Preparation and application of oxidized modified straw biomass charcoal

Abstract

The application discloses a kind of preparation and application of oxidized modified straw biomass charcoal, comprising: straw biomass charcoal is prepared by calcining in inert atmosphere;Straw biomass charcoal is placed in plasma ball mill, and plasma ball milling treatment is carried out under inert atmosphere;After ball milling, straw biomass charcoal is oxidized by microwave heating under oxidizing atmosphere, and after reaction, it is cooled to room temperature under oxidizing atmosphere, and oxidized modified straw biomass charcoal is obtained.The surface of straw biomass charcoal is oxidized in the application, the active functional groups on its surface are increased, and microwave and oxidation treatment can form rich pore structure in the material, increase its specific surface area, and improve its removal capacity for uranium.The preparation method of the application is simple, green and efficient, provides new technical support for modification and high-value material utilization of low-grade biomass charcoal in straw pyrolysis gasification poly-generation system, and supports the development of straw high-value efficient utilization industry.

Description

Technical Field

[0001] This invention belongs to the field of environmental material preparation technology. More specifically, this invention relates to the preparation and application of oxidized modified straw biochar. Background Technology

[0002] Among various energy utilization methods, combined heat and power (CHP) technologies based on pyrolysis or gasification are currently the most valuable, mature, convenient, and stable methods, yielding not only carbon-neutral fuels (pyrolysis gas or pyrolysis oil) but also carbon-negative biochar. However, as a low-grade carbonized material, biochar lacks active functional groups or components on its surface, making it difficult to directly serve as a high-value environmental functional material. This limits the overall economic benefits of straw thermochemical conversion. Currently, there is a lack of low-cost, green, and efficient functional modification technologies to enhance the environmental performance and value of biochar. Summary of the Invention

[0003] One object of the present invention is to solve at least the above-mentioned problems and / or defects, and to provide at least the advantages described below.

[0004] To achieve these objectives and other advantages of the present invention, a method for preparing oxidized modified straw biochar is provided, comprising the following steps:

[0005] Step 1: Rinse the straw with deionized water to remove surface impurities, then dry and crush it. Then calcine it in an inert atmosphere, cool it naturally to room temperature, wash it, dry it, and grind it to obtain straw biochar.

[0006] Step 2: Place the straw biochar into a plasma ball mill and perform plasma ball milling treatment under an inert atmosphere;

[0007] Step 3: The straw biochar after ball milling in Step 2 is subjected to an oxidation reaction by microwave heating in an oxidizing atmosphere. After the reaction is completed, the temperature is lowered to room temperature in the oxidizing atmosphere to obtain oxidized modified straw biochar.

[0008] Preferably, in steps one and two, the inert atmosphere is one or more of nitrogen, helium, and argon.

[0009] Preferably, in step one, the drying temperature is 60–100°C.

[0010] Preferably, in step one, the material is crushed to 60-100 mesh and ground to 200-300 mesh.

[0011] Preferably, in step one, the calcination is carried out by heating the temperature to 400-700°C at a rate of 10-30°C / min and holding it at that temperature for 2-5 hours.

[0012] Preferably, in step two, the plasma ball mill voltage is 10-20kV, the discharge current is 1-2.5A, the gas pressure inside the ball mill jar is 0.1-0.3MPa, the ball mill speed is 500-1000rpm, the ball milling media is tungsten carbide balls or zirconium oxide balls, the ball-to-material ratio is 10-30:1, and the ball milling time is 30-60min.

[0013] Preferably, in step three, the oxidizing atmosphere is any one of air, water vapor, or carbon dioxide.

[0014] Preferably, in step three, the microwave heating power is 500-800W.

[0015] Preferably, in step three, the microwave heating time is 20 to 40 minutes.

[0016] Application of oxidized modified straw biochar prepared by the method described above in the treatment of uranium-containing wastewater.

[0017] To further improve the uranium removal capability of the material, this invention also provides a method for pretreating the oxidized modified straw biochar obtained in step three. The specific steps of the pretreating method include: adding the obtained oxidized modified straw biochar and hydroxylamine hydrochloride to deionized water and stirring evenly to obtain a mixed solution; irradiating the mixed solution with an electron beam; then filtering, washing, and drying with supercritical carbon dioxide to obtain the pretreated oxidized modified straw biochar.

[0018] Preferably, the mass-to-volume ratio of the oxidized modified straw biochar, hydroxylamine hydrochloride, and deionized water is 1g:0.4-0.8g:100-150mL.

[0019] Preferably, the electron beam irradiation dose is 20–60 kGy, and the dose rate is 1–3 kGy / h.

[0020] Preferably, the temperature for supercritical carbon dioxide drying is 35–50°C, the pressure is 10–20 MPa, the flow rate of the supercritical fluid is 1000–2000 L / h, and the drying time is 1–2 h.

[0021] This invention offers at least the following beneficial effects: It provides a method for preparing and applying oxidized straw biochar. Oxidizing the surface of the straw biochar increases its surface active functional groups. Simultaneously, microwave and oxidation treatments create a rich porous structure within the material, increasing its specific surface area and enhancing its uranium removal capacity. This invention utilizes a plasma ball mill to treat the straw biochar, stimulating its surface activity and promoting subsequent reactions with oxidizing gases, further improving its uranium removal capacity. The oxidized straw biochar prepared by this invention possesses a stable porous structure, a large specific surface area, and an adsorption capacity for uranium in wastewater exceeding 88 mg / g. The preparation method of this invention is simple, green, and efficient, providing new technical support for the modification and high-value material utilization of low-grade biochar in straw pyrolysis gasification multi-product systems, and supporting the development of industries such as straw pyrolysis gasification multi-product systems and biochar materials, which are crucial for the high-value and efficient utilization of straw.

[0022] This invention utilizes hydroxylamine hydrochloride to pretreat oxidized straw biochar, introducing amino groups to increase surface active sites and enhance its adsorption capacity and selectivity. Electron beam irradiation is then used to treat a mixed solution of oxidized straw biochar and hydroxylamine hydrochloride, promoting a full reaction between the two and further increasing the number of active sites on the surface of the oxidized straw biochar. Furthermore, this invention employs supercritical carbon dioxide drying, which offers high drying efficiency and preserves the original structural morphology of the biochar without causing pore shrinkage or structural damage, thus maintaining the porous structure of the straw biochar.

[0023] Other advantages, objectives and features of the present invention will become apparent in part from the following description, and in part from those skilled in the art through study and practice of the invention. Detailed Implementation

[0024] The present invention will be further described in detail below with reference to embodiments, so that those skilled in the art can implement it based on the description.

[0025] It should be understood that terms such as “having,” “comprising,” and “including” as used herein do not exclude the presence or addition of one or more other elements or combinations thereof.

[0026] Example 1

[0027] A method for preparing oxidized modified straw biochar includes the following steps:

[0028] Step 1: Rinse the straw with deionized water to remove surface impurities, then dry it at 80℃. Use a pulverizer to pulverize the straw to 80 mesh, then put it into a muffle furnace and heat it to 500℃ in a nitrogen atmosphere at a heating rate of 20℃ / min. Keep it at this temperature for 4 hours. After it cools naturally to room temperature, take it out, wash it twice with deionized water, dry it at 80℃, and grind it to 200 mesh to obtain straw biochar.

[0029] Step 2: Take 10g of straw biochar and put it into a plasma ball mill. Perform plasma ball milling for 45min under a nitrogen atmosphere. The plasma ball mill voltage is 15kV, the discharge current is 1.5A, the gas pressure inside the ball mill is 0.2MPa, the ball milling speed is 800rpm, the ball milling media is tungsten carbide balls, and the ball-to-material ratio is 20:1.

[0030] Step 3: The straw biochar after ball milling in Step 2 is subjected to an oxidation reaction by microwave heating under a carbon dioxide atmosphere. After the reaction is carried out for 30 minutes, the temperature is lowered to room temperature under a carbon dioxide atmosphere to obtain oxidized modified straw biochar. The microwave heating power is 600W.

[0031] Example 2

[0032] A method for preparing oxidized modified straw biochar includes the following steps:

[0033] Step 1: Rinse the straw with deionized water to remove surface impurities, then dry it at 100℃. Crush the straw to 100 mesh using a pulverizer, then add it to a muffle furnace and heat it to 600℃ in a nitrogen atmosphere at a heating rate of 30℃ / min. Keep it at this temperature for 3 hours. After it cools naturally to room temperature, take it out, wash it twice with deionized water, dry it at 100℃, and grind it to 270 mesh to obtain straw biochar.

[0034] Step 2: Take 10g of straw biochar and put it into a plasma ball mill. Perform plasma ball milling for 30min under a nitrogen atmosphere. The plasma ball mill voltage is 20kV, the discharge current is 2A, the gas pressure inside the ball mill is 0.3MPa, the ball mill speed is 1000rpm, the ball milling medium is tungsten carbide balls, and the ball-to-material ratio is 30:1.

[0035] Step 3: The straw biochar after ball milling in Step 2 is subjected to an oxidation reaction by microwave heating under a carbon dioxide atmosphere. After reacting for 40 minutes, the mixture is cooled to room temperature under a carbon dioxide atmosphere to obtain oxidized modified straw biochar. The microwave heating power is 500W.

[0036] Example 3

[0037] A method for preparing oxidized modified straw biochar includes the following steps:

[0038] Step 1: Rinse the straw with deionized water to remove surface impurities, then dry it at 60℃. Use a pulverizer to pulverize the straw to 60 mesh, then put it into a muffle furnace and heat it to 700℃ in a nitrogen atmosphere at a heating rate of 10℃ / min. Keep it at this temperature for 2 hours, and after it cools naturally to room temperature, take it out, wash it twice with deionized water, dry it at 60℃, and grind it to 230 mesh to obtain straw biochar.

[0039] Step 2: Take 10g of straw biochar and put it into a plasma ball mill. Perform plasma ball milling for 60min under a nitrogen atmosphere. The plasma ball mill voltage is 10kV, the discharge current is 1A, the gas pressure inside the ball mill is 0.1MPa, the ball mill speed is 600rpm, the ball milling medium is tungsten carbide balls, and the ball-to-material ratio is 10:1.

[0040] Step 3: The straw biochar after ball milling in Step 2 is subjected to an oxidation reaction by microwave heating under a carbon dioxide atmosphere. After the reaction is carried out for 20 minutes, the temperature is lowered to room temperature under a carbon dioxide atmosphere to obtain oxidized modified straw biochar. The microwave heating power is 800W.

[0041] Example 4

[0042] A method for preparing oxidized modified straw biochar includes the following steps:

[0043] Step 1: Rinse the straw with deionized water to remove surface impurities, then dry it at 80℃. Use a pulverizer to pulverize the straw to 80 mesh, then put it into a muffle furnace and heat it to 500℃ in a nitrogen atmosphere at a heating rate of 20℃ / min. Keep it at this temperature for 4 hours. After it cools naturally to room temperature, take it out, wash it twice with deionized water, dry it at 80℃, and grind it to 200 mesh to obtain straw biochar.

[0044] Step 2: Take 10g of straw biochar and put it into a plasma ball mill. Perform plasma ball milling for 45min under a nitrogen atmosphere. The plasma ball mill voltage is 15kV, the discharge current is 1.5A, the gas pressure inside the ball mill is 0.2MPa, the ball milling speed is 800rpm, the ball milling media is tungsten carbide balls, and the ball-to-material ratio is 20:1.

[0045] Step 3: The straw biochar after ball milling in Step 2 is subjected to an oxidation reaction by microwave heating under a carbon dioxide atmosphere. After the reaction is carried out for 30 minutes, the temperature is lowered to room temperature under a carbon dioxide atmosphere to obtain oxidized modified straw biochar. The microwave heating power is 600W.

[0046] Step 4: Add 5g of the oxidized modified straw biochar obtained in Step 3 and 2.5g of hydroxylamine hydrochloride to 600mL of deionized water and stir until homogeneous to obtain a mixed solution. Irradiate the mixed solution with an electron beam at a dose of 40kGy and a dose rate of 2kGy / h. Then filter, wash twice with deionized water, and dry with supercritical carbon dioxide for 2h to obtain pretreated oxidized modified straw biochar. The temperature of supercritical carbon dioxide drying is 40℃, the pressure is 15MPa, and the flow rate of supercritical fluid is 1500L / h.

[0047] Comparative Example 1

[0048] A method for preparing oxidized modified straw biochar includes the following steps:

[0049] Step 1: Rinse the straw with deionized water to remove surface impurities, then dry it at 80℃. Use a pulverizer to pulverize the straw to 80 mesh, then put it into a muffle furnace and heat it to 500℃ in a nitrogen atmosphere at a heating rate of 20℃ / min. Keep it at this temperature for 4 hours. After it cools naturally to room temperature, take it out, wash it twice with deionized water, dry it at 80℃, and grind it to 200 mesh to obtain straw biochar.

[0050] Step 2: 10g of the straw biochar obtained in Step 1 is subjected to an oxidation reaction by microwave heating under a carbon dioxide atmosphere. After the reaction is carried out for 30 minutes, the temperature is lowered to room temperature under a carbon dioxide atmosphere to obtain oxidized modified straw biochar. The microwave heating power is 600W.

[0051] Comparative Example 2

[0052] This comparative example does not involve electron beam irradiation. The mixed solution is heated to 60°C and kept at that temperature for 20 hours. The remaining steps are the same as in Example 4.

[0053] Comparative Example 3

[0054] In this comparative example, drying in a 60°C vacuum drying oven for 12 hours was used instead of supercritical carbon dioxide drying, and the remaining steps were the same as in Example 4.

[0055] U(VI) removal experiment: 5 mg of sample was added to 20 mL of U(VI) solution (U(VI) concentration 100 mg / L, pH = 6.0), and the solution was shaken at 200 rpm for 4 h at 25 °C using a constant temperature shaker. Solid-liquid separation was performed using a microporous membrane, and the U(VI) concentration after the reaction was determined at 651.8 nm by azoarsine III spectrophotometry. Adsorption capacity Q (mg / g) = (C0 - C) × V / m, where C0 (mg / mL) is the initial concentration of U(VI), C (mg / mL) is the U(VI) concentration after the reaction, V (mL) is the volume of the reaction solution, and m (g) is the mass of the sample. The results are shown in Table 1.

[0056] Table 1

[0057]

[0058] As shown in Table 1, the oxidized modified straw biochar prepared by this invention can effectively remove U(VI) from water, with an adsorption capacity of over 88.21 mg / g. Example 4 exhibits the highest adsorption capacity, reaching 101.67 mg / g, indicating that this invention utilizes hydroxylamine hydrochloride for pretreatment of the oxidized modified straw biochar, introducing amino groups to increase its surface active sites, thereby enhancing its adsorption capacity and selectivity, and improving the uranium removal rate. Comparing Example 1 and Comparative Example 1 demonstrates that this invention utilizes a plasma ball mill to treat the straw biochar, stimulating its surface activity and promoting its subsequent reaction with oxidizing gases, further enhancing its uranium removal capacity. Comparing Example 4 and Comparative Example 2 shows that electron beam irradiation can promote the full reaction between the oxidized modified straw biochar and hydroxylamine hydrochloride, increasing the surface active sites of the straw biochar, thus improving its uranium removal capacity. Comparing Example 4 and Comparative Example 3 demonstrates that supercritical carbon dioxide drying has high efficiency and can maintain the porous structure of the biochar, thereby improving its uranium adsorption capacity.

[0059] Although embodiments of the present invention have been disclosed above, they are not limited to the applications listed in the specification and embodiments. They can be applied to various fields suitable for the present invention. For those skilled in the art, other modifications can be easily made. Therefore, without departing from the general concept defined by the claims and their equivalents, the present invention is not limited to the specific details and embodiments shown and described herein.

Claims

1. A method for preparing oxidized modified straw biochar, characterized in that, Includes the following steps: Step 1: Rinse the straw with deionized water to remove surface impurities, then dry and crush it. Then calcine it in an inert atmosphere, cool it naturally to room temperature, wash it, dry it, and grind it to obtain straw biochar. Step 2: Place the straw biochar into a plasma ball mill and perform plasma ball milling under an inert atmosphere; wherein, the voltage of the plasma ball mill is 10~20kV, the discharge current is 1~2.5A, the gas pressure inside the ball mill is 0.1~0.3MPa, the ball milling speed is 500~1000rpm, the ball milling media is tungsten carbide balls or zirconium oxide balls, the ball-to-material ratio is 10~30:1, and the ball milling time is 30~60min; Step 3: The straw biochar after ball milling in Step 2 is subjected to an oxidation reaction by microwave heating under an oxidizing atmosphere. After the reaction is completed, the temperature is lowered to room temperature under the oxidizing atmosphere to obtain oxidized modified straw biochar. The oxidizing atmosphere is carbon dioxide. The microwave heating time is 20-40 minutes. The obtained oxidized modified straw biochar is pretreated. The specific steps of the pretreatment include: adding the obtained oxidized modified straw biochar and hydroxylamine hydrochloride to deionized water and stirring evenly to obtain a mixed solution; irradiating the mixed solution with an electron beam; then filtering, washing, and drying with supercritical carbon dioxide to obtain pretreated oxidized modified straw biochar.

2. The method for preparing oxidized modified straw biochar as described in claim 1, characterized in that, In steps one and two, the inert atmosphere is one or more of nitrogen, helium, and argon.

3. The method for preparing oxidized modified straw biochar as described in claim 1, characterized in that, In step one, the drying temperature is 60~100℃.

4. The method for preparing oxidized modified straw biochar as described in claim 1, characterized in that, In step one, the material is crushed to 60-100 mesh and ground to 200-300 mesh.

5. The method for preparing oxidized modified straw biochar as described in claim 1, characterized in that, In step one, the specific method of calcination is as follows: the temperature is increased to 400-700℃ at a heating rate of 10-30℃ / min, and then held for 2-5 hours.

6. The method for preparing oxidized modified straw biochar as described in claim 1, characterized in that, In step three, the microwave heating power is 500~800W.

7. The application of an oxidized modified straw biochar prepared by any one of claims 1-6 in the treatment of uranium-containing wastewater.

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