Silicon-calcium-potassium-magnesium type soil conditioner and preparation method thereof

Abstract

The invention belongs to the technical field of soil conditioners, and particularly relates to a silicon-calcium-potassium-magnesium type soil conditioner and a preparation method thereof. The preparation method comprises the following steps: S1, adding quick lime into a sodium silicate solution to react, separating and drying to obtain calcium silicate with the water content of 0-80%; s2, uniformly mixing calcium silicate, magnesium salt / molecular sieve / modified cellulose and potassium salt / modified chitosan to obtain a mixture; and S3, spraying an alcoholic solution containing alkyl quaternary ammonium salt modified palygorskite on the mixture, stirring, and drying to obtain the product. The silicon-calcium-potassium-magnesium type soil conditioner disclosed by the invention can meet the index requirements of the national standard GB / T 36207-2018 'Silicon-calcium-potassium-magnesium Fertilizer', has good slow release effect and storage stability, improves the pH value of acid soil, and increases the content of organic matters in the soil.

Description

Technical Field

[0001] The invention belongs to the technical field of soil conditioners, and in particular relates to a silicon-calcium-potassium-magnesium type soil conditioner and a preparation method thereof. Background Art

[0002] Soil acidification is one of the important factors restricting the green and high-quality development of agriculture. Soil acidification can lead to a decrease in soil pH, aggravate the imbalance of soil calcium and magnesium nutrients, increase the activity of heavy metals, and increase the incidence of soil-borne diseases.

[0003] At present, silicon-calcium-potassium-magnesium type soil conditioners are mainly alkaline soil conditioners made from high-temperature calcination of phosphate tailings, phosphogypsum and potassium feldspar. They contain multiple nutrients such as calcium, magnesium and silicon. They can not only adjust the acidic pH value, but also significantly increase the content of fast-acting nutrients in the soil. At the same time, they have little impact on the soil and ecological environment, and can effectively overcome the shortcomings of lime and other agents that easily cause soil compaction when adjusting the pH value of acidic soil.

[0004] The methods of silicon-calcium-potassium-magnesium soil conditioners in the prior art mainly include high-temperature calcination and hydrothermal methods. For example, the Chinese patent with publication number CN113620724A discloses a method for producing silicon-calcium-potassium-magnesium fertilizer using dolomite limestone, wherein dolomite limestone, potassium feldspar, phosphogypsum, etc. are mixed with additives I and II in proportion, and a mineral fertilizer produced using dolomite limestone is prepared through molding, drying, calcination, cooling, ball milling, granulation and other processes. The effective components of the silicon-calcium-potassium-magnesium fertilizer obtained by this technical solution are not less than 85%, of which effective calcium oxide is greater than 30%, effective silicon dioxide is greater than 21%, effective magnesium oxide is greater than 7%, effective potassium oxide is greater than 5%, and it contains a variety of trace elements. The fertilizer is weakly alkaline (pH=8-12), which can be used to adjust the physical and chemical properties of the soil and comprehensively improve the level of trace elements in the soil; however, the preparation process is relatively complicated, and the high-temperature calcination causes high costs.

[0005] The Chinese patent with publication number CN110078538A discloses a method for preparing silicon-calcium-potassium-magnesium slow-release fertilizer by comprehensive utilization of tailings and a preparation method thereof, comprising the following steps: (1) mixing the raw materials of each component according to the following mass ratio: low-grade magnesite: carnallite tailings: high-silicon iron tailings: boron mud: quicklime = 3-4:4-6:3-4:6-7:3-4, and fully mixing them by a vertical turbulent mixer to obtain a homogeneous mixture; (2) mixing the mixture of step (1) with water to form a uniform slurry; (3) feeding the uniform slurry of step (2) into a high-pressure magnetic stirring reactor through a slurry pump to decompose and synthesize the substances to obtain a reaction material; (4) drying the reaction material of step (3) in a drying furnace, grinding it with a Raymond mill, and classifying it with a vibrating screen to obtain a silicon-calcium-potassium-magnesium slow-release fertilizer. Although the contents of effective K2O, CaO, MgO and SiO2 in the products obtained by this technical solution have reached the national standards, there are still a series of problems such as excessive use of additives, harsh reaction conditions, high production costs, and failure to consider the leaching of heavy metal elements in tailings. Summary of the invention

[0006] In view of the above problems, the present invention provides a silicon-calcium-potassium-magnesium type soil conditioner and a preparation method thereof. The silicon-calcium-potassium-magnesium type soil conditioner of the present invention can meet the index requirements of the national standard GB / T 36207-2018 "Silicon-calcium-potassium-magnesium type fertilizer", and has good slow-release effect and storage stability, improves the pH value of acidic soil, and increases the organic matter content of soil.

[0007] To achieve the above purpose, the technical solution adopted by the present invention is as follows: The first aspect of the present invention provides a method for preparing a silicon-calcium-potassium-magnesium type soil conditioner, comprising the following steps: S1, adding quicklime to the sodium silicate solution to react, separate, and dry to obtain calcium silicate with a moisture content of 0-80%; S2, mixing calcium silicate, magnesium salt / molecular sieve / modified cellulose and potassium salt / modified chitosan uniformly to obtain a mixture; S3, spraying the alcohol solution containing alkyl quaternary ammonium salt modified palygorskite on the mixture, stirring, and drying; The mass ratio of the calcium silicate, magnesium salt / molecular sieve / modified cellulose, potassium salt / modified chitosan and alkyl quaternary ammonium salt modified palygorskite is 100:(110-130):(8-10):(3-6).

[0008] The source of the sodium silicate solution in the present invention includes but is not limited to self-made sodium silicate solution or sodium silicate solution generated by comprehensive utilization of fly ash or high-silicon bauxite.

[0009] Preferably, the sodium silicate solution in step S1 is derived from the sodium silicate solution produced during the comprehensive utilization of fly ash or high-silicon bauxite.

[0010] Preferably, the mass ratio of the effective calcium oxide in the quicklime to the silicon dioxide in the sodium silicate solution in step S1 is (0.6-2):1, preferably (0.8-1.2):1.

[0011] Preferably, in step S1, the reaction temperature is 20-150° C., preferably 70-90° C., and the reaction time is 0.2-10 h, preferably 1-1.5 h.

[0012] Preferably, the method for preparing magnesium salt / molecular sieve / modified cellulose in step S2 comprises the following steps: Step 1, dispersing the molecular sieve in a magnesium salt aqueous solution, and performing an exchange reaction to obtain a magnesium-exchanged molecular sieve; Step 2, adding cellulose to a solvent to dissolve, adding a dimethylacetamide solution containing lauric acid, 4-toluenesulfonyl chloride and triethylene glycol mono-p-toluenesulfonate and pyridine under nitrogen protection to carry out a modification reaction, and after the reaction is completed, performing reduced pressure distillation, water recrystallization, and drying to obtain modified cellulose; Step 3: Add the magnesium-exchanged molecular sieve and modified cellulose into water for stirring reaction. After the reaction is completed, filter and dry to obtain the product.

[0013] Preferably, the molecular sieve in step 1 is a FAU type Y zeolite molecular sieve, with a silicon-aluminum molar ratio of 60-90 and a specific surface area of ​​650-750m 2 / g.

[0014] Further preferably, the molecular sieve in step 1 is a FAU type Y zeolite molecular sieve with a silicon-aluminum molar ratio of 81 and a specific surface area of ​​710 m 2 / g.

[0015] Preferably, the concentration of the magnesium salt aqueous solution in step 1 is 4-6 mol / L, and the magnesium salt aqueous solution is selected from at least one of a magnesium chloride aqueous solution and a magnesium sulfate aqueous solution.

[0016] Preferably, the ratio of the molecular sieve and the magnesium salt aqueous solution in step 1 is 1 g: 100-200 mL.

[0017] Preferably, the temperature of the exchange reaction in step 1 is 25-30° C., and the time of the exchange reaction is 8-12 h.

[0018] Preferably, the solvent in step 2 is a mixture of lithium chloride and dimethylacetamide, and the mass ratio of the two is (8-10): (90-92).

[0019] Preferably, the mass ratio of cellulose, solvent, dimethylacetamide solution and pyridine in step 2 is 1:(10-15):(15-25):(2-3).

[0020] Preferably, the dimethylacetamide solution in step 2 is a mixture of lauric acid, 4-toluenesulfonyl chloride, triethylene glycol mono-p-toluenesulfonate and dimethylacetamide; the mass ratio of lauric acid, 4-toluenesulfonyl chloride, triethylene glycol mono-p-toluenesulfonate and dimethylacetamide is 1:(1.1-1.3):(1.5-2.5):(6-8).

[0021] Preferably, the temperature of the modification reaction in step 2 is 80-90° C. and the time is 18-22 h.

[0022] Preferably, the mass ratio of the magnesium-exchanged nanomolecular sieve, modified cellulose and water in step 3 is (1-3): (3-5): (20-30).

[0023] Preferably, the stirring reaction in step 3 is carried out at a speed of 300-500 rpm for 6-10 h.

[0024] Preferably, the method for preparing potassium salt / modified chitosan in step S2 comprises the following steps: (1) Zinc oxide and chitosan solution react and then dry to obtain zinc oxide / chitosan; (2) adding zinc oxide / chitosan into a stearic acid solution for immersion and then taking out and drying to obtain a modified chitosan having a porous structure; (3) Adding the modified chitosan and potassium salt into an ethanol aqueous solution for stirring reaction, filtering and drying the obtained chitosan after the stirring reaction is completed.

[0025] In order to make full use of the sodium silicate solution produced by the comprehensive utilization of fly ash or high-silicon bauxite with high added value, the inventors added quicklime thereto. The synthesized calcium silicate can be used as one of the raw materials of silicon-calcium-potassium-magnesium type soil conditioner. The silicon-calcium-potassium-magnesium type soil conditioner obtained by mixing it with potassium salt and magnesium salt is more convenient. However, potassium salt and magnesium salt are easily lost due to the influence of rainwater. In order to solve this technical problem, the inventors creatively modified potassium salt and magnesium salt in different ways. Among them, the modification of magnesium salt is to first prepare a magnesium-exchanged molecular sieve, and magnesium ions can be fixed inside or on the surface of the pores of the molecular sieve; then lauric acid and triethylene glycol mono-p-toluenesulfonate are used to prepare comb-shaped modified cellulose, and finally the comb-shaped modified cellulose is coated on the surface of the magnesium-exchanged molecular sieve. The hydrophobicity and network structure of the modified cellulose can effectively slow down the speed at which water molecules enter the interior of the molecular sieve, thereby controlling The release rate of magnesium ions is controlled; the modification of potassium salt is to first graft chitosan on the surface of zinc oxide, and then immerse it in a stearic acid solution, stearic acid can be adsorbed on the surface of chitosan, and when drying, the ethanol aqueous solution will volatilize to form a modified chitosan with a porous structure, and finally the modified chitosan is mixed with potassium salt, and the potassium salt is adsorbed in the porous structure of the modified chitosan while the hydrophobic layer of stearic acid forms a barrier to slow down the penetration rate of water molecules, thereby controlling the release rate of potassium salt; the release rate of potassium salt and magnesium salt is controlled, and the local pH surge at the soil fertilization point can also be avoided to cause the soil to be fixed in phosphate ions; at the same time, the inventors found that different modification methods for potassium salt and magnesium salt can avoid the agglomeration or adhesion phenomenon that is easy to occur when calcium silicate with a water content of 20-40% is mixed with potassium salt and magnesium salt; and the porosity, bulk density, moisture content and organic matter content of the soil can be improved.

[0026] Preferably, in step (1), the ratio of zinc oxide to chitosan solution is 1 g: (10-30) mL; the chitosan solution is a mixture of chitosan and acetic acid, and the concentration of chitosan is 0.05 g / mL.

[0027] Preferably, the reaction temperature in step (1) is 70-90°C and the reaction time is 2-4h.

[0028] Preferably, in step (2), the ratio of zinc oxide / chitosan to stearic acid solution is 1 g: (20-30) mL; the stearic acid solution is a mixture of stearic acid and ethanol, and the concentration of stearic acid is 10 g / mL.

[0029] Preferably, the immersion temperature in step (2) is 50-70° C. and the immersion time is 1-2 h.

[0030] Preferably, in step (3), the ratio of modified chitosan, potassium salt and ethanol aqueous solution is 1 g: (1-2) g: (10-20) mL.

[0031] Preferably, the ethanol aqueous solution is a mixture of ethanol and water in a mass ratio of (70-90):1.

[0032] Preferably, the potassium salt is selected from at least one of potassium chloride and potassium sulfate.

[0033] Preferably, the stirring reaction speed in step (3) is 300-500 rpm and the time is 3-5 h.

[0034] Preferably, the water content of the calcium silicate is 20-40%.

[0035] Preferably, the alcohol solution containing alkyl quaternary ammonium salt-modified palygorskite in step S3 is a mixture of alkyl quaternary ammonium salt-modified palygorskite and ethanol, and the ratio of the two is 1 g: (20-30) mL.

[0036] Preferably, the preparation method of the alkyl quaternary ammonium salt modified palygorskite is: taking palygorskite and ethanol, adding alkyl quaternary ammonium salt at 80-100° C. for reflux reaction for 6-10 hours, and after the reaction is completed, washing and drying the product.

[0037] Preferably, the ratio of palygorskite, ethanol and alkyl quaternary ammonium salt is 1 g: (10-30) mL: (0.4-0.6) mL.

[0038] Preferably, the alkyl quaternary ammonium salt is hexadecyltrimethylammonium bromide.

[0039] In order to avoid the homemade calcium silicate from generating a large amount of dust and to ensure its fluidity, the water content of the calcium silicate is controlled to be 20-40% in the present invention. However, the calcium silicate with a high water content is prone to agglomeration or adhesion during the mixing process with potassium salt and magnesium salt and during the storage process. The inventors found that although the modified potassium salt and magnesium salt can avoid agglomeration or adhesion during the mixing process with calcium silicate, they are still prone to agglomeration or adhesion during the high temperature and high humidity storage process. To solve this technical problem, the inventors creatively prepared alkyl quaternary ammonium salt modified palygorskite, which was sprayed on the mixture to avoid agglomeration or adhesion of the silicon-calcium-potassium-magnesium type soil conditioner. The inventors further found that when palygorskite was replaced with montmorillonite, the effect was not good. The inventors speculated that this was because the special layered chain structure of palygorskite could provide more physical support than the layered structure of montmorillonite, thereby avoiding the adhesion or agglomeration of the silicon-calcium-potassium-magnesium type soil conditioner.

[0040] In addition, the inventors have also found that the mass ratio of calcium silicate, magnesium salt / molecular sieve / modified cellulose, potassium salt / modified chitosan and alkyl quaternary ammonium salt modified palygorskite needs to be controlled to be 100:(110-130):(8-10):(3-6), otherwise the effect of the silicon-calcium-potassium-magnesium type soil conditioner in regulating soil pH and increasing organic matter content will be reduced.

[0041] As another embodiment, magnesium salt / molecular sieve / modified cellulose may be replaced by magnesium salt; and potassium salt / modified chitosan may be replaced by potassium salt.

[0042] The second aspect of the present invention provides a silicon-calcium-potassium-magnesium type soil conditioner obtained by the preparation method of the above-mentioned silicon-calcium-potassium-magnesium type soil conditioner.

[0043] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention realizes high added value and full utilization of the sodium silicate solution produced by the comprehensive utilization of fly ash or high-silicon bauxite, and quicklime is added thereto. The synthesized calcium silicate can be used as one of the raw materials of silicon-calcium-potassium-magnesium type soil conditioner, and the silicon-calcium-potassium-magnesium type soil conditioner obtained by mixing it with potassium salt and magnesium salt is more convenient.

[0044] 2. The present invention creatively modifies the magnesium salt: first, a magnesium-exchanged molecular sieve is prepared, and the magnesium ions can be fixed inside the pores or on the surface of the molecular sieve; then, lauric acid and triethylene glycol mono-p-toluenesulfonate are used to prepare comb-shaped modified cellulose, and finally, the comb-shaped modified cellulose is coated on the surface of the magnesium-exchanged molecular sieve. The hydrophobicity and network structure of the modified cellulose can effectively slow down the speed at which water molecules enter the interior of the molecular sieve, thereby controlling the release rate of magnesium ions.

[0045] 3. The present invention creatively modifies potassium salt: chitosan is first grafted onto the surface of zinc oxide, and then immersed in a stearic acid solution. Stearic acid can be adsorbed on the surface of chitosan. When drying, the ethanol aqueous solution will evaporate to form a modified chitosan with a porous structure. Finally, the modified chitosan is mixed with potassium salt. While the potassium salt is adsorbed in the porous structure of the modified chitosan, the hydrophobic layer of stearic acid forms a barrier to slow down the penetration rate of water molecules, thereby controlling the release rate of the potassium salt.

[0046] 4. The release rate of potassium salt and magnesium salt of the present invention is controlled, and the local pH surge at the soil fertilization point can also be avoided, which causes the phosphate ions in the soil to be fixed; at the same time, different modification methods are used for potassium salt and magnesium salt, which avoids the agglomeration or adhesion phenomenon that is easy to occur when calcium silicate with a water content of 20-40% is mixed with potassium salt and magnesium salt; and the porosity, bulk density, moisture content and organic matter content of the soil can be improved.

[0047] 5. The present invention creatively prepares alkyl ammonium salt modified palygorskite, which is sprayed on the mixture, which can prevent the silicon calcium potassium magnesium type soil conditioner from caking or sticking, and controls the mass ratio of calcium silicate, magnesium salt / molecular sieve / modified cellulose, potassium salt / modified chitosan and alkyl quaternary ammonium salt modified palygorskite to 100: (110-130): (8-10): (3-6), thereby preventing the silicon calcium potassium magnesium type soil conditioner from having poor effects in adjusting soil pH and increasing organic matter content. BRIEF DESCRIPTION OF THE DRAWINGS

[0048] Figure 1 This is the SEM image of the calcium silicate prepared in Basic Example 1. DETAILED DESCRIPTION

[0049] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, a specific implementation scheme is now described in detail.

[0050] The present invention is further described below in conjunction with the embodiments, but the present invention is not limited to the following embodiments. The implementation conditions used in the embodiments can be further adjusted according to the different requirements of specific use, and the implementation conditions not indicated are conventional conditions in the industry. The technical features involved in each embodiment of the present invention can be combined with each other as long as they do not conflict with each other.

[0051] In the following examples and comparative examples, unless otherwise specified, all raw materials used were commercially available or prepared by conventional methods in the art.

[0052] Basic Example 1 Quicklime with an effective calcium oxide content of 85.5% was added to a sodium silicate solution with a silicon dioxide concentration of 102.3 g / L generated from fly ash during comprehensive utilization. The reaction was carried out at a mass ratio of effective calcium oxide in the quicklime to silicon dioxide in the sodium silicate solution of 1.2. The reaction temperature was 90°C and the reaction time was 1 h. The calcium silicate index obtained after separation without drying is shown in Table 1: Table 1

[0053] Basic Example 2 Quicklime with an effective calcium oxide concentration of 105.6 g / L was added to a sodium silicate solution with a silicon dioxide concentration of 30.02 g / L generated from fly ash during comprehensive utilization. The reaction was carried out at a mass ratio of effective calcium oxide in the quicklime to silicon dioxide in the sodium silicate solution of 1. The reaction temperature was 80°C and the reaction time was 1.2 h. The calcium silicate index obtained after separation without drying is shown in Table 2: Table 2

[0054] Example 1 A silicon-calcium-potassium-magnesium type soil conditioner, the preparation method of which is as follows: S1, drying the calcium silicate that has not been dried in Basic Example 1 until the moisture content is 38.24%; S2, mixing calcium silicate, magnesium salt / molecular sieve / modified cellulose and potassium salt / modified chitosan uniformly to obtain a mixture; S3, spraying the alcohol solution containing alkyl quaternary ammonium salt modified palygorskite on the mixture, stirring, and drying; The mass ratio of the calcium silicate, magnesium salt / molecular sieve / modified cellulose, potassium salt / modified chitosan and alkyl quaternary ammonium salt modified palygorskite is 100:120:9:5.

[0055] The preparation method of magnesium salt / molecular sieve / modified cellulose in step S2 is: Step 1, dispersing the molecular sieve in a magnesium salt aqueous solution, and performing an exchange reaction to obtain a magnesium-exchanged molecular sieve; Step 2, adding cellulose to a solvent to dissolve, adding a dimethylacetamide solution containing lauric acid, 4-toluenesulfonyl chloride and triethylene glycol mono-p-toluenesulfonate and pyridine under nitrogen protection to carry out a modification reaction, and after the reaction is completed, performing reduced pressure distillation, water recrystallization, and drying to obtain modified cellulose; Step 3: Add the magnesium-exchanged molecular sieve and modified cellulose into water for stirring reaction. After the reaction is completed, filter and dry to obtain the product.

[0056] The molecular sieve in step 1 is a FAU type Y zeolite molecular sieve with a silicon-aluminum molar ratio of 81 and a specific surface area of ​​710 m 2 / g, purchased from Tianjin Nanhua Catalyst Co., Ltd., model NKF-7-5-80.

[0057] The concentration of the magnesium salt aqueous solution in step 1 is 5 mol / L, and the magnesium salt aqueous solution is a magnesium sulfate aqueous solution.

[0058] The ratio of the molecular sieve and the magnesium salt aqueous solution in step 1 is 1 g: 200 mL.

[0059] The temperature of the exchange reaction in step 1 is 25° C., and the time of the exchange reaction is 10 h.

[0060] The solvent in step 2 is a mixture of lithium chloride and dimethylacetamide, and the mass ratio of the two is 9:91.

[0061] The mass ratio of cellulose, solvent, dimethylacetamide solution and pyridine in step 2 is 1:12:20:2.5; the dimethylacetamide solution is a mixture of lauric acid, 4-toluenesulfonyl chloride, triethylene glycol mono-p-toluenesulfonate and dimethylacetamide; the mass ratio of lauric acid, 4-toluenesulfonyl chloride, triethylene glycol mono-p-toluenesulfonate and dimethylacetamide is 1:1.2:2:7.

[0062] The temperature of the modification reaction in step 2 is 85° C. and the time is 20 h.

[0063] The mass ratio of the magnesium-exchanged nanomolecular sieve, modified cellulose and water in step 3 is 2:4:25.

[0064] The stirring reaction in step 3 is carried out at a speed of 400 rpm for 8 hours.

[0065] The preparation method of potassium salt / modified chitosan in step S2 is: (1) Zinc oxide and chitosan solution react and then dry to obtain zinc oxide / chitosan; (2) adding zinc oxide / chitosan into a stearic acid solution for immersion and then taking out and drying to obtain a modified chitosan having a porous structure; (3) Adding the modified chitosan and potassium salt into an ethanol aqueous solution for stirring reaction, filtering and drying the obtained chitosan after the stirring reaction is completed.

[0066] In step (1), the ratio of zinc oxide to chitosan solution is 1 g:20 mL; the chitosan solution is a mixture of chitosan and acetic acid, and the concentration of chitosan is 0.05 g / mL.

[0067] Zinc oxide was purchased from Shijiazhuang Honghong Chemical Co., Ltd., and chitosan was agricultural grade and purchased from Shandong Haiyihua Biotechnology Co., Ltd.

[0068] The reaction temperature of step (1) is 80°C and the reaction time is 3h.

[0069] In step (2), the ratio of zinc oxide / chitosan to stearic acid solution is 1 g:25 mL; the stearic acid solution is a mixture of stearic acid and ethanol, and the concentration of stearic acid is 10 g / mL.

[0070] The immersion temperature in step (2) is 60° C. and the immersion time is 1.5 h.

[0071] In step (3), the ratio of modified chitosan, potassium salt and ethanol aqueous solution is 1 g:1.5 g:15 mL.

[0072] The ethanol aqueous solution is a mixture of ethanol and water in a mass ratio of 80:1; and the potassium salt is potassium sulfate.

[0073] The stirring reaction speed in step (3) is 400 rpm and the time is 4 hours.

[0074] The alcohol solution containing alkyl quaternary ammonium salt-modified palygorskite in step S3 is a mixture of alkyl quaternary ammonium salt-modified palygorskite and ethanol, and the ratio of the two is 1 g:25 mL.

[0075] The preparation method of the alkyl quaternary ammonium salt modified palygorskite is as follows: palygorskite and ethanol are taken, and the alkyl quaternary ammonium salt is added at 90° C. to carry out reflux reaction for 8 hours, and after the reaction is completed, the product is washed and dried to obtain the product.

[0076] Palygorskite was purchased from Shunze Mineral Products Processing Plant in Lingshou County.

[0077] The ratio of the palygorskite, ethanol and alkyl quaternary ammonium salt is 1 g: 20 mL: 0.5 mL.

[0078] The alkyl quaternary ammonium salt is hexadecyltrimethylammonium bromide.

[0079] Example 2 The difference from Example 1 is that the mass ratio of calcium silicate, magnesium salt / molecular sieve / modified cellulose, potassium salt / modified chitosan and alkyl quaternary ammonium salt modified palygorskite is 100:110:8:3; the rest are the same.

[0080] Example 3 The difference from Example 1 is that the mass ratio of the calcium silicate, magnesium salt / molecular sieve / modified cellulose, potassium salt / modified chitosan and alkyl quaternary ammonium salt modified palygorskite is 100:130:10:6; the rest are the same.

[0081] Comparative Example 1 The difference from Example 1 is that magnesium salt / molecular sieve / modified cellulose is replaced by magnesium salt / modified chitosan of equal mass, and the preparation method of magnesium salt / modified chitosan is the same as potassium salt / modified chitosan; the rest are the same.

[0082] Comparative Example 2 The difference from Example 1 is that potassium salt / modified chitosan is replaced by a mixture of potassium salt and chitosan, and the mass ratio of the two is 1.5:1; the rest are the same.

[0083] Comparative Example 3 The difference from Example 1 is that the preparation method of the potassium salt / modified chitosan is: (1) Zinc oxide and chitosan solution react and then dry to obtain zinc oxide / chitosan; (2) Add zinc oxide / chitosan and potassium salt to ethanol aqueous solution for stirring reaction. After the stirring reaction is completed, filter and dry to obtain the obtained product. The ratio of zinc oxide / chitosan, potassium salt and ethanol aqueous solution is 1 g:1.5 g:15 mL; the rest are the same.

[0084] Comparative Example 4 The difference from Example 1 is that magnesium salt / molecular sieve / modified cellulose is replaced by a mixture of magnesium salt, molecular sieve and modified cellulose, and the mass ratio of the three is 1:1:4; the rest are the same.

[0085] Comparative Example 5 The difference from Example 1 is that the magnesium salt / molecular sieve / modified cellulose is replaced by magnesium salt / molecular sieve of equal mass, and the preparation method of the magnesium salt / molecular sieve is: dispersing the molecular sieve in a magnesium salt aqueous solution, performing an exchange reaction, and obtaining the magnesium salt / molecular sieve; the rest are the same.

[0086] Comparative Example 6 The difference from Example 1 is that the modified cellulose is replaced by cellulose of equal mass, that is, magnesium salt / molecular sieve / modified cellulose is replaced by magnesium salt / molecular sieve / cellulose of equal mass; the rest are the same.

[0087] Comparative Example 7 The difference from Example 1 is that the palygorskite is replaced by montmorillonite of equal mass, and the montmorillonite is purchased from Shunze Mineral Products Processing Plant in Lingshou County; the rest are the same.

[0088] Comparative Example 8 The difference from Example 1 is that the mass ratio of calcium silicate, magnesium salt / molecular sieve / modified cellulose, potassium salt / modified chitosan and alkyl quaternary ammonium salt modified palygorskite is 80:140:11:3; the rest are the same.

[0089] Performance Testing: 1. The silicon-calcium-potassium-magnesium type soil conditioner of Examples 1-3 was tested according to GB / T 36207-2018. The results are shown in Table 3. 2. Sustained release performance: The release rate test was carried out according to GB / T23348-2009 standard, the test temperature was 25°C, and the results are shown in Table 4; 3. Storage stability: Place the silicon-calcium-potassium-magnesium soil conditioner in an environment with a temperature of 40°C and a humidity of 65% for 6 months, and observe whether there is adhesion or agglomeration. The results are shown in Table 5. 4. Potted plant test: The soil used was acidic red soil with a pH of 5.0 and an organic matter content of 13.52 g / kg. The amount of silicon-calcium-potassium-magnesium type soil conditioner applied to each pot was 100 kg / mu. After 6 months, the following tests were conducted: soil pH (standard HJ962-2018), soil porosity, bulk density (standard NY / T 1121.4-2006), soil moisture content (standard NY / T 1121.3-2006) and organic matter content (standard NY / T 1121.6-2006). The results are shown in Table 6.

[0090] Table 3

[0091] It can be seen from Table 3 that the silicon-calcium-potassium-magnesium type soil conditioner prepared in Examples 1-3 of the present invention can meet the index requirements of the national standard GB / T 36207-2018 "Silicon-calcium-potassium-magnesium type fertilizer".

[0092] Table 4

[0093] It can be seen from Table 4 that the silicon-calcium-potassium-magnesium type soil conditioner of Examples 1-3 has good slow-release performance; In Comparative Example 1, since magnesium salt / molecular sieve / modified cellulose was replaced with magnesium salt / modified chitosan of the same mass, the sustained release performance of the obtained silicon-calcium-potassium-magnesium type soil conditioner decreased, indicating that different modification methods for magnesium salt and potassium salt can achieve better sustained release performance; In Comparative Example 2, since potassium salt / modified chitosan is replaced by a mixture of potassium salt and chitosan; in Comparative Example 3, since stearic acid is not used for modification in the preparation method of potassium salt / modified chitosan, the sustained release performance of the obtained silicon-calcium-potassium-magnesium type soil conditioner is reduced; indicating that modifying potassium salt can improve the sustained release performance, but the effect is best only when the modification method of Examples 1-3 of the present invention is used; In Comparative Example 4, the magnesium salt / molecular sieve / modified cellulose was replaced by a mixture of magnesium salt, molecular sieve and modified cellulose; in Comparative Example 5, the magnesium salt / molecular sieve / modified cellulose was replaced by magnesium salt / molecular sieve of equal mass; and in Comparative Example 6, the modified cellulose was replaced by cellulose of equal mass; the sustained release performance of the obtained silicon-calcium-potassium-magnesium type soil conditioner decreased; indicating that modifying the magnesium salt can improve the sustained release performance, but the effect is best only when the modification method of Examples 1-3 of the present invention is adopted; The sustained-release performance of Comparative Examples 7-8 is not much different from that of Example 1.

[0094] Table 5

[0095] It can be seen from Table 5 that the silicon-calcium-potassium-magnesium type soil conditioner of Examples 1-3 has good storage stability under high temperature and high humidity; although Comparative Examples 1-8 did not show adhesion or agglomeration phenomenon at 1 day, their stability deteriorated after storage for 3 months or 6 months, and adhesion or agglomeration phenomenon occurred.

[0096] Table 6

[0097] It can be seen from Table 6 that the silicon-calcium-potassium-magnesium type soil conditioner of Examples 1-3 can improve the pH of acidic soil, and the improved soil has higher porosity, lower bulk density, higher moisture content and higher organic matter content; Comparative Examples 1-7 can also improve the organic matter content of acidic soil, but the porosity of the improved soil decreases, the bulk density increases, the moisture content decreases, and the organic matter content decreases; In Comparative Example 8, the mass ratio of calcium silicate, magnesium salt / molecular sieve / modified cellulose, potassium salt / modified chitosan and alkyl quaternary ammonium salt modified palygorskite is not within the preferred range. Although the soil improved by the obtained silicon calcium potassium magnesium type soil conditioner has higher porosity, lower bulk density and higher moisture content, it does not improve the pH of acidic soil well and has low organic matter content.

[0098] Finally, it should be noted that the above content is only used to illustrate the technical solution of the present invention, rather than to limit the scope of protection of the present invention. Simple modifications or equivalent substitutions of the technical solution of the present invention by ordinary technicians in this field do not deviate from the essence and scope of the technical solution of the present invention.

Claims

1. A method for preparing a silicon-calcium-potassium-magnesium type soil conditioner, characterized in that: The following steps are involved: S1, adding quicklime to the sodium silicate solution to react, separate, and dry to obtain calcium silicate with a moisture content of 0-80%; S2, mixing calcium silicate, magnesium salt / molecular sieve / modified cellulose and potassium salt / modified chitosan uniformly to obtain a mixture; S3, spraying the alcohol solution containing alkyl quaternary ammonium salt modified palygorskite on the mixture, stirring, and drying; The mass ratio of the calcium silicate, magnesium salt / molecular sieve / modified cellulose, potassium salt / modified chitosan and alkyl quaternary ammonium salt modified palygorskite is 100:(110-130):(8-10):(3-6).

2. The method for preparing the silicon-calcium-potassium-magnesium type soil conditioner according to claim 1, characterized in that: The method for preparing the magnesium salt / molecular sieve / modified cellulose in step S2 comprises the following steps: Step 1, the molecular sieve is dispersed in a magnesium salt aqueous solution, and an exchange reaction is performed to obtain a magnesium-exchanged molecular sieve; Step 2, adding cellulose to a solvent to dissolve, adding a dimethylacetamide solution containing lauric acid, 4-toluenesulfonyl chloride and triethylene glycol mono-p-toluenesulfonate and pyridine under nitrogen protection to carry out a modification reaction, and after the reaction is completed, performing reduced pressure distillation, water recrystallization, and drying to obtain modified cellulose; Step 3: Add the magnesium-exchanged molecular sieve and modified cellulose into water for stirring reaction. After the reaction is completed, filter and dry to obtain the product.

3. The method for preparing the silicon-calcium-potassium-magnesium type soil conditioner according to claim 2, characterized in that: The molecular sieve in step 1 is a FAU type Y zeolite molecular sieve with a silicon-aluminum molar ratio of 60-90 and a specific surface area of ​​650-750m 2 / g.

4. The method for preparing the silicon-calcium-potassium-magnesium type soil conditioner according to claim 3, characterized in that: The dimethylacetamide solution in step 2 is a mixture of lauric acid, 4-toluenesulfonyl chloride, triethylene glycol mono-p-toluenesulfonate and dimethylacetamide; the mass ratio of lauric acid, 4-toluenesulfonyl chloride, triethylene glycol mono-p-toluenesulfonate and dimethylacetamide is 1: (1.1-1.3): (1.5-2.5): (6-8).

5. The method for preparing the silicon-calcium-potassium-magnesium type soil conditioner according to claim 4, characterized in that: The mass ratio of the magnesium-exchanged nanomolecular sieve, modified cellulose and water in step 3 is (1-3): (3-5): (20-30).

6. The method for preparing the silicon-calcium-potassium-magnesium type soil conditioner according to claim 1, characterized in that: The method for preparing potassium salt / modified chitosan in step S2 comprises the following steps: (1) Zinc oxide and chitosan solution react and then dry to obtain zinc oxide / chitosan; (2) adding zinc oxide / chitosan into a stearic acid solution for immersion and then taking out and drying to obtain a modified chitosan having a porous structure; (3) Adding the modified chitosan and potassium salt into an ethanol aqueous solution for stirring reaction, filtering and drying the obtained chitosan after the stirring reaction is completed.

7. The method for preparing the silicon-calcium-potassium-magnesium type soil conditioner according to claim 6, characterized in that: In step (3), the ratio of modified chitosan, potassium salt and ethanol aqueous solution is 1 g: (1-2) g: (10-20) mL.

8. The method for preparing the silicon-calcium-potassium-magnesium type soil conditioner according to claim 1, characterized in that: The preparation method of the alkyl quaternary ammonium salt modified palygorskite is as follows: palygorskite and ethanol are taken, and the alkyl quaternary ammonium salt is added at 80-100° C. to carry out reflux reaction for 6-10 hours, and after the reaction is completed, the product is washed and dried to obtain the product.

9. The method for preparing the silicon-calcium-potassium-magnesium type soil conditioner according to claim 8, characterized in that: The ratio of the palygorskite, ethanol and alkyl quaternary ammonium salt is 1 g: (10-30) mL: (0.4-0.6) mL.

10. The silicon-calcium-potassium-magnesium type soil conditioner obtained by the preparation method of the silicon-calcium-potassium-magnesium type soil conditioner according to any one of claims 1 to 9.

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