Plant fiber bonding type soil improvement composite material with water retention function and preparation method of plant fiber bonding type soil improvement composite material

Abstract

The invention discloses a plant fiber bonding type soil improvement composite material with a water retention function and a preparation method thereof, and relates to the technical field of ecological management. The plant fiber bonding type soil improvement composite material with the water retention function is prepared from plant fiber; the fertilizer is prepared from the following raw materials in parts by weight: 20 to 30 parts of modified straw fiber, 18 to 25 parts of modified bentonite, 25 to 35 parts of coco coir, 15 to 20 parts of zeolite powder, 12 to 18 parts of potassium humate, 10 to 15 parts of rice husk charcoal, 8 to 12 parts of diatomite, 5 to 8 parts of compound amino acid, 3 to 5 parts of polyglutamic acid, 6 to 8 parts of sodium carboxymethyl starch, 2 to 4 parts of nano silicon dioxide, 4 to 6 parts of calcium magnesium phosphate fertilizer, 2 to 3 parts of xanthan gum and 80 to 120 parts of deionized water. The soil improvement composite material is outstanding in water retention and fertilizer locking capacity, can effectively improve the soil structure and improve the fertility, and meets the requirements of plant maintenance. The raw materials are natural, environment-friendly and wide in source, the preparation process is simple and controllable, and the cost is low. The soil conditioner is stable in particle morphology, convenient to apply, suitable for various soil scenes, environmentally friendly, high in practical value and sufficient in application potential.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of ecological management, in particular to a plant fiber adhesive type soil improvement compound material with water retention function and a preparation method thereof. BACKGROUND

[0002] Currently, the global soil degradation problem is increasingly serious, such as drought, water shortage, soil compaction, fertility decline, poor water and fertilizer retention capacity, which seriously restricts the efficiency of agricultural production and ecological restoration. In arid and semiarid areas, poor soil water holding capacity leads to crop wilting due to water shortage, which requires frequent irrigation, resulting in waste of water resources and increased planting costs; in rainy areas, poor soil aggregate structure easily causes water and soil loss, and nutrients are lost with rainwater, further exacerbating soil infertility.

[0003] Traditional soil improvement methods rely on single materials, such as the use of unmodified straw or bentonite alone, which can improve soil permeability to some extent, but the water retention performance is limited, and the unmodified raw material is easily decomposed and lost, resulting in poor long-term improvement effect. In addition, although some chemical modifiers have a quick effect in the short term, they have the risk of secondary soil pollution, destroy soil microbial communities, and do not meet the needs of ecological and sustainable development.

[0004] At the same time, the existing improvement materials generally have the problem of insufficient adhesion, which is easily dispersed after application and difficult to form a stable soil structure, especially in special scenarios such as slopes, which is easily washed away with rainwater, reducing the improvement efficiency. In addition, most products have single functions, focusing only on water retention or fertilizer increase, and cannot meet the multiple needs of water retention, fertilizer retention, and soil structure improvement, making it difficult to adapt to the repair of different types of degraded soil and the planting needs of crops.

[0005] Therefore, it is a key requirement to develop a composite improvement material with excellent water retention function, stable adhesion, green environmental protection, and long-term improvement of soil fertility, which is a key requirement to solve the current soil degradation problem and promote sustainable agricultural development and ecological restoration. SUMMARY

[0006] In view of the deficiencies of the prior art, the present application provides a plant fiber adhesive type soil improvement compound material with water retention function and a preparation method thereof, which solves the problems of weak water retention capacity, short-term improvement effect, single function and easy soil pollution or loss of traditional soil improvement materials.

[0007] To achieve the above purpose, the present application is realized by the following technical scheme: A plant fiber-bonded soil amendment compound with water retention function comprises the following raw materials in parts by weight: 20-30 parts modified straw fiber, 18-25 parts modified bentonite, 25-35 parts coconut coir, 15-20 parts zeolite powder, 12-18 parts potassium humate, 10-15 parts rice husk charcoal, 8-12 parts diatomaceous earth, 5-8 parts compound amino acids, 3-5 parts polyglutamic acid, 6-8 parts sodium carboxymethyl starch, 2-4 parts nano silica, 4-6 parts calcium magnesium phosphate fertilizer, 2-3 parts xanthan gum, and 80-120 parts deionized water.

[0008] Furthermore, the modified straw fiber is prepared using the following specific steps: A1. Take dried straw fiber and pulverize it to 40-60 mesh. Add 8-12% sodium hydroxide solution and stir at 60-70℃ and 300-400 rpm for 2-3 hours to break down the straw fiber cell walls, increase porosity, and provide reaction sites for subsequent oxidation and grafting. After the reaction, filter and wash until neutral, add deionized water to disperse, and then add 30% hydrogen peroxide and ferrous sulfate in sequence. Stir at 45-55℃ and 250-300 rpm, monitoring the redox potential until it reaches 450-480 mV. Stop the reaction. Hydrogen peroxide and ferrous sulfate synergistically oxidize the product, introducing oxygen-containing functional groups to enhance hydrophilicity. Immediately add ascorbic acid and stir for 30 minutes to terminate the oxidation reaction. Wash the product with deionized water 3-4 times, filter and collect the filter cake. Add acrylic acid and acrylamide, adjust the pH to 5-6 with 5% sodium hydroxide solution, then heat to 75-85℃ and add ammonium persulfate. Stir and react for 3-4 hours. Acrylic acid and acrylamide graft to form a high molecular weight water-absorbing chain, enhancing water retention capacity. After filtration, vacuum dry at 60℃ to constant weight to obtain the first modified straw fiber. A2. Take the first modified straw fiber, add anhydrous ethanol and silane coupling agent KH-550, and stir at 250-300 r / min for 2-2.5 h under nitrogen protection at 50-60℃. The silane coupling agent KH-550 improves the compatibility of the fiber with organic components, and the nitrogen protection prevents oxidation. Then add 1-2% acetic acid solution and chitosan, and keep the reaction at 40-50℃ for 1.5-2 h. Chitosan improves the biocompatibility of the fiber. Continue to add 25% glutaraldehyde, and stir at 35-45℃ for 1-1.5 h. Glutaraldehyde achieves cross-linking and curing. Then add 1% sodium borohydride solution for reduction for 30 min, and perform color development with 0.1% ninhydrin ethanol solution. After no purple color appears, wash the product and vacuum dry at 55℃ to obtain the second modified straw fiber. A3. Take the second batch of modified straw fiber, add deionized water and ultrasonically disperse for 30 min. Slowly add a 10% sodium silicate solution and dropwise add 5% hydrochloric acid to adjust the pH to 3-4. Stir at 50-60℃ and 250-300 r / min for 1-1.5 h. Sodium silicate forms a siliceous layer on the fiber surface to enhance mechanical strength. Then add potassium humate and heat to 65-75℃ for 2-2.5 h. Potassium humate enhances fertilizer retention capacity. Then add hexadecyltrimethylammonium bromide and octadecyltrimethoxysilane and stir at 70-80℃ for 1-1.5 h to optimize the binding of fiber and soil particles. After the reaction, filter and wash until there is no turbidity when tested with silver nitrate to ensure no chloride ion residue. Dry the product under vacuum at 60℃ and then pulverize to 80-100 mesh to obtain modified straw fiber.

[0009] Furthermore, the modified bentonite is prepared using the following specific steps: B1. Take bentonite and crush it to 100-120 mesh. Add a 6-8% (w / w) hydrochloric acid-sulfuric acid mixed acid and stir at 70℃ and 250-300 r / min for 2 hours. The mixed acid removes impurities from the bentonite and expands the interlayer spacing, thereby increasing the adsorption capacity. After the reaction, filter and wash until the pH of the filtrate is 5-6. Add a 5-8% (w / w) calcium chloride solution and stir at 60-70℃ and 250-300 r / min for 2-2.5 hours. Calcium chloride replaces interlayer ions and enhances the adsorption and locking ability. Then add polyethylene glycol 600 and heat to 75-85℃ and stir for 2.5-3 hours to improve dispersibility and prevent agglomeration. After the reaction, filter and dry the product at 70℃ to constant weight to obtain the first modified bentonite. B2. Take the first-modified bentonite, add deionized water and ultrasonically disperse for 40 min, then add sodium dodecylbenzenesulfonate and triethanolamine, and stir at 65-75℃ and 300-350 r / min for 2-2.5 h. Sodium dodecylbenzenesulfonate and triethanolamine achieve organic coating, improving compatibility with organic raw materials. Next, add sodium alginate, adjust the pH to 7.5-8.5 with 3% sodium hydroxide, and stir at 55-65℃ and 250-300 r / min for 1.5-2 h to enhance adhesion and water retention. Then add disodium ethylenediaminetetraacetate and stir at 50-60℃ for 1-1.5 h. Disodium ethylenediaminetetraacetate chelates heavy metal ions, improving soil safety. After the reaction, filter and dry the product at 65℃ to constant weight to obtain the second-modified bentonite. B3. Take the second modified bentonite, add a 10-15% potassium dihydrogen phosphate solution, stir at 70-80℃ and 250-300 r / min for 2-2.5 h to supplement phosphorus and potassium nutrients and achieve the combination of nutrients and adsorption carrier; then add a 0.5% sodium tripolyphosphate solution, stir at 60-70℃ for 1-1.5 h to optimize dispersion stability; then add deionized water and graphene oxide, ultrasonically disperse completely, and stir at 55-65℃ for 1.5-2 h to enhance the structural stability and bioactivity of bentonite; after the reaction is completed, filter, dry the product at 75℃ and pulverize to 100-120 mesh to obtain modified bentonite.

[0010] Furthermore, the total amino acid content of the compound amino acid is ≥40%, ensuring sufficient replenishment of the amino acid nutrition required by plants and promoting root development and nutrient absorption; the polyglutamic acid has a molecular weight of 1-3 million, and polyglutamic acid in this molecular weight range can form a stable polymer network, effectively locking in water and delaying nutrient release; the calcium magnesium phosphate fertilizer contains P2O5 ≥18%, CaO ≥30%, and MgO ≥10%, and sufficient phosphorus, calcium, and magnesium elements can improve the soil nutrient structure and help crops improve photosynthesis and stress resistance.

[0011] Furthermore, the viscosity of the xanthan gum at 25°C is 12000-15000 mPa·s. This suitable viscosity ensures that xanthan gum and sodium carboxymethyl starch synergistically enhance adhesion and improve particle stability. The degree of substitution of the sodium carboxymethyl starch is 0.8-1.2. Sodium carboxymethyl starch in this substitution range has excellent bonding performance and can help adjust the viscosity of the adhesive liquid, ensuring uniform mixing.

[0012] Furthermore, the viscosity of the xanthan gum at 25°C is 12000-15000 mPa·s. This suitable viscosity ensures that xanthan gum and sodium carboxymethyl starch synergistically enhance adhesion and improve particle stability. The degree of substitution of the sodium carboxymethyl starch is 0.8-1.2. Sodium carboxymethyl starch in this substitution range has excellent bonding performance and can help adjust the viscosity of the adhesive liquid, ensuring uniform mixing.

[0013] Furthermore, the ratio of dried straw fiber, sodium hydroxide solution, deionized water, hydrogen peroxide, ferrous sulfate, ascorbic acid, acrylic acid, acrylamide, and ammonium persulfate in A1 is 100g: 400-500ml: 300-350ml: 20-30ml: 5-8g: 0.04-0.06g: 15-20g: 8-12g: 0.8-1.2g.

[0014] Furthermore, the ratio of the first modified straw fiber, anhydrous ethanol, silane coupling agent KH-550, acetic acid solution, chitosan, glutaraldehyde, and sodium borohydride solution in A2 is 100g: 300-350ml: 8-12ml: 200-250ml: 6-10g: 1.0-1.5ml: 18-25ml.

[0015] Furthermore, the ratio of the amount of the second modified straw fiber, deionized water, sodium silicate solution, potassium humate, hexadecyltrimethylammonium bromide, and octadecyltrimethoxysilane in A3 is 100g: 400-450ml: 30-40ml: 12-18g: 1-2g: 0.5-1g.

[0016] Furthermore, the ratio of bentonite, hydrochloric acid-sulfuric acid mixture, calcium chloride solution, and polyethylene glycol 600 in B1 is 100g: 350-400ml: 300-350ml: 15-20g.

[0017] Furthermore, the ratio of the first modified bentonite, deionized water, sodium dodecylbenzenesulfonate, triethanolamine, sodium alginate, and disodium EDTA in B2 is 100g: 400-450ml: 10-15g: 5-8g: 5-8g: 6-10g.

[0018] Furthermore, the ratio of the amount of the second modified bentonite, potassium dihydrogen phosphate solution, sodium tripolyphosphate solution, deionized water, and graphene oxide in B3 is 100g: 350-400ml: 8-12ml: 300-350ml: 0.5-1.5g.

[0019] Furthermore, in the hydrochloric acid-sulfuric acid mixed acid B1, the volume ratio of hydrochloric acid to sulfuric acid is 3:1. This ratio balances the characteristics of both, enabling efficient impurity removal through hydrochloric acid while fully activating the crystal lattice with sulfuric acid. This avoids the problems of incomplete impurity removal or excessive lattice erosion caused by single-acid modification, ultimately achieving a synergistic improvement in the adsorption performance and structural stability of bentonite.

[0020] A method for preparing a plant fiber-based soil amendment compound with water retention function includes the following steps: S1. Crush coconut coir, potassium humate, rice husk charcoal, diatomaceous earth, calcium magnesium phosphate fertilizer, sodium carboxymethyl starch, nano silica, and xanthan gum to 100-120 mesh to improve reaction and adsorption efficiency; pass zeolite powder through a 200-300 mesh sieve to enhance nutrient adsorption and slow release effect; dry all raw materials at 60℃ for 4 hours to remove moisture and prevent mold growth during storage and from affecting subsequent mixing and granulation. S2. Add 20-30 parts of modified straw fiber, 18-25 parts of modified bentonite, 15-20 parts of zeolite powder, 8-12 parts of diatomaceous earth, and 2-4 parts of nano-silica to the mixer. Adjust the speed to 300-350 r / min and mix at room temperature for 35-45 min. This speed and time ensure that the porous raw materials such as modified straw fiber and zeolite powder are fully mixed with the inorganic raw materials without damaging the porous structure, so as to obtain porous mixed powder A. Add 25-35 parts coconut coir, 12-18 parts potassium humate, 10-15 parts rice husk charcoal, and 4-6 parts calcium magnesium phosphate fertilizer to mixed powder A, keep them unchanged, and continue mixing for 25-35 minutes to avoid premature over-adsorption of nutrients and achieve uniform distribution of organic matter and nutrients, thus obtaining organic matter-nutrient composite powder B. S3. In a separate container, add 6-8 parts sodium carboxymethyl starch, 2-3 parts xanthan gum, 3-5 parts polyglutamic acid, and 80-120 parts deionized water. Stir and dissolve at 75-85℃ and 400-450 r / min for 40-50 minutes to prepare an adhesive liquid with a viscosity of 5000-8000 mPa·s. Spray the adhesive liquid evenly into the mixed powder B through a sprayer at a pressure of 0.35-0.5 MPa, ensuring that the adhesive liquid evenly covers the powder. At the same time, add 5-8 parts of the composite amino acid in two batches to avoid amino acid agglomeration and ensure uniform dispersion. Adjust the mixer temperature to 50-55℃ and increase the speed to 380-420 r / min, mix for 70-90 minutes to promote the tight bonding between the adhesive liquid and the powder, and obtain the composite material. S4. Feed the composite material into a twin-screw granulator, adjust the die orifice diameter to 3-5mm, and granulate to obtain particles with a length of 4-6mm. Feed the particles into a dryer at a temperature of 55-65℃ and an airflow rate of 1.2-1.5m / s for 3-4 hours to quickly remove surface free water at a low temperature. Then raise the temperature to 70-75℃, with an airflow rate of 1.0-1.2m / s, and dry for 1.5-2 hours for medium-temperature deep dehydration. Continue to adjust the temperature to 60-65℃, with an airflow rate of 0.8-1.0m / s, and dry for 0.5-1 hours to cool and balance the moisture content, avoiding damage to heat-sensitive components and particle cracking due to high temperature. After drying, feed the particles into a cooler and air-cool them to below 30℃ at room temperature to prevent internal stress caused by sudden cooling, thus obtaining a plant fiber-bonded soil amendment composite material with water retention function.

[0021] Furthermore, the composite amino acid in S3 is added in two parts. The first part is when the adhesive liquid is sprayed to 50% concentration, adding 60% of the total amount. The second part is when the remaining 40% is added after the spraying is completed. After both additions, the mixture is stirred for 15-20 minutes.

[0022] Furthermore, in S4, the screw speed of the twin-screw granulator is adjusted to 180-220 r / min. During the granulation process, nitrogen gas at a temperature of 30-40℃ is introduced into the barrel at a rate of 0.8-1.2 L / min. Nitrogen gas isolates the raw materials from air to prevent oxidation, and stable speed ensures granulation quality.

[0023] This invention provides a plant fiber-bonded soil amendment compound with water retention function and its preparation method, which has the following beneficial effects: 1. The composite material of this invention, through the synergistic effect of the porous structure of modified straw fiber and the adsorption properties of modified bentonite, forms a stable water-locking and fertilizer-retaining system. It can efficiently store water and adsorb soil nutrients, reducing water evaporation and nutrient loss. In arid regions, it can reduce irrigation frequency and save water resources; in rainy regions, it can reduce soil erosion and nutrient leaching, preventing soil depletion. Simultaneously, components such as potassium humate and calcium magnesium phosphate in the material can slowly release nutrients, providing a long-term nutritional supply for crop growth. It is suitable for various degraded soil scenarios such as arid, barren, and sloping land, solving the common problem of weak water and fertilizer retention capacity in different regions.

[0024] 2. The composite binding system formed by sodium carboxymethyl starch, xanthan gum, and polyglutamic acid in the material allows the functional components to bind tightly and adhere effectively to soil particles, preventing material dispersion and loss due to wind and rain erosion after application. This is especially suitable for easily eroded soils such as slopes and sandy areas. Simultaneously, the binding property gives the material a stable particle shape, allowing it to continue to function in the soil after application. This reduces the problems of easy decomposition and frequent reapplication required by traditional loose soil amendments, extending the soil amendment cycle, reducing long-term amendment costs, and ensuring stable and lasting amendment effects.

[0025] 3. This invention uses natural agricultural waste such as straw fiber, coconut coir, and rice husk charcoal as core raw materials, achieving both resource utilization of waste and reducing environmental pollution, while avoiding secondary pollution of the soil by chemical amendments. The modified raw materials have good soil compatibility, promoting soil microbial activity, improving soil aggregate structure, enhancing soil aeration and permeability, and alleviating soil compaction. Long-term application can gradually restore soil ecological functions, build a healthy soil environment, meet the needs of sustainable agricultural development and ecological restoration, and balance practical value with ecological benefits.

[0026] 4. Compared to traditional single-function soil amendment products, the compound material of this invention integrates water retention, fertilizer retention, soil structure improvement, and soil stabilization, eliminating the need for multiple products to be applied in separate steps. This simplifies the operation process and reduces application costs for farmers and ecological restoration projects. Furthermore, the crushing, mixing, and granulation steps in the preparation process are scientifically controllable, enabling large-scale production. The granule shape facilitates storage, transportation, and mechanized application, making it suitable for agricultural planting and ecological restoration projects of different scales, thus improving the product's applicability and application efficiency. Detailed Implementation

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1: Preparation of a plant fiber-bonded soil amendment compound with water retention function. The specific preparation steps are as follows: S1. Crush coconut coir, potassium humate, rice husk charcoal, diatomaceous earth, calcium magnesium phosphate fertilizer, sodium carboxymethyl starch, nano silica, and xanthan gum to 100 mesh; pass zeolite powder through a 200 mesh sieve; dry all raw materials at 60℃ for 4 hours for later use. S2. Add 20 parts modified straw fiber, 18 parts modified bentonite, 15 parts zeolite powder, 8 parts diatomite, and 2 parts nano silica to the mixer, adjust to 300 r / min, mix at room temperature for 35 min to obtain porous mixed powder A. Add 25 parts coconut coir, 12 parts potassium humate, 10 parts rice husk charcoal, and 4 parts calcium magnesium phosphate fertilizer to mixed powder A, keep the mixture unchanged, and continue mixing for 25 minutes to obtain organic matter-nutrient composite powder B. S3. In a separate container, add 6 parts sodium carboxymethyl starch, 2 parts xanthan gum, 3 parts polyglutamic acid, and 80 parts deionized water. Stir at 75°C and 400 r / min for 40 min to dissolve and prepare an adhesive liquid with a viscosity of 5000 mPa·s. Spray the adhesive liquid evenly into the mixed powder B through a sprayer at a pressure of 0.35 MPa. At the same time, add 5 parts of composite amino acids in two batches, stirring for 15 min after each addition. Adjust the mixer temperature to 50°C, increase the speed to 380 r / min, and mix for 70 min to obtain the composite material. S4. The composite material is fed into a twin-screw granulator, with the screw speed adjusted to 180 r / min. During granulation, nitrogen gas at 30°C is introduced into the barrel at a rate of 0.8 L / min. The die orifice diameter is adjusted to 3 mm, and the granules are cut to obtain particles with a length of 4 mm. The particles are then fed into a dryer at 55°C and a ventilation rate of 1.2 m / s for 3 hours. The temperature is then increased to 70°C and the ventilation rate is 1.0 m / s for 1.5 hours. The temperature is then further adjusted to 60°C and the ventilation rate is 0.8 m / s for 0.5 hours. After drying, the particles are fed into a cooler and cooled to below 30°C at room temperature to obtain a plant fiber-bonded soil amendment composite material with water retention function.

[0029] Example 2: Preparation of a plant fiber-bonded soil amendment compound with water retention function. The specific preparation steps are as follows: S1. Crush coconut coir, potassium humate, rice husk charcoal, diatomaceous earth, calcium magnesium phosphate fertilizer, sodium carboxymethyl starch, nano silica, and xanthan gum to 120 mesh; pass zeolite powder through a 300 mesh sieve; dry all raw materials at 60℃ for 4 hours for later use. S2. Add 30 parts modified straw fiber, 25 parts modified bentonite, 20 parts zeolite powder, 12 parts diatomite, and 4 parts nano silica to the mixer, adjust to 350 r / min, and mix at room temperature for 45 min to obtain porous mixed powder A. Add 35 parts coconut coir, 18 parts potassium humate, 15 parts rice husk charcoal, and 6 parts calcium magnesium phosphate fertilizer to mixed powder A, keep the mixture unchanged, and continue mixing for 35 minutes to obtain organic matter-nutrient composite powder B. S3. In a separate container, add 8 parts sodium carboxymethyl starch, 3 parts xanthan gum, 5 parts polyglutamic acid, and 120 parts deionized water. Stir at 85°C and 450 r / min for 50 min to dissolve and prepare an adhesive liquid with a viscosity of 8000 mPa·s. Spray the adhesive liquid evenly into the mixed powder B through a sprayer at a pressure of 0.5 MPa. At the same time, add 8 parts of composite amino acids in two batches, stirring for 20 min after each addition. Adjust the mixer temperature to 55°C, increase the speed to 420 r / min, and mix for 90 min to obtain the composite material. S4. The composite material is fed into a twin-screw granulator, and the screw speed is adjusted to 220 r / min. During the granulation process, nitrogen gas at 40℃ is introduced into the barrel at a rate of 1.2 L / min. The die orifice diameter is adjusted to 5 mm, and the pellets are cut to obtain 6 mm long particles. The particles are then fed into a dryer at 65℃ and a ventilation rate of 1.5 m / s for 4 hours. The temperature is then increased to 75℃ and the ventilation rate is 1.2 m / s for 2 hours. The temperature is then adjusted to 65℃ and the ventilation rate is 1.0 m / s for 1 hour. After drying, the particles are fed into a cooler and cooled to below 30℃ at room temperature to obtain a plant fiber-bonded soil amendment composite material with water retention function.

[0030] Example 3: Preparation of a plant fiber-bonded soil amendment compound with water retention function. The specific preparation steps are as follows: S1. Crush coconut coir, potassium humate, rice husk charcoal, diatomaceous earth, calcium magnesium phosphate fertilizer, sodium carboxymethyl starch, nano silica, and xanthan gum to 110 mesh; pass zeolite powder through a 250 mesh sieve; dry all raw materials at 60℃ for 4 hours for later use. S2. Add 25 parts modified straw fiber, 21 parts modified bentonite, 17 parts zeolite powder, 10 parts diatomaceous earth, and 3 parts nano silica to the mixer, adjust to 320 r / min, mix at room temperature for 40 min to obtain porous mixed powder A. Add 30 parts coconut coir, 15 parts potassium humate, 12 parts rice husk charcoal, and 5 parts calcium magnesium phosphate fertilizer to mixed powder A, keep the mixture constant, and continue mixing for 30 minutes to obtain organic matter-nutrient composite powder B. S3. In a separate container, add 7 parts sodium carboxymethyl starch, 2.5 parts xanthan gum, 4 parts polyglutamic acid, and 100 parts deionized water. Stir at 80℃ and 430 r / min for 45 min to dissolve and prepare an adhesive liquid with a viscosity of 6500 mPa·s. Spray the adhesive liquid evenly into the mixed powder B through a sprayer at a pressure of 0.4 MPa. At the same time, add 6 parts of composite amino acids in two batches, and keep stirring for 17 min after each addition. Adjust the temperature of the mixer to 52℃, increase the speed to 400 r / min, and mix for 80 min to obtain the composite material. S4. The composite material is fed into a twin-screw granulator, and the screw speed is adjusted to 200 r / min. During the granulation process, nitrogen gas at 35°C is introduced into the barrel at a rate of 1 L / min. The die orifice diameter is adjusted to 4 mm, and the granules are cut to obtain particles with a length of 5 mm. The particles are then fed into a dryer at 60°C and a ventilation rate of 1.3 m / s for 3.5 h. The temperature is then increased to 72°C and the ventilation rate is 1.1 m / s for 1.7 h. The temperature is then further adjusted to 62°C and the ventilation rate is 0.9 m / s for 0.7 h. After drying, the particles are fed into a cooler and cooled to below 30°C at room temperature to obtain a plant fiber-bonded soil amendment composite material with water retention function.

[0031] Example 4: Preparation of modified straw fiber. The specific preparation steps are as follows: A1. Take 100g of dried straw fiber and crush it to 40 mesh. Add 400ml of 8% sodium hydroxide solution and stir at 60℃ and 300r / min for 2h. After the reaction, filter and wash until neutral. Add 300ml of deionized water to disperse. Add 20ml of 30% hydrogen peroxide and 5g of ferrous sulfate in sequence. Stir at 45℃ and 250r / min. Stop when the redox potential reaches 450mV. Immediately add 0.04g of ascorbic acid and stir for 30min. Wash the product with deionized water 3 times. After filtration, collect the filter cake. Add 15g of acrylic acid and 8g of acrylamide. Adjust the pH to 5 with 5% sodium hydroxide solution. Then heat to 75℃ and add 0.8g of ammonium persulfate. Stir and react for 3h. After filtration, vacuum dry at 60℃ to constant weight to obtain the first modified straw fiber. A2. Take 100g of the first modified straw fiber, add 300ml of anhydrous ethanol and 8ml of silane coupling agent KH-550, and stir at 250r / min for 2h under nitrogen protection at 50℃; then add 200ml of 1% acetic acid solution and 6g of chitosan, and keep the reaction at 40℃ for 1.5h; continue to add 1.0ml of 25% glutaraldehyde, and stir at 35℃ for 1h; then add 18ml of 1% sodium borohydride solution for reduction for 30min, and perform color development with 0.1% ninhydrin ethanol solution. After no purple color appears, wash the product and dry it under vacuum at 55℃ to obtain the second modified straw fiber. A3. Take 100g of the second modified straw fiber, add 400ml of deionized water and ultrasonically disperse for 30min. Slowly add 30ml of 10% sodium silicate solution, add 5% hydrochloric acid to adjust the pH to 3, and stir at 50℃ and 250r / min for 1h. Then add 12g of potassium humate and heat to 65℃ for 2h. Then add 1g of hexadecyltrimethylammonium bromide and 0.5g of octadecyltrimethoxysilane and stir at 70℃ for 1h. After the reaction is complete, filter and wash until there is no turbidity when tested with silver nitrate. Dry the product under vacuum at 60℃ and pulverize to 80 mesh to obtain modified straw fiber.

[0032] Example 5: Preparation of modified straw fiber. The specific preparation steps are as follows: A1. Take 100g of dried straw fiber and crush it to 60 mesh. Add 500ml of 12% sodium hydroxide solution and stir at 70℃ and 400r / min for 3h. After the reaction, filter and wash until neutral. Add 350ml of deionized water to disperse. Add 30ml of 30% hydrogen peroxide and 8g of ferrous sulfate in sequence. Stir at 55℃ and 300r / min. Stop when the redox potential reaches 480mV. Immediately add 0.06g of ascorbic acid and stir for 30min. Wash the product with deionized water 4 times. After filtration, collect the filter cake. Add 20g of acrylic acid and 12g of acrylamide. Adjust the pH to 6 with 5% sodium hydroxide solution. Then heat to 85℃ and add 1.2g of ammonium persulfate. Stir and react for 4h. After filtration, vacuum dry at 60℃ to constant weight to obtain the first modified straw fiber. A2. Take 100g of the first modified straw fiber, add 350ml of anhydrous ethanol and 12ml of silane coupling agent KH-550, and stir at 300r / min for 2.5h under nitrogen protection at 60℃. Then add 250ml of 2% acetic acid solution and 10g of chitosan, and keep the reaction at 50℃ for 2h. Continue to add 1.5ml of 25% glutaraldehyde, and stir at 45℃ for 1.5h. Then add 25ml of 1% sodium borohydride solution for reduction for 30min, and perform color development with 0.1% ninhydrin ethanol solution. After no purple color appears, wash the product and dry it under vacuum at 55℃ to obtain the second modified straw fiber. A3. Take 100g of the second modified straw fiber, add 450ml of deionized water and ultrasonically disperse for 30min. Slowly add 40ml of 10% sodium silicate solution, add 5% hydrochloric acid to adjust the pH to 4, and stir at 60℃ and 300r / min for 1.5h. Then add 18g of potassium humate and heat to 75℃ for 2.5h. Then add 2g of hexadecyltrimethylammonium bromide and 1g of octadecyltrimethoxysilane and stir at 80℃ for 1.5h. After the reaction is complete, filter and wash until there is no turbidity when tested with silver nitrate. Dry the product under vacuum at 60℃ and pulverize it to 100 mesh to obtain the modified straw fiber.

[0033] Example 6: Preparation of modified bentonite. The specific preparation steps are as follows: B1. Take 100g of bentonite and crush it to 100 mesh. Add 350ml of 6% hydrochloric acid-sulfuric acid mixture and stir at 70℃ and 250r / min for 2h. After the reaction is complete, filter and wash until the pH of the filtrate is 5. Add 300ml of 5% calcium chloride solution and stir at 60℃ and 250r / min for 2h. Then add 15g of polyethylene glycol 600, heat to 75℃ and stir for 2.5h. After the reaction is complete, filter and dry the product at 70℃ to constant weight to obtain the first modified bentonite. B2. Take 100g of the first-modified bentonite, add 400ml of deionized water and ultrasonically disperse for 40min. Add 10g of sodium dodecylbenzenesulfonate and 5g of triethanolamine, and stir at 65℃ and 300r / min for 2h. Then add 5g of sodium alginate, adjust the pH to 7.5 with 3% sodium hydroxide, and stir at 55℃ and 250r / min for 1.5h. Then add 6g of disodium ethylenediaminetetraacetate, and stir at 50℃ for 1h. After the reaction is complete, filter and dry the product at 65℃ to constant weight to obtain the second-modified bentonite. B3. Take 100g of the second modified bentonite, add 350ml of 10% potassium dihydrogen phosphate solution, and stir at 70℃ and 250r / min for 2h. Then add 8ml of 0.5% sodium tripolyphosphate solution, stir at 60℃ for 1h, then add 300ml of deionized water and 0.5g of graphene oxide. After ultrasonic dispersion, stir at 55℃ for 1.5h. After the reaction is complete, filter, dry the product at 75℃ and pulverize to 100 mesh to obtain modified bentonite.

[0034] Example 7: Preparation of modified bentonite. The specific preparation steps are as follows: B1. Take 100g of bentonite and crush it to 120 mesh. Add 400ml of 8% hydrochloric acid-sulfuric acid mixture and stir at 70℃ and 300r / min for 2h. After the reaction is complete, filter and wash until the pH of the filtrate is 6. Add 350ml of 8% calcium chloride solution and stir at 70℃ and 300r / min for 2.5h. Then add 20g of polyethylene glycol 600, heat to 85℃ and stir for 3h. After the reaction is complete, filter and dry the product at 70℃ to constant weight to obtain the first modified bentonite. B2. Take 100g of the first-modified bentonite, add 450ml of deionized water and ultrasonically disperse for 40min. Add 15g of sodium dodecylbenzenesulfonate and 8g of triethanolamine, and stir at 75℃ and 350r / min for 2.5h. Then add 8g of sodium alginate, adjust the pH to 8.5 with 3% sodium hydroxide, and stir at 65℃ and 300r / min for 2h. Then add 10g of disodium ethylenediaminetetraacetate, and stir at 60℃ for 1.5h. After the reaction is complete, filter and dry the product at 65℃ to constant weight to obtain the second-modified bentonite. B3. Take 100g of the second modified bentonite, add 400ml of 15% potassium dihydrogen phosphate solution, and stir at 80℃ and 300r / min for 2.5h. Then add 12ml of 0.5% sodium tripolyphosphate solution, stir at 70℃ for 1.5h, then add 350ml of deionized water and 1.5g of graphene oxide. After ultrasonic dispersion, stir at 65℃ for 2h. After the reaction is complete, filter, dry the product at 75℃ and pulverize to 120 mesh to obtain modified bentonite.

[0035] Comparative Example 1: A plant fiber-based soil amendment compound with water retention function was prepared. The specific preparation steps are as follows: The remaining steps remain the same, except that the modified straw fiber prepared in Example 4 used in Example 3 is replaced with unmodified straw fiber to prepare a plant fiber adhesive soil amendment compound with water retention function.

[0036] Comparative Example 2: A plant fiber-based soil amendment compound with water retention function was prepared. The specific preparation steps are as follows: The remaining steps remain the same, except that the modified bentonite prepared in Example 7 used in Example 3 is replaced with unmodified bentonite to prepare a plant fiber adhesive soil amendment compound with water retention function.

[0037] Comparative Example 3: A plant fiber-based soil amendment compound with water retention function was prepared. The specific preparation steps are as follows: The remaining steps remain unchanged, except that the modified straw fiber prepared in Example 4 used in Example 3 is replaced with unmodified straw fiber, and the modified bentonite is replaced with unmodified bentonite, so as to prepare a plant fiber adhesive soil amendment compound with water retention function.

[0038] Performance testing Test item Example 1 Example 2 Example 3 Comparative Example 1 Comparative Example 2 Comparative Example 3 Saturation water absorption rate (%) 425 458 482 312 335 286 24h water retention rate (%) 78.5 82.3 86.7 56.2 59.8 51.3 Soil aggregate stability (>0.25mm aggregate content increase rate, %) 35.8 39.2 43.5 22.6 24.3 18.9 Nutrient slow-release rate (28d, %) 68.3 72.5 76.8 45.7 48.2 41.5 Adhesion stability (residual rate after simulated rainfall erosion, %) 85.2 88.6 92.3 62.4 65.8 58.7 Soil pH adjustment range (30d after application, ΔpH) 0.35 0.42 0.48 0.21 0.25 0.18 Performance test results show that the composite materials of Examples 1-3 are significantly superior to those of Comparative Examples 1-3 using unmodified straw fiber, unmodified bentonite, and both unmodified materials in all key indicators: saturated water absorption rate reaches 425%-482%, 24h water retention rate is 78.5%-86.7%, demonstrating outstanding water retention capacity; soil aggregate structure stability (>0.25mm aggregate content increase rate 35.8%-43.5%) and adhesion stability (residual rate after simulated rainfall washout 85.2%-92.3%) are excellent, effectively preventing material loss and improving soil structure; 28d nutrient slow release rate is 68.3%-76.8%, providing long-term nutrient supply, and the soil pH adjustment range is reasonable (ΔpH 0.35-0.48), with overall comprehensive performance better suited to soil improvement needs.

[0039] The above description is merely an example and illustration of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A plant fiber-based soil amendment compound with water retention function, characterized in that: It contains the following raw materials by weight: 20-30 parts modified straw fiber, 18-25 parts modified bentonite, 25-35 parts coconut coir, 15-20 parts zeolite powder, 12-18 parts potassium humate, 10-15 parts rice husk charcoal, 8-12 parts diatomaceous earth, 5-8 parts compound amino acids, 3-5 parts polyglutamic acid, 6-8 parts sodium carboxymethyl starch, 2-4 parts nano silica, 4-6 parts calcium magnesium phosphate fertilizer, 2-3 parts xanthan gum, and 80-120 parts deionized water; The modified straw fiber is prepared using the following specific steps: A1. Take dried straw fiber and crush it to 40-60 mesh. Add 8-12% sodium hydroxide solution and stir at 60-70℃ and 300-400 r / min for 2-3 hours. After the reaction, filter and wash until neutral. Add deionized water to disperse. Add 30% hydrogen peroxide and ferrous sulfate in sequence. Stir at 45-55℃ and 250-300 r / min. Stop when the redox potential reaches 450-480 mV. Immediately add ascorbic acid and stir for 30 minutes. Wash the product with deionized water 3-4 times. After filtration, collect the filter cake. Add acrylic acid and acrylamide. Adjust the pH to 5-6 with 5% sodium hydroxide solution. Then raise the temperature to 75-85℃ and add ammonium persulfate. Stir and react for 3-4 hours. After filtration, vacuum dry at 60℃ to constant weight to obtain the first modified straw fiber. A2. Take the first modified straw fiber, add anhydrous ethanol and silane coupling agent KH-550, and stir at 250-300 r / min for 2-2.5 h under nitrogen protection at 50-60℃; then add 1-2% acetic acid solution and chitosan, and keep the reaction at 40-50℃ for 1.5-2 h; continue to add 25% glutaraldehyde, and stir at 35-45℃ for 1-1.5 h; then add 1% sodium borohydride solution for reduction for 30 min, and perform color development with 0.1% ninhydrin ethanol solution. After no purple color appears, wash the product and dry it under vacuum at 55℃ to obtain the second modified straw fiber. A3. Take the second batch of modified straw fiber, add deionized water and ultrasonically disperse for 30 min, slowly add 10% sodium silicate solution, add 5% hydrochloric acid to adjust the pH to 3-4, stir at 50-60℃ and 250-300 r / min for 1-1.5 h; then add potassium humate, heat to 65-75℃ and react for 2-2.5 h; then add hexadecyltrimethylammonium bromide and octadecyltrimethoxysilane, stir at 70-80℃ for 1-1.5 h; after the reaction is complete, filter and wash until there is no turbidity when tested with silver nitrate, dry the product under vacuum at 60℃ and pulverize to 80-100 mesh to obtain modified straw fiber; The modified bentonite is prepared using the following specific steps: B1. Take bentonite and crush it to 100-120 mesh. Add 6-8% hydrochloric acid-sulfuric acid mixed acid and stir at 70℃ and 250-300 r / min for 2 hours. After the reaction is completed, filter and wash until the pH of the filtrate is 5-6. Add 5-8% calcium chloride solution and stir at 60-70℃ and 250-300 r / min for 2-2.5 hours. Then add polyethylene glycol 600, heat to 75-85℃ and stir for 2.5-3 hours. After the reaction is completed, filter and dry the product at 70℃ to constant weight to obtain the first modified bentonite. B2. Take the first modified bentonite, add deionized water and ultrasonically disperse for 40 min, add sodium dodecylbenzenesulfonate and triethanolamine, stir at 65-75℃ and 300-350 r / min for 2-2.5 h; then add sodium alginate, adjust the pH to 7.5-8.5 with 3% sodium hydroxide, stir at 55-65℃ and 250-300 r / min for 1.5-2 h; then add disodium ethylenediaminetetraacetate, stir at 50-60℃ for 1-1.5 h, filter after the reaction, and dry the product at 65℃ to constant weight to obtain the second modified bentonite; B3. Take the second modified bentonite, add a 10-15% potassium dihydrogen phosphate solution, and stir at 70-80℃ and 250-300 r / min for 2-2.5 h; then add a 0.5% sodium tripolyphosphate solution, stir at 60-70℃ for 1-1.5 h, then add deionized water and graphene oxide, and after complete ultrasonic dispersion, stir at 55-65℃ for 1.5-2 h. After the reaction is complete, filter, dry the product at 75℃ and pulverize it to 100-120 mesh to obtain modified bentonite.

2. The plant fiber-bonded soil amendment compound with water retention function according to claim 1, characterized in that: The total amino acid content of the compound amino acid is ≥40%; the molecular weight of the polyglutamic acid is 1-3 million; and the calcium magnesium phosphate fertilizer contains P2O5 ≥18%, CaO ≥30%, and MgO ≥10%.

3. The plant fiber-bonded soil amendment compound with water retention function according to claim 1, characterized in that: The viscosity of the xanthan gum at 25°C is 12000-15000 mPa·s; the degree of substitution of the sodium carboxymethyl starch is 0.8-1.

2.

4. The plant fiber-bonded soil amendment compound with water retention function according to claim 1, characterized in that: The ratio of dried straw fiber, sodium hydroxide solution, deionized water, hydrogen peroxide, ferrous sulfate, ascorbic acid, acrylic acid, acrylamide, and ammonium persulfate in A1 is 100g: 400-500ml: 300-350ml: 20-30ml: 5-8g: 0.04-0.06g: 15-20g: 8-12g: 0.8-1.2g; The ratio of the first modified straw fiber, anhydrous ethanol, silane coupling agent KH-550, acetic acid solution, chitosan, glutaraldehyde, and sodium borohydride solution in A2 is 100g: 300-350ml: 8-12ml: 200-250ml: 6-10g: 1.0-1.5ml: 18-25ml; The ratio of the amount of the second modified straw fiber, deionized water, sodium silicate solution, potassium humate, hexadecyltrimethylammonium bromide, and octadecyltrimethoxysilane in A3 is 100g: 400-450ml: 30-40ml: 12-18g: 1-2g: 0.5-1g.

5. The plant fiber-bonded soil amendment compound with water retention function according to claim 1, characterized in that: The ratio of bentonite, hydrochloric acid-sulfuric acid mixture, calcium chloride solution, and polyethylene glycol 600 in B1 is 100g: 350-400ml: 300-350ml: 15-20g; The ratio of the first modified bentonite, deionized water, sodium dodecylbenzenesulfonate, triethanolamine, sodium alginate, and disodium ethylenediaminetetraacetate in B2 is 100g: 400-450ml: 10-15g: 5-8g: 5-8g: 6-10g. The ratio of the amount of the second modified bentonite, potassium dihydrogen phosphate solution, sodium tripolyphosphate solution, deionized water, and graphene oxide in B3 is 100g: 350-400ml: 8-12ml: 300-350ml: 0.5-1.5g.

6. The plant fiber-bonded soil amendment compound with water retention function according to claim 1, characterized in that: In the hydrochloric acid-sulfuric acid mixture B1, the volume ratio of hydrochloric acid to sulfuric acid is 3:

1.

7. A method for preparing a plant fiber-bonded soil amendment compound with water retention function as described in claim 1, characterized in that: Specifically, it includes the following steps: S1. Crush coconut coir, potassium humate, rice husk charcoal, diatomaceous earth, calcium magnesium phosphate fertilizer, sodium carboxymethyl starch, nano silica, and xanthan gum to 100-120 mesh respectively; pass zeolite powder through a 200-300 mesh sieve; dry all raw materials at 60℃ for 4 hours for later use. S2. Add 20-30 parts of modified straw fiber, 18-25 parts of modified bentonite, 15-20 parts of zeolite powder, 8-12 parts of diatomaceous earth, and 2-4 parts of nano-silica to the mixer, adjust to 300-350 r / min, and mix at room temperature for 35-45 min to obtain porous mixed powder A. Add 25-35 parts coconut coir, 12-18 parts potassium humate, 10-15 parts rice husk charcoal, and 4-6 parts calcium magnesium phosphate fertilizer to mixed powder A, keep the mixture unchanged, and continue mixing for 25-35 minutes to obtain organic matter-nutrient composite powder B. S3. In a separate container, add 6-8 parts sodium carboxymethyl starch, 2-3 parts xanthan gum, 3-5 parts polyglutamic acid, and 80-120 parts deionized water. Stir at 75-85℃ and 400-450 r / min for 40-50 min to dissolve and prepare an adhesive liquid with a viscosity of 5000-8000 mPa·s. The adhesive liquid is sprayed evenly into the mixed powder B through a sprayer at a pressure of 0.35-0.5MPa. At the same time, 5-8 parts of composite amino acids are added in two batches. The temperature of the mixer is adjusted to 50-55℃ and increased to 380-420r / min. The mixture is mixed for 70-90min to obtain the composite material. S4. Feed the composite material into a twin-screw granulator, adjust the die orifice diameter to 3-5mm, and granulate to obtain particles with a length of 4-6mm; feed the particles into a dryer, temperature 55-65℃, ventilation rate 1.2-1.5m / s, dry for 3-4h; then raise the temperature to 70-75℃, ventilation rate 1.0-1.2m / s, dry for 1.5-2h; continue to adjust the temperature to 60-65℃, ventilation rate 0.8-1.0m / s, dry for 0.5-1h; after drying, feed the particles into a cooler, air cool at room temperature to below 30℃, to obtain a plant fiber adhesive soil amendment composite material with water retention function.

8. The method for preparing a plant fiber-bonded soil amendment compound with water retention function according to claim 7, characterized in that: The composite amino acid in S3 is added in two parts. The first part is when the adhesive liquid is sprayed to 50% concentration, adding 60% of the total amount. The second part is when the remaining 40% is added after the spraying is completed. After both additions, the mixture is stirred for 15-20 minutes.

9. The method for preparing a plant fiber-bonded soil amendment compound with water retention function according to claim 7, characterized in that: The screw speed of the twin-screw granulator in S4 is adjusted to 180-220 r / min. During the granulation process, nitrogen gas at a temperature of 30-40℃ is introduced into the barrel at a rate of 0.8-1.2 L / min.