Preparation method of cellulose-based slow-release phosphate fertilizer

Abstract

The invention discloses a preparation method of a cellulose-based slow-release phosphate fertilizer. The preparation method comprises the following steps: 1, preparing a deep-eutectic solvent; 2, extracting the lignin from the cotton straws; 3, preparing a lignin / carboxymethyl cellulose composite solution; and 4, preparing the cellulose-based slow-release phosphate fertilizer and evaluating the leaching effect. The used raw materials are easy to obtain, green, economical and environmentally friendly, the prepared material is biodegradable, the preparation process is simple, the obtained slow-release phosphate fertilizer is good in slow-release performance and has potential large-scale application prospects, and the utilization rate of the phosphate fertilizer can be increased.

Description

Technical Field

[0001] The invention relates to the field of preparation of cellulose-based slow-release phosphate fertilizers, and in particular to a method for preparing cellulose-based slow-release phosphate fertilizers. Background Art

[0002] Fertilizers play a vital role in increasing crop yields to meet the growing world population, however, the conflict between population and limited land for crop cultivation (urbanization, industrialization, desertification, etc.) has become a common concern. Therefore, farmers apply large amounts of fertilizers in order to maximize agricultural production. However, direct dissolution causes these fertilizers to be lost in large quantities through rainfall, irrigation, volatilization, etc., and the nutrients cannot be fully absorbed by crops. Therefore, researchers are gradually focusing on slow-release fertilizers, which can improve nutrient utilization, reduce fertilization frequency, reduce time and energy consumption, and use coating technology (impregnation, inversion phase, spraying method) to better promote crop growth.

[0003] Studies have shown that common coating materials include polyethylene, polystyrene, and polyethersulfone, which have excellent water-blocking and film-forming properties and strong slow-release effects. However, they are difficult to be degraded by microorganisms, have high production costs, and have certain environmental hazards, and cannot meet the requirements of long-term green development. Therefore, researchers have gradually shifted their focus to abundant, non-toxic, low-cost, and biodegradable biopolymers, which have the advantages of improving soil water holding capacity, reducing oxidative stress, promoting soil particle aggregation, and minimizing soil erosion. However, the hydrophilicity of natural polymers leads to their weak durability. At the same time, production costs are also the main problem they face.

[0004] Cellulose is the most abundant polysaccharide in the plant kingdom. Carboxymethylcellulose is one of the most important cellulose derivatives. However, sodium carboxymethylcellulose itself cannot be used directly in sustained-release systems because of its hydrophilicity, which results in poor barrier capacity. Therefore, it needs to be combined with other biopolymers to overcome these shortcomings. Notably, lignin has a filler effect because it has a highly complex aromatic heteropolymer network of phenylpropane units that helps to enhance the hydrophobicity of other biopolymers. Summary of the invention

[0005] In view of this, the present invention provides a method for preparing a cellulose-based slow-release phosphate fertilizer.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A method for preparing a cellulose-based slow-release phosphate fertilizer, wherein the amount "parts" are parts by weight, comprises the following steps:

[0008] Step 1: Preparation of deep eutectic solvent

[0009] Take choline chloride, formic acid and ferric chloride and add them into a reaction bottle, and stir under heating conditions until a uniform transparent solution is obtained to obtain a low eutectic solvent;

[0010] Step 2: Extraction of cotton stalk lignin

[0011] The low eutectic solvent and cotton stalk powder are mixed and stirred evenly, and stirred under heating conditions to react; after cooling to room temperature, anhydrous ethanol is added and stirred to react, and a lignin solution is separated by centrifugation, the ethanol is removed, and deionized water is added and refrigerated, and then centrifuged again, and the precipitate is freeze-dried to obtain cotton stalk lignin;

[0012] Step 3: Preparation of lignin / carboxymethyl cellulose composite solution

[0013] Sodium carboxymethyl cellulose and deionized water are added to a reactor, and stirred under heating conditions until they are completely dissolved; cotton stalk lignin is then added, and stirred under normal temperature conditions, and then subjected to ultrasonic treatment; malic acid is then added, and stirred under heating conditions to obtain a lignin / carboxymethyl cellulose composite solution;

[0014] Step 4: Preparation of cellulose-based slow-release phosphate fertilizer

[0015] Take monoammonium phosphate particles and add them into a coating pot, preheat them, then spray the lignin / carboxymethyl cellulose composite solution, and keep the original temperature for coating; finally, cross-link the coated fertilizer under heating conditions to obtain lignin / carboxymethyl cellulose coated slow-release phosphate fertilizer.

[0016] Preferably, in the first step, the molar ratio of choline chloride, formic acid and ferric chloride is 1:1-3:0.01-0.1.

[0017] Preferably, in the first step, the heating temperature is 60-90° C., and the stirring speed is 300-800 rpm.

[0018] Preferably, in the second step, the amount of the low eutectic solvent added is 5 to 10 parts, and the amount of the cotton straw powder added is 1 part, which is dried and passed through an 80-mesh sieve.

[0019] Preferably, the stirring time of the low eutectic solvent and the cotton straw powder is 20 to 40 minutes, the heating condition is 80 to 120° C., and the stirring reaction time is 2 to 10 hours.

[0020] Preferably, in the second step, the amount of anhydrous ethanol added is 200 to 400 parts, and the stirring reaction time is 4 to 8 hours;

[0021] The method for removing ethanol is to perform rotary evaporation at 45°C, add 400-600 parts of deionized water and refrigerate at 0-4°C for 48 hours.

[0022] Preferably, in the third step, the amount of sodium carboxymethyl cellulose added is 1-3 parts, the amount of deionized water added is 100-200 parts, the heating conditions for adding sodium carboxymethyl cellulose and deionized water into the reactor are 60-90° C., and the stirring time is 2-4 hours.

[0023] Preferably, in the third step, the amount of cotton stalk lignin added is 0.2 to 1 part, the room temperature is 25° C., the stirring speed is 400 to 500 rpm, the stirring time is 0.5 to 1 h, and the ultrasonic treatment time is 0.5 to 1 h.

[0024] Preferably, in the third step, the amount of malic acid added is 5 to 10 parts, the heating condition is 60° C., the stirring speed is 400 rpm, and the stirring time is 2 to 5 hours.

[0025] Preferably, in the fourth step, the amount of monoammonium phosphate particles added is 50 to 100 parts, the preheating condition is 100°C, and the preheating time is 10 to 20 minutes; the amount of lignin / carboxymethyl cellulose composite solution added is 300 to 500 parts; and the coated fertilizer is cross-linked at 140°C for 30 to 40 minutes.

[0026] Compared with the prior art, the present invention has achieved the following technical effects:

[0027] (1) The low eutectic solvent prepared by the present invention has the advantages of high stability, low volatility, low cost and low toxicity as a green organic solvent;

[0028] (2) Using a low eutectic solvent to pretreat cotton straw to extract lignin has the advantages of simple process, selective dissolution of lignin, low cost, and high recyclability;

[0029] (3) The synthetic raw materials used are all environmentally friendly green materials, which are environmentally friendly and avoid secondary pollution;

[0030] (4) The present invention cross-links the extracted lignin with sodium carboxymethyl cellulose to obtain a composite material that is biodegradable, economical and environmentally friendly;

[0031] (5) The slow-release phosphate fertilizer prepared by coating the phosphate fertilizer with the obtained composite material in the present invention has good slow-release performance, potential large-scale application prospects, simple operation method, and easy availability of raw materials. It is expected to be used in modern agriculture to improve the utilization rate of phosphate fertilizer. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The contact angle measurement results of the lignin / carboxymethyl cellulose composite film in the preparation method of the cellulose-based slow-release phosphate fertilizer of the present invention;

[0033] Figure 2This is an infrared spectrum of a lignin / carboxymethyl cellulose composite film in a method for preparing a cellulose-based slow-release phosphate fertilizer of the present invention;

[0034] Figure 3 A schematic diagram of soil column leaching of cellulose-based slow-release phosphate fertilizer in a method for preparing cellulose-based slow-release phosphate fertilizer of the present invention;

[0035] Figure 4 The invention discloses a leaching loss content of cellulose-based slow-release phosphate fertilizer in each proportion formula in a method for preparing cellulose-based slow-release phosphate fertilizer. DETAILED DESCRIPTION

[0036] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0037] like Figure 1-4 As shown, the present invention discloses a method for preparing a cellulose-based slow-release phosphate fertilizer, wherein the amount "parts" taken are parts by weight, and comprises the following steps:

[0038] Step 1: Preparation of deep eutectic solvent

[0039] Add choline chloride, formic acid and ferric chloride into a reaction bottle at a molar ratio of 1:1-3:0.01-0.1, stir at 60-90°C at a speed of 300-800 rpm until a uniform transparent solution is obtained to obtain a low eutectic solvent;

[0040] Step 2: Extraction of cotton stalk lignin

[0041] Take 5 to 10 parts of the low eutectic solvent and 1 part of dry cotton stalk powder through an 80-mesh sieve, stir for 20 to 40 minutes, mix evenly, and stir and react at 80 to 120° C. for 2 to 10 hours; after cooling to room temperature, add 200 to 400 parts of anhydrous ethanol and stir and react for 4 to 8 hours, centrifuge to separate the lignin solution, remove the ethanol by rotary evaporation at 45° C., then add 400 to 600 parts of deionized water and refrigerate at 0 to 4° C. for 48 hours, centrifuge again, and freeze-dry the precipitate to obtain cotton stalk lignin;

[0042] Step 3: Preparation of lignin / carboxymethyl cellulose composite solution

[0043] 1-3 parts of sodium carboxymethyl cellulose and 100-200 parts of deionized water are added to a reactor, stirred at 60-90°C for 2-4 hours until completely dissolved; then 0.2-1 parts of cotton stalk lignin are added, stirred at 400-500 rpm at 25°C for 0.5-1 hour, and then ultrasonically treated for 0.5-1 hour; then 5-10 parts of malic acid are added, stirred at 400 rpm at 60°C for 2-5 hours to obtain a lignin / carboxymethyl cellulose composite solution;

[0044] Step 4: Preparation of cellulose-based slow-release phosphate fertilizer and evaluation of leaching effect

[0045] Take 50-100 parts of monoammonium phosphate particles and add them into a coating pot, preheat at 100°C for 10-20 minutes, then spray 300-500 parts of lignin / carboxymethyl cellulose composite solution, and maintain the original temperature for coating; finally, cross-link the coated fertilizer at 140°C for 30-40 minutes to obtain lignin / carboxymethyl cellulose coated slow-release phosphate fertilizer.

[0046] Finally, a soil column leaching experiment was used to explore the release pattern of phosphorus nutrients in the soil from cellulose-based slow-release phosphate fertilizers. 100 portions of deionized water were added to the soil columns on the 1st, 3rd, 5th, 9th, 13th, 19th and 27th days to simulate rainfall leaching. The leaching solutions were collected and filtered, and the phosphorus content of the leaching solutions was determined by ammonium molybdate spectrophotometry to explore the leaching pattern of phosphate fertilizers in the soil. Each experimental group was measured three times in parallel.

[0047] Example 1

[0048] Step 1: Preparation of deep eutectic solvent

[0049] Choline chloride, formic acid and ferric chloride were added to a reaction bottle at a molar ratio of 1:1:0.01, and stirred at 90°C and 800 rpm until a uniform transparent solution was obtained to obtain a low eutectic solvent for later use;

[0050] Step 2: Extraction of cotton stalk lignin

[0051] Take 10 parts of low eutectic solvent and 1 part of dry cotton stalk powder through 80 mesh sieve, stir for 20 minutes to mix evenly, stir and react at 90°C for 5 hours; after cooling to room temperature, add 400 parts of anhydrous ethanol and stir and react for 4 hours, centrifuge to separate lignin solution, remove ethanol by rotary evaporation at 45°C, add 500 parts of deionized water and refrigerate at 4°C for 48 hours, centrifuge again, freeze-dry the precipitate to obtain cotton stalk lignin, and set aside;

[0052] Step 3: Preparation of lignin / carboxymethyl cellulose composite solution

[0053] 2.55 parts of sodium carboxymethyl cellulose and 150 parts of deionized water were added to a reactor, and stirred at 60°C for 2 hours until completely dissolved; 0.45 parts of cotton stalk lignin was added, and stirred at 400 rpm at 25°C for 0.5 hours, and then ultrasonically treated for 0.5 hours; 7.5 parts of malic acid were added, and stirred at 400 rpm at 60°C for 5 hours to obtain a lignin / carboxymethyl cellulose composite solution for later use;

[0054] Step 4: Preparation of cellulose-based slow-release phosphate fertilizer and evaluation of leaching effect

[0055] Take 100 parts of monoammonium phosphate particles and add them into the coating pot, preheat at 100°C for 20 minutes; then spray 450 parts of lignin / carboxymethyl cellulose composite solution and keep the temperature at 100°C for coating; finally, cross-link the coated fertilizer at 140°C for 40 minutes to obtain lignin / carboxymethyl cellulose coated slow-release phosphate fertilizer.

[0056] Finally, a soil column leaching experiment was used to explore the release pattern of phosphorus nutrients in the soil from cellulose-based slow-release phosphate fertilizers. 100 portions of deionized water were added to the soil columns on the 1st, 3rd, 5th, 9th, 13th, 19th and 27th days to simulate rainfall leaching. The leaching solutions were collected and filtered, and the phosphorus content of the leaching solutions was determined by ammonium molybdate spectrophotometry to explore the leaching pattern of phosphate fertilizers in the soil. Each experimental group was measured three times in parallel.

[0057] Example 2

[0058] Step 1: Preparation of deep eutectic solvent

[0059] Choline chloride, formic acid and ferric chloride were added to a reaction bottle at a molar ratio of 1:1:0.01, and stirred at 60°C and 800 rpm until a uniform transparent solution was obtained to obtain a low eutectic solvent for later use;

[0060] Step 2: Extraction of cotton stalk lignin

[0061] Take 5 parts of low eutectic solvent and 1 part of dry cotton stalk powder through 80 mesh sieve, stir for 20 minutes to mix evenly, stir and react at 90°C for 3 hours; after cooling to room temperature, add 200 parts of anhydrous ethanol and stir and react for 4 hours, centrifuge to separate lignin solution, remove ethanol by rotary evaporation at 45°C, add 500 parts of deionized water and refrigerate at 4°C for 48 hours, centrifuge again, freeze-dry the precipitate to obtain cotton stalk lignin, and set aside;

[0062] Step 3: Preparation of lignin / carboxymethyl cellulose composite solution

[0063] 2.25 parts of sodium carboxymethyl cellulose and 150 parts of deionized water were added to a reactor, and stirred at 60°C for 2 hours until completely dissolved; 0.75 parts of cotton stalk lignin were added, and stirred at 400 rpm at 25°C for 0.5 hours, and then ultrasonically treated for 0.5 hours; 7.5 parts of malic acid were added, and stirred at 400 rpm at 60°C for 4 hours to obtain a lignin / carboxymethyl cellulose composite solution for later use;

[0064] Step 4: Preparation of cellulose-based slow-release phosphate fertilizer and evaluation of leaching effect

[0065] Take 50 parts of monoammonium phosphate particles and add them to the coating pot, preheat at 100°C for 10 minutes; then spray 300 parts of lignin / carboxymethyl cellulose composite solution and keep the temperature at 100°C for coating; finally, cross-link the coated fertilizer at 140°C for 30 minutes to obtain lignin / carboxymethyl cellulose coated slow-release phosphate fertilizer.

[0066] Finally, a soil column leaching experiment was used to explore the release pattern of phosphorus nutrients in the soil from cellulose-based slow-release phosphate fertilizers. 100 portions of deionized water were added to the soil columns on the 1st, 3rd, 5th, 9th, 13th, 19th and 27th days to simulate rainfall leaching. The leaching solutions were collected and filtered, and the phosphorus content of the leaching solutions was determined by ammonium molybdate spectrophotometry to explore the leaching pattern of phosphate fertilizers in the soil. Each experimental group was measured three times in parallel.

[0067] Example 3

[0068] Step 1: Preparation of deep eutectic solvent

[0069] Choline chloride, formic acid and ferric chloride were added to a reaction bottle at a molar ratio of 1:1:0.01, and stirred at 80°C and 800 rpm until a uniform transparent solution was obtained to obtain a low eutectic solvent for later use;

[0070] Step 2: Extraction of cotton stalk lignin

[0071] Take 10 parts of low eutectic solvent and 1 part of dry cotton stalk powder through 80 mesh sieve, stir for 40 minutes to mix evenly, stir and react at 90°C for 2 hours; after cooling to room temperature, add 400 parts of anhydrous ethanol and stir and react for 4 hours, centrifuge to separate lignin solution, remove ethanol by rotary evaporation at 45°C, add 500 parts of deionized water and refrigerate at 4°C for 48 hours, centrifuge again, freeze-dry the precipitate to obtain cotton stalk lignin, and set aside;

[0072] Step 3: Preparation of lignin / carboxymethyl cellulose composite solution

[0073] 1.2 parts of sodium carboxymethyl cellulose and 100 parts of deionized water were added to a reactor, and stirred at 60°C for 2 hours until completely dissolved; then 0.8 parts of cotton stalk lignin was added, and stirred at 400 rpm at 25°C for 0.5 hours, and then ultrasonically treated for 0.5 hours; then 5 parts of malic acid were added, and stirred at 400 rpm at 60°C for 4 hours to obtain a lignin / carboxymethyl cellulose composite solution for later use;

[0074] Step 4: Preparation of cellulose-based slow-release phosphate fertilizer and evaluation of leaching effect

[0075] Take 100 parts of monoammonium phosphate particles and add them into the coating pot, preheat them at 100°C for 20 minutes. Then spray 500 parts of lignin / carboxymethyl cellulose composite solution and keep the temperature at 100°C for coating; cross-link the coated fertilizer at 140°C for 40 minutes, and finally obtain lignin / carboxymethyl cellulose coated slow-release phosphate fertilizer.

[0076] Finally, a soil column leaching experiment was used to explore the release pattern of phosphorus nutrients in the soil from cellulose-based slow-release phosphate fertilizers. 100 portions of deionized water were added to the soil columns on the 1st, 3rd, 5th, 9th, 13th, 19th and 27th days to simulate rainfall leaching. The leaching solutions were collected and filtered, and the phosphorus content of the leaching solutions was determined by ammonium molybdate spectrophotometry to explore the leaching pattern of phosphate fertilizers in the soil. Each experimental group was measured three times in parallel.

[0077] Example 4

[0078] Step 1: Preparation of deep eutectic solvent

[0079] Choline chloride, formic acid and ferric chloride were added into a reaction bottle in a molar ratio of 1:1:0.01, and stirred at 60°C and 750 rpm until a uniform transparent solution was obtained to obtain a low eutectic solvent for later use.

[0080] Step 2: Extraction of cotton stalk lignin

[0081] Take 10 parts of low eutectic solvent and 1 part of dry cotton stalk powder through 80 mesh sieve, stir for 40 minutes to mix evenly, stir and react at 90°C for 2 hours; after cooling to room temperature, add 400 parts of anhydrous ethanol and stir and react for 4 hours, centrifuge to separate lignin solution, remove ethanol by rotary evaporation at 45°C, add 500 parts of deionized water and refrigerate at 4°C for 48 hours, centrifuge again, freeze-dry the precipitate to obtain cotton stalk lignin, and set aside;

[0082] Step 3: Preparation of carboxymethyl cellulose solution

[0083] Take 3 parts of sodium carboxymethyl cellulose and 150 parts of deionized water and add them into the reactor, stir at 60°C for 2 hours until they are completely dissolved, and ultrasonically treat for 0.5 hours; then add 7.5 parts of malic acid, stir at 60°C and 400 rpm for 5 hours to obtain a carboxymethyl cellulose solution for later use;

[0084] Step 4: Preparation of cellulose-based slow-release phosphate fertilizer and evaluation of leaching effect

[0085] Take 100 parts of monoammonium phosphate particles and add them into a coating pot, preheat at 100°C for 20 minutes; then spray 500 parts of carboxymethyl cellulose solution and keep the temperature at 100°C for coating; cross-link the coated fertilizer at 140°C for 35 minutes to finally obtain lignin / carboxymethyl cellulose coated slow-release phosphate fertilizer.

[0086] Finally, a soil column leaching experiment was used to explore the release pattern of phosphorus nutrients in the soil from cellulose-based slow-release phosphate fertilizers. 100 portions of deionized water were added to the soil columns on the 1st, 3rd, 5th, 9th, 13th, 19th and 27th days to simulate rainfall leaching. The leaching solutions were collected and filtered, and the phosphorus content of the leaching solutions was determined by ammonium molybdate spectrophotometry to explore the leaching pattern of phosphate fertilizers in the soil. Each experimental group was measured three times in parallel.

[0087] The above description is only a preferred embodiment of the present invention and does not limit the technical scope of the present invention. Therefore, any slight modifications, equivalent changes and modifications made to the above embodiments based on the technical essence of the present invention are still within the scope of the technical solution of the present invention.

Claims

1. A method for preparing a cellulose-based slow-release phosphate fertilizer, characterized in that: The amount of material taken "parts" is weight parts, including the following steps: Step 1: Preparation of deep eutectic solvent Take choline chloride, formic acid and ferric chloride and add them into a reaction bottle, and stir under heating conditions until a uniform transparent solution is obtained to obtain a low eutectic solvent; Step 2: Extraction of cotton stalk lignin The low eutectic solvent and cotton stalk powder are taken, stirred and mixed evenly, and stirred and reacted under heating conditions; after cooling to room temperature, anhydrous ethanol is added and stirred and reacted, and a lignin solution is separated by centrifugation, the ethanol is removed, and deionized water is added and refrigerated, and the precipitate is freeze-dried to obtain cotton stalk lignin; Step 3: Preparation of lignin / carboxymethyl cellulose composite solution Sodium carboxymethyl cellulose and deionized water are added to a reactor, and stirred under heating conditions until they are completely dissolved; cotton stalk lignin is then added, and stirred under normal temperature conditions, and then subjected to ultrasonic treatment; malic acid is then added, and stirred under heating conditions to obtain a lignin / carboxymethyl cellulose composite solution; Step 4: Preparation of cellulose-based slow-release phosphate fertilizer Take monoammonium phosphate particles and add them into a coating pot, preheat them, then spray the lignin / carboxymethyl cellulose composite solution, and keep the original temperature for coating; finally, cross-link the coated fertilizer under heating conditions to obtain lignin / carboxymethyl cellulose coated slow-release phosphate fertilizer.

2. The method for preparing a cellulose-based slow-release phosphate fertilizer according to claim 1, characterized in that: In the first step, the molar ratio of choline chloride, formic acid and ferric chloride is 1:1-3:0.01-0.

1.

3. The method for preparing a cellulose-based slow-release phosphate fertilizer according to claim 1, characterized in that: In the first step, the heating temperature is 60-90° C., and the stirring speed is 300-800 rpm.

4. The method for preparing a cellulose-based slow-release phosphate fertilizer according to claim 1, characterized in that: In the second step, the amount of the low eutectic solvent added is 5 to 10 parts, and the amount of the cotton straw powder added is 1 part, which is dried and passed through an 80-mesh sieve.

5. The method for preparing a cellulose-based slow-release phosphate fertilizer according to claim 1, characterized in that: The stirring time of the low eutectic solvent and the cotton straw powder is 20 to 40 minutes, the heating condition is 80 to 120° C., and the stirring reaction time is 2 to 10 hours.

6. The method for preparing a cellulose-based slow-release phosphate fertilizer according to claim 1, characterized in that: In the second step, the amount of anhydrous ethanol added is 200 to 400 parts, and the stirring reaction time is 4 to 8 hours; The method for removing ethanol is to perform rotary evaporation at 45°C, add 400-600 parts of deionized water and refrigerate at 0-4°C for 48 hours.

7. The method for preparing a cellulose-based slow-release phosphate fertilizer according to claim 1, characterized in that: In the third step, the amount of sodium carboxymethyl cellulose added is 1-3 parts, the amount of deionized water added is 100-200 parts, the heating conditions for adding sodium carboxymethyl cellulose and deionized water into the reactor are 60-90° C., and the stirring time is 2-4 hours.

8. The method for preparing a cellulose-based slow-release phosphate fertilizer according to claim 1, characterized in that: In the third step, the amount of cotton stalk lignin added is 0.2-1 parts, the normal temperature condition is 25° C., the stirring speed is 400-500 rpm, the stirring time is 0.5-1 h, and the ultrasonic treatment time is 0.5-1 h.

9. The method for preparing a cellulose-based slow-release phosphate fertilizer according to claim 1, characterized in that: In the third step, the amount of malic acid added is 5 to 10 parts, the heating condition is 60° C., the stirring speed is 400 rpm, and the stirring time is 2 to 5 hours.

10. The method for preparing a cellulose-based slow-release phosphate fertilizer according to claim 1, characterized in that: In the fourth step, the amount of monoammonium phosphate particles added is 50 to 100 parts, the preheating condition is 100° C., and the preheating time is 10 to 20 minutes; the amount of lignin / carboxymethyl cellulose composite solution added is 300 to 500 parts; and the coated fertilizer is cross-linked at 140° C. for 30 to 40 minutes.

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