min, react for 12 h at room temperature in the dark, add 0.1 M ethylenediaminetetraacetic acid solution, continue stirring for 40 min, and filter, wash with phosphate buffer solution, deionized water, and ethanol, and then dry to obtain the nutrient and moisture-retaining ceramsite; the mass ratio of the alkynylated ceramsite, modified microcapsules, catalyst solution, phosphate buffer solution, and 0.1 M ethylenediaminetetraacetic acid solution is 1:0.5:3:5; the catalyst solution is obtained by mixing copper sulfate and sodium ascorbate in a volume ratio of 1:2.

[0033] Demonstrative test for desertified soil improvement: Select 5 mu of desertified land in a certain city in western Inner Mongolia for the demonstrative test of soil treatment. Divide the 5 mu of desertified land into four equal parts in a "plus" shape and number them counterclockwise as "1, 2, 3, 4" plots. Plots 1 and 3 are improved with the nutrient and moisture-retaining ceramsite of the present invention, and plots 2 and 4 are used as test controls. Uniformly select 50 sampling points in each of plots 1, 2, 3, and 4.

[0034] First, respectively select nutrient and moisture-retaining ceramsite with particle sizes of 5 mm, 10 mm, and 15 mm, and directly lay and construct them in the form of larger particle sizes at the bottom and smaller particle sizes at the top. The total height of the ceramsite layer is 300 mm, of which the height of the bottom layer is 150 mm (nutrient and moisture-retaining ceramsite with a particle size of 5 mm), the height of the middle layer is 100 mm (nutrient and moisture-retaining ceramsite with a particle size of 10 mm), and the height of the upper layer is 50 mm (nutrient and moisture-retaining ceramsite with a particle size of 15 mm). Second, conduct a one-time uniform sprinkler irrigation on the test land, with a water consumption of 500 m 3 / mu. Third, under natural conditions, after 48 h, conduct the first sampling at the sampling points of each plot at depths of 20 cm, 40 cm, and 60 cm, and conduct the second sampling at an interval of 7 days. Compare the soil moisture content and nutrient element content in the two samples. The results are shown in Table 1. The moisture content reduction in each layer of plots 1 and 3 is less than that of plots 2 and 4, indicating that the nutrient and moisture-retaining ceramsite layer has a moisture-retaining effect. The soluble nitrogen, phosphorus, and potassium contents in each layer of plots 1 and 3 are greater than those of plots 2 and 4, indicating that the nutrient and moisture-retaining ceramsite layer significantly improves the fertility of desertified soil. It can be seen that the nutrient and moisture-retaining ceramsite can very effectively improve desertified soil.

[0035] Table 1 Soil moisture content and nutrient element content of plots 1-4 Example 2:

[0036] A thermal power plant in Inner Mongolia Autonomous Region has an annual output of 2 million tons of fly ash. The fly ash from this power plant contains 63.14 wt% of silicon dioxide, 24.31 wt% of aluminum oxide, 1.19 wt% of potassium oxide, 1.07 wt% of calcium oxide, 6.26 wt% of iron oxide, and the rest are impurities, including titanium dioxide and phosphorus pentoxide. Heavy metals such as lead, cadmium, mercury, and copper are not detected.

[0037] This embodiment provides a method for preparing nutrient - moisturizing ceramsite, which includes the following steps: S1. Pass the fly ash from the power plant through a 40 - mesh sieve to obtain fly ash; mix the fly ash with commercial cement of strength grade 32.5, solid nutrient powder, and coal gangue powder, and stir with a cylindrical mixer at a rotation speed of 100 r / min for 60 min to obtain ceramsite powder; add hydrogen peroxide and mix evenly to obtain porous ceramsite powder; The components of the solid nutrient powder are 15 parts of apatite and 85 parts of phosphogypsum by weight; the addition amount of the solid nutrient powder is 4.5 wt%, the addition amount of coal gangue is 10.5 wt%, the addition amount of commercial cement is 1.5 wt%, and the addition amount of fly ash is 83.5 wt%; the hydrogen peroxide is 0.07 times the mass of the ceramsite powder. S2. Mix 1 - methyl - 3 - hexylimidazolium chloride, dipotassium hydrogen phosphate, ammonium sulfate, and deionized water evenly to obtain a nutrient solution; the concentration of 1 - methyl - 3 - hexylimidazolium chloride is 0.03 mol / L; the concentrations of dipotassium hydrogen phosphate and ammonium sulfate are both 0.08 mol / L. S3. Put the ceramsite powder obtained in S1 into a disk granulator with a rotation speed of 75 r / min for granulation, and carry out aging for 48 h at a temperature of 35°C; immerse it in the nutrient solution in S2, with a liquid - solid ratio of 10:1, and obtain nutrient ceramsite with particle sizes of 3 mm, 8 mm, and 13 mm after drying. S4. Carry out aging for 48 h at a temperature of 35°C on the nutrient ceramsite masterbatch obtained in S3, immerse it in the nutrient solution in S2, with a liquid - solid ratio of 15:1, oscillate at room temperature for 4.5 h, and obtain nutrient ceramsite with particle sizes of 3 mm, 8 mm, and 13 mm after drying. S4. Mix chitosan, urea, and phosphoric acid in a mass ratio of 1:5:55, react at 115 °C for 3.5 h. After cooling to room temperature, precipitate with ethanol, wash with acetone, and dry to obtain phosphorylated chitosan. Dissolve the phosphorylated chitosan in pure water to obtain a phosphorylated chitosan solution. Immerse the nutrient ceramsite in the phosphorylated chitosan solution and stir at room temperature for 2.5 h. Add a crosslinking agent and react for 35 min. Wash and dry to obtain pre-modified ceramsite. The mass ratio of phosphorylated chitosan, pure water, crosslinking agent, and nutrient ceramsite is 1:110:1.3:1.5. The crosslinking agent is obtained by mixing glutaraldehyde and calcium chloride in a mass ratio of 1:4.5. Immerse the pre-modified ceramsite in the oxidation solution with a liquid-solid ratio of 15:1 mL / g. The oxidation solution is a sodium periodate solution with a concentration of 0.7 g / mL. Under dark conditions, stir and react at room temperature for 2.5 h, then add ethylene glycol to quench, continue to stir for 17 min, wash with pure water and saturated sodium carbonate solution, and dry to obtain aldehyde-functionalized ceramsite. Dissolve 1-amino-3-butyne in an acetic acid-sodium acetate buffer solution with pH = 4.5, and the concentration of 1-amino-3-butyne in the acetic acid-sodium acetate buffer solution is 0.3 M. Immerse the aldehyde-functionalized ceramsite in the above buffer solution with a liquid-solid ratio of 15:1 mL / g. React at room temperature under dark conditions for 5 h. Filter, wash, and dry to obtain alkynyl-functionalized ceramsite. S5. Dissolve sodium alginate in a 2-(N-morpholino)ethanesulfonic acid buffer solution with pH = 6.0, sequentially add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and stir and activate at room temperature for 1 h. Dropwise add 2-azidoethylamine at a dropping rate of 0.1 mL / min, continue to react at room temperature in the dark for 22 h, dialyze for 5 days, and then freeze-dry to obtain azido-sodium alginate. The mass ratio of sodium alginate, 2-(N-morpholino)ethanesulfonic acid buffer solution, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, and 2-azidoethylamine is 1:60:0.6:0.3:0.7. Mix azido-sodium alginate, calcium carbonate, and pure water in a mass ratio of 1:0.9:110, add paraffin with a mass 1.5 times that of azido-sodium alginate and an emulsifier with a mass 0.15 times that of paraffin with a mass 1.5 times that of azido-sodium alginate. The emulsifier is Span 80. Emulsify at 63 °C at 9000 rpm for 15 min to obtain the primary emulsion. Dropwise add the primary emulsion to a petroleum ether-acetic acid mixture at a dropping rate of 0.6 mL / min, stir for 35 min, then add calcium chloride solution and continue to stir for 2.5 h. Filter, wash, and dry to obtain modified microcapsules. The petroleum ether-acetic acid mixture is obtained by mixing petroleum ether and acetic acid in a volume ratio of 100:1. S6. Ultrasonically disperse the alkynylated ceramsite, modified microcapsules, catalyst solution, and phosphate buffer solution for 15 min, react at room temperature in the dark for 9 h, add 0.1 M ethylenediaminetetraacetic acid solution, continue stirring for 35 min, and filter, wash with phosphate buffer solution, deionized water, and ethanol, and then dry to obtain the nutrient and moisture-retaining ceramsite; the mass ratio of the alkynylated ceramsite, modified microcapsules, catalyst solution, phosphate buffer solution, and 0.1 M ethylenediaminetetraacetic acid solution is 1:0.6:3.5:5.5; the catalyst solution is obtained by mixing copper sulfate and sodium ascorbate in a volume ratio of 1:2.

[0038] Demonstration test for desertified soil improvement: Select 5 mu of desertified land in a certain city in western Inner Mongolia for a demonstration test on soil improvement. Divide the 5 mu of desertified land into four equal parts in a "cross" shape and number them counterclockwise as "1, 2, 3, 4" plots. Plots 1 and 3 are improved with the ceramsite of the present invention, and plots 2 and 4 are used as test controls. Uniformly select 50 sampling points in each of plots 1, 2, 3, and 4.

[0039] First, respectively select nutrient and moisture-retaining ceramsites with particle sizes of 3 mm, 8 mm, and 13 mm, and directly lay them in the form of larger particles on the upper layer and smaller particles on the lower layer. The total height of the ceramsite layer is 400 mm, of which the height of the uppermost layer is 100 mm (nutrient and moisture-retaining ceramsite with a particle size of 13 mm), the height of the middle layer is 150 mm (nutrient and moisture-retaining ceramsite with a particle size of 8 mm), and the height of the lower layer is 150 mm (nutrient and moisture-retaining ceramsite with a particle size of 3 mm). Second, uniformly spray-irrigate the test land once, with a water consumption of 500 m 3 / mu. Third, under natural conditions, after 48 h, conduct the first sampling at the sampling points in each plot at depths of 30 cm, 50 cm, and 60 cm, and conduct the second sampling at an interval of 7 days. Compare the soil moisture content and nutrient element content in the two samples. The results are shown in Table 2. The moisture content reduction in each layer of plots 1 and 3 is less than that in plots 2 and 4, indicating that the nutrient and moisture-retaining ceramsite layer has a moisture-retaining effect. The soluble nitrogen, phosphorus, and potassium contents in each layer of plots 1 and 3 are greater than those in plots 2 and 4, indicating that the nutrient and moisture-retaining ceramsite layer significantly improves the fertility of desertified soil. It can be seen that the nutrient and moisture-retaining ceramsite can very effectively improve desertified soil.

[0040] Table 2 Soil moisture content and nutrient element content of plots 1-4 Example 3:

[0041] A thermal power plant in Shaanxi Province produces 2 million tons of fly ash annually. The fly ash from this power plant contains 41.05 wt% of silicon dioxide, 23.84 wt% of aluminum oxide, 1.33 wt% of potassium oxide, 6.38 wt% of calcium oxide, 9.41 wt% of iron oxide, and the rest are impurities, including titanium dioxide and phosphorus pentoxide. Heavy metals such as lead, cadmium, mercury, and copper are not detected.

[0042] This embodiment provides a method for preparing nutrient moisturizing ceramsite, including the following steps: S1. Pass the fly ash from the power plant through a 40-mesh sieve to obtain fly ash; mix the fly ash with commercial cement of strength grade 42.5, solid nutrient powder, and coal gangue powder, and stir with a cylindrical mixer for 60 min under the condition of a rotation speed of 100 r / min to obtain ceramsite powder; add hydrogen peroxide and mix evenly to obtain porous ceramsite powder; The components of the solid nutrient powder are 15 parts of apatite and 85 parts of phosphogypsum by weight; the addition amount of the solid nutrient powder is 4.5 wt%, the addition amount of coal gangue is 12.5 wt%, the addition amount of commercial cement is 1.8 wt%, and the addition amount of fly ash is 81.2 wt%; the mass of the hydrogen peroxide is 0.09 times that of the ceramsite powder; S2. Mix 1-methyl-3-hexylimidazolium chloride, dipotassium hydrogen phosphate, ammonium sulfate, and deionized water evenly to obtain a nutrient solution; the concentration of 1-methyl-3-hexylimidazolium chloride is 0.02 mol / L; the concentrations of dipotassium hydrogen phosphate and ammonium sulfate are both 0.3 mol / L; S3. Put the ceramsite powder obtained in S1 into a disk granulator with a rotation speed of 90 r / min for granulation, and carry out aging for 48 h under the condition of a temperature of 35°C, S4. Carry out aging for 48 h under the condition of a temperature of 35°C on the nutrient ceramsite masterbatch obtained in S3, immerse it in the nutrient solution in S2, with a liquid-solid ratio of 20:1, oscillate at room temperature for 5 h, and dry to obtain nutrient ceramsite with particle sizes of 5 mm, 9 mm, and 15 mm; S4. Mix chitosan, urea, and phosphoric acid in a mass ratio of 1:7:60, react at 110 °C for 3 h. After cooling to room temperature, precipitate with ethanol, wash with acetone, and dry to obtain phosphorylated chitosan. Dissolve the phosphorylated chitosan in pure water to obtain a phosphorylated chitosan solution. Immerse the nutrient ceramsite in the phosphorylated chitosan solution and stir at room temperature for 2 h. Add a crosslinking agent and react for 30 min. Wash and dry to obtain pre-modified ceramsite. The mass ratio of phosphorylated chitosan, pure water, crosslinking agent, and nutrient ceramsite is 1:120:1.5:2. The crosslinking agent is obtained by mixing glutaraldehyde and calcium chloride in a mass ratio of 1:5. Immerse the pre-modified ceramsite in the oxidation solution with a liquid-solid ratio of 20:1 mL / g. The oxidation solution is a sodium periodate solution with a concentration of 1.0 g / mL. Under dark conditions, stir and react at room temperature for 2 h, then add ethylene glycol to quench, continue to stir for 15 min, wash with pure water and saturated sodium carbonate solution, and dry to obtain aldehyde-functionalized ceramsite. Dissolve 1-amino-3-butyne in an acetic acid-sodium acetate buffer solution with pH = 4.0, and the concentration of 1-amino-3-butyne in the acetic acid-sodium acetate buffer solution is 0.5 M. Immerse the aldehyde-functionalized ceramsite in the above buffer solution with a liquid-solid ratio of 20:1 mL / g. React at room temperature under dark conditions for 4 h. Filter, wash, and dry to obtain alkynyl-functionalized ceramsite. S5. Dissolve sodium alginate in a 2-(N-morpholino)ethanesulfonic acid buffer solution with pH 5.5, sequentially add 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride and N-hydroxysuccinimide, and stir and activate at room temperature for 1 h. Dropwise add 2-azidoethylamine at a dropping rate of 0.1 mL / min, continue to react at room temperature in the dark for 20 h, dialyze for 5 days, and then freeze-dry to obtain azido-functionalized sodium alginate. The mass ratio of sodium alginate, 2-(N-morpholino)ethanesulfonic acid buffer solution, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, and 2-azidoethylamine is 1:80:0.7:0.4:0.8. Mix azido-functionalized sodium alginate, calcium carbonate, and pure water in a mass ratio of 1:1.0:120, add paraffin wax twice the mass of azido-functionalized sodium alginate and an emulsifier 0.2 times the mass of paraffin wax twice the mass of azido-functionalized sodium alginate. The emulsifier is Span 80. Emulsify at 65 °C at 8000 rpm for 20 min to obtain the primary emulsion. Dropwise add the primary emulsion to a petroleum ether-acetic acid mixture at a dropping rate of 0.6 mL / min, stir for 30 min, then add calcium chloride solution and continue to stir for 2 h. Filter, wash, and dry to obtain modified microcapsules. The petroleum ether-acetic acid mixture is obtained by mixing petroleum ether and acetic acid in a volume ratio of 100:1. S6. Ultrasonically disperse the alkynylated ceramsite, modified microcapsules, catalyst solution, and phosphate buffer solution for 10 min, react for 6 h at room temperature in the dark, add 0.1 M ethylenediaminetetraacetic acid solution, continue stirring for 30 min, and filter, wash with phosphate buffer solution, deionized water, and ethanol, and then dry to obtain the nutrient and moisture-retaining ceramsite. The mass ratio of the alkynylated ceramsite, modified microcapsules, catalyst solution, phosphate buffer solution, and 0.1 M ethylenediaminetetraacetic acid solution is 1:0.7:4:6. The catalyst solution is obtained by mixing copper sulfate and sodium ascorbate at a volume ratio of 1:2.

[0043] Demonstration test for desertified soil improvement: Select 5 mu of desertified land in a certain city in western Inner Mongolia for the demonstration test of soil treatment. Divide the 5 mu of desertified land into four equal parts in a "plus" shape and number them counterclockwise as "1, 2, 3, 4" plots. Plots 1 and 3 are improved with the ceramsite of the present invention, and plots 2 and 4 are used as test controls. Uniformly select 50 sampling points in each of plots 1, 2, 3, and 4.

[0044] First, select nutrient ceramsites with particle sizes of 5 mm, 9 mm, and 15 mm respectively, mix them evenly according to the proportions that the ceramsites with particle sizes of 5 mm, 9 mm, and 15 mm account for 60 wt%, 30 wt%, and 10 wt% respectively, and then carry out direct laying construction. The total height of the nutrient and moisture-retaining ceramsite layer is 400 mm. Second, carry out a one-time uniform sprinkler irrigation on the test land, with a water consumption of 500 m 3 / mu. Third, after 48 h under natural conditions, take the first samples at the sampling points in each plot at depths of 30 cm, 50 cm, and 60 cm respectively, and take the second samples at an interval of 7 days. Compare the soil moisture content and nutrient element content in the two samples. The results are shown in Table 3. The moisture content reduction in each layer of plots 1 and 3 is less than that of plots 2 and 4, indicating that the nutrient and moisture-retaining ceramsite layer has a moisture-retaining effect. The contents of soluble nitrogen, phosphorus, and potassium in each layer of plots 1 and 3 are greater than those of plots 2 and 4, indicating that the nutrient and moisture-retaining ceramsite layer significantly improves the fertility of desertified soil. It can be seen that the nutrient and moisture-retaining ceramsite can very effectively improve desertified soil.

[0045] Table 3 Soil moisture content and nutrient element content of plots 1 - 4

[0046] Test Example 1: Refer to the standard ASTM E2149-20 for the nutrient ceramsites with particle sizes of 5 mm, 3 mm, and 5 mm obtained in Examples 1 - 3. Add 2 g of ceramsite to 50 mL of bacterial solution, and use the oscillation method to test the antibacterial rate. The test results are shown in Table 4.

[0047] Table 4 Test results of antibacterial performance Antibacterial rate (%) Example 1 84.61 Example 2 87.43 Example 3 85.21 As can be seen from the results in Table 4, the nutrient - moisturizing ceramsite prepared by the present invention has certain antibacterial properties, and is expected to inhibit the invasion of pathogenic bacteria on plant roots to a certain extent, maintain soil health, and promote plant growth.

[0048] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above - mentioned exemplary embodiments, and without departing from the spirit or basic characteristics of the present invention, the present invention can be implemented in other specific forms. Therefore, from any point of view, the embodiments should be regarded as exemplary and non - restrictive. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, all changes falling within the meaning and scope of the equivalent elements of the claims are intended to be embraced within the present invention. Any reference signs in the claims should not be construed as limiting the claims involved.

Claims

1. A method for preparing nutritious and moisturizing ceramsite, characterized in that: The following steps are involved: S1. Sieve fly ash from a power plant to obtain fly ash, mix the fly ash with commercial cement, solid nutrient powder and coal gangue powder, and stir evenly to obtain ceramsite powder; Add hydrogen peroxide and mix well to obtain porous ceramsite powder; S2, mixing the auxiliary agent, the nutrient agent and the deionized water uniformly to obtain a nutrient solution; S3, granulating and aging the ceramsite powder obtained in S1 and immersing it in the nutrient solution in S2 to obtain nutrient ceramsite; S4, using phosphorylated chitosan to encapsulate the nutritional ceramsite obtained in S3, and then reacting it with amino alkynyl groups to obtain alkynyl ceramsite after formylation with sodium periodate; S5, obtaining modified microcapsules using sodium alginate as the wall material and paraffin as the core material; S6, mixing the acetylated ceramsite and the modified microcapsule to obtain the nutrient-moisturizing ceramsite.

2. The method for preparing a nutrient-moisturizing ceramsite according to claim 1, characterized in that: The components of the fly ash from the power plant in S1 are 40-70% silicon dioxide, 15-25% aluminum oxide, 3-10% iron oxide, 1-7% calcium oxide, 0.5-2% potassium oxide and impurities by weight, wherein the impurities include titanium dioxide and phosphorus pentoxide; the sieve specification for screening the fly ash from the power plant is 40 mesh; the components of the solid nutrient powder are 15 parts of apatite and 85 parts of phosphogypsum by weight; the commercial cement is 32.5, 32.5R, 42.5, 42.5R, 52.5, 52. Any one of eight strength grades: 5R, 62.5 and 62.5R; the stirring speed is 100r / min and the time is 60min; the mass ratio of the fly ash, the commercial cement, the solid nutrient powder and the coal gangue powder is (75-94.4): (0.1-5): (0.5-5): (5-15); the granulation in S3 uses a disc granulator, and the speed of the disc granulator is 50-200r / min; the hydrogen peroxide is 0.02-0.1 times the mass of the ceramsite powder.

3. The method for preparing a nutrient-moisturizing ceramsite according to claim 1, characterized in that: The auxiliary agent in S2 is any one of the alkyl imidazole ionic liquids; the concentration of the alkyl imidazole ionic liquid is 0.01-0.05 mol / L; the nutrient agent is a mixture of any one or more of dipotassium hydrogen phosphate, potassium dihydrogen phosphate, monoammonium phosphate, diammonium phosphate and ammonium sulfate, and the concentrations of the dipotassium hydrogen phosphate, potassium dihydrogen phosphate, monoammonium phosphate, diammonium phosphate and ammonium sulfate are all 0.01-0.5 mol / L.

4. The method for preparing a nutrient-moisturizing ceramsite according to claim 1, characterized in that: The preparation method of the nutritional ceramsite described in S3 is: granulate and age the ceramsite powder obtained in S1, immerse it in the nutrient solution in S2, the liquid-to-solid ratio is (10-20):1, oscillate at room temperature for 4-5 hours, and obtain the nutritional ceramsite after drying; the aging temperature is 20-40°C, and the time is 24-72 hours; the particle size of the nutritional ceramsite is 3-20 mm.

5. The method for preparing a nutrient-moisturizing ceramsite according to claim 1, characterized in that: S4 The preparation method of the alkyne-modified ceramsite is as follows: chitosan, urea and phosphoric acid are mixed in a mass ratio of 1: (5-7): (50-60), and reacted at 110-120°C for 3-4 hours to obtain phosphorylated chitosan; the nutritional ceramsite is immersed in the phosphorylated chitosan solution and stirred at room temperature for 2-3 hours, and a cross-linking agent is added to react for 30-40 minutes to obtain pre-modified ceramsite; the mass ratio of phosphorylated chitosan, pure water, cross-linking agent and nutritional ceramsite is 1: (100-120): (1-1.5): (1-2 ); the cross-linking agent is obtained by mixing glutaraldehyde and calcium chloride in a mass ratio of 1: (4-5); the pre-modified ceramsite is immersed in an oxidizing solution and reacted for 2-3 hours to obtain aldehyde-modified ceramsite, the liquid-to-solid ratio is (10-20): 1 mL / g, and the oxidizing solution is a sodium periodate solution with a concentration of 0.3-1.0 g / mL; the aldehyde-modified ceramsite is immersed in 1-amino-3-butyne acetic acid-sodium acetate buffer, the liquid-to-solid ratio is (10-20): 1 mL / g; the reaction is carried out at room temperature for 4-6 hours under light-proof conditions to obtain acetylenic ceramsite.

6. The method for preparing a nutrient-moisturizing ceramsite according to claim 1, characterized in that: The preparation method of the modified microcapsule described in S5 is as follows: sodium alginate, 2-(N-morpholino)ethanesulfonic acid buffer, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, and N-hydroxysuccinimide are activated at room temperature for 1 hour; 2-azidoethylamine is added dropwise to react at room temperature in the dark for 20-24 hours, and sodium azide alginate is obtained after dialysis for 5-6 days; sodium alginate, 2-(N-morpholino)ethanesulfonic acid buffer, 1-ethyl-3-(3-dimethylaminopropyl)carbodiimide hydrochloride, N-hydroxysuccinimide, 2- The mass ratio of ethylamine is 1: (70-80): (0.5-0.7): (0.2-0.4): (0.6-0.8); sodium azido alginate, calcium carbonate, pure water, paraffin and emulsifier are mixed and emulsified in a mass ratio of 1: (0.8-1.0): (100-120): (1-2): (1-2) to obtain colostrum, and the colostrum is added dropwise to a petroleum ether-acetic acid mixture, stirred for 30-40 minutes, and then calcium chloride solution is added and stirred for 2-3 hours. The modified microcapsules are obtained by filtering, washing and drying.

7. The method for preparing a nutrient-moisturizing ceramsite according to claim 1, characterized in that: S6 The preparation method of the nutritional ceramsite described in claim 1 is: reacting the acetylenic ceramsite, modified microcapsules, catalyst solution, and phosphate buffer for 6-12 hours, adding 0.1M ethylenediaminetetraacetic acid solution, and continuing stirring for 30-40 minutes to nourish and moisturize the ceramsite; the mass ratio of the acetylenic ceramsite, modified microcapsules, catalyst solution, phosphate buffer, and 0.1M ethylenediaminetetraacetic acid solution is 1: (0.5-0.7): (3-4): (5-6); the catalyst solution contains copper sulfate and sodium ascorbate.

8. A nutritional and moisturizing ceramsite prepared by the method for preparing the nutritional and moisturizing ceramsite according to any one of claims 1 to 7.

9. Use of the nutrient-moisturizing ceramsite as claimed in claim 8 in improving desertified soil.

10. A method for using the nutrient-moisturizing ceramsite as claimed in claim 8 in improving desertified soil, characterized in that: The following steps are involved: S1, the nutrient moisturizing ceramsite is divided into: small ceramsite with a particle size of 3-7 mm, medium ceramsite with a particle size of 8-12 mm and large ceramsite with a particle size of 13-20 mm according to the particle size; S2, directly covering the desertified land with a mixture of any one or more of the small ceramsite, medium ceramsite and large ceramsite in S1 to form a nutrient-moisturizing ceramsite layer with a thickness of 300-400 mm; The nutrient-moisturizing ceramsite layers formed in S3 and S2 are divided into five forms: large on top and small on bottom, uniform, sandwich, mixed, and well-mixed. The upper large and lower small form in S3 is: any two or three of the small ceramsite, the medium ceramsite and the large ceramsite are laid in the upper large and lower small form; The uniform form is: laying the small ceramsite, the medium ceramsite or the large ceramsite; The interlayer form is: any two of the small ceramsite, the medium ceramsite and the large ceramsite are selected and laid into three layers, the middle layer is ceramsite of one particle size, and the upper and lower layers are ceramsite of another particle size; The mixing method is: the small ceramsite, the medium ceramsite and the large ceramsite are mixed evenly in a mass ratio of 60:30:10, and then paved; The mixing method is: the small ceramsite, the medium ceramsite and the large ceramsite are mixed evenly with the desertified soil to be treated in a mass ratio of (4-5): (3-4): (1-3): 100, and then spread on the desertified land to form a ceramsite-desertified soil mixed layer.

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