Preparation of a suspension concentrate and its use in a light-transmitting balanced liquid fertilizer

Abstract

The prepared suspension agent is a stable colloidal suspension obtained by hydrolysis of methoxy zinc aluminum hydrotalcite, the suspension agent can interact with a large amount of nutrient elements and trace nutrient elements required by crops, and form a stable suspension type liquid fertilizer, in the liquid fertilizer, fertilizer molecules are not easy to aggregate to form crystals and precipitate, and no solid-liquid stratification phenomenon occurs. The liquid fertilizer prepared based on the suspension agent has high light transmittance, does not block light, has strong adhesion to crop leaf surface, and can be used as a foliar fertilizer. The nutrition of the liquid fertilizer can be absorbed by crops in a short time, can effectively improve the chlorophyll content of crop leaves and improve the whole plant quality of crops, and shows that the liquid fertilizer has good effect of promoting the growth of crops. The method for preparing the liquid fertilizer by using the suspension agent is simple, the conditions are mild, and is suitable for practical popularization and application.

Description

Technical fields:

[0001] This invention provides a suspending agent, its preparation method, and its application in a light-transmitting balanced liquid fertilizer, belonging to the field of liquid fertilizer technology. Background technology:

[0002] Liquid fertilizer is an economical and effective fertilizer that has been widely used both domestically and internationally. Currently, liquid fertilizers include two types: clear liquid and suspension. Clear liquid fertilizers generally have lower nutrient content, and their solubility varies significantly with temperature, making production and application inconvenient. Furthermore, they present numerous problems in transportation and storage, limiting their widespread adoption. Suspension liquid fertilizers can contain more nutrients and may include insoluble matter, thus requiring less stringent raw material requirements and resulting in lower costs. However, suspension fertilizers are supersaturated liquids and are unstable. Under the influence of external forces, temperature, pH, etc., the dissolved fertilizer will crystallize, and these crystals will continue to grow, eventually leading to solid-liquid separation and the fertilizer becoming ineffective.

[0003] Foliar fertilizer is a type of fertilizer that applies nutrients in liquid form to the surface of crop leaves, allowing the leaves to absorb the nutrients and exert their effects. Since soil fertilization requires time for nutrients to be absorbed by crops, it cannot promptly alleviate symptoms caused by nutrient deficiencies. Foliar fertilization, on the other hand, allows nutrients to enter the plant through the leaves in a shorter time, quickly addressing nutrient deficiencies. Foliar fertilization promotes rapid nutrient absorption while saving on fertilizer application and reducing soil and water pollution from excessive fertilization—a three-in-one effective fertilization technique. It is important to note that the light transmittance of the liquid foliar fertilizer must be considered to avoid hindering photosynthesis. Using low-transmittance liquid foliar fertilizer will impede photosynthesis; without the energy support of photosynthesis, crops will struggle to absorb nutrients from the foliar fertilizer, resulting in wasted fertilizer and harming crop growth. In addition, the waxy coating on the leaves must be considered when applying liquid foliar fertilizer. This wax makes it difficult for water-based liquid foliar fertilizer to adhere to the crop leaves. Since the absorption of nutrients from the liquid fertilizer by the crop leaves takes time, if the liquid foliar fertilizer has poor adhesion, it may detach from the leaves with rainwater, irrigation water, dew, etc., before the nutrients are fully absorbed, thus losing its intended effect. Reference 1 (CN110590467B) reports a liquid fertilizer containing graphene oxide. This liquid fertilizer uses graphene oxide as the main component of the dispersion. Due to its amphoteric molecular characteristics, graphene oxide can act as a surfactant, reducing the energy between the interfaces of the components in the liquid fertilizer, thus helping to form a uniform suspension system. Furthermore, xanthan gum and chitosan are added to assist in thickening and suspending, further ensuring the stability of the suspension system. However, since Reference 1 uses graphene oxide as a raw material to prepare the liquid fertilizer, and graphene oxide is black and has a strong light-blocking effect, this liquid fertilizer is detrimental to promoting photosynthesis on crop leaves if used as a foliar fertilizer. Furthermore, the graphene oxide, xanthan gum, and chitosan used as suspending agents in Reference 1 do not have high adhesiveness, making it difficult for the liquid fertilizer to adhere to the leaf surface for a long time. This results in a relatively high actual loss rate when the liquid fertilizer is used as a foliar fertilizer. Summary of the Invention:

[0004] To address the problems existing in the prior art, this invention provides a method for preparing a suspending agent and its application in the preparation of a light-transmitting balanced liquid fertilizer.

[0005] The preparation steps of a suspension are as follows:

[0006] (1) Dissolve NaOH in methanol solvent at 45-55℃ to obtain solution A, wherein the weight ratio of NaOH to methanol is 1:(5-7);

[0007] (2) Dissolve zinc nitrate hexahydrate and aluminum nitrate nonahydrate in methanol solvent at room temperature to obtain solution B, wherein the weight ratio of zinc nitrate hexahydrate, aluminum nitrate nonahydrate and methanol is (1.73-2.75):1:(42-48.6);

[0008] (3) Add the solution B obtained in step (2) dropwise to the solution A obtained in step (1) at 45-55℃ and stirring at 2000-5000r / min. The dropwise rate is 1 drop every 2-5 seconds. When the pH of the resulting mixture is 7.5-8.5, the dropwise addition ends. Continue the reaction for 10-24 hours, and then obtain a white mixture C.

[0009] (4) Heat the white mixture C obtained in step (3) to 55-65℃, add sodium unsaturated fatty acid, and then stir at a speed of 1000-3000 r / min for 3-12 h to obtain a white mixture D containing unsaturated fatty acid-zinc aluminum methoxy hydrotalcite, wherein the weight ratio of the white mixture C obtained in step (3) to sodium unsaturated fatty acid is (6-15):(0.28-0.58);

[0010] (5) Filter the mixture D containing unsaturated fatty acid-zinc-aluminum hydrotalcite obtained in step (4) at room temperature. Wash the filtered gel with methanol solvent 3-5 times to obtain white unsaturated fatty acid-zinc-aluminum hydrotalcite gel E, wherein the weight ratio of mixture D to methanol solvent is 1:3.

[0011] (6) Sodium stearate and polyvinyl alcohol are mixed in water at 30-45℃, with a mass ratio of sodium stearate, polyvinyl alcohol and water of 1:(1.5~3):(80~120). The mixture is stirred at 500-1500r / min for 0.5-3h and then cooled to room temperature to obtain solution F.

[0012] (7) At 18-35℃ and under stirring conditions, the unsaturated fatty acid-methoxy zinc aluminum hydrotalcite gel E obtained in step (5) is added to the solution F obtained in step (6). The stirring speed is 500-3500 r / min. After stirring for 2-12 h, a colloidal suspension G containing stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite is obtained. The colloidal suspension G is a suspending agent. The weight ratio of solution F to gel E is (1-3):1.

[0013] Another object of the present invention is to apply the above-mentioned suspending agent to the preparation of a light-transmitting balanced liquid fertilizer, characterized in that the raw materials used in the preparation method include: the suspending agent described in steps (1)-(7) above, macro-elements and micro-elements, and the preparation steps are as follows:

[0014] Add macro- and micro-elements to the colloidal suspension G (or suspending agent) obtained in step (7) at room temperature and stir for 0.2-1.5 h at a stirring speed of 100 r / min-300 r / min. Then add water and continue stirring at the same stirring speed for 0.5 h to obtain a high-transmittance balanced liquid fertilizer, which includes the following components and their mass fractions: colloidal suspension G (or suspending agent) 0.8-1.5 parts, macro-elements 66-85 parts, micro-elements 2-2.7 parts, and water 11.5-30 parts.

[0015] The macroelements are one or a mixture of more than one of urea, urea ammonium nitrate solution, liquid phosphoric acid, ammonium polyphosphate solution, dipotassium hydrogen phosphate, potassium pyrophosphate, and potassium acetate; the microelements are one or a mixture of more than one of EDTA-Fe-13, EDTA-Mn-13, EDTA-Cu-15, EDTA-Zn-15, boric acid, and disodium octaborate tetrahydrate.

[0016] The water used in the above preparation methods is all deionized water.

[0017] The present invention differs from the prior art in that it achieves the following technical effects:

[0018] The experimental results of the efficacy examples demonstrate that the suspension prepared by this invention can interact with the macro- and micro-elements required by crops to form a stable suspension, making it difficult for fertilizer molecules to aggregate and form crystals, thus preventing solid-liquid stratification. The liquid fertilizer preparation method based on the suspension of this invention is simple and suitable for practical promotion and application. The liquid fertilizer prepared by this invention has high light transmittance, does not block light, and has strong adhesion to crop leaves, making it suitable for use as a foliar fertilizer. Crops can quickly absorb the nutrients from this foliar fertilizer, thereby increasing the chlorophyll content of crop leaves and improving the overall quality of the crop, demonstrating that the liquid fertilizer of this invention can positively promote healthy crop growth. The above technical effects are due to the following working principle:

[0019] In the preparation steps of the suspending agent, steps (1)-(3) involve preparing a mixture C of methoxy zinc aluminum hydrotalcite compounds in methanol solvent using zinc nitrate hexahydrate and aluminum nitrate nonahydrate as raw materials. The classic hydrotalcite is magnesium aluminum carbonate type hydrotalcite, whose structure is very similar to the layered structure of brucite [Mg(OH)2]. The hydrotalcite layers are formed by MgO6 octahedra sharing common edges to form unit layers, with MgO6 on the layers... 2+ Can be used by Al within a certain range 3+ Isomorphic substitution causes the layers to carry a positive charge, and the CO3 between the layers... 2-The positive charge balance on the layers makes the overall structure of magnesium aluminum carbonate root-type hydrotalcite electrically neutral. If the magnesium in magnesium aluminum hydrotalcite is replaced by zinc, it becomes zinc aluminum hydrotalcite. Zinc is introduced because zinc can indirectly affect the synthesis of auxin in crops. When crops are deficient in zinc, the auxin content in the stems and buds of the crops decreases, growth is stagnant, and the plants are stunted. At the same time, zinc is also an activator of many enzymes and has a wide range of effects on the carbon and nitrogen metabolism of plants. Therefore, supplementing zinc helps the photosynthesis of crops. Zinc can also enhance the stress resistance of plants, increase the weight of grains, and change the ratio of grains to stems. In steps (1)-(3) of the present invention, methanol molecules in the reaction system react with the metal hydroxyl groups (M-OH) on the zinc aluminum hydrotalcite layers under the action of sodium hydroxide to form M-OCH3 groups. NO is present between the layers. 3- Anions are used to balance the positive charge on the hydrotalcite layers.

[0020] In steps (4) and (5) of the preparation of the suspending agent, the methoxy zinc aluminum hydrotalcite prepared in steps (1)-(3) undergoes an interlayer ion exchange reaction with sodium unsaturated fatty acids under stirring conditions, that is, the unsaturated fatty acid anions replace the NO between the layers of the methoxy zinc aluminum hydrotalcite. 3- Anions enter the interlayer space, yielding a mixed solution D containing intercalated unsaturated fatty acid-methoxy zinc-aluminum hydrotalcite. Solution D is then washed and filtered with methanol to obtain an unsaturated fatty acid-methoxy zinc-aluminum hydrotalcite gel E. Sodium unsaturated fatty acids dissolve in water and ionize to release unsaturated fatty acid anions. These anions are characterized by a carboxyl group at one end and an aliphatic hydrocarbon chain at the other. The presence of intercalated unsaturated fatty acid anions increases the distance between the zinc-aluminum inorganic layers and expands the intercalation space, weakening the interactions between the inorganic layers. This facilitates ion exchange reactions between other anions and the intercalated unsaturated fatty acid anions, leading to the formation of new intercalated hydrotalcite compounds.

[0021] In the preparation step (6) of the suspending agent, sodium stearate dissolves in water and ionizes into negatively charged stearate anions. The carboxyl stearate and the hydroxyl polyvinyl alcohol molecules can form hydrogen bonds in the aqueous solution to generate a negatively charged stearic acid / polyvinyl alcohol supramolecular complex. The free sodium ions in the solution balance the charge of the supramolecular complex.

[0022] In the preparation step (7) of the suspending agent, while the unsaturated fatty acid-zinc-aluminum hydrotalcite gel E comes into contact with water and undergoes a hydrolysis reaction, it also undergoes an interlayer ion exchange reaction with the negatively charged stearic acid / polyvinyl alcohol supramolecular complex. The M-OCH3 group in the unsaturated fatty acid-zinc-aluminum hydrotalcite gel readily hydrolyzes in water to generate M-OH. This hydrolysis reaction is relatively rapid and vigorous, and the energy released by the reaction can instantly break down the gel into very small colloidal particles. The generated tiny colloidal particles can be stably suspended in the aqueous solution. Furthermore, during the hydrolysis reaction of unsaturated fatty acid-methoxy zinc aluminum layered double hydroxides (LDHs), when methanol molecules formed by the hydrolysis of the M-OCH3 groups detach from the inorganic layers, the interaction between the inorganic layers of the zinc aluminum LDHs is further weakened. This facilitates interlayer ion exchange between the negatively charged stearic acid / polyvinyl alcohol supramolecular complex and the stearate ions between the inorganic layers of the zinc aluminum LDHs, generating a stearic acid / polyvinyl alcohol-zinc aluminum LDH interlayer complex. The unsaturated fatty acid ions exchanged from the inorganic layers of the zinc aluminum LDHs become free ions in the solution, while some unsaturated fatty acid ions are adsorbed on the outer surface of the inorganic layers of the zinc aluminum LDHs through electrostatic attraction. The unsaturated fatty acid ions have a certain emulsifying effect, which helps the stearic acid / polyvinyl alcohol-zinc aluminum LDH interlayer complex to suspend in the aqueous solution. Because the waxy substance on crop leaves is mainly composed of fatty acids, the alkyl chains of fatty acids on the surface of the stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite layered intercalation complex can combine with the alkyl chains of fatty acids in the leaf wax through hydrophobic interactions. This allows the stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite layered intercalation complex to adhere to the crop leaves. In addition, the free unsaturated fatty acids and stearic acid molecules in the suspension concentrate, which have surfactant functions, also reduce the surface tension of the foliar fertilizer liquid and decrease the contractile force of the liquid. This makes it easier for the liquid fertilizer to spread on the leaf surface, thereby better wetting the leaf surface and achieving a good foliar fertilization effect.

[0023] In the above-mentioned application of the suspending agent to the preparation of light-transmitting balanced liquid fertilizer, the suspending agent obtained in step (7) is used. The effective component in the suspending agent is stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite intercalated organic-inorganic complex. Due to the long polyvinyl alcohol chain, it is not completely embedded in the zinc aluminum hydrotalcite inorganic layers. Instead, some polyvinyl alcohol molecular chains are embedded in the layers, while other polyvinyl alcohol molecular chains are suspended outside the hydrotalcite layers. The hydroxyl groups on the polyethanol chains suspended outside the inorganic layers can interact with polar groups (such as phosphate, carbonyl, carboxyl, and amino groups) of fertilizer molecules, or with polar groups carried by organic ligands of metal ions in fertilizer molecules, or with hydroxyl groups on fertilizer hydrates, or with metal ions in some fertilizer molecules to form supramolecular interactions such as hydrogen bonds and coordination bonds. This allows these fertilizer molecules to be adsorbed and encapsulated in a three-dimensional network composed of polyvinyl alcohol chains and zinc-aluminum hydrotalcite inorganic layers of the intercalated complex, ensuring stable suspension of these fertilizer molecules or compounds in the solution. When fertilizer molecules interact with the stearic acid / polyvinyl alcohol-zinc-aluminum hydrotalcite intercalated complex in the suspending agent at the molecular level, these fertilizer molecules are less likely to aggregate and precipitate, thus preventing solid-liquid stratification. When the stearic acid / polyvinyl alcohol-zinc-aluminum hydrotalcite intercalated organic-inorganic complex adheres to the leaf surface, the fertilizer molecules adsorbed and encapsulated on the intercalated organic-inorganic complex network can also simultaneously and stably adhere to the leaf surface. Due to the barrier effect of the polymer chains and inorganic layers in the stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite layered composite, the dissolution rate of these nutrients will also be reduced, which in turn will reduce the loss rate of these nutrients with rainwater and irrigation water. Attached Figure Description

[0024] The accompanying drawings are provided to further illustrate the invention and form part of the specification. They are used together with the following detailed description to explain the invention, but do not constitute a limitation thereof.

[0025] Figure 1 In the diagram, a represents the zinc-aluminum hydrotalcite prepared in Comparative Example 6 of this invention, b represents the methoxy zinc-aluminum hydrotalcite prepared in Example 3, c represents the fatty acid-methoxy zinc-aluminum hydrotalcite, and d represents the X-ray powder diffraction pattern of stearic acid / polyvinyl alcohol-zinc-aluminum hydrotalcite.

[0026] Figure 2 This is a process flow diagram of the preparation process of a suspending agent according to the present invention.

[0027] Figure 3 This is a process flow diagram of the preparation process of a light-transmitting balanced liquid fertilizer according to the present invention. Detailed Implementation

[0028] The above-mentioned and other technical features and advantages of the present invention will be described in more detail below with reference to the embodiments. Unless otherwise specified, all chemical raw materials used in the following embodiments are commercially available, chemically pure reagents; additionally, sodium unsaturated fatty acid, CAS number 67701-11-5, was purchased from Aladdin Biochemical Technology Co., Ltd.; sodium stearate, analytical grade, was purchased from Tianjin Huafuer Chemical Co., Ltd.; polyvinyl alcohol, model PVA2488, viscosity 45-55 mPa·s, was purchased from Shanghai Yingjia Industrial Development Co., Ltd.; and deionized water was used.

[0029] Example 1

[0030] The preparation steps of a suspension are as follows:

[0031] (1) Dissolve NaOH in methanol solvent at 45℃ to obtain solution A, wherein the weight ratio of NaOH to methanol is 1:5;

[0032] (2) Zinc nitrate hexahydrate and aluminum nitrate nonahydrate are dissolved in methanol at room temperature to obtain solution B, wherein the weight ratio of zinc nitrate hexahydrate, aluminum nitrate nonahydrate and methanol is 1.73:1:42.

[0033] (3) The solution B obtained in step (2) is added dropwise to the solution A obtained in step (1) at 45°C and with a stirring speed of 2000 r / min. The dropwise rate is 1 drop every 2 seconds. When the pH of the resulting mixture is 7.5, the dropwise addition is stopped. The reaction continues for 10 h, and then a white mixture C is obtained.

[0034] (4) Heat the white mixture C obtained in step (3) to 55°C, add sodium unsaturated fatty acid, and then stir at a speed of 1000 r / min for 3 h to obtain a white mixture D containing unsaturated fatty acid-zinc aluminum methoxy hydrotalcite, wherein the weight ratio of the white mixture C obtained in step (3) to sodium unsaturated fatty acid is 6:0.28.

[0035] (5) Filter the mixture D containing unsaturated fatty acid-zinc-aluminum hydrotalcite obtained in step (4) at room temperature. Wash the filtered gel with methanol solvent three times to obtain white unsaturated fatty acid-zinc-aluminum hydrotalcite gel E, wherein the weight ratio of mixture D to methanol solvent is 1:3.

[0036] (6) Sodium stearate and polyvinyl alcohol were mixed in water at 30°C. The mass ratio of sodium stearate, polyvinyl alcohol and water was 1:1.5:80. The mixture was stirred at 500 r / min for 0.5 h. After cooling to room temperature, solution F was obtained.

[0037] (7) The unsaturated fatty acid-methoxy zinc aluminum hydrotalcite gel E obtained in step (5) is added to the solution F obtained in step (6) at 18℃ and under stirring conditions. The stirring speed is 500r / min. After stirring for 2h, a colloidal suspension G containing stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite is obtained. The colloidal suspension G is a suspending agent. The weight ratio of solution F to gel E is 1:1.

[0038] Example 2

[0039] The preparation steps of a suspension are as follows:

[0040] (1) Dissolve NaOH in methanol solvent at 48℃ to obtain solution A, wherein the weight ratio of NaOH to methanol is 1:5.5;

[0041] (2) Zinc nitrate hexahydrate and aluminum nitrate nonahydrate are dissolved in methanol at room temperature to obtain solution B, wherein the weight ratio of zinc nitrate hexahydrate, aluminum nitrate nonahydrate and methanol is 1.99:1:43.5.

[0042] (3) The solution B obtained in step (2) is added dropwise to the solution A obtained in step (1) at 48°C and stirring at 2750 r / min. The dropwise rate is 1 drop every 2 seconds. The dropwise addition ends when the pH of the resulting mixture is 7.7. The reaction continues for 13 hours, and then a white mixture C is obtained.

[0043] (4) Heat the white mixture C obtained in step (3) to 57°C, add sodium unsaturated fatty acid, and then stir at a stirring speed of 1500 r / min for 6 h to obtain a white mixture D containing unsaturated fatty acid-zinc aluminum methoxy hydrotalcite, wherein the weight ratio of the white mixture C obtained in step (3) to sodium unsaturated fatty acid is 8:0.36.

[0044] (5) Filter the mixture D containing unsaturated fatty acid-zinc-aluminum hydrotalcite obtained in step (4) at room temperature. Wash the filtered gel with methanol solvent three times to obtain white unsaturated fatty acid-zinc-aluminum hydrotalcite gel E, wherein the weight ratio of mixture D to methanol solvent is 1:3.

[0045] (6) Sodium stearate and polyvinyl alcohol were mixed in water at 34°C. The mass ratio of sodium stearate, polyvinyl alcohol and water was 1:1.9:90. The mixture was stirred at 750 r / min for 1.2 h. After cooling to room temperature, solution F was obtained.

[0046] (7) At 23°C and under stirring conditions, the unsaturated fatty acid-methoxy zinc aluminum hydrotalcite gel E obtained in step (5) is added to the solution F obtained in step (6). The stirring speed is 1250 r / min. After stirring for 5 h, a colloidal suspension G containing stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite is obtained. The colloidal suspension G is a suspending agent. The weight ratio of the solution F to the gel E is 1.5:1.

[0047] Example 3

[0048] The preparation steps of a suspension are as follows:

[0049] (1) Dissolve NaOH in methanol solvent at 50℃ to obtain solution A, wherein the weight ratio of NaOH to methanol is 1:6;

[0050] (2) Zinc nitrate hexahydrate and aluminum nitrate nonahydrate are dissolved in methanol at room temperature to obtain solution B, wherein the weight ratio of zinc nitrate hexahydrate, aluminum nitrate nonahydrate and methanol is 2.25:1:45;

[0051] (3) The solution B obtained in step (2) is added dropwise to the solution A obtained in step (1) at 50°C and stirring at 3500 r / min. The dropwise rate is 1 drop every 3 seconds. When the pH of the resulting mixture is 8.0, the dropwise addition ends. The reaction continues for 17 h, and then a white mixture C is obtained.

[0052] (4) Heat the white mixture C obtained in step (3) to 60°C, add sodium unsaturated fatty acid, and then stir at a stirring speed of 2000 r / min for 8 h to obtain a white mixture D containing unsaturated fatty acid-zinc aluminum methoxy hydrotalcite, wherein the weight ratio of the white mixture C obtained in step (3) to sodium unsaturated fatty acid is 11:0.43.

[0053] (5) Filter the mixture D containing unsaturated fatty acid-zinc-aluminum hydrotalcite obtained in step (4) at room temperature. Wash the filtered gel with methanol solvent four times to obtain white unsaturated fatty acid-zinc-aluminum hydrotalcite gel E, wherein the weight ratio of mixture D to methanol solvent is 1:3.

[0054] (6) Sodium stearate and polyvinyl alcohol were mixed in water at 38°C. The mass ratio of sodium stearate, polyvinyl alcohol and water was 1:2.3:100. The mixture was stirred at 1000 r / min for 1.8 h. After cooling to room temperature, solution F was obtained.

[0055] (7) At 27°C and under stirring conditions, the unsaturated fatty acid-methoxy zinc aluminum hydrotalcite gel E obtained in step (5) is added to the solution F obtained in step (6). The stirring speed is 2000 r / min. After stirring for 7 h, a colloidal suspension G containing stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite is obtained. The colloidal suspension G is a suspending agent. The weight ratio of solution F to gel E is 2:1.

[0056] Example 4

[0057] The preparation steps of a suspension are as follows:

[0058] (1) Dissolve NaOH in methanol solvent at 53℃ to obtain solution A, wherein the weight ratio of NaOH to methanol is 1:6.5;

[0059] (2) Zinc nitrate hexahydrate and aluminum nitrate nonahydrate are dissolved in methanol at room temperature to obtain solution B, wherein the weight ratio of zinc nitrate hexahydrate, aluminum nitrate nonahydrate and methanol is 2.5:1:47.

[0060] (3) The solution B obtained in step (2) is added dropwise to the solution A obtained in step (1) at 53°C and stirring at 4250 r / min. The dropwise rate is 1 drop every 4 seconds. When the pH of the resulting mixture is 8.3, the dropwise addition ends. The reaction continues for 21 h, and then a white mixture C is obtained.

[0061] (4) Heat the white mixture C obtained in step (3) to 62°C, add sodium unsaturated fatty acid, and then stir at a stirring speed of 2500 r / min for 10 h to obtain a white mixture D containing unsaturated fatty acid-zinc aluminum methoxy hydrotalcite, wherein the weight ratio of the white mixture C obtained in step (3) to sodium unsaturated fatty acid is 13:0.5.

[0062] (5) Filter the mixture D containing unsaturated fatty acid-zinc-aluminum hydrotalcite obtained in step (4) at room temperature. Wash the filtered gel with methanol solvent four times to obtain white unsaturated fatty acid-zinc-aluminum hydrotalcite gel E, wherein the weight ratio of mixture D to methanol solvent is 1:3.

[0063] (6) Sodium stearate and polyvinyl alcohol were mixed in water at 42°C. The mass ratio of sodium stearate, polyvinyl alcohol and water was 1:2:110. The mixture was stirred at 1250 r / min for 2.4 h. After cooling to room temperature, solution F was obtained.

[0064] (7) The unsaturated fatty acid-methoxy zinc aluminum hydrotalcite gel E obtained in step (5) was added to the solution F obtained in step (6) at 31℃ and under stirring conditions. The stirring speed was 2750 r / min. After stirring for 10 h, a colloidal suspension G containing stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite was obtained. The colloidal suspension G is a suspending agent. The weight ratio of solution F to gel E is 2.5:1.

[0065] Example 5

[0066] The preparation steps of a suspension are as follows:

[0067] (1) Dissolve NaOH in methanol solvent at 55℃ to obtain solution A, wherein the weight ratio of NaOH to methanol is 1:7;

[0068] (2) Zinc nitrate hexahydrate and aluminum nitrate nonahydrate are dissolved in methanol at room temperature to obtain solution B, wherein the weight ratio of zinc nitrate hexahydrate, aluminum nitrate nonahydrate and methanol is 2.75:1:48.6.

[0069] (3) The solution B obtained in step (2) is added dropwise to the solution A obtained in step (1) at 55°C and stirring at 5000 r / min. The dropwise rate is 1 drop every 5 seconds. When the pH of the resulting mixture is 8.5, the dropwise addition is stopped. The reaction continues for 24 hours, and then a white mixture C is obtained.

[0070] (4) Heat the white mixture C obtained in step (3) to 65°C, add sodium unsaturated fatty acid, and then stir at a stirring speed of 3000 r / min for 12 h to obtain a white mixture D containing unsaturated fatty acid-zinc aluminum methoxy hydrotalcite, wherein the weight ratio of the white mixture C obtained in step (3) to sodium unsaturated fatty acid is 15:0.58.

[0071] (5) Filter the mixture D containing unsaturated fatty acid-zinc-aluminum hydrotalcite obtained in step (4) at room temperature. Wash the filtered gel with methanol solvent repeatedly 5 times to obtain white unsaturated fatty acid-zinc-aluminum hydrotalcite gel E, wherein the weight ratio of mixture D to methanol solvent is 1:3.

[0072] (6) Sodium stearate and polyvinyl alcohol were mixed in water at 45°C. The mass ratio of sodium stearate, polyvinyl alcohol and water was 1:3:120. The mixture was stirred at 1500 r / min for 3 h and then cooled to room temperature to obtain solution F.

[0073] (7) The unsaturated fatty acid-methoxy zinc aluminum hydrotalcite gel E obtained in step (5) is added to the solution F obtained in step (6) under stirring conditions at 35℃ and stirring speed of 3500r / min. After stirring for 12h, a colloidal suspension G containing stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite is obtained. The colloidal suspension G is a suspending agent. The weight ratio of solution F to gel E is 3:1.

[0074] Comparative Example 6

[0075] The difference between this embodiment and Example 3 is that in this embodiment, methanol solvent is not used in steps (1)-(5), but deionized water is used instead of methanol, and the amount of water is the same as that of methanol. The other preparation steps and reagent amounts are the same as in Example 3. The specific preparation steps are as follows:

[0076] (1) Dissolve NaOH in an aqueous solvent at 50℃ to obtain solution A, wherein the weight ratio of NaOH to water is 1:6;

[0077] (2) Dissolve zinc nitrate hexahydrate and aluminum nitrate nonahydrate in an aqueous solvent at room temperature to obtain solution B, wherein the weight ratio of zinc nitrate hexahydrate, aluminum nitrate nonahydrate and water is 2.25:1:45;

[0078] (3) The solution B obtained in step (2) is added dropwise to the solution A obtained in step (1) at 50°C and stirring at 3500 r / min. The dropwise rate is 1 drop every 3 seconds. When the pH of the resulting mixture is 8.0, the dropwise addition ends. The reaction continues for 17 h, and then a white mixture C is obtained.

[0079] (4) Heat the white mixture C obtained in step (3) to 60°C, add sodium unsaturated fatty acid, and then stir at a stirring speed of 2000 r / min for 8 h to obtain white mixture D. The weight ratio of white mixture C obtained in step (3) to sodium unsaturated fatty acid is 11:0.43.

[0080] (5) Filter the mixture D obtained in step (4) at room temperature, wash the filtered gel with water solvent 4 times to obtain white gel E, wherein the weight ratio of mixture D to water solvent is 1:3.

[0081] Steps (6) and (7) in this embodiment are the same as steps (6) and (7) in embodiment (3).

[0082] The white mixture C obtained in this example was filtered and washed three times with 50 ml of water. The precipitate after washing was dried to constant weight in a vacuum drying oven at 60°C to obtain dried zinc-aluminum hydrotalcite. In addition, in Example 3, the mixture C obtained in step (3) was filtered, washed with methanol solvent, and vacuum dried to obtain methoxy zinc-aluminum hydrotalcite. The colloidal substance E obtained in step (5) was vacuum dried to obtain unsaturated fatty acid-methoxy zinc-aluminum hydrotalcite. The colloidal suspension G obtained in step (7) was filtered, washed with deionized water, and vacuum dried to obtain stearic acid / polyvinyl alcohol-zinc-aluminum hydrotalcite. The samples obtained above were ground into powder and then subjected to X-ray powder diffraction characterization test (X-ray powder diffraction was performed on a Rigaku D / MAX X-ray diffractometer, CuKα). (Pipe voltage 40.0 kV, pipe current 30.0 mA), test results are attached. Figure 1 As shown.

[0083] Appendix Figure 1 The image shows X-ray powder diffraction patterns of the zinc-aluminum hydrotalcite prepared in step (3) of Comparative Example 6 and the methoxy zinc-aluminum hydrotalcite, unsaturated fatty acid-methoxy zinc-aluminum hydrotalcite, and stearic acid / polyvinyl alcohol-zinc-aluminum hydrotalcite prepared in Example 3 of this invention. Compared to the zinc-aluminum hydrotalcite, the first diffraction peak of the methoxy zinc-aluminum hydrotalcite shifts towards the small-angle diffraction direction. This is because in Example 3, the zinc-aluminum hydrotalcite was prepared in methanol solvent, and the methoxy groups in methanol were grafted onto the layers of the zinc-aluminum hydrotalcite, leading to an increase in the interlayer spacing. Compared to the methoxy zinc-aluminum hydrotalcite, the first diffraction peak of the unsaturated fatty acid-methoxy zinc-aluminum hydrotalcite shifts towards the small-angle diffraction direction. This is because negatively charged unsaturated fatty acid ions are embedded into the positively charged interlayer spaces of the zinc-aluminum hydrotalcite, further increasing the interlayer spacing. Compared to unsaturated fatty acid-methoxy zinc-aluminum hydrotalcite, the diffraction peak shape of stearic acid / polyvinyl alcohol-zinc-aluminum hydrotalcite changed and the position of the first diffraction peak shifted. This is because the negatively charged stearic acid / polyvinyl alcohol supramolecular complex replaced the unsaturated fatty acid ions and entered the inorganic interlayer. At the same time, the methoxy groups grafted onto the inorganic interlayer were also removed from the interlayer surface during the hydrolysis reaction. The interlayer structure of stearic acid / polyvinyl alcohol-zinc-aluminum hydrotalcite changed compared to that of unsaturated fatty acid-methoxy zinc-aluminum hydrotalcite.

[0084] Comparative Example 7

[0085] The difference between this embodiment and Example 3 is that step (4) is omitted. Instead, in step (5), the white mixture C obtained in step (3) is used instead of mixture D for filtration, and the filtered gel-like substance E is washed four times with methanol. That is, the reaction between sodium unsaturated fatty acids and zinc aluminum methoxy hydrotalcite is not carried out, and unsaturated fatty acids-zinc aluminum methoxy hydrotalcite is not used in the preparation steps. The other preparation steps and reagent dosages are the same as in Example 3.

[0086] Comparative Example 8

[0087] The difference between this embodiment and Example 3 is that this embodiment does not use the stearic acid / polyvinyl alcohol supramolecular complex. That is, this embodiment does not have step (6), and in step (7) this embodiment, deionized water is used instead of solution F. The other preparation steps and reagent amounts are the same as in Example 3. Step (7) of this embodiment is as follows: under the conditions of 27°C and stirring, the gel E obtained in step (5) is added to deionized water, the stirring speed is 2000 r / min, and after stirring for 7 h, a colloidal suspension is obtained, wherein the weight ratio of deionized water to gel E is 2:1.

[0088] Comparative Example 9

[0089] The difference between this embodiment and Example 3 is that the weight ratio of solution F to gel E in step (7) of this embodiment is 2:0.8, which is not within the scope of claims (1-3):1, meaning that the amount of unsaturated fatty acid-methoxy zinc aluminum hydrotalcite gel E is relatively small. The other preparation steps and reagent amounts are the same as in Example 3.

[0090] Comparative Example 10

[0091] The difference between this embodiment and Embodiment 3 is that the weight ratio of zinc nitrate hexahydrate, aluminum nitrate nonahydrate, and methanol in step (2) of this embodiment is 2.25:0.8:45, which is outside the range of (1.73-2.75):1:(42-48.6) in the claims, meaning the amount of aluminum nitrate nonahydrate used is smaller. The other preparation steps and reagent amounts are the same as in Embodiment 3.

[0092] Application Example 11

[0093] In this embodiment, the suspensions or samples prepared in Examples 1-5 and Comparative Examples 6-10 are used to prepare a light-transmitting balanced liquid fertilizer according to the following steps:

[0094] At room temperature, macro-elements and micro-elements were added to the aforementioned colloidal suspension G or suspending agent and stirred for 0.9 h at a stirring speed of 200 r / min. Then water was added and stirring was continued at the same stirring speed for 0.5 h to obtain a high-transmittance balanced liquid fertilizer, which includes the following components and their mass fractions: 1.3 parts of colloidal suspension G, 66 parts of macro-elements, 2.7 parts of micro-elements, and 30 parts of water.

[0095] The mass fractions of macroelements are as follows: 12 parts of ammonium urea nitrate, 9 parts of ammonium polyphosphate, 20 parts of urea, and 25 parts of potassium pyrophosphate; the mass fractions of microelements are as follows: 1 part of disodium tetraborate tetrahydrate, 0.7 parts of EDTA-Fe-13, 0.5 parts of EDTA-Mn-13, and 0.5 parts of EDTA-Zn-15.

[0096] The product has been tested and is classified as a 200-200-200+TE balanced suspension liquid fertilizer.

[0097] Application Example 12

[0098] The light-transmitting balanced liquid fertilizer was prepared using the suspension prepared in Example 3 and following similar preparation steps as described in Application Example 11. The specific steps are as follows:

[0099] At room temperature, macro-elements and micro-elements were added to the colloidal suspension G or suspending agent of Example 3 and stirred for 0.2 h at a stirring speed of 100 r / min. Then water was added and stirring was continued at the same stirring speed for 0.5 h to obtain a high-transmittance balanced liquid fertilizer, which includes the following components and their mass fractions: 0.8 parts of colloidal suspension G, 76 parts of macro-elements, 2 parts of micro-elements, and 21.2 parts of water.

[0100] The mass fractions of macroelements are as follows: ammonium polyphosphate 32 parts, urea 17 parts, dipotassium hydrogen phosphate 3 parts, and potassium acetate 24 parts; the mass fractions of microelements are as follows: disodium octaborate tetrahydrate 0.5 parts, EDTA-Cu-15 0.5 parts, EDTA-Mn-13 0.5 parts, and EDTA-Zn-15 0.5 parts.

[0101] The product has been tested and is classified as a 180-180-180+TE balanced suspension liquid fertilizer.

[0102] Application Example 13

[0103] A light-transmitting balanced liquid fertilizer was prepared using the suspension prepared in Example 3 and following a similar preparation procedure as described in Application Example 11. The specific steps are as follows:

[0104] At room temperature, macro-elements and micro-elements were added to the colloidal suspension G or suspending agent of Example 3 and stirred for 1.5 h at a stirring speed of 300 r / min. Then water was added and stirring was continued at the same stirring speed for 0.5 h to obtain a high-transmittance balanced liquid fertilizer, which includes the following components and their mass fractions: 1.5 parts of colloidal suspension G, 85 parts of macro-elements, 2 parts of micro-elements, and 11.5 parts of water.

[0105] The mass fractions of macroelements are as follows: 15 parts of ammonium urea nitrate, 17 parts of liquid phosphoric acid, 21 parts of urea, 12 parts of dipotassium hydrogen phosphate, and 20 parts of potassium acetate. The mass fractions of microelements are as follows: 0.5 parts of disodium octaborate tetrahydrate, 0.5 parts of EDTA-Cu-15, 0.5 parts of EDTA-Fe-13, and 0.5 parts of EDTA-Zn-15.

[0106] The product has been tested and is classified as a 210-210-210+TE balanced suspension liquid fertilizer.

[0107] Application Example 14

[0108] A light-transmitting balanced liquid fertilizer was prepared using the suspending agent prepared in Example 3 and following similar preparation steps as described in Application Example 11. The difference between this example and Application Example 11 is that the mass fraction of the colloidal suspension G or suspending agent used in this example is 0.6 parts, which is less than the range of 0.8-1.5 parts described in the claims; that is, the amount of suspending agent prepared in Example 3 is relatively small. The other preparation steps and reagent amounts are the same as in Example 11.

[0109] Application Example 15

[0110] This embodiment refers to the method in Reference 1 to prepare liquid fertilizer, that is, using graphene oxide, xanthan gum, and chitosan to replace colloidal suspension G, and mixing it with macro-elements, micro-elements, and water. The specific preparation steps are as follows:

[0111] Water was added to an ultrasonic cleaner. 0.8 parts by weight of graphene oxide were added under ultrasonic power of 180W and temperature of 40℃, and the mixture was ultrasonically dispersed and dissolved at 45 rpm. The dispersion was transferred to a combined stirrer reactor, and the reactor temperature was maintained at 40℃. 0.35 parts by weight of xanthan gum and 0.15 parts by weight of chitosan were added as suspending agents. The stirring speed was controlled at 130 rpm and the shearing speed at 800 rpm for 60 minutes. Then, macro- and micro-elements were added, and the stirring speed was controlled at 160 rpm and the shearing speed at 1000 rpm for 18 minutes of simultaneous stirring and shearing. Heating and stirring were stopped, and the mixture was cooled to obtain a liquid fertilizer product.

[0112] The mass fractions of macroelements are as follows: 12 parts of ammonium urea nitrate, 9 parts of ammonium polyphosphate, 20 parts of urea, and 25 parts of potassium pyrophosphate; the mass fractions of microelements are as follows: 1 part of disodium tetraborate tetrahydrate, 0.7 parts of EDTA-Fe-13, 0.5 parts of EDTA-Mn-13, and 0.5 parts of EDTA-Zn-15.

[0113] The product has been tested and is classified as a 200-200-200+TE balanced suspension liquid fertilizer.

[0114] Effect Example

[0115] 1. Stability tests were conducted on the suspensions obtained in Examples 1-5, the liquid samples obtained in Comparative Examples 6-10, and the liquid fertilizers obtained in Examples 11-15.

[0116] Observe the sample for 30 days to see if crystals precipitate or stratify. If the sample does not stratify into solid and liquid, it indicates that the suspension sample is stable and can proceed to the next test. If solid-liquid stratification occurs, it indicates that the sample is unstable and is not suitable as a suspending agent for liquid fertilizer or for use as liquid fertilizer. The sample will not proceed to the next test stage.

[0117] 2. Perform light transmittance tests on the liquid fertilizers obtained in Application Examples 11-15.

[0118] The liquid samples obtained in each embodiment were placed in quartz cuvettes. Using a Shanghai Lingguang 752Pro UV-Vis spectrophotometer, after baseline zeroing, the instrument's optical path was passed through the quartz cuvettes. The wavelength range was 300–800 nm, and the scanning interval was 5 nm / scan. The average transmittance of the liquid sample = (sum of transmittance per scan) / total number of tests.

[0119] 3. Leaf adhesion tests were conducted on the liquid fertilizers obtained in Application Examples 11-15.

[0120] Several fresh soybean leaves of similar size were collected, and the weight of each leaf was recorded. The weighed leaves were then flattened and pasted parallel to each other on a glass plate, with a 2cm gap between the edges of each leaf. The glass plate was then tilted at a 45-degree angle. The light-transmitting balanced liquid fertilizer prepared from the suspensions obtained in Examples 1, 3, and 5 (Application Example 11) and the liquid fertilizer prepared in Examples 12, 13, and 15 were sprayed onto the corresponding leaves, respectively. The amount of liquid fertilizer sprayed onto each leaf was 1ml. After 30 minutes, each leaf was weighed. The adhesion of the liquid fertilizer to the leaf was evaluated by the leaf weight gain rate. A higher leaf weight gain rate indicates greater adhesion of the liquid sample to the leaf. Leaf weight gain rate = (weight gain of leaf after spraying liquid fertilizer / initial weight of leaf before spraying liquid fertilizer) × 100%.

[0121] 4. The liquid fertilizer obtained in Examples 11-15 was applied to soybean cultivation, using the Hefeng 50 soybean variety, while the control group consisted of water. The specific procedures are as follows:

[0122] A pot experiment was conducted between 2021 and 2022, with each pot (day) containing [data missing]. 底 =6cm,d 顶 Ten soybean seeds of uniform size (h=15cm, h=8cm) were sown under day and night temperatures of (23±0.8℃) and (18±0.6℃), humidity of 55%±5%, 12h light exposure, and light intensity of 1200μmol·m⁻². -2 ·s -1 Soybeans were cultivated in a greenhouse, with 6 seedlings at the true leaf stage and cultivated to the V2 stage. Uniform seedling pots were selected, and foliar spraying was applied to the V2 stage soybean leaves, with 10 ml of the corresponding liquid fertilizer applied to each pot. Three pots were used in parallel for each example treatment. The control group was sprayed with the same volume of water, ensuring even wetting of both sides of the leaves. The chlorophyll content in the soybean leaves and the dry weight of the whole plant biomass were measured after foliar spraying. The specific procedures were as follows: The chlorophyll content of soybean leaves was measured using a chlorophyll meter (SPAD-502) to determine the SPAD value (a dimensionless value representing relative chlorophyll content). The higher the SPAD value, the higher the chlorophyll content. Measurements were taken from 9:30 AM to 11:30 AM, with 6 new leaves randomly selected each time. Each leaf was measured three times, and the average value was taken as the final result. Then, the soil particles adhering to the surface of the entire plant were removed, and the plant was dried at 70℃ to constant weight and weighed.

[0123] 5. As can be seen from Table 1, the suspensions prepared in Examples 1-5 did not exhibit stratification within 30 days, indicating that the suspending agents prepared in Examples 1-5 are stable. In contrast, the liquid sample prepared in Comparative Example 6 showed precipitation, i.e., solid-liquid stratification occurred on day 1. This is because Comparative Example 6 did not use methanol as a solvent, but rather water. The zinc-aluminum hydrotalcite synthesized in the water solvent is a crystalline solid with high crystal order, where inorganic layers are orderly aggregated and stacked together, resulting in large grains. This can be seen from its X-ray powder diffraction pattern (see attached table). Figure 1As confirmed in a), the highly ordered stacking of these inorganic layers of zinc-aluminum hydrotalcite makes it difficult to suspend in solution, instead existing as a precipitate. This ultimately leads to precipitation in the liquid fertilizer prepared from the sample of Comparative Example 6, resulting in solid-liquid stratification. This does not meet the requirements for a suspension-type liquid fertilizer. Therefore, the sample prepared in Comparative Example 6 cannot be used as a liquid fertilizer suspending agent, and it will not be subjected to further testing. The liquid samples prepared in Comparative Examples 7-10 did not exhibit solid-liquid stratification, indicating that the liquid samples prepared in these examples are stable. This is because comparative examples 7-10 used methanol as a solvent during the preparation process. Methanol molecules, under the action of sodium hydroxide, react with the metal hydroxyl groups (M-OH) on the zinc-aluminum hydrotalcite layer to form M-OCH3 groups. When the zinc-aluminum hydrotalcite grafted with -OCH3 groups encounters an aqueous solvent, the M-OCH3 groups on the layer are easily hydrolyzed in water to generate M-OH and release CH3OH molecules. This hydrolysis reaction is rapid and violent, and the energy released by the reaction can instantly depolymerize the zinc-aluminum hydrotalcite layer, and the zinc-aluminum hydrotalcite becomes very small colloidal particles. These tiny colloidal particles can be stably suspended in the aqueous solution without producing solid-liquid stratification.

[0124] As can be seen from Table 2, the suspending agents obtained from Examples 1-5 did not show solid-liquid separation in the liquid fertilizers obtained from Examples 11-13 and the liquid fertilizer containing graphene oxide prepared from Example 15 within 30 days, indicating that these liquid fertilizers are relatively stable.

[0125] Table 2 also shows that the liquid fertilizer prepared from the suspension obtained in Comparative Example 7 exhibited solid-liquid separation on the first day, indicating that the liquid fertilizer sample corresponding to Comparative Example 7 was very unstable. This is because the difference between Comparative Example 7 and Example 3 is that the reaction between sodium unsaturated fatty acids and methoxy zinc aluminum hydrotalcite is not carried out, and unsaturated fatty acids-methoxy zinc aluminum hydrotalcite are not used in the preparation steps. If unsaturated fatty acid ions are embedded between the layers of methoxy zinc aluminum hydrotalcite, the interlayer spacing of the methoxy zinc aluminum hydrotalcite can be increased, reducing the interaction between the layers. This facilitates the subsequent ion exchange reaction between the negatively charged stearic acid / polyvinyl alcohol supramolecular complex and the unsaturated fatty acid ions in the interlayer, allowing the stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite interlayer complex to be embedded within the layers, forming a stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite interlayer complex. This complex can adsorb and encapsulate fertilizer molecules or compounds, which are nutrients, within a network composed of the polyvinyl alcohol chains of the interlayer complex and the inorganic layers of the zinc aluminum hydrotalcite. This achieves the effect of stably suspending these fertilizer molecules or compounds in the solution. When individual fertilizer molecules interact with the stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite interlayer complex in the suspending agent, these fertilizer molecules are less likely to aggregate and precipitate, thus preventing solid-liquid stratification. Comparative Example 7 did not yield an unsaturated fatty acid-methoxy zinc aluminum hydrotalcite layered intercalation complex, and therefore did not prepare a stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite layered intercalation organic-inorganic complex. Consequently, the suspending agent obtained in Comparative Example 7 had poor suspending properties for fertilizer molecules and poor ability to prevent fertilizer molecules from crystallizing into precipitates. Therefore, the liquid sample containing fertilizer molecules corresponding to Comparative Example 7 exhibited solid-liquid stratification and was not suitable for use as a liquid fertilizer.

[0126] The liquid fertilizer prepared from the suspension obtained in Comparative Example 8 exhibited solid-liquid stratification on the third day, indicating that the liquid fertilizer sample corresponding to Comparative Example 8 was highly unstable. This is because the difference between Comparative Example 8 and Example 3 is that the stearic acid / polyvinyl alcohol supramolecular complex was not used. Clearly, Comparative Example 8 did not yield a suspension containing a stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite layered complex. Similar to the reasoning regarding the liquid fertilizer in Comparative Example 7, the suspension obtained in Comparative Example 8 had poor suspending properties for fertilizer molecules and poor ability to prevent fertilizer molecules from crystallizing into precipitates. Therefore, the liquid sample containing fertilizer molecules corresponding to Comparative Example 8 exhibited solid-liquid stratification and was unsuitable for use as a liquid fertilizer.

[0127] The liquid fertilizer suspension prepared from the suspending agent obtained in Comparative Example 9 exhibited solid-liquid stratification on day 18, indicating that the liquid fertilizer sample corresponding to Comparative Example 9 was also unstable. This is because the difference between Comparative Example 9 and Example 3 is that the weight ratio of solution F to colloidal substance E in step (7) of Comparative Example 9 is 2:0.8, which is outside the scope of claims (1-3):1, meaning the amount of unsaturated fatty acid-methoxy zinc aluminum hydrotalcite colloidal substance E is relatively small. This results in insufficient effective content of the stearic acid / polyvinyl alcohol-zinc aluminum hydrotalcite intercalation complex in the suspending agent obtained in Comparative Example 9. Therefore, the sample obtained in Comparative Example 9 has poor suspension properties for fertilizer molecules and poor performance in preventing fertilizer molecules from crystallizing into precipitates. Consequently, the liquid sample containing fertilizer molecules corresponding to Comparative Example 9 eventually exhibited solid-liquid stratification, and therefore it is not suitable for use as a liquid fertilizer.

[0128] The liquid fertilizer suspension prepared from the suspending agent obtained in Comparative Example 10 showed solid-liquid separation on day 23, indicating that the liquid fertilizer sample corresponding to Comparative Example 10 was also unstable. This is because the difference between Comparative Example 10 and Example 3 is that the weight ratio of magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, and methanol in step (2) of Comparative Example 10 is 2.25:0.8:45, which is outside the range of (1.73-2.75):1:(42-48.6) in the claims, meaning that the amount of aluminum nitrate nonahydrate used is too small. This results in an insufficient number of positive charges on the inorganic layers of zinc-aluminum hydrotalcite, which in turn affects the content of stearic acid / polyvinyl alcohol embedded in the interlayer. In other words, the content of stearic acid / polyvinyl alcohol in the interlayer is too low. Therefore, the adsorption of fertilizer molecules by the stearic acid / polyvinyl alcohol-zinc-aluminum hydrotalcite interlayer complex in the suspension obtained in Comparative Example 10 is poor. Consequently, the suspension obtained in Comparative Example 10 has poor suspension properties for fertilizer molecules and poor performance in preventing fertilizer molecules from crystallizing into precipitates. Therefore, the liquid sample containing fertilizer molecules corresponding to Comparative Example 10 also eventually showed solid-liquid stratification and is not suitable for use as a liquid fertilizer.

[0129] The liquid fertilizer obtained in Application Example 14 exhibited solid-liquid stratification on day 26, indicating that the liquid fertilizer sample corresponding to Application Example 14 was also unstable. This is because the difference between Application Example 14 and Application Example 11 is that the mass fraction of the colloidal suspension G (or suspending agent) obtained in Example 3 used in the preparation of the liquid fertilizer in Application Example 14 was 0.6 parts, which is less than the range of 0.8-1.5 parts by weight as stated in the claims. That is, the content of suspending agent in the prepared liquid fertilizer was insufficient, resulting in poor suspension of fertilizer molecules and easy crystallization of fertilizer molecules into precipitates in Application Example 14. The sample prepared in Application Example 14 also eventually exhibited solid-liquid stratification and was not suitable for use as a liquid fertilizer.

[0130] As can be seen from Table 3, the suspensions obtained from Examples 1, 3, and 5 significantly increased the soybean leaf weight gain rate, the SPAD value (or chlorophyll content) of soybean leaves, and the dry weight of whole plant biomass compared with the control group (fertilization with water) when applied to the liquid fertilizers prepared in Examples 11-13 and Example 15. This indicates that the above liquid fertilizers all have the effect of promoting crop growth.

[0131] Furthermore, the liquid fertilizer prepared using the suspension obtained in Example 3, when applied to Examples 11-13, exhibited at least 30% higher light transmittance than the liquid fertilizer prepared in Example 15. This is because the preparation of the liquid fertilizer in Example 15 involved the use of black graphene oxide, which blocks light and consequently reduces the light transmittance of the liquid fertilizer, thus affecting leaf photosynthesis. This also indicates that the suspension prepared in Example 3 has lower light blocking, resulting in higher light transmittance for the corresponding liquid fertilizer, which is beneficial for leaf photosynthesis. The liquid fertilizer prepared using the suspension obtained in Example 3, when applied to Example 11, showed a 4.9% higher leaf weight gain rate than the liquid fertilizer prepared in Example 15, indicating that the suspension obtained in Example 3 provides better leaf adhesion performance than the suspension composed of graphene oxide, xanthan gum, and chitosan. Because the liquid fertilizer corresponding to Example 3 has better light transmittance and adhesion to the leaf surface, it can better promote the photosynthesis of crops and enable crops to absorb the nutrients in the liquid fertilizer in a balanced way. Therefore, compared with the liquid fertilizer prepared by Example 15, the liquid fertilizer corresponding to Example 3 increased the SPDA value of leaves by 26.5% and the dry weight of whole plant biomass by 34.9%.

[0132] Table 1 shows the stability of the suspensions prepared in Examples 1-5 and the liquids obtained in Comparative Examples 6-10, which were evaluated by recording whether the liquids exhibited stratification within 30 days.

[0133]

[0134] Table 2 shows the stability of the liquid fertilizers obtained in Application Examples 11-15. The stability of the liquid was assessed by recording whether the liquid exhibited stratification within 30 days. In the table, Examples 1-5 and Comparative Examples 7-10 represent liquid fertilizers prepared from the suspensions or samples obtained in Application Example 11 from Examples 1-5 and Comparative Examples 7-10, respectively, while Examples 12-15 represent liquid fertilizers obtained in Application Examples 12-15, respectively.

[0135]

[0136] Table 3 shows the light transmittance of the liquid fertilizers obtained in Application Examples 11-13 and 15, and the weight gain rate (%) of the leaves when attached to soybean leaves, along with the corresponding SPAD values ​​and whole plant dry weights of the soybean leaves. In the table, Examples 1, 3, and 5 represent liquid fertilizers prepared from the suspensions obtained in Examples 1, 3, and 5, respectively, in Application Example 11; Application Examples 12, 13, and 15 represent liquid fertilizers obtained in Application Examples 12, 13, and 15, respectively; and "water" represents water used instead of liquid fertilizer.

[0137]

Claims

1. A method for preparing a suspending agent, characterized in that, The steps are as follows: (1) Dissolve NaOH in methanol solvent at 45-55℃ to obtain solution A, wherein the weight ratio of NaOH to methanol is 1:(5-7); (2) Dissolve zinc nitrate hexahydrate and aluminum nitrate nonahydrate in methanol solvent at room temperature to obtain solution B, wherein the weight ratio of zinc nitrate hexahydrate, aluminum nitrate nonahydrate and methanol is (1.73-2.75):1:(42-48.6); (3) Add the solution B obtained in step (2) dropwise to the solution A obtained in step (1) at 45-55℃ and stirring at 2000-5000r / min. The dropwise rate is 1 drop every 2-5 seconds. When the pH of the resulting mixture is 7.5-8.5, the dropwise addition ends. Continue the reaction for 10-24 hours, and then obtain a white mixture C. (4) Heat the white mixture C obtained in step (3) to 55-65℃, add sodium unsaturated fatty acid, and then stir at a speed of 1000-3000 r / min for 3-12 h to obtain a white mixture D containing unsaturated fatty acid-zinc aluminum methoxy hydrotalcite, wherein the weight ratio of the white mixture C obtained in step (3) to sodium unsaturated fatty acid is (6-15):(0.28-0.58); (5) Filter the mixture D containing unsaturated fatty acid-zinc-aluminum hydrotalcite obtained in step (4) at room temperature. Wash the filtered gel with methanol solvent 3-5 times to obtain white unsaturated fatty acid-zinc-aluminum hydrotalcite gel E, wherein the weight ratio of mixture D to methanol solvent is 1:

3. (6) Sodium stearate and polyvinyl alcohol are mixed in water at 30-45℃, with a mass ratio of sodium stearate, polyvinyl alcohol and water of 1:(1.5~3):(80~120). The mixture is stirred at 500-1500 r / min for 0.5-3 h and then cooled to room temperature to obtain solution F. Sodium stearate dissolves in water and ionizes to produce negatively charged stearate anions. Carboxyl stearate and hydroxyl polyvinyl alcohol molecules can form hydrogen bonds in aqueous solution to generate negatively charged stearic acid / polyvinyl alcohol supramolecular complexes. (7) At 18-35℃ and under stirring conditions, the unsaturated fatty acid-zinc-aluminum hydrotalcite colloid E obtained in step (5) is added to the solution F obtained in step (6). The stirring speed is 500-3500 r / min. While the unsaturated fatty acid-zinc-aluminum hydrotalcite colloid E comes into contact with water and undergoes hydrolysis, it also undergoes interlayer ion exchange reaction with the negatively charged stearic acid / polyvinyl alcohol supramolecular complex. After stirring for 2-12 h, a colloidal suspension G containing stearic acid / polyvinyl alcohol-zinc-aluminum hydrotalcite is obtained. The colloidal suspension G is a suspending agent. The weight ratio of the solution F to the colloid E is (1-3):

1.

2. The preparation method according to claim 1, characterized in that, The weight ratio of magnesium nitrate hexahydrate, aluminum nitrate nonahydrate, and methanol in step (2) is 2.25:1:

45.

3. The preparation method according to claim 1, characterized in that, The white mixture C obtained in step (3) in step (4) has a weight ratio of 11:0.43 to sodium unsaturated fatty acids.

4. The preparation method according to claim 1, characterized in that, The mass ratio of sodium stearate, polyvinyl alcohol, and water in step (6) is 1:2.3:

100.

5. The preparation method according to claim 1, characterized in that, The weight ratio of solution F to gel E in step (7) is 2:

1.

6. A method for preparing a light-transmitting balanced liquid fertilizer using a suspending agent, characterized in that, The preparation method uses raw materials including: the suspending agent, macro-elements and micro-elements as described in any one of claims 1-5, and the preparation steps are as follows: at room temperature, macro-elements and micro-elements are added to the suspending agent or colloidal suspension G obtained in step (7) of claim 1 and stirred for 0.2-1.5 h at a stirring speed of 100-300 r / min, and then water is added and stirred at the same stirring speed for 0.5 h to obtain a high light transmittance balanced liquid fertilizer, which includes the following components and their mass fractions: colloidal suspension G is 0.8-1.5 parts, macro-elements are 66-85 parts, micro-elements are 2-2.7 parts, and water is 11.5-30 parts.

7. The preparation method according to claim 6, characterized in that, The macroelements are one or a mixture of more than one of urea, urea ammonium nitrate solution, liquid phosphoric acid, ammonium polyphosphate solution, dipotassium hydrogen phosphate, potassium pyrophosphate, and potassium acetate; the microelements are one or a mixture of more than one of EDTA-Fe-13, EDTA-Mn-13, EDTA-Cu-15, EDTA-Zn-15, boric acid, and disodium octaborate tetrahydrate.

8. The preparation method according to claim 6, characterized in that, The components and their mass fractions are as follows: colloidal suspension G is 1.3 parts, macroelements are 66 parts, microelements are 2.7 parts, and water is 30 parts.

9. The application of the light-transmitting balanced liquid fertilizer prepared by the method according to any one of claims 6-8 in the field of foliar fertilizer.

Images