Nitrogen-rich biochar material as well as preparation method and application thereof

Abstract

The invention provides a nitrogen-rich biochar material as well as a preparation method and application thereof, and belongs to the technical field of soil nutrient synergism. Comprising the following steps: S1, cleaning, drying, crushing and sieving wheat straws to obtain wheat straw powder for later use; s2, heating and carbonizing the wheat straw powder to obtain wheat straw charcoal; s3, preparing urea into a solution, adding the modified starch, and stirring to obtain a mixed solution; s4, adding the wheat straw biochar into the mixed solution, heating and stirring, and after the solution is cooled, settling and filtering to obtain a nitrogen-rich biochar-based material; s5, the nitrogen-rich biochar material is purified with absolute ethyl alcohol, washed with deionized water and dried, the nitrogen-rich biochar material is obtained, the fertility of the sandy soil is improved, and meanwhile the nutrient content and the nutrient utilization efficiency of the soil are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of soil nutrient enhancement, and specifically relates to a nitrogen-rich biochar material, a preparation method thereof, and an application thereof. Background Art

[0002] Nitrogen (N) is one of the essential nutrient elements for plant growth and is particularly important in sandy soils. Nitrogen is a key limiting factor for plant growth in sandy soils, but its efficient utilization faces major challenges. Due to its physical properties (such as large particles, many pores, and poor water and fertilizer retention capacity), nitrogen in sandy soils is easily lost or difficult to maintain effectiveness, resulting in low plant utilization efficiency. And sandy soil, as one of the soil types with the largest area in cultivated land, plays a very important role in food production and security. Therefore, how to improve the fertility and nitrogen availability of sandy soil is very important.

[0003] Selecting agricultural waste wheat straw as the raw material for nitrogen-rich biochar-based materials has always been the research priority in the field of sandy soil treatment because wheat straw is widely available, almost cost-free, and very friendly to the environment. Biochar is a carbon-rich solid product made from various agricultural waste biomasses through high-temperature anaerobic pyrolysis, with a porous structure, a high specific surface area, and various oxygen-containing functional groups. Therefore, it is widely used in the treatment of sandy soil. However, due to the limitations of biochar itself, its porous structure and large specific surface area may accelerate nutrient loss, restricting the application of biochar in sandy soil. In order to improve the nutrient efficiency of biochar in soil, make it more effective and applicable, enrichment modification treatment is carried out on biochar to prepare nitrogen-rich biochar-based materials, increasing the nutrient retention capacity of biochar and enhancing soil fertility.

[0004] Therefore, in the treatment of sandy soil, providing a nitrogen-rich biochar-based material that can increase soil fertility, improve soil structure, and is easy to prepare and low in cost is a technical problem that researchers in this field urgently need to solve. Summary of the Invention

[0005] The purpose of the present invention is to provide a nitrogen-rich biochar material, a preparation method thereof, and an application thereof. Based on biochar, the biochar is prepared into a nitrogen-rich biochar material through an enrichment method, realizing the improvement of the fertility of sandy soil, while increasing the nutrient content and nutrient utilization efficiency of the soil. The present invention has the advantages of simple preparation, high nutrient utilization rate, and environmental friendliness.

[0006] The technical solution of the present invention is realized as follows: The present invention provides a preparation method of a nitrogen-rich biochar material, including the following steps: S1. Wash, dry, crush, and sieve wheat straw to obtain wheat straw powder for standby; S2. Heat the wheat straw powder for carbonization to obtain wheat straw biochar; S3. Prepare a solution of urea, add modified starch, and stir to obtain a mixed solution; S4. Add the wheat straw biochar to the mixed solution, heat and stir. After the solution cools, sediment and filter to obtain a nitrogen-rich biochar-based material; S5. Purify the nitrogen-rich biochar material with absolute ethanol, wash it with deionized water, and dry it to obtain the nitrogen-rich biochar material.

[0007] As a further improvement of the present invention, the drying temperature in step S1 is 55 - 65 °C, and the mesh number of the sieve for sieving is 50 - 100 meshes.

[0008] As a further improvement of the present invention, the conditions for the heating carbonization in step S2 are heating to 550 - 650 °C at a heating rate of 10 - 20 °C / min in a nitrogen atmosphere and maintaining a constant temperature for 1 - 3 h.

[0009] As a further improvement of the present invention, the mass ratio of urea to modified starch in step S3 is as follows. Low: 8.69 g, 26 mL of deionized water, ratio 1:3; Medium: 17.3 g of urea, 52 mL of deionized water; High: 26.08 g of urea, 78.5 mL of deionized water (the ratio of urea to water is 1:3). Fix 100 g of biochar.) As a further improvement of the present invention, the solid-liquid ratio of the wheat straw biochar to the mixed solution in step S4 is (the fixed addition amount of biochar is 100 g).

[0010] As a further improvement of the present invention, the heating and stirring temperature in step S4 is 90 - 100 °C, and the time is 30 - 50 min.

[0011] As a further improvement of the present invention, the purification time in step S5 is 10 - 14 h, the drying temperature is 55 - 65 °C, and the time is 20 - 28 h.

[0012] The present invention further protects a nitrogen-rich biochar material prepared by the above preparation method.

[0013] The present invention further protects the application of the above nitrogen-rich biochar material in enhancing soil nutrients.

[0014] The present invention has the following beneficial effects: The nitrogen-rich biochar material prepared by the present invention is prepared by enriching biochar on the basis of biochar to obtain a nitrogen-rich biochar material, which realizes the improvement of the fertility of sandy soil, and at the same time improves the nutrient content and nutrient utilization efficiency of the soil. The present invention has the advantages of simple preparation, high nutrient utilization rate and environmental friendliness. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0016] Figure 1 It is the scanning electron microscope image of the nitrogen-rich biochar material in the present invention; Figure 2 It is the Fourier transform infrared spectrum schematic diagram of the nitrogen-rich biochar material in the present invention; Figure 3 It is the effect diagram of the influence of the nitrogen-rich biochar material on the total nitrogen of sandy soil in the present invention; Figure 4 It is the effect diagram of the influence of the nitrogen-rich biochar material on the available potassium of sandy soil in the present invention; Figure 5 It is the effect diagram of the influence of the nitrogen-rich biochar material on the available phosphorus of sandy soil in the present invention; Figure 6 It is the effect diagram of the influence of the nitrogen-rich biochar material on the total organic matter of sandy soil in the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0017] The following will clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0018] Example 1 This embodiment provides a preparation method of a nitrogen-rich biochar material, including the following steps (1) Wash wheat straw, place it in an oven at 60 °C for drying, and crush it into powder by a pulverizer, and pass through a 80-mesh sieve to obtain wheat straw powder for standby; (2) Put the selected wheat straw powder into a tubular muffle furnace, heat and carbonize it under the protection of nitrogen, heat it to 600 °C at a heating rate of 15 °C / min, and keep it warm for 2 h to obtain wheat straw biochar; (3)Prepare urea solutions with low, medium, and high concentrations (low: 8.69 g of urea, 26 mL of deionized water, ratio of 1:3; medium: 17.3 g of urea, 52 mL of deionized water; high: 26.08 g of urea, 78.5 mL of deionized water (ratio of urea to water is 1:3). [2] Fix 100 g of biochar.) Add modified starch to each solution, set the rotation speed to 600 r / min, and stir rapidly; (4)Slowly add the obtained wheat straw biochar to the mixed solution in step (3), heat up to 100 °C, keep it at a constant temperature for 40 min. After the solution cools down, wait until the nitrogen-rich biochar material settles, and filter out the settled nitrogen-rich biochar material; (5)Purify the nitrogen-rich biochar material with absolute ethanol for 12 h, wash it with deionized water, and dry it in an oven at 60 °C for 24 h. Finally, obtain the nitrogen-rich biochar material, which is NB1.

[0019] Example 2 This example provides a preparation method of a nitrogen-rich biochar material, including the following steps (1)Wash the wheat straw, dry it in an oven at 55 °C, and crush it into powder through a pulverizer. Pass it through a 50-mesh sieve to obtain wheat straw powder for standby; (2)Put the selected wheat straw powder into a tubular muffle furnace, heat it up and carbonize it under the protection of nitrogen. Heat it to 550 °C at a heating rate of 10 °C / min and keep it at a constant temperature for 1 h to obtain wheat straw biochar; (3)Add modified starch to urea solutions with low, medium, and high concentrations respectively, set the rotation speed to 600 r / min, and stir rapidly; (4)Slowly add the obtained wheat straw biochar to the mixed solution in step (3), heat up to 90 °C, keep it at a constant temperature for 30 min. After the solution cools down, wait until the nitrogen-rich biochar material settles, and filter out the settled nitrogen-rich biochar material; (5)Purify the nitrogen-rich biochar material with absolute ethanol for 10 h, wash it with deionized water, and dry it in an oven at 55 °C for 20 h. Finally, obtain the nitrogen-rich biochar material, recorded as NB2.

[0020] Example 3 This example provides a preparation method of a nitrogen-rich biochar material, including the following steps (1)Wash the wheat straw, dry it in an oven at 65 °C, and crush it into powder through a pulverizer. Pass it through a 100-mesh sieve to obtain wheat straw powder for standby; (2) Put the selected wheat straw powder into a tubular muffle furnace, heat it for carbonization under the protection of nitrogen, heat it up at a heating rate of 20 °C / min to 650 °C, and keep it warm for 3 h to obtain wheat straw biochar (PB); (3) Prepare urea solutions with low, medium, and high concentrations (low: 8.69 g of urea, 26 mL of deionized water, ratio of 1:3; medium: 17.3 g of urea, 52 mL of deionized water; high: 26.08 g of urea, 78.5 mL of deionized water (the ratio of urea to water is 1:3). Fix 100 g of biochar.) Add modified starch to each solution respectively, set the rotation speed to 600 r / min, and stir rapidly; (4) Slowly add the obtained wheat straw biochar to the mixed solution in step (3), heat up to 95 °C, keep it at a constant temperature for 50 min. After the solution cools down, wait until the nitrogen-rich biochar material settles, and filter out the settled nitrogen-rich biochar material; (5) Purify the nitrogen-rich biochar material with absolute ethanol for 14 h, wash it with deionized water, and dry it in an oven at 65 °C for 28 h. Finally, obtain the nitrogen-rich biochar material, which is NB3.

[0021] Test Example 1 Perform performance tests on the nitrogen-rich biochar materials prepared in Examples 1-3, and the results are shown in Table 1.

[0022] Table 1

[0023] Test Example 2 Perform SEM and infrared tests on the nitrogen-rich biochar materials prepared in Examples 1-3, and the results are shown in Figure 2 and Figure 3 . It can be seen from Figure 1 that PB (raw wheat straw biochar) has a highly porous structure with distinct pores, forming interconnected and complex pores with a rough surface ( Figure 1 a). NB1 shows a similar porous structure, but compared with PB, there are obvious changes on the surface, the pores are uneven, and some pores are blocked or filled, indicating that the nitrogen in urea is adsorbed and enriched on the surface and in the pores of the biochar during the impregnation process ( Figure 1 b). As the urea content increases, the nitrogen content increases accordingly, and the porosity of the biochar gradually decreases. The porosities of NB2 and NB3 are significantly lower than those of PB and NB1 ( Figure 1 c, d), and the surface texture of the biochar becomes rougher, which may be due to the chemical interactions that occur during the enrichment of nitrogen in the biochar. In addition, NB2 and NB3 show higher density and fewer macropores.

[0024] FTIR spectrum (Figure 2 showed that compared with PB, the intensities of the NB spectrum increased at both higher and lower wavenumbers. In the higher wavenumber range (2500 - 4000 cm −1 ), NB had stronger N-H (amine group) peak intensity, especially at 3463 cm −1 , which was more significant than that of PB. Meanwhile, the peaks at 1633 cm −1 and 1667 cm −1 might correspond to carbonyl (C═O) and amide (C═N) respectively. The peak at 1456 cm −1 might be related to the N-H deformation vibration, indicating the presence of amine or amide groups in this peak. It can be seen that the N content in NB was significantly higher than that in PB, which proved that the N in urea was significantly enriched in biochar. In addition, the FTIR spectrum of PB in the range of 1000 - 1100 cm −1 showed C-O stretching vibration, indicating that it contained more carbohydrates or polysaccharides than NB.

[0025] Test Example 1 explored the effects on nutrients in sandy soil At 26 °C, PB (PB is the original biochar of wheat straw), NB1, NB2 and NB3 biochars were applied at two different application rates: 20 t / ha (L1: equivalent to 0.77% of the soil weight) and 40 t / ha (L2: equivalent to 1.54% of the soil weight) to the soil and continuously cultured for 150 days. After the cultivation was completed, the air-dried soil samples were analyzed for total nitrogen, available potassium, available phosphorus and soil organic matter, as Figure 3 , Figure 4 , Figure 5 and Figure 6 shown.

[0026] When applying 20 t / ha, the total nitrogen in the soils of NB1, NB2 and NB3 increased by 8.34%, 8.34% and 20.84% respectively; the available potassium in the soils increased by 112.79%, 95.41% and 87.63% respectively; the available phosphorus in the soils increased by 90.22%, 69.57% and 113.59% respectively; the total soil organic matter increased by 87.50%, 28.57% and 32.33% respectively.

[0027] When applying 40 t / ha, the total nitrogen in the soils of NB1, NB2 and NB increased by 12.5%, 12.5% and 20.84% respectively; the available potassium in the soils increased by 297.18%, 200.61% and 186.50% respectively; the available phosphorus in the soils increased by 155.98%, 144.03% and 122.83% respectively; the total soil organic matter increased by 34.16%, 41.35% and 48.55% respectively.

[0028] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for preparing nitrogen-rich biochar material, characterized in that: The following steps are involved: S1. Wash, dry, crush and sieve the wheat straw to obtain wheat straw powder for later use; S2. heating and carbonizing the wheat straw powder to obtain wheat straw biochar (PB original wheat straw biochar); S3. The urea solution was prepared, modified starch was added, and stirred to obtain a mixed solution; S4. adding wheat straw biochar to the mixed solution, heating and stirring, cooling the solution, settling, filtering, and obtaining a nitrogen-rich biochar-based material; S5. Purify the nitrogen-rich biochar material with anhydrous ethanol, wash it with deionized water, and dry it to obtain the nitrogen-rich biochar material.

2. The preparation method according to claim 1, characterized in that: The drying temperature in step S1 is 55-65° C., and the mesh size of the sieving screen is 50-100 meshes.

3. The preparation method according to claim 1, characterized in that: The heating and carbonization conditions in step S2 are to heat to 550-650° C. at a heating rate of 10-20° C. / min under a nitrogen atmosphere and maintain a constant temperature for 1-3 h.

4. The preparation method according to claim 1, characterized in that: The mass ratio of urea to modified starch in step S3 is (0.7 g modified starch: 30 mL urea mixed solution).

5. The preparation method according to claim 1, characterized in that: The solid-to-liquid ratio of the wheat straw biochar and the mixed solution in step S4 is (biochar fixed at 100 g).

6. The preparation method according to claim 1, characterized in that: The heating and stirring in step S4 is performed at a temperature of 90-100° C. and for a time of 30-50 min.

7. The preparation method according to claim 1, characterized in that: The purification time in step S5 is 10-14 h, and the drying temperature is 55-65° C. for 20-28 h.

8. A nitrogen-rich biochar material obtained by the preparation method according to any one of claims 1 to 7.

9. Use of the nitrogen-rich biochar material as claimed in claim 8 in enhancing soil nutrient efficiency.

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