Modified vinasse biochar-based nitrogen fertilizer as well as preparation method and application thereof

Abstract

The invention discloses a modified vinasse biochar-based nitrogen fertilizer and a preparation method and application thereof, and the preparation method comprises the following steps: (1) drying and crushing vinasse to obtain vinasse particles; (2) mixing and dipping the vinasse particles and a phosphoric acid solution, and then drying to obtain modified vinasse; (3) under a protective atmosphere, pyrolyzing the modified vinasse to obtain modified charcoal; (4) adding an ammonium chloride solution into the modified biochar, adjusting the pH value, heating and oscillating, then taking out the modified biochar after adsorption, and drying to obtain the modified vinasse biochar-based nitrogen fertilizer. The prepared modified vinasse biochar-based nitrogen fertilizer is applied to the field of chemical fertilizer preparation, resource utilization of a wine brewing byproduct vinasse is achieved, the risk of environmental pollution is reduced, the vinasse is made into the biochar-loaded nitrogen fertilizer, technical reference is provided for effective utilization of the nitrogen fertilizer, and the modified vinasse biochar-based nitrogen fertilizer has practical significance in promotion of industrial green cycle development.

Description

Technical Field

[0001] The present invention relates to the technical field of fertilizers, and particularly to a modified distiller's grains biochar-based nitrogen fertilizer and its preparation method and application. Background Art

[0002] Fertilization is an effective measure to improve the yield and quality of crops per unit area of land. However, conventional chemical fertilizers have too fast an effect, making it difficult for crops to absorb and utilize them efficiently in a timely manner. Environmental problems such as soil acidification erosion and groundwater pollution caused thereby have attracted wide attention. How to achieve slow release of fertilizer nutrients, meet the dynamic fertilizer demand characteristics of crops, and produce a slow-release fertilizer with low cost and high utilization efficiency is extremely urgent.

[0003] Distiller's grains are a large amount of solid waste in the brewing industry. Traditional treatment methods such as landfill and incineration are likely to cause environmental pollution. Distiller's grains contain a large amount of organic substances such as cellulose, hemicellulose, lignin, and protein. These components make it an ideal raw material for preparing high-quality biochar. By preparing distiller's grains into biochar, the waste is transformed into valuable resources, realizing the efficient recycling of resources and reducing environmental pollution.

[0004] Biochar is a carbon-rich substance formed by pyrolysis of biomass waste in an anoxic or oxygen-limited environment. However, the pore structure of raw biochar is not developed enough, the distribution of surface functional groups is not reasonable enough, and the ash composition is not functionalized enough; in addition, the high-temperature pyrolysis process will reduce the number of functional groups of biochar and reduce its adsorption performance. Given the limitations of raw biochar, it is necessary to improve its performance through modification. Currently, the main modification methods for biochar are impregnation modification. Impregnation modification forms a more developed microporous and mesoporous structure by filling and expanding the original pores, providing more adsorption sites, thereby improving the adsorption efficiency of biochar. In addition, through modification, the physicochemical properties of biochar can also be optimized, such as adjusting the crystal structure, increasing the specific surface area, improving the pore structure, and changing the surface charge properties of biochar, enhancing the electrostatic interaction between biochar and pollutants, thereby improving the adsorption efficiency.

[0005] Based on the fact that the impregnation modification of the above-mentioned biochar can improve its adsorption performance, it can be considered to use biochar as the carrier of slow-release fertilizer to make carbon-based inorganic fertilizer to achieve the long-term slow-release effect of water and fertilizer. However, when unmodified biochar is actually applied to inorganic fertilizer, it is found that its slow-release performance does not reach the ideal effect. Summary of the Invention

[0006] The purpose of the present invention is to provide a modified distiller's grains biochar-based nitrogen fertilizer and its preparation method and application to solve the problem that the slow-release performance of fertilizer does not reach the ideal effect during the preparation of inorganic fertilizer by directly pyrolyzing the distiller's grains to prepare biochar.

[0007] To achieve the above object, a first aspect of the present invention provides a method for preparing a modified distiller's grains biochar-based nitrogen fertilizer, comprising the following steps:

[0008] (1) Dry and crush the distiller's grains to obtain distiller's grains particles;

[0009] (2) Mix and impregnate the distiller's grains particles with a phosphoric acid solution, and then dry them to obtain modified distiller's grains;

[0010] (3) Pyrolyze the modified distiller's grains under a protective atmosphere to obtain modified biochar;

[0011] (4) Add an ammonium chloride solution to the modified biochar, adjust the pH value, heat and shake, and then take out the modified biochar after adsorption is completed and dry it to obtain the modified distiller's grains biochar-based nitrogen fertilizer.

[0012] Based on the problem that the adsorption performance of the biochar directly obtained by pyrolyzing and carbonizing distiller's grains in the prior art is insufficient, in the present invention, the distiller's grains are first impregnated and mixed with a phosphoric acid solution, and then pyrolyzed and carbonized to obtain modified biochar with high adsorption performance. From the process of phosphoric acid impregnation activation, the content and dispersion state of phosphoric acid play a decisive role in the pore development degree and pore size distribution of biochar. During the carbonization process, the phosphoric acid molecular aggregates provide a site for the deposition of newly generated carbon atoms produced by the precursor. Therefore, within a certain range, the larger the amount of phosphoric acid or the impregnation ratio, the more developed the pore structure of biochar. In addition, during the heat treatment of phosphoric acid-distiller's grains, phosphoric acid can undergo an obvious cross-linking reaction with biopolymers. The three hydroxyl groups of phosphoric acid can condense with the hydroxyl groups in the high polysaccharides in the distiller's grains and their degradation products to form phosphate ester bonds, and its cross-linking degree has a very high correlation with the development of micropores in activated carbon. The development of the pore structure of biochar further promotes the improvement of the adsorption performance of biochar. The modified biochar has a rich pore structure and a high specific surface area, which endows it with a strong adsorption capacity.

[0013] When the nitrogen fertilizer is combined with the modified biochar, nitrogen can be fixed in the pores of the biochar through physical adsorption and chemical reactions, thus greatly reducing nitrogen loss caused by leaching, volatilization, etc. Such physical adsorption and chemical reactions include electrostatic adsorption, pore adsorption, cation-π bond, ion exchange and other action mechanisms. This mechanism ensures that more nitrogen can remain in the soil for long-term use by plants. The stability of biochar enables the fixed nitrogen to be slowly released, extending the fertilizer efficiency period, which means that plants can obtain a stable nitrogen supply for a longer time. Especially in the later stage of the growth season when the efficacy of traditional nitrogen fertilizers weakens, this delayed release effect improves the overall utilization efficiency of nitrogen fertilizers.

[0014] Preferably, in step (1), the temperature during drying of the distiller's grains should not be too high, generally 50°C.

[0015] Preferably, in step (1), the distillers' grains are crushed to 0.15 - 0.35 mm.

[0016] Preferably, in step (2), the concentration of the phosphoric acid solution is 1 - 3 mol / L, and the mass - to - volume ratio of the distillers' grains particles to the phosphoric acid solution is 5 - 15 g: 150 - 250 mL.

[0017] Preferably, in step (2), the impregnation temperature is 60 - 80 °C, and the impregnation time is 24 - 48 h.

[0018] Preferably, in step (3), the heating rate is 4 - 10 °C / min, the pyrolysis temperature is 550 - 850 °C, and the constant - temperature time is 60 - 120 min.

[0019] Preferably, in step (4), the concentration of the ammonium chloride solution is 2000 - 4000 mg / L, and the mass - to - volume ratio of the modified biochar to the ammonium chloride solution is 0.05 - 0.15 g: 100 mL.

[0020] Preferably, in step (4), the pH value is adjusted to 3 - 11, the heating temperature is 25 - 65 °C, and the oscillation time is 5 - 10 h.

[0021] The second aspect of the present invention provides a modified distillers' grains biochar - based nitrogen fertilizer, which is prepared by the above - mentioned preparation method.

[0022] The third aspect of the present invention provides the application of the modified distillers' grains biochar - based nitrogen fertilizer, that is, the application of the modified distillers' grains biochar - based nitrogen fertilizer in lettuce cultivation.

[0023] Preferably, lettuce seedlings with consistent growth vigor are transplanted and planted. Phosphate fertilizer and potassium fertilizer are applied into the soil at one time as base fertilizers before lettuce planting. After lettuce planting, the modified distillers' grains biochar - based nitrogen fertilizer is added to the lettuce soil, and the physiological - related indexes of lettuce growth are measured every 3 days after planting.

[0024] Therefore, the modified distillers' grains biochar - based nitrogen fertilizer with the above - mentioned structure, its preparation method and application of the present invention have the following beneficial effects:

[0025] 1. The present invention uses the by - product distillers' grains of brewing as raw materials. Its source is wide. While saving costs, it can effectively reduce the accumulation problem caused by its unreasonable utilization, realizing the resource utilization of waste biomass. In addition, after the fertilizer is used up, the biochar remains in the soil, which can increase the soil organic carbon content, improve the soil structure, promote the formation of soil aggregates, and increase the content of aromatic compounds in coarse aggregates.

[0026] 2. Compared with other modification methods, the present invention uses a phosphoric acid solution to impregnate and modify distiller's grains particles, improving the pore structure of the biochar material, increasing the specific surface area, enriching the functional groups on the biochar surface, overcoming the disadvantages of traditional biochar materials mainly relying on physical adsorption and having a low ammonia nitrogen adsorption capacity, and enhancing the ammonia nitrogen adsorption performance of the biochar. The present invention also optimizes the factors affecting the loading effect, and selects the optimal solution concentration, solution pH and solution temperature through experiments, which enables the modified distiller's grains biochar to have a higher ammonia nitrogen adsorption capacity and achieve a better slow-release effect.

[0027] The technical solution of the present invention will be further described in detail below through the drawings and embodiments. Description of the Drawings

[0028] Figure 1 SEM image of the modified distiller's grains biochar-based nitrogen fertilizer prepared in Example 1. Detailed Embodiments

[0029] The present invention will be further described below. It should be noted that this embodiment is based on the present technical solution and gives detailed implementation methods and specific operation processes, but the present invention is not limited to this embodiment.

[0030] Example 1

[0031] A preparation method of a modified distiller's grains biochar-based nitrogen fertilizer includes the following steps:

[0032] (1) Naturally air-dry or dry the distiller's grains and then crush them to 0.25 - 0.35 mm to obtain distiller's grains particles, and the drying temperature is 50°C;

[0033] (2) Preparation of the phosphoric acid solution: Put phosphoric acid into a beaker, add an appropriate amount of distilled water, and make up the volume to obtain a 1000 ml 3 mol / L phosphoric acid solution;

[0034] Put 200 mL of the phosphoric acid solution into a conical flask, take 10 g of distiller's grains particles and put them into the conical flask, place the conical flask in an oven for impregnation, the oven temperature (i.e., the impregnation temperature) is 80°C, take it out after 24 h, and then dry it to obtain modified distiller's grains;

[0035] (3) Filter and dry the modified distiller's grains, then place them in a tube furnace for pyrolysis, introduce a protective gas N2, heat at a rate of 7°C / min to the final pyrolysis temperature of 700°C, and keep pyrolyzing continuously at this temperature for 90 min. After pyrolysis is completed, wait for the tube furnace to cool to below 100°C, turn off the tube furnace, take out the quartz boat, collect the solid product, wash the solid product with deionized water until neutral, and dry it at 105°C to obtain a modified biochar material;

[0036] (4) Weigh 0.1 g of the modified biochar into a conical flask, add 100 mL of 2000 mg / L NH4Cl solution, place the conical flask on a water bath shaker at 150 r / min for oscillatory adsorption, adjust the temperature to 25 °C, the pH value of the solution to 7, take out the sample after 360 min for drying to obtain the modified distiller's grains biochar-based nitrogen fertilizer.

[0037] Regarding the adjustment of the distiller's grains particle size, impregnating solution type, impregnating solution concentration, and impregnating temperature in steps (1) and (2) of Example 1, the following Comparative Examples 1-1 to 1-8 are given.

[0038] Comparative Example 1-1

[0039] The difference between this comparative example and Example 1 lies in that the distiller's grains particle size, phosphoric acid solution concentration, and impregnating temperature are different, specifically as follows: the distiller's grains particle size is 0.18 - 0.25 mm, the concentration of the phosphoric acid solution is 2 mol / L, and the impregnating temperature is 60 °C.

[0040] Comparative Example 1-2

[0041] The difference between this comparative example and Example 1 lies in that the distiller's grains particle size, phosphoric acid solution concentration, and impregnating temperature are different, specifically as follows: the distiller's grains particle size is 0.15 - 0.18 mm, the concentration of the phosphoric acid solution is 1 mol / L, and the impregnating temperature is 70 °C.

[0042] Comparative Example 1-3

[0043] The difference between this comparative example and Example 1 lies in that the distiller's grains particle size, impregnating solution type, and impregnating temperature are different, specifically as follows: the distiller's grains particle size is 0.15 - 0.18 mm, the phosphoric acid solution is replaced with a zinc chloride solution, and the impregnating temperature is 60 °C.

[0044] Comparative Example 1-4

[0045] The difference between this comparative example and Example 1 lies in that the distiller's grains particle size, impregnating solution type, and impregnating temperature are different, specifically as follows: the distiller's grains particle size is 0.18 - 0.25 mm, the phosphoric acid solution is replaced with a potassium acetate solution, and the impregnating temperature is 70 °C.

[0046] Comparative Example 1-5

[0047] The difference between this comparative example and Example 1 lies in that the impregnating solution type, concentration, and impregnating temperature are different, specifically as follows: the phosphoric acid solution is replaced with a zinc chloride solution, the concentration of the zinc chloride solution is 2 mol / L, and the impregnating temperature is 70 °C.

[0048] Comparative Example 1-6

[0049] The differences between this comparative example and Example 1 are as follows: the distiller's grains particle size, the type and concentration of the impregnating solution are different, specifically as follows: the distiller's grains particle size is 0.18 - 0.25 mm, the phosphoric acid solution is replaced with a zinc chloride solution, and the concentration of the zinc chloride solution is 2 mol / L.

[0050] Comparative Example 1-7

[0051] The differences between this comparative example and Example 1 are as follows: the type, concentration, and impregnation temperature of the impregnating solution are different, specifically as follows: the phosphoric acid solution is replaced with a potassium acetate solution, the concentration of the potassium acetate solution is 1 mol / L, and the impregnation temperature is 60 °C.

[0052] Comparative Example 1-8

[0053] The differences between this comparative example and Example 1 are as follows: the distiller's grains particle size, the type and concentration of the impregnating solution are different, specifically as follows: the distiller's grains particle size is 0.15 - 0.18 mm, the phosphoric acid solution is replaced with a potassium acetate solution, and the concentration of the potassium acetate solution is 2 mol / L.

[0054] The specific surface areas and adsorption capacities of the modified biochars in Example 1 and Comparative Examples 1-1 to 1-8 are shown in Table 1. The test process for the adsorption capacity is as follows: after the modified biochar completes the adsorption of ammonium chloride in step (4), the concentration of ammonia nitrogen remaining in the solution is measured, and then the ammonia nitrogen adsorption capacity of the modified biochar is calculated by the difference between the initial ammonium chloride concentration and the ammonia nitrogen concentration remaining in the solution.

[0055] Table 1 Specific surface areas and adsorption capacities of the modified biochars in Example 1 and Comparative Examples 1-1 to 1-8

[0056]

[0057] It can be seen from Table 1 that when Example 1 is adopted, that is, a phosphoric acid solution is selected, the solution concentration is 3 mol / L, the distiller's grains particle size is 0.25 - 0.35 mm, and the impregnation temperature is 80 °C, this formulation is the optimal choice. At this time, the modified biochar has the best adsorption effect on the ammonia nitrogen solution and can better provide nutrients for crops.

[0058] The pyrolysis temperature, pyrolysis time, heating rate, and gas type in step (3) of Example 1 are adjusted to give the following Comparative Examples 2-1 to 2-8.

[0059] Comparative Example 2-1

[0060] The differences between this comparative example and Example 1 are as follows: the pyrolysis temperature, pyrolysis time, and heating rate are different, specifically as follows: the pyrolysis temperature is 550 °C, the pyrolysis time is 60 min, and the heating rate is 7 °C / min.

[0061] Comparative Example 2-2

[0062] The difference between this comparative example and Example 1 lies in: different pyrolysis temperatures, pyrolysis times, and heating rates, specifically as follows: the pyrolysis temperature is 850 °C, the pyrolysis time is 120 min, and the heating rate is 10 °C / min.

[0063] Comparative Example 2-3

[0064] The difference between this comparative example and Example 1 lies in: different pyrolysis temperatures, pyrolysis times, and gas types, specifically as follows: the pyrolysis temperature is 550 °C, the pyrolysis time is 120 min, and the protective gas nitrogen is not introduced.

[0065] Comparative Example 2-4

[0066] The difference between this comparative example and Example 1 lies in: different pyrolysis times, heating rates, and gas types, specifically as follows: the pyrolysis time is 60 min, the heating rate is 10 °C / min, and the protective gas nitrogen is not introduced.

[0067] Comparative Example 2-5

[0068] The difference between this comparative example and Example 1 lies in: different pyrolysis temperatures, heating rates, and gas types, specifically as follows: the pyrolysis temperature is 850 °C, the heating rate is 4 °C / min, and the protective gas nitrogen is not introduced.

[0069] Comparative Example 2-6

[0070] The difference between this comparative example and Example 1 lies in: different pyrolysis temperatures, heating rates, and gas types, specifically as follows: the pyrolysis temperature is 550 °C, the heating rate is 10 °C / min, and the protective gas nitrogen is replaced with carbon dioxide.

[0071] Comparative Example 2-7

[0072] The difference between this comparative example and Example 1 lies in: different pyrolysis times, heating rates, and gas types, specifically as follows: the pyrolysis time is 120 min, the heating rate is 4 °C / min, and the protective gas nitrogen is replaced with carbon dioxide.

[0073] Comparative Example 2-8

[0074] The difference between this comparative example and Example 1 lies in: different pyrolysis temperatures, pyrolysis times, and gas types, specifically as follows: the pyrolysis temperature is 550 °C, the pyrolysis time is 60 min, and the protective gas nitrogen is replaced with carbon dioxide.

[0075] The specific surface areas and adsorption capacities of the modified biochars in Example 1 and Comparative Examples 2-1 to 2-8 are shown in Table 2.

[0076] Table 2 Specific surface areas and adsorption capacities of the modified biochars in Example 1 and Comparative Examples 2-1 to 2-8

[0077]

[0078] As can be seen from Table 2, when Example 1 is adopted, that is, the protective gas N2 is introduced, heated to the final pyrolysis temperature of 700 °C at a rate of 7 °C / min, and kept pyrolyzing continuously for 90 min at this temperature, this pyrolysis condition is the optimal choice. At this time, the specific surface area of the modified biochar is relatively high, and the Zeta potential is more conducive to the adsorption of ammonium nitrogen. Finally, the adsorption effect on the ammonia nitrogen solution is the best, and it can better provide nutrients for crops.

[0079] Regarding the adjustment of the solution temperature during the adsorption process in step (4) of Example 1, the following Comparative Examples 3-1 to 3-4 are given.

[0080] Comparative Example 3-1

[0081] The difference between this comparative example and Example 1 is that the solution temperature during the adsorption process is different, and the specific solution temperature is 35 °C.

[0082] Comparative Example 3-2

[0083] The difference between this comparative example and Example 1 is that the solution temperature during the adsorption process is different, and the specific solution temperature is 45 °C.

[0084] Comparative Example 3-3

[0085] The difference between this comparative example and Example 1 is that the solution temperature during the adsorption process is different, and the specific solution temperature is 55 °C.

[0086] Comparative Example 3-4

[0087] The difference between this comparative example and Example 1 is that the solution temperature during the adsorption process is different, and the specific solution temperature is 65 °C.

[0088] The adsorption capacities of the modified biochars in Example 1 and Comparative Examples 3-1 to 3-4 are shown in Table 3.

[0089] Table 3 Adsorption capacities of modified biochars at different temperatures

[0090]

[0091] As can be seen from Table 3, in Example 1, when the solution pH and ammonium chloride concentration are constant, as the solution temperature increases, the ammonia nitrogen adsorption capacity of the modified biochar first increases and then decreases. When the solution temperature is 45 °C, the adsorption capacity is the highest and the nitrogen fertilizer loading effect is the best.

[0092] Regarding the adjustment of the solution pH value during the adsorption process in step (4) of Example 1, the following Comparative Examples 4-1 to 4-4 are given.

[0093] Comparative Example 4-1

[0094] The difference between this comparative example and Example 1 lies in that the pH value of the solution is different during the adsorption process, and the specific pH value of the solution is 3.

[0095] Comparative Example 4-2

[0096] The difference between this comparative example and Example 1 lies in that the pH value of the solution is different during the adsorption process, and the specific pH value of the solution is 5.

[0097] Comparative Example 4-3

[0098] The difference between this comparative example and Example 1 lies in that the pH value of the solution is different during the adsorption process, and the specific pH value of the solution is 9.

[0099] Comparative Example 4-4

[0100] The difference between this comparative example and Example 1 lies in that the pH value of the solution is different during the adsorption process, and the specific pH value of the solution is 11.

[0101] The adsorption capacities of the modified biochars in Example 1 and Comparative Examples 4-1 to 4-4 are shown in Table 4.

[0102] Table 4 Adsorption capacities of modified biochars at different solution pH values

[0103] Project Solution pH value Adsorption capacity (mg / g) Example 1 7 113.31 Comparative Example 4-1 3 187.64 Comparative Example 4-2 5 232.66 Comparative Example 4-3 9 197.63 Comparative Example 4-4 11 175.43

[0104] As can be seen from Table 4, in Example 1, when the initial concentration and temperature of the solution are constant, as the pH of the solution increases, the ammonia nitrogen adsorption capacity of the modified biochar first increases and then decreases. When the solution pH is 7, the adsorption capacity is the highest and the nitrogen fertilizer loading effect is the best.

[0105] Regarding the adjustment of the concentration of ammonium chloride during the adsorption process in step (4) of Example 1, the following Comparative Examples 5-1 to 5-4 are given.

[0106] Comparative Example 5-1

[0107] The difference between this comparative example and Example 1 is that the concentration of ammonium chloride is different during the adsorption process, and the specific concentration of ammonium chloride is 2500 mg / L.

[0108] Comparative Example 5-2

[0109] The difference between this comparative example and Example 1 is that the concentration of ammonium chloride is different during the adsorption process, and the specific concentration of ammonium chloride is 3000 mg / L.

[0110] Comparative Example 5-3

[0111] The difference between this comparative example and Example 1 is that the concentration of ammonium chloride is different during the adsorption process, and the specific concentration of ammonium chloride is 3500 mg / L.

[0112] Comparative Example 5-4

[0113] The difference between this comparative example and Example 1 is that the concentration of ammonium chloride is different during the adsorption process, and the specific concentration of ammonium chloride is 4000 mg / L.

[0114] The adsorption capacities of the modified biochars in Example 1 and Comparative Examples 5-1 to 5-4 are shown in Table 5.

[0115] Table 5 Adsorption Capacities of Modified Biochars at Different Solution Concentrations

[0116]

[0117] As can be seen from Table 5, in Example 1, when the solution pH and solution temperature are constant, as the initial concentration of the ammonium chloride solution increases, the ammonia nitrogen adsorption capacity of the modified biochar first increases and then levels off. When the initial solution concentration is 4000 mg / L, the adsorption capacity is the highest and the nitrogen fertilizer loading effect is the best.

[0118] Example 2

[0119] The difference between this example and Example 1 is that the solution temperature, solution pH value, and solution concentration are all different during the adsorption process, specifically as follows: in step (4), the concentration of the ammonium chloride solution is 3271 mg / L, the solution temperature is 46.3 °C, and the solution pH value is 7.6.

[0120] In response to the adjustment of the solution temperature, pH value, and concentration during the adsorption process in step (4) of Example 2, the following Comparative Examples 6-1 to 6-3 are given.

[0121] Comparative Example 6-1

[0122] The difference between this comparative example and Example 2 is that the solution temperature, solution pH value, and solution concentration are all different during the adsorption process, specifically as follows: in step (4), the concentration of the ammonium chloride solution is 2000 mg / L, the solution temperature is 45 °C, and the solution pH value is 5.

[0123] Comparative Example 6-2

[0124] The difference between this comparative example and Example 2 is that the solution temperature, solution pH value, and solution concentration are all different during the adsorption process, specifically as follows: in step (4), the concentration of the ammonium chloride solution is 2000 mg / L, the solution temperature is 35 °C, and the solution pH value is 7.

[0125] Comparative Example 6-3

[0126] The difference between this comparative example and Example 2 is that the solution temperature, solution pH value, and solution concentration are all different during the adsorption process, specifically as follows: in step (4), the concentration of the ammonium chloride solution is 3000 mg / L, the solution temperature is 35 °C, and the solution pH value is 5.

[0127] The adsorption capacities of the modified biochars of Example 2 and Comparative Examples 6-1 to 6-3 are shown in Table 4.

[0128] Table 6 Adsorption capacities of modified biochars under different adsorption conditions

[0129]

[0130]

[0131] As can be seen from Table 6, in Example 2, when the solution pH is 7.6, the solution temperature is 46.3 °C, and the initial concentration of the ammonium chloride solution is 3271 mg / L, the ammonia nitrogen adsorption capacity of the modified biochar is the highest, and the nitrogen fertilizer loading effect is the best.

[0132] Test Example 1

[0133] The modified distiller's grains biochar-based nitrogen fertilizer prepared in Example 2 and conventional urea were applied to the cultivation of lettuce. The type of lettuce is loose-leaf lettuce (Dashusheng), which has the characteristics of strong growth, good comprehensive resistance, cold tolerance, and high yield, and is more suitable for cultivation in northern greenhouse greenhouses. The fertilizer application effect of the present invention was evaluated through the lettuce growth indexes. The test process is as follows:

[0134] After the lettuce was planted, 0.3 g of the modified distiller's grains biochar-based nitrogen fertilizer prepared in Example 2 or 0.3 g of conventional urea was evenly added to the soil of each lettuce plant once at the seedling stage of lettuce. The physical and chemical properties and nutrient indexes of the soil were measured in the middle of each growth period, and the results are shown in Table 7. The physiological related indexes of lettuce growth were measured at the rosette stage, and the results are shown in Table 8. The yield and quality related indexes of lettuce were measured at the end of the mature stage, and the results are shown in Table 9.

[0135] (1) Soil physical and chemical properties and nutrient indexes: soil pH, ammonium nitrogen, nitrate nitrogen, as shown in Table 7.

[0136] Table 7 Physical and chemical properties and nutrient indexes

[0137]

[0138] (2) Growth indexes: plant height, stem diameter, leaf area, etc., as shown in Table 8.

[0139] Table 8 Lettuce growth indexes

[0140] Applied fertilizer Plant height (cm) <![CDATA[Stem diameter (cm 3 )]]> <![CDATA[Leaf area (cm 2 ) <!-- 9 -->]]> Loaded nitrogen fertilizer 15.21 6.51 238.22 Conventional urea 12.27 5.85 203.22

[0141] (3) Physiological indexes: relative chlorophyll SPAD content, as shown in Table 9.

[0142] Table 9 Lettuce physiological indexes

[0143] Applied fertilizer Relative chlorophyll SPAD content Example 2 44.3 Conventional urea 38.27

[0144] (4) The harvest - period yield (fresh weight and dry weight) and quality indexes (contents of vitamin C, soluble sugar, soluble protein, etc.) are shown in Table 10.

[0145] Table 10 Lettuce Yield and Quality Indexes

[0146]

[0147] It can be seen from the test results that the soil nutrient release rate of the modified distiller's grains biochar - based nitrogen fertilizer prepared in Example 2 is slower than that of conventional urea, the soil acidification is improved to a certain extent, the lettuce grows better, and the yield and nutrients are more abundant. Therefore, the nitrogen fertilizer prepared by the present invention significantly improves the growth of lettuce.

[0148] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions of the present invention or make equivalent replacements, and these modifications or equivalent replacements cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present invention.

Claims

1. Preparation method of modified distiller's grains biochar-based nitrogen fertilizer, characterized in that: The following steps are involved: (1) drying and crushing the lees to obtain lees particles; (2) mixing and impregnating the distiller's grains with a phosphoric acid solution, and then drying to obtain modified distiller's grains; (3) pyrolyzing the modified wine grains under a protective atmosphere to obtain modified biochar; (4) Adding ammonium chloride solution to the modified biochar, adjusting the pH value, heating and shaking, and then taking out the modified biochar after adsorption is completed and drying it to obtain modified distiller's grains biochar-based nitrogen fertilizer.

2. The preparation method of the modified distiller's grains biochar-based nitrogen fertilizer according to claim 1, wherein: In step (1), the wine lees are crushed to 0.15-0.35 mm.

3. The preparation method of the modified distiller's grains biochar-based nitrogen fertilizer according to claim 1, wherein: In step (2), the concentration of the phosphoric acid solution is 1-3 mol / L, and the mass volume ratio of the vinasse particles to the phosphoric acid solution is 5-15 g:150-250 mL.

4. The preparation method of the modified distiller's grains biochar-based nitrogen fertilizer according to claim 1, wherein: In step (2), the immersion temperature is 60-80° C. and the immersion time is 24-48 hours.

5. The preparation method of the modified distiller's grains biochar-based nitrogen fertilizer according to claim 1, characterized in that: In step (3), the heating rate is 4-10°C / min, the pyrolysis temperature is 550-850°C, and the constant temperature time is 60-120min.

6. The preparation method of the modified distiller's grains biochar-based nitrogen fertilizer according to claim 1, wherein: In step (4), the concentration of the ammonium chloride solution is 2000-4000 mg / L, and the mass volume ratio of the modified biochar to the ammonium chloride solution is 0.05-0.15 g:100 mL.

7. The preparation method of the modified distiller's grains biochar-based nitrogen fertilizer according to claim 1, wherein: In step (4), the pH value is adjusted to 3-11, the heating temperature is 25-65° C., and the oscillation time is 5-10 h.

8. Modified distiller's grains biochar-based nitrogen fertilizer, characterized in that: Prepared by the preparation method according to any one of claims 1 to 7.

9. Use of the modified distiller's grains biochar-based nitrogen fertilizer according to claim 8, characterized in that: Application of modified distiller's grains biochar-based nitrogen fertilizer in lettuce cultivation.

10. Use of the modified distiller's grains biochar-based nitrogen fertilizer according to claim 9, characterized in that: Lettuce seedlings with uniform growth were transplanted and planted. Phosphorus fertilizer and potassium fertilizer were applied to the soil as base fertilizer before the lettuce was planted. After the lettuce was planted, modified distiller's grains biochar-based nitrogen fertilizer was added to the soil. The physiological indicators related to the growth of the lettuce were measured every 3 days after planting.

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