阅读说明：本技术 核膜结构的光敏性保水缓释肥料及其制备方法 (Photosensitive water-retention slow-release fertilizer with nuclear membrane structure and preparation method thereof ) 是由 李燕 戴佳锟 于 2021-09-17 设计创作，主要内容包括：本发明涉及一种核膜结构的光敏性保水缓释肥料及其制备方法。传统化肥普遍存在利用率不高的问题,而缓释化肥具有不利于土壤保水保温的缺陷。本发明将氧化淀粉水凝胶和海藻酸钠溶液混合,加入化肥后形成保水缓释内核材料；之后加入作为光敏外膜材料的聚多巴胺溶液,获得光敏性保水缓释肥料。本发明通过交联作用合成兼具保水和缓释性能的肥料内核,并通过离子相互作用合成含光敏材料的肥料外膜,获得的缓释肥料具有明显的核膜结构,缓释性能优异,明显提升了利用率,并能有效提高土壤持水率、提升土壤温度,进一步促进作物生长；同时,本发明采用无毒害、易降解的材料,可降低肥料流失造成的面源污染,减少环境污染,保护土壤结构。(The invention relates to a photosensitive water-retention slow-release fertilizer with a nuclear membrane structure and a preparation method thereof. The traditional fertilizer generally has the problem of low utilization rate, and the slow release fertilizer has the defect of being not beneficial to soil water retention and heat preservation. Mixing oxidized starch hydrogel and sodium alginate solution, and adding a chemical fertilizer to form a water-retaining slow-release core material; and then adding polydopamine solution serving as a photosensitive outer membrane material to obtain the photosensitive water-retention slow-release fertilizer. According to the invention, the fertilizer inner core with water retention and slow release performances is synthesized through a crosslinking effect, and the fertilizer outer membrane containing a photosensitive material is synthesized through an ionic interaction, so that the obtained slow release fertilizer has an obvious nuclear membrane structure, is excellent in slow release performance, obviously improves the utilization rate, can effectively improve the soil water retention rate and the soil temperature, and further promotes the growth of crops; meanwhile, the invention adopts non-toxic and easily degradable materials, thus reducing non-point source pollution caused by fertilizer loss, reducing environmental pollution and protecting soil structure.)

1. The preparation method of the photosensitive water-retention slow-release fertilizer with the nuclear membrane structure is characterized by comprising the following steps of:

the method comprises the following steps:

mixing oxidized starch hydrogel and sodium alginate solution, and adding a chemical fertilizer to form a water-retaining slow-release core material;

and then adding polydopamine solution serving as a photosensitive outer membrane material to obtain the photosensitive water-retention slow-release fertilizer.

2. The method for preparing a photosensitive water-retention slow-release fertilizer with a nuclear membrane structure according to claim 1, wherein the method comprises the following steps:

the method specifically comprises the following steps:

the method comprises the following steps: gelatinizing starch, adding the gelatinized starch into an oxidation reaction solution, and precipitating and purifying an obtained product to obtain oxidized starch hydrogel;

step two: mixing the oxidized starch hydrogel obtained in the step one with a sodium alginate solution, adding a chemical fertilizer into the mixture and completely dissolving to obtain a water-retaining slow-release core material;

step three: spraying the water-retention slow-release core material into a solution containing an emulsifier and calcium ions in a normal-temperature spraying manner;

step four: and C, carrying out reduced pressure suction filtration and drying on the reaction liquid obtained in the step three, then adding a polydopamine solution serving as a photosensitive outer membrane material, stirring at room temperature, carrying out reduced pressure suction filtration, drying and sieving to obtain the photosensitive water-retaining slow-release fertilizer.

3. The method for preparing a photosensitive water-retention slow-release fertilizer with a nuclear membrane structure according to claim 2, wherein the method comprises the following steps:

in the first step, the oxidation reaction liquid is KMnO₄With NaHSO₄The mixed solution of (1); KMnO in starch and mixed solution₄With NaHSO₄The mass ratio of (10-40): 1:(1-3).

4. The method for preparing a photosensitive water-retention slow-release fertilizer with a nuclear membrane structure according to claim 3, wherein the method comprises the following steps:

in the second step, the mass ratio of the sodium alginate in the sodium alginate solution to the starch in the first step is (1-9): 1.

5. The method for preparing a photosensitive water-retention slow-release fertilizer with a nuclear membrane structure according to claim 4, wherein the method comprises the following steps:

in the second step, the mass ratio of the chemical fertilizer to the sodium alginate in the sodium alginate solution is (1-5) to 1.

6. The method for preparing a photosensitive water-retention slow-release fertilizer with a nuclear membrane structure according to claim 5, wherein the method comprises the following steps:

in the third step, the emulsifier in the solution containing the emulsifier and calcium ions is polyvinyl alcohol, and the mass ratio of the polyvinyl alcohol to the calcium ions to the fertilizer is 1: 5: (20-50).

7. The method for preparing a photosensitive water-retention slow-release fertilizer with a nuclear membrane structure according to claim 6, wherein the method comprises the following steps:

in the fourth step, the mass ratio of the polydopamine in the polydopamine solution to the fertilizer is 1: (20-40).

8. The photosensitive water-retaining slow-release fertilizer with a nuclear membrane structure prepared by the method of claim 7.

Technical Field

The invention relates to a novel fertilizer, in particular to a photosensitive water-retention slow-release fertilizer with a nuclear membrane structure and a preparation method thereof.

Background

The utilization rate of chemical fertilizer in China is not high (30-40%), and the large amount of application of the chemical fertilizer can damage the soil structure of cultivated land, cause soil hardening and have poor water retention. In addition, because the penetration of nutrient substances is too fast, the plants can not absorb all nutrients, so that most elements are accumulated or leached into underground water, thereby causing water eutrophication and causing serious agricultural non-point source pollution.

The slow release fertilizer is an important means for solving the technical problems and becomes an important method for improving the utilization rate of the fertilizer. The early coating material of the slow release fertilizer is difficult to degrade or can generate other harmful substances, so that the environmental pollution is caused. Therefore, its development is gradually shifted to degradable, non-toxic, environmentally friendly materials.

At present, researches on various slow release fertilizers focus on how to slowly release nutrient elements, little attention is paid to water holding capacity and temperature of soil, and soil humidity and temperature are just important factors influencing crop growth, but related researches on slow release fertilizers considering the factors are few at present.

Disclosure of Invention

The invention aims to provide a photosensitive water-retention slow-release fertilizer with a nuclear membrane structure and a preparation method thereof.

In order to achieve the purpose, the technical scheme adopted by the invention is as follows:

the preparation method of the photosensitive water-retention slow-release fertilizer with the nuclear membrane structure is characterized by comprising the following steps of:

the method comprises the following steps:

mixing oxidized starch hydrogel and sodium alginate solution, and adding a chemical fertilizer to form a water-retaining slow-release core material;

and then adding polydopamine solution serving as a photosensitive outer membrane material to obtain the photosensitive water-retention slow-release fertilizer.

The method specifically comprises the following steps:

the method comprises the following steps: gelatinizing starch, adding the gelatinized starch into an oxidation reaction solution, and precipitating and purifying an obtained product to obtain oxidized starch hydrogel;

step two: mixing the oxidized starch hydrogel obtained in the step one with a sodium alginate solution, adding a chemical fertilizer into the mixture and completely dissolving to obtain a water-retaining slow-release core material;

step three: spraying the water-retention slow-release core material into a solution containing an emulsifier and calcium ions in a normal-temperature spraying manner;

step four: and C, carrying out reduced pressure suction filtration and drying on the reaction liquid obtained in the step three, then adding a polydopamine solution serving as a photosensitive outer membrane material, stirring at room temperature, carrying out reduced pressure suction filtration, drying and sieving to obtain the photosensitive water-retaining slow-release fertilizer.

In the first step, the oxidation reaction liquid is KMnO₄With NaHSO₄The mixed solution of (1); KMnO in starch and mixed solution₄With NaHSO₄The mass ratio of (10-40): 1:(1-3).

In the second step, the mass ratio of the sodium alginate in the sodium alginate solution to the starch in the first step is (1-9): 1.

In the second step, the mass ratio of the chemical fertilizer to the sodium alginate in the sodium alginate solution is (1-5) to 1.

In the third step, the emulsifier in the solution containing the emulsifier and calcium ions is polyvinyl alcohol, and the mass ratio of the polyvinyl alcohol to the calcium ions to the fertilizer is 1: 5: (20-50).

In the fourth step, the mass ratio of the polydopamine in the polydopamine solution to the fertilizer is 1: (20-40).

The photosensitive water-retaining slow-release fertilizer with the nuclear membrane structure is prepared by the method.

Compared with the prior art, the invention has the following beneficial effects:

1. the fertilizer prepared by the invention has multiple effects and characteristics of slow release, water retention and photosensitivity:

according to the invention, the fertilizer inner core with water retention and slow release performances is synthesized through a crosslinking effect, and the fertilizer outer membrane containing the photosensitive material is synthesized through an ionic interaction, so that the obtained slow release fertilizer has an obvious nuclear membrane structure, is excellent in slow release performance, obviously improves the utilization rate, can effectively improve the soil water retention rate and the soil temperature, and further promotes the growth of crops.

2. The fertilizer prepared by the invention can effectively reduce environmental pollution:

the invention adopts non-toxic and easily degradable materials, can reduce non-point source pollution caused by fertilizer loss, reduce environmental pollution and protect soil structure.

2. The raw materials adopted by the invention have obvious synergistic effect:

the fertilizer prepared by taking the sodium alginate as a carrier has a good slow release effect, and in order to improve the water retention performance of the sodium alginate, the oxidized starch hydrogel is introduced, so that the oxidized starch hydrogel and the sodium alginate are crosslinked to form a slow release fertilizer inner core with strong water absorption, and a poly dopamine outer membrane with photosensitivity is adsorbed on the outside, so that the slow release fertilizer with good water retention and photosensitivity effects is formed.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings of the embodiments can be obtained according to the drawings without creative efforts.

FIG. 1 is a schematic diagram of the water absorption effect of a fertilizer.

Fig. 2 is a schematic diagram of detecting the temperature change of the fertilizer under sunlight irradiation by an infrared camera.

Detailed Description

To facilitate an understanding of the invention, the invention will now be described more fully with reference to the accompanying drawings. The present invention may be embodied in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete.

In order to overcome the defects that the utilization rate of the traditional fertilizer is not high and the slow release fertilizer is not beneficial to soil water retention and heat preservation, the oxidized starch hydrogel and the sodium alginate solution are mixed, the fertilizer is added to form a water retention and slow release core material, and then the polydopamine solution serving as a photosensitive outer membrane material is added to prepare the slow release fertilizer with the core membrane structure. The preparation method specifically comprises the following steps:

the method comprises the following steps: and gelatinizing starch, adding the gelatinized starch into the oxidation reaction solution, and precipitating and purifying the obtained product to obtain oxidized starch hydrogel.

The oxidation reaction liquid can carry out oxidation modification on starch and is KMnO₄With NaHSO₄The mixed solution of (1); KMnO in starch and mixed solution₄With NaHSO₄The mass ratio of (10-40): 1:(1-3). Other similar oxidation reaction liquids capable of oxidatively modifying starch can also be used in the present invention.

Step two: and (3) mixing the oxidized starch hydrogel obtained in the step one with a sodium alginate solution, adding a chemical fertilizer into the mixture, and completely dissolving to obtain the water-retaining slow-release core material.

The mass ratio of the sodium alginate in the sodium alginate solution to the starch in the step one is (1-9):1, and the mass ratio of the chemical fertilizer to the sodium alginate in the sodium alginate solution is (1-5): 1. The fertilizer which can be used in the invention can be urea, and other water-soluble fertilizers can also be used, such as nitrogen, phosphorus and potassium fertilizers such as ammonium bicarbonate, ammonium nitrate, potassium chloride, potassium dihydrogen phosphate, calcium superphosphate and the like, and the fertilizer can cause environmental pollution when being overused, and the dosage can be effectively controlled by using a slow release means.

The fertilizer prepared by taking sodium alginate as a carrier has good slow release performance, but poor water retention performance. In order to improve the water retention performance of sodium alginate, oxidized starch hydrogel is introduced in the invention, and the oxidized starch hydrogel and the sodium alginate are crosslinked to form a slow-release fertilizer inner core with strong water absorption.

Step three: spraying the water-retaining slow-release core material into a solution containing an emulsifier and calcium ions in a normal-temperature spraying manner, and placing the solution containing the emulsifier and the calcium ions below a nozzle to enable mixed liquid drops formed by spraying to directly contact the solution.

The emulsifier in the solution containing the emulsifier and calcium ions is polyvinyl alcohol, and the mass ratio of the polyvinyl alcohol to the calcium ions to the fertilizer is 1: 5: (20-50). Sodium alginate is combined with calcium ions to form calcium alginate, so that the calcium alginate is solidified into balls, and the fertilizer is wrapped in the particles. The emulsifier enables the particles formed to be better dispersed in the solution.

Step four: and C, carrying out reduced pressure suction filtration and drying on the reaction liquid obtained in the step three, then adding a polydopamine solution serving as a photosensitive outer membrane material, stirring at room temperature, carrying out reduced pressure suction filtration, drying and sieving to obtain the photosensitive water-retaining slow-release fertilizer.

The mass ratio of polydopamine to the fertilizer in the polydopamine solution is 1: (20-40). The invention introduces oxidized starch hydrogel, forms a slow release fertilizer inner core with strong water absorption with sodium alginate through crosslinking, and simultaneously adsorbs a poly dopamine outer membrane with photosensitivity outside, thereby forming the slow release fertilizer with good water retention and photosensitivity.

Example 1:

the preparation method of the nuclear membrane structure photosensitive water-retention slow-release fertilizer specifically comprises the following steps:

the method comprises the following steps: and gelatinizing starch, adding the gelatinized starch into the oxidation reaction solution, and precipitating and purifying the obtained product to obtain oxidized starch hydrogel. The oxidation reaction solution is KMnO₄With NaHSO₄The mixed solution of (1); KMnO in starch and mixed solution₄With NaHSO₄The mass ratio of (A) to (B) is 10: 1:3.

Step two: and (3) mixing the oxidized starch hydrogel obtained in the step one with a sodium alginate solution, adding a chemical fertilizer into the mixture, and completely dissolving to obtain the water-retaining slow-release core material. The mass ratio of the sodium alginate in the sodium alginate solution to the starch in the step one is 1:1, and the mass ratio of the chemical fertilizer to the sodium alginate in the sodium alginate solution is 5: 1.

Step three: spraying the water-retaining slow-release core material into a solution containing an emulsifier and calcium ions in a normal-temperature spraying manner, and placing the solution containing the emulsifier and the calcium ions below a nozzle to enable mixed liquid drops formed by spraying to directly contact the solution. The emulsifier in the solution containing the emulsifier and calcium ions is polyvinyl alcohol, and the mass ratio of the polyvinyl alcohol to the calcium ions to the fertilizer is 1: 5: 20.

step four: and C, carrying out reduced pressure suction filtration and drying on the reaction liquid obtained in the step three, then adding a polydopamine solution serving as a photosensitive outer membrane material, stirring at room temperature, carrying out reduced pressure suction filtration, drying and sieving to obtain the photosensitive water-retaining slow-release fertilizer. The mass ratio of polydopamine to the fertilizer in the polydopamine solution is 1: 40.

example 2:

the preparation method of the nuclear membrane structure photosensitive water-retention slow-release fertilizer specifically comprises the following steps:

the method comprises the following steps: and gelatinizing starch, adding the gelatinized starch into the oxidation reaction solution, and precipitating and purifying the obtained product to obtain oxidized starch hydrogel. The oxidation reaction solution is KMnO₄With NaHSO₄The mixed solution of (1); KMnO in starch and mixed solution₄With NaHSO₄The mass ratio of (A) to (B) is 25: 1:2.

Step two: and (3) mixing the oxidized starch hydrogel obtained in the step one with a sodium alginate solution, adding a chemical fertilizer into the mixture, and completely dissolving to obtain the water-retaining slow-release core material. The mass ratio of the sodium alginate in the sodium alginate solution to the starch in the step one is 5:1, and the mass ratio of the chemical fertilizer to the sodium alginate in the sodium alginate solution is 2.5: 1.

Step three: spraying the water-retaining slow-release core material into a solution containing an emulsifier and calcium ions in a normal-temperature spraying manner, and placing the solution containing the emulsifier and the calcium ions below a nozzle to enable mixed liquid drops formed by spraying to directly contact the solution. The emulsifier in the solution containing the emulsifier and calcium ions is polyvinyl alcohol, and the mass ratio of the polyvinyl alcohol to the calcium ions to the fertilizer is 1: 5: 35.

step four: and C, carrying out reduced pressure suction filtration and drying on the reaction liquid obtained in the step three, then adding a polydopamine solution serving as a photosensitive outer membrane material, stirring at room temperature, carrying out reduced pressure suction filtration, drying and sieving to obtain the photosensitive water-retaining slow-release fertilizer. The mass ratio of polydopamine to the fertilizer in the polydopamine solution is 1: 30.

example 3:

the preparation method of the nuclear membrane structure photosensitive water-retention slow-release fertilizer specifically comprises the following steps:

the method comprises the following steps: and gelatinizing starch, adding the gelatinized starch into the oxidation reaction solution, and precipitating and purifying the obtained product to obtain oxidized starch hydrogel. The oxidation reaction solution is KMnO₄With NaHSO₄The mixed solution of (1); KMnO in starch and mixed solution₄With NaHSO₄Is 40: 1:1.

Step two: and (3) mixing the oxidized starch hydrogel obtained in the step one with a sodium alginate solution, adding a chemical fertilizer into the mixture, and completely dissolving to obtain the water-retaining slow-release core material. The mass ratio of the sodium alginate in the sodium alginate solution to the starch in the step one is 9:1, and the mass ratio of the chemical fertilizer to the sodium alginate in the sodium alginate solution is 1: 1.

Step three: spraying the water-retaining slow-release core material into a solution containing an emulsifier and calcium ions in a normal-temperature spraying manner, and placing the solution containing the emulsifier and the calcium ions below a nozzle to enable mixed liquid drops formed by spraying to directly contact the solution. The emulsifier in the solution containing the emulsifier and calcium ions is polyvinyl alcohol, and the mass ratio of the polyvinyl alcohol to the calcium ions to the fertilizer is 1: 5: 50.

step four: and C, carrying out reduced pressure suction filtration and drying on the reaction liquid obtained in the step three, then adding a polydopamine solution serving as a photosensitive outer membrane material, stirring at room temperature, carrying out reduced pressure suction filtration, drying and sieving to obtain the photosensitive water-retaining slow-release fertilizer. The mass ratio of polydopamine to the fertilizer in the polydopamine solution is 1: 20.

the above examples were tested for effects by specific experiments as follows:

5g of the photosensitive water-retaining slow-release fertilizer was added to 100g of dry sandy soil, 50mL of water was added every 3 days, and the release rate (%) of the fertilizer was measured on fixed days, and the results are shown in the following table.

2g of the photosensitive water-retaining slow-release fertilizer (example 2) was mixed with 100g of dry sandy soil and 50mL of water was added, and the water holding capacity and temperature of the soil were measured at a fixed time with respect to a soil sample to which a general slow-release fertilizer was added, and the results are shown in the following table.

The water absorption effect of the photosensitive water-retention slow-release fertilizer after being immersed in water for 1 hour is shown in figure 1.

The temperature change of the fertilizer under the irradiation of sunlight was detected by an infrared camera, and the result is shown in fig. 2. The photosensitive water-retaining slow-release fertilizer can be rapidly heated under illumination compared with the common slow-release fertilizer.

The present invention has been described in terms of specific examples, which are provided to aid understanding of the invention and are not intended to be limiting. For a person skilled in the art to which the invention pertains, several simple deductions, modifications or substitutions may be made according to the idea of the invention.