Preparation method of efficient mediation nanometer magnesium oxide crystal loaded charcoal adsorption material

Abstract

The invention relates to the technical field of materials, and discloses a preparation method of an efficient mediating nanometer magnesium oxide crystal loaded biochar adsorption material, which comprises the following steps: drying coffee grounds as a biomass raw material under the drying condition of 105 DEG C, carrying out particle size detection on a grinding machine by adopting a particle size analyzer, grinding by the grinding machine, and screening by a 40-mesh screen; stirring 10 g of the powder and 10 g of urea to be fully mixed, and performing pyrolysis in a vacuum tube furnace; transferring all the charcoal obtained after pyrolysis into 250mL of magnesium chloride solution, stirring, adjusting the pH value of the mixed solution by using a sodium hydroxide solution after stirring, and standing; centrifuging and standing to obtain a solution, and drying the centrifuged precipitate at 105 DEG C until the weight is constant; grinding the dried powder through a grinding machine, sieving through a 40-mesh sieve, and pyrolyzing again in a vacuum tube furnace; and cleaning the pyrolyzed powder with deionized water until the supernatant is neutral, drying, and storing in a dry place to obtain the charcoal adsorption material. The invention also discloses a method.

Description

Technical Field

[0001] The invention relates to the technical field of materials, and in particular to a method for preparing a biochar adsorption material efficiently mediating nano magnesium oxide crystal loading. Background Art

[0002] Eutrophication caused by excessive phosphorus discharge into wastewater seriously deteriorates the water quality of natural water bodies and ultimately poses a threat to human health. To address this problem, sewage treatment plants use chemical flocculation to remove phosphorus, which can achieve the goal of removing most of the phosphates in sewage. However, the latest research shows that ultra-low concentrations of phosphates in water (0.02-0.1 mg / L) can also successfully induce eutrophication. At the same time, existing processes in sewage treatment plants make it difficult to efficiently remove low concentrations of phosphorus in water and reduce them to a safe range.

[0003] Among all available technologies, adsorption is widely regarded as a promising technology for removing phosphate from water, especially for the treatment of low-concentration phosphate wastewater; biochar is considered to be a good adsorbent material due to its excellent integrity, porous structure and large specific surface area; on this basis, by doping with magnesium, the surface charge of biochar can be adjusted and more phosphorus adsorption sites can be provided, so that an efficient phosphorus removal adsorbent - magnesium-doped biochar can be prepared; however, due to the high surface energy of magnesium oxide during the generation process, the generated MgO crystals are prone to spontaneous agglomeration to form blocks in biochar, which greatly hinders the effective utilization of active MgO sites and blocks the structure of biochar, thereby affecting the phosphorus removal performance of magnesium-doped biochar; in order to improve the current adsorption effect, the existing response method is to continuously increase the doping amount of magnesium, thereby improving the adsorption effect of magnesium-doped biochar; however, as the amount of doped magnesium continues to increase, the utilization efficiency of magnesium continues to decrease, and the preparation cost also increases significantly, which ultimately leads to the inability of magnesium-doped biochar to be used in actual water pollution control. Summary of the invention

[0004] The purpose of the present invention is to solve the above problems and to design a method for preparing a biochar adsorption material that efficiently mediates nano-magnesium oxide crystal loading.

[0005] The present invention provides a method for preparing a biochar adsorption material efficiently mediated by nano-magnesium oxide crystal loading, and the method for preparing a biochar adsorption material efficiently mediated by nano-magnesium oxide crystal loading comprises the following steps:

[0006] Step 1: Dry coffee grounds at 105°C as biomass raw materials, use a particle size analyzer to detect the particle size of the grinder, grind the grounds through the grinder and pass through a 40-mesh sieve;

[0007] Step 2: Take 10 g of the powder obtained in step 1 and 10 g of urea, stir them to mix them thoroughly, and perform pyrolysis in a vacuum tube furnace;

[0008] Step 3: transfer all the biochar obtained after pyrolysis in step 2 into 250 mL of magnesium chloride solution and stir. After stirring, adjust the pH of the mixed solution with sodium hydroxide solution and let it stand;

[0009] Step 4: Centrifuge the solution obtained after standing in step 3, and dry the precipitate after centrifugation at 105° C. to constant weight;

[0010] Step 5: Grind the powder obtained by drying in step 4 through a grinder and pass it through a 40-mesh sieve, and pyrolyze it again in a vacuum tube furnace;

[0011] Step 6: Wash the powder after pyrolysis in step 5 with deionized water until the supernatant is neutral, dry it and store it in a dry place to obtain a biochar adsorption material.

[0012] Optionally, in the first implementation of the present invention, step 2 specifically includes the following process:

[0013] Pour 10 g of the powder obtained in step 1 and 10 g of urea into a container, turn on the agitator, stir at 50 rpm for 5 minutes to preliminarily mix the two substances, increase the speed to 150 rpm, continue stirring for 15 minutes, mix the two substances thoroughly, and put the fully mixed coffee grounds powder and urea into a vacuum tube furnace for pyrolysis.

[0014] Optionally, in a second implementation of the present invention, the pyrolysis parameters of the vacuum tube furnace are set, the heating rate is set to 10°C / min, the pyrolysis temperature is set to 600°C, and the pyrolysis time is set to 1h.

[0015] Optionally, in a third implementation of the present invention, step three specifically includes the following process:

[0016] The biochar obtained after pyrolysis in step 2 is taken out from the vacuum tube furnace, and all the biochar is transferred to a clean container;

[0017] Measure 250 mL of 0.1 M magnesium chloride solution, slowly pour the biochar into the container containing the magnesium chloride solution, and stir with a stirrer for 2 hours to allow the biochar to fully contact with the magnesium chloride solution;

[0018] After stirring is completed, the pH value of the mixed solution is adjusted with sodium hydroxide solution, and the sodium hydroxide solution is slowly added dropwise while stirring until the pH value of the mixed solution reaches 10. After adjusting the pH value, the mixed solution is allowed to stand for 12 hours.

[0019] Optionally, in a fourth implementation of the present invention, step 4 specifically includes the following process:

[0020] Pour the solution after standing in step 3 into a centrifuge tube, set the centrifugal speed to 5000 rpm to 8000 rpm, the centrifugal time to 15 minutes to 30 minutes, start the centrifuge for centrifugal treatment, and after the centrifugation is completed, put the precipitate at the bottom of the centrifuge tube into a drying oven, set the drying oven temperature to 105°C, and dry the precipitate to constant weight.

[0021] Optionally, in a fifth implementation of the present invention, step five specifically includes the following process:

[0022] Take out the powder obtained by drying in step 4 from the drying oven, put the powder into a grinder for grinding, pass the ground powder through a 40-mesh sieve, put the sieved powder into a vacuum tube furnace for pyrolysis again, set the pyrolysis parameters of the vacuum tube furnace, set the heating rate to 10°C / min, the pyrolysis temperature to 600°C, and the pyrolysis time to 1h.

[0023] Optionally, in a sixth implementation of the present invention, step six specifically includes the following process:

[0024] Put the powder after pyrolysis in step 5 into a container, add deionized water and stir until the pH value of the supernatant is neutral, put the cleaned powder into a drying oven, set the drying oven temperature to 80°C to 100°C, and dry to constant weight. After drying, store the powder in a dry place to obtain a biochar adsorption material.

[0025] Optionally, in the seventh implementation of the present invention, a magnetic stirrer is used for stirring at a speed of 80 rpm for 20 minutes, the supernatant is taken every 10 minutes, and the pH value of the supernatant is detected with a pH meter. If the supernatant is not neutral, deionized water is continued to be added for washing, and the stirring and standing process is repeated until the pH value of the supernatant is neutral.

[0026] Conventional magnesium-doped biochar adopts a one-step pyrolysis method to prepare the material. During the preparation process, magnesium oxide crystals will be embedded in the structure as the biochar grows. At the same time, the high surface energy of magnesium oxide crystals themselves and the lack of external constraints cause the magnesium oxide crystals to spontaneously agglomerate into blocks, blocking the pore structure of biochar and causing extremely low magnesium oxide point utilization. The present invention adopts a distributed pyrolysis method and nitrogen pre-doping to achieve biochar pore size adjustment, ultimately mediating the uniform loading of nano-scale magnesium oxide crystals. The preparation is carried out under the same biomass raw material and magnesium doping ratio. Compared with the prior art, the present invention has the following advantages:

[0027] (1) The conventional one-step pyrolysis method was transformed into a two-step pyrolysis method and nitrogen was added to achieve the customization of the porous biochar template through nitrogen pre-doping, forming a physical regional restriction for the in-situ generation of MgO. In contrast, the conventional one-step pyrolysis method cannot achieve the size restriction of the MgO crystals therein;

[0028] (2) The average particle size of magnesium oxide crystals in conventional magnesium-doped biochar is 32.8 nm, while the average particle size of magnesium oxide crystals in the novel nano-magnesium oxide-biochar developed by the present invention is only 4.17 nm;

[0029] (3) The adsorption performance of conventional magnesium-doped biochar is 40.3 mg / g, while the maximum phosphorus adsorption capacity of the new nano-magnesium oxide-biochar adsorbent developed by the present invention is 108 mg / g, which is 2.7 times that of conventional materials;

[0030] (4) When the effluent phosphate concentration is 0.5 mg / L, the adsorption performance of conventional magnesium-doped biochar is only 2.31 mg / g, while the maximum phosphorus adsorption capacity of the new nano-magnesium oxide-biochar adsorbent developed by the present invention is 40.9 mg / g, which is 17.7 times that of conventional materials;

[0031] (5) By creating a suitable biochar skeleton by nitrogen pre-doping before the magnesium doping step, the confined loading of magnesium can be achieved, which significantly improves the adsorption performance of magnesium-biochar as a phosphorus adsorbent. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the following detailed description of the preferred embodiment.The drawings are only for the purpose of illustrating the preferred embodiments and are not to be construed as limiting the invention.

[0033] Figure 1 The adsorption equilibrium curves of two different adsorbents at different phosphate equilibrium concentrations;

[0034] Figure 2 This is a schematic diagram comparing the phosphate adsorption amount of two different adsorbents at different times;

[0035] Figure 3 The graphs of the relationship between the adsorption amount and relative pressure, the pore volume distribution graph and the FTIR spectrum graph of two different adsorbents;

[0036] Figure 4 This is a schematic diagram of the adsorption effect of the adsorbent provided by the present invention. DETAILED DESCRIPTION

[0037] The present invention is further described below in conjunction with specific examples. It should be understood that these examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention. The experimental methods in the following examples without specifying specific conditions are usually carried out under conventional conditions or according to the conditions recommended by the manufacturer. The reagents, materials and equipment, unless otherwise specified, can be obtained from commercial sources.

[0038] Example 1

[0039] For ease of understanding, the specific process of the embodiment of the present invention is described below. The method for preparing a biochar adsorption material loaded with nano-magnesium oxide crystals with high efficiency comprises the following steps:

[0040] Step 1: Dry coffee grounds at 105°C as biomass raw materials, use a particle size analyzer to detect the particle size of the grinder, grind the grounds through the grinder and pass through a 40-mesh sieve;

[0041] Step 2: Take 10 g of the powder obtained in step 1 and 10 g of urea, stir them to mix them thoroughly, and perform pyrolysis in a vacuum tube furnace;

[0042] Step 3: transfer all the biochar obtained after pyrolysis in step 2 into 250 mL of magnesium chloride solution and stir. After stirring, adjust the pH of the mixed solution with sodium hydroxide solution and let it stand;

[0043] Step 4: Centrifuge the solution obtained after standing in step 3, and dry the precipitate after centrifugation at 105° C. to constant weight;

[0044] Step 5: Grind the powder obtained by drying in step 4 through a grinder and pass it through a 40-mesh sieve, and pyrolyze it again in a vacuum tube furnace;

[0045] Step 6: Wash the powder after pyrolysis in step 5 with deionized water until the supernatant is neutral, dry it and store it in a dry place to obtain a biochar adsorption material.

[0046] In this embodiment, step 2 specifically includes the following process: pour 10g of the powder obtained in step 1 and 10g of urea into a container, turn on the agitator, stir at 50 rpm for 5 minutes to preliminarily mix the two substances, increase the speed to 150 rpm, continue stirring for 15 minutes, fully mix the two substances, put the fully mixed coffee grounds powder and urea into a vacuum tube furnace for pyrolysis, set the pyrolysis parameters of the vacuum tube furnace, set the heating rate to 10°C / min, set the pyrolysis temperature to 600°C, and set the pyrolysis time to 1h.

[0047] In this embodiment, step three specifically includes the following process: taking out the biochar obtained after pyrolysis in step two from the vacuum tube furnace, and transferring all the biochar to a clean container; measuring 250 mL of 0.1 M magnesium chloride solution, slowly pouring the biochar into the container containing the magnesium chloride solution, turning on the agitator and stirring for 2 hours to allow the biochar to fully contact with the magnesium chloride solution; after stirring, adjusting the pH value of the mixed solution with sodium hydroxide solution, slowly adding sodium hydroxide solution while stirring until the pH value of the mixed solution reaches 10, and after adjusting the pH value, allowing the mixed solution to stand for 12 hours.

[0048] In this embodiment, step four specifically includes the following process: pouring the solution after standing in step three into a centrifuge tube, setting the centrifugal speed to 5000 rpm to 8000 rpm, the centrifugal time to 15 minutes to 30 minutes, starting the centrifuge for centrifugal treatment, and after the centrifugation is completed, placing the precipitate at the bottom of the centrifuge tube into a drying oven, setting the drying oven temperature to 105°C, and drying the precipitate to constant weight.

[0049] In this embodiment, step five specifically includes the following process: taking out the powder obtained by drying in step four from the drying oven, putting the powder into a grinder for grinding, passing the ground powder through a 40-mesh sieve, putting the sieved powder into a vacuum tube furnace for pyrolysis again, setting the pyrolysis parameters of the vacuum tube furnace, setting the heating rate to 10°C / min, the pyrolysis temperature to 600°C, and the pyrolysis time to 1h.

[0050] In this embodiment, step six specifically includes the following process: putting the powder after pyrolysis in step five into a container, adding deionized water for stirring, using a magnetic stirrer for stirring, stirring at a speed of 80 rpm for 20 minutes, taking the supernatant every 10 minutes, and detecting the pH value of the supernatant with a pH meter. If the supernatant is not neutral, continue to add deionized water for washing, repeat the stirring and standing process until the pH value of the supernatant is neutral, put the washed powder into a drying oven, set the drying oven temperature to 80°C to 100°C, and dry to constant weight. After drying, store the powder in a dry place to obtain a biochar adsorption material.

[0051] Example 2

[0052] Prepare adsorbents: conventional magnesium-doped biochar (Mg-BC) and novel nano magnesium oxide-biochar (Mg / N-BC) prepared by the method;

[0053] Add 50 ml of a certain concentration of phosphate solution to a series of 150 ml conical flasks, weigh 0.0125 g of conventional magnesium-doped biochar (Mg-BC) and new nano magnesium oxide-biochar (Mg / N-BC), respectively, add 0.0125 g of two different adsorbents to different conical flasks, seal the conical flasks, put the sealed conical flasks into a constant temperature oscillator, set the oscillation conditions to 25 ° C and 180 rpm, and regularly observe the state of the conical flask during the oscillation to ensure that the oscillation is uniform and stable. After the oscillation is completed, take out the conical flask, filter the supernatant, and take the filtrate to determine the residual phosphate concentration according to the "Determination of total phosphorus in water quality-Ammonium molybdate spectrophotometry" (GB11893-89);

[0054] like Figure 1 As shown, after experimental measurement, it was found that the maximum adsorption capacity of Mg-BC was only 40.3 mg / g, while the maximum adsorption capacity of Mg / N-BC was 108 mg / g, which was 2.7 times that of Mg-BC; at the same time, when the phosphate concentration of the effluent was 0.5 mg / L, the adsorption performance of Mg-BC was only 2.31 mg / g, while the maximum phosphorus adsorption capacity of Mg / N-BC developed by this patent was 40.9 mg / g, which was 17.7 times that of Mg-BC.

[0055] Example 3

[0056] Prepare adsorbents: conventional magnesium-doped biochar (Mg-BC) and novel nano magnesium oxide-biochar (Mg / N-BC) prepared by the method;

[0057] 1500 mL of a certain concentration of phosphate solution was added to a series of 2000 mL conical flasks, 0.75 g of conventional magnesium-doped biochar (Mg-BC) and new nano magnesium oxide-biochar (Mg / N-BC) were weighed respectively, and 0.75 g of two different adsorbents were added to different conical flasks, the conical flasks were sealed, and the sealed conical flasks were placed in a magnetic stirrer, the magnetic stirrer was turned on, and the solution in the conical flask was stirred at a preset stirring speed. Stirring can make the adsorbent fully contact with the phosphate solution and promote the adsorption reaction During the stirring process, observe the operating status of the magnetic stirrer to ensure that the stirrer can rotate stably to avoid jumping or stopping. Sample the supernatant at preset time intervals, use a sterile syringe or pipette to extract a certain volume of supernatant from the conical flask, filter the extracted supernatant through a suitable filter to remove tiny particles and impurities therein to ensure the purity of the filtrate, and take the filtrate to determine the residual phosphate concentration according to the "Determination of Total Phosphorus in Water - Ammonium Molybdate Spectrophotometry" (GB11893-89);

[0058] like Figure 2As shown in the figure, it was found through experimental measurement that when the initial phosphate concentration was 5 mg / L, the equilibrium concentrations of the two were not much different, but the adsorption rate of Mg / N-BC was 18 mg / g / h while that of Mg-BC was only 3.7 mg / g / h, which was significantly better than that of Mg-BC; when the initial phosphate concentration was 20 mg / L, the adsorption rate of Mg / N-BC was 16.9 mg / g / h while that of Mg-BC was only 6.4 mg / g / h. Moreover, at adsorption equilibrium, the removal rate of phosphate in water by Mg / N-BC was 99.2% while that of Mg-BC was only 45.5%.

[0059] Example 4

[0060] Prepare adsorbents: conventional magnesium-doped biochar (Mg-BC) and novel nano magnesium oxide-biochar (Mg / N-BC) prepared by the method;

[0061] The pore structure of the two adsorbents and the graphitization degree of biochar were characterized by BET specific surface area analyzer and Raman spectrometer, respectively. Figure 3 As shown in the figure, the specific surface areas of Mg / N-BC and Mg-BC are 115m2 / g and 32m2 / g, respectively, and Mg-BC exhibits a typical type IV BET isotherm, indicating that the Mg-BC material is mostly a mesoporous structure; while Mg / N-BC exhibits a combination of type I and type IV BET isotherms, indicating that the Mg / N-BC material is a structure that combines micropores and mesopores, such as Figure 3 a. From the pore size distribution, as Figure 3 As shown in (b), it can also be seen that Mg / N-BC has abundant microporous structures while Mg-BC only has mesoporous structures, and the pore volume of Mg / N-BC is also greatly increased, as shown in Figure 3 As shown in Figure c, the ID / IG value of the new Mg / N-BC developed by the preparation method of the present invention is 1, indicating that the disorder inside the material is increased, which is conducive to the formation of a microporous structure and ultimately achieves confined loading of nano-scale magnesium oxide.

[0062] Example 5

[0063] A laboratory-grade adsorption filter column with an effective volume of 100 mL was established using the novel nano-magnesium oxide-biochar (Mg / N-BC) developed by the preparation method of the present invention as a filter column filler. Figure 4As shown, AC is the initial phosphate concentration of 2 mg / L, and the filtration rates are 1, 0.5 and 0.25 mL / min respectively; DF is the filtration rate of 0.5 mL / min, and the initial phosphate concentrations are 0.5, 1 and 1.5 mg / L respectively. When the initial concentration is 2 mg / L, reducing the filtration rate can effectively increase the adsorption effect of the filter column, and the filtration efficiency of the filter column reaches the optimal when the filtration rate is 0.5 mL / min; when the filtration rate of the filter column is controlled at 0.5 mL / min, when the influent phosphate concentration is changed, the filter column breaks through 50% at 1020, 1040 and 1050 min respectively, indicating that the Mg / N-BC-based filter column can effectively withstand different influent phosphate concentrations and the treatment performance is predictable, which is conducive to its application in actual water bodies.

[0064] = Conventional magnesium-doped biochar uses a one-step pyrolysis method to prepare materials. In this process, there are many problems that seriously affect its performance and application. During the preparation process, magnesium oxide crystals will be embedded in the structure as the biochar grows. However, due to the high surface energy of magnesium oxide crystals themselves and the lack of external constraints, they will spontaneously agglomerate into blocks. These blocky magnesium oxides not only block the pore structure of biochar, but also greatly reduce the specific surface area and porosity of biochar, thereby affecting its adsorption performance; the blockage of the pore structure makes it difficult for target pollutants such as phosphate to enter the interior of biochar and fully contact with the adsorption sites. This leads to extremely low magnesium oxide site utilization, and a large amount of magnesium oxide cannot play its due adsorption role, resulting in a waste of resources; the conventional one-step pyrolysis method cannot achieve the size limit of magnesium oxide crystals. Due to the lack of effective control means, the size distribution of magnesium oxide crystals is relatively wide, and it is difficult to form uniform nano-scale crystals. Larger magnesium oxide crystals will not only block pores, but also may reduce the stability and recycling performance of the adsorbent.

[0065] The present invention transforms the conventional one-step pyrolysis method into a two-step pyrolysis method, and realizes the customization of the porous biochar template by adding nitrogen. Nitrogen pre-doping plays a key role in the preparation process of biochar, and it forms a physical regional restriction for the in-situ generation of magnesium oxide. This physical regional restriction effectively prevents the spontaneous agglomeration of magnesium oxide crystals, so that magnesium oxide can be evenly distributed in the pore structure of biochar. At the same time, nitrogen pre-doping can also adjust the pore size and distribution of biochar, providing a suitable space for the loading of magnesium oxide. Compared with the conventional one-step pyrolysis method, the two-step pyrolysis method of the present invention can better control the structure and performance of biochar, and create more favorable conditions for the loading of magnesium oxide. The average particle size of magnesium oxide crystals in conventional magnesium-doped biochar is 32.8 nm, while the average particle size of the magnesium oxide crystals in the new nano magnesium oxide-biochar developed by the present invention is only 4.17nm; nano-scale magnesium oxide crystals have a larger specific surface area and higher surface activity, and can provide more adsorption sites, thereby significantly improving the adsorption performance of the adsorbent; smaller crystal size can also reduce the mass transfer resistance inside the crystal, so that pollutants such as phosphate can diffuse to the adsorption sites faster, thereby increasing the adsorption rate; in addition, the uniform distribution of nano-scale magnesium oxide crystals also helps to improve the stability and recycling performance of the adsorbent; the adsorption performance of conventional magnesium-doped biochar is 40.3mg / g, while the maximum phosphorus adsorption capacity of the new nano magnesium oxide-biochar adsorbent developed by the present invention is 108mg / g, which is 2.7 times that of conventional materials. When the phosphate concentration of the effluent is 0.5 mg / L, the adsorption performance of conventional magnesium-doped biochar is only 2.31 mg / g, while the maximum phosphorus adsorption capacity of the new nano-magnesium oxide-biochar adsorbent developed by the present invention is 40.9 mg / g, which is 17.7 times that of conventional materials; this excellent adsorption performance is due to the uniform loading of nano-magnesium oxide crystals and the porous structure of biochar. Nano-magnesium oxide crystals provide a large number of adsorption sites, while the pore structure of biochar provides channels for the diffusion and adsorption of pollutants. The synergistic effect of the two enables the new nano-magnesium oxide-biochar adsorbent to efficiently remove pollutants such as phosphates from water; by creating a suitable biochar skeleton by nitrogen pre-doping before the magnesium doping step, the limited loading of magnesium is achieved. This limited loading method significantly improves the adsorption performance of magnesium-biochar, a phosphorus adsorbent; the biochar skeleton formed by nitrogen pre-doping provides a specific space for the loading of magnesium, so that magnesium can be evenly distributed in biochar, avoiding the occurrence of agglomeration. At the same time, the biochar skeleton can also form a synergistic effect with magnesium to enhance the affinity and adsorption capacity of the adsorbent for pollutants such as phosphates.

[0066] The present invention adopts a distributed pyrolysis method and nitrogen pre-doping to adjust the pore size of biochar, and finally mediates the uniform loading of nano-magnesium oxide crystals. By creating a suitable biochar skeleton by nitrogen pre-doping before the magnesium doping step to achieve the limited loading of magnesium, the adsorption performance of magnesium-biochar as a phosphorus adsorbent is significantly improved, and finally a nano-magnesium oxide-biochar adsorbent with high efficiency in phosphorus removal is created.

[0067] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. The above embodiments and descriptions are only preferred examples of the present invention and are not intended to limit the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for preparing a biochar adsorption material efficiently mediated by nano-magnesium oxide crystal loading, characterized in that: The method for preparing the biochar adsorption material efficiently mediated by nano-magnesium oxide crystal loading comprises the following steps: Step 1: Dry coffee grounds at 105°C as biomass raw materials, use a particle size analyzer to detect the particle size of the grinder, grind the grounds through the grinder and pass through a 40-mesh sieve; Step 2: Take 10 g of the powder obtained in step 1 and 10 g of urea, stir them to mix them thoroughly, and perform pyrolysis in a vacuum tube furnace; Step 3: transfer all the biochar obtained after pyrolysis in step 2 into 250 mL of magnesium chloride solution and stir. After stirring, adjust the pH of the mixed solution with sodium hydroxide solution and let it stand; Step 4: Centrifuge the solution obtained after standing in step 3, and dry the precipitate after centrifugation at 105° C. to constant weight; Step 5: Grind the powder obtained by drying in step 4 through a grinder and pass it through a 40-mesh sieve, and pyrolyze it again in a vacuum tube furnace; Step 6: Wash the powder after pyrolysis in step 5 with deionized water until the supernatant is neutral, dry it and store it in a dry place to obtain a biochar adsorption material.

2. The method for preparing a biochar adsorption material efficiently mediated by nano-magnesium oxide crystal loading according to claim 1, characterized in that: Step 2 specifically includes the following processes: Pour 10 g of the powder obtained in step 1 and 10 g of urea into a container, turn on the agitator, stir at 50 rpm for 5 minutes to preliminarily mix the two substances, increase the speed to 150 rpm, continue stirring for 15 minutes, mix the two substances thoroughly, and put the fully mixed coffee grounds powder and urea into a vacuum tube furnace for pyrolysis.

3. The method for preparing a biochar adsorption material efficiently mediated by nano-magnesium oxide crystal loading according to claim 2, characterized in that: The pyrolysis parameters of the vacuum tube furnace were set, the heating rate was set to 10 °C / min, the pyrolysis temperature was set to 600 °C, and the pyrolysis time was set to 1 h.

4. The method for preparing a biochar adsorption material efficiently mediated by nano-magnesium oxide crystal loading according to claim 1, characterized in that: Step 3 specifically includes the following processes: The biochar obtained after pyrolysis in step 2 is taken out from the vacuum tube furnace, and all the biochar is transferred to a clean container; Measure 250 mL of 0.1 M magnesium chloride solution, slowly pour the biochar into the container containing the magnesium chloride solution, and stir with a stirrer for 2 hours to allow the biochar to fully contact with the magnesium chloride solution; After stirring is completed, the pH value of the mixed solution is adjusted with sodium hydroxide solution, and the sodium hydroxide solution is slowly added dropwise while stirring until the pH value of the mixed solution reaches 10. After adjusting the pH value, the mixed solution is allowed to stand for 12 hours.

5. The method for preparing a biochar adsorption material efficiently mediated by nano-magnesium oxide crystal loading according to claim 1, characterized in that: Step 4: Specific The process includes: Pour the solution after standing in step 3 into a centrifuge tube, set the centrifugal speed to 5000 rpm to 8000 rpm, the centrifugal time to 15 minutes to 30 minutes, start the centrifuge for centrifugal treatment, and after the centrifugation is completed, put the precipitate at the bottom of the centrifuge tube into a drying oven, set the drying oven temperature to 105°C, and dry the precipitate to constant weight.

6. The method for preparing a biochar adsorption material efficiently mediated by nano-magnesium oxide crystal loading according to claim 1, characterized in that: Step 5 specifically includes the following processes: Take out the powder obtained by drying in step 4 from the drying oven, put the powder into a grinder for grinding, pass the ground powder through a 40-mesh sieve, put the sieved powder into a vacuum tube furnace for pyrolysis again, set the pyrolysis parameters of the vacuum tube furnace, set the heating rate to 10°C / min, the pyrolysis temperature to 600°C, and the pyrolysis time to 1h.

7. The method for preparing a biochar adsorption material efficiently mediated by nano-magnesium oxide crystal loading according to claim 1, characterized in that: Step 6 specifically includes the following processes: Put the powder after pyrolysis in step 5 into a container, add deionized water and stir until the pH value of the supernatant is neutral, put the cleaned powder into a drying oven, set the drying oven temperature to 80°C to 100°C, and dry to constant weight. After drying, store the powder in a dry place to obtain a biochar adsorption material.

8. The method for preparing a biochar adsorption material efficiently mediated by nano-magnesium oxide crystal loading according to claim 7, characterized in that: Use a magnetic stirrer to stir at 80 rpm for 20 minutes, take the supernatant every 10 minutes, and use a pH meter to detect the pH value of the supernatant. If the supernatant is not neutral, continue to add deionized water for washing, and repeat the stirring and standing process until the pH value of the supernatant is neutral.

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