A method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar

Abstract

This invention belongs to the field of water treatment technology, specifically disclosing a method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar. The invention involves mixing manganese oxide-modified biochar, hydrogen peroxide, and tetracycline-containing wastewater to obtain a mixed solution, which is then reacted to treat the tetracycline-containing wastewater. The mass concentration of the manganese oxide-modified biochar in the mixed solution is 1-2 g / L. This invention utilizes manganese oxide-modified biochar for adsorption-synergistic Fenton-like reactions to remove typical antibiotic tetracyclines from water, exhibiting excellent tetracycline adsorption and catalytic performance.

Description

Technical Field

[0001] This invention relates to the field of water treatment technology, and in particular to a method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar. Background Technology

[0002] Antibiotics are a class of secondary metabolites produced by microorganisms or plants and animals. They inhibit the growth of pathogens or exert bactericidal effects by interfering with key physiological processes in pathogen cells. Due to their high efficiency and specificity, antibiotics have been widely used in clinical medicine, animal husbandry, and many other fields to treat human and animal diseases and promote animal growth. Antibiotics are mainly classified into tetracyclines, sulfonamides, macrolides, chloramphenicols, and fluoroquinolones. Tetracycline antibiotics are widely used due to their low cost and significant efficacy, resulting in the generation of large amounts of wastewater containing tetracycline substances.

[0003] Currently, methods for removing tetracycline-containing wastewater include membrane separation, biological treatment, adsorption, and advanced oxidation processes. Advanced oxidation processes are among the most promising technologies for treating tetracycline-containing wastewater because they generate highly oxidizing free radicals (such as ·OH and ·SO4). - Biochar can completely degrade tetracycline molecules into smaller molecules and even mineralize them into CO2 and H2O, avoiding secondary pollution. Studies have found that biochar can not only act as an adsorbent for pollutants in water treatment but also as a catalyst to activate oxidizing substances, thereby degrading organic pollutants. However, the removal capacity of biochar is mainly affected by the source of raw materials and their preparation and modification methods. Based on these characteristics, researchers are increasingly focusing on using locally sourced biomass raw materials to prepare high-performance carbon materials and exploring their modification methods to significantly improve their adsorption and catalytic performance, thus demonstrating excellent application prospects in treating organic pollutants in water.

[0004] Biochar produced from different types of biomass raw materials exhibits varying physicochemical properties and adsorption capacities. Under the same preparation conditions, bamboo and rapeseed stalk biochar, due to differences in ash and fiber content, possess better pore characteristics and higher relative concentrations of aromatic rings than cotton stalk and rice husk biochar, thus demonstrating better adsorption effects for organic matter. Yan et al. found that bamboo char has larger pore sizes and volumes, resulting in stronger adsorption capacity compared to amorphous palm char with less porous structure. Furthermore, bamboo char has a higher proportion of oxygen-containing (polar) functional groups, which, due to polarization, easily removes organic matter through electrostatic and hydrophobic interactions. Lu et al.'s research indicates that sheep manure contains a large amount of plant fiber, which can reduce the H / C and O / C ratios in manure-based biochar, thereby producing higher aromaticity and polarity. Under acidic conditions, this type of biochar carries a positive charge and can remove organic pollutants from aqueous solutions through electrostatic adsorption.

[0005] Therefore, how to provide a method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar and achieve excellent tetracycline degradation effect is an urgent problem to be solved in this field. Summary of the Invention

[0006] In view of this, the present invention provides a novel method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar, and achieves excellent degradation effect.

[0007] To achieve the above objectives, the present invention adopts the following technical solution: A method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar includes the following steps: Manganese oxide-modified biochar, hydrogen peroxide, and tetracycline-containing wastewater are mixed to obtain a mixed solution, which is then reacted to achieve the treatment of tetracycline-containing wastewater. The mass concentration of the manganese oxide-modified biochar in the mixed solution is 1~2 g / L.

[0008] Preferably, the molar concentration of hydrogen peroxide in the mixed solution is ≥200 mmol / L.

[0009] Preferably, the concentration of tetracycline in the tetracycline-containing wastewater is 10~50 mg / L.

[0010] Preferably, the reaction temperature is 25~40℃, the reaction time is 8~10h, and the pH value of the reaction system is 5~11.

[0011] Preferably, the method for preparing the manganese oxide modified biochar includes the following steps: 1) Mix coconut shell biochar with potassium permanganate solution and impregnate to obtain coconut shell biochar loaded with potassium permanganate; 2) Coconut shell biochar loaded with potassium permanganate was roasted to obtain manganese oxide modified biochar.

[0012] Preferably, the mass-to-volume ratio of coconut shell biochar to potassium permanganate solution in step 1) is 0.5~1g:10mL; The molar concentration of the potassium permanganate solution is 0.1 mol / L.

[0013] Preferably, the immersion temperature in step 1) is 20~25℃ and the time is 4h.

[0014] Preferably, the roasting temperature in step 2) is 400°C and the roasting time is 90~120 min.

[0015] As can be seen from the above technical solution, compared with the prior art, the present invention has the following beneficial effects: A low-cost manganese oxide-modified biochar was prepared using potassium permanganate impregnation and high-temperature pyrolysis, exhibiting excellent surface pore structure and oxygen-containing functional groups. The tetracycline removal process of the manganese oxide-modified biochar / H₂O₂ synergistic system involves both adsorption and oxidative degradation, but oxidation is dominant. It demonstrates excellent removal performance (removal rate greater than 85%) over a wide pH range (pH=5~11), exhibiting superior removal capacity and anti-interference ability. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on the provided drawings without creative effort.

[0017] Figure 1 SEM images of biochar modified at different calcination temperatures are shown. Figure 1 In the equation, a~f correspond to 300℃, 400℃, 500℃, 600℃, 700℃, and 800℃ respectively. Figure 2 The results of manganese oxide-modified biochar at different calcination temperatures on the treatment of tetracycline-containing wastewater; Figure 3 The treatment results of tetracycline-containing wastewater with different dosages of manganese oxide-modified biochar; Figure 4 The results of treating tetracycline-containing wastewater with different hydrogen peroxide concentrations; Figure 5 The treatment results of tetracycline-containing wastewater at different pH values ​​in different systems; Figure 6 The treatment results of tetracycline-containing wastewater at different reaction temperatures; in, Figures 2-6 In the graph, 'a' represents the concentration change over time, and 'b' represents the characteristic absorption peak (wavenumber) of TC at 8 h. Detailed Implementation

[0018] This invention provides a method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar, comprising the following steps: Manganese oxide-modified biochar, hydrogen peroxide, and tetracycline-containing wastewater are mixed to obtain a mixed solution, which is then reacted to achieve the treatment of tetracycline-containing wastewater.

[0019] In this invention, the mass concentration of the manganese oxide modified biochar in the mixed solution is 1~2 g / L, specifically 1.2 g / L, 1.4 g / L, 1.5 g / L, 1.6 g / L, or 1.8 g / L.

[0020] In this invention, the molar concentration of hydrogen peroxide in the mixed solution is ≥200 mmol / L, specifically 220 mmol / L, 240 mmol / L, 250 mmol / L, 260 mmol / L, 280 mmol / L, or 300 mmol / L.

[0021] In this invention, the concentration of tetracycline in the tetracycline-containing wastewater is 10~50 mg / L, specifically 15 mg / L, 20 mg / L, 25 mg / L, 30 mg / L, 35 mg / L, 40 mg / L, or 45 mg / L.

[0022] In this invention, the reaction temperature is 25~40℃, specifically 26℃, 28℃, 30℃, 32℃, 34℃, 35℃, 36℃, or 38℃; the reaction time is 8~10h, specifically 8.2h, 8.5h, 8.8h, 9h, 9.2h, 9.5h, or 9.8h; and the pH value of the reaction system is 5~11, specifically 6, 7, 8, 9, or 10.

[0023] In this invention, the preparation method of the manganese oxide modified biochar includes the following steps: 1) Mix coconut shell biochar with potassium permanganate solution and impregnate to obtain coconut shell biochar loaded with potassium permanganate; 2) Coconut shell biochar loaded with potassium permanganate was roasted to obtain manganese oxide modified biochar.

[0024] In this invention, the mass-to-volume ratio of coconut shell biochar to potassium permanganate solution in step 1) is 0.5~1g:10mL, preferably 0.6~1g:10mL, and more preferably 0.8~1g:10mL; the molar concentration of the potassium permanganate solution is 0.1 mol / L.

[0025] In this invention, the immersion temperature in step 1) is 20~25℃, specifically 21℃, 22℃, 23℃, or 24℃; and the time is 4 hours.

[0026] In this invention, the roasting temperature in step 2) is 400°C and the roasting time is 90~120 min, specifically 95 min, 100 min, 105 min, 110 min, or 115 min.

[0027] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] Example 1

[0029] Coconut shell biochar (from Hongzhiyuan Water Purification Materials Co., Ltd., crushed and sieved to obtain 40-60 mesh material) was added to a 0.1 mol / L KMnO4 aqueous solution at a solid-liquid ratio of 1 g: 10 mL. The mixture was placed on a 25℃ constant temperature water bath shaker and continuously shaken for 4 h. After filtration through a 0.45 μm filter membrane, the material was washed multiple times with ultrapure water until the filtrate was colorless. The washed biochar material was then transferred to a constant temperature drying oven and dried at 90℃ for 12 h. The dried biochar material was then spread evenly in a ceramic boat and placed in a high-temperature tube furnace. The furnace was heated to 400℃ at a rate of 5℃ / min under a nitrogen atmosphere and pyrolyzed for 90 min. After the pyrolysis process, the temperature automatically dropped to room temperature. The biochar material was then removed, washed with ultrapure water, and dried at 90℃ for 12 h in a constant temperature drying oven. After cooling to room temperature, it was stored for later use. The obtained material is manganese oxide modified biochar, denoted as Mn-BC-400 (400 being the pyrolysis temperature of the material).

[0030] The manganese oxide-modified biochar obtained above was mixed with hydrogen peroxide and tetracycline-containing wastewater (the dosage of manganese oxide-modified biochar was 2 g / L, the concentration of hydrogen peroxide in the mixed system was 200 mM, and the concentration of tetracycline in the tetracycline-containing wastewater was 50 mg / L), and the reaction was carried out at 25℃ and pH 7.2 to achieve the treatment of tetracycline-containing wastewater.

[0031] Example 2

[0032] The calcination temperatures of the manganese oxide modified biochar were adjusted to 300℃, 400℃ (the same as in Example 1), 500℃, 600℃, 700℃, and 800℃, respectively, and were denoted as Mn-BC-T (T being the calcination temperature), which were consistent with the conditions in Example 1.

[0033] SEM images of manganese oxide-modified biochar at different non-calcination temperatures are shown below. Figure 1 As shown, Figure 1 In the diagram, a~f correspond to 300~800℃ respectively; through Figure 1It can be observed that the surface of the modified biochar material is rough, and a dense layer of nanoparticles appears on all of them. These particles are nano-manganese oxide particles loaded during the modification process. Comparing manganese-modified char materials prepared at different pyrolysis temperatures, it was found that the particle size of manganese oxide particles increases significantly with increasing pyrolysis temperature. This may be because the interaction force between particles decreases under high temperature conditions, making them more likely to aggregate and form larger particles. However, compared with modified char materials at other pyrolysis temperatures, the nanoparticles on the surface of Mn-BC-400 are more dense and more uniformly distributed. In addition, XRD patterns confirmed the presence of MnO. X Successfully loaded onto BC material, and determined that the prepared nanoparticles could be Mn3O4, Mn2O3, MnO, or MnO in different valence states. X mixture.

[0034] The treatment results of manganese oxide-modified biochar at different calcination temperatures on tetracycline-containing wastewater are as follows: Figure 2 As shown (where BC is the coconut shell biochar control group, and BC-400 is the control group without manganese oxide loading), among which, Figure 2 In this context, 'a' represents the change in concentration over time (C). t / C0 is the percentage concentration compared to the initial state), b is the characteristic absorption peak of TC at 8 h; through Figure 2It can be seen that pyrolysis temperature is a crucial factor affecting the adsorption and catalytic performance of modified biochar materials. Under the action of BC and BC-400, the removal rate of TC (tetracycline) in the solution gradually decreased to 77.89% and 76.23% with increasing reaction time. This may be due to the excellent pore structure and abundant surface functional groups of the carbon material, which have a good adsorption effect on TC. It may also be due to the presence of persistent free radicals centered on oxygen on the surface of the biochar, which promote the generation of active substances such as ·OH from H2O2 in the system, thereby degrading TC. Under the action of Mn-BC-T, the concentration of TC in the solution decreased rapidly within 2 hours of reaction, and then gradually leveled off. This is because the manganese oxides loaded on the surface of the carbon material react with H2O2 in the system in a Fenton-like reaction to generate ·OH with strong oxidizing ability, degrading TC and causing its concentration to decrease rapidly in a short time. However, as the main active substance in the Fenton-like reaction, ·OH has a short active lifetime and easily forms peroxy free radicals with weak oxidizing ability. Therefore, in the later stage of the reaction, the concentration of TC decreases slowly with increasing time and tends to reach equilibrium. Based on the experimental results, the final reaction time was determined to be 8 h. Comparing the changes in TC concentration under the action of biochar prepared at different pyrolysis temperatures, it can be seen that the TC concentration in the solution gradually decreases with increasing pyrolysis temperature of the carbon material, meaning that the removal rate gradually increases with increasing pyrolysis temperature. When the pyrolysis temperature is 400℃, the removal rate reaches 90.2%. When the pyrolysis temperature increases to 800℃, the removal rate also increases to 93.86%, although there is an increase, it is not significant. This indicates that the modified carbon material prepared at 400℃ has better removal performance. UV-Vis spectral analysis reflects the structural changes of TC during the removal process. The TC solution has a characteristic absorption peak at 358.5 nm, but after removal by the modified carbon material, the characteristic peak gradually broadens and its height decreases with increasing pyrolysis temperature. When the pyrolysis temperature is 300℃, a clear absorption peak can still be observed in the UV-Vis spectrum of the removed solution. However, when the pyrolysis temperature is increased to 400℃, the absorption peak becomes less obvious. As the pyrolysis temperature continues to rise to 800℃, the absorption peak almost disappears. This indicates that under the action of the modified carbon material / H2O2 system, the degree of destruction of the TC structure increases with the increase of pyrolysis temperature, leading to a gradual decrease in absorbance. This is because the high-temperature pyrolysis process alters the structure of the biochar, thereby giving the material superior catalytic and adsorption properties. This, in turn, facilitates the catalysis of H2O2 to generate more active substances that destroy the TC structure, achieving the purpose of degradation and removal.

[0035] Example 3

[0036] Based on Example 1, the dosage of manganese oxide modified biochar was changed to 0 g / L, 0.1 g / L, 0.5 g / L, 1.0 g / L, 1.5 g / L, and 2.0 g / L (under the same conditions as in Example 1), and the conditions were kept consistent with those in Example 1.

[0037] Test results are as follows Figure 3 As shown, where, Figure 3 In the diagram, 'a' represents the concentration change over time, and 'b' represents the characteristic absorption peak of TC at 8 h. Figure 3 It can be seen that when only H2O2 exists in the removal system, the concentration of TC decreases slightly, with a removal rate of only 23.41%. Furthermore, the characteristic absorption peak height of TC after the reaction is lower than that of the initial TC solution, corresponding to a lower absorbance, indicating that the TC structure is destroyed under these reaction conditions. This is because H2O2 has oxidizing properties and can induce TC degradation independently, thus reducing the TC concentration in the solution. Comparing the changes in TC concentration in the solution after the reaction under different char dosages, it was found that with the continuous increase of Mn-BC-400 dosage, the removal rate showed an increasing trend, and the characteristic absorption peak of TC in the solution after the reaction gradually decreased, with a corresponding decrease in absorbance. This is because the increased amount of manganese oxide-loaded biochar provides a large number of active sites for the system, promoting the positive conversion of H2O2 into strong oxidizing free radicals. Simultaneously, the increased dosage of modified materials also improves the overall adsorption performance, thereby increasing the TC removal rate. When the char dosage increased from 0.1 g / L to 1.0 g / L, the removal rate increased from 42.34% to 89.28%. When the dosage increased to 1.5 g / L, the removal rate also increased to 90.37%, though the increase was not significant. However, as the char dosage continued to increase to 2.0 g / L, the TC removal rate decreased to 90.12%. Ignoring errors, this is because excessive char material leads to competition for adsorption sites, preventing TC from fully occupying them. Furthermore, excessive manganese can react with oxidizing substances, resulting in ineffective oxidation and reducing the ability to degrade TC. Therefore, considering the changes in removal rate, 1.0 g / L was determined to be the optimal char dosage.

[0038] Example 4

[0039] The dosage of manganese oxide modified biochar in Example 1 was adjusted to 1.0 g / L, and the concentration of hydrogen peroxide was adjusted to 50 mM, 100 mM, 150 mM, 200 mM, 250 mM, and 300 mM, while maintaining the same conditions as in Example 1.

[0040] Test results are as follows Figure 4 As shown, where, Figure 4 In the diagram, 'a' represents the concentration change over time, and 'b' represents the characteristic absorption peak of TC at 8 h. Figure 4It can be seen that when only BC, BC-400, and Mn-BC-400 are present in the reaction system, the TC concentration in the solution decreases slightly after 8 hours of reaction, indicating that the three carbon materials can adsorb TC in the aqueous solution, but the adsorption effect is worse than that of the Fenton-like system. When the catalyst is Mn-BC-400, comparing the TC concentration changes over time under different H2O2 dosages and the characteristic absorption peak of TC in the solution after 8 hours, it can be seen that as the H2O2 concentration in the system increases, the TC concentration in the solution decreases after the reaction, the removal rate gradually increases, and the characteristic absorption peak of TC gradually decreases, with the corresponding absorbance also gradually decreasing, indicating that the TC structure is destroyed. This is because the increase of H2O2 provides the system with more strong oxidizing free radicals and reactive oxygen species, promoting the degradation of TC by H2O2. When the H2O2 concentration increased to 200 mM, the TC removal rate rose to 89.32%. Furthermore, with continued increases in H2O2 dosage, the removal rate did not significantly increase, and the characteristic absorption peaks of TC almost overlapped. This is because excessive H2O2 not only consumes the ·OH generated during the reaction but also competes with TC for adsorption sites on the carbon material surface, thus reducing the TC removal rate. Therefore, 200 mM was determined to be the optimal H2O2 dosage. Under these conditions, the TC mineralization rate was 49.01%, lower than the removal rate, indicating that some substances were not completely degraded into carbon dioxide and water during the reaction, but instead generated intermediate products.

[0041] Example 5

[0042] The dosage of manganese oxide modified biochar in Example 1 was adjusted to 1.0 g / L, and then the pH of the system was adjusted to 3, 5, 7, 9, and 11, which were consistent with the conditions in Example 1.

[0043] Test results are as follows Figure 5 As shown, where, Figure 5 In the diagram, 'a' represents the concentration change over time, and 'b' represents the characteristic absorption peak of TC at 8 h. Figure 5 It can be seen that as the pH increases from 3 to 7, the absorption peak of TC in the post-reaction solution gradually decreases, and the corresponding absorbance gradually decreases. Calculations show that the TC removal rate gradually increases. The lowest removal rate at pH 3 may be due to the instability of the material under acidic conditions, which reduces its removal capacity, or it may be due to excessive H₂. + The reaction with ·OH radicals inhibits the degradation of TC by reducing reactive free radicals. This may also be due to the complete protonation of tetracycline at pH < 3.3, leading to the degradation of TC. +Tetracycline exists primarily in the form of TC, making it less susceptible to attack by reactive free radicals. When the pH rises to 9 and 11, tetracycline is rapidly degraded in the first 0.5 hours of the reaction, with removal rates reaching 78.03% and 82.48%, respectively. As the reaction continues, the absorption peak of TC in the solution at 8 hours is higher than at pH 7, corresponding to an increase in absorbance. Calculations show that the final TC removal rates decrease to 87.81% and 85.41%, respectively. This may be because tetracycline mainly exists as TC at pH 7.7 < pH < 9.7. - With TC 2- It exists in the form of TC at pH > 9.7. 2- Both forms exist in a form with a higher electron density than TC, which may promote the attack of H2O2 on active groups. However, ·OH combines with hydroxide ions to form a weaker oxidizing agent. Therefore, when the pH is in the range of 7-11, the stronger the alkalinity, the higher the degradation efficiency of the system, but the final removal rate decreases.

[0044] Example 6

[0045] The dosage of manganese oxide modified biochar in Example 1 was adjusted to 1.0 g / L, and the treatment reaction temperature in Example 1 was adjusted to 25℃, 30℃, 35℃, and 40℃, which were consistent with the conditions in Example 1.

[0046] Test results are as follows Figure 6 As shown, where, Figure 6 In the diagram, 'a' represents the concentration change over time, and 'b' represents the characteristic absorption peak of TC at 8 h. Figure 6 It can be seen that as the reaction temperature increases to 35℃, the removal rate of TC in the system accelerates, gradually increasing to 92.5%. Furthermore, the characteristic absorption peak of TC in the post-reaction solution becomes smaller, corresponding to a decrease in absorbance. This is because the increased temperature accelerates molecular thermal motion, making it easier for the active sites on the biochar surface to contact H2O2 and generate ·OH radicals. Simultaneously, the increased temperature also promotes the diffusion of TC in the solution, allowing for better contact between TC and oxidizing substances. Both factors work together to promote TC removal. However, when the reaction temperature reaches 40℃, the TC removal rate decreases to 91.4%. The characteristic absorption peak of TC in the post-reaction solution is slightly higher than that under the 35℃ reaction conditions. This is because at higher temperatures, H2O2 may thermally decompose to generate byproduct O2, which reacts with ·OH, reducing the ·OH concentration in the system and thus decreasing the degradation effect. Simultaneously, the more vigorous reaction between manganese oxide-modified biochar and H2O2 at higher temperatures may increase the concentration of Mn dissolution, limiting the degradation effect and reducing the stability of the material to some extent. However, modified biochar has an excellent ability to remove TC over a wide temperature range and exhibits good stability.

[0047] The various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0048] The above description of the disclosed embodiments enables those skilled in the art to make or use the invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Therefore, the invention is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar, characterized in that, Includes the following steps: Manganese oxide-modified biochar, hydrogen peroxide, and tetracycline-containing wastewater are mixed to obtain a mixed solution, which is then reacted to achieve the treatment of tetracycline-containing wastewater. The mass concentration of the manganese oxide-modified biochar in the mixed solution is 1~2 g / L.

2. The method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar according to claim 1, characterized in that, In the mixed solution, the molar concentration of hydrogen peroxide is ≥200 mmol / L.

3. The method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar according to claim 2, characterized in that, The concentration of tetracycline in the tetracycline-containing wastewater is 10~50 mg / L.

4. A method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar according to any one of claims 1 to 3, characterized in that, The reaction is carried out at a temperature of 25-40°C for 8-10 hours, and the pH of the reaction system is 5-11.

5. The method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar according to claim 4, characterized in that, The preparation method of the manganese oxide modified biochar includes the following steps: 1) Mix coconut shell biochar with potassium permanganate solution and impregnate to obtain coconut shell biochar loaded with potassium permanganate; 2) Coconut shell biochar loaded with potassium permanganate was roasted to obtain manganese oxide modified biochar.

6. The method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar according to claim 5, characterized in that, The mass-to-volume ratio of coconut shell biochar to potassium permanganate solution in step 1) is 0.5~1g:10mL; The molar concentration of the potassium permanganate solution is 0.1 mol / L.

7. A method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar according to claim 5 or 6, characterized in that, The immersion temperature in step 1) is 20~25℃ and the time is 4h.

8. The method for treating tetracycline-containing wastewater based on manganese oxide-modified biochar according to claim 7, characterized in that, The roasting temperature in step 2) is 400℃, and the roasting time is 90~120min.

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