Method for using biochar as composite nitrogen fertilizer synergist and application of biochar

Abstract

The invention discloses a method for using biochar as a composite nitrogen fertilizer synergist and application, and belongs to the technical field of soil fertilizer synergism, the method comprises the following steps: S1, using corn straw as a raw material, and adopting an oxygen-limited temperature-controlled carbonization method to prepare biochar; and S2, wrapping the outer surface of the 3, 4-dimethyl pyrazole phosphate with the charcoal. Compared with treatment by singly applying the 3, 4-dimethylpyrazole phosphate, the degradation period of treatment by the 3, 4-dimethylpyrazole phosphate applied in combination with the charcoal in soil is prolonged by 10-21 days, and the characteristic of the charcoal shows that the charcoal can be used as a potential 3, 4-dimethylpyrazole phosphate slow-release carrier, so that the slow-release effect of the charcoal on the soil is improved. The effectiveness of the compound as a nitrogen fertilizer inhibitor is favorably prolonged.

Description

Technical Field

[0001] The invention belongs to the technical field of soil fertilizer synergistic enhancement, and specifically relates to a method and application of biochar as a composite nitrogen fertilizer synergist. Background Art

[0002] Nitrification inhibitors refer to a class of chemical or natural biological agents that can inhibit the conversion of ammonium nitrogen to nitrate nitrogen. They can reduce the loss of nitrogen fertilizer in the form of nitrate nitrogen and the impact on the ecological environment, and are particularly widely used in agricultural production. However, inhibitors are easily inactivated by adsorption by soil organic matter and minerals, and can be quickly degraded by soil microorganisms, resulting in a short effective action time, which significantly affects the efficiency of the inhibitor. The most widely used 3,4-dimethylpyrazole phosphate (DMPP) today only maintains an optimal inhibitory effect for 14-21 days and cannot continuously regulate nitrogen conversion and loss during the crop growth cycle. Prolonging the effective action time of DMPP in the soil is a difficult problem that needs to be solved in practical applications.

[0003] In recent years, some scholars have tried to develop new functional materials by modifying the active groups of inhibitors to improve the stability of inhibitors from the molecular structure; or use microencapsulation technology to encapsulate inhibitors to block direct contact between inhibitors and soil, and release them again through sustained release. Although the above methods can theoretically prolong the duration of inhibition, most of them are still in the exploratory research stage due to the high cost of developing new compounds, the complex microcapsule preparation process, and the difficulty in ensuring the effect. Summary of the invention

[0004] In view of this, the object of the present invention is to provide a method and application of biochar as a composite nitrogen fertilizer synergist.

[0005] In order to achieve the above object, the present invention provides the following technical solutions:

[0006] The present invention provides a method for using biochar as a composite nitrogen fertilizer synergist, comprising the following steps:

[0007] S1, biochar prepared by oxygen-limited temperature-controlled carbonization method using corn stalks as raw materials;

[0008] S2, dissolving solid 3,4-dimethylpyrazole phosphate in an aqueous solution to wet the surface thereof;

[0009] S3, removing ash from the biochar;

[0010] S4. The soaked 3,4-dimethylpyrazole phosphate and the ash-removed biochar are placed in a centrifuge for centrifugal adsorption, so that the DMPP small molecules are temporarily stored in the pore structure of the biochar.

[0011] Furthermore, in step S2, the biochar ash removal step is:

[0012] P1. The biochar prepared in step S1 is placed in an HCl solution for treatment and centrifugation, and then filtered with a PTFE membrane to remove the supernatant in the HCl solution after centrifugation;

[0013] P2, the biochar sample was further treated with HCl-HF mixed solution, then centrifuged and filtered;

[0014] P3. Wash the sample with deionized water to remove residual acid, silicon and soluble salts until the pH of the supernatant remains unchanged;

[0015] P4. Dry the treated biochar in an oven at 80°C for 12 h.

[0016] Furthermore, any of the biochars described above is used as a composite nitrogen fertilizer synergist in soil fertilizer.

[0017] The beneficial effects of the present invention are:

[0018] 1. In the present invention, compared with the treatment of single DMPP application, the degradation period of DMPP treatment combined with biochar in soil was extended by 10-21 days. This characteristic of biochar indicates that it can be used as a potential DMPP slow-release carrier, which helps to prolong its effectiveness as a nitrogen fertilizer inhibitor.

[0019] 2. In the present invention, DMPP is centrifugally adsorbed through the pore structure inside the small biochar particles. The DMPP small molecules are temporarily stored in the pore structure of the biochar, so that they are slowly released when applied to the soil, effectively slowing down the degradation rate of DMPP, thereby extending its residence time in the soil to maintain its effectiveness.

[0020] 3. In the present invention, the effect of biochar on the residual level of DMPP also reflects its adsorption capacity and the existence of physical and chemical adsorption, which to a certain extent slows down the rate of degradation by microorganisms and reduces the leaching of inhibitors.

[0021] 4. In the present invention, the pore structure of biochar provides a large number of adsorption sites for DMPP molecules, and the chemical functional groups on its surface may form stable interactions with DMPP molecules, thereby enhancing its stability and slow-release ability in the soil. Based on the above experimental research, it can be confirmed that biochar has the potential to serve as a "protective agent".

[0022] Other advantages, objectives and features of the present invention will be described in the following description and will be apparent to those skilled in the art to some extent, or those skilled in the art may be taught from the practice of the present invention. The objectives and other advantages of the present invention may be realized and obtained through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to make the purpose, technical solution and beneficial effects of the invention clearer, the present invention provides the following drawings for illustration:

[0024] Figure 1 The residual dynamics of DMPP in the soil after the application of different types of biochar in the present invention;

[0025] Figure 2 This is a kinetic curve diagram of DMPP adsorption and desorption by biochar of the present invention;

[0026] Figure 3 The thermodynamic curve diagram of DMPP adsorption and desorption of biochar of the present invention;

[0027] Figure 4 This is the change of the functional groups on the surface of biochar at different pyrolysis temperatures before and after adsorption and desorption in the present invention. DETAILED DESCRIPTION

[0028] The DMPP in the present invention is: 3,4-dimethylpyrazole phosphate.

[0029] A method for using biochar as a composite nitrogen fertilizer synergist.

[0030] Example 1

[0031] S1. Using corn straw as raw material, biochar with pyrolysis temperatures of 300°C, 500°C, and 700°C was prepared by oxygen-limited temperature-controlled carbonization method, while removing ash;

[0032] The method for removing ash from biochar is as follows: treating biochar at pyrolysis temperatures of 300° C., 500° C., and 700° C. in an HCl solution for 4 h and centrifuging the solution, and then filtering the solution with a 0.45 μm PTFE membrane to remove the supernatant;

[0033] The biochar samples were treated with HCl-HF mixed solution, centrifuged and filtered;

[0034] The samples were then washed with deionized water to remove residual acid, silicon, and soluble salts until the pH of the supernatant remained unchanged;

[0035] The treated biochar was oven-dried at 80 °C for 12 h and weighed, which was repeated four times. The three types of deashed biochars after treatment were recorded as RBC300, RBC500, and RBC700;

[0036] S2. Wrap the deashed biochar on the outer surface of DMPP.

[0037] verify:

[0038] 1. The basic properties of biochar were characterized by using electron microscope scanner, X-ray diffractometer, elemental analyzer, specific surface area analyzer, Fourier transform infrared spectrometer and other equipment. The functional groups, specific surface area, pore structure, carbonization degree, cation exchange capacity, aromaticity and hydrophobicity of biochar at different pyrolysis temperatures were compared and analyzed, and the adsorption characteristics of different biochars for DMPP were discussed and evaluated.

[0039] Table 1: Changes in specific surface area, pore volume, pore size, cation exchange capacity, carbon-nitrogen ratio and carboxyl content of biochar before and after adsorption and desorption

[0040]

[0041] 2. In order to obtain the relationship between different adsorption-desorption times and the corresponding equilibrium adsorption-desorption amounts, the pseudo-first-order kinetics, pseudo-second-order kinetics model, Elovich equation and intra-particle diffusion equation are used to clarify whether the dominant adsorption effect is physical adsorption or chemical adsorption, and to determine the optimal adsorption-desorption time. The adsorption-desorption kinetics test is carried out through batch equilibrium adsorption test:

[0042] P1. Prepare 3,4-dimethylpyrazole phosphate with pure water to make 1 g L -1 Concentration of mixed solution;

[0043] P2. Place 50 mL of the prepared mixed solution and 0.1000 g of biochar in a centrifuge tube for oscillation. Keep the test temperature constant (25°C). Centrifuge after 30 min, 1 h, 3 h, 6 h, 12 h, 24 h and 48 h of oscillation. Take the supernatant and determine the DMPP content at different time periods.

[0044] P3. After the adsorption test is completed, the supernatant is discarded, and 50 mL of pure water (without 3,4-dimethylpyrazole phosphate) is added to the centrifuge tube for oscillation. The sampling time is 24 hours, and the sampling is repeated three times. After centrifugation, the supernatant is taken to determine the DMPP concentration.

[0045] Figure 2 Kinetic curves of DMPP adsorption and desorption by biochar; a, b are the adsorption and desorption curves of the pseudo-second-order kinetic equation, respectively; c, d are Elovich, respectively.

[0046] In order to obtain the relationship curve between different concentrations and the corresponding equilibrium adsorption-desorption amount, the Freundlich isotherm adsorption equation and the Langmuir model were used for fitting (the Freundlich model is mainly applicable to adsorbents with uneven surfaces, and it is believed that the adsorption between the adsorbed molecules and the adsorbent is multi-layer non-uniform adsorption. When the adsorption kinetic parameter n>1, it belongs to the L-type adsorption isotherm curve of surface monolayer adsorption); (the Langmuir model is mainly used to describe the monolayer adsorption process of the adsorbate on the adsorbent surface. It is believed that the adsorption energy of each molecule is the same and has nothing to do with its coverage on the adsorbate surface. The adsorption of organic matter only occurs at a fixed position of the adsorbent and there is no interaction between the adsorbates). Adsorption and desorption thermodynamic experiments were also carried out:

[0047] P1. The optimal adsorption and desorption time is determined by batch constant temperature oscillation adsorption method combined with the adsorption-desorption kinetics experimental results:

[0048] P2. Prepare 3,4-dimethylpyrazole phosphate into 7 concentrations (50, 100, 250, 500, 1000, 1500 and 2000 mg L -1 ) gradient sequence of solutions;

[0049] P3, pure water (50 mL) and 0.1000 g of biochar were placed in a centrifuge tube, shaken at 25 °C for the optimal time, and then centrifuged. The supernatant was extracted and the concentration of 3,4-dimethylpyrazole phosphate was determined;

[0050] P4. After the adsorption test, discard the supernatant, add 50 mL of pure water to the centrifuge tube, continue to oscillate for 24 hours, then centrifuge, extract the supernatant and determine the concentration of 3,4-dimethylpyrazole phosphate.

[0051] Figure 3 Thermodynamic curves of DMPP adsorption and desorption on biochar; a and b are the adsorption and desorption curves of Freundlich model, respectively; c and d are the adsorption and desorption curves of Langmuir model, respectively.

[0052] Summarize:

[0053] The present invention explores the adsorption-desorption characteristics of biochar on DMPP; based on pseudo-first-order and pseudo-second-order adsorption kinetic models, the adsorption kinetic mechanism of biochar on DMPP is analyzed, and according to the Langmuir, Freundlich and Temkin adsorption isotherm models, the isothermal adsorption characteristics (such as single-layer adsorption process, multi-layer heterogeneous adsorption process or electrostatic adsorption process) are clarified:

[0054] In the present invention, the adsorption process of DMPP on the biochar surface is significantly limited by the availability of adsorption sites, and the reaction slows down as the surface sites are saturated. The reaction conforms to the core assumption of the pseudo-second-order kinetic model, that is, the adsorption rate is proportional to the square of the number of unoccupied sites on the biochar surface. This high degree of conformity also emphasizes the strong chemical interactions between biochar and DMPP, such as chemical bonding, charge transfer, etc. At the same time, the applicability of the Elovich model reveals the complexity of the adsorption process, especially in the early stage of adsorption, reflecting the heterogeneity of the energy distribution of the adsorption sites on the biochar surface and the nonlinear decrease of the adsorption rate over time, emphasizing the key role of the physical properties of biochar (such as porosity and surface heterogeneity) and the chemical forces between it and DMPP in driving the adsorption process.

[0055] Finally, it should be noted that the above preferred embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail through the above preferred embodiments, those skilled in the art should understand that various changes can be made in form and details without departing from the scope defined by the claims of the present invention.

Claims

1. A method for using biochar as a composite nitrogen fertilizer synergist, characterized in that: The following steps are included: S1, biochar prepared by oxygen-limited temperature-controlled carbonization method using corn stalks as raw materials; S2, dissolving solid 3,4-dimethylpyrazole phosphate in an aqueous solution to wet the surface thereof; S3, removing ash from the biochar; S4. The soaked 3,4-dimethylpyrazole phosphate and the ash-removed biochar are placed in a centrifuge for centrifugal adsorption, so that the DMPP small molecules are temporarily stored in the pore structure of the biochar.

2. The method of using biochar as a composite nitrogen fertilizer synergist according to claim 1, characterized in that: In step S2, the biochar ash removal step is: P1. The biochar prepared in step S1 is placed in an HCl solution for treatment and centrifugation, and then filtered with a PTFE membrane to remove the supernatant in the HCl solution after centrifugation; P2, the biochar sample was further treated with HCl-HF mixed solution, then centrifuged and filtered; P3. Wash the sample with deionized water to remove residual acid, silicon and soluble salts until the pH of the supernatant remains unchanged; P4. Dry the treated biochar in an oven at 80°C for 12 h.

3. The biochar according to any one of claims 1-2 is used as a composite nitrogen fertilizer synergist in soil fertilizer.

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