Environment-friendly slow release fertilizer and preparation method thereof

Abstract

The invention discloses an environment-friendly slow release fertilizer and a preparation method thereof, and belongs to the technical field of fertilizer mixture preparation. The preparation method comprises the following steps: mixing and stirring a mussel extract-polysaccharide-nitrogen fertilizer complex, an inorganic fertilizer and water according to a weight part ratio of (1-2): (5-7): (15-23), heating to 50-60 DEG C to form a dispersion solution, mixing and stirring the dispersion solution and a calcium salt according to a weight part ratio of 1: (0.005-0.01), cooling to 20-25 DEG C, and reacting for 20-24 hours to obtain a viscous mixture; and drying, dewatering and crushing the viscous mixture to obtain the environment-friendly slow-release fertilizer. According to the environment-friendly slow-release fertilizer, the mussel extract with a good adhesion effect and the carboxymethyl cellulose or the hyaluronic acid with biocompatibility are used as carriers, through the synergistic cooperation of an amide structure, an imine structure and metal coordination, wrapping of a nitrogen fertilizer and an inorganic fertilizer is achieved, and finally the environment-friendly slow-release fertilizer is obtained.

Description

Technical Field

[0001] The invention belongs to the technical field of fertilizer mixture preparation, and in particular relates to an environmentally friendly slow-release fertilizer and a preparation method thereof. Background Art

[0002] Although traditional chemical fertilizers can quickly provide nutrients, their improper use often leads to environmental problems such as soil degradation and water pollution. In order to solve these problems, slow-release fertilizers came into being. Slow-release fertilizers have gradually become an indispensable fertilizer choice in modern agriculture due to their unique release mechanism and nutrient supply characteristics. In the national standard (GB / T 23348-2009), the definition of slow-release fertilizers is: chemical fertilizers that slowly release effective nutrients for crops over time through chemical compound or physical action of nutrients. Slow-release fertilizers are fertilizers made by coating, encapsulation and adding inhibitors. After being applied to the soil, they are converted into effective nutrients absorbed by plants and released more slowly than ordinary fertilizers. After a one-time application, slow release can meet the physiological needs of plant growth and development, improve fertilizer utilization, save labor and fertilizer, and reduce the pollution caused by fertilizer loss to the environment. Considering resource utilization, environmental protection and other aspects, there is a good development space.

[0003] Slow-release fertilizers can be divided into the following categories based on their release characteristics and material composition: (1) Chemical slow-release fertilizers: This type of fertilizer is made by chemical synthesis, and common ones include slow-release urea, slow-release phosphate fertilizers, and slow-release potassium fertilizers. They usually change the chemical structure of chemical fertilizers so that nutrients can be slowly released in the soil. (2) Physical slow-release fertilizers: This type of fertilizer usually controls the release rate of fertilizers through physical methods such as coating, particle encapsulation, etc. For example, polymer-coated granular fertilizers can slowly release nutrients under conditions of moisture or temperature changes. (3) Biological slow-release fertilizers: Biological slow-release fertilizers gradually release nutrients through the action of microorganisms or biological materials. For example, some microorganisms can decompose organic matter and release nutrients needed by plants.

[0004] Patent CN113582771A discloses a method for preparing a polymer-based slow-release fertilizer. The invention mixes a compound containing a mercapto monomer and a compound containing an acrylate monomer to form a solution; immerses the fertilizer in the solution, then takes out the fertilizer and places it in a triethylamine gas environment. After 1 to 8 hours, the fertilizer is taken out to obtain a slow-release fertilizer. The mercapto monomer and the acrylate monomer react and cross-link, thereby coating the surface of the fertilizer with a layer of hydrophobic polymer, so that the fertilizer has a slow-release characteristic.

[0005] Patent CN113816794A discloses a method for preparing a lignin-based water-retaining double-layer slow-release fertilizer. The invention comprises the following steps: blending polyvinyl alcohol and a cellulose derivative to obtain a mixed liquid for use; grafting and polymerizing an acrylic acid-acrylamide copolymer with a lignin derivative to obtain a lignin-based water absorbent; spraying the mixed solution obtained by blending evenly on the surface of fertilizer particles, and repeatedly coating to obtain a single-layer coated fertilizer; evenly coating the pre-ground lignin-based water absorbent powder on the outer layer of the single-layer coated fertilizer, and finally drying the fertilizer at 55°C to obtain a double-layer coated slow-release fertilizer.

[0006] Patent CN112624865A discloses a water-retaining slow-release fertilizer and its preparation method. The invention places fertilizer particles in a coating machine, adds a polycaprolactone-polyurethane block copolymer solution, performs coating treatment, and dries and cools to obtain a coated material; the coated material is placed in a coating machine, performs a secondary coating treatment, and dries and cools to obtain a water-retaining slow-release fertilizer. By coating the fertilizer core, the first coating forms a slow-release layer, and the second coating forms a water-retaining layer, which can ensure a good slow-release speed while having excellent water-retaining performance.

[0007] Although the above invention has made some progress in slow-release fertilizers, some polymer materials may have harmful effects on the environment due to degradation. Even if the function of slow-release fertilizers can be achieved, long-term use may be more persistent in the environment, leading to its accumulation in the ecosystem, thereby affecting the ecological balance of soil and water.

[0008] Materials of biological origin come from animals, plants or microorganisms. These materials are renewable and have good degradation properties. Therefore, using biological materials of biological origin to prepare fertilizers with slow-release function is of great significance to environmental protection. Summary of the invention

[0009] In view of the deficiencies of the prior art, the present invention utilizes mussel extracts with good adhesion effect and carboxymethyl cellulose or hyaluronic acid with biocompatibility as carriers, and realizes the encapsulation of nitrogen fertilizer and inorganic fertilizer through the synergistic coordination of amide structure, imine structure and metal coordination, and finally obtains environmentally friendly slow-release fertilizer, which solves the technical problems raised in the background technology. Specifically, the technical solution of the present invention includes the following contents:

[0010] One of the purposes of the present invention is to provide a method for preparing an environmentally friendly slow-release fertilizer, the preparation method comprising the following steps:

[0011] The mussel extract-polysaccharide-nitrogen fertilizer complex, inorganic fertilizer and water are mixed and stirred in a weight ratio of 1-2:5-7:15-23, heated to 50°C-60°C to form a dispersed solution, the dispersed solution and calcium salt are mixed and stirred in a weight ratio of 1:0.005-0.01, cooled to 20°C-25°C, reacted for 20h-24h to obtain a viscous mixture;

[0012] The viscous mixture is dried, dehydrated and crushed to obtain the environmentally friendly slow-release fertilizer.

[0013] Furthermore, the preparation method of the mussel extract-polysaccharide-nitrogen fertilizer complex comprises the following steps:

[0014] The mussel extract is dissolved in dimethyl sulfoxide, mixed with oxidized polysaccharide and anhydrous sodium sulfate, heated to 30°C to 40°C and reacted for 10h to 14h to obtain a mixed solution; the mixed solution, nitrogen fertilizer, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole are mixed and reacted in a temperature environment of 15°C to 20°C for 18h to 24h to obtain the mussel extract-polysaccharide-nitrogen fertilizer complex.

[0015] Furthermore, the preparation method of the mussel extract comprises the following steps:

[0016] Cut off the byssus of the mussel and put it into 0.1 mol / L sodium hydroxide solution, stir it at 50r / min-100r / min for 2h-3h in 4℃-10℃ environment, then add hydrochloric acid to adjust the pH value to 9-10 to obtain protein precipitation solution;

[0017] The protein precipitation liquid is centrifuged at a speed of 10000 r / min to 15000 r / min for 3 to 5 minutes to obtain a precipitate, and the precipitate is dialyzed through a dialysis bag with a cut-off flow rate of 10 kDa to obtain the mussel extract.

[0018] Furthermore, the preparation method of the oxidatively modified polysaccharide comprises the following steps:

[0019] The water-soluble polysaccharide derivative is mixed and dissolved with water, and then acid is added to adjust the pH value to 3-4, and stirred for 30-60 minutes to obtain a mixed solution, and the mixed solution is vacuum dried to obtain a water-soluble polysaccharide;

[0020] The water-soluble polysaccharide is mixed with sodium periodate and stirred and reacted in the dark to obtain the oxidatively modified polysaccharide.

[0021] Furthermore, the water-soluble polysaccharide derivative includes sodium carboxymethyl cellulose or sodium hyaluronate.

[0022] Furthermore, the mass ratio of the water-soluble polysaccharide to sodium periodate is 1:1-2.

[0023] Furthermore, the conditions for the light-proof reaction include a reaction temperature of 20° C. to 25° C. and a reaction time of 2 h to 5 h.

[0024] Furthermore, the nitrogen fertilizer is urea.

[0025] Furthermore, the mass ratio of the mussel extract: oxidized polysaccharide: anhydrous sodium sulfate: nitrogen fertilizer: N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride: 1-hydroxybenzotriazole is 0.1: 5-10: 0.05-0.1: 20-30: 3-6: 3-6.

[0026] Furthermore, the inorganic fertilizer is potash fertilizer.

[0027] Furthermore, the calcium salt comprises a calcium chloride solution.

[0028] Furthermore, the mass concentration of the calcium salt is 5% to 10%.

[0029] The second object of the present invention is to provide an environmentally friendly slow-release fertilizer prepared by the method for preparing the environmentally friendly slow-release fertilizer.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] The invention uses a mussel extract with good adhesion effect as one of the carriers. The mussel extract contains a large amount of mussel mucin. The mussel mucin has a strong adhesion effect. The mussel mucin has active groups of amino and carboxyl groups. The carboxyl groups on the mussel mucin are activated by the activation of carboxyl activation reagents N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole, so that the mussel mucin is activated and condensed with the amino groups in the nitrogen fertilizer to form an amide structure through the activated carboxyl groups. Then, carboxymethyl cellulose or hyaluronic acid with biocompatibility is used. Hyaluronic acid has good water absorption and water retention capabilities. As the second carrier, the water-soluble polysaccharide derivatives are acidified to restore their carboxylic acid structure to obtain water-soluble polysaccharides. The water-soluble polysaccharides are oxidized to obtain functional group aldehyde groups to obtain oxidized modified polysaccharides. On the one hand, the oxidized modified polysaccharides condense with the amino groups in the nitrogen fertilizer through the action of the carboxyl activation reagent to form an amide bond connection. On the other hand, the oxidized modified polysaccharides condense with the amino groups of mussel mucin in the mussel extract through the aldehyde group to form a dynamic imine bond connection with high temperature resistance, thereby achieving high temperature protection for the mussel mucin and preventing the degradation of the mussel mucin during high temperature heating and drying. Through the synergistic cooperation of amide structure and imine structure, the encapsulation of nitrogen fertilizer and the protection of the carrier are achieved, and then the adhesion of mussel mucin is used to adhere and encapsulate the inorganic fertilizer. Finally, the calcium ion energy forms a metal coordination effect with carboxymethyl cellulose or hyaluronic acid to form gelation, which further realizes the encapsulation of inorganic fertilizer. Through the synergistic cooperation of amide bond, imine bond and calcium ion metal coordination, an environmentally friendly slow-release fertilizer is finally obtained. After being applied to the soil, it is slowly released with the help of micro-environment conditions such as microorganisms and enzymes contained in the soil. DETAILED DESCRIPTION

[0032] The technical solution of the present invention will be clearly and completely described below through 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 those skilled in the art without creative work are within the scope of protection of the present invention.

[0033] Unless otherwise specified, the raw materials and reagents used in the present invention are commercially available or can be prepared by known methods.

[0034] Preparation Example 1:

[0035] The preparation of mussel extract specifically includes the following processes:

[0036] The fresh purple mussel was washed with water, and then its byssus was cut with scissors and put into 200mL of 0.1mol / L sodium hydroxide solution, and then the stirring controller was turned on for stirring in a low temperature environment of 4°C, and the stirring speed was set to 50r / min. After stirring for 2h, hydrochloric acid was added dropwise while stirring until the pH value of the solution dropped to 9-10, and then it was allowed to stand for 10min to obtain a protein precipitate. The protein precipitate was placed in a centrifuge and centrifuged at a speed of 10000r / min for 3min to obtain a precipitate. The precipitate was mixed and stirred with Tris-hydrochloric acid buffer with a pH value of 7, and then placed in a dialysis bag with a cutoff flow of 10kDa, dialyzed with deionized water for 2 days, and then freeze-dried to obtain the mussel extract.

[0037] Preparation Example 2:

[0038] The preparation method of mussel extract specifically includes the following processes:

[0039] The fresh purple mussel was washed with water, and then its byssus was cut with scissors and put into 200mL of 0.1mol / L sodium hydroxide solution, and then the stirring controller was turned on for stirring in a low temperature environment of 6°C, and the stirring speed was set to 70r / min. After stirring for 2h, hydrochloric acid was added dropwise while stirring until the pH value of the solution dropped to 9-10, and then it was allowed to stand for 10min to obtain a protein precipitate, and the protein precipitate was placed in a centrifuge and centrifuged at a speed of 12000r / min for 4min to obtain a precipitate, and the precipitate was mixed and stirred with Tris-hydrochloric acid buffer with a pH value of 7, and then placed in a dialysis bag with a cutoff flow of 10kDa, dialyzed with deionized water for 2 days, and then freeze-dried to obtain the mussel extract.

[0040] Preparation Example 3:

[0041] The preparation method of mussel extract specifically includes the following processes:

[0042] The fresh purple mussel was washed with water, and then its byssus was cut with scissors and placed in 200 mL of 0.1 mol / L sodium hydroxide solution. Then, the stirring controller was turned on for stirring in a low temperature environment of 8°C, and the stirring speed was set to 90 r / min. After stirring for 3 hours, hydrochloric acid was added dropwise while stirring until the pH value of the solution dropped to 9-10, and then it was allowed to stand for 15 minutes to obtain a protein precipitate. The protein precipitate was placed in a centrifuge and centrifuged at a speed of 14000 r / min for 4 minutes to obtain a precipitate. The precipitate was mixed and stirred with Tris-hydrochloric acid buffer with a pH value of 7, and then placed in a dialysis bag with a cutoff flow of 10 kDa, dialyzed with deionized water for 2 days, and then freeze-dried to obtain the mussel extract.

[0043] Preparation Example 4:

[0044] The preparation method of mussel extract specifically includes the following processes:

[0045] The fresh purple mussel was washed with water, and then its byssus was cut with scissors and put into 200mL of 0.1mol / L sodium hydroxide solution, and then the stirring controller was turned on for stirring in a low temperature environment of 10°C, and the stirring speed was set to 100r / min. After stirring for 3h, hydrochloric acid was added dropwise while stirring until the pH value of the solution dropped to 9-10, and then it was allowed to stand for 15min to obtain a protein precipitate, and the protein precipitate was placed in a centrifuge and centrifuged at a speed of 15000r / min for 5min to obtain a precipitate, and the precipitate was mixed and stirred with Tris-hydrochloric acid buffer with a pH value of 7, and then placed in a dialysis bag with a cutoff flow of 10kDa, dialyzed with deionized water for 2 days, and then freeze-dried to obtain the mussel extract.

[0046] Preparation Example 5:

[0047] The preparation of oxidatively modified polysaccharides specifically includes the following processes:

[0048] Dissolve 100g of sodium carboxymethyl cellulose in 500mL of deionized water, then adjust the pH value of the dissolved sodium carboxymethyl cellulose solution to 3 with acetic acid, then stir for 30min and vacuum dry to obtain carboxymethyl cellulose. Mix 50g of carboxymethyl cellulose with 50g of sodium periodate and dissolve in 400ml of water, then place in a 20°C water bath, stir and react for 2h in the dark. After the reaction is completed, add 100ml of ethylene glycol to mix and quench the reaction for 2h to obtain a mixed solution, then place the mixed solution in a dialysis bag with a cutoff of 3.5kDa, dialyze with deionized water for 2 days, and then freeze-dry to obtain oxidatively modified carboxymethyl cellulose.

[0049] Preparation Example 6:

[0050] The preparation of oxidatively modified polysaccharides specifically includes the following processes:

[0051] Dissolve 100g of sodium carboxymethyl cellulose in 500mL of deionized water, then adjust the pH value of the dissolved sodium carboxymethyl cellulose solution to 3.5 with acetic acid, then stir for 40min and vacuum dry to obtain carboxymethyl cellulose. Mix 50g of carboxymethyl cellulose with 70g of sodium periodate and dissolve in 400ml of water, then place in a 20°C water bath, stir and react for 3h in the dark. After the reaction is completed, add 100ml of ethylene glycol to mix and quench the reaction for 3h to obtain a mixed solution, then place the mixed solution in a dialysis bag with a cutoff of 3.5kDa, dialyze with deionized water for 2 days, and then freeze-dry to obtain oxidatively modified carboxymethyl cellulose.

[0052] Preparation Example 7:

[0053] The preparation of oxidatively modified polysaccharides specifically includes the following processes:

[0054] Dissolve 100g of sodium hyaluronate in 600mL of deionized water, then adjust the pH value of the dissolved sodium hyaluronate to 4 with acetic acid, then stir for 50min and vacuum dry to obtain hyaluronic acid. Mix 50g of hyaluronic acid with 90g of sodium periodate and dissolve in 400ml of water, then place in a 25°C water bath, stir and react for 4h in the dark. After the reaction is completed, add 150ml of ethylene glycol to mix and quench the reaction for 4h to obtain a mixed solution, then place the mixed solution in a dialysis bag with a cutoff of 3.5kDa, dialyze with deionized water for 2 days, and then freeze-dry to obtain oxidatively modified hyaluronic acid.

[0055] Preparation Example 8:

[0056] The preparation of oxidatively modified polysaccharides specifically includes the following processes:

[0057] 100g of sodium hyaluronate was dissolved in 600mL of deionized water, and then the pH value of the dissolved sodium hyaluronate was adjusted to 4 with acetic acid, followed by stirring for 60min and vacuum drying to obtain hyaluronic acid, 50g of hyaluronic acid was mixed with 100g of sodium periodate and dissolved in 400ml of water, and then placed in a 25°C water bath environment, stirred and reacted for 5h in the dark. After the reaction was completed, 150ml of ethylene glycol was added to mix and quench the reaction for 5h to obtain a mixed solution, and then the mixed solution was placed in a dialysis bag with a cutoff of 3.5kDa, dialyzed with deionized water for 2 days, and then freeze-dried to obtain oxidatively modified hyaluronic acid.

[0058] Preparation Example 9:

[0059] The preparation of oxidatively modified polysaccharides specifically includes the following processes:

[0060] Directly mix 100g of sodium hyaluronate and 100g of sodium periodate and add 400ml of water to dissolve, then place in a water bath at 25°C and stir to react for 5h in the dark. After the reaction is completed, add 150ml of ethylene glycol to mix and quench the reaction for 5h to obtain a mixed solution, then place the mixed solution in a dialysis bag with a cutoff of 3.5kDa, dialyze with deionized water for 2 days, and then freeze-dry to obtain oxidatively modified sodium hyaluronate.

[0061] Preparation Example 10:

[0062] The preparation of the mussel extract-polysaccharide-nitrogen fertilizer complex specifically includes the following processes:

[0063] 1 g of the mussel extract obtained in Preparation Example 1 was weighed and dissolved in 300 mL of dimethyl sulfoxide, and then 50 g of the oxidized modified carboxymethyl cellulose obtained in Preparation Example 5 and 0.5 g of anhydrous sodium sulfate were added and mixed and stirred evenly, and then the temperature was raised to 30° C. for reaction for 10 h. After the reaction was completed, the obtained mixed solution was mixed with 200 g of urea, 3 g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 3 g of 1-hydroxybenzotriazole to form a reaction solution, and the reaction solution was placed in a low-temperature water bath at 15° C. for reaction for 18 h. After the reaction was completed, the solution was placed in a dialysis bag with a cutoff of 30 kDa for dialysis treatment to obtain a viscous mussel extract-polysaccharide-nitrogen fertilizer complex.

[0064] Preparation Example 11:

[0065] The preparation of the mussel extract-polysaccharide-nitrogen fertilizer complex specifically includes the following processes:

[0066] 1 g of the mussel extract obtained in Preparation Example 2 was weighed and dissolved in 300 mL of dimethyl sulfoxide, and then 70 g of the oxidized modified carboxymethyl cellulose obtained in Preparation Example 6 and 0.6 g of anhydrous sodium sulfate were added and mixed and stirred evenly, and then the temperature was raised to 30 ° C for reaction for 12 hours. After the reaction was completed, the obtained mixed solution was mixed with 230 g of urea, 4 g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 4 g of 1-hydroxybenzotriazole to form a reaction solution, and the reaction solution was placed in a low-temperature water bath at 15 ° C for 20 hours. After the reaction was completed, the solution was placed in a dialysis bag with a cut-off flow rate of 30 kDa for dialysis treatment to obtain a viscous mussel extract-polysaccharide-nitrogen fertilizer complex.

[0067] Preparation Example 12:

[0068] The preparation of the mussel extract-polysaccharide-nitrogen fertilizer complex specifically includes the following processes:

[0069] Weigh 1g of the mussel extract obtained in Preparation Example 3 and dissolve it in 400mL of dimethyl sulfoxide, then add 90g of the oxidatively modified hyaluronic acid obtained in Preparation Example 7, 0.8g of anhydrous sodium sulfate and mix and stir evenly, then warm to 35°C for 12h. After the reaction is completed, the obtained mixed solution is mixed with 270g of urea, 5g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 5g of 1-hydroxybenzotriazole to form a reaction solution, and the reaction solution is placed in a low-temperature water bath at 20°C for 22h. After the reaction is completed, the solution is placed in a dialysis bag with a cutoff of 30kDa and dialyzed to obtain a viscous mussel extract-polysaccharide-nitrogen fertilizer complex.

[0070] Preparation Example 13:

[0071] The preparation of the mussel extract-polysaccharide-nitrogen fertilizer complex specifically includes the following processes:

[0072] Weigh 1g of the mussel extract obtained in Preparation Example 4 and dissolve it in 400mL of dimethyl sulfoxide, then add 100g of the oxidatively modified hyaluronic acid obtained in Preparation Example 8, 1g of anhydrous sodium sulfate and mix and stir evenly, then heat to 40°C for reaction for 14h. After the reaction is completed, the obtained mixed solution is mixed with 300g of urea, 6g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 6g of 1-hydroxybenzotriazole to form a reaction solution, and the reaction solution is placed in a low-temperature water bath at 20°C for reaction for 24h. After the reaction is completed, the solution is placed in a dialysis bag with a cutoff of 30kDa and dialyzed to obtain a viscous mussel extract-polysaccharide-nitrogen fertilizer complex.

[0073] Preparation Example 14:

[0074] The preparation of the mussel extract-polysaccharide-nitrogen fertilizer complex specifically includes the following processes:

[0075] Weigh 1g of the mussel extract obtained in Preparation Example 4 and dissolve it in 400mL of dimethyl sulfoxide, then add 100g of the oxidatively modified hyaluronic acid obtained in Preparation Example 9, 1g of anhydrous sodium sulfate and mix and stir evenly, then heat to 40°C for reaction for 14h. After the reaction is completed, the obtained mixed solution is mixed with 300g of urea, 6g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 6g of 1-hydroxybenzotriazole to form a reaction solution, and the reaction solution is placed in a low-temperature water bath at 20°C for reaction for 24h. After the reaction is completed, the solution is placed in a dialysis bag with a cutoff of 30kDa and dialyzed to obtain a viscous mussel extract-polysaccharide-nitrogen fertilizer complex.

[0076] Preparation Example 15:

[0077] The preparation of the mussel extract-polysaccharide-nitrogen fertilizer complex specifically includes the following processes:

[0078] Weigh 1g of the mussel extract obtained in Preparation Example 4 and dissolve it in 400mL of dimethyl sulfoxide, then add 100g of sodium hyaluronate and 1g of anhydrous sodium sulfate and mix and stir evenly, then heat to 40°C and react for 14h. After the reaction is completed, the obtained mixed solution is mixed with 300g of urea, 6g of N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 6g of 1-hydroxybenzotriazole to form a reaction solution, and the reaction solution is placed in a low-temperature water bath at 20°C and reacted for 24h. After the reaction is completed, the solution is placed in a dialysis bag with a cutoff of 30kDa and dialyzed to obtain a viscous mussel extract-polysaccharide-nitrogen fertilizer complex.

[0079] Embodiment 1:

[0080] The preparation of an environmentally friendly slow-release fertilizer specifically includes the following processes:

[0081] Weigh 1 part by weight of the mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 10 and disperse it in 15 parts by weight of water, then heat it to 50° C., and then add 5 parts by weight of potash fertilizer and mix and stir to form a dispersed solution. At a temperature of 50° C., add a 5% calcium chloride solution according to 0.005 times the weight of the dispersed solution to the dispersed solution and stir evenly while hot. Then cool it to 20° C. and let it stand for 20 hours to obtain a viscous mixture. The viscous mixture is dried with a dryer, and then put into a crusher and crushed to obtain an environmentally friendly slow-release fertilizer.

[0082] Embodiment 2:

[0083] The preparation of an environmentally friendly slow-release fertilizer specifically includes the following processes:

[0084] 1.2 parts by weight of the mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 10 was weighed and dispersed in 17 parts by weight of water, then heated to 50° C., and then 5 parts by weight of potash fertilizer was added and mixed to form a dispersed solution. At a temperature of 50° C., a 6% calcium chloride solution was added to the dispersed solution according to 0.006 times the weight of the dispersed solution and stirred evenly while hot. Then the mixture was cooled to 20° C. and allowed to stand for 20 hours to obtain a viscous mixture, which was dried with a dryer and then crushed in a crusher to obtain an environmentally friendly slow-release fertilizer.

[0085] Embodiment 3:

[0086] The preparation of an environmentally friendly slow-release fertilizer specifically includes the following processes:

[0087] 1.4 parts by weight of the mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 11 was weighed and dispersed in 18 parts by weight of water, then heated to 55° C., and 6 parts by weight of potash fertilizer were added and mixed to form a dispersed solution. At a temperature of 55° C., a calcium chloride solution with a mass concentration of 7% was added to the dispersed solution according to 0.007 times the weight of the dispersed solution and stirred evenly while hot. Then the mixture was cooled to 20° C. and allowed to stand for 22 hours to obtain a viscous mixture, which was dried with a dryer and then crushed in a crusher to obtain an environmentally friendly slow-release fertilizer.

[0088] Embodiment 4:

[0089] The preparation of an environmentally friendly slow-release fertilizer specifically includes the following processes:

[0090] 1.6 parts by weight of the mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 12 was weighed and dispersed in 20 parts by weight of water, then heated to 55° C., and 6 parts by weight of potash fertilizer were added and mixed to form a dispersed solution. At a temperature of 55° C., a calcium chloride solution with a mass concentration of 8% was added to the dispersed solution according to 0.008 times the weight of the dispersed solution and stirred evenly while hot. Then the mixture was cooled to 25° C. and allowed to stand for 22 hours to obtain a viscous mixture, which was dried with a dryer and then crushed in a crusher to obtain an environmentally friendly slow-release fertilizer.

[0091] Embodiment 5:

[0092] The preparation of an environmentally friendly slow-release fertilizer specifically includes the following processes:

[0093] 1.8 parts by weight of the mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 13 was weighed and dispersed in 22 parts by weight of water, then heated to 60° C., and then 7 parts by weight of potash fertilizer was added and mixed to form a dispersed solution. At a temperature of 60° C., a 9% calcium chloride solution was added to the dispersed solution according to 0.009 times the weight of the dispersed solution and stirred evenly while hot. Then the mixture was cooled to 25° C. and allowed to stand for 24 hours to obtain a viscous mixture, which was dried with a dryer and then crushed in a crusher to obtain an environmentally friendly slow-release fertilizer.

[0094] Embodiment 6:

[0095] The preparation of an environmentally friendly slow-release fertilizer specifically includes the following processes:

[0096] Weigh 2 parts by weight of the mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 13 and disperse it in 23 parts by weight of water, then heat it to 60°C, and then add 7 parts by weight of potash fertilizer and mix and stir to form a dispersed solution. At a temperature of 60°C, add a 10% calcium chloride solution according to 0.01 times the weight of the dispersed solution to the dispersed solution and stir evenly while hot. Then cool it to 25°C and let it stand for 24 hours to obtain a viscous mixture, dry the viscous mixture with a dryer, and then put it into a crusher to crush it to obtain an environmentally friendly slow-release fertilizer.

[0097] Comparative Example 1:

[0098] The preparation of an environmentally friendly slow-release fertilizer specifically includes the following processes:

[0099] The mussel extract-polysaccharide-nitrogen fertilizer complex in Example 6 was replaced by the mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 14, and the other conditions remained the same as in Example 6.

[0100] Comparative Example 2:

[0101] The preparation of an environmentally friendly slow-release fertilizer specifically includes the following processes:

[0102] The mussel extract-polysaccharide-nitrogen fertilizer complex in Example 6 was replaced by the mussel extract-polysaccharide-nitrogen fertilizer complex obtained in Preparation Example 15, and the other conditions remained the same as in Example 6.

[0103] According to GB / T 23348-2009 Slow-release Fertilizer, the environmentally friendly slow-release fertilizers obtained in Examples 1 to 6 and Comparative Examples 1 to 2 were measured for the cumulative release rates of total nutrients (nitrogen and potassium) on the 7th, 14th and 28th days in a temperature environment of 30°C ± 5°C. The results are shown in Table 1 below.

[0104] Table 1

[0105] Sources Cumulative release rate on the 7th day Cumulative release rate on day 14 Cumulative release rate on day 28 Example 1 4.87 14.8 38.4 Example 2 4.84 14.7 38.1 Example 3 4.75 14.4 37.6 Example 4 4.62 13.9 37.1 Example 5 4.54 13.6 36.8 Example 6 4.31 13.2 36.3 Comparative Example 1 6.67 35.6 52.5 Comparative Example 2 8.04 42.7 61.3

[0106] According to the cumulative release rate in Table 1 above, it can be seen that:

[0107] (1) Examples 1 to 6 of the present invention use mussel extracts with good adhesion effects and carboxymethyl cellulose or hyaluronic acid with biocompatibility as carriers, and achieve slow release of fertilizers through the synergistic coordination of amide structure, imine structure and calcium ion metal coordination.

[0108] (2) Comparative Example 1 shows that, since the sodium ions in sodium hyaluronate are not removed by acidification, the carboxyl structure in the hyaluronic acid cannot form an amide bond, which may lead to insufficient cross-linking density. Relying on the coordination effect of calcium ions and the covalent cross-linking of imine bonds, the release rate is fast and the sustained-release effect is poor.

[0109] (3) Comparative Example 2 shows that, since sodium hyaluronate is not oxidized, it cannot form a high-temperature-resistant dynamic imine bond with the mussel mucin in the mussel extract. When dried at high temperature, the mussel mucin is easily denatured and inactivated, loses its adhesion, and has a fast release rate and a poor sustained-release effect.

[0110] The above-described embodiments provide a detailed description of the technical solutions and beneficial effects of the present invention. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected.

Claims

1. A method for preparing an environmentally friendly slow-release fertilizer, characterized in that: The preparation method comprises the following steps: The mussel extract-polysaccharide-nitrogen fertilizer complex, inorganic fertilizer and water are mixed and stirred in a weight ratio of 1-2:5-7:15-23, heated to 50°C-60°C to form a dispersed solution, the dispersed solution and calcium salt are mixed and stirred in a weight ratio of 1:0.005-0.01, cooled to 20°C-25°C, reacted for 20h-24h to obtain a viscous mixture; The viscous mixture is dried, dehydrated and crushed to obtain the environmentally friendly slow-release fertilizer.

2. The method for preparing an environmentally friendly slow-release fertilizer according to claim 1, characterized in that: The preparation method of the mussel extract-polysaccharide-nitrogen fertilizer complex comprises the following steps: The mussel extract is dissolved in dimethyl sulfoxide, mixed with oxidized polysaccharide and anhydrous sodium sulfate, heated to 30°C to 40°C and reacted for 10h to 14h to obtain a mixed solution; the mixed solution, nitrogen fertilizer, N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride and 1-hydroxybenzotriazole are mixed and reacted in a temperature environment of 15°C to 20°C for 18h to 24h to obtain the mussel extract-polysaccharide-nitrogen fertilizer complex.

3. The method for preparing an environmentally friendly slow-release fertilizer according to claim 2, characterized in that: The preparation method of the mussel extract comprises the following steps: Cut off the byssus of the mussel and put it into 0.1 mol / L sodium hydroxide solution, stir it at 50r / min-100r / min for 2h-3h in 4℃-10℃ environment, then add hydrochloric acid to adjust the pH value to 9-10 to obtain protein precipitation solution; The protein precipitation liquid is centrifuged at a speed of 10000 r / min to 15000 r / min for 3 to 5 minutes to obtain a precipitate, and the precipitate is dialyzed through a dialysis bag with a cut-off flow of 10 kDa to obtain the mussel extract.

4. The method for preparing an environmentally friendly slow-release fertilizer according to claim 2, characterized in that: The preparation method of the oxidatively modified polysaccharide comprises the following steps: The water-soluble polysaccharide derivative is mixed and dissolved with water, and then acid is added to adjust the pH value to 3-4, and stirred for 30-60 minutes to obtain a mixed solution, and the mixed solution is vacuum dried to obtain a water-soluble polysaccharide; The water-soluble polysaccharide is mixed with sodium periodate and stirred and reacted in the dark to obtain the oxidatively modified polysaccharide.

5. The method for preparing an environmentally friendly slow-release fertilizer according to claim 4, characterized in that: The water-soluble polysaccharide derivative includes sodium carboxymethylcellulose or sodium hyaluronate.

6. The method for preparing an environmentally friendly slow-release fertilizer according to claim 2, characterized in that: The nitrogen fertilizer is urea.

7. The method for preparing an environmentally friendly slow-release fertilizer according to claim 2, characterized in that: The mass ratio of the mussel extract: oxidized polysaccharide: anhydrous sodium sulfate: nitrogen fertilizer: N-(3-dimethylaminopropyl)-N'-ethylcarbodiimide hydrochloride: 1-hydroxybenzotriazole is 0.1: 5-10: 0.05-0.1: 20-30: 3-6: 3-6.

8. The method for preparing an environmentally friendly slow-release fertilizer according to claim 2, characterized in that: The inorganic fertilizer is potash fertilizer.

9. The method for preparing an environmentally friendly slow-release fertilizer according to claim 2, characterized in that: The calcium salt includes calcium sulfate or calcium chloride.

10. An environmentally friendly slow-release fertilizer prepared by the method for preparing an environmentally friendly slow-release fertilizer according to any one of claims 1 to 9.