Modified biochar material, preparation method and application

Abstract

The invention discloses a modified biochar material as well as a preparation method and application thereof. The preparation method comprises the following steps: (1) mixing graphite and cellulose in proportion, fully grinding, roasting in a tubular furnace, and cooling after roasting to obtain a biochar material; and (3) mixing the biochar material with a zero-valent iron material in proportion, and carrying out ball milling treatment by using a planetary ball mill to obtain the modified biochar material. The preparation method has the advantages that the raw materials are easy to obtain, the operation is simple, the condition is mild, the operation environment pollution is small, the energy loss is less, a clean and efficient method is provided for the preparation of the modified biochar, and the prepared modified biochar sample can efficiently remove tetracycline TC in water.

Description

Technical Field

[0001] This invention relates to the fields of water pollution treatment and biochar preparation technology, specifically to a modified biochar material, its preparation method, and its application. Background Technology

[0002] Tetracycline is a broad-spectrum antibiotic that inhibits bacterial growth and has been widely used for antibacterial treatment in humans and animals. Tetracycline antibiotics (TCs) mainly include tetracycline (TC), chlortetracycline (CTC), and cyclamicin (DC), and are a common class of broad-spectrum antibiotics. Tetracycline is a yellow crystalline substance, widely used in various fields due to its good antibacterial activity, few side effects, and low cost and high efficacy, such as aquaculture, livestock growth promoters, and the prevention and treatment of human diseases. However, because tetracycline entering the human and animal body cannot be completely degraded, it is excreted through feces and urine due to its hydrophilic nature. Studies have shown that approximately 30.0% to 90.0% of antibiotics and their metabolites ultimately enter the surrounding environment, leading to high levels of tetracycline in aquatic environments.

[0003] Biochar, a solid material produced by the pyrolysis of biomass under anaerobic or oxygen-deficient atmospheres, possesses a unique porous structure and has become a research hotspot in the field of adsorbents. However, biochar has limited adsorption capacity and usually requires treatment to improve its adsorption performance. Heteroatom doping technology can alter the polarity of biochar materials by changing their framework structure and electron configuration, thereby further enhancing their adsorption capacity. Currently, the main atoms used for doping include boron, nitrogen, phosphorus, and sulfur. However, heteroatom-doped carbon materials used for adsorbing pollutants in water mainly focus on single-atom doping such as nitrogen doping, sulfur doping, or boron doping. Research on co-doping with other multiple atoms is very limited. This is mainly because heteroatom doping forms are diverse, and the lack of directional theoretical guidance for co-doping leads to complex and expensive development processes. Furthermore, there is currently no systematic introduction to multi-atom doping processes. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the purpose of this invention is to provide a modified biochar material, its preparation method, and its applications. This invention uses inexpensive and readily available cellulose and graphite as carbon sources, and prepares graphite biochar with zero-valent iron loading through a one-step co-pyrolysis process. The entire process is simple to operate, operates under mild conditions, consumes less energy, and generates minimal secondary pollution. This provides a clean and efficient method for preparing modified biochar, and the prepared modified biochar can efficiently remove tetracycline (TC) from water.

[0005] To achieve the above objectives, the present invention provides the following technical solution.

[0006] In a first aspect, a method for preparing a modified biochar material includes the following steps: (1) Graphite and cellulose are mixed in proportion, ground thoroughly, calcined in a tube furnace, kept at a certain temperature for a certain time and then cooled to obtain biochar material; (2) Mix biochar material and zero-valent iron material in a certain proportion. After mixing evenly, place the mixture in a planetary ball mill for ball milling to obtain modified biochar material.

[0007] In this invention, in step (1), the mass ratio of graphite to cellulose is 1:3 to 1:5.

[0008] In this invention, in step (1), the calcination conditions are: nitrogen atmosphere, calcination temperature of 680-720 ℃, and holding time of 25-40 min.

[0009] In this invention, the tube furnace is an SK-G06123K tube furnace, and the nitrogen flow rate is 90-120 cm³. 3 STP.min -1 .

[0010] In this invention, in step (2), the mass ratio of biochar material to zero-valent iron material is 2:1 to 1:3; the zero-valent iron material is elemental iron powder; most preferably, in step (2), the mass ratio of biochar material to zero-valent iron material is 1:1. The modified biochar material obtained under this ratio is used in the Fenton method to remove tetracycline (TC) from water, and has better catalytic activity and conductivity. It can provide sufficient active iron in the reaction process, while avoiding excessive carbon that leads to poor iron dispersion and maintaining higher removal efficiency.

[0011] In this invention, in step (2), the ball mill speed is 300-500 rpm and the ball milling time is 4-6 h; the material obtained after ball milling has a larger specific surface area and uniformly dispersed zero-valent iron, resulting in better removal of tetracycline.

[0012] Secondly, the present invention also provides a modified biochar material loaded with nano-zero valent iron prepared by the above preparation method.

[0013] Thirdly, this invention also provides the application of the above-mentioned modified biochar material in the removal of tetracycline (TC) from water. In application, the modified biochar material is used as a catalyst, and hydrogen peroxide as an oxidant, based on the Fenton reaction to degrade tetracycline (TC) in water. According to application test results, at pH 2-5, temperature 10-60℃, hydrogen peroxide 50-200 mmol / L, and catalyst dosage 0.1-1.5 g / mL, tetracycline solutions with an initial concentration of 50-150 mg / L exhibit excellent degradation effects.

[0014] Compared with the prior art, the beneficial effects of the present invention are as follows: This invention utilizes the co-carbonization of graphite and cellulose to prepare graphite biochar. By co-pyrolyzing cellulose with a certain mass fraction of graphite, a biochar with low crystallinity and rich in amorphous aromatic carbon structures, possessing numerous hydroxyl and C–O functional groups on its surface, can be obtained. Its specific surface area (measured by a 3Flex America Micromeritics analyzer) significantly increases from approximately 9.8 m² / g of cellulose biochar to approximately 262.5 m² / g, and its micropore area increases from near zero to approximately 104.8 m² / g. Simultaneously, the introduction of graphite significantly improves the electrical conductivity of the support, thereby enhancing the electron transfer efficiency of zero-valent iron (ZVFe) supported on it and its catalytic activity in Fenton-type reactions. The composite material obtained by uniformly loading ZVFe onto the aforementioned graphite biochar support can efficiently remove tetracycline (TC) from polluted water under suitable conditions, exhibiting good stability and reusability, demonstrating significantly superior overall performance compared to ordinary biochar or ZVFe materials without a graphite support. Attached Figure Description

[0015] Figure 1 Scanning electron microscope (SEM) images of the modified biochar material ZVI / G-BC-2 prepared in Example 3 and the comparative material, and energy dispersive X-ray spectra of ZVI / G-BC-2.

[0016] Figure 2 The X-ray diffraction (XRD) pattern of the modified biochar material ZVI / G-BC-2 prepared in Example 3.

[0017] Figure 3 Comparison of the tetracycline (TC) removal effects of the biochar materials with different carbon-iron ratios prepared in Examples 2-5 and the materials in Comparative Examples 1-3 under the conditions described in Example 6.

[0018] Figure 4 The graph shows the change in TC removal rate when ZVI / G-BC-2 prepared in Example 3 is used in multiple cycles. Detailed Implementation

[0019] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments and accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0021] All materials and instruments used in the following examples are commercially available, and the raw materials are analytical grade. In the following examples, if no... It should be noted that all data obtained are the average values ​​of three or more repeated trials.

[0022] The technical solutions and effects achieved by this application will be described in detail below through more specific embodiments.

[0023] Example 1

[0024] (1) Weighing and mixing raw materials Weigh out cellulose and graphite, with the graphite accounting for 20% of the total mass of graphite and cellulose, i.e., the graphite:cellulose mass ratio is 1:4. Place them in a mortar and mix and grind them thoroughly until they are evenly mixed.

[0025] (2) Preparation of graphite biochar by co-pyrolysis The mixture was loaded into a quartz boat and pushed into an SK-G06123K tube furnace under nitrogen protection (nitrogen flow rate...). 100 cm 3 STP·min -1 The temperature was raised to 700 °C and held for 30 min. After the reaction was completed, the furnace was cooled to room temperature, the solid product was removed, ground and sieved to obtain the graphite biochar carrier material, denoted as G-BC.

[0026] The preparation process of this embodiment is simple and can produce graphite biochar with stable structure, containing graphite phase and large specific surface area, which provides a good carrier for subsequent loading of zero-valent iron.

[0027] Example 2

[0028] Based on the G-BC prepared in Example 1, zero-valent iron-supported graphite biochar was prepared according to the following steps: (1) Weighing and mixing Weigh G-BC and zero-valent iron powder (ZVI) in a mass ratio of 2:1, and mix them thoroughly in a mortar until homogeneous.

[0029] (2) Ball mill load zero-valent iron The mixture was transferred to the grinding jar of a planetary ball mill, and the milling speed was set to 400 r·min. -1 The ball milling time was 5 hours. After ball milling, the sample was removed, gently ground, and sieved to obtain the zero-valent iron-supported graphite biochar composite material, denoted as ZVI / G-BC-1; the X-ray diffraction (XRD) pattern is shown below. Figure 2 As shown.

[0030] Example 3

[0031] This embodiment is the same as Embodiment 2, except that the mass ratio of G-BC to zero-valent iron is 1:1. The specific steps are as follows: (1) Weighing and mixing Weigh the G-BC obtained in Example 1 and zero-valent iron powder in a mass ratio of 1:1, mix them, and grind them thoroughly until uniform.

[0032] (2) Ball mill load The mixture was placed in the grinding jar of a planetary ball mill and the rotation speed was set to 400 r·min. -1 The sample was ball-milled for 5 hours. After cooling, it was removed, ground, and sieved to obtain the composite material, denoted as ZVI / G-BC-2. The specific surface area (measured by a 3FlexAmerica Micromeritics analyzer) and pore structure of the ZVI / G-BC-2 sample are shown in Table 1. Table 1. BET characterization results of ZVI / G-BC-2 samples

[0033] Scanning electron microscope image and energy-dispersive X-ray spectrum of ZVI / G-BC-2 are shown below. Figure 1 As shown, the X-ray diffraction (XRD) pattern is as follows: Figure 2 As shown.

[0034] Example 4 The preparation steps in this embodiment are the same as in Example 2, except that the carbon-iron ratio is changed: (1) Weighing and mixing Take G-BC and zero-valent iron powder in a mass ratio of 1:2, mix and grind them evenly.

[0035] (2) Ball mill load At 400 r·min -1 After ball milling for 5 hours, the material was cooled, removed, ground, and sieved to obtain the composite material, denoted as ZVI / G-BC-3. Its X-ray diffraction (XRD) pattern is as follows: Figure 2 As shown.

[0036] Example 5 The preparation steps in this embodiment are the same as in Example 2, except that the carbon-iron ratio is changed: (1) Weighing and mixing Take G-BC and zero-valent iron powder in a mass ratio of 1:3, mix and grind them evenly.

[0037] (2) Ball mill load At 400 r·min -1 After ball milling for 5 hours, the material was cooled, removed, ground, and sieved to obtain the composite material, denoted as ZVI / G-BC-4. Its X-ray diffraction (XRD) pattern is as follows: Figure 2 As shown.

[0038] Through Examples 2 to 5, four zero-valent iron-supported graphitic biochar materials ZVI / G-BC-1 to ZVI / G-BC-4 with different carbon-to-iron ratios can be obtained, providing a corresponding preparation process basis for the performance comparison of different materials in the attached figures.

[0039] Comparative Example 1 To compare the differences in material properties before and after the introduction of graphite, graphite-free cellulose biochar BC was prepared, and the steps are as follows: (1) Weigh the cellulose, weigh it evenly with an electronic balance, and then put it into a quartz boat; (2) Push the quartz boat into the SK-G06123K tube furnace, with a nitrogen flow rate of 100 cm³. 3 STP·min -1 Under the given conditions, the temperature was raised to 700 ℃ and held for 30 min. (3) After the reaction is completed, the solid is cooled to room temperature in the furnace, taken out, ground and sieved to obtain biochar material BC.

[0040] The comparative material does not contain the graphite phase, and its specific surface area and electrical conductivity are significantly lower than those of the G-BC obtained in Example 1.

[0041] Comparative Example 2 To further highlight the superiority of the "graphite-supported zero-valent iron" material of this invention, a graphite-free biochar-based zero-valent iron material ZVI / BC was prepared as a comparison: (1) Weigh the BC and zero-valent iron powder prepared in Comparative Example 1 at a mass ratio of 1:1, mix and grind them evenly; (2) Load the mixture into a ball mill jar and mill at 400 r·min -1 5 hours in the ball mill; (3) After ball milling, the material is taken out, ground, and sieved to obtain a graphite-free zero-valent iron biochar composite material, denoted as ZVI / BC.

[0042] Under the same process conditions, zero-valent iron in ZVI / BC tends to agglomerate and has poor dispersibility, resulting in lower conductivity and active site utilization compared to the ZVI / G-BC material of this invention.

[0043] Performance testing Using ZVI / G-BC-2 prepared in Example 3 as a catalyst, its performance in removing tetracycline (TC) from water in a Fenton-like system was investigated.

[0044] 1. Degradation performance (1) Preparation of reaction solution: Prepare an aqueous solution of TC with a mass concentration of 60 mg / L. Measure 250 mL and add it to a 500 mL beaker. Adjust the pH of the solution to 3 with 0.1 mol / L HCl or NaOH solution.

[0045] (2) Addition of catalyst and oxidant ZVI / G-BC-2 was added to the above TC solution at a dosage of 0.2 g / L, and the solution was incubated in a constant temperature shaker at 25°C and 150 r·min. -1 Shake for 10 minutes under the specified conditions to reach adsorption equilibrium; then add a 50 mM H2O2 solution all at once and start timing.

[0046] (3) Sampling and analysis Samples were taken periodically during the reaction, filtered through a 0.22 μm filter membrane, and the remaining concentration of TC in the solution was determined using high-performance liquid chromatography (HPLC) to calculate the removal rate. The XRD pattern of the sample after the reaction is shown below. Figure 2 As shown.

[0047] Under the same reaction conditions, ZVI / BC, G-BC, graphite alone, and zero-valent iron alone were used as catalysts in comparative experiments. The results are as follows: Figure 3 As shown, the following is displayed: Graphite alone has almost no degradation effect on TC; G-BC mainly exhibits physical adsorption with limited removal rate; although ZVI / BC can activate H2O2 to some extent, its removal rate is significantly lower than ZVI / G-BC-2 due to poor conductivity and ZVI dispersion; ZVI / G-BC-2 of this invention has the highest TC removal rate under the same conditions, and its kinetic rate constant is significantly greater than that of the above-mentioned comparative materials, which fully demonstrates the synergistic effect between graphite biochar support and zero-valent iron; when ZVI / G-BC-2 reacts for 120 min under the above conditions, the TC removal rate can reach about 99%, indicating that ZVI / G-BC-2 prepared by this invention has excellent Fenton-like catalytic degradation performance.

[0048] 2. Recyclability After the above degradation reaction was completed, ZVI / G-BC-2 was recovered by filtration, washed with deionized water, dried at 60 °C, and used for the next cycle of experiments. Figure 4As shown, after being reused five times under the same conditions, the TC removal rate remained above 90%, indicating that the material has good stability and reusability.

Claims

1. A method for preparing a modified biochar material, characterized in that, Includes the following steps: (1) Graphite and cellulose are mixed in proportion, ground thoroughly, calcined in a tube furnace, kept at a certain temperature for a certain time and then cooled to obtain biochar material; (2) Mix biochar material and zero-valent iron material in a certain proportion. After mixing evenly, place the mixture in a planetary ball mill for ball milling to obtain modified biochar material.

2. The preparation method according to claim 1, characterized in that, In step (1), the mass ratio of graphite to cellulose is 1:3 to 1:

5.

3. The preparation method according to claim 1, characterized in that, In step (1), the roasting conditions are: nitrogen atmosphere, roasting temperature of 680-720 ℃, and holding time of 25-40 min.

4. The preparation method according to claim 3, characterized in that, The tube furnace is an SK-G06123K tube furnace with a nitrogen flow rate of 90-120 cm³. 3 STP.min -1 .

5. The preparation method according to claim 1, characterized in that, In step (2), the mass ratio of biochar material to zero-valent iron material is 2:1 to 1:3; Zero-valent iron material is elemental iron powder.

6. The preparation method according to claim 1, characterized in that, In step (2), the ball mill speed is 300-500 rpm and the ball milling time is 4-6 h.

7. A modified biochar material prepared by the preparation method according to any one of claims 1-6.

8. The application of the modified biochar material according to claim 7 in the removal of tetracycline (TC) from water.

9. The application according to claim 8, characterized in that, In application, modified biochar material is used as a catalyst and hydrogen peroxide as an oxidant to degrade tetracycline (TC) in water based on the Fenton reaction.

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