Magnesium aluminum silicate mineral derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material, preparation method and application thereof

Abstract

The invention relates to the technical field of agricultural fertilizers, and particularly discloses a magnesium aluminum silicate mineral derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material as well as a preparation method and application of the magnesium aluminum silicate mineral derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material. Magnesium / aluminosilicate minerals are successfully converted into the layered magnesium-aluminum bimetal oxide-silicon oxide composite material with a high specific surface area and a developed pore structure, and the layered magnesium-aluminum bimetal oxide-silicon oxide composite material is combined with nutrients through a simple and convenient fertilizer preparation process to prepare the slow-release fertilizer. The slow-release fertilizer has the advantages of cheap and easily available raw materials, simple and efficient preparation process, stable slow-release performance, soil improvement effect and the like, and provides an efficient and environment-friendly new way for development of the slow-release fertilizer; the method has important significance for promoting sustainable agricultural development and realizing high-value utilization of silicate minerals in the agricultural field.

Description

Technical Field

[0001] The invention relates to the technical field of agricultural fertilizers, and in particular to a magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material, a preparation method and application thereof. Background Art

[0002] With the continued rapid growth of the global population and people's increasing expectations for food production and quality, the challenges faced by the agricultural sector are becoming increasingly severe. In past agricultural production, the widely used ordinary fertilizers often have the significant defects of nutrient release too quickly and the speed is difficult to control. This means that within a short period of time after fertilization, a large amount of nutrients are rapidly released into the soil, but the crops cannot fully absorb them in time, which not only causes a large amount of waste of precious nutrients in the fertilizer, but also greatly increases the economic cost of agricultural production. What's more serious is that the nutrients not absorbed by the crops enter the water and soil through rain erosion or soil infiltration, which may cause a series of environmental pollution problems, such as eutrophication of water bodies, soil compaction and acidification, etc., posing a huge threat to ecological balance and sustainable agricultural development. Therefore, it is of great practical significance to develop a new, efficient and environmentally friendly slow-release fertilizer.

[0003] As a layered material, hydrotalcite has shown excellent performance in the fields of drug sustained release and pollutant adsorption. Its application in the agricultural field is mainly concentrated on the carrier of slow-release pesticides and slow-release fertilizers. However, single hydrotalcite materials still have certain limitations in fertilizer carrier applications, such as low nutrient element loading and difficult to control release rate. Porous silica has a high specific surface area and a developed pore structure. Constructing hydrotalcite and porous silica into a composite material is conducive to the loading and sustained release of nutrients, while also improving soil structure and solidifying soil pollutants. It will be an ideal material for nutrient loading and sustained release. Patents CN202410777714.7, CN202310333668.7, CN201611052461.9 and CN201510038720.1 and papers doi.org / 10.1016 / j.jece.2015.05.009, doi.org / 10.1016 / j.micro-meso.2021.111247, doi.org / 10.1021 / acsanm.2c00927, doi.org / 10.1016 / j.micromes-o.2018.09.001 report a variety of hydrotalcite-silicon oxide composites. These materials are all made of high-purity chemical reagents, prepared by complex synthesis methods and strict synthesis conditions. They are costly and are mainly used in high-tech fields such as catalysis and drug sustained release.

[0004] In the current global context of advocating sustainable agricultural development, there is an urgent need for a new type of slow-release fertilizer material for agriculture with a wide range of raw materials, simple preparation process and low production cost. Using abundant and low-priced magnesium / aluminum silicate minerals in nature as raw materials, preparing magnesium-aluminum hydrotalcite-silicon oxide composite materials through simple conventional processes, and then calcining to obtain layered magnesium-aluminum bimetallic oxide-silicon oxide composite materials for slow-release fertilizer carriers, undoubtedly provides an innovative solution to this problem with great application prospects. Summary of the invention

[0005] In view of the above-mentioned shortcomings that currently exist, the present invention provides a magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material, a preparation method and an application thereof. The magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material of the present invention uses cheap and readily available magnesium / aluminum silicate minerals as raw materials, and through conventional synthesis processes, forms a layered magnesium aluminum bimetallic oxide-silicon oxide slow-release fertilizer with high adsorption capacity and good slow-release performance, thereby improving the utilization efficiency of the fertilizer and reducing the impact on the environment.

[0006] In order to achieve the above object, the present invention provides a method for preparing a magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material, the preparation method comprising the following steps:

[0007] S1. Grinding a silicate mineral into powder and then calcining it to obtain an activated silicate mineral; wherein the silicate mineral comprises any one or more of a magnesium silicate mineral, an aluminum silicate mineral, and a magnesium aluminum silicate mineral;

[0008] S2, acid leaching the activated silicate mineral to obtain a solid-liquid mixture A; wherein the solid-liquid mixture comprises insoluble silicon oxide and a leaching solution;

[0009] S3, based on the ratio of magnesium and aluminum ions in the hydrotalcite, selectively adding soluble magnesium salt and / or aluminum salt to the leachate, and obtaining a solid-liquid mixture B after stirring; wherein the solid-liquid mixture B comprises insoluble silicon oxide and the regulated leachate;

[0010] It should be noted that the amount of soluble salt introduced by selectively adding soluble magnesium salt and / or aluminum salt to the leachate is determined according to the concentration of magnesium and aluminum ions in the solution. (a) If the raw material is a magnesium silicate mineral, the leachate contains more magnesium ions and less aluminum ions, and it is necessary to introduce additional aluminum ions in proportion to the solid-liquid mixture; (b) If the raw material is an aluminum silicate mineral, the leachate contains more aluminum ions and less magnesium ions, and it is necessary to introduce additional magnesium ions in proportion to the solid-liquid mixture; (c) If the raw material contains both magnesium silicate and aluminum silicate or magnesium aluminum silicate minerals, the leachate contains appropriate magnesium ions and aluminum ions at the same time, and by controlling the raw material ratio, it is not necessary to introduce additional aluminum and magnesium ions or only a small amount of aluminum and magnesium ions need to be introduced.

[0011] S4, adjusting the pH value of the solid-liquid mixture B to 9-11, and then performing a hydrothermal reaction to synthesize a magnesium-aluminum hydrotalcite-silicon oxide composite material;

[0012] It should be noted that the purpose of adjusting the pH value of the solid-liquid mixture B is to promote the co-precipitation of magnesium and aluminum.

[0013] S5. After solid-liquid separation and drying, the magnesium aluminum hydrotalcite-silicon oxide composite material is calcined to obtain a magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material.

[0014] Furthermore, in step S1, the temperature of the calcination treatment is 600-1000° C., and the time of the calcination treatment is 0.5-3 h.

[0015] Further, in step S1, the magnesium silicate mineral includes any one or more of serpentine, talc, and sepiolite, and the aluminum silicate mineral includes one or more of pyrophyllite, kaolinite, halloysite, illite, and muscovite; the magnesium aluminum silicate mineral includes one or more of montmorillonite, palygorskite, vermiculite, chlorite, rectorite, and phlogopite.

[0016] Furthermore, in step S2, the solid-liquid ratio of the activated silicate mineral to the acid is 1:10-1:60, the acid used for the acid leaching is sulfuric acid or hydrochloric acid, the concentration of the sulfuric acid or hydrochloric acid is 0.5-4.0 mol / L, the leaching temperature of the acid leaching is 30-80°C, and the leaching time of the acid leaching is 0.5-5h.

[0017] Furthermore, in step S3, the molar ratio of magnesium to aluminum ions in the regulated leachate is 2:1-4:1, the concentration of magnesium ions in the regulated leachate is 1-16 g / L, and the concentration of aluminum ions in the regulated leachate is 0.5-8 g / L.

[0018] Furthermore, in step S4, the substance for adjusting the pH value of the solid-liquid mixture B is a mixed solution of sodium carbonate and sodium hydroxide; wherein the concentration of the sodium carbonate is 0.1-0.2 mol / L, and the concentration of the sodium hydroxide is 1.0-2.0 mol / L.

[0019] Furthermore, in step S4, the temperature of the hydrothermal reaction is 40-80° C., and the time of the hydrothermal reaction is 12-48 hours.

[0020] Furthermore, in step S5, the temperature of the calcination treatment is 400-800° C., and the time of the calcination treatment is 0.5-3 h.

[0021] Based on the same inventive concept, the present invention also provides a magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material prepared by any of the above-mentioned preparation methods.

[0022] Based on the same inventive concept, the present invention also provides the use of the magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material prepared by any of the above preparation methods in fertilizer slow release.

[0023] Furthermore, the fertilizer is specifically a layered magnesium aluminum bimetallic oxide-silicon oxide based nitrogen fertilizer, phosphate fertilizer, selenium fertilizer and composite slow-release fertilizer. The preparation method of the layered magnesium aluminum bimetallic oxide-silicon oxide based nitrogen fertilizer, phosphate fertilizer, selenium fertilizer and composite slow-release fertilizer is: adding the layered magnesium aluminum bimetallic oxide-silicon oxide composite material to a single nutrient solution or a composite nutrient solution of nitrogen, phosphorus and selenium, and obtaining the fertilizer after impregnation, adsorption and drying.

[0024] Furthermore, the single nutrient solution or compound nutrient solution of nitrogen, phosphorus and selenium includes but is not limited to any one or more soluble salts of potassium nitrate, ammonium nitrate, potassium phosphate, diammonium phosphate, sodium selenate and sodium selenite.

[0025] Furthermore, the magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material is immersed and adsorbed in the above-mentioned single nutrient solution or composite nutrient solution with various soluble salt concentrations of 1-10 g / L for 12-48 hours.

[0026] Beneficial effects of the present invention:

[0027] (1) The preparation method of layered magnesium aluminum bimetallic oxide-silicon oxide composite material has advantages and innovations: The present invention adopts the process of calcination-acid leaching-coprecipitation-hydrothermal-calcination to successfully transform magnesium / aluminum silicate minerals into layered magnesium aluminum bimetallic oxide-silicon oxide composite materials with high specific surface area and developed pore structure. Among them, calcination-acid leaching can efficiently extract magnesium, aluminum and other elements in the mineral and form porous silica, coprecipitation-hydrothermal can prepare magnesium aluminum ions and porous silica into magnesium aluminum hydrotalcite-silicon oxide composite materials, and calcination can effectively transform magnesium aluminum hydrotalcite-silicon oxide composite materials into layered magnesium aluminum bimetallic oxide-silicon oxide composite materials. Multiple conventional processes work together to efficiently activate and transform mineral components, thereby forming a composite material with excellent performance. The entire preparation process is simple and efficient to operate, has low requirements on equipment, is very suitable for large-scale industrial production, and has higher economic benefits and stronger market competitiveness.

[0028] (2) The raw materials for the preparation of layered magnesium aluminum bimetallic oxide-silicon oxide composite materials have advantages and innovations: The present invention uses serpentine, talc, sepiolite, pyrophyllite, kaolinite, halloysite, illite, muscovite, montmorillonite, palygorskite, vermiculite, chlorite, rectorite, phlogopite and other low-priced and easily accessible magnesium silicate minerals, aluminum silicate minerals, and magnesium aluminum silicate minerals as raw materials. These raw materials break through the limitations of using high-purity chemical products as raw materials in traditional synthesis methods, and provide a new idea for large-scale, low-cost production of high-performance composite materials. Compared with high-purity, high-cost chemical products, magnesium / aluminum silicate minerals as raw materials have significant advantages. They are abundant in reserves, widely distributed, low in cost, easy to obtain, and highly substitutable, which effectively reduces raw material costs and supply risks.

[0029] (3) The preparation and application of slow-release fertilizers are advantageous and innovative: The present invention uses a layered magnesium-aluminum bimetallic oxide-silicon oxide composite material as a slow-release fertilizer carrier. The composite material has different levels and complex interlayer structures, pore structures, inter-particle structures, and surface structures, which can allow nutrients to be adsorbed, attached, filled, and coated at different levels at various positions therein, and has different desorption and release rates. Therefore, the fertilizer can be efficiently loaded on the composite material through the impregnation adsorption method, and the slow release of nutrients can be achieved in the soil through the difference in the ease of release of nutrients at different positions in the material. It has long-term effectiveness and environmental adaptability, and the process is simple and the performance is stable, which has obvious advantages in large-scale production. In addition, the slow decomposition and release of bimetallic hydroxides and silicon oxide in the slow-release fertilizer can supply the necessary magnesium and silicon elements for plant growth, showing significant innovation in material application. In addition, at the soil improvement level, the material can enhance the soil's ability to retain water and fertilizer, regulate soil pH, promote microbial activity, and reduce heavy metal pollution, thereby creating favorable conditions for crop growth and effectively ensuring the quality and safety of agricultural products.

[0030] In summary, the present invention demonstrates significant advantages in terms of material innovation, slow-release control, environmental friendliness, economic benefits, etc., and provides a new method and material for the development of slow-release fertilizers. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 The present invention is a flow chart for preparing the composite slow-release fertilizer based on the layered magnesium-aluminum bimetallic oxide-silicon oxide composite material derived from magnesium-aluminum silicate minerals;

[0032] Figure 2 The SEM images of the magnesium aluminum silicate mineral-derived layered bimetallic oxide-silicon oxide composite materials described in Examples 1-6 of the present invention; wherein, (a) serpentine LDO@Si; (b) talc LDO@Si; (c) kaolin LDO@Si; (d) halloysite LDO@Si; (e) vermiculite LDO@Si; (f) chlorite LDO@Si;

[0033] Figure 3 The loading capacity of the layered magnesium aluminum bimetallic oxide-silicon oxide composite material prepared in Examples 1-6 of the present invention for nitrate, selenite and phosphate;

[0034] Figure 4 The static water release curve of the layered magnesium aluminum bimetallic oxide-silicon oxide based slow-release nitrogen fertilizer prepared in Examples 1-6 of the present invention;

[0035] Figure 5 The hydrostatic release curve of the layered magnesium-aluminum bimetallic oxide-silicon oxide-based slow-release phosphate fertilizer obtained in Examples 1-6 of the present invention;

[0036] Figure 6 The hydrostatic release curves of the layered magnesium-aluminum bimetallic oxide-silicon oxide-based slow-release selenium fertilizers prepared in Examples 1-6 of the present invention. DETAILED DESCRIPTION

[0037] To make the present invention easier to understand, the present invention is further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. Unless otherwise defined, the professional terms used below are consistent with the meanings understood by professional and technical personnel in the field; unless otherwise specified, the raw materials and reagents involved in this article can be purchased from the market or prepared by known methods.

[0038] Example 1

[0039] A method for preparing a slow-release fertilizer based on a layered magnesium-aluminum bimetallic oxide-silicon oxide composite material derived from magnesium-aluminum silicate minerals, wherein the preparation process is as follows: Figure 1 As shown:

[0040] In this embodiment, serpentine is used as the source of Mg and silicon oxide, and the contents of Mg and Si are 23.17% and 19.40% respectively.

[0041] After the serpentine is ground into powder, it is calcined at 600°C for 0.5h. The calcined serpentine is added to a 2mol / L hydrochloric acid solution at a solid-liquid ratio of 1:60, and stirred and leached at 40°C for 2h to obtain a solid-liquid mixture with a magnesium ion concentration of about 3.8g / L; aluminum salt is added to the mixed solution at a magnesium-aluminum molar ratio of 2:1, and stirred evenly; 0.2mol / L sodium carbonate and 2.0mol / L sodium hydroxide mixed solution are slowly added to the above mixture to adjust the pH to 9.5; then the solid-liquid mixture is hydrothermally synthesized at 60°C for 24h to prepare magnesium-aluminum hydrotalcite-oxygen The prepared serpentine LDH@Si was subjected to solid-liquid separation and drying, and then calcined at 450°C for 1.5h to obtain a layered magnesium-aluminum bimetallic oxide-silicon oxide composite material (serpentine LDO@Si); the serpentine LDO@Si was added to a composite solution of 1g / L potassium nitrate, 3g / L sodium selenite and 5g / L potassium phosphate at a solid-liquid ratio of 1:100, and then immersed and adsorbed for 24h and dried to obtain a layered magnesium-aluminum bimetallic oxide-silicon oxide-based composite slow-release fertilizer (CRSF). Figure 2 (a) SEM image shows that the oxide flakes are successfully grown on the silicon oxide surface; Figure 3 It can be seen that the loading amounts of N, Se, and P are 8.27 mg / g, 122.31 mg / g, and 50.94 mg / g, respectively. Figure 4-6 As shown, under static water conditions, 77.43% of N and 62.69% of Se were released within 120 h, while 51.36% of P was released within 240 h, showing excellent sustained release performance.

[0042] Example 2

[0043] A method for preparing a slow-release fertilizer based on a layered magnesium-aluminum bimetallic oxide-silicon oxide composite material derived from magnesium-aluminum silicate minerals, wherein the preparation process is as follows: Figure 1 As shown:

[0044] In this embodiment, talc is used as the source of Mg and silicon oxide, and the contents of Mg and Si are 19% and 29.5% respectively.

[0045] After the talc is ground into powder, it is calcined at 700°C for 2.0h. The calcined talc is added to a 0.5mol / L sulfuric acid solution at a solid-liquid ratio of 1:20, and stirred and leached at 30°C for 5h to obtain a solid-liquid mixture with a magnesium ion concentration of about 9.0g / L; aluminum salt is added to the mixed solution at a magnesium-aluminum molar ratio of 3:1, and stirred evenly; 0.2moL / L sodium carbonate and 2.0mol / L sodium hydroxide mixed solution are slowly added to the above mixture to adjust the pH to 9.0; then the solid-liquid mixture is subjected to hydrothermal synthesis at 80°C for 24h to prepare magnesium-aluminum hydrotalcite. Talc-silicon oxide composite material (talc LDH@Si); after solid-liquid separation and drying of the prepared talc LDH@Si, calcined at 500°C for 1.5h to obtain a layered magnesium-aluminum bimetallic oxide-silicon oxide composite material (talc LDO@Si); talc LDO@Si was added to a composite solution of 2g / L potassium nitrate, 5g / L sodium selenite and 8g / L potassium phosphate at a solid-liquid ratio of 1:100, immersed and adsorbed for 48h and then dried to obtain a layered magnesium-aluminum bimetallic oxide-silicon oxide-based composite slow-release fertilizer (CRSF). Figure 2 (b) SEM shows that the oxide nanosheets are cross-linked to form a layered structure. Figure 3 It can be seen that the loading amounts of N, Se, and P are 13.56 mg / g, 172.67 mg / g, and 68.69 mg / g, respectively. Figure 4-6 As shown, under static water conditions, 76.34% of N and 63.06% of Se were released within 120 h, while 47.2% of P was released within 240 h, showing excellent sustained release performance.

[0046] Example 3

[0047] A method for preparing a slow-release fertilizer based on a layered magnesium-aluminum bimetallic oxide-silicon oxide composite material derived from magnesium-aluminum silicate minerals, wherein the preparation process is as follows: Figure 1 As shown:

[0048] This embodiment uses kaolin as the source of Al and silicon oxide, and the contents of Al and Si are 23.93% and 21.71% respectively.

[0049] After kaolin is ground into powder, it is calcined at 800°C for 1.5h. The calcined kaolin is added to a 0.5mol / L sulfuric acid solution at a solid-liquid ratio of 1:40, and stirred and leached at 60°C for 3h to obtain a solid-liquid mixture with an aluminum ion concentration of about 5.6g / L; magnesium salt is added to the mixed solution at a magnesium-aluminum molar ratio of 2:1, and stirred evenly; 0.2moL / L sodium carbonate and 2.0mol / L sodium hydroxide mixed solution are slowly added to the above mixture to adjust the pH to 10.0; then the solid-liquid mixture is hydrothermally synthesized at 40°C for 24h to prepare magnesium-aluminum hydrotalcite- Silica composite material (kaolin LDH@Si); after solid-liquid separation and drying of the prepared kaolin LDH@Si, calcination at 550°C for 2.0h obtains a layered magnesium aluminum bimetallic oxide-silica composite material (kaolin LDO@Si); kaolin LDO@Si is added to a composite solution of 3g / L potassium nitrate, 10g / L sodium selenite and 10g / L potassium phosphate at a solid-liquid ratio of 1:100, immersed and adsorbed for 36h and then dried to obtain a layered magnesium aluminum bimetallic oxide-silica-based composite slow-release fertilizer (CRSF). Figure 2 (c) SEM image shows that an oxide nanosheet structure is formed on the surface of silicon oxide. Figure 3 It can be seen that the loading amounts of N, Se, and P are 7.38 mg / g, 112.44 mg / g, and 56.94 mg / g, respectively. Figure 4-6 As shown, under static water conditions, 56.89% of N and 58.16% of Se were released within 120 h, while 46.68% of P was released within 240 h, showing excellent sustained release performance.

[0050] Example 4

[0051] A method for preparing a slow-release fertilizer based on a layered bimetallic oxide-silicon oxide composite material derived from magnesium aluminum silicate minerals, the preparation process of which is as follows: Figure 1 As shown:

[0052] In this embodiment, halloysite is used as the source of Al and silicon oxide, and the contents of Al and Si are approximately 22.6% and 23.5%, respectively.

[0053] After the halloysite is ground into powder, it is calcined at 850°C for 3 hours. The calcined halloysite is added to a 1 mol / L sulfuric acid solution at a solid-liquid ratio of 1:30, and stirred and leached at 80°C for 3 hours to obtain a solid-liquid mixture with an aluminum ion concentration of about 7.1 g / L; magnesium salt is added to the mixed solution at a magnesium-aluminum molar ratio of 2:1, and stirred evenly; 0.2 mol / L sodium carbonate and 2.0 mol / L sodium hydroxide mixed solution are slowly added to the above mixture to adjust the pH to 9.0; then the solid-liquid mixture is hydrothermally synthesized at 80°C for 24 hours to prepare magnesium-aluminum hydrotalcite-oxide. Silicon composite material (halloysite LDH@Si); after solid-liquid separation and drying of the prepared halloysite LDH@Si, calcination at 600°C for 1.0h obtains a layered magnesium aluminum bimetallic oxide-silicon oxide composite material (halloysite LDO@Si); halloysite LDO@Si is added to 1g / L potassium nitrate, 3g / L sodium selenite and 5g / L potassium phosphate composite solution at a solid-liquid ratio of 1:100, immersed and adsorbed for 12h and then dried to obtain a layered magnesium aluminum bimetallic oxide-silicon oxide-based composite slow-release fertilizer (CRSF). Figure 2 (d) SEM shows that an oxide nanosheet structure is formed on the surface of silicon oxide. Figure 3 It can be seen that the loading amounts of N, Se, and P are 15.34 mg / g, 183.58 mg / g, and 72.94 mg / g, respectively. Figure 4-6 As shown, under static water conditions, 63.46% of N and 58.49% of Se were released within 120 h, while 43.57% of P was released within 240 h, showing excellent sustained release performance.

[0054] Example 5

[0055] A method for preparing a slow-release fertilizer based on a layered magnesium-aluminum bimetallic oxide-silicon oxide composite material derived from magnesium-aluminum silicate minerals, wherein the preparation process is as follows: Figure 1 As shown:

[0056] In this embodiment, vermiculite is used as the source of Mg, Al and silicon oxide, and the contents of Mg, Al and Si are 13.2%, 6.51% and 15.86% respectively.

[0057] After the vermiculite is ground into powder, it is calcined at 900°C for 1.5h. The calcined vermiculite is added to a 1mol / L sulfuric acid solution at a solid-liquid ratio of 1:20, and stirred and leached at 60°C for 3h to obtain a solid-liquid mixture with a magnesium ion concentration of about 6.1g / L and an aluminum ion concentration of about 3.0g / L, and a magnesium-aluminum molar ratio of about 2.3:1; 0.2mol / L of sodium carbonate and 2.0mol / L of sodium hydroxide mixed solution are slowly added to the above mixture to adjust the pH to 9.0; then the solid-liquid mixture is hydrothermally synthesized at 60°C for 36h to prepare magnesium-aluminum hydrotalcite-oxygen Silicon composite material (vermiculite LDH@Si); after solid-liquid separation and drying of the prepared vermiculite LDH@Si, calcined at 650°C for 0.5h to obtain a layered magnesium aluminum bimetallic oxide-silicon oxide composite material (vermiculite LDO@Si); vermiculite LDO@Si was added to 1g / L potassium nitrate, 3g / L sodium selenite and 5g / L potassium phosphate composite solution at a solid-liquid ratio of 1:100, immersed and adsorbed for 36h and then dried to obtain a layered magnesium aluminum bimetallic oxide-silicon oxide-based composite slow-release fertilizer (CRSF). Figure 2 (e) SEM image shows that an oxide nanosheet structure is formed on the surface of silicon oxide. Figure 3 It can be seen that the loading amounts of N, Se, and P are 8.75 mg / g, 117.91 mg / g, and 58.26 mg / g, respectively. Figure 4-6 As shown, under static water conditions, 70.89% of N and 69.10% of Se were released within 120 h, while 66.32% of P was released within 240 h, showing excellent sustained release performance.

[0058] Example 6

[0059] A method for preparing a slow-release fertilizer based on a layered magnesium-aluminum bimetallic oxide-silicon oxide composite material derived from magnesium-aluminum silicate minerals, wherein the preparation process is as follows: Figure 1 As shown:

[0060] In this embodiment, chlorite is used as the source of Mg, Al and silicon oxide, and the contents of Mg, Al and Si are 18.32%, 6.87% and 18.78% respectively.

[0061] After the chlorite is ground into powder, it is calcined at 1000°C for 0.5h. The calcined chlorite is added to a 1mol / L sulfuric acid solution at a solid-liquid ratio of 1:20, and stirred and leached at 60°C for 2h to obtain a solid-liquid mixture with a magnesium ion concentration of about 8.6g / L and an aluminum ion concentration of about 3.2g / L, and a magnesium-aluminum molar ratio of about 3:1; 0.2moL / L of sodium carbonate and 2.0mol / L of sodium hydroxide mixed solution are slowly added to the above mixture to adjust the pH to 11.0; then the solid-liquid mixture is hydrothermally synthesized at 80°C for 48h to prepare magnesium-aluminum hydrotalcite-silicon oxide. Composite material (chlorite LDH@Si); after solid-liquid separation and drying of the prepared chlorite LDH@Si, calcination at 550°C for 1.5h obtains a layered magnesium aluminum bimetallic oxide-silicon oxide composite material (chlorite LDO@Si); chlorite LDO@Si is added to 1g / L potassium nitrate, 3g / L sodium selenite and 5g / L potassium phosphate composite solution at a solid-liquid ratio of 1:100, immersed and adsorbed for 36h and then dried to obtain a layered magnesium aluminum bimetallic oxide-silicon oxide-based composite slow-release fertilizer (CRSF). Figure 2 (f) SEM image shows that an oxide nanosheet structure is formed on the surface of silicon oxide. Figure 3 It can be seen that the loading amounts of N, Se, and P are 6.18 mg / g, 101.88 mg / g, and 52.83 mg / g, respectively. Figure 4-6 As shown, under static water conditions, 68.89% of N and 66.70% of Se were released within 120 h, while 50.49% of P was released within 240 h, showing excellent sustained release performance.

[0062] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by any technician familiar with the art within the technical scope disclosed in the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be based on the protection scope of the claims.

Claims

1. A method for preparing a layered magnesium aluminum bimetallic oxide-silicon oxide composite material derived from a magnesium aluminum silicate mineral, characterized in that: The preparation method comprises the following steps: S1. Grinding a silicate mineral into powder and then calcining it to obtain an activated silicate mineral; wherein the silicate mineral comprises any one or more of a magnesium silicate mineral, an aluminum silicate mineral, and a magnesium aluminum silicate mineral; S2, acid leaching the activated silicate mineral to obtain a solid-liquid mixture A; wherein the solid-liquid mixture comprises insoluble silicon oxide and a leaching solution; S3, based on the ratio of magnesium and aluminum ions in the hydrotalcite, selectively adding soluble magnesium salt and / or aluminum salt to the leachate, and obtaining a solid-liquid mixture B after stirring; wherein the solid-liquid mixture B comprises insoluble silicon oxide and the regulated leachate; S4, adjusting the pH value of the solid-liquid mixture B to 9-11, and then performing a hydrothermal reaction to synthesize a magnesium-aluminum hydrotalcite-silicon oxide composite material; S5. After solid-liquid separation and drying, the magnesium aluminum hydrotalcite-silicon oxide composite material is calcined to obtain a magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material.

2. The method for preparing the magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material according to claim 1, characterized in that: In step S1, the calcination temperature is 600-1000°C, and the calcination time is 0.5-3h.

3. The method for preparing the magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material according to claim 1, characterized in that: In step S1, the magnesium silicate mineral includes any one or more of serpentine, talc, and sepiolite, and the aluminum silicate mineral includes one or more of pyrophyllite, kaolinite, halloysite, illite, and muscovite; the magnesium aluminum silicate mineral includes one or more of montmorillonite, palygorskite, vermiculite, chlorite, rectorite, and phlogopite.

4. The method for preparing the magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material according to claim 1, characterized in that: In step S2, the solid-liquid ratio of the activated silicate mineral to the acid is 1:10-1:60, the acid used for the acid leaching is sulfuric acid or hydrochloric acid, the concentration of the sulfuric acid or hydrochloric acid is 0.5-4.0 mol / L, the leaching temperature of the acid leaching is 30-80°C, and the leaching time of the acid leaching is 0.5-5h.

5. The method for preparing the magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material according to claim 1, characterized in that: In step S3, the molar ratio of magnesium to aluminum ions in the regulated leachate is 2:1-4:1, the concentration of magnesium ions in the regulated leachate is 1-16 g / L, and the concentration of aluminum ions in the regulated leachate is 0.5-8 g / L.

6. The method for preparing the magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material according to claim 1, characterized in that: In step S4, the substance for adjusting the pH value of the solid-liquid mixture B is a mixed solution of sodium carbonate and sodium hydroxide; wherein the concentration of the sodium carbonate is 0.1-0.2 mol / L, and the concentration of the sodium hydroxide is 1.0-2.0 mol / L.

7. The method for preparing the magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material according to claim 1, characterized in that: In step S4, the temperature of the hydrothermal reaction is 40-80° C., and the time of the hydrothermal reaction is 12-48 hours.

8. The method for preparing the magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material according to claim 1, characterized in that: In step S5, the calcination temperature is 400-800°C, and the calcination time is 0.5-3h.

9. A magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material prepared by the preparation method described in any one of claims 1 to 8.

10. An application of a magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material prepared by the preparation method according to any one of claims 1 to 8 or a magnesium aluminum silicate mineral-derived layered magnesium aluminum bimetallic oxide-silicon oxide composite material according to claim 9 in a fertilizer slow release, characterized in that: The fertilizers are specifically layered magnesium aluminum bimetallic oxide-silicon oxide based nitrogen fertilizers, phosphate fertilizers, selenium fertilizers and composite slow-release fertilizers. The preparation method of the layered magnesium aluminum bimetallic oxide-silicon oxide based nitrogen fertilizers, phosphate fertilizers, selenium fertilizers and composite slow-release fertilizers is as follows: the layered magnesium aluminum bimetallic oxide-silicon oxide composite material is added to a single nutrient solution or a composite nutrient solution of nitrogen, phosphorus and selenium, and the mixture is prepared after impregnation, adsorption and drying.

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