Preparation Method and Application of Magnetite-Loaded Biochar Catalyst

Abstract

The present invention provides a preparation method and application of a magnetite-loaded biochar catalyst, belonging to the technical field of catalysts. The preparation method is to mix wheat straw powder obtained by crushing wheat straw and shell powder obtained by crushing shells, add ferrous sulfate, ferric chloride and water under the protection of an inert gas, mix well, then dropwise add ammonia water to react, precipitate, filter, and the obtained precipitate is dried and pyrolyzed to obtain the magnetite-loaded biochar catalyst; the magnetite-loaded biochar catalyst is used for treating wastewater. The magnetite-loaded biochar catalyst prepared by the present invention can effectively adsorb and degrade benzo[a]pyrene in coking wastewater, and the whole preparation process is simple and environmentally friendly, suitable for industrial production.

Description

Technical Field

[0001] The present invention relates to the preparation of a biochar catalyst, and particularly to a preparation method and application of a magnetite-loaded biochar catalyst. Background Art

[0002] Benzo[a]pyrene is a polycyclic aromatic hydrocarbon that widely exists in coal tar, fuel oil, coal, and coking wastewater. Due to its carcinogenic and mutagenic properties, it has been identified as one of the important pollutants to the environment and health. The components contained in coking wastewater are relatively complex, and one of the main pollutants is benzo[a]pyrene. The benzo[a]pyrene contained in coking wastewater is difficult to remove by conventional biochemical methods, so it is difficult for the coking wastewater treated by biochemical methods to meet the discharge standards. In the National Standard GB16171-2012 Discharge Standard of Pollutants for Coking Chemical Industry, the discharge standard of benzo[a]pyrene is specified to be lower than 0.03 μg / L. With the increasingly high requirements of the country for the discharge of coking wastewater, the in-depth treatment of coking wastewater to reduce the concentration of benzo[a]pyrene has become an urgent problem to be solved in the fields of steelmaking, coking, and power generation. Currently, there are mainly three treatment methods for benzo[a]pyrene in coking wastewater: 1. Physical method. The physical method of treating wastewater uses the adsorbability of adsorbents to temporarily remove pollutants from the wastewater without completely converting them into harmless substances. The most commonly used adsorbents are: activated carbon, clay adsorbents, adsorbents prepared from waste, coal-based adsorbents, and iron-based adsorbents, but they have not been widely promoted and applied due to high costs. 2. Biological method. Microbial metabolism is an effective method for removing benzo[a]pyrene in polluted environments, and biodegradation is also known as bioreclamation and bioremediation. This method includes aerobic and anaerobic methods. Although the aerobic treatment method has a relatively high removal rate and low cost, it is not conducive to the degradation of macromolecular substances, and the removal rate is only about 50%. Therefore, the effect of removing benzo[a]pyrene usually cannot meet the requirements. Compared with aerobic treatment, the anaerobic biological treatment method can significantly degrade complex macromolecular substances in a suitable environment and can play a superior role in treating coking wastewater. However, the anaerobic treatment of coking wastewater is often accompanied by a foul smell, and the efficiency of using it alone is not high, and it is also difficult to meet the discharge standards. 3. Chemical method. The chemical method includes photo-oxidation degradation method and chemical oxidation degradation method. Photo-oxidation degradation is that the pollutants in coking wastewater are oxidized by free radicals in the medium or by ozone under the condition of light irradiation, but this process is affected by many factors, such as light intensity, types and amounts of free radicals, ozone concentration, and temperature, etc. Due to the difficulty of light penetrating the coking wastewater quality, the efficiency of this method is relatively low. The chemical oxidation method can be divided into three types according to the types of oxidants: chlorine oxidation method, hydrogen peroxide oxidation method, and ozone oxidation method. Its main degradation process is that ·OH generated by the oxidant gradually oxidizes the target pollutant until it is completely mineralized. There are many types of oxidants, such as NaClO, O 3 、O 2 、H 2 O2 , ClO 2 etc. However, the chlorination oxidation method is prone to produce smaller molecules with greater danger, such as organic halides like chloroform that can cause animal tumors and damage the central nervous system, and it has now been gradually phased out; the cost of ozone treatment is very high, and ozone oxidation treatment alone cannot be used as an energy-saving and efficient coking wastewater treatment method. The typical representative of the hydrogen peroxide oxidation technology is the Fenton method, which forms a reagent with strong oxidizing properties by adding H 2 O 2 and Fe 2+ in a reaction system in a specific ratio, that is, under suitable conditions, the two react with each other to generate ·OH free radicals with a high oxidation-reduction potential to oxidize benzo[a]pyrene. However, the traditional Fenton reaction system has relatively strict requirements for reaction conditions. How to improve the strict requirements of the Fenton reaction system for reaction conditions and improve the treatment efficiency of benzo[a]pyrene has always been the focus of research and development by those skilled in the art. Summary of the Invention

[0003] In view of the above problems, the present invention provides a preparation method and application of a magnetite-loaded biochar catalyst.

[0004] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0005] A preparation method of a magnetite-loaded biochar catalyst, comprising the following steps:

[0006] S1. After wheat straw is crushed, wheat straw powder is obtained;

[0007] After shells are crushed, shell powder is obtained;

[0008] S2. Wheat straw powder and shell powder with a weight ratio of 8-12:1 are taken and mixed to obtain a mixed powder;

[0009] S3. Under the protection of an inert gas, the mixed powder is taken and ferrous sulfate, ferric chloride and water are added, and after mixing evenly, a slightly excessive amount of ammonia water is added for reaction, precipitation, and filtration. After the obtained precipitate is dried, a solid loading mixture is obtained;

[0010] S4. Under the protection of an inert gas, the solid loading mixture is pyrolyzed to obtain the magnetite-loaded biochar catalyst.

[0011] Further, in step S3, the molar ratio of ferrous sulfate to ferric chloride is 1:2-2.1.

[0012] Further, in step S3, the weight molar ratio of the mixed powder to ferrous sulfate is 100 g:0.035-0.038 mol.

[0013] Further, in step S3, the weight molar ratio of the mixed powder to ammonia water is 100 g: 12.05 - 12.2 mol.

[0014] Further, in step S4, the pyrolysis is carried out by heating at a heating rate of 5 °C / min to 400 - 450 °C, then maintaining the temperature at 400 - 450 °C for pyrolysis for 6 - 7 h, and then cooling to room temperature at a cooling rate of 5 °C / min.

[0015] Further, in step S1, the wheat straw powder is obtained by pulverizing wheat straw and passing it through a 100 - 120 mesh sieve;

[0016] The shell powder is obtained by pulverizing shells and passing it through a 100 - 120 mesh sieve;

[0017] In step S4, after the solid - loaded mixture is pyrolyzed, it needs to be ground and passed through a 100 - 120 mesh sieve.

[0018] An application of the above - mentioned magnetite - loaded biochar catalyst in wastewater treatment.

[0019] Further, the method of the application is to take the wastewater to be treated, add the magnetite - loaded biochar catalyst and hydrogen peroxide, carry out the Fenton reaction. After the reaction is completed, the degradation of substances such as benzo[a]pyrene in the system can be completed, and the treated wastewater can be obtained.

[0020] Further, the added weight of the magnetite - loaded biochar catalyst is 1.5 - 2% of the volume of the wastewater to be treated.

[0021] Further, after the wastewater treatment is completed, the magnetite - loaded biochar catalyst can be recycled under the action of a magnetic field and used in the next wastewater treatment process.

[0022] The beneficial effects of the preparation method and application of the magnetite - loaded biochar catalyst of the present invention are as follows:

[0023] Biochar is a kind of porous carbonized material, which has the characteristics of large specific surface area, complex pore structure, rich ash content, strong conductivity, and rich surface functional groups. Its adsorption performance depends to a large extent on its physical properties (such as surface area and pore structure) and chemical properties (such as functional groups), and these properties are affected by its pyrolysis conditions and raw material types. The present invention modifies it by using a specific proportion of wheat straw powder combined with shell powder and cooperating with a small amount of alkaline substance ammonia water, and pyrolyzing at a specific temperature, which can effectively increase the active sites and specific surface area on the surface of the prepared biochar. At the same time, since the shell powder contains a large amount of substances such as calcium carbonate, sodium oxide, silicon dioxide, magnesium oxide, and aluminum oxide, combined with the modification effect of a small amount of ammonia water on the biochar, it can effectively increase the content of oxygen functional groups of the prepared biochar, thereby effectively improving the adsorption capacity of the prepared magnetite - loaded biochar catalyst;

[0024] Through a specific process, the present invention uses biochar to load nano-ferroferric oxide, which can directly fix nano-ferroferric oxide particles in the porous medium formed by biochar. And due to the strong adsorption performance of biochar, benzo[a]pyrene in wastewater can be adsorbed into the porous medium of biochar, and then nano-ferroferric oxide is used to promote H 2 O 2 to generate ·OH, so as to fully degrade the adsorbed benzo[a]pyrene and effectively reduce the content of benzo[a]pyrene in wastewater;

[0025] Furthermore, since shell powder is added during the preparation of biochar in the present invention, a certain amount of calcium oxide, sodium oxide, magnesium oxide, aluminum oxide and other substances will also be loaded in the porous medium of biochar after pyrolysis. These substances will further activate ·OH and strengthen the degradation of benzo[a]pyrene;

[0026] By using biochar to load nano-ferroferric oxide, the present invention can also utilize the strong magnetism of ferroferric oxide to recover the biochar catalyst loaded on magnetite under the action of an external magnetic field, thereby improving its reuse rate;

[0027] The biochar catalyst loaded with magnetite prepared by the present invention can effectively adsorb and degrade benzo[a]pyrene in coking wastewater, and the whole preparation process is simple and environmentally friendly, which is suitable for industrial production. Specific Embodiments

[0028] The technical solutions in the embodiments of the present invention will be described clearly and completely below. Many specific details are set forth in the following description in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar promotions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0029] Example 1 Preparation Method and Application of a Biochar Catalyst Loaded with Magnetite

[0030] This example is a preparation method and application of a biochar catalyst loaded with magnetite, which specifically includes the following steps:

[0031] I. Preparation Method of Biochar Catalyst Loaded with Magnetite

[0032] S1. Take wheat straw, remove impurities, dry and crush it, and pass through a 100-120 mesh sieve (100 mesh in this example) to obtain wheat straw powder;

[0033] Take shells, remove impurities, crush them, and pass through a 100-120 mesh sieve (100 mesh in this example) to obtain shell powder;

[0034] S2. Mix wheat straw powder and shell powder at a weight ratio of 8 - 12:1 (the weight ratio of wheat straw powder to shell powder in this example is 10:1) to obtain a mixed powder;

[0035] S3. Under nitrogen protection, take 100 g of the mixed powder, add 9.73 g (0.035 mol) of FeSO 4 ·7H 2 O and 18.92 g (0.07 mol) of FeCl 3 ·6H 2 O, add 2 L of deionized water, continuously stir the obtained system at a rotation speed of 150 - 200 r / min for 0.5 - 1 h (the rotation speed in this example is 150 r / min and the continuous stirring time is 1 h), add a slightly excessive amount of 25 wt% NH 3 ·H 2 O (12.05 mol) as a co - precipitating agent, slowly drop it into the system. After dropping, maintain the above rotation speed and continue stirring for 1 - 2 h (maintain the rotation speed of 150 r / min and continue stirring for 1 h in this example), then let it stand until complete precipitation, filter. Place the obtained precipitate in a vacuum drying oven and dry it at 50 °C for 12 h to obtain a solid - loaded mixture;

[0036] S4. Take the solid - loaded mixture and place it in a tube furnace. Under nitrogen protection, heat it at a heating rate of 5 °C / min to 400 - 450 °C for pyrolysis (heat it to 450 °C in this example), and maintain pyrolysis at 400 - 450 °C for 6 - 7 h (the pyrolysis temperature is 450 °C and the time is 6 h in this example). Then cool it to room temperature at a cooling rate of 5 °C / min, take it out, grind it, and pass it through a 100 - mesh sieve to obtain a magnetite - loaded biochar catalyst, labeled as T1.

[0037] II. Application of the magnetite - loaded biochar catalyst:

[0038] Use the coking wastewater treated by the secondary sedimentation tank as the wastewater to be treated. Add 1.5 - 2% (by weight - volume percentage) of the magnetite - loaded biochar catalyst T1 (the added weight of the magnetite - loaded biochar catalyst T1 in this example is 1.5% of the volume of the wastewater to be treated) to it, and add 2.3 - 2.8% (by volume percentage) of 30% H 2 O 2 (the added volume of 30% hydrogen peroxide in this example is 2.5% of the volume of the wastewater to be treated). Conduct a Fenton reaction at room temperature for more than 30 min (the Fenton reaction time is 40 min in this example), and then the degradation of substances such as benzo[a]pyrene in the obtained system can be completed to obtain the treated wastewater.

[0039] After the wastewater treatment, under the action of a magnetic field, magnetite-loaded biochar catalyst T1 is recycled. The recycled magnetite-loaded biochar catalyst T1 can be reused as a catalyst in another batch of wastewater to be treated. In this example, the magnetite-loaded biochar catalyst T1 was repeated 5 times. It should be noted that when the recycled magnetite-loaded biochar catalyst T1 is insufficient, it can be supplemented with unused magnetite-loaded biochar catalyst T1 according to the required dosage.

[0040] Among them, the first batch of wastewater to be treated contained 2.53 μg / L of benzo[a]pyrene, 293 mg / L of COD, 7.92 mg / L of ammonia nitrogen, 10.35 mg / L of total nitrogen, and 2.43 mg / L of total cyanide;

[0041] The wastewater after the first treatment contained 0.001 μg / L of benzo[a]pyrene, 84 mg / L of COD, 0.33 mg / L of ammonia nitrogen, 0.41 mg / L of total nitrogen, and 0.01 mg / L of total cyanide;

[0042] The second batch of wastewater to be treated contained 2.49 μg / L of benzo[a]pyrene, 289 mg / L of COD, 8.12 mg / L of ammonia nitrogen, 10.57 mg / L of total nitrogen, and 2.36 mg / L of total cyanide;

[0043] The wastewater after the second treatment contained 0.001 μg / L of benzo[a]pyrene, 79 mg / L of COD, 0.37 mg / L of ammonia nitrogen, 0.43 mg / L of total nitrogen, and 0.02 mg / L of total cyanide;

[0044] The third batch of wastewater to be treated contained 2.57 μg / L of benzo[a]pyrene, 281 mg / L of COD, 7.84 mg / L of ammonia nitrogen, 9.98 mg / L of total nitrogen, and 2.56 mg / L of total cyanide;

[0045] The wastewater after the third treatment contained 0.002 μg / L of benzo[a]pyrene, 82 mg / L of COD, 0.42 mg / L of ammonia nitrogen, 0.53 mg / L of total nitrogen, and 0.02 mg / L of total cyanide;

[0046] The fourth batch of wastewater to be treated contained 2.64 μg / L of benzo[a]pyrene, 296 mg / L of COD, 8.07 mg / L of ammonia nitrogen, 10.46 mg / L of total nitrogen, and 2.51 mg / L of total cyanide;

[0047] The wastewater after the fourth treatment contained 0.002 μg / L of benzo[a]pyrene, 81 mg / L of COD, 0.46 mg / L of ammonia nitrogen, 0.57 mg / L of total nitrogen, and 0.02 mg / L of total cyanide;

[0048] The fifth wastewater to be treated contains 2.54 μg / L of benzo[a]pyrene, 283 mg / L of COD, 8.04 mg / L of ammonia nitrogen, 10.57 mg / L of total nitrogen, and 2.45 mg / L of total cyanide;

[0049] The fifth treated wastewater contains 0.003 μg / L of benzo[a]pyrene, 85 mg / L of COD, 0.49 mg / L of ammonia nitrogen, 0.68 mg / L of total nitrogen, and 0.03 mg / L of total cyanide.

[0050] Preparation methods and applications of magnetite-loaded biochar catalysts in Examples 2 to 5

[0051] Examples 2 to 5 are respectively preparation methods and applications of a magnetite-loaded biochar catalyst. Their steps are basically the same as those in Example 1, except for the different process parameters. For details, see Table 1:

[0052] Table 1 List of process parameters in Examples 2 to 5

[0053]

[0054]

[0055] The process steps and parameters of other parts in Examples 2 to 5 are the same as those in Example 1, and the magnetite-loaded biochar catalysts in each example can be recycled under the action of a magnetic field.

[0056] Experimental Example 1 Comparative test

[0057] Comparative tests 1 to 7 are comparative tests on the preparation methods and applications of the magnetite-loaded biochar catalyst in Example 1. The processes and raw material dosages used are also basically the same, except for:

[0058] In step S2 of Comparative Example 1, wheat straw powder and shell powder are mixed in a weight ratio of 4:1, and the finally prepared magnetite-loaded biochar catalyst is labeled as DT1. The wastewater is treated with the magnetite-loaded biochar catalyst DT1 according to the application method in Example 1. Among them, the wastewater to be treated contains 2.57 μg / L of benzo[a]pyrene, 286 mg / L of COD, 7.87 mg / L of ammonia nitrogen, 10.45 mg / L of total nitrogen, and 2.41 mg / L of total cyanide; the treated wastewater contains 0.008 μg / L of benzo[a]pyrene, 137 mg / L of COD, 1.27 mg / L of ammonia nitrogen, 1.58 mg / L of total nitrogen, and 0.43 mg / L of total cyanide;

[0059] In step S2 of Comparative Example 2, wheat straw powder and shell powder with a weight ratio of 16:1 were mixed, and the finally prepared magnetite-loaded biochar catalyst was labeled as DT2; the magnetite-loaded biochar catalyst DT2 was used to treat wastewater according to the application method in Example 1. Among them, the wastewater to be treated contained 2.47 μg / L of benzo[a]pyrene, 296 mg / L of COD, 8.03 mg / L of ammonia nitrogen, 10.54 mg / L of total nitrogen, and 2.36 mg / L of total cyanide; the treated wastewater contained 0.006 μg / L of benzo[a]pyrene, 124 mg / L of COD, 1.13 mg / L of ammonia nitrogen, 1.36 mg / L of total nitrogen, and 0.37 mg / L of total cyanide;

[0060] In step S3 of Comparative Example 3, only the dosage of FeSO 4 ·7H 2 O was changed to 0.02 mol, and the dosage of FeCl 3 ·6H 2 O was changed to 0.04 mol. The dosages of other raw materials and the process steps and parameters remained unchanged. The finally prepared magnetite-loaded biochar catalyst was labeled as DT3; the magnetite-loaded biochar catalyst DT3 was used to treat wastewater according to the application method in Example 1. Among them, the wastewater to be treated contained 2.57 μg / L of benzo[a]pyrene, 299 mg / L of COD, 7.96 mg / L of ammonia nitrogen, 10.42 mg / L of total nitrogen, and 2.46 mg / L of total cyanide; the treated wastewater contained 0.187 μg / L of benzo[a]pyrene, 156 mg / L of COD, 1.79 mg / L of ammonia nitrogen, 2.47 mg / L of total nitrogen, and 0.59 mg / L of total cyanide;

[0061] In step S3 of Comparative Example 4, only the dosage of FeSO 4 ·7H 2 O was changed to 0.08 mol, and the dosage of FeCl 3 ·6H 2 O was changed to 0.16 mol. The dosages of other raw materials and the process steps and parameters remained unchanged. The finally prepared magnetite-loaded biochar catalyst was labeled as DT4; the magnetite-loaded biochar catalyst DT4 was used to treat wastewater according to the application method in Example 1. Among them, the wastewater to be treated contained 2.51 μg / L of benzo[a]pyrene, 283 mg / L of COD, 7.89 mg / L of ammonia nitrogen, 10.53 mg / L of total nitrogen, and 2.51 mg / L of total cyanide; the treated wastewater contained 0.067 μg / L of benzo[a]pyrene, 134 mg / L of COD, 1.43 mg / L of ammonia nitrogen, 2.58 mg / L of total nitrogen, and 0.66 mg / L of total cyanide;

[0062] In step S4 of Comparative Example 5, the pyrolysis temperature was 300 °C, and the finally prepared magnetite-loaded biochar catalyst was labeled as DT5; the magnetite-loaded biochar catalyst DT5 was used to treat wastewater according to the application method in Example 1. Among them, the wastewater to be treated contained 2.52 μg / L of benzo[a]pyrene, 294 mg / L of COD, 7.86 mg / L of ammonia nitrogen, 10.38 mg / L of total nitrogen, and 2.46 mg / L of total cyanide; the treated wastewater contained 0.023 μg / L of benzo[a]pyrene, 121 mg / L of COD, 1.35 mg / L of ammonia nitrogen, 1.57 mg / L of total nitrogen, and 0.12 mg / L of total cyanide.

[0063] In step S4 of Comparative Example 6, the pyrolysis temperature was 600 °C, and the finally prepared magnetite-loaded biochar catalyst was labeled as DT6; the magnetite-loaded biochar catalyst DT6 was used to treat wastewater according to the application method in Example 1. Among them, the wastewater to be treated contained 2.44 μg / L of benzo[a]pyrene, 281 mg / L of COD, 7.98 mg / L of ammonia nitrogen, 10.42 mg / L of total nitrogen, and 2.37 mg / L of total cyanide; the treated wastewater contained 0.054 μg / L of benzo[a]pyrene, 138 mg / L of COD, 1.44 mg / L of ammonia nitrogen, 2.09 mg / L of total nitrogen, and 0.27 mg / L of total cyanide.

[0064] In step S3 of Comparative Example 7, only the dosage of NH 3 ·H 2 O was changed to 13 mol, and the dosages of other raw materials and the process steps and parameters remained unchanged. The finally prepared magnetite-loaded biochar catalyst was labeled as DT7; the magnetite-loaded biochar catalyst DT7 was used to treat wastewater according to the application method in Example 1. Among them, the wastewater to be treated contained 2.54 μg / L of benzo[a]pyrene, 298 mg / L of COD, 8.04 mg / L of ammonia nitrogen, 10.61 mg / L of total nitrogen, and 2.37 mg / L of total cyanide; the treated wastewater contained 0.008 μg / L of benzo[a]pyrene, 105 mg / L of COD, 0.74 mg / L of ammonia nitrogen, 1.25 mg / L of total nitrogen, and 0.09 mg / L of total cyanide.

[0065] Comparing the treatment effects of the wastewater to be treated in Example 1 and Comparative Examples 1-7, it can be clearly seen that just changing a single process parameter such as the raw material ratio and pyrolysis temperature in the process of preparing the magnetite-loaded biochar catalyst will lead to a decrease in the performance of the magnetite-loaded biochar catalyst, and thus affect the removal effect of substances such as benzo[a]pyrene in coking wastewater. The magnetite-loaded biochar catalyst prepared by the present invention can well remove substances such as benzo[a]pyrene in coking wastewater.

[0066] Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the scope of protection of the present invention.

Claims

1. Preparation method of magnetite-loaded biochar catalyst, Characterized in that, The preparation method includes the following steps: S1. After wheat straw is crushed, wheat straw powder is obtained; After shells are crushed, shell powder is obtained; S2. Wheat straw powder and shell powder with a weight ratio of 8-12:1 are mixed to obtain a mixed powder; S3. Under the protection of inert gas, ferrous sulfate, ferric chloride and water are added to the mixed powder. After mixing evenly, slightly excessive ammonia water is added dropwise for reaction, precipitation, and filtration. The obtained precipitate is dried to obtain a solid-loaded mixture; the molar ratio of ferrous sulfate to ferric chloride is 1:2-2.1; the weight molar ratio of the mixed powder to ferrous sulfate is 100g:0.035-0.038mol; the weight molar ratio of the mixed powder to ammonia water is 100g:12.05-12.2mol; S4. Under the protection of inert gas, the solid-loaded mixture is pyrolyzed to obtain the magnetite-loaded biochar catalyst; The pyrolysis is carried out by heating at a heating rate of 5°C / min to 400-450°C, then maintaining the pyrolysis at 400-450°C for 6-7h, and then cooling to room temperature at a cooling rate of 5°C / min.

2. The preparation method of the magnetite-loaded biochar catalyst according to claim 1, Characterized in that, In step S1, the wheat straw powder is obtained by crushing wheat straw and passing through a 100-120 mesh sieve; The shell powder is obtained by crushing shells and passing through a 100-120 mesh sieve; In step S4, after the solid-loaded mixture is pyrolyzed, it also needs to be ground and passed through a 100-120 mesh sieve.

3. Application of the magnetite-loaded biochar catalyst prepared by the preparation method according to claim 1 or 2 in treating wastewater.

4. The application according to claim 3, Characterized in that, The method of the application is to take the wastewater to be treated, add the magnetite-loaded biochar catalyst and hydrogen peroxide, carry out Fenton reaction, and after the reaction is completed, obtain the treated wastewater.

5. The application according to claim 3 or 4, Characterized in that, After the wastewater treatment is completed, the magnetite-loaded biochar catalyst is recovered under the action of a magnetic field and used in the next wastewater treatment process.

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