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CN-121975529-A - Melatonin-chitosan-attapulgite composite gel beads and preparation method thereof

CN121975529ACN 121975529 ACN121975529 ACN 121975529ACN-121975529-A

Abstract

The invention discloses a melatonin-chitosan-attapulgite composite gel bead and a preparation method thereof, wherein the preparation method comprises the following steps of S1, treating attapulgite by organic acid to obtain activated attapulgite; S2, dispersing activated attapulgite in chitosan acid sol, S3, adding melatonin into the dispersed sol, mixing in a dark place to obtain colloid, S4, dripping the colloid into a cross-linking agent, and standing to form gel beads. The melatonin-chitosan-attapulgite composite gel bead is constructed, has excellent water retention performance, and the chitosan and the attapulgite cooperatively promote water absorption and retention capacity, reduce soil moisture loss, have remarkable water saving effect and are suitable for agricultural production in water-deficient areas. The water retention-regulation-slow release synergy is realized, the composite carrier can slow release melatonin and prolong the action period of the melatonin, regulate and control the physiology of crops, enhance stress resistance and realize the double effects of water guarantee and stress resistance regulation.

Inventors

  • YUAN JUN
  • XIA YAN
  • JIANG RUOTONG
  • Liu Suman
  • LI LING
  • YUAN HANBING
  • TAO MINGTAO
  • XU ZHIMENG

Assignees

  • 淮阴工学院

Dates

Publication Date
20260505
Application Date
20260127

Claims (10)

  1. 1. The preparation method of the melatonin-chitosan-attapulgite composite gel beads is characterized by comprising the following steps of: s1, treating attapulgite with organic acid to obtain activated attapulgite; s2, dispersing activated attapulgite in chitosan acid sol; s3, adding melatonin into the dispersed sol, and mixing in a dark place to obtain a colloid; S4, dripping the colloid into the cross-linking agent, and standing to form gel beads.
  2. 2. The preparation method of claim 1, wherein the mass ratio of chitosan, activated attapulgite and melatonin is 100 (10-15): 0.3-0.5.
  3. 3. The preparation method of claim 1, wherein in step S1, the organic acid is one or more of citric acid, oxalic acid and malic acid, and the concentration is 0.5-1 mol/L.
  4. 4. The preparation method of the activated attapulgite according to claim 1, wherein in the step S1, the activated attapulgite is prepared by stirring the attapulgite in an organic acid at 60-70 ℃ for 1-3 hours, washing the attapulgite with water until the pH is approximately equal to 6, drying and sieving the attapulgite.
  5. 5. The preparation method according to claim 1, wherein in step S2, the concentration of chitosan in the chitosan acid sol is 1% -3% (w/v).
  6. 6. The preparation method of the chitosan acid sol according to claim 1, wherein in the step S2, the chitosan is stirred in acid for 2-3 hours under the condition of a constant-temperature water bath at 60-70 ℃.
  7. 7. The preparation method of claim 1, wherein in the step S2, the chitosan has a deacetylation degree of 80% -90% and a molecular weight of 100-300 kDa.
  8. 8. The preparation method according to claim 1, wherein in the step S3, the melatonin is more than or equal to 98%, the melatonin is added into the colloid drop by drop, the temperature is 40-60 ℃ when being stirred in dark, the stirring time is 1-2 h, and the rotating speed is 300-400 rpm.
  9. 9. The preparation method of claim 1, wherein in step S4, the cross-linking agent is sodium citrate, sodium tripolyphosphate or sodium alginate, and the concentration is 0.02-0.1 mol/L.
  10. 10. The melatonin-chitosan-attapulgite composite gel beads prepared by the method of any one of claims 1 to 9.

Description

Melatonin-chitosan-attapulgite composite gel beads and preparation method thereof Technical Field The invention relates to an agricultural water-saving stress-resistant material, in particular to a melatonin-chitosan-attapulgite composite gel bead and a preparation method thereof. Background In the traditional agricultural drought-resistant measures, the water consumption of frequent irrigation is large, the water resource utilization rate is less than 40%, and the chemical water-retaining agent (such as polyacrylamide) can retain water for a short period, but is mostly a non-degradable polymer material, so that soil hardening, air permeability reduction and soil ecology damage are easily caused after long-term use. Melatonin (MT) is a plant growth regulator, and can enhance stress resistance of plants by regulating crop stomata opening and closing and activating an antioxidant enzyme system. However, MT is directly applied and is easy to be photolyzed and oxidized, and the release rate cannot be matched with the drought response period of 15-20 d of crops, so that the duration of drought resistance effect is short. Therefore, researchers develop the composite hydrogel with the slow release function to delay the release of MT so as to prolong the drought resistance time. However, the existing composite hydrogel preparation process has obvious defects that firstly, toxic cross-linking agents such as formaldehyde, glutaraldehyde and the like are mostly adopted, the crop growth can be inhibited due to exceeding of residual quantity, secondly, high-temperature (> 60 ℃) reaction conditions are needed, melatonin activity (MT thermal decomposition temperature is about 50 ℃) is easy to damage, and thirdly, the function is single, and only water retention or drug release can be realized. There is an urgent need in the industry to develop an agricultural drought-resistant material which is green to prepare, has synergistic performance and is environment-friendly so as to solve the multiple problems of water resource shortage, soil pollution and crop yield reduction in arid areas. Disclosure of Invention Aiming at the problems, the invention provides a melatonin-chitosan-attapulgite composite gel bead and a preparation method thereof, and the composite gel bead can activate the drought resistance activity of plants while maintaining moisture. In order to achieve the above purpose, the present invention provides a preparation method of melatonin-chitosan-attapulgite composite gel beads, which comprises the following steps: s1, treating attapulgite with organic acid to obtain activated attapulgite; s2, dispersing activated attapulgite in chitosan acid sol; s3, adding melatonin into the dispersed sol, and mixing in a dark place to obtain a colloid; S4, dripping the colloid into the cross-linking agent, and standing to form gel beads. The Chitosan (CS) is used as natural degradable polysaccharide, has excellent water absorption and retention property, but has poor mechanical strength and short water retention time effect, the Attapulgite (ATP) is a natural clay mineral, the water retention property of the material can be enhanced by high specific surface area (more than or equal to 300m 2/g) and cation exchange capacity, and the activated attapulgite (gATP) has high dispersion stability and good compatibility with chitosan base materials, and the synergistic effect of the two can further optimize the comprehensive performance of the composite material. In S1, modifying natural attapulgite by adopting organic acid, breaking siloxane bond and aluminum oxide bond in the attapulgite crystal lattice by the organic acid through protonation, replacing impurity ions in the crystal lattice, and simultaneously, carrying out esterification reaction on carboxyl and hydroxyl on the surface of the attapulgite to successfully introduce hydrophilic functional groups so as to optimize the surface activity. After the activation treatment, the original attapulgite aggregate is effectively dispersed to form a rich mesoporous-macroporous structure, the specific surface area is improved by 30% -50% compared with the original soil, the surface hydroxyl density and the number of active sites are obviously increased, the Zeta potential is changed from weak negative electricity to weak positive electricity, the hydrophobicity is greatly reduced, and conditions are created for subsequent interaction with chitosan. The gATP still keeps a one-dimensional rod-shaped structure, can be used as a physical support framework of a subsequent gel network, has optimized surface properties and pore structures, can obviously improve the interface compatibility with chitosan acidic sol, and lays a structural foundation for chitosan adsorption and melatonin loading. In S2, chitosan generates amino protonation reaction in an acid environment to generate-NH 3+, molecular chains are disentangled to form stable sol, gATP forms firm combination with chitosan molecular