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CN-122010640-A - Antibacterial hydrogel for controlled release fertilizer and preparation method thereof

CN122010640ACN 122010640 ACN122010640 ACN 122010640ACN-122010640-A

Abstract

The invention discloses an antibacterial hydrogel for a controlled-release fertilizer and a preparation method thereof, belonging to the technical field of controlled-release fertilizers. The preparation method comprises the steps of taking soluble corn starch, cellulose nanocrystalline, chitosan and chitin nanofibrils as main matrix materials, constructing a core-shell silver-zinc oxide nano antibacterial agent in situ, compounding the core-shell silver-zinc oxide nano antibacterial agent with functionalized graphene oxide and acrylamide monomers, wrapping nitrogen-phosphorus-potassium fertilizer and urea formaldehyde prepolymer in starch-based mother liquor, blending the starch-based mother liquor with chitosan solution, carrying out in-situ covalent-ion compound cross-linking polymerization through an ammonium persulfate/tetramethyl ethylenediamine initiating system to form three-dimensional network hydrogel, and carrying out extrusion/spray granulation, freeze-drying and hot air combined drying to obtain dry-base particles. The hydrogel provided by the invention has the advantages of high mechanical strength, excellent slow release performance, long-acting broad-spectrum antibacterial property and environmental responsiveness, obviously improves the fertilizer utilization rate and inhibits soil pathogenic bacteria, and is suitable for modern sustainable agriculture.

Inventors

  • ZHANG XUEJIE
  • SHEN LIN
  • DU TINGTING
  • ZHAO XIAOXIAO

Assignees

  • 菏泽开发区曹州农用化学有限公司

Dates

Publication Date
20260512
Application Date
20260203

Claims (8)

  1. 1. The preparation method of the antibacterial hydrogel for the controlled release fertilizer is characterized by comprising the following steps of (1) weighing 25-45 parts of soluble corn starch and 3-12 parts of cellulose nanocrystalline, adding 250-450 parts of deionized water, mechanically stirring, and cooling to obtain starch-nanocrystalline mother solution A; (2) weighing 8-18 parts of chitosan and 1-5 parts of chitin nanofibrils, adding 250-350 parts of glacial acetic acid aqueous solution with the volume fraction of 1.5-2.5%, and magnetically stirring at room temperature for 6-10 hours until the chitosan solution is completely dissolved and transparent to obtain a chitosan-nanofibril solution B; preparing core-shell silver-zinc oxide nano particles by an in-situ reduction method, namely dissolving 0.2-0.8 part of silver nitrate and 0.2-0.8 part of polyvinylpyrrolidone in 80-150 parts of deionized water, dropwise adding an ascorbic acid solution under ice bath, stirring for 40-70 min to form silver cores, adding 1-4 parts of zinc oxide precursor zinc nitrate hexahydrate and 1:1 hexamethyltetramine in mass ratio at 80-90 ℃ for 2-4 h to form a core-shell structure, B) ultrasonically dispersing the core-shell nano particles and 0.2-1.0 part of graphene oxide in 150-250 parts of deionized water containing 8-20 parts of acrylamide and 0.2-0.8 part of N, N-methylenebisacrylamide to obtain a functional nano antibacterial monomer dispersion liquid C, adding 30-70 parts of urea, 8-25 parts of ammonium dihydrogen phosphate and 8-25 parts of potassium sulfate into a starch-nano crystal mother solution A, adding 5-15 parts of urea aldehyde prepolymer after dissolution, slowly releasing the functional nano antibacterial monomer dispersion liquid C is added into 15-40 parts of functional nano antibacterial monomer dispersion liquid C, mixing chitosan-nanofibril solution B and the fertilizer-containing nano functional precursor solution D according to the mass ratio of (1.2-2.5) (4-7) under the protection of nitrogen, heating to 55-65 ℃, adding 0.2-0.7 part of ammonium persulfate and 0.1-0.3 part of N, N, N ', N' -tetramethyl ethylenediamine, and carrying out constant-temperature crosslinking reaction for 2-4 hours to form covalent-ion composite crosslinked three-dimensional network hydrogel E, (6) extruding or dripping the covalent-ion composite crosslinked three-dimensional network hydrogel E into particles with the particle size of 1.0-4.0 mm, pre-freezing for 4-8 hours at the temperature of-45-25 ℃, freeze-drying for 16-28 hours at the vacuum degree of less than or equal to 30Pa, and then carrying out hot air drying for 6-14 hours at the temperature of 40-50 ℃ until the water content is less than or equal to 12%, thereby obtaining the antibacterial hydrogel particles for the controlled release fertilizer.
  2. 2. The method for preparing the antibacterial hydrogel for the controlled release fertilizer, which is characterized in that in the step (1), 4-15 parts of carboxymethyl chitosan and 10 parts of corn starch are further added.
  3. 3. The method for preparing the antibacterial hydrogel for the controlled release fertilizer, which is characterized in that the parameters of mechanical stirring in the step (1) are as follows, the mechanical stirring is carried out at 85-95 ℃ for 40-70 min until the antibacterial hydrogel is completely gelatinized and transparent, and the temperature after cooling in the step (1) is 45-55 ℃.
  4. 4. The preparation method of the antibacterial hydrogel for the controlled release fertilizer, which is disclosed in claim 1, is characterized in that 0.3-1.5 parts of titanium dioxide nano particles are further added after the core-shell structure is formed in the step (a) of the step (3), and the mass ratio of silver nitrate to ascorbic acid solution in the step (a) of the step (3) is 1 (0.8-1.2).
  5. 5. The method for preparing the antibacterial hydrogel for the controlled release fertilizer, which is characterized in that graphene oxide in the step (b) of the step (3) is subjected to surface modification by using a KH-550 silane coupling agent in advance, and the using amount of the modifier is 3-8% of the mass of the graphene oxide.
  6. 6. The preparation method of the antibacterial hydrogel for the controlled release fertilizer is characterized in that 3-12 parts of potassium fulvate and 1 (5-10) of urea are further added in the step (4), the urea formaldehyde slow release prepolymer in the step (4) is prepared by the following steps of preparing urea and 37% formaldehyde solution in a molar ratio of 1.2:1, performing pH 8.0-8.5 and 60 ℃ prepolymerization for 3 hours, and stirring the urea formaldehyde slow release prepolymer in the step (4) for 40-80 minutes at the following stirring parameters of 45-55 ℃.
  7. 7. The method for preparing the antibacterial hydrogel for the controlled release fertilizer according to claim 1, wherein 2-10 parts of N-isopropyl acrylamide is added simultaneously in the step (5) through a constant temperature crosslinking reaction, and the mass ratio of the N-isopropyl acrylamide to the acrylamide is (1-4): 10, so that a temperature-responsive shrinkage-expansion network is formed.
  8. 8. An antibacterial hydrogel for a controlled release fertilizer, which is characterized by being obtained by the preparation method of any one of claims 1 to 7.

Description

Antibacterial hydrogel for controlled release fertilizer and preparation method thereof Technical Field The invention belongs to the technical field of controlled release fertilizers, and particularly relates to an antibacterial hydrogel for a controlled release fertilizer and a preparation method thereof. Background With the continuous growth of global population and the increasingly tense cultivated land resources, chemical fertilizers play a vital role in guaranteeing grain safety and agricultural sustainable development. However, the traditional fertilizer application has the problems of low utilization rate, unsynchronized nutrient release and crop demands, and the like, so that a great amount of nutrients are lost in the modes of volatilization, leaching, runoff, and the like. According to statistics, the nitrogen fertilizer utilization rate in China is only 30% -50%, the phosphate fertilizer is 20% -30%, and the potash fertilizer is 40% -60%. The low utilization rate not only causes resource waste and agricultural production cost increase, but also causes serious environmental problems such as water eutrophication, soil acidification hardening, greenhouse gas emission, nitrate pollution of underground water and the like. Especially under the condition that the fertilizer application amount in China is the first place in the world, the problems become bottlenecks for restricting the green development of agriculture and the construction of ecological civilization. Therefore, developing a novel fertilizer technology with high efficiency and environmental protection has become an industry consensus. In order to solve the defects of the traditional fertilizer, the slow and controlled release fertilizer technology is developed. The slow-release fertilizer is a fertilizer type which can be used for improving the utilization rate of the fertilizer and reducing the fertilization times and the environmental pollution by regulating and controlling the nutrient release rate through a physical, chemical or biological method so as to be matched with the growth requirements of crops. This technology was proposed in the united states in the earliest 60 s of the 20 th century and rapidly developed into an important direction of the modern fertilizer industry. Early controlled release fertilizers were primarily sulfur or polymer coated technologies such as Sulfur Coated Urea (SCU) and Polymer Coated Fertilizers (PCF) developed by TVA in the united states. The products realize the diffusion and controlled release of nutrients by forming a compact coating on the surface of fertilizer particles, and remarkably prolong the fertilizer efficiency period. However, the coated controlled release fertilizer has obvious defects that firstly, the production cost is high, coating materials (such as polyolefin and resin) depend on petrochemical industry, the cost is high, the coated controlled release fertilizer is not easy to degrade, secondly, the release mechanism is single, the coated controlled release fertilizer is mainly dependent on moisture permeation and coating breakage, and is easy to be influenced by environmental factors such as soil temperature, humidity and pH, so that initial burst or later nutrient deficiency is caused, thirdly, part of the coated materials use organic solvents, the environment is polluted in the production process, and residual coatings accumulate in soil to influence the microbial activity of the soil. In addition, the existing coated fertilizer has limited mechanical strength, is easy to damage in the transportation, storage and application processes, and influences the controlled release effect. With the increasingly strict environmental protection requirements, matrix type slow-release and controlled-release fertilizers gradually become research hotspots. The fertilizer of the type has the advantages of simple production process and lower cost, and nutrients are contained in the polymer matrix and released through matrix swelling, diffusion and degradation. Among them, hydrogel-based controlled release fertilizers have been attracting attention due to their high water absorption, water retention and biocompatibility. The hydrogel is a high polymer material with a three-dimensional network structure, can absorb water with hundreds of times of the self weight, slowly releases nutrients in soil, and improves the soil aggregation structure and the water retention capacity. Natural polysaccharide hydrogels, such as starch-based, chitosan-based, and cellulose-based hydrogels, are becoming an important point of research due to their wide sources and biodegradability. For example, starch is used as a cheap and renewable natural polymer, and can form a porous network after gelatinization and crosslinking, and is used for loading nutrients such as urea, phosphate and the like, so as to realize a slow release effect. The chitosan has cationic property, can form ionic bonding with anionic nutrients, and