Preparation method of chitosan selenium-supplementing water-retaining agent

Abstract

The invention relates to a preparation method of a chitosan selenium-supplementing water-retaining agent, intelligent response to temperature change is realized through a multi-component linkage effect, and nutrient release can be adjusted while good water retention performance is maintained. The product has a selenium slow-release function, and selenium nanoparticles are embedded in a polymer network and are slowly released through a diffusion effect. The multi-polymer barrier and the pH-responsive component ensure long-term stable release, and the utilization efficiency of selenium is improved. The product is composed of a natural polymer and a biodegradable synthetic polymer, and can be gradually decomposed into simple organic matters in soil. The selenium nanoparticles are absorbed by plants or combined with soil elements, and cannot be accumulated for a long time. And the biodegradable cross-linking agent ensures that the whole network structure is finally and completely decomposed, so that environmental friendliness and sustainability are realized. According to the composite system design, the overall performance and the application range of the water-retaining agent are remarkably improved, comprehensive support is provided for plant growth, and meanwhile harmful chemical residues are avoided.

Description

Technical Field

[0001] The invention relates to the field of agricultural technology, and in particular to a method for preparing a chitosan selenium-supplementing water-retaining agent. Background Art

[0002] As an important agricultural water-saving material, the principle and application of water retainer plays a key role in agricultural production. It can absorb and retain water, and then slowly release it when plants need it, thereby improving the water retention capacity of the soil and improving the growth environment of plants under drought conditions. This material is widely used in agriculture, horticulture, and flower planting, providing strong support for increasing crop yields and saving water resources.

[0003] However, the performance of water retainers may be affected in high temperature environments. Since high temperature causes faster evaporation, the water content in the water retainer may decrease rapidly, which directly affects its water retention effect under high temperature and drought conditions. It is worth noting that different types of water retainers perform differently in high temperature environments. Some synthetic polymer water retainers may lose some of their water retention capacity due to structural changes caused by high temperature; while some water retainers based on natural polymers, such as chitosan materials, may be able to resist the effects of high temperature to a certain extent and maintain their water retention properties.

[0004] Despite this, existing water retaining agent technologies generally have the problem of insufficient temperature responsiveness. In high or low temperature environments, many water retaining agents cannot effectively regulate their water retention and release, resulting in excessive evaporation of water at high temperatures and excessive water retention at low temperatures, which cannot meet the water needs of plants under different temperature conditions.

[0005] In addition, poor environmental compatibility is also a significant problem of existing water retaining agent technology. Some synthetic water retaining agents degrade slowly in the soil, which may cause long-term adverse effects on soil structure and ecological environment. The accumulation of these materials in the soil may lead to a decline in soil quality, affecting plant growth and sustainable use of soil.

[0006] At the same time, the application scope of existing water retainers is limited, which is mainly due to the differences in soil types, climatic conditions and crop types in different regions. Many water retainers are only suitable for specific types of soil or crops and lack wide applicability, which limits the promotion and application of water retainers in different regions. Summary of the invention

[0007] In order to solve or partially solve the problems existing in the related art, the present invention provides a method for preparing a chitosan selenium-supplementing water-retaining agent, which has good temperature responsiveness, can intelligently adjust the retention and release of water under different temperature conditions, and has better environmental compatibility, is easy to degrade in the soil, and reduces the impact on the environment. In addition, the new water-retaining agent should also have a wide range of applications, be able to adapt to the needs of different soil and crop types, thereby providing a more efficient, intelligent and environmentally friendly water management solution for agricultural production.

[0008] The first aspect of the present invention provides a method for preparing a chitosan selenium supplement water-retaining agent, comprising the following steps:

[0009] a. Dissolve 30 g chitosan in 1000 ml purified water containing 1% acetic acid and stir for 1-2 hours until completely dissolved;

[0010] b. Dissolve 20 g of poly (N-isopropylacrylamide-co-acrylic acid) in 200 ml of purified water and stir for 30 min until completely dissolved;

[0011] c. Disperse 5 g of nano-selenium in 15 ml of glycerol and treat with an ultrasonic processor for 10 min;

[0012] d. Mix the solutions of steps a, b and c and stir evenly;

[0013] e. Add 1g of cross-linking agent and stir for 1h to promote cross-linking;

[0014] f. Add 15 ml glycerol, 10 g polylactic acid, 5 g seaweed extract, 2 g vitamin E and 1 g citric acid, adjust the pH to 5.5-6.0, and stir well;

[0015] g. Use a high-speed homogenizer for homogenization;

[0016] h. Drying by spray dryer;

[0017] i. The spray-dried powder is cooled to room temperature and packaged.

[0018] Furthermore, the cross-linking agent is glutaraldehyde.

[0019] Furthermore, the inlet air temperature of the spray drying is 150°C, and the outlet air temperature is 80°C.

[0020] Furthermore, it is characterized in that the time of the high-speed homogenization treatment is 10 minutes.

[0021] Furthermore, the chitosan is characterized in that the deacetylation degree of the chitosan is greater than 85% and the chitosan is of medium molecular weight.

[0022] Furthermore, the invention is characterized in that the particle size of the nano-selenium is 20-50 nm.

[0023] The second aspect of the invention application provides a chitosan selenium supplement water-retaining agent, which is prepared by the above method.

[0024] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present invention.

[0025] Beneficial technical effects of the present invention:

[0026] The water retainer of the present invention achieves intelligent response to temperature changes through the linkage effect of multiple components. While maintaining good water retention performance, it can also adjust nutrient release according to environmental conditions to provide comprehensive support for plant growth. The design of this composite system not only solves the shortcomings of the water retainer in the control group in terms of temperature adaptability, but also significantly improves the overall performance and application range of the water retainer through the synergistic effect of each component.

[0027] This product has the function of slow-release selenium, based on the synergistic effect of polymer network and selenium nanoparticles. Selenium nanoparticles are embedded in the polymer network and slowly released by diffusion. The concentration gradient inside and outside the water retainer and the multi-polymer barrier structure ensure long-term slow release. The pH-responsive component can adjust the release rate according to the soil pH. The released selenium nanoparticles are highly bioavailable. By adjusting the initial loading and the degree of network cross-linking, the release rate can be controlled to meet the needs of different crops. This slow-release mechanism reduces the accumulation and loss of selenium, improves utilization efficiency, and reduces environmental risks.

[0028] This product is composed of natural polymers and biodegradable synthetic polymers, which can be gradually decomposed in the soil. Natural polymers are completely degraded by microorganisms into carbon dioxide and water; synthetic polymers are degraded into simple organic matter through hydrolysis and microbial action; temperature-sensitive components are finally degraded by oxidation and hydrolysis. Selenium nanoparticles are absorbed by plants or combined with soil elements and will not accumulate for a long time. The use of biodegradable cross-linking agents ensures that the entire network structure can be completely decomposed. This comprehensive biodegradation process ensures that the product does not leave harmful chemical residues, achieving environmental friendliness and sustainability. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a surface electron microscope image of the product obtained in Example 1 of the present invention after drying;

[0030] Figure 2 This is a surface electron microscope image of the product obtained in Example 1 of the present invention after absorbing water; DETAILED DESCRIPTION

[0031] The optional embodiments of the present invention will be described in more detail below with reference to the accompanying drawings. Although the optional embodiments of the present invention are shown in the accompanying drawings, it should be understood that the present invention can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to make the present invention more thorough and complete, and to fully convey the scope of the present invention to those skilled in the art.

[0032] The terms used in this application are only for the purpose of describing specific embodiments and are not intended to limit this application. The singular forms of "a", "said" and "the" used in this application and the appended claims are also intended to include plural forms unless the context clearly indicates other meanings. It should also be understood that the term "and / or" used herein refers to and includes any or all possible combinations of one or more associated listed items.

[0033] The preparation method of the chitosan selenium supplement water-retaining agent of the present invention is described in detail below in conjunction with the accompanying drawings, as follows:

[0034] The present invention provides a method for preparing a chitosan selenium-supplementing water-retaining agent, comprising the following steps:

[0035] a. Dissolve 30g chitosan in 1000ml purified water containing 1% acetic acid and stir for 1-2h until completely dissolved;

[0036] b. Dissolve 20 g of poly (N-isopropylacrylamide-co-acrylic acid) in 200 ml of purified water and stir for 30 min until completely dissolved;

[0037] c. Disperse 5 g of nano-selenium in 15 ml of glycerol and treat with an ultrasonic processor for 10 min;

[0038] d. Mix the solutions of steps a, b and c and stir evenly;

[0039] e. Add 1g of cross-linking agent and stir for 1h to promote cross-linking;

[0040] f. Add 15 ml of glycerol, 10 g of polylactic acid, 5 g of seaweed extract, 2 g of vitamin E and 1 g of citric acid, adjust the pH to 5.5-6.0, and stir well;

[0041] g. Use a high-speed homogenizer for homogenization;

[0042] h. Drying by spray dryer;

[0043] i. The spray-dried powder is cooled to room temperature and packaged.

[0044] 1. Synergistic effect of P(NIPAAm-co-AAc) and chitosan in the water-retaining agent of the present invention

[0045] P(NIPAAm-co-AAc) is a temperature-sensitive main polymer, while chitosan, as a natural polymer material, forms a semi-interpenetrating network structure with P(NIPAAm-co-AAc). The linkage effect of this structure is manifested in:

[0046] Under low temperature environment: the polymer chain of P(NIPAAm-co-AAc) is in an extended state, forming a highly hydrophilic network structure with chitosan to maximize the water absorption capacity.

[0047] Under high temperature environment: When the polymer chain of P(NIPAAm-co-AAc) begins to shrink, the presence of chitosan can partially offset this shrinkage effect and maintain a certain network structure and water retention capacity. The water absorption and expansion characteristics of chitosan can compensate for the shrinkage of P(NIPAAm-co-AAc), thereby maintaining a good water retention effect under high temperature conditions.

[0048] 2. Synergistic effect of natural moisturizer (glycerin)

[0049] There is a linkage effect between natural moisturizers and the network structure formed by P(NIPAAm-co-AAc) and chitosan:

[0050] Across the entire temperature range: Natural humectants enhance the overall moisturizing properties of the water retainer.

[0051] Under high temperature environment: When P(NIPAAm-co-AAc) starts to release water, the natural moisturizer can slow down the evaporation rate of water, and work synergistically with P(NIPAAm-co-AAc) and chitosan to maintain the overall water retention effect of the water retaining agent.

[0052] 3. Temperature-responsive release of selenium nanoparticles

[0053] Selenium nanoparticles are encapsulated in a polymer network, and their release is closely related to the temperature responsiveness of P(NIPAAm-co-AAc):

[0054] Under low temperature environment: the network structure of P(NIPAAm-co-AAc) is relatively tight, the selenium nanoparticles are firmly wrapped, and the release rate is slow.

[0055] Under high temperature conditions: As the P(NIPAAm-co-AAc) polymer chain shrinks, the network structure becomes looser and the release rate of selenium nanoparticles increases. This temperature-responsive release mechanism can provide more selenium when plants need it (such as under high temperature stress conditions), enhancing the plant's ability to resist stress.

[0056] 4. Regulatory role of biodegradable polymers

[0057] Biodegradable polymers play an important regulatory role in the entire system:

[0058] In low temperature environment: biodegradable polymers and other components together constitute the overall structure of the water retaining agent, enhancing its mechanical strength and stability.

[0059] Under high temperature environment: the degradation rate of biodegradable polymers is accelerated, providing more space for the phase change of P(NIPAAm-co-AAc), optimizing water retention and release performance. At the same time, this degradation process also helps the water retaining agent to gradually decompose in the soil and improve environmental compatibility.

[0060] 5. Overall linkage effect

[0061] The synergistic effect of these components enables the water retaining agent to maintain good performance under different temperature conditions:

[0062] In low temperature environments, the components work synergistically to maximize water absorption and retention capabilities.

[0063] During the temperature increase, the temperature-responsive changes of P(NIPAAm-co-AAc) triggered the dynamic regulation of the entire system, and other components such as chitosan and natural moisturizers played a buffering and compensating role.

[0064] Under high temperature conditions, although P(NIPAAm-co-AAc) begins to release water, the presence of other components ensures that the water retaining agent can still maintain the necessary water retention capacity, while the accelerated release of selenium nanoparticles provides additional nutritional support for plants.

[0065] Through the linkage effect of the above-mentioned multiple components, the water retainer achieves an intelligent response to temperature changes. While maintaining good water retention performance, it can also adjust nutrient release according to environmental conditions to provide comprehensive support for plant growth. The design of this composite system not only solves the shortcomings of the control group water retainer in temperature adaptability, but also significantly improves the overall performance and application range of the water retainer through the synergistic effect of each component.

[0066] In addition, this product also has the function of slow-release selenium, which is mainly based on the synergistic effect of the polymer network structure and selenium nanoparticles. During the preparation process, selenium nanoparticles are evenly dispersed and embedded in the polymer network, forming a physical barrier to limit direct release. The release of selenium nanoparticles is mainly controlled by diffusion, and slowly diffuses through the pore structure of the polymer network to achieve sustained release. As the release process proceeds, the concentration gradient formed inside and outside the water retainer becomes the driving force for sustained release. The multiple polymer barrier structure in the water retainer further regulates the release process to ensure long-term slow release. Over time, erosion and degradation of the surface of the water retainer also become auxiliary release mechanisms. The pH responsiveness of certain components can adjust the network structure according to soil pH changes and affect the release rate. The released selenium nanoparticles have high bioavailability due to their small size and large surface area. By adjusting parameters such as the initial loading amount and the degree of cross-linking of the polymer network, the release rate can be controlled to meet the needs of different crops. This slow-release mechanism reduces the accumulation and loss of selenium in the soil, reduces environmental impact, and improves utilization efficiency. In summary, this product achieves the intelligent release of selenium through a sustained-release system controlled by multiple mechanisms, providing plants with a continuous and stable supply of selenium nutrition, which not only improves the utilization efficiency of selenium but also reduces environmental risks.

[0067] Finally, the main body of the water retaining agent of the present invention is composed of natural polymer materials and biodegradable synthetic polymers, which can be gradually decomposed in the soil environment through physical, chemical and biological effects. Natural polymers such as chitosan and starch can be completely degraded into carbon dioxide and water under the action of soil microorganisms. Synthetic polymer parts, such as polyacrylamide, are broken into small molecular fragments by hydrolysis and then further decomposed by microorganisms. The temperature-sensitive component P (NIPAAm-co-AAc) will undergo oxidation and hydrolysis when exposed to the soil environment for a long time, and will eventually be degraded into simple organic matter. These degradation products are either absorbed and utilized by plants or further converted into soil organic matter by microorganisms. Selenium nanoparticles are gradually absorbed by plants or combined with other elements in the soil during the release process, and will not accumulate in the soil for a long time. The cross-linking agent used in the product is selected as a biodegradable type, ensuring that the entire network structure can be completely decomposed in the end. Through this comprehensive biodegradation process, the product will not leave harmful chemical residues in the soil after use, achieving environmental friendliness and sustainability.

[0068] In one embodiment of the present invention, the cross-linking agent is glutaraldehyde.

[0069] In one embodiment of the present invention, the inlet air temperature of the spray drying is 150°C and the outlet air temperature is 80°C.

[0070] In one embodiment of the present invention, the high-speed homogenization treatment lasts for 10 minutes.

[0071] In one embodiment of the present invention, the chitosan is characterized in that the deacetylation degree of the chitosan is greater than 85% and the chitosan is of medium molecular weight.

[0072] In one embodiment of the present invention, the nano-selenium has a particle size of 20-50 nm.

[0073] In one embodiment of the present invention, a chitosan selenium-supplementing water-retaining agent is provided, and the water-retaining agent is prepared by the above method.

[0074] For the purpose of greater clarity, the invention is described in detail through the following examples.

[0075] Example 1

[0076] 1. Dissolve 30 g chitosan (deacetylation degree greater than 85%, medium molecular weight) in 1000 ml purified water containing 1% acetic acid and stir for 1.5 h until completely dissolved.

[0077] 2. Dissolve 20 g of poly (N-isopropylacrylamide-co-acrylic acid) in 200 ml of purified water and stir for 30 min until completely dissolved.

[0078] 3. Disperse 5 g of nano-selenium (particle size 30 nm) in 15 ml of glycerol and treat with an ultrasonic processor for 10 min.

[0079] 4. Mix the solutions of steps 1, 2 and 3 and stir well.

[0080] 5. Add 1 g of glutaraldehyde as a cross-linking agent and stir for 1 hour to promote cross-linking.

[0081] 6. Add 15 ml of glycerol, 10 g of polylactic acid, 5 g of seaweed extract, 2 g of vitamin E and 1 g of citric acid, adjust the pH to 5.8 and stir well.

[0082] 7. Use a high-speed homogenizer for homogenization for 10 minutes.

[0083] 8. Drying is carried out by spray dryer with air inlet temperature of 150°C and air outlet temperature of 80°C.

[0084] 9. Cool the spray-dried powder to room temperature and package it.

[0085] Test Example 1 Water Retention Performance Test

[0086] 1. Purpose: To verify the water-retaining capacity of the water-retaining agent of the present invention under different temperature conditions.

[0087] 2. Materials:

[0088] Temperature responsive water retaining agent of the present invention (experimental group)

[0089] Potassium polyacrylate water retaining agent purchased from commercial sources (control group)

[0090] Analytical balance (precision 0.001g)

[0091] Constant temperature and humidity chamber

[0092] Glass Petri Dish

[0093] 3. Experimental steps:

[0094] S1 Preparation:

[0095] a) Soak the two water retaining agent samples in deionized water for 24 hours to allow them to fully absorb water.

[0096] b) Use filter paper to gently absorb excess water from the sample surface, weigh and record the initial mass (W0).

[0097] S2 sets the temperature conditions:

[0098] The constant temperature and humidity chambers were set to 15°C, 25°C, 35°C, and 45°C, respectively, and the relative humidity was uniformly set to 60%.

[0099] S3 water retention performance test:

[0100] a) Place fully hydrated samples (3 replicates of each) into pre-weighed glass petri dishes.

[0101] b) Place the sample in a constant temperature and humidity chamber at a set temperature.

[0102] c) Take out samples at 24h, 48h, 72h and 96h, weigh them quickly and record them (Wt).

[0103] d) After weighing, immediately place the sample back into the constant temperature and humidity chamber.

[0104] Data processing:

[0105] Calculate water retention rate = (Wt-dry weight) / (W0-dry weight) × 100%

[0106] Note: The dry weight is obtained by drying the sample at 105°C for 24 hours after the experiment.

[0107] Experimental results:

[0108] Water retention performance test results (water retention rate %)

[0109]

[0110] From the table we can observe that:

[0111] 1. Under all temperature conditions, the water retaining agent of the present invention always maintains a higher water retention rate than the water retaining agent of the control group.

[0112] 2. As the temperature rises, the water retention rates of the two water retaining agents show a downward trend, but the water retaining agent of the present invention decreases to a smaller extent.

[0113] 3. The effect of temperature on water retention performance is most significant at 45°C, at which time the performance difference between the water retaining agent of the present invention and the water retaining agent of the control group is the largest.

[0114] 4. In the long-term (96 hours) water retention test, the water retention agent of the present invention exhibits better durability, especially under high temperature conditions.

[0115] 5. In low temperature environments of 15°C and 25°C, the performance difference between the two water retaining agents is relatively small, but the water retaining agent of the present invention still performs better.

[0116] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or improvements to the technology in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a chitosan selenium supplement water-retaining agent, characterized in that: The following steps are involved: a. Dissolve 30g chitosan in 1000ml purified water containing 1% acetic acid and stir for 1-2h until completely dissolved; b. Dissolve 20 g of poly (N-isopropylacrylamide-co-acrylic acid) in 200 ml of purified water and stir for 30 min until completely dissolved; c. Disperse 5 g of nano-selenium in 15 ml of glycerol and treat with an ultrasonic processor for 10 min; d. Mix the solutions of steps a, b and c and stir evenly; e. Add 1g of cross-linking agent and stir for 1h to promote cross-linking; f. Add 15 ml of glycerol, 10 g of polylactic acid, 5 g of seaweed extract, 2 g of vitamin E and 1 g of citric acid, adjust the pH to 5.5-6.0, and stir well; g. Use a high-speed homogenizer for homogenization; h. Drying by spray dryer; i. The spray-dried powder is cooled to room temperature and packaged.

2. The preparation method according to claim 1, further characterized in that: The cross-linking agent is glutaraldehyde.

3. The preparation method according to claim 1, further characterized in that: The inlet air temperature of the spray drying is 150°C, and the outlet air temperature is 80°C.

4. The preparation method according to claim 1, further characterized in that: The high-speed homogenization treatment lasts for 10 minutes.

5. The preparation method according to claim 1, further characterized in that: The deacetylation degree of the chitosan is greater than 85%, and the chitosan is of medium molecular weight.

6. The preparation method according to claim 1, further characterized in that: The particle size of the nano-selenium is 20-50nm.

7. A chitosan selenium supplement water-retaining agent, characterized in that: Prepared according to the preparation method according to any one of claims 1 to 6.

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