Method for preparing slow-release fertilizer by coating urea with cellulose subjected to two-step modification of sodium periodate oxidation coupling citric acid esterification
Through the oxidation of sodium periodate citrate esterification of two-step modified cellulose and beeswax envelope technology, the problems of low urea utilization and poor cellulose envelope sustained release performance are solved, and the efficient sustained release of urea is achieved and Resource utilization of industrial hemp straw.
Patent Information
- Application Number
- CN202411839583.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-13
- Publication Date
- 2025-02-07
AI Technical Summary
The utilization rate of existing urea and other soluble fertilizers is low, the sustained release performance of cellulose-covered sustained release fertilizers is poor, and the industrial hemp straw resources have not been effectively utilized.
The two-step modified cellulose was modified by sodium periodate oxidative coupling citrate esterification, cellulose was extracted through industrial hemp straw, and the esterification was carried out using microwave-assisted hydrothermal method, and combined with beeswax coating technology, urea sustained release fertilizer was prepared.
It improves the utilization efficiency of urea, extends the release time of urea, reduces environmental pollution, and realizes the resource utilization of industrial hemp straw.
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Figure CN119390501A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to a method for preparing a slow-release fertilizer by using coated urea through two-step modified cellulose by sodium periodate oxidation coupled with citric acid esterification. Background Art
[0002] Fertilizers are crucial in today's agricultural production, accounting for more than 40% of food production. However, due to factors such as volatilization, runoff and leaching, about 40% to 70% of nitrogen nutrients are lost after fertilizer application and are not fully utilized, resulting in resource waste and environmental pollution (such as lake eutrophication, soil quality degradation and groundwater pollution).
[0003] Slow-release fertilizers (SRFs) play an important role in delaying the release of fertilizer nutrients and improving nutrient utilization efficiency. Coated fertilizers are a major branch of SRFs, which are prepared by coating the surface of urea particles with some hydrophobic coating films. The coating matrix materials commonly used in slow-release fertilizers are mainly composed of sulfur, inorganic minerals, and natural or synthetic organic polymers. The brittleness of sulfur coatings is not conducive to storage and transportation, and it is easy to destroy microorganisms in the soil. Inorganic mineral materials are difficult to form films and have poor slow-release properties. Most organic polymers are synthetic polymers with high toxicity and are expensive. Therefore, the above materials have many unfavorable factors that limit their widespread application.
[0004] Natural polymers such as cellulose, starch, chitosan, and alginate are a class of very promising fertilizer coating materials. Cellulose in particular has the advantages of being renewable, biodegradable, and abundant in source. However, the presence of a large number of hydrogen bonds in cellulose molecules causes it to be insoluble in water and solvents, and therefore it cannot be directly used for coating urea fertilizers. Physical and chemical modification of cellulose can effectively solve the inherent defects of cellulose, presenting different physical and chemical properties, and thus being beneficial as a coating material for fertilizers. Therefore, the present invention provides a two-step modified cellulose by oxidation coupling esterification for the preparation of coated urea slow-release fertilizers. Summary of the invention
[0005] The purpose of the present invention is to solve the problems of low utilization rate of urea and other soluble fertilizers, poor slow-release performance of cellulose-coated slow-release fertilizers, and waste of industrial hemp straw, and to provide a preparation method of cellulose-sutured beeswax-coated urea slow-release fertilizer by two-step oxidative coupling esterification.
[0006] A method for preparing slow-release fertilizer by two-step modification of cellulose by sodium periodate oxidation coupled with citric acid esterification for coated urea is completed by the following steps:
[0007] 1. Extracting cellulose from industrial hemp straw: ①Put the cut industrial hemp straw into an oven at 60℃~80℃ and dry it for 20 hours to remove the moisture in the industrial hemp straw and obtain the dried industrial hemp straw; ② After taking out the dried industrial hemp stalks, put them into a grinder to grind the dried industrial hemp stalks to obtain the crushed industrial hemp stalk powder; ③ Mix the crushed industrial hemp straw powder with sodium hydroxide solution and react in a water bath for 1 h. After the solution is cooled, wash and filter the mixed solution to obtain straw powder after removing hemicellulose; In step 1③, the ratio of sodium hydroxide to deionized water is (4.5 g~22.5 g):(50 mL~250 mL); In step 1③, the ratio of industrial hemp straw to sodium hydroxide solution is (1 g~5 g):(50 mL~250 mL); ④ Mix the obtained straw powder with a mixed aqueous solution of acetic acid and sodium chlorite, react in a water bath for 1 h, and after the solution is cooled, wash, filter, and dry to obtain cellulose solids: In step 1④, the ratio of sodium chlorite, acetic acid and water is (0.55 g~2.75 g):(5 mL~25 mL):(50 mL~250 mL); In step 1④, the ratio of straw powder to mixed solution is (1 g~5 g):(50 mL~250 mL);
[0008] 2. Sodium periodate oxidized cellulose: ① Stirring the cellulose obtained in step 1 with 0.4% sodium periodate solution in the dark to obtain a dispersed cellulose aqueous solution; In step 2①, the ratio of cellulose to sodium periodate solution is (1 g~50 g):(10 mL~500 mL); ② Filter by suction, wash the product with ice water, stir with 1.5% sodium chlorite solution at room temperature, wash with distilled water, and filter by suction; In step 2②, the ratio of cellulose to sodium chlorite solution is (1 g~5 g):(4 g~20 g);
[0009] 3. Citric acid modified oxidized cellulose: ① Dispersing the cellulose obtained in step 2② in distilled water and stirring at room temperature to obtain a dispersed cellulose aqueous solution; The ratio of oxidized cellulose obtained in step 3 to distilled water is (1 g~5 g):(10 mL~50 mL); ② Add citric acid solid to the cellulose aqueous solution obtained in step 3①, and stir at room temperature to obtain a mixed dispersed solution of citric acid and cellulose; The ratio of oxidized cellulose obtained in step 3② to citric acid is (1 g~4 g):(5 g~20 g); ③ The mixed dispersion solution of citric acid and cellulose is transferred to a polytetrafluoroethylene-lined reactor, and the oxidized cellulose obtained in step 2② is subjected to microwave-assisted hydrothermal esterification; ④ The obtained crude esterification product is washed with deionized water and ethanol, and then dried and ground to obtain cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification;
[0010] 4. Preparation of the above-mentioned sodium periodate oxidation coupled with citric acid esterification two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer ① Add beeswax to ethyl acetate and stir at room temperature; In step 4①, the ratio of beeswax to ethyl acetate is (3 g ~ 20 g): (3 mL ~ 20 mL); ② Add the cellulose modified by sodium periodate oxidation coupled with citric acid esterification obtained in step 3 into the ethyl acetate solution of beeswax and stir at room temperature. ,; In step 4②, the ratio of cellulose modified by sodium periodate oxidation coupled with citric acid esterification to beeswax solution is (20g~1g):(20mL~1mL); ③Urea particles of uniform size and shape are selected for coating in a drum granulator with 1 to 5 coating layers, and then placed in an oven for drying to obtain a two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer by sodium periodate oxidation coupled with citric acid esterification;
[0011] Principles and advantages of the present invention:
[0012] 1. The present invention uses cellulose from discarded industrial hemp straw, which can realize the resource utilization of industrial hemp straw and reduce straw waste and pollution;
[0013] Second, the present invention uses a microwave-assisted hydrothermal method to prepare sodium periodate oxidation coupled with citric acid esterification two-step modified cellulose, which does not require complicated instruments and operation procedures, can achieve large-scale preparation, can effectively improve the performance deficiencies of ordinary straw cellulose, and lay the foundation for the utilization of cellulose;
[0014] 3. The two-step chemically modified cellulose composite beeswax-coated urea slow-release fertilizer of the present invention, which is coupled with sodium periodate oxidation and citric acid esterification, coats the two-step modified cellulose and beeswax on the outside of the urea ball, which reduces the speed at which water molecules enter the fertilizer, effectively prolongs the release of urea, improves the utilization efficiency of urea, and improves the pollution of urea to the environment. In addition, the modified cellulose coating material can be degraded and is environmentally friendly.
[0015] The invention can obtain a two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer through sodium periodate oxidation coupling citric acid esterification. BRIEF DESCRIPTION OF THE DRAWINGS
[0016] Figure 1 The flow chart of the preparation of the two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer by sodium periodate oxidation coupled with citric acid esterification;
[0017] Figure 2 are scanning electron microscope images, in which (a) is a scanning electron microscope image of industrial hemp straw cellulose, and (b) is a scanning electron microscope image of the two-step chemical modification of cellulose by sodium periodate oxidation coupled with citric acid esterification obtained in step 3 of Example 1;
[0018] Figure 3 The infrared images are respectively the infrared image of industrial hemp straw cellulose and the infrared image of cellulose chemically modified by two steps of sodium periodate oxidation coupled with citric acid esterification;
[0019] Figure 4 1 is the release curve of urea in water, (a) is the release curve of urea in water, (b) is the release curve of the two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer prepared in Example 1 by sodium periodate oxidation coupled with citric acid esterification in water;
[0020] Figure 5 1 is the release curve of urea in soil, (a) is the release curve of urea in soil, (b) is the release curve of the two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer prepared in Example 1 by sodium periodate oxidation coupled with citric acid esterification in soil;
[0021] Figure 6 The following are plant height diagrams of blank and fertilizer-treated plants at different periods. (a) shows the plant height after fertilizer application, and (b) shows the plant height of the urea control group. DETAILED DESCRIPTION
[0022] Specific implementation method 1: This implementation method is a method for preparing slow-release fertilizer by two-step modification of cellulose by sodium periodate oxidation coupled with citric acid esterification for coated urea, which is completed according to the following steps:
[0023] 1. Extracting cellulose from industrial hemp straw: ①Put the cut industrial hemp straw into an oven at 60℃~80℃ and dry it for 20 hours to remove the moisture in the industrial hemp straw and obtain the dried industrial hemp straw; ② After taking out the dried industrial hemp stalks, put them into a grinder to grind the dried industrial hemp stalks to obtain the crushed industrial hemp stalk powder; ③ Mix the crushed industrial hemp straw powder with sodium hydroxide solution and react in a water bath for 1 h. After the solution is cooled, wash and filter the mixed solution to obtain straw powder after removing hemicellulose; In step 1③, the ratio of sodium hydroxide to deionized water is (4.5 g~22.5 g):(50 mL~250 mL); In step 1③, the ratio of industrial hemp straw to sodium hydroxide solution is (1 g~5 g):(50 mL~250 mL); ④ Mix the obtained straw powder with a mixed aqueous solution of acetic acid and sodium chlorite, react in a water bath for 1 h, and after the solution is cooled, wash, filter, and dry to obtain cellulose solids; In step 1④, the ratio of sodium chlorite, acetic acid and water is (0.55 g~2.75 g):(5 mL~25 mL):(50 mL~250 mL); In step 1④, the ratio of straw powder to mixed solution is (1 g~5 g):(50 mL~250 mL);
[0024] 2. Sodium periodate oxidized cellulose: ① Stirring the cellulose obtained in step 1 with 0.4% sodium periodate solution in the dark to obtain a dispersed cellulose aqueous solution; In step 2①, the ratio of cellulose to sodium periodate solution is (1 g~50 g):(10 mL~500 mL); ② Filter by suction, wash the product with ice water, stir with 1.5% sodium chlorite solution at room temperature, wash with distilled water, and filter by suction; In step 2②, the ratio of cellulose to sodium chlorite solution is (1 g~5 g):(4 g~20 g);
[0025] 3. Citric acid modified oxidized cellulose: ① Dispersing the cellulose obtained in step 2② in distilled water and stirring at room temperature to obtain a dispersed cellulose aqueous solution; The ratio of oxidized cellulose obtained in step 3① to distilled water is (1 g~5 g):(10 mL~50 mL); ② Add citric acid solid to the cellulose aqueous solution obtained in step 3①, and stir at room temperature to obtain a mixed dispersed solution of citric acid and cellulose; The ratio of oxidized cellulose obtained in step 3② to citric acid is (1 g~4 g):(5 g~20 g); ③ The mixed dispersion solution of citric acid and cellulose is transferred to a polytetrafluoroethylene-lined reactor, and the oxidized cellulose obtained in step 2② is subjected to microwave-assisted hydrothermal esterification; ④ The obtained crude esterification product is washed with deionized water and ethanol, and then dried and ground to obtain cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification;
[0026] 4. Preparation of the above-mentioned sodium periodate oxidation coupled with citric acid esterification two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer ① Add beeswax to ethyl acetate and stir at room temperature; In step 4①, the ratio of beeswax to ethyl acetate is (3 g to 20 g): (3 mL to 20 mL); ② Add the cellulose modified by sodium periodate oxidation coupled with citric acid esterification obtained in step 3 into the ethyl acetate solution of beeswax and stir at room temperature; In step 4②, the ratio of cellulose modified by sodium periodate oxidation coupled with citric acid esterification in two steps to beeswax solution is (20g-1g): (20mL-1mL); ③Urea particles with uniform size and shape are selected for coating in a drum granulator, and then placed in an oven for drying to obtain a two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer by sodium periodate oxidation coupled with citric acid esterification;
[0027] Specific implementation method 2: This implementation method is different from the specific implementation method 1 in that the water bath temperature in step 1 ③ is 60° C. to 70° C. The other steps are the same as those in the specific implementation method 1.
[0028] Specific implementation method 3: This implementation method is different from specific implementation method 1 in that: the water bath temperature in step 1 ④ is 70 ℃ to 80 ℃, and the number of water washing in step 1 ④ is 3 to 4 times until the cellulose has no sour taste. The other steps are the same as those in specific implementation method 1.
[0029] Specific implementation method 4: This implementation method is different from the specific implementation method 1 in that the stirring speed in step 2① is 300 r / min~800 r / min and the stirring time is 6 h. The other steps are the same as those in the specific implementation method 1.
[0030] Specific implementation method 5: This implementation method is different from the specific implementation method 1 in that the stirring speed in step 2② is 300 r / min~800 r / min and the stirring time is 6 h. The other steps are the same as those in the specific implementation method 1.
[0031] Specific embodiment 6: This embodiment differs from specific embodiment 1 in that the ratio of cellulose to citric acid in step 3② is (1 g to 4 g): (5 g to 20 g). The other steps are the same as those in specific embodiment 1.
[0032] Specific embodiment 7: This embodiment differs from specific embodiment 1 in that: in step 3③, the esterification temperature is 120°C to 160°C, and the esterification time is 0.5 h to 2 h. The other steps are the same as those in specific embodiment 1.
[0033] Specific implementation method 8: This implementation method is different from specific implementation method 1 in that: in step 4, ① the stirring speed is 300 r / min~800 r / min, and the stirring time is 12 h. The other steps are the same as those in specific implementation method 1.
[0034] Specific embodiment 9: This embodiment differs from specific embodiment 1 in that the number of coating layers in step 4③ is 1 to 5. The other steps are the same as those in specific embodiment 1.
[0035] Specific embodiment 10: This embodiment differs from specific embodiment 1 in that: in step 4③, the drying temperature in the oven is 45°C to 65°C, and the drying time is 12 h to 24 h. The other steps are the same as those in specific embodiment 1.
[0036] The following examples are used to verify the beneficial effects of the present invention:
[0037] Example 1: A method for preparing a slow-release fertilizer by two-step modification of cellulose by sodium periodate oxidation coupled with citric acid esterification for coated urea is accomplished by the following steps: 1. Extracting cellulose from industrial hemp straw: ①Put the cut industrial hemp straw into an oven at 60℃~80℃ and dry it for 20 hours to remove the moisture in the industrial hemp straw and obtain the dried industrial hemp straw; ② After taking out the dried industrial hemp stalks, put them into a grinder to grind the dried industrial hemp stalks to obtain the crushed industrial hemp stalk powder; ③ Mix 10 g of crushed industrial hemp straw powder with 200 mL of 8%wt sodium hydroxide solution, react in a 60°C water bath for 1 h, and after the solution is cooled, wash and filter the mixed solution to obtain straw powder after removing hemicellulose; ④ Mix the obtained straw powder with 250 mL of a mixed solution containing 25 mL of acetic acid and 2.75 mL of sodium chlorite, and react in a 70 °C water bath for 1 h. After the solution is cooled, wash and filter until the solid has no sour taste, and then dry to obtain cellulose solid;
[0038] 2. Sodium periodate oxidized cellulose: ① Stir 1.0015 g of cellulose obtained in step 1 with 50 mL of 0.4% sodium periodate solution in the dark for 6 h to obtain a dispersed cellulose aqueous solution; ② Filter with suction, wash the product with ice water, stir with 5 mL 1.5% sodium chlorite solution at room temperature for 6 h, wash with distilled water, and filter with suction;
[0039] 3. Citric acid modified oxidized cellulose ① Disperse 1.0011 g of oxidized cellulose obtained in step 2② in 5 mL of distilled water and stir at room temperature to obtain a dispersed cellulose aqueous solution; ② Add 4.0052 g of citric acid solid to the dispersed cellulose aqueous solution and stir at room temperature to obtain a mixed dispersed solution of citric acid and cellulose; ③ The mixed dispersion solution of citric acid and cellulose was transferred into a polytetrafluoroethylene-lined reactor, and the esterified oxidized cellulose was prepared by microwave-assisted hydrothermal method at 140 °C for 40 min. ④ The obtained crude esterification product is washed with deionized water and ethanol, and then dried and ground to obtain cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification;
[0040] 4. Preparation of the above-mentioned sodium periodate oxidation coupled with citric acid esterification two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer ① Add 3 g of beeswax to 20 mL of ethyl acetate and stir at room temperature; ② 1.0014 g of cellulose modified by two steps of sodium periodate oxidation coupled with citrate esterification obtained in step 3 was added to 20 mL of ethyl acetate solution of beeswax and stirred at room temperature; ③Urea particles with uniform size and shape were selected and coated with one layer in a drum granulator, and then placed in an oven and dried at 60 ℃ for 24 h to obtain a two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer by sodium periodate oxidation coupled with citric acid esterification;
[0041] Example 2: A method for preparing slow-release fertilizer by two-step modification of cellulose by sodium periodate oxidation coupled with citric acid esterification for coated urea is accomplished by the following steps:
[0042] 1. Extracting cellulose from industrial hemp straw: ①Put the cut industrial hemp straw into an oven at 60℃~80℃ and dry it for 20 hours to remove the moisture in the industrial hemp straw and obtain the dried industrial hemp straw; ② After taking out the dried industrial hemp stalks, put them into a grinder to grind the dried industrial hemp stalks to obtain the crushed industrial hemp stalk powder; ③ Mix 10 g of crushed industrial hemp straw powder with 200 mL of 8%wt sodium hydroxide solution, react in a 60°C water bath for 1 h, and after the solution is cooled, wash and filter the mixed solution to obtain straw powder after removing hemicellulose; ④ Mix the obtained straw powder with 250 mL of a mixed solution containing 25 mL of acetic acid and 2.75 mL of sodium chlorite, and react in a 70 °C water bath for 1 h. After the solution is cooled, wash and filter until the solid has no sour taste, and then dry to obtain cellulose solid;
[0043] 2. Sodium periodate oxidized cellulose: ① Stir 1.0009 g of cellulose obtained in step 1 with 50 mL of 0.4% sodium periodate solution in the dark for 6 h to obtain a dispersed cellulose aqueous solution; ② Filter with suction, wash the product with ice water, stir with 5 mL 1.5% sodium chlorite solution at room temperature for 6 h, wash with distilled water, and filter with suction;
[0044] 3. Citric acid modified oxidized cellulose ① Disperse 1.0015 g of oxidized cellulose obtained in step 2② in 5 mL of distilled water and stir at room temperature to obtain a dispersed cellulose aqueous solution; ② Add 4.0061 g of citric acid solid to the dispersed cellulose aqueous solution and stir at room temperature to obtain a mixed dispersed solution of citric acid and cellulose; ③ The mixed dispersion solution of citric acid and cellulose was transferred to a polytetrafluoroethylene-lined reactor, and the oxidized cellulose was esterified by microwave-assisted hydrothermal method at 140 °C for 40 min. ④ The obtained crude esterification product is washed with deionized water and ethanol, and then dried and ground to obtain cellulose citrate;
[0045] 4. Preparation of the above-mentioned sodium periodate oxidation coupled with citric acid esterification two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer ① Add 3 g of beeswax to 20 mL of ethyl acetate and stir at room temperature; ② Add 1.0035 g of cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification obtained in step 3 into 20 mL of ethyl acetate solution of beeswax and stir at room temperature; ③Urea particles of uniform size and shape were selected and coated with two layers in a drum granulator, and then placed in an oven and dried at 60°C for 24 hours to obtain a two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer by sodium periodate oxidation coupled with citric acid esterification;
[0046] Example 3: A method for preparing slow-release fertilizer by two-step modification of cellulose by sodium periodate oxidation coupled with citric acid esterification for coated urea is accomplished by the following steps:
[0047] 1. Extracting cellulose from industrial hemp straw: ①Put the cut industrial hemp straw into an oven at 60℃~80℃ and dry it for 20 hours to remove the moisture in the industrial hemp straw and obtain the dried industrial hemp straw; ② After taking out the dried industrial hemp stalks, put them into a grinder to grind the dried industrial hemp stalks to obtain the crushed industrial hemp stalk powder; ③ Mix 10 g of crushed industrial hemp straw powder with 200 mL of 8%wt sodium hydroxide solution, react in a 60°C water bath for 1 h, and after the solution is cooled, wash and filter the mixed solution to obtain straw powder after removing hemicellulose; ④ Mix the obtained solid with 250 mL of a mixed solution containing 25 mL of acetic acid and 2.75 mL of sodium chlorite, and react in a 70°C water bath for 1 h. After the solution is cooled, wash and filter until the solid has no sour taste, and then dry to obtain cellulose solid;
[0048] 2. Sodium periodate oxidized cellulose: ① Stir 1.0019 g of cellulose obtained in step 1 with 50 mL of 0.4% sodium periodate solution in the dark for 6 h to obtain a dispersed cellulose aqueous solution; ② Filter with suction, wash the product with ice water, stir with 5 mL 1.5% sodium chlorite solution at room temperature for 6 h, wash with distilled water, and filter with suction;
[0049] 3. Citric acid modified oxidized cellulose ① Disperse 1.0021 g of oxidized cellulose obtained in step 2② in 5 mL of distilled water, and stir at room temperature to obtain a dispersed cellulose aqueous solution; ② Add 4.0012 g of citric acid solid to the dispersed cellulose aqueous solution and stir at room temperature to obtain a mixed dispersed solution of citric acid and cellulose; ③ The mixed dispersion solution of citric acid and cellulose was transferred to a polytetrafluoroethylene-lined reactor, and the esterified oxidized cellulose was prepared by microwave-assisted hydrothermal method at 140 °C for 40 min. ④ The obtained crude esterification product is washed with deionized water and ethanol, and then dried and ground to obtain cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification;
[0050] 4. Preparation of the above-mentioned sodium periodate oxidation coupled with citric acid esterification two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer ① Add 3 g of beeswax to 20 mL of ethyl acetate and stir at room temperature; ② Add 1.0035 g of cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification obtained in step 3 into 20 mL of ethyl acetate solution of beeswax and stir at room temperature; ③Urea particles with uniform size and shape were selected and coated with three layers in a drum granulator, and then placed in an oven and dried at 60 ℃ for 24 h to obtain a two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer by sodium periodate oxidation coupled with citric acid esterification;
[0051] Example 4: A method for preparing a slow-release fertilizer by two-step modification of cellulose by sodium periodate oxidation coupled with citric acid esterification for coated urea is accomplished by the following steps:
[0052] 1. Extracting cellulose from industrial hemp straw: ①Put the cut industrial hemp straw into an oven at 60℃~80℃ and dry it for 20 hours to remove the moisture in the industrial hemp straw and obtain the dried industrial hemp straw; ② After taking out the dried industrial hemp stalks, put them into a grinder to grind the dried industrial hemp stalks to obtain the crushed industrial hemp stalk powder; ③ Mix 10 g of crushed industrial hemp straw powder with 200 mL of 8%wt sodium hydroxide solution, react in a 60°C water bath for 1 h, and after the solution is cooled, wash and filter the mixed solution to obtain straw powder after removing hemicellulose; ④ Mix the obtained solid with 250 mL of a mixed solution containing 25 mL of acetic acid and 2.75 mL of sodium chlorite, and react in a 70°C water bath for 1 h. After the solution is cooled, wash and filter until the solid has no sour taste, and then dry to obtain cellulose solid;
[0053] 2. Sodium periodate oxidized cellulose: ① Stir 1.0021 g of cellulose obtained in step 1 with 50 mL of 0.4% sodium periodate solution in the dark for 6 h to obtain a dispersed cellulose aqueous solution; ② Filter with suction, wash the product with ice water, stir with 5 mL 1.5% sodium chlorite solution at room temperature for 6 h, wash with distilled water, and filter with suction;
[0054] 3. Citric acid modified oxidized cellulose ① Disperse 1.0017 g of oxidized cellulose obtained in step 2② in 5 mL of distilled water and stir at room temperature to obtain a dispersed cellulose aqueous solution; ② Add 4.0107 g of citric acid solid to the dispersed cellulose aqueous solution and stir at room temperature to obtain a mixed dispersed solution of citric acid and cellulose; ③ The mixed dispersion solution of citric acid and cellulose was transferred to a polytetrafluoroethylene-lined reactor, and the esterified oxidized cellulose was prepared by microwave-assisted hydrothermal method at 140 °C for 40 min. ④ The obtained crude esterification product is washed with deionized water and ethanol, and then dried and ground to obtain cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification;
[0055] 4. Preparation of the above-mentioned sodium periodate oxidation coupled with citric acid esterification two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer ① Add 3 g of beeswax to 20 mL of ethyl acetate and stir at room temperature; ② Add 1.1054 g of cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification obtained in step 3 into 20 mL of ethyl acetate solution of beeswax and stir at room temperature; ③Urea particles with uniform size and shape were selected and coated with four layers in a drum granulator, and then placed in an oven and dried at 60 ℃ for 24 h to obtain a two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer by sodium periodate oxidation coupled with citric acid esterification;
[0056] Example 5: A method for preparing slow-release fertilizer by two-step modification of cellulose by sodium periodate oxidation coupled with citric acid esterification for coated urea is accomplished by the following steps:
[0057] 1. Extracting cellulose from industrial hemp straw: ①Put the cut industrial hemp straw into an oven at 60℃~80℃ and dry it for 20 hours to remove the moisture in the industrial hemp straw and obtain the dried industrial hemp straw; ② After taking out the dried industrial hemp stalks, put them into a grinder to grind the dried industrial hemp stalks to obtain the crushed industrial hemp stalk powder; ③ Mix 10 g of crushed industrial hemp straw powder with 200 mL of 8%wt sodium hydroxide solution, react in a 60°C water bath for 1 h, and after the solution is cooled, wash and filter the mixed solution to obtain straw powder after removing hemicellulose; ④ Mix the obtained solid with 250 mL of a mixed solution containing 25 mL of acetic acid and 2.75 mL of sodium chlorite, and react in a 70°C water bath for 1 h. After the solution is cooled, wash and filter until the solid has no sour taste, and then dry to obtain cellulose solid;
[0058] 2. Sodium periodate oxidized cellulose: ① Stir 1.0051 g of cellulose obtained in step 1 with 50 mL of 0.4% sodium periodate solution in the dark for 6 h to obtain a dispersed cellulose aqueous solution; ② Filter with suction, wash the product with ice water, stir with 5 mL 1.5% sodium chlorite solution at room temperature for 6 h, wash with distilled water, and filter with suction;
[0059] 3. Citric acid modified oxidized cellulose ① Disperse 1.0196 g of oxidized cellulose obtained in step 2② in 5 mL of distilled water and stir at room temperature to obtain a dispersed cellulose aqueous solution; ② Add 4.0039 g of citric acid solid to the dispersed cellulose aqueous solution and stir at room temperature to obtain a mixed dispersed solution of citric acid and cellulose; ③ The mixed dispersion solution of citric acid and cellulose was transferred to a polytetrafluoroethylene-lined reactor, and the esterified oxidized cellulose was prepared by microwave-assisted hydrothermal method at 140 °C for 40 min. ④ The obtained crude esterification product is washed with deionized water and ethanol, and then dried and ground to obtain cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification;
[0060] 4. Preparation of the above-mentioned sodium periodate oxidation coupled with citric acid esterification two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer ① Add 3 g of beeswax to 20 mL of ethyl acetate and stir at room temperature; ② Add 1.0129 g of cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification obtained in step 3 into 20 mL of ethyl acetate solution of beeswax and stir at room temperature; ③Urea particles with uniform size and shape were selected and coated with 5 layers in a drum granulator, and then placed in an oven and dried at 60 ℃ for 24 h to obtain a two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer by sodium periodate oxidation coupled with citric acid esterification;
[0061] Detection of urea in the two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer prepared by sodium periodate oxidation coupled with citric acid esterification in Examples 1 to 5: urea reacts with p-dimethylaminobenzaldehyde under acidic conditions to generate a lemon-colored substance, and the urea content can be determined by ultraviolet spectrophotometry. According to the European Standards Committee, the slow-release fertilizer should have several standards: that is, at 25°C (1) the release rate of nutrients in the fertilizer within 24 hours (that is, the chemical form of the fertilizer is converted into an effective form that can be used by plants) does not exceed 15%; (2) the nutrient release rate within 28 days does not exceed 75%; (3) within the specified time, the nutrient release rate is not less than 75%; (4) the nutrient release curve of the special controlled-release fertilizer is consistent with the nutrient absorption curve of the corresponding crop.
[0062] The 10-day release rate of the two-step chemically modified cellulose composite beeswax-coated urea slow-release fertilizer prepared in Example 1 by sodium periodate oxidation coupled with citric acid esterification in soil was 24.39%;
[0063] The 10-day release rate of the two-step chemically modified cellulose composite beeswax-coated urea slow-release fertilizer prepared in Example 2 by sodium periodate oxidation coupled with citric acid esterification in soil was 22.26%;
[0064] The 10-day release rate of the two-step chemically modified cellulose composite beeswax-coated urea slow-release fertilizer prepared in Example 3 by sodium periodate oxidation coupled with citric acid esterification in soil was 19.03%;
[0065] The 10-day release rate of the two-step chemically modified cellulose composite beeswax-coated urea slow-release fertilizer prepared in Example 4 in the soil was 16.57%;
[0066] The 10-day release rate of the two-step chemically modified cellulose composite beeswax-coated urea slow-release fertilizer prepared in Example 5 by sodium periodate oxidation coupled with citric acid esterification in the soil was 16.12%.
[0067] Figure 1 This is a flow chart for the preparation of a two-step chemically modified cellulose composite beeswax-coated urea slow-release fertilizer by sodium periodate oxidation coupled with citric acid esterification.
[0068] Figure 2 The following are scanning electron microscope images. (a) is a scanning electron microscope image of industrial hemp straw cellulose, and (b) is a scanning electron microscope image of the two-step chemical modification of cellulose by sodium periodate oxidation coupled with citric acid esterification obtained in step 3 of Example 1. Figure 2 It can be seen that the surface of industrial hemp straw cellulose is rough, and the surface of cellulose chemically modified by two steps of sodium periodate oxidation coupled with citric acid esterification is smooth, which is surface modification.
[0069] Figure 3The infrared spectra are shown in Figure (a), where (b) is an infrared spectra curve of industrial hemp straw cellulose, and (c) is an infrared spectra curve of the two-step chemical modification of cellulose by sodium periodate oxidation coupled with citric acid esterification obtained in step 3 of Example 1. Figure 3 It can be seen that in (b), 1730 cm -1 The C=O stretching vibration absorption of the ester group, 1160 cm -1 and 1110 cm -1 is the CO of cellulose, indicating that the cellulose is modified.
[0070] Figure 4 The release curve of urea in water, (a) is the release curve of ordinary urea in water, and (c) is the release curve of the two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer prepared in Example 1 by sodium periodate oxidation coupled with citric acid esterification. Figure 4 It can be seen that ordinary urea is released fastest in water, while the two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer prepared in Comparative Example 1 by sodium periodate oxidation coupled with citric acid esterification, because the urea is coated in modified cellulose and beeswax, the hydrophobic film prevents the entry of water, reduces the contact between urea and water, and thus slows down the release of the fertilizer.
[0071] Figure 5 The release curve of urea in soil, (a) is the release curve of urea in soil, and (b) is the release curve of the two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer prepared in Example 1 by sodium periodate oxidation coupled with citric acid esterification. Figure 5 It can be seen that the initial release rate of urea in soil is very fast, while the two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer by sodium periodate oxidation coupled with citric acid esterification is released slowly in soil. The initial release rate is slower than that in water because there is less free water in the soil, and the exchange rate between free water and fertilizer in the soil is reduced, thereby reducing the release of urea.
[0072] Figure 6 The following are the plant heights of blank and fertilizer-treated plants at different times. (a) is the plant height of the blank control, and (b) is the plant height of the fertilizer-treated group. Figure 6 It can be seen that the plant height of the blank group was 38.4 cm after 5 weeks, and the plant height of the plants applied with fertilizer was 44.5 cm, indicating that the fertilizer played a significant role in promoting the growth of crops.
Claims
1. A method for preparing slow-release fertilizer by coating urea with cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification, characterized in that A method for preparing a cellulose composite beeswax coated urea slow-release fertilizer by two-step modification treatment of cellulose by first oxidation with sodium periodate and then esterification with citric acid is completed by the following steps:
1. Extracting cellulose from industrial hemp straw: ①Put the cut industrial hemp straw into an oven at 60℃~80℃ and dry it for 20 hours to remove the moisture in the industrial hemp straw and obtain the dried industrial hemp straw; ② After taking out the dried industrial hemp stalks, put them into a grinder to grind the dried industrial hemp stalks to obtain the crushed industrial hemp stalk powder; ③ Mix the crushed industrial hemp straw powder with sodium hydroxide solution and react in a water bath for 1 h. After the solution is cooled, wash and filter the mixed solution to obtain straw powder after removing hemicellulose; In step 1③, the ratio of sodium hydroxide to deionized water is (4.5 g~22.5 g):(50 mL~250 mL); In step 1③, the ratio of industrial hemp straw to sodium hydroxide solution is (1 g~5 g):(50 mL~250 mL); ④ Mix the obtained straw powder with a mixed aqueous solution of acetic acid and sodium chlorite, react in a water bath for 1 h, and after the solution is cooled, wash, filter, and dry to obtain cellulose solids; In step 1④, the ratio of sodium chlorite, acetic acid and water is (0.55 g~2.75 g):(5 mL~25 mL):(50 mL~250 mL); In step 1④, the ratio of straw powder to mixed solution is (1 g~5 g):(50 mL~250 mL); 2. Sodium periodate oxidized cellulose: ① Stirring the cellulose obtained in step 1 with 0.4% sodium periodate solution in the dark to obtain a dispersed cellulose aqueous solution; In step 2①, the ratio of cellulose to sodium periodate solution is (1 g~50 g):(10 mL~500 mL); ② Filter by suction, wash the product with ice water, stir with 1.5% sodium chlorite solution at room temperature, wash with distilled water, and filter by suction; In step 2②, the ratio of cellulose to sodium chlorite solution is (1 g~5 g):(4 g~20 g); 3. Citric acid modified oxidized cellulose: ① Dispersing the cellulose obtained in step 2② in distilled water and stirring at room temperature to obtain a dispersed cellulose aqueous solution; The ratio of the oxidized cellulose obtained in step 3① to distilled water is (1 g~5 g):(10 mL~50 mL); ② Add citric acid solid to the cellulose aqueous solution obtained in step 3①, and stir at room temperature to obtain a mixed dispersed solution of citric acid and cellulose; The ratio of oxidized cellulose obtained in step 3② to citric acid is (1 g~4 g):(5 g~20 g); ③ The mixed dispersion solution of citric acid and cellulose is transferred to a polytetrafluoroethylene-lined reactor, and the cellulose obtained in step 2② of the esterification treatment is prepared by microwave-assisted hydrothermal method; ④ The obtained crude esterification product is washed with deionized water and ethanol, and then dried and ground to obtain a cellulose ester modified by two steps of sodium periodate oxidation coupling citric acid esterification; 4. Preparation of the above-mentioned sodium periodate oxidation coupled with citric acid esterification two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer ① Add beeswax to ethyl acetate and stir at room temperature; In step 4①, the ratio of beeswax to ethyl acetate is (3 g~20 g):(3 mL~20 mL); ② Add the cellulose modified by sodium periodate curing coupled with citric acid esterification obtained in step 3 into the ethyl acetate solution of beeswax and stir at room temperature; In step 4②, the ratio of cellulose modified by sodium periodate oxidation coupled with citric acid esterification to beeswax solution is (20 g~1 g): (20 mL~1 mL) ③Urea particles of uniform size and shape are selected and coated in a drum granulator with 1 to 5 coating layers, and then placed in an oven for drying to obtain a two-step chemically modified cellulose composite beeswax coated urea slow-release fertilizer by sodium periodate oxidation coupled with citric acid esterification.
2. The method for preparing a slow-release fertilizer by coating urea with cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification according to claim 1, characterized in that In step 2①, the stirring speed is 300r / min~800r / min, and the stirring time is 6h.
3. The method for preparing a slow-release fertilizer by coating urea with cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification according to claim 1, characterized in that In step 2②, the stirring speed is 300r / min~800r / min, and the stirring time is 6h.
4. The method for preparing a slow-release fertilizer by coating urea with cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification according to claim 1, characterized in that In step 3③, the esterification temperature is 120°C~160°C, and the esterification time is 0.5h~2h.
5. The method for preparing a slow-release fertilizer by coating urea with cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification according to claim 1, characterized in that In step 4①, the stirring speed is 300r / min~800r / min, and the stirring time is 12h.
6. The method for preparing a slow-release fertilizer by coating urea with cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification according to claim 1, characterized in that In step 4②, the stirring speed is 300r / min~800r / min, and the stirring time is 30min.
7. The method for preparing a slow-release fertilizer by coating urea with cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification according to claim 1, characterized in that In step 4③, the number of coating layers is 1 to 5.
8. The method for preparing a slow-release fertilizer by coating urea with cellulose modified by two steps of sodium periodate oxidation coupled with citric acid esterification according to claim 1, characterized in that In step 4③, the drying temperature in the oven is 45°C~65°C, and the drying time is 12h~24h.