Preparation method of chitosan selenium supplementing water retaining agent

Abstract

The application relates to a preparation method of a chitosan selenium supplementing water-retaining agent. The application realizes intelligent response to temperature change through multi-component linkage effect, can regulate nutrient release while maintaining good water-retaining performance, has a slow-release selenium function, and can ensure long-term stable release through a multiple polymer barrier and a pH-responsive component, thereby improving the utilization efficiency of selenium. The product is composed of natural polymers and biodegradable synthetic polymers, can be gradually decomposed into simple organic matters in soil, and can be absorbed by plants or combined with soil elements, so that the product cannot be accumulated for a long time. The biodegradable crosslinking agent ensures that the whole network structure is finally completely decomposed, realizes environmental friendliness and sustainability, significantly improves the overall performance and application range of the water-retaining agent, provides comprehensive support for plant growth, and avoids harmful chemical residues.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of agricultural technology, in particular to a preparation method of a chitosan selenium-supplemented water-retaining agent. BACKGROUND

[0002] Water-retaining agents, as an important agricultural water-saving material, play a key role in agricultural production in terms of their principles and applications. They can absorb and retain water, and then slowly release it when plants need it, thereby improving the water-retaining performance 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 improving crop yield and saving water resources.

[0003] However, in high-temperature environments, the performance of water-retaining agents may be affected. Due to the accelerated evaporation rate caused by high temperatures, the water content in the water-retaining agent may quickly decrease, which directly affects its water-retaining effect under high-temperature and drought conditions. It is worth noting that different types of water-retaining agents perform differently in high-temperature environments. Some synthetic polymer water-retaining agents may lose some of their water-retaining ability due to structural changes caused by high temperatures; while some water-retaining agents based on natural high molecular materials, such as chitosan-based materials, may be able to resist the effects of high temperatures to some extent, maintaining their water-retaining performance.

[0004] However, the existing water-retaining agent technology generally has the problem of insufficient temperature responsiveness. In high-temperature or low-temperature environments, many water-retaining agents cannot effectively regulate their water retention and release, resulting in rapid evaporation of water in high-temperature conditions, and excessive retention of water in low-temperature conditions, 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 have long-term adverse effects on soil structure and the 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 the soil.

[0006] At the same time, the existing water-retaining agents have limited scope of application, mainly due to differences in soil types, climate conditions and crop species in different regions. Many water-retaining agents are only suitable for specific types of soil or crops, lacking broad applicability, which limits the promotion and application of water-retaining agents in different regions. SUMMARY

[0007] To solve or partially solve the problems in the related art, the present application provides a preparation method of a chitosan selenium-supplemented 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 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 soils and crop types, and thus provide more efficient, intelligent and environmentally friendly water management solutions for agricultural production.

[0008] The first aspect of the present application provides a preparation method of a chitosan selenium-supplemented water-retaining agent, comprising the following steps:

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

[0010] b. Dissolve 20 g of poly(N-isopropyl acrylamide-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 process for 10 min using an ultrasonic processor;

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

[0013] e. Add 1 g of a crosslinking agent, and stir for 1 h to promote crosslinking;

[0014] 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 value to 5.5-6.0, and stir uniformly;

[0015] g. Perform homogenization treatment using a high-speed homogenizer;

[0016] h. Perform drying by a spray dryer;

[0017] i. Cool the powder after spray drying to room temperature, and package.

[0018] Further, the crosslinking agent is glutaraldehyde.

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

[0020] Further, it is characterized in that the high-speed homogenization treatment time is 10 min.

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

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

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

[0024] It should be understood that the foregoing general description and the following detailed description are only exemplary and explanatory, and cannot limit the application.

[0025] The beneficial technical effects of the application are:

[0026] Through the linkage effect of multiple components, the water retaining agent realizes intelligent response to temperature changes, maintains good water retention performance, and adjusts nutrient release according to environmental conditions to provide comprehensive support for plant growth. The design of this composite system not only solves the temperature adaptability of the control group water retaining agent, but also significantly improves the overall performance and application range of the water retaining agent through the synergistic effect of the components.

[0027] The product has the function of slow-release selenium, based on the synergistic effect of polymer network and selenium nanoparticles. The selenium nanoparticles are embedded in the polymer network and released slowly through diffusion. The concentration gradient inside and outside the water retaining agent and the multiple 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 have high bioavailability. By adjusting the initial loading amount and network crosslinking degree, 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 the utilization efficiency, and reduces the environmental risk.

[0028] The product is composed of natural macromolecules and biodegradable synthetic polymers, which can gradually decompose in the soil. The natural macromolecules are completely degraded by microorganisms into carbon dioxide and water; the synthetic polymers are decomposed into simple organic matter through hydrolysis and microbial action; the temperature-sensitive component is finally degraded by oxidation and hydrolysis. The selenium nanoparticles are absorbed by plants or combined with soil elements, and will not accumulate for a long time. The use of biodegradable crosslinking agents ensures that the entire network structure can be completely decomposed. This comprehensive biodegradation process makes the product leave no harmful chemical residues, achieving environmental friendliness and sustainability. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 The surface electron microscope image of the product prepared in Example 1 of the application after drying;

[0030] Figure 2 The surface electron microscope image of the product prepared in Example 1 of the application after water absorption; DETAILED DESCRIPTION

[0031] Alternative embodiments of the present application will be described in greater detail below, with reference to the drawings. While several embodiments of the present application are shown in the drawings, it should be understood that the present application can be embodied in various forms without being limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present application to those skilled in the art.

[0032] The terminology used in this application is for the purpose of describing particular embodiments only and is not intended to be limiting of the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms "comprises" and / or "comprising," when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0033] The preparation method of the chitosan selenium supplemented water retaining agent of the present application will be described in detail below in conjunction with the drawings, as follows:

[0034] The present application provides a preparation method of a chitosan selenium supplemented water retaining agent, comprising the following steps:

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

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

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

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

[0039] e. Add 1g of a crosslinking agent, and stir for 1h to promote crosslinking;

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

[0041] g. Homogenize using a high-speed homogenizer;

[0042] h. Dry by a spray dryer;

[0043] i. Cool the powder after spray drying to room temperature, and package.

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

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

[0046] In a low-temperature environment: the polymer chains of P(NIPAAm-co-AAc) are in an extended state, forming a highly hydrophilic network structure with chitosan, maximizing water absorption capacity.

[0047] In a high-temperature environment: when the polymer chains of P(NIPAAm-co-AAc) begin to shrink, the presence of chitosan can partially offset this shrinkage effect, maintaining a certain network structure and water-retaining capacity. The water absorption and swelling properties of chitosan can compensate for the shrinkage of P(NIPAAm-co-AAc), so that the water-retaining effect is still good under high-temperature conditions.

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

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

[0050] Throughout the temperature range: the natural moisturizer can enhance the overall moisturizing performance of the water-retaining agent.

[0051] In a high-temperature environment: when P(NIPAAm-co-AAc) begins to release water, the natural moisturizer can slow down the evaporation rate of water, and synergize with P(NIPAAm-co-AAc) and chitosan to maintain the overall water-retaining effect of the water-retaining agent.

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

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

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

[0055] In a high-temperature environment: as the polymer chains of P(NIPAAm-co-AAc) shrink, the network structure becomes more loose, and the release rate of selenium nanoparticles increases. This temperature-responsive release mechanism can provide more selenium elements to plants when needed (such as under high-temperature stress conditions), enhancing the stress resistance of plants.

[0056] 4. Regulating effect of biodegradable polymer

[0057] The biodegradable polymer plays an important regulating role in the whole system:

[0058] In low temperature environment: The biodegradable polymer, together with other components, forms the overall structure of the water-retaining agent, enhancing its mechanical strength and stability.

[0059] In high temperature environment: The degradation rate of the biodegradable polymer increases, providing more space for the phase transition of P(NIPAAm-co-AAc), optimizing the water-retaining and releasing performance. At the same time, this degradation process also helps the gradual decomposition of the water-retaining agent in the soil, improving environmental compatibility.

[0060] 5. Overall linkage effect

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

[0062] In low temperature environment, the components work together to maximize water absorption and retention capacity.

[0063] During temperature rise, the temperature-responsive change of P(NIPAAm-co-AAc) triggers the dynamic regulation of the whole system, while other components such as chitosan and natural moisturizers play a buffering and compensating role.

[0064] In high temperature environment, although P(NIPAAm-co-AAc) starts to release water, the presence of other components ensures that the water-retaining agent can still maintain the necessary water-retaining 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-retaining agent realizes intelligent response to temperature changes, maintaining good water-retaining performance while adjusting nutrient release according to environmental conditions, providing comprehensive support for plant growth. The design of this composite system not only solves the deficiencies of the control group water-retaining agent in temperature adaptability, but also significantly improves the overall performance and application range of the water-retaining agent through the synergistic effect of the components.

[0066] In addition, the product also has the function of slow-release selenium, mainly based on the synergistic effect of polymer network structure and selenium nanoparticles. In the preparation process, selenium nanoparticles are uniformly dispersed and embedded in the polymer network to form a physical barrier to limit direct release. The release of selenium nanoparticles is mainly controlled by diffusion, slowly diffusing 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-retaining agent becomes the driving force for sustained release. The multiple polymer barrier structure in the water-retaining agent further regulates the release process to ensure long-term slow release. Over time, the erosion and degradation of the water-retaining agent surface also become an auxiliary release mechanism. The pH responsiveness of certain components can adjust the network structure according to changes in soil pH, affecting the release rate. The released selenium nanoparticles have high bioavailability due to their small size and large surface area. By adjusting the initial loading, polymer network crosslinking degree and other parameters, 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, the slow-release system controlled by multiple mechanisms in the product realizes the intelligent release of selenium elements, providing a sustained and stable supply of selenium nutrition for plants, improving the utilization efficiency of selenium and reducing environmental risks.

[0067] Finally, the main body of the water-retaining agent of the present application is composed of natural high molecular materials and biodegradable synthetic polymers, which can be gradually decomposed by physical, chemical and biological actions in the soil environment. Natural polymers such as chitosan and starch can be completely degraded into carbon dioxide and water under the action of soil microorganisms. The synthetic polymer part, such as polyacrylamide, is 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 upon long-term exposure to the soil environment, and will eventually be degraded into simple organic matter. These degradation products are either absorbed and utilized by plants or further transformed 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 crosslinking agent used in the product is biodegradable, ensuring that the entire network structure can be completely decomposed. 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 an embodiment of the present application, the crosslinking agent is glutaraldehyde.

[0069] In an embodiment of the present application, the inlet air temperature of the spray drying is 150℃ and the outlet air temperature is 80℃.

[0070] In one embodiment of the present application, the time of the high-speed homogenization process is 10 minutes.

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

[0072] In one embodiment of the present application, the particle size of the nano-selenium is 20-50 nm.

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

[0074] For a clearer understanding of the present application, the following examples are provided for further illustration.

[0075] Example 1

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

[0077] 2. Dissolve 20 g of poly(N-isopropyl acrylamide-co-acrylic acid) in 200 ml of purified water, and stir for 30 minutes 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 minutes.

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

[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 until uniform.

[0082] 7. Perform a homogenization process using a high-speed homogenizer, and the processing time is 10 minutes.

[0083] 8. Dry by a spray dryer, with an inlet temperature of 150°C and an outlet temperature of 80°C.

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

[0085] Test Example 1: Water-retention performance test

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

[0087] 2. Materials:

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

[0089] Commercially available polyacrylate potassium water-retaining agent (control group)

[0090] Analytical balance (accuracy 0.001 g)

[0091] Constant temperature and humidity chamber

[0092] Glass culture dish

[0093] 3. Experimental procedure:

[0094] S1 Preparation:

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

[0096] b) Gently absorb the excess water on the surface of the sample with filter paper and record the initial mass (W0).

[0097] S2 Set temperature conditions:

[0098] Set the constant temperature and humidity chamber to 15°C, 25°C, 35°C, and 45°C, respectively, and set the relative humidity to 60%.

[0099] S3 Water-retaining performance test:

[0100] a) Place the fully water-absorbed samples (3 parallel samples for each) into pre-weighed glass culture dishes.

[0101] b) Place the samples in the constant temperature and humidity chamber set to the specified temperature.

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

[0103] d) Immediately after weighing, place the samples back in the constant temperature and humidity chamber.

[0104] Data processing:

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

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

[0107] Experimental results:

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

[0109]

[0110] From the table, it can be observed that:

[0111] 1. At all temperature conditions, the water retention agent of the present application consistently maintains higher water retention rate than the control group.

[0112] 2. As temperature increases, the water retention rate of both water retention agents shows a downward trend, but the water retention agent of the present application has a smaller decline.

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

[0114] 4. In long-term (96 hours) water retention tests, the water retention agent of the present application shows 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 retention agents is relatively small, but the water retention agent of the present application still performs better.

[0116] The above has described various embodiments of the present application, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and changes are obvious to those skilled in the art without departing from the scope and spirit of the described embodiments. The choice of terms used herein is intended to best explain the principles, practical applications, or improvements to the technology in the market of the embodiments, or to enable other ordinary skilled persons in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a chitosan selenium-supplementing water-retaining agent, characterized in that: The following steps are involved: a. Dissolve 30g of chitosan in 1000ml of purified water containing 1% acetic acid and stir for 1-2h until completely dissolved; b. Dissolve 20g of poly (N-isopropylacrylamide -co- acrylic acid) in 200ml of purified water and stir for 30min until completely dissolved; c. Disperse 5g of nano-selenium in 15ml of glycerol and treat with an ultrasonic processor for 10min; d. The solutions of steps a, b and c are mixed and stirred evenly; e. Add 1g of crosslinking agent and stir for 1h to promote crosslinking; f. Add 15ml glycerol, 10g polylactic acid, 5g seaweed extract, 2g vitamin E and 1g 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; The cross-linking agent is glutaraldehyde; The inlet air temperature of the spray drying is 150°C and the outlet air temperature is 80°C; The high-speed homogenization treatment time is 10 minutes; The chitosan has a deacetylation degree greater than 85% and is a medium molecular weight chitosan; The particle size of the nano-selenium is 20-50 nm.

2. A chitosan selenium supplement and water-retaining agent, characterized in that: Prepared according to the preparation method of claim 1.

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