Cotton stalk-based agricultural and forestry water-retaining material and preparation method thereof

Abstract

The application discloses a cotton stalk-based agricultural and forestry water-retaining material and a preparation method thereof, which is obtained by mixing, granulating and preparing carboxymethyl cellulose grafting products, nano-synthetic cellulose linseed gum gel particles and nano-synthetic cellulose calcium alginate fiber powder, and the raw materials are cotton stalks. The application realizes the resource utilization of cotton stalks, and obtains a water-retaining material with high water absorption, slow release, water retention and good mechanical stability. Furthermore, the carboxymethyl cellulose is replaced from sodium salt to potassium salt, so that the ion compatibility and applicability of the water-retaining material in the soil environment are improved.

Description

Technical Field

[0001] This invention belongs to the technical field of agricultural water-retaining materials and high-value utilization of biomass, and relates to a cotton stalk-based agricultural and forestry water-retaining material and its preparation method. Background Technology

[0002] Water resources play an indispensable role in agriculture and forestry. Traditional irrigation methods such as sprinkler, spray, and drip irrigation systems face certain limitations when implemented in specific environments, leading to significant water waste. This is especially true in water-scarce areas where agricultural and forestry irrigation water is scarce, making traditional irrigation methods unsuitable.

[0003] In recent years, water-retaining materials have been increasingly used in agriculture and forestry. These materials can improve soil water retention capacity and reduce evaporation and seepage losses. Their structure contains network-like molecular chains that electrolyze upon contact with water, dissociating into ions with a strong affinity for water, thus exhibiting extremely strong water absorption and retention properties. Water-retaining materials can rapidly absorb hundreds of times their own weight in water and retain a large amount of moisture, while simultaneously expanding in volume to tens or even hundreds of times their original size. When the moisture content in the environment is low, they slowly release the water back into the soil, shrinking back to their original size, repeating this cycle repeatedly, thereby improving soil water retention capacity and soil quality. Furthermore, through their network structure, water-retaining materials can adsorb and fix fertilizer elements in the soil, reducing nutrient loss and promoting plant growth. Therefore, they are widely used in desertification control, agricultural and forestry crop cultivation, and landscaping.

[0004] However, most existing water-retaining materials are derived from petrochemical-based monomers, which are costly and environmentally burdensome, contradicting the green and environmentally friendly concepts of recent years.

[0005] On the other hand, agricultural waste such as cotton stalks is abundant, and direct burning or disposal leads to waste and pollution. Developing highly absorbent and water-retaining materials with cotton stalk cellulose as the backbone would be of great significance for improving water resource utilization efficiency and the resource recovery of agricultural waste. Summary of the Invention

[0006] In view of this, the purpose of the present invention is to provide a cotton stalk-based agroforestry water-retaining material and its preparation method.

[0007] To achieve the above objectives, the present invention provides the following technical solution: A method for preparing a cotton stalk-based agroforestry water-retaining material, the specific steps of which are as follows: S1. First, extract holocellulose from cotton stalks; S2. Using holocellulose as raw material, cellulose is extracted and carboxymethylated to obtain potassium carboxymethyl cellulose CS-CMC-K. Using CS-CMC-K as the backbone, it is grafted and copolymerized with acrylic acid to obtain carboxymethyl cellulose graft product. S3. Using holocellulose as raw material, nano-sized to obtain nano holocellulose. A portion of the nano holocellulose is cross-linked with linseed gum to obtain nano holocellulose linseed gum gel particles. The remaining nano holocellulose is mixed with sodium alginate and calcium chloride to prepare nano holocellulose calcium alginate fiber powder. S4. Finally, mix and granulate the carboxymethyl cellulose graft product, nano-harvest cellulose flaxseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder.

[0008] Preferably, the specific method of step S1 is as follows: S1-1. Crush the cotton stalks, add them to a sulfuric acid solution with 8 to 10 times their weight, let them stand to soak and neutralize, add urea and hexadecyltrimethylammonium bromide, mix them evenly, and obtain a mixture. S1-2. Ultrasonic oscillation treatment, cold storage treatment, centrifugation to collect the precipitate, washing with water, drying to obtain the intermediate product; S1-3. Extract the intermediate product with benzene alcohol, filter to obtain the solid, air dry naturally, pour into a sodium chlorite-acetic acid mixture for bleaching, filter to obtain the solid, dry, and obtain holocellulose.

[0009] More preferably, in step S1-1, the mass concentration of the sulfuric acid solution is 10-15%; the soaking time is 5-7 hours; the pH is neutralized to 7 using a 0.3-0.5% potassium hydroxide solution; and the mass percentages of urea and hexadecyltrimethylammonium bromide in the mixture are 10% and 13%, respectively.

[0010] Further preferably, in steps S1-2, the ultrasonic oscillation treatment conditions are: frequency 35-45kHz, power 400-600W, time 20-30 minutes; the refrigeration treatment conditions are: refrigeration at 4℃ for 12 hours; and the drying conditions are: drying at 45℃ to constant weight.

[0011] Further preferably, in steps S1-3, the extraction conditions for benzene alcohol are as follows: a benzene-ethanol mixed solution with a volume ratio of 2:1 is heated to reflux for 6-8 hours; the sodium chlorite-glacial acetic acid mixture is obtained by mixing equal volumes of a 5-10% sodium chlorite aqueous solution and a 2-5% acetic acid solution; the amount of sodium chlorite-acetic acid mixture used is 2-3 times the mass of the intermediate product, and the bleaching time is 3-5 minutes; the drying conditions are: drying at 45°C to constant weight.

[0012] Preferably, in step S2, the method for extracting cellulose is as follows: add hemicellulose to a potassium hydroxide solution of 6 to 8 times its weight and stir at 75 to 85°C for 1 to 2 hours to dissolve the hemicellulose, filter to obtain the solid, wash with water until neutral, and dry at 45°C to constant weight to obtain cellulose.

[0013] Preferably, in step S2, the carboxymethylation method is as follows: First, cellulose is stirred and dispersed in 6-8 times its weight of a 90% isopropanol aqueous solution. Then, a 30% hydrogen peroxide solution and a 50% potassium hydroxide solution are added, and the mixture is stirred at 20-30°C for 2-3 hours. Next, a 50% chloroacetic acid solution is added, and the mixture is stirred for another 30 minutes. The temperature is then gradually increased to 45°C, 60°C, and 75°C, and the mixture is stirred for 30 minutes, 30 minutes, and 90 minutes respectively to complete the etherification reaction. Finally, the pH is adjusted to neutral using a 10% acetic acid solution, the solid is filtered, washed three times with anhydrous ethanol, dried at 70°C, and pulverized to obtain the CS-CMC-K. The molar ratio of glucose units in cellulose, hydrogen peroxide in hydrogen peroxide solution, potassium hydroxide in potassium hydroxide solution, and chloroacetic acid in chloroacetic acid solution is 1:2-3:2-3:2-3.

[0014] Preferably, in step S2, the preparation method of the carboxymethyl cellulose graft product is as follows: CS-CMC-K is stirred and dispersed in 8 to 10 times its weight of deionized water, and allowed to stand for 24 hours to fully swell; then, in an ice-water bath, a 20% potassium hydroxide solution is added dropwise to acrylic acid while stirring, slowly neutralizing the acrylic acid to a neutralization degree of 70 to 80%, obtaining a partially neutralized acrylate solution; then, the fully swollen CS-CMC-K is mixed with the partially neutralized acrylate solution, followed by the addition of N,N'-methylenebisacrylamide and potassium persulfate, and the graft copolymerization crosslinking reaction is carried out under nitrogen protection by heating and stirring. After the reaction is completed, the product is allowed to stand to initially solidify, and then removed. It is washed with anhydrous ethanol and water alternately to remove unreacted monomers and impurities, dried at 60°C to constant weight, and pulverized to obtain the carboxymethyl cellulose graft product.

[0015] In a further preferred embodiment, the mass ratio of CS-CMC-K to acrylic acid is 1:5-6, and the amounts of N,N'-methylenebisacrylamide and potassium persulfate are 0.1-0.2% and 0.3-0.4% of the mass of CS-CMC-K, respectively. N,N'-methylenebisacrylamide and potassium persulfate are added after being prepared into an aqueous solution using 6-8 times their total mass of deionized water.

[0016] A further preferred heating and stirring condition is: heating and stirring at 60-70°C for 3-4 hours.

[0017] Preferably, in step S3, the nano-sizing method is as follows: first, holocellulose is ball-milled to below 500 mesh, then added to 8-10 times its weight in deionized water, and allowed to swell for 20-24 hours. Then, it is ultra-finely pulverized using a disc mill. Specific process conditions are: disc mill speed 3000-4000 r / min, each disc milling time 20-30 minutes, repeated 8-10 times, and disc gap 0.005 mm. Preferably, in step S3, the preparation method of the nano-harvest cellulose linseed gum gel particles is as follows: nano-harvest cellulose and linseed gum are stirred and dispersed in deionized water, heated in a water bath at 50-60°C, the pH is adjusted to 11-12 using 0.1 mol / L sodium hydroxide solution, ethylene glycol diglycidyl ether is added, the mixture is kept warm and stirred for 3-4 hours, and then freeze-dried under vacuum and pulverized to obtain the product; wherein, the mass ratio of nano-harvest cellulose, linseed gum, and ethylene glycol diglycidyl ether is 1:0.3-0.4:0.03-0.04.

[0018] Preferably, in step S3, the preparation method of nano-harvest cellulose calcium alginate fiber powder is as follows: First, nano-harvest cellulose is added to an aqueous solution of N-methylmorpholine nitrogen oxides at 6-8 times its weight, and allowed to swell at 65-75°C for 30-40 minutes. The swelled nano-harvest cellulose is then filtered to obtain swollen nano-harvest cellulose. Then, the swollen nano-harvest cellulose is added to a sodium alginate solution, stirred and mixed, and a calcium chloride solution is added and stirred and mixed to reduce the moisture content to below 15% to obtain a spinning solution. The solution is then dry-spun and wet-spun to obtain composite fibers, which are then pulverized to obtain the final product. The mass ratio of nano-harvest cellulose to sodium alginate in the sodium alginate solution is 10:0.4-0.6, the molar ratio of sodium alginate in the sodium alginate solution to calcium chloride in the calcium chloride solution is 2:1, and the mass concentrations of both the sodium alginate solution and the calcium chloride solution are 3-4%.

[0019] Further preferably, the water content of the N-methylmorpholine nitrogen oxide aqueous solution is 45-50%; the water content is reduced by thin-film evaporation, with the following process conditions: temperature 90-100℃, vacuum degree -8.0×10⁻⁶. -4 Pa.

[0020] Further preferred process conditions for dry-jet wet spinning are: ring cooling air blowing, air temperature -5℃, air flow rate 300L / min, humidity 40%; spinning solution extrusion temperature 110℃, air layer length 50mm, air layer temperature -5℃, 5% N-methylmorpholine nitrogen oxide aqueous solution coagulation bath, coagulation bath temperature 20℃, and drying temperature 110℃.

[0021] Preferably, in step S4, the particle sizes of the carboxymethyl cellulose graft product, nano-harvest cellulose flaxseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder are 80-100 mesh, 100-150 mesh, and 150-200 mesh, respectively, and the mass ratio of the three is 1:0.4-0.6:0.2-0.3.

[0022] Preferably, the specific method of step S4 is as follows: the carboxymethyl cellulose graft product, nano-harvest cellulose flaxseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder are mixed evenly and conveyed to the granulator. Granulation is started and gelatinized starch liquid is sprayed in at the same time. Granulation is continued for 5 to 7 minutes, dried, and sieved to obtain particles with a particle size of 3 to 4 mm.

[0023] A further preferred method for preparing the gelatinized starch solution is as follows: corn starch is added to water at 3 to 4 times its weight and gelatinized at 70 to 75°C for 10 to 15 minutes; the amount of corn starch used is 0.3 to 0.4% of the total mass of carboxymethyl cellulose graft product, nano-harvestibular flaxseed gum gel particles, and nano-harvestibular cellulose calcium alginate fiber powder.

[0024] A cotton stalk-based agroforestry water-retaining material is obtained through the aforementioned preparation method.

[0025] The beneficial effects of this invention are as follows: This invention discloses a cotton stalk-based agroforestry water-retaining material and its preparation method. It is obtained by mixing and granulating carboxymethyl cellulose grafted products, nano-harvest cellulose linseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder, with cotton stalks as the raw material. This invention realizes the resource utilization of cotton stalks, obtaining a water-retaining material with high water absorption, slow-release water retention, and good mechanical stability. Furthermore, by replacing sodium carboxymethyl cellulose with potassium carboxymethyl cellulose, the ionic compatibility and applicability of the water-retaining material in the soil environment are improved.

[0026] Specifically, cotton stalks are first used as raw material to extract holocellulose; holocellulose is then used as raw material to extract cellulose, which is then carboxymethylated to obtain potassium carboxymethyl cellulose (CS-CMC-K). CS-CMC-K is used as a backbone and undergoes a graft copolymerization and crosslinking reaction with acrylic acid to obtain a carboxymethyl cellulose graft product. Holocellulose is then nano-sized to obtain nano-holocellulose. A portion of the nano-holocellulose is crosslinked with flaxseed gum to obtain nano-holocellulose flaxseed gum gel particles. The remaining nano-holocellulose is mixed with sodium alginate and calcium chloride to prepare nano-holocellulose calcium alginate fiber powder. Finally, the carboxymethyl cellulose graft product, nano-holocellulose flaxseed gum gel particles, and nano-holocellulose calcium alginate fiber powder are mixed and granulated.

[0027] The specific advantages are as follows: (1) Use cotton stalks as raw materials to improve the utilization rate of agricultural waste; (2) Using CS-CMC-K as a hydrophilic skeleton, a three-dimensional network is constructed by grafting and crosslinking with acrylic acid to improve the water absorption ratio and water retention performance; (3) Using potassium salt type carboxymethyl cellulose is beneficial to the material's adaptability in soil ionic environment and reduces the potential salinization risk caused by the introduction of sodium ions; (4) The synergistic effect of carboxymethyl cellulose graft products, nano-harvest cellulose flaxseed gel particles, and nano-harvest cellulose calcium alginate fiber powder with different particle size scales further improves water absorption, water retention and water holding effect through their own pores and the pore structure formed during the composite process. Detailed Implementation

[0028] The preferred embodiments of the present invention will now be described in detail. Example 1

[0029] A method for preparing a cotton stalk-based agroforestry water-retaining material, the specific steps of which are as follows: S1. First, extract holocellulose from cotton stalks;

[0030] The specific method is as follows: S1-1. Crush the cotton stalks, add them to a sulfuric acid solution with 8 times their weight, let them stand to soak and neutralize, add urea and hexadecyltrimethylammonium bromide, mix well to obtain a mixture; S1-2. Ultrasonic oscillation treatment, cold storage treatment, centrifugation to collect the precipitate, washing with water, drying to obtain the intermediate product; S1-3. Extract the intermediate product with benzene alcohol, filter to obtain the solid, air dry naturally, pour into a sodium chlorite-acetic acid mixture for bleaching, filter to obtain the solid, dry, and obtain holocellulose.

[0031] In step S1-1, the mass concentration of the sulfuric acid solution is 10%; the soaking time is 5 hours; the pH is neutralized to 7 using a 0.3% potassium hydroxide solution; and the mass percentages of urea and hexadecyltrimethylammonium bromide in the mixture are 10% and 13%, respectively.

[0032] In steps S1-2, the ultrasonic oscillation treatment conditions are: frequency 35kHz, power 400W, time 20 minutes; the refrigeration treatment conditions are: refrigeration at 4℃ for 12 hours; and the drying conditions are: drying at 45℃ to constant weight.

[0033] In steps S1-3, the extraction conditions for benzene alcohol are as follows: a benzene-ethanol mixed solution with a volume ratio of 2:1 is heated to reflux for 6 hours; the sodium chlorite-glacial acetic acid mixture is obtained by mixing equal volumes of a 5% sodium chlorite aqueous solution and a 2% acetic acid solution; the amount of sodium chlorite-acetic acid mixture used is twice the mass of the intermediate product, and the bleaching time is 3 minutes; the drying conditions are: drying at 45℃ to constant weight.

[0034] S2. Using holocellulose as raw material, cellulose is extracted and carboxymethylated to obtain potassium carboxymethyl cellulose CS-CMC-K. Using CS-CMC-K as the backbone, it is grafted and copolymerized with acrylic acid to obtain carboxymethyl cellulose graft product.

[0035] The method for extracting cellulose is as follows: add holocellulose to a potassium hydroxide solution of 6 times its weight and stir at 75°C for 1 hour to dissolve hemicellulose. Filter to obtain the solid, wash with water until neutral, and dry at 45°C to constant weight to obtain cellulose.

[0036] The carboxymethylation method is as follows: First, cellulose is stirred and dispersed in a 90% isopropanol aqueous solution with a volume concentration of 6 times its weight. Then, a 30% hydrogen peroxide aqueous solution and a 50% potassium hydroxide solution are added, and the mixture is stirred at 20°C for 2 hours. Next, a 50% chloroacetic acid solution is added, and the mixture is stirred for another 30 minutes. The temperature is then gradually increased to 45°C, 60°C, and 75°C, and the mixture is stirred for 30 minutes, 30 minutes, and 90 minutes respectively to complete the etherification reaction. Finally, the pH is adjusted to neutral using a 10% acetic acid solution, the solid is filtered, washed three times with anhydrous ethanol, dried at 70°C, and pulverized to obtain the CS-CMC-K. The molar ratio of glucose units in cellulose, hydrogen peroxide in hydrogen peroxide solution, potassium hydroxide in potassium hydroxide solution, and chloroacetic acid in chloroacetic acid solution is 1:2:2:2.

[0037] The preparation method of carboxymethyl cellulose grafted product is as follows: CS-CMC-K is stirred and dispersed in 8 times its weight of deionized water and allowed to stand for 24 hours to fully swell; then, in an ice-water bath, a 20% potassium hydroxide solution is added dropwise to acrylic acid while stirring, slowly neutralizing the acrylic acid to a neutralization degree of 70%, resulting in a partially neutralized acrylate solution; the fully swollen CS-CMC-K is then mixed with the partially neutralized acrylate solution, followed by the addition of N,N'-methylenebisacrylamide and potassium persulfate. Under nitrogen protection, the mixture is heated and stirred to carry out the graft copolymerization crosslinking reaction. After the reaction is completed, the product is allowed to stand to partially solidify, and then removed. The product is washed with anhydrous ethanol and water alternately to remove unreacted monomers and impurities, dried at 60°C to constant weight, and pulverized to obtain the carboxymethyl cellulose grafted product.

[0038] The mass ratio of CS-CMC-K to acrylic acid is 1:5. The amounts of N,N'-methylenebisacrylamide and potassium persulfate are 0.1% and 0.3% of the mass of CS-CMC-K, respectively. The N,N'-methylenebisacrylamide and potassium persulfate are added after being prepared into an aqueous solution with 6 times their total mass of deionized water.

[0039] The heating and stirring conditions are: heating and stirring at 60℃ for 3 hours.

[0040] S3. Using holocellulose as raw material, nano-sized to obtain nano holocellulose. A portion of the nano holocellulose is cross-linked with linseed gum to obtain nano holocellulose linseed gum gel particles. The remaining nano holocellulose is mixed with sodium alginate and calcium chloride to prepare nano holocellulose calcium alginate fiber powder.

[0041] The nano-sizing method is as follows: First, holocellulose is ball-milled to below 500 mesh, then added to 8 times its weight in deionized water, and allowed to swell for 20 hours. Then, it is ultra-finely pulverized using a disc mill. The specific process conditions are: disc mill speed 3000 r / min, each disc milling time 20 minutes, repeated 8 times, and disc gap 0.005 mm. The preparation method of nano-harvest cellulose linseed gum gel particles is as follows: nano-harvest cellulose and linseed gum are stirred and dispersed in deionized water, heated in a 50°C water bath, the pH is adjusted to 11 using 0.1 mol / L sodium hydroxide solution, ethylene glycol diglycidyl ether is added, the mixture is kept warm and stirred for 3 hours, and then freeze-dried under vacuum and pulverized to obtain the final product; wherein, the mass ratio of nano-harvest cellulose, linseed gum and ethylene glycol diglycidyl ether is 1:0.3:0.03.

[0042] The preparation method of nano-harvest cellulose calcium alginate fiber powder is as follows: First, nano-harvest cellulose is added to an aqueous solution of N-methylmorpholine nitrogen oxides at 6 times its weight, and allowed to swell at 65°C for 30 minutes. The swelled nano-harvest cellulose is then filtered to obtain swollen nano-harvest cellulose. Then, the swollen nano-harvest cellulose is added to a sodium alginate solution and stirred until homogeneous. Calcium chloride solution is added and stirred until homogeneous. The moisture content is reduced to below 15% to obtain a spinning solution. The solution is then dry-spun and wet-spun to obtain composite fibers, which are then pulverized to obtain the final product. The mass ratio of nano-harvest cellulose to sodium alginate solution is 10:0.4, the molar ratio of sodium alginate solution to calcium chloride solution is 2:1, and the mass concentration of both sodium alginate solution and calcium chloride solution is 3%.

[0043] The aqueous solution of N-methylmorpholine nitrogen oxides has a water content of 45%. The water content is reduced by thin-film evaporation under the following conditions: temperature 90℃, vacuum degree -8.0×10⁻⁶. -4 Pa.

[0044] The process conditions for dry-jet wet spinning are as follows: ring cooling air blowing, air temperature -5℃, air flow rate 300L / min, humidity 40%; spinning solution extrusion temperature 110℃, air layer length 50mm, air layer temperature -5℃, 5% N-methylmorpholine nitrogen oxide aqueous solution coagulation bath, coagulation bath temperature 20℃, and drying temperature 110℃.

[0045] S4. Finally, mix and granulate the carboxymethyl cellulose graft product, nano-harvest cellulose flaxseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder.

[0046] The specific method is as follows: Carboxymethyl cellulose graft product, nano-harvest cellulose flaxseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder are mixed evenly and fed into a granulator. Granulation is started, and gelatinized starch liquid is sprayed in at the same time. Granulation is continued for 5 minutes, dried, and sieved to obtain particles with a particle size of 3mm.

[0047] The particle sizes of the carboxymethyl cellulose graft product, nano-harvest cellulose flaxseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder are 80 mesh, 100 mesh, and 150 mesh, respectively, and the mass ratio of the three is 1:0.4:0.2.

[0048] The method for preparing the gelatinized starch solution is as follows: add corn starch to water with a weight of 3, and gelatinize at 70°C for 10 minutes; the amount of corn starch used is 0.3% of the total mass of carboxymethyl cellulose graft product, nano-harvestibular cellulose flaxseed gum gel particles, and nano-harvestibular cellulose calcium alginate fiber powder. Example 2

[0049] A method for preparing a cotton stalk-based agroforestry water-retaining material, the specific steps of which are as follows: S1. First, extract holocellulose from cotton stalks;

[0050] The specific method is as follows: S1-1. Crush the cotton stalks, add them to a sulfuric acid solution with 10 times their weight, let them stand to soak and neutralize, add urea and hexadecyltrimethylammonium bromide, mix well to obtain a mixture; S1-2. Ultrasonic oscillation treatment, cold storage treatment, centrifugation to collect the precipitate, washing with water, drying to obtain the intermediate product; S1-3. Extract the intermediate product with benzene alcohol, filter to obtain the solid, air dry naturally, pour into a sodium chlorite-acetic acid mixture for bleaching, filter to obtain the solid, dry, and obtain holocellulose.

[0051] In step S1-1, the mass concentration of the sulfuric acid solution is 15%; the soaking time is 7 hours; the pH is neutralized to 7 using a 0.5% potassium hydroxide solution; and the mass percentages of urea and cetyltrimethylammonium bromide in the mixture are 10% and 13%, respectively.

[0052] In steps S1-2, the ultrasonic oscillation treatment conditions are: frequency 45kHz, power 600W, time 30 minutes; the refrigeration treatment conditions are: refrigeration at 4℃ for 12 hours; and the drying conditions are: drying at 45℃ to constant weight.

[0053] In steps S1-3, the extraction conditions for benzene alcohol are as follows: a benzene-ethanol mixed solution with a volume ratio of 2:1 is heated to reflux for 8 hours; the sodium chlorite-glacial acetic acid mixture is obtained by mixing equal volumes of a 10% sodium chlorite aqueous solution and a 5% acetic acid solution; the amount of sodium chlorite-acetic acid mixture used is 3 times the mass of the intermediate product, and the bleaching time is 5 minutes; the drying conditions are: drying at 45℃ to constant weight.

[0054] S2. Using holocellulose as raw material, cellulose is extracted and carboxymethylated to obtain potassium carboxymethyl cellulose CS-CMC-K. Using CS-CMC-K as the backbone, it is grafted and copolymerized with acrylic acid to obtain carboxymethyl cellulose graft product.

[0055] The method for extracting cellulose is as follows: add holocellulose to a potassium hydroxide solution with 8 times its weight and stir at 85°C for 2 hours to dissolve hemicellulose. Filter to obtain the solid, wash with water until neutral, and dry at 45°C to constant weight to obtain cellulose.

[0056] The carboxymethylation method is as follows: First, cellulose is stirred and dispersed in an aqueous solution of 90% isopropanol with a volume concentration of 8 times its weight. Then, a 30% hydrogen peroxide solution and a 50% potassium hydroxide solution are added, and the mixture is stirred at 30°C for 3 hours. Next, a 50% chloroacetic acid solution is added, and the mixture is stirred for another 30 minutes. The temperature is then gradually increased to 45°C, 60°C, and 75°C, and the mixture is stirred for 30 minutes, 30 minutes, and 90 minutes respectively to complete the etherification reaction. Finally, the pH is adjusted to neutral using a 10% acetic acid solution, the solid is filtered, washed three times with anhydrous ethanol, dried at 70°C, and pulverized to obtain the CS-CMC-K. The molar ratio of glucose units in cellulose, hydrogen peroxide in the hydrogen peroxide solution, potassium hydroxide in the potassium hydroxide solution, and chloroacetic acid in the chloroacetic acid solution is 1:3:3:3.

[0057] The preparation method of carboxymethyl cellulose grafted product is as follows: CS-CMC-K is stirred and dispersed in 10 times its weight of deionized water, and allowed to stand for 24 hours to fully swell; then, in an ice-water bath, a 20% potassium hydroxide solution is added dropwise to acrylic acid while stirring, slowly neutralizing the acrylic acid to a neutralization degree of 80%, resulting in a partially neutralized acrylate solution; the fully swollen CS-CMC-K is then mixed with the partially neutralized acrylate solution, followed by the addition of N,N'-methylenebisacrylamide and potassium persulfate. Under nitrogen protection, the mixture is heated and stirred to carry out the graft copolymerization crosslinking reaction. After the reaction is completed, the product is allowed to stand to partially solidify, and then removed. The product is washed with anhydrous ethanol and water alternately to remove unreacted monomers and impurities, dried at 60°C to constant weight, and pulverized to obtain the carboxymethyl cellulose grafted product.

[0058] The mass ratio of CS-CMC-K to acrylic acid is 1:6. The amounts of N,N'-methylenebisacrylamide and potassium persulfate are 0.2% and 0.4% of the mass of CS-CMC-K, respectively. The N,N'-methylenebisacrylamide and potassium persulfate are added after being prepared into an aqueous solution with 8 times their total mass of deionized water.

[0059] The heating and stirring conditions were: heating and stirring at 70℃ for 4 hours.

[0060] S3. Using holocellulose as raw material, nano-sized to obtain nano holocellulose. A portion of the nano holocellulose is cross-linked with linseed gum to obtain nano holocellulose linseed gum gel particles. The remaining nano holocellulose is mixed with sodium alginate and calcium chloride to prepare nano holocellulose calcium alginate fiber powder.

[0061] The nano-sizing method is as follows: First, holocellulose is ball-milled to below 500 mesh, then added to 10 times its weight in deionized water, and allowed to swell for 24 hours. Then, it is ultra-finely pulverized using a disc mill. The specific process conditions are: disc mill speed 4000 r / min, each disc milling time 30 minutes, repeated 10 times, and disc gap 0.005 mm. The preparation method of nano-harvest cellulose linseed gum gel particles is as follows: nano-harvest cellulose and linseed gum are stirred and dispersed in deionized water, heated in a water bath at 60°C, the pH is adjusted to 12 using 0.1 mol / L sodium hydroxide solution, ethylene glycol diglycidyl ether is added, the mixture is kept warm and stirred for 4 hours, and then freeze-dried under vacuum and pulverized to obtain the product; wherein, the mass ratio of nano-harvest cellulose, linseed gum and ethylene glycol diglycidyl ether is 1:0.4:0.04.

[0062] The preparation method of nano-harvest cellulose calcium alginate fiber powder is as follows: First, nano-harvest cellulose is added to an aqueous solution of N-methylmorpholine nitrogen oxides at 8 times its weight, and allowed to swell at 75°C for 40 minutes. The swelled nano-harvest cellulose is then filtered to obtain swollen nano-harvest cellulose. Then, the swollen nano-harvest cellulose is added to a sodium alginate solution and stirred until homogeneous. Calcium chloride solution is added and stirred until homogeneous. The moisture content is reduced to below 15% to obtain a spinning solution. The solution is then dry-spun and wet-spun to obtain composite fibers, which are then pulverized to obtain the final product. The mass ratio of nano-harvest cellulose to sodium alginate solution is 10:0.6, the molar ratio of sodium alginate solution to calcium chloride solution is 2:1, and the mass concentrations of both sodium alginate solution and calcium chloride solution are 4%.

[0063] The aqueous solution of N-methylmorpholine nitrogen oxides has a water content of 50%. The water content is reduced by thin-film evaporation under the following conditions: temperature 100℃, vacuum degree -8.0×10⁻⁶. -4 Pa.

[0064] The process conditions for dry-jet wet spinning are as follows: ring cooling air blowing, air temperature -5℃, air flow rate 300L / min, humidity 40%; spinning solution extrusion temperature 110℃, air layer length 50mm, air layer temperature -5℃, 5% N-methylmorpholine nitrogen oxide aqueous solution coagulation bath, coagulation bath temperature 20℃, and drying temperature 110℃.

[0065] S4. Finally, mix and granulate the carboxymethyl cellulose graft product, nano-harvest cellulose flaxseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder.

[0066] The specific method is as follows: Carboxymethyl cellulose graft product, nano-harvest cellulose flaxseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder are mixed evenly and fed into a granulator. Granulation is started, and gelatinized starch liquid is sprayed in at the same time. Granulation is continued for 7 minutes, dried, and sieved to obtain particles with a particle size of 4mm.

[0067] The particle sizes of the carboxymethyl cellulose graft product, nano-harvest cellulose flaxseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder are 100 mesh, 150 mesh, and 200 mesh, respectively, and the mass ratio of the three is 1:0.6:0.3.

[0068] The method for preparing gelatinized starch solution is as follows: add corn starch to 4 times its weight of water and gelatinize at 75°C for 15 minutes; the amount of corn starch used is 0.4% of the total mass of carboxymethyl cellulose graft product, nano-harvestibular cellulose flaxseed gum gel particles, and nano-harvestibular cellulose calcium alginate fiber powder. Example 3

[0069] A method for preparing a cotton stalk-based agroforestry water-retaining material, the specific steps of which are as follows: S1. First, extract holocellulose from cotton stalks;

[0070] The specific method is as follows: S1-1. Crush the cotton stalks, add them to a sulfuric acid solution with a weight of 9, let them stand to soak and neutralize, add urea and hexadecyltrimethylammonium bromide, mix well to obtain a mixture; S1-2. Ultrasonic oscillation treatment, cold storage treatment, centrifugation to collect the precipitate, washing with water, drying to obtain the intermediate product; S1-3. Extract the intermediate product with benzene alcohol, filter to obtain the solid, air dry naturally, pour into a sodium chlorite-acetic acid mixture for bleaching, filter to obtain the solid, dry, and obtain holocellulose.

[0071] In step S1-1, the mass concentration of the sulfuric acid solution is 12%; the soaking time is 6 hours; the pH is neutralized to 7 using a 0.4% potassium hydroxide solution; and the mass percentages of urea and cetyltrimethylammonium bromide in the mixture are 10% and 13%, respectively.

[0072] In steps S1-2, the ultrasonic oscillation treatment conditions are: frequency 40kHz, power 500W, time 25 minutes; the refrigeration treatment conditions are: refrigeration at 4℃ for 12 hours; and the drying conditions are: drying at 45℃ to constant weight.

[0073] In steps S1-3, the extraction conditions for benzene alcohol are as follows: a benzene-ethanol mixed solution with a volume ratio of 2:1 is heated to reflux for 7 hours; the sodium chlorite-glacial acetic acid mixture is obtained by mixing equal volumes of an 8% sodium chlorite aqueous solution and a 3% acetic acid solution; the amount of sodium chlorite-acetic acid mixture used is 2.5 times the mass of the intermediate product, and the bleaching time is 4 minutes; the drying conditions are: drying at 45°C to constant weight.

[0074] S2. Using holocellulose as raw material, cellulose is extracted and carboxymethylated to obtain potassium carboxymethyl cellulose CS-CMC-K. Using CS-CMC-K as the backbone, it is grafted and copolymerized with acrylic acid to obtain carboxymethyl cellulose graft product.

[0075] The method for extracting cellulose is as follows: add holocellulose to a potassium hydroxide solution with a weight of 7 times its weight and stir at 80°C for 1.5 hours to dissolve hemicellulose. Filter to obtain the solid, wash with water until neutral, and dry at 45°C to constant weight to obtain cellulose.

[0076] The carboxymethylation method is as follows: First, cellulose is stirred and dispersed in a 90% isopropanol aqueous solution with a volume concentration of 7 times its weight. Then, a 30% hydrogen peroxide aqueous solution and a 50% potassium hydroxide solution are added, and the mixture is stirred at 25°C for 2.5 hours. Next, a 50% chloroacetic acid solution is added, and the mixture is stirred for another 30 minutes. The temperature is then gradually increased to 45°C, 60°C, and 75°C, and the mixture is stirred for 30 minutes, 30 minutes, and 90 minutes respectively to complete the etherification reaction. Finally, the pH is adjusted to neutral using a 10% acetic acid solution, the solid is filtered, washed three times with anhydrous ethanol, dried at 70°C, and pulverized to obtain the CS-CMC-K. The molar ratio of glucose units in cellulose, hydrogen peroxide in hydrogen peroxide solution, potassium hydroxide in potassium hydroxide solution, and chloroacetic acid in chloroacetic acid solution is 1:2.5:2.5:2.5.

[0077] The preparation method of carboxymethyl cellulose grafted product is as follows: CS-CMC-K is stirred and dispersed in 9 times its weight of deionized water and allowed to stand for 24 hours to fully swell; then, in an ice-water bath, a 20% potassium hydroxide solution is added dropwise to acrylic acid while stirring, slowly neutralizing the acrylic acid to a neutralization degree of 75%, resulting in a partially neutralized acrylate solution; the fully swollen CS-CMC-K is then mixed with the partially neutralized acrylate solution, followed by the addition of N,N'-methylenebisacrylamide and potassium persulfate. Under nitrogen protection, the mixture is heated and stirred to carry out the graft copolymerization crosslinking reaction. After the reaction is completed, the product is allowed to stand to partially solidify, and then removed. The product is washed with anhydrous ethanol and water alternately to remove unreacted monomers and impurities, dried at 60°C to constant weight, and pulverized to obtain the carboxymethyl cellulose grafted product.

[0078] The mass ratio of CS-CMC-K to acrylic acid is 1:5.5. The amounts of N,N'-methylenebisacrylamide and potassium persulfate are 0.15% and 0.35% of the mass of CS-CMC-K, respectively. The N,N'-methylenebisacrylamide and potassium persulfate are added after being prepared into an aqueous solution with 7 times their total mass of deionized water.

[0079] The heating and stirring conditions were: heating and stirring at 65°C for 3.5 hours.

[0080] S3. Using holocellulose as raw material, nano-sized to obtain nano holocellulose. A portion of the nano holocellulose is cross-linked with linseed gum to obtain nano holocellulose linseed gum gel particles. The remaining nano holocellulose is mixed with sodium alginate and calcium chloride to prepare nano holocellulose calcium alginate fiber powder.

[0081] The nano-sizing method is as follows: First, holocellulose is ball-milled to below 500 mesh, then added to 9 times its weight in deionized water, and allowed to swell for 22 hours. Then, it is ultra-finely pulverized using a disc mill. The specific process conditions are: disc mill speed 4000 r / min, each disc milling time 25 minutes, repeated 9 times, and disc gap 0.005 mm. The preparation method of nano-harvest cellulose linseed gum gel particles is as follows: nano-harvest cellulose and linseed gum are stirred and dispersed in deionized water, heated in a water bath at 55°C, the pH is adjusted to 11 using 0.1 mol / L sodium hydroxide solution, ethylene glycol diglycidyl ether is added, the mixture is kept warm and stirred for 3.5 hours, and then freeze-dried under vacuum and pulverized to obtain the final product; wherein, the mass ratio of nano-harvest cellulose, linseed gum and ethylene glycol diglycidyl ether is 1:0.35:0.035.

[0082] The preparation method of nano-harvest cellulose calcium alginate fiber powder is as follows: First, nano-harvest cellulose is added to an aqueous solution of N-methylmorpholine nitrogen oxides at 7 times its weight, and allowed to swell at 70°C for 35 minutes. The swelled nano-harvest cellulose is then filtered to obtain swollen nano-harvest cellulose. Then, the swollen nano-harvest cellulose is added to a sodium alginate solution and stirred until homogeneous. Calcium chloride solution is added and stirred until homogeneous. The moisture content is reduced to below 15% to obtain a spinning solution. The solution is then dry-spun and wet-spun to obtain composite fibers, which are then pulverized to obtain the final product. The mass ratio of nano-harvest cellulose to sodium alginate solution is 10:0.5, the molar ratio of sodium alginate solution to calcium chloride solution is 2:1, and the mass concentration of both sodium alginate solution and calcium chloride solution is 3.5%.

[0083] The aqueous solution of N-methylmorpholine nitrogen oxides has a water content of 48%. The water content is reduced by thin-film evaporation under the following conditions: temperature 90–100℃, vacuum degree -8.0 × 10⁻⁶. -4 Pa.

[0084] The process conditions for dry-jet wet spinning are as follows: ring cooling air blowing, air temperature -5℃, air flow rate 300L / min, humidity 40%; spinning solution extrusion temperature 110℃, air layer length 50mm, air layer temperature -5℃, 5% N-methylmorpholine nitrogen oxide aqueous solution coagulation bath, coagulation bath temperature 20℃, and drying temperature 110℃.

[0085] S4. Finally, mix and granulate the carboxymethyl cellulose graft product, nano-harvest cellulose flaxseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder.

[0086] The specific method is as follows: Carboxymethyl cellulose graft product, nano-harvest cellulose flaxseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder are mixed evenly and fed into a granulator. Granulation is started, and gelatinized starch liquid is sprayed in at the same time. Granulation is continued for 6 minutes, dried, and sieved to obtain particles with a particle size of 3mm.

[0087] The particle sizes of the carboxymethyl cellulose graft product, nano-harvest cellulose flaxseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder are 90 mesh, 120 mesh, and 180 mesh, respectively, and the mass ratio of the three is 1:0.5:0.25.

[0088] The method for preparing the gelatinized starch solution is as follows: add corn starch to 3.5 times its weight of water and gelatinize at 72°C for 12 minutes; the amount of corn starch used is 0.35% of the total mass of carboxymethyl cellulose graft product, nano-harvestibular cellulose flaxseed gum gel particles, and nano-harvestibular cellulose calcium alginate fiber powder.

[0089] Comparative Example 1

[0090] In step S3, holocellulose was not nano-sized; holocellulose was used to replace nano-holocellulose.

[0091] The rest is the same as in Example 1.

[0092] Comparative Example 2

[0093] The nano-cellulose flaxseed gel particles are omitted.

[0094] The rest is the same as in Example 1.

[0095] Comparative Example 3

[0096] The nano-cellulose calcium alginate fiber powder is omitted.

[0097] The rest is the same as in Example 1.

[0098] Experimental Example

[0099] The water-retaining materials obtained in Examples 1-3 and Comparative Examples 1-3 were subjected to relevant tests, including: 1. Water absorption rate (average rate within 5 minutes): Take 1g (m1) of water-retaining material and mix it with 1000mL of tap water for 5 minutes to obtain a gel. After filtering the gel through a 0.18mm sieve, weigh it (m2). Water absorption rate = (m2-m1) / 5m1.

[0100] 2. Water absorption ratio: Take 1g (m3) of water-retaining material and mix it with 1000mL of tap water for 30 minutes to obtain a gel. After filtering the gel through a 0.18mm sieve, weigh it as m4. Water absorption ratio = (m4-m3) / m3.

[0101] 3. Tensile strength: The gel obtained in Part 2 was tested using an electronic universal testing machine (Shimadzu AGX-V2).

[0102] The test results are shown in Table 1.

[0103] Table 1 Example 1 90.05 485.6 5.3 Example 2 90.11 486.0 5.5 Example 3 90.58 487.1 5.6 Comparative Example 1 61.22 400.5 2.9 Comparative Example 2 84.73 460.6 4.1 Comparative Example 3 85.06 462.7 4.0 As shown in Table 1, the water-retaining materials obtained in Examples 1 to 3 have high water retention performance and excellent mechanical properties.

[0104] In Comparative Example 1, step S3, holocellulose was not nano-sized and holocellulose was used to replace nano-holocellulose. In Comparative Example 2, nano-holocellulose flaxseed gum gel particles were omitted. In Comparative Example 3, nano-holocellulose calcium alginate fiber powder was omitted. The water retention performance and mechanical properties of the resulting water-retaining materials were significantly worse. This indicates that in this application, carboxymethyl cellulose graft products, nano-holocellulose flaxseed gum gel particles, and nano-holocellulose calcium alginate fiber powder synergistically improve mechanical properties and water retention performance through the formation of specific microstructures.

[0105] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made to it in form and detail without departing from the scope defined by the claims of the present invention.

Claims

1. A method for preparing a cotton stalk-based agroforestry water-retaining material, characterized in that, The specific steps are as follows: S1. First, extract holocellulose from cotton stalks; S2. Using holocellulose as raw material, cellulose is extracted and carboxymethylated to obtain potassium carboxymethyl cellulose CS-CMC-K. Using CS-CMC-K as the backbone, it is grafted and copolymerized with acrylic acid to obtain carboxymethyl cellulose graft product. S3. Using holocellulose as raw material, nano-sized to obtain nano holocellulose. A portion of the nano holocellulose is cross-linked with linseed gum to obtain nano holocellulose linseed gum gel particles. The remaining nano holocellulose is mixed with sodium alginate and calcium chloride to prepare nano holocellulose calcium alginate fiber powder. S4. Finally, mix and granulate the carboxymethyl cellulose graft product, nano-harvest cellulose flaxseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder.

2. The preparation method according to claim 1, characterized in that, The specific method for step S1 is as follows: S1-1. Crush the cotton stalks, add them to a sulfuric acid solution of 8 to 10 times their weight, let them stand and soak, neutralize, add urea and hexadecyltrimethylammonium bromide, mix evenly, and obtain a mixture; S1-2. Ultrasonic oscillation treatment, cold storage treatment, centrifugation to collect the precipitate, washing with water, drying, to obtain the intermediate product; S1-3. Extract the intermediate product with benzene alcohol, filter to obtain the solid, air dry naturally, pour into a sodium chlorite-acetic acid mixture for bleaching, filter to obtain the solid, dry, and obtain holocellulose.

3. The preparation method according to claim 1, characterized in that, In step S2, the method for extracting cellulose is as follows: add holocellulose to a potassium hydroxide solution of 6 to 8 times its weight and stir at 75 to 85°C for 1 to 2 hours to dissolve hemicellulose, filter to obtain solid, wash with water until neutral, and dry at 45°C to constant weight to obtain cellulose.

4. The preparation method according to claim 1, characterized in that, In step S2, the carboxymethylation method is as follows: First, cellulose is stirred and dispersed in 6-8 times its weight of a 90% isopropanol aqueous solution. Then, a 30% hydrogen peroxide solution and a 50% potassium hydroxide solution are added, and the mixture is stirred at 20-30°C for 2-3 hours. Next, a 50% chloroacetic acid solution is added, and the mixture is stirred for another 30 minutes. The temperature is then gradually increased to 45°C, 60°C, and 75°C, and the mixture is stirred for 30 minutes, 30 minutes, and 90 minutes respectively to complete the etherification reaction. Finally, the pH is adjusted to neutral using a 10% acetic acid solution, the solid is filtered, washed three times with anhydrous ethanol, dried at 70°C, and pulverized to obtain the CS-CMC-K. The molar ratio of glucose units in cellulose, hydrogen peroxide in the hydrogen peroxide solution, potassium hydroxide in the potassium hydroxide solution, and chloroacetic acid in the chloroacetic acid solution is 1:2-3:2-3:2-3.

5. The preparation method according to claim 1, characterized in that, In step S2, the preparation method of the carboxymethyl cellulose graft product is as follows: CS-CMC-K is stirred and dispersed in 8 to 10 times its weight of deionized water, and allowed to stand for 24 hours to fully swell; then, in an ice-water bath, a 20% potassium hydroxide solution is added dropwise to acrylic acid while stirring, slowly neutralizing the acrylic acid to a neutralization degree of 70 to 80%, obtaining a partially neutralized acrylate solution; then, the fully swollen CS-CMC-K is mixed with the partially neutralized acrylate solution, followed by the addition of N,N'-methylenebisacrylamide and potassium persulfate, and the graft copolymerization crosslinking reaction is carried out under nitrogen protection by heating and stirring. After the reaction is completed, the product is allowed to stand to initially solidify, and then removed. It is washed with anhydrous ethanol and water alternately to remove unreacted monomers and impurities, dried at 60°C to constant weight, and pulverized to obtain the carboxymethyl cellulose graft product.

6. The preparation method according to claim 1, characterized in that, In step S3, the nano-sizing method is as follows: first, the holocellulose is ball-milled to below 500 mesh, then added to 8 to 10 times its weight in deionized water, and swelled for 20 to 24 hours. Then, it is ultra-finely pulverized using a disc mill. The specific process conditions are: disc mill speed of 3000 to 4000 r / min, each disc milling time of 20 to 30 minutes, repeated disc milling 8 to 10 times, and disc gap of 0.005 mm.

7. The preparation method according to claim 1, characterized in that, In step S3, the preparation method of nano-harvest cellulose linseed gum gel particles is as follows: nano-harvest cellulose and linseed gum are stirred and dispersed in deionized water, heated in a water bath at 50-60℃, the pH is adjusted to 11-12 using 0.1mol / L sodium hydroxide solution, ethylene glycol diglycidyl ether is added, the mixture is kept warm and stirred for 3-4 hours, and then freeze-dried under vacuum and pulverized to obtain the product; wherein, the mass ratio of nano-harvest cellulose, linseed gum and ethylene glycol diglycidyl ether is 1:0.3-0.4:0.03-0.

04.

8. The preparation method according to claim 1, characterized in that, In step S3, the preparation method of nano-harvest cellulose calcium alginate fiber powder is as follows: First, nano-harvest cellulose is added to an aqueous solution of N-methylmorpholine nitrogen oxides at 6-8 times its weight, and allowed to swell at 65-75°C for 30-40 minutes. The swelled nano-harvest cellulose is then filtered to obtain swollen nano-harvest cellulose. Then, the swollen nano-harvest cellulose is added to a sodium alginate solution, stirred and mixed, and a calcium chloride solution is added and stirred and mixed to reduce the moisture content to below 15% to obtain a spinning solution. The solution is then dry-spun and wet-spun to obtain composite fibers, which are then pulverized to obtain the final product. The mass ratio of nano-harvest cellulose to sodium alginate in the sodium alginate solution is 10:0.4-0.6, the molar ratio of sodium alginate in the sodium alginate solution to calcium chloride in the calcium chloride solution is 2:1, and the mass concentrations of both the sodium alginate solution and the calcium chloride solution are 3-4%.

9. The preparation method according to claim 1, characterized in that, The specific method of step S4 is as follows: mix carboxymethyl cellulose graft product, nano-harvest cellulose flaxseed gum gel particles, and nano-harvest cellulose calcium alginate fiber powder evenly, and feed them into a granulator. Start granulation, and spray in gelatinized starch liquid at the same time. Continue granulation for 5 to 7 minutes, dry, and sieve to obtain particles with a particle size of 3 to 4 mm.

10. A cotton stalk-based agroforestry water-retaining material, characterized in that, It is obtained by the preparation method described in any one of claims 1 to 9.