Preparation method and agricultural application of nano-selenium fertilizer prepared by electric etching method

Abstract

The invention provides a preparation method of a nano-selenium fertilizer prepared by an electric etching method and agricultural application. The preparation method of the nano-selenium fertilizer prepared by the electric etching method comprises the following steps: S1, preparing a selenium-containing precursor solution; s2, connecting a graphite rod with a direct-current power supply anode and immersing into the solution, and connecting another conductive substance with a direct-current power supply cathode; s3, applying direct-current voltage for etching, and performing centrifugation and concentration treatment on the electrolyte to obtain the nano-selenium fertilizer; the nano-selenium fertilizer is added into a hydroponic nutrient solution, the problem of large-scale production of the nano-selenium fertilizer is solved with a low-cost and green process through an electrochemical etching in-situ synthesis path, the bottleneck of traditional selenium fertilizer absorption efficiency is broken through depending on a selenium-carbon quantum dot composite structure, and an efficient solution is provided for agricultural quality and yield improvement.

Description

Technical Field

[0001] The present application relates to the technical field of nanomaterials, and in particular to a method for preparing a nano-selenium fertilizer prepared by an electro-etching method and its agricultural application. Background Art

[0002] With the advancement of agricultural modernization, the need to improve crop yield and quality is becoming increasingly urgent. Selenium, as an important nutrient, significantly promotes plant growth and stress resistance. Traditional inorganic selenium fertilizers such as Na2SeO3 and Na2SeO4 can increase plant biomass, but their absorption and utilization rate when applied to soil is low, at only approximately 10%. Nano-selenium, due to its small particle size, large specific surface area, high bioactivity, and low toxicity, exhibits unique advantages in the agricultural sector.

[0003] Existing nano-selenium fertilizer preparation technologies often use complex processes (e.g., patent CN202411963386.6), such as solution preparation, multi-step reaction, aging, and centrifugation, which are harsh conditions and cumbersome operations. Some methods also require the use of special raw materials such as enzyme agents (e.g., patent CN202410887850.1), organic chelating agents (e.g., patent CN202410800901.2), or selenium-rich soil, which are relatively expensive. These limitations make nano-selenium fertilizer difficult to produce on a large scale, and the high production cost makes it difficult to promote it widely.

[0004] In recent years, carbon quantum dots (CQDs) have shown great potential in the agricultural field due to their unique properties. After being loaded with trace elements, they can play an excellent role in plant growth, photosynthesis and stress resistance. The gradual construction of carbon quantum dots through chemical reactions makes it easy to control the size, shape and surface functional groups of carbon quantum dots. However, its synthesis process is relatively complex, requires specific precursors, and is relatively expensive. Electrochemical etching is an efficient and low-cost synthesis method. It oxidizes and decomposes bulk carbon materials such as graphite into carbon quantum dots through electrochemical reactions. This method is simple to operate, low-cost, and suitable for large-scale production. At the same time, defect engineering can be introduced during the electrochemical etching process. By controlling the electrochemical conditions, various metal / non-metal elements can be doped into carbon quantum dots to achieve material modification. Its application in the agricultural field has shown great potential and provides new ideas for increasing crop yields and recycling resources.

[0005] In this context, developing a new and efficient selenium-doped carbon quantum dot fertilizer and improving the stability of selenium and plant absorption and utilization rate by optimizing its synthesis method are of great significance for promoting crop growth. Summary of the Invention

[0006] The present application provides a method for preparing nano-selenium fertilizer prepared by an electro-etching method and its agricultural application, in order to solve the problems raised in the above background technology.

[0007] To solve the above technical problems, the present application discloses a method for preparing nano-selenium fertilizer by electro-etching, comprising the following steps:

[0008] S1. Prepare a selenium-containing precursor solution;

[0009] S2. Connect a graphite rod to the positive terminal of a DC power supply and immerse it in the solution. Connect another conductive object to the negative terminal of the DC power supply.

[0010] S3. Apply DC voltage for etching, centrifuge and concentrate the electrolyte to obtain nano-selenium fertilizer.

[0011] Furthermore, the selenium-containing precursor is an inorganic selenium compound.

[0012] Furthermore, the inorganic selenium compound is selected from one of sodium selenate, sodium selenite, selenium dioxide, selenic acid or selenous acid.

[0013] Furthermore, the selenium concentration of the selenium-containing precursor solution is 0.1-100 g / L, and the pH value is 2-10.

[0014] Furthermore, the solution in step S1 further contains one of an inorganic acid, an inorganic base or an organic solvent; the inorganic acid is one of hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, the inorganic base is one of sodium hydroxide, potassium hydroxide or calcium hydroxide, and the organic solvent is one of alcohol, ketone, aldehyde or ester.

[0015] Furthermore, the negative electrode conductor in step S2 is a graphite rod, a metal rod, a graphite sheet or a metal sheet.

[0016] Furthermore, the prepared nano-selenium particles have a particle size of 3-10 nm and are loaded on a carbon quantum dot carrier.

[0017] Furthermore, the carbon quantum dot carrier is in-situ generated by electrochemical etching of a graphite rod, and has a selenium-doped defect structure on its surface.

[0018] Furthermore, the nano-selenium fertilizer prepared by the preparation method is used in agriculture by adding the nano-selenium fertilizer to a hydroponic nutrient solution at a concentration of 0.1-100 mg / L.

[0019] Furthermore, the crops include leafy vegetables or cereal crops, and the application method is foliar spraying, irrigation fertilization or hydroponic addition.

[0020] Compared with the prior art, this application provides a method for preparing nano-selenium fertilizer prepared by electro-etching and its agricultural application, which has the following beneficial effects:

[0021] 1. The present application can effectively and quickly prepare nano-selenium fertilizer with high purity and small particle size. The particle size distribution of nano-selenium particles is between 3-10nm. The nano-selenium fertilizer can effectively increase the biomass of plants, increase the selenium content in plants, better promote plant growth and improve the nutritional value of plants;

[0022] 2. The particle size of the nanoparticles of the present application is between 3-10 nm, with good dispersibility and stability, which is convenient for efficient application in agricultural production, improving the absorption and utilization of selenium by crops. The synthesis process of this nano-selenium fertilizer is simple, low-cost, green and environmentally friendly, and is conducive to industrial mass production;

[0023] 3. The process of the present application is efficient, simple, and low-cost. It uses a one-step electro-etching method to directly generate nano-selenium-carbon quantum dot composites, eliminating the complex processes of multi-step reactions, aging, and chelating agent addition in traditional processes. The raw materials are inexpensive inorganic selenium and graphite rods, and no selenium-rich soil or biological agents are required, which significantly reduces production costs.

[0024] 4. The nano-selenium particles of the present application have uniform particle size and high stability. Nano-selenium particles with stable particle size can be obtained by regulating electrical parameters. The in-situ generated selenium-doped carbon quantum dot carrier provides structural support, enhances the dispersibility and chemical stability of nano-selenium, and avoids agglomeration failure. The carrier of the present application can synergistically enhance the absorption efficiency of plants. The selenium-doped defect structure on the surface of carbon quantum dots enhances the biological activity of selenium. Combined with the nano-size effect, it significantly improves the absorption and utilization rate of selenium by crops. It is environmentally friendly and adaptable to a variety of agricultural scenarios. The process does not require toxic organic solvents, and the reaction by-products are recyclable electrolytes, which meets the requirements of green production. The finished product can be flexibly used for foliar spraying, irrigation or hydroponics, and is effective on leafy vegetables and cereal crops at low concentrations, with a wide range of applicability. It can significantly increase crop yield and nutritional value. Nano-selenium fertilizer simultaneously increases crop biomass (leaf length / root length) and selenium enrichment by enhancing photosynthesis and stress resistance, achieving both "increased production" and "nutrition enhancement". BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 This is a TEM high-resolution transmission electron microscope image of the nano-selenium fertilizer in Example 1;

[0026] Figure 2 This is a TEM high-resolution transmission electron microscope image of the nano-selenium fertilizer in Example 2;

[0027] Figure 3 This is a TEM high-resolution transmission electron microscope image of the nano-selenium fertilizer in Example 3;

[0028] Figure 4 This is a TEM high-resolution transmission electron microscope image of the nano-selenium fertilizer in Example 4;

[0029] Figure 5This is a TEM high-resolution transmission electron microscope image of the nano-selenium fertilizer in Example 5;

[0030] Figure 6 This is a TEM high-resolution transmission electron microscope image of the nano-selenium fertilizer of Example 6;

[0031] Figure 7 This is the TEM high-resolution transmission electron microscopy image of the mass production case 1 nano-selenium fertilizer;

[0032] Figure 8 This is the TEM high-resolution transmission electron microscopy image of the mass production case 2 nano-selenium fertilizer;

[0033] Figure 9 This is the high-resolution electron microscopy test result of Example 1;

[0034] Figure 10 These are the results of the wheat hydroponic growth experiments for mass production case 1, mass production case 2, and the comparative example. DETAILED DESCRIPTION

[0035] The preferred embodiments of the present application are described below. It should be understood that the preferred embodiments described herein are only used to illustrate and explain the present application and are not used to limit the present application.

[0036] In addition, in this application, descriptions such as "first" and "second" are only used for descriptive purposes and do not specifically refer to the order or sequence, nor are they used to limit this application. They are only used to distinguish components or operations described with the same technical terms, and cannot be understood as indicating or implying their relative importance or implicitly indicating the number of technical features indicated. Therefore, the features defined as "first" and "second" may explicitly or implicitly include at least one such feature. In addition, the technical solutions and technical features between the various embodiments can be combined with each other, but they must be based on the ability of ordinary technicians in this field to implement them. When the combination of technical solutions is contradictory or cannot be implemented, it should be deemed that such a combination of technical solutions does not exist and is not within the scope of protection required by this application.

[0037] Unless otherwise specified, the examples and comparative examples are parallel experiments with the same components, component contents, preparation steps, and preparation parameters. The experimental methods in the following examples are conventional methods unless otherwise specified. The experimental materials used in the following examples are analytical reagents (AR) unless otherwise specified, which were purchased from commercial channels.

[0038] Example 1: 50g sodium selenate is added to 1L ultrapure water, stirred magnetically at 25°C, 800rpm speed to complete dissolution, 1mol / LHCl solution is added dropwise, adjusted to pH=4, a graphite rod with a diameter of 10mm and a length of 30cm is inserted into the solution and connected to the positive pole of a DC power supply, and another graphite rod of the same size is connected to the negative pole, anode and cathode are set to be parallel with a spacing of 50mm, an immersion depth of 250mm, a 25°C constant temperature water bath is opened, a DC power supply is started, an initial current is 2.15A, and a DC power supply voltage is set to 10V, and the whole process is kept away from light for 10h; at a speed of 8000rpm, a temperature of 4°C is centrifuged for 15min, filtered through a nylon filter membrane, and freeze-dried for 24h at 10Pa and -50°C to obtain a nano-selenium fertilizer solution. Its micromorphology is observed by high-resolution transmission electron microscopy, and the results are as follows Figure 1 shown.

[0039] Example 2: In this embodiment, the selenium-containing precursor solution is prepared from 10 g / L of sodium selenite, and the pH value of the solution is adjusted to 7 by sodium hydroxide. Two graphite rods with a diameter of 8 mm and a length of 50 cm are inserted into the experimental device as the positive electrode, and the negative electrode is a copper rod. The electro-etching reaction is carried out at a voltage of 50 V for 30 hours. After the reaction is completed, the electrolyte is centrifuged to remove the precipitate, and then concentrated by high-temperature drying to obtain a nano-selenium fertilizer solution. The micromorphology is observed by high-resolution transmission electron microscopy, and the results are as follows Figure 2 shown.

[0040] Example 3: This example uses a 20g / L selenium dioxide solution as a selenium-containing precursor, and adjusts the pH value to 6 by adding phosphoric acid. In the experiment, three graphite rods with a diameter of 12mm and a length of 40cm are used as positive electrodes, and an iron plate is used as the negative electrode. The electro-etching reaction is carried out at a voltage of 30V for 20 hours. After the reaction is completed, the electrolyte is centrifuged to remove impurities, and then concentrated by rotary evaporation to obtain a nano-selenium fertilizer solution. The micromorphology is observed by high-resolution transmission electron microscopy, and the results are as follows Figure 3 shown.

[0041] Example 4: In this example, a sodium selenite solution with a concentration of 100 g / L was prepared, and the pH value was adjusted to 9 by potassium hydroxide. Four graphite rods with a diameter of 15 mm and a length of 60 cm were inserted into the solution as positive electrodes, and the negative electrode was a graphite plate. The electro-etching reaction was carried out at a voltage of 80 V for 60 hours. After the reaction was completed, the electrolyte was centrifuged to remove the precipitate, and then concentrated by distillation purification to obtain a nano-selenium fertilizer solution. The micromorphology was observed by high-resolution transmission electron microscopy, and the results were as follows. Figure 4 shown.

[0042] Example 5: In this embodiment, the selenium-containing precursor solution is prepared from 5g / L sodium selenate, and the pH value is adjusted to 3 by adding hydrochloric acid. A graphite rod with a diameter of 5mm and a length of 20cm is inserted into the experimental device as the positive electrode, and the negative electrode is a copper rod. The electro-etching reaction is carried out at a voltage of 20V for 15 hours. After the reaction is completed, the electrolyte is centrifuged to remove impurities, and then concentrated by freeze drying to obtain a nano-selenium fertilizer solution. The micromorphology is observed by high-resolution transmission electron microscopy, and the results are as follows Figure 5 shown.

[0043] Example 6: This example uses a 40g / L selenium dioxide solution as a selenium-containing precursor, and adjusts the pH value to 8 by adding sodium hydroxide. In the experiment, two graphite rods with a diameter of 10mm and a length of 50cm were used as the positive electrode, and the negative electrode was an iron rod. The electro-etching reaction was carried out at a voltage of 60V for 40 hours. After the reaction was completed, the electrolyte was centrifuged to remove the precipitate, and then concentrated by a high-temperature drying method to obtain a nano-selenium fertilizer solution. The micromorphology was observed by high-resolution transmission electron microscopy, and the results were as follows. Figure 6 shown.

[0044] A method for preparing nano-selenium fertilizer by electro-etching method comprises:

[0045] S1. preparing a selenium-containing precursor solution using inorganic selenium;

[0046] S2. Inserting one or more graphite rods into the selenium-containing precursor solution and connecting the graphite rods to the positive electrode of a DC power supply; at the same time, connecting another conductive object to the electrode of the DC power supply. The conductive object can be a graphite rod, various metal rods, or graphite sheets / plates, various metal sheets / plates;

[0047] S3, the DC power supply is set to 5-100V, the etching time is 5-60h, and the obtained electro-etched electrolyte is subjected to centrifugation, concentration and other treatments to obtain a nano-selenium fertilizer solution.

[0048] The inorganic selenium in S1 is one of sodium selenate, sodium selenite, selenium dioxide, selenic acid or selenious acid; the selenium concentration of the selenium-containing precursor solution in S2 is 0.1-100 g / L;

[0049] The selenium-containing precursor solution described in S1 may also include an inorganic acid, which is one of hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid; an inorganic base, which is one of sodium hydroxide, potassium hydroxide, and calcium hydroxide; and an organic solvent, which is one of alcohol, ketone, aldehyde, and ester. There is no special restriction on the amount of the selenium-containing precursor solution used, and it can be adjusted according to the material and size of the conductive material, as well as the conditions of electrolysis; the selenium-containing precursor solution described in S1 adjusts the pH value of the solution by adding acid or alkali, and the pH value is 2-10; the size of the graphite rod described in S2 can be adjusted according to the capacity of the container; the concentration process involved in S3 can be high-temperature drying, freeze drying, rotary evaporation, or distillation purification; the pH value of the nano-selenium fertilizer solution in S3 is adjusted according to actual application requirements, and the pH value of the solution is adjusted by adding acid or alkali.

[0050] Application Example 1: Application of nano-selenium fertilizer in hydroponic vegetables: The application object is lettuce (leafy vegetables), and the application method is to add the hydroponic nutrient solution. The concentration of nano-selenium fertilizer is 20 mg / L, and the application cycle is 7 days.

[0051] Application Example 2: Application of nano-selenium fertilizer in hydroponic vegetables: The application object is wheat, and the application method is to add hydroponic nutrient solution. The concentration of nano-selenium fertilizer is 20 mg / L, and the application cycle is 5 days.

[0052] Mass production case 1

[0053] In this mass production case, a total of 1 ton of sodium selenate solution with a concentration of 50g / L was prepared, and the pH value of the solution was adjusted to 7 by sodium hydroxide. In a 1 cubic meter reaction vessel, 50 graphite rods with a diameter of 10mm and a length of 50cm were inserted as positive electrodes, and copper rods were used as negative electrodes. The DC power supply voltage was set to 50V, and the electroetching reaction was carried out for 10 hours. After the reaction, the obtained electrolyte was centrifuged to remove large particle impurities, and then concentrated by freeze drying to obtain a nano-selenium fertilizer solution. This mass production method can efficiently produce a large amount of nano-selenium fertilizer solution to meet the needs of large-scale agricultural applications. The micromorphology was observed by high-resolution transmission electron microscopy, and the results are as follows Figure 7 This sample was prepared with a 20 mg / L nutrient solution, and the germinated plants were placed in the nutrient solution for hydroponic growth experiments of wheat and lettuce. The test results are shown in Tables 1 and 2.

[0054] Table 1 shows the effects of applying nano-selenium fertilizer on the average leaf length, leaf width and root length of lettuce 7 days later:

[0055]

[0056]

[0057] Mass production case 2

[0058] In this mass production case, a total of 1 ton of 50g / L sodium selenite solution was prepared, and the pH value of the solution was adjusted to 7 by sodium hydroxide. Fifty graphite rods with a diameter of 8mm and a length of 50cm were inserted into a 1 cubic meter reaction vessel as the positive electrode, and the negative electrode was a copper rod. The electro-etching reaction was carried out at a voltage of 10V for 30 hours. After the reaction was completed, the electrolyte was centrifuged to remove the precipitate, and then concentrated by high-temperature drying to obtain a nano-selenium fertilizer solution. This method can stably produce high-quality nano-selenium fertilizer solutions, which are suitable for large-scale agricultural production. The micromorphology was observed by high-resolution transmission electron microscopy, and the results are as follows Figure 8 This sample was prepared with a 20 mg / L nutrient solution, and the germinated plants were placed in the nutrient solution for hydroponic growth experiments of wheat and lettuce. The test results are shown in Table 2.

[0059] Table 2 shows the effect of applying nano-selenium fertilizer on the average root length and seedling length of wheat 5 days later:

[0060] Average root length / cm Average seedling length / cm Mass production case 1 10.87 11.18 Mass production case 2 11.80 12.30 Comparative Example 9.03 9.43

[0061] Comparative Examples 9.03 9.43 Obviously, those skilled in the art may make various changes and modifications to this application without departing from the spirit and scope of this application. If such changes and modifications fall within the scope of the claims of this application and their equivalents, this application is intended to include such changes and modifications.

Claims

1. A method for preparing nano-selenium fertilizer by electro-etching, characterized in that: The following steps are involved: S1. preparing a selenium-containing precursor solution; S2. Connect the graphite rod to the positive terminal of a DC power supply and immerse it in the solution. Connect another conductive object to the negative terminal of the DC power supply. S3. Apply DC voltage for etching, centrifuge and concentrate the electrolyte to obtain nano-selenium fertilizer.

2. The method for preparing nano-selenium fertilizer prepared by electro-etching according to claim 1, wherein The selenium-containing precursor is an inorganic selenium compound.

3. The preparation method according to claim 2, characterized in that The inorganic selenium compound is selected from one of sodium selenate, sodium selenite, selenium dioxide, selenic acid or selenous acid.

4. The preparation method according to claim 1, characterized in that The selenium concentration of the selenium-containing precursor solution is 0.1-100 g / L, and the pH value is 2-10.

5. The preparation method according to claim 1, characterized in that The solution in step S1 further contains one of an inorganic acid, an inorganic base or an organic solvent; the inorganic acid is one of hydrochloric acid, sulfuric acid, nitric acid or phosphoric acid, the inorganic base is one of sodium hydroxide, potassium hydroxide or calcium hydroxide, and the organic solvent is one of an alcohol, a ketone, an aldehyde or an ester.

6. The preparation method according to claim 1, characterized in that The negative electrode conductive material in step S2 is a graphite rod, a metal rod, a graphite sheet or a metal sheet.

7. The preparation method according to claim 1, characterized in that The prepared nano-selenium particles have a particle size of 3-10 nm and are loaded on a carbon quantum dot carrier.

8. The preparation method according to claim 7, characterized in that The carbon quantum dot carrier is in-situ generated by electrochemically etching a graphite rod, and has a selenium-doped defect structure on the surface.

9. Application of the nano-selenium fertilizer prepared by the preparation method according to claim 1 in agriculture, characterized in that: The nano-selenium fertilizer is added to a hydroponic nutrient solution at a concentration of 0.1-100 mg / L.

10. The use according to claim 9, characterized in that Crops that are applied with nano-selenium fertilizer include leafy vegetables or cereal crops, and the application methods are foliar spraying, irrigation fertilization or hydroponic addition.

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