A biochar-supported manganese oxide adsorbent, its preparation method and application

Abstract

This invention belongs to the field of tetracycline adsorption material preparation technology, specifically relating to an in-situ manganese oxide adsorbent supported on biochar, its preparation method, and its application. The method includes the following steps: mixing spore-based biochar and a divalent manganese salt solution to form mixture A; mixing potassium permanganate solution and an alkaline solution to form mixture B; adding mixture A to mixture B under stirring, allowing it to stand at room temperature, then aging it at 60-80℃, and finally drying to obtain the in-situ manganese oxide adsorbent supported on biochar. This invention uses spore-based biochar as a carrier and employs a chemical co-precipitation method to synthesize the in-situ manganese oxide adsorbent supported on biochar. Manganese dioxide nanoparticles are adsorbed through the micropores of the spore-based biochar, and these nanoparticles coat the surface of the biochar, forming contact sites on the biochar surface that bind to the pollutant TC, thereby improving the removal efficiency of TC.

Description

Technical Field

[0001] This invention belongs to the field of tetracycline adsorption material preparation technology, specifically relating to a biochar in-situ supported manganese oxide adsorbent, its preparation method, and its application. Background Technology

[0002] Tetracycline antibiotics are widely used in healthcare and animal husbandry due to their low cost and significant antibacterial effects. However, due to incomplete metabolism, they are excreted into the body and pollute soil and surface water through leaching and runoff. Although the concentration of these antibiotics in domestic sewage is relatively low (100 ng / L), they are still excreted in some cases. -1 -6μg·L -1 However, in hospitals and the pharmaceutical industry, the levels can reach 100-500 mg / L. -1 The concentration of pollutants entering the soil via livestock and poultry manure reached a maximum of 10967.1 μg·kg⁻¹. -1 This far exceeds the trigger value (100 μg·kg⁻¹) for the ecotoxicity of soil antibiotics proposed by the International Coordinating Committee on Veterinary Drugs. -1 Tetracycline antibiotics possess high hydrophilicity and biological stability, enabling them to migrate and accumulate in the environment, causing pollution. If they persist in humans, aquatic organisms, and terrestrial organisms, they pose significant risks not only to human life, animal survival, and food safety but also to ecological harm. Therefore, research on the environmental behavior of tetracycline antibiotics, a novel pollutant, has become a hot topic in environmental science.

[0003] Currently, methods for treating tetracycline both domestically and internationally mainly focus on physical, chemical, and biological methods. Physical methods include adsorption, coagulation, sedimentation, and flotation, with adsorption being the most widely used. Adsorption typically utilizes the large specific surface area and surface functional groups of adsorbents to adsorb tetracycline from wastewater, thereby achieving the purpose of pollutant removal. Adsorption is widely used for antibiotic removal in water due to its advantages such as ease of operation, low cost, and no toxic byproducts. Commonly used adsorbents include clay, activated carbon, carbon nanotubes, and biochar. Biochar is a highly aromatic, carbon-rich solid product formed by high-temperature pyrolysis and carbonization of biomass under low-oxygen or oxygen-free conditions. Common raw materials for biochar preparation include crop straw, wood, animal manure, and solid waste. However, the poor functionality after pyrolysis and limited ability to adsorb high concentrations of pollutants restrict its use, requiring further modification to increase active sites. Existing modification methods include porous biochar modification and alkali modification. Porous biochar modification mainly increases the specific surface area and improves the adsorption capacity for tetracycline by preparing activated carbon (or porous biochar) from biomass. The activating agents required for preparing porous biochar are similar to those for preparing activated carbon, mainly strong bases, strong acids, phosphoric acid, ZnCl2, and carbonates of K and Na. However, this modification method suffers from low yield and serious secondary pollution. Alkali modification involves modifying the biochar obtained after biomass pyrolysis with an alkaline solution at a certain temperature. After modification, the specific surface area of ​​the biochar increases, but the functional groups such as hydroxyl groups and -CO (esters and ethers) decrease.

[0004] Therefore, this invention prepares biochar from Ganoderma lucidum spore powder (GLS) by simultaneously carbonizing and activating with KOH activator in one step. At the same time, using the spore powder biochar as a carrier, a manganese oxide adsorbent loaded on the biochar is synthesized in situ by chemical co-precipitation for the adsorption of tetracycline. Summary of the Invention

[0005] To address the aforementioned problems, this invention provides an in-situ manganese oxide adsorbent supported on biochar, its preparation method, and its application. This invention uses spore-derived biochar as a carrier and synthesizes the in-situ manganese oxide adsorbent supported on biochar using a chemical co-precipitation method. Manganese dioxide (MnO2) nanoparticles are adsorbed through the micropores of the spore-derived biochar. The MnO2 nanoparticles coat the surface of the biochar, forming contact sites on the biochar surface that bind to the pollutant tetracycline (TC), thereby improving the removal efficiency of TC.

[0006] The present invention solves the above-mentioned technical problems through the following technical solutions.

[0007] The first objective of this invention is to provide a method for preparing an in-situ supported manganese oxide adsorbent on biochar, comprising the following steps:

[0008] Mixture A is formed by mixing spore powder biochar and divalent manganese salt solution; mixture B is formed by mixing potassium permanganate solution and alkaline solution; mixture A is slowly added dropwise to mixture B under stirring, and after standing at room temperature for 4 hours, it is aged at 60-80℃. Using spore powder biochar as a carrier, manganese dioxide nanoparticles are loaded in situ on spore powder biochar using a chemical co-precipitation method to obtain a biochar in situ loaded manganese oxide adsorbent.

[0009] Furthermore, the molar mass ratio of Mn to spore biochar in the divalent manganese salt solution is 0.68-6.7 mmol:1g.

[0010] Furthermore, the molar ratio of Mn in the divalent manganese salt solution and the potassium permanganate solution is 3:2.

[0011] Furthermore, the molar ratio of Mn in the potassium permanganate solution to hydroxide ions in the alkaline solution is 1:2.

[0012] Furthermore, the specific method for preparing spore powder biochar is as follows:

[0013] The spore powder and alkali modifier are mixed and pretreated, then carbonized in a protective gas at 600-800℃. After carbonization, hydrochloric acid is added, and the mixture is soaked and stirred at room temperature and then dried to obtain spore powder biochar.

[0014] Furthermore, the ratio of spore powder to alkali modifier is 1g:5ml, and the alkali modifier is 2mol·L⁻¹. -1 A potassium hydroxide solution.

[0015] Further, the pretreatment involves dispersing the spore powder and alkali modifier at room temperature for 2 hours, followed by drying at 120-150℃ for 12 hours; the mixture is then carbonized at a heating rate of 5℃·min. -1 The incubation time was 2 hours; the concentration of hydrochloric acid was 12 mol·L⁻¹. -1 The soaking and stirring time is 24 hours, and the drying temperature is 100℃ for 24 hours.

[0016] Furthermore, the settling time was 4 hours, and the aging time was 12 hours. After aging, the filtered precipitate was washed with ultrapure water until the conductivity of the filtrate was less than 20 μS·cm. -1 The following method yields a biochar-supported manganese oxide adsorbent after drying at 80℃ for 12 hours.

[0017] The second objective of this invention is to provide a biochar-supported manganese oxide adsorbent prepared by the above preparation method, wherein the manganese oxide is manganese dioxide, and the mass ratio of biochar to manganese dioxide is 1:0.5-1.

[0018] A third objective of this invention is to provide the application of the above-mentioned biochar in-situ supported manganese oxide adsorbent in the adsorption and removal of tetracycline from water.

[0019] Compared with the prior art, the present invention has the following advantages:

[0020] (1) This invention uses spore powder biochar as a carrier and synthesizes in-situ manganese oxide adsorbent supported on biochar by chemical co-precipitation. The chemical formula of the reaction process is as follows:

[0021] 2KMnO4+3MnSO4·H2O+4NaOH→5MnO2↓+2Na2SO4+K2SO4+5H2O;

[0022] The micropores of spore-based biochar adsorb manganese dioxide (MnO2) nanoparticles. The MnO2 nanoparticles coat the surface of the biochar, forming contact sites on the biochar surface for binding with the pollutant TC. The main adsorption mechanisms of TC on the manganese oxide-loaded spore-based biochar composite material include surface complexation, π-π interactions, electrostatically assisted hydrogen bonding, pore filling, and redox reactions. Furthermore, the adsorbent application process is simple, convenient, environmentally friendly, and produces no secondary pollution, demonstrating broad application prospects.

[0023] (2) In this study, in-situ supported manganese oxide adsorbent (MB) on biochar was prepared by chemical coprecipitation. Compared with biochar (BC), it has more oxygen-containing functional groups, increased polarity and hydrophilicity. Based on the Langmuir model, the solid-liquid ratio was 0.1 g·L⁻¹. -1 At 298 K, the maximum adsorption capacity of MB-700 is 4785.9470 mg·g⁻¹. -1 Compared to traditional biochar, MB-700 has a 30-fold increase in adsorption capacity. Attached Figure Description

[0024] Figure 1 The images shown are scanning electron microscope (SEM) images of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention.

[0025] Figure 2 The X-ray diffraction patterns are those of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention.

[0026] Figure 3 The X-ray photoelectron spectra of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention are shown.

[0027] Figure 4 The adsorbents prepared in Example 1 and Comparative Example 1 of this invention have N2 adsorption-desorption isotherms and pore size distributions at 77.3 K.

[0028] Figure 5The graph shows the effect of the adsorbents prepared in Examples 1-5 and Comparative Examples 1-3 of this invention on the removal efficiency and adsorption amount of TC at the same concentration.

[0029] Figure 6 The graph shows the effect of the amount of adsorbent prepared in Example 1 and Comparative Example 1 on the TC removal efficiency and adsorption capacity.

[0030] Figure 7 The graph shows the effect of different pH values ​​on the TC removal efficiency and adsorption capacity of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention.

[0031] Figure 8 The graph shows the effect of different contact times at different temperatures on the TC removal efficiency of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention.

[0032] Figure 9 The graph shows the effect of the initial TC concentration on the TC removal efficiency of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention at different temperatures.

[0033] Figure 10 This is a graph showing the effect of coexisting ions on TC removal by the adsorbents prepared in Example 1 and Comparative Example 1 of the present invention.

[0034] Figure 11 The diagram shows the reusable use effect of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention.

[0035] Figure 12 The adsorption kinetics diagrams for TC prepared by the adsorbents in Example 1 and Comparative Example 1 of this invention are shown.

[0036] Figure 13 The images show the adsorption isotherms of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention.

[0037] Figure 14 The 1nK adsorbent prepared in Example 1 and Comparative Example 1 of this invention adsorbs 1nK d Relationship with 1 / T. Detailed Implementation

[0038] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the 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 skilled in the art without creative effort are within the scope of protection of the present invention.

[0039] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased from the market or prepared by existing methods.

[0040] On one hand, the present invention provides a method for preparing a biochar-supported manganese oxide adsorbent, comprising the following steps: mixing spore powder biochar and divalent manganese salt solution to form mixture A; mixing potassium permanganate solution and alkaline solution to form mixture B; under vigorous stirring, slowly adding mixture A dropwise to mixture B, allowing it to stand at room temperature for 4 hours, and then aging it at 60-80℃; using spore powder biochar as a carrier, manganese dioxide nanoparticles are in situ supported on the spore powder biochar by chemical co-precipitation method to obtain a biochar-supported manganese oxide adsorbent.

[0041] In this invention, spore powder biochar is used as a carrier, and a biochar-supported manganese oxide adsorbent is synthesized by chemical co-precipitation. The chemical formula for the reaction process is as follows:

[0042] 2KMnO4+3MnSO4·H2O+4NaOH→5MnO2↓+2Na2SO4+K2SO4+5H2O;

[0043] The biochar adsorbs manganese dioxide (MnO2) nanoparticles through the micropores of the biochar spores. The MnO2 nanoparticles coat the surface of the biochar, forming contact sites on the biochar surface that bind to the pollutant tetracycline (TC), thereby improving the removal efficiency of TC.

[0044] In some specific embodiments, the molar mass ratio of Mn to biochar from divalent manganese salt solution was 0.68-6.7 mmol:1g. The Ganoderma lucidum spores used in this invention are the reproductive cells of Ganoderma lucidum, possessing a uniform and unique oval-shaped structure, each approximately 8 μm in size. Furthermore, various bioactive substances, such as proteins, fatty acids, and nucleosides, were detected by GLS; these substances were used as carbon sources to prepare porous carbon with uniform shape and pore structure.

[0045] In some specific embodiments, the molar ratio of Mn in the divalent manganese salt solution and the potassium permanganate solution is 3:2. In this invention, a chemical co-precipitation method is used to load the manganese oxide adsorbent. The chemical formula for the reaction process is: 2KMnO4 + 3MnSO4·H2O + 4NaOH → 5MnO2↓ + 2Na2SO4 + K2SO4 + 5H2O. The molar ratio of Mn in the divalent manganese salt solution and the potassium permanganate solution is determined to be 3:2 based on the reaction equation. This ensures that the amount of manganese dioxide generated is within a predetermined range and that the synthesized sample has a consistent composition; a higher amount of divalent manganese salt would lead to a decrease in the average oxidation degree of manganese. In this invention, manganese oxides are a class of highly reactive metal oxides. Their abundant hydroxyl groups, large specific surface area, and specific pore structure give them strong adsorption and oxidation properties. The variable valence states and environmental friendliness of manganese oxides give them a significant advantage in removing pollutants from water. 2+ / Mn 3+ / Mn 4+ The redox properties between them give manganese oxides oxidizing capabilities, allowing them to directly oxidize some pollutants when added to water.

[0046] In some specific embodiments, the molar ratio of Mn in the potassium permanganate solution to hydroxide ions in the alkaline solution is 1:2, the volume ratio of potassium permanganate solution to alkaline solution is 60:67.5, and the concentration of the potassium permanganate solution is 0.08 mol·L⁻¹. -1 The alkaline solution has a concentration of 0.196 mol·L⁻¹. -1 Sodium hydroxide solution. MnO2 is synthesized in an alkaline medium. At the beginning of the reaction, MnSO4 reacts with NaOH to generate Mn(OH)2. Under vigorous stirring and oxidation by KMnO4, it mainly exists in an amorphous form in the short period of time at the beginning of the reaction, and is then oxidized to MnO2. However, this method requires a long aging time for the reaction to be complete.

[0047] In some specific embodiments, the preparation method of spore powder biochar is as follows:

[0048] Spore powder and an alkali modifier are mixed, pretreated, and then carbonized at 600-800℃ in a protective gas atmosphere. After carbonization, hydrochloric acid is added, and the mixture is soaked and stirred at room temperature, filtered, and dried to obtain spore powder biochar. In this invention, GLS has a uniform and unique rugby ball-shaped structure, which can be completely transformed into a three-dimensional honeycomb structure (3D-HPC) during the process. The core-shell structure of GLS ensures that KOH is present both on the outside and inside of the GLS during impregnation, leading to a rapid and simultaneous structural transformation. KOH is a key material in the production of 3D-HPC, serving not only as a hard template and chemical activator to produce a hierarchical porous structure, but also as a binder to hold the GLS together. The porous structure can increase the specific surface area and pore volume of the adsorbent, thereby developing catalytic performance while enhancing its adsorption or electron transport performance.

[0049] In some specific embodiments, the ratio of spore powder to alkali modifier is 1g:5ml, and the alkali modifier is 2mol·L⁻¹. -1 A potassium hydroxide solution.

[0050] In some specific embodiments, the pretreatment involves drying the spore powder and alkali modifier at 120-150°C for 12 hours, with a carbonization heating rate of 5°C / min. -1 The soaking and stirring were carried out for 2 hours; the concentration of hydrochloric acid was 12 mol·L⁻¹. -1 The soaking and stirring time is 24 hours, and the drying temperature is 100℃ for 24 hours.

[0051] In some specific embodiments, the settling time is 4 hours, the aging time is 12 hours, and after aging, the filtered precipitate is washed with water until the conductivity of the filtrate is less than 20 μS·cm. -1 Below, biochar-supported manganese oxide adsorbent was obtained by drying at 80℃ for 12 h. The aging process aims to improve the crystallinity of the product.

[0052] On the other hand, this invention provides a biochar-supported manganese oxide adsorbent prepared by the above-described preparation method, wherein the manganese oxide is manganese dioxide, and the mass ratio of biochar to manganese dioxide is 1:0.1-1. In this invention, the Mn in the manganese oxide is mainly in the form of Mn 4+ It exists in form, but is accompanied by a small amount of Mn. 3+ .

[0053] This invention also provides the application of biochar-supported manganese oxide adsorbent in the adsorption and removal of tetracycline (TC) from water. In this invention, the biochar-supported manganese oxide adsorbent is used to remove TC from water. Other interactions, including π-π interactions and hydrogen bonds, may form between the antibiotic and the carboxyl or hydroxyl groups on the surface of the novel biochar composite material. Furthermore, some TC can be adsorbed by MnO2 particles on the biochar surface. Meanwhile, pH has no significant effect on the adsorption of TC by the biochar-supported manganese oxide adsorbent. It can effectively remove TC from water under acidic, neutral, and weakly alkaline conditions, exhibiting good reusability. After four adsorption and regeneration cycles, the adsorption capacity of MB-700 decreases slightly, but still maintains a high adsorption capacity. The application process of the adsorbent is simple and convenient, and it is environmentally friendly, producing no secondary pollution, and has broad application prospects.

[0054] The following specific examples will provide further explanation.

[0055] Example 1

[0056] A method for preparing an in-situ supported manganese oxide adsorbent on biochar includes the following steps:

[0057] Preparation of biochar: Mix 10g of spore powder with 50mL of 2mol·L⁻¹ solution. -1 The KOH solution was added to the corundum ceramic boat and stirred evenly with a glass rod for 2 hours. The mixture was then placed in a constant temperature drying oven and dried at 120°C for 12 hours. The dried sample was then pushed into the middle of the tube of a tube furnace. The furnace plugs were placed on both sides of the corundum ceramic boat containing the sample. The sides were closed and nitrogen gas was introduced, and the furnace was heated at 5°C / min. -1 The temperature was increased to 700℃ and held for 2 hours for high-temperature carbonization. When the temperature in the tube furnace dropped below 100℃, the quartz boat was removed, and the carbonized sample was transferred to a clean, dry 250mL beaker. An appropriate volume of distilled water was added, and then 12 mol·L⁻¹ was added dropwise using a dropper. -1 Hydrochloric acid was added dropwise while stirring, and the pH was tested with pH paper until the solution became strongly acidic, with the pH less than 2 during stirring. A magnetic stir bar was added, and the sample was placed on a magnetic stirrer. The mixture was soaked and stirred for 24 hours to remove metallic compound impurities. After complete acid washing, the sample was vacuum filtered using a circulating water vacuum pump and washed with ultrapure water until the filtrate flowing from the bottom of the funnel was neutral when tested with pH paper. The filtered sample and filter paper were transferred together with tweezers to a petri dish, capped, and labeled. The sample was then placed in a forced-air drying oven set to 100℃ and dried for 24 hours to obtain spore powder biochar. The sample was labeled: BC-700.

[0058] Preparation of adsorbent:

[0059] 2.0282 g of MnSO4·H2O was dissolved in 100 mL of deoxygenated ultrapure water to obtain a concentration of 0.12 mol·L⁻¹. -1 Prepare a MnSO4·H2O solution for later use;

[0060] 1.2643 g of KMnO4 was weighed and dissolved in 100 mL of deoxygenated ultrapure water to obtain a concentration of 0.08 mol·L⁻¹. -1 Prepare a KMnO4 solution for later use;

[0061] Weigh 0.7840 g of NaOH and dissolve it in 100 mL of deoxygenated ultrapure water to obtain a concentration of 0.196 mol·L⁻¹. -1 Prepare a NaOH solution for later use;

[0062] 1.3915 g of BC-700 and 60 mL of MnSO4·H2O were mixed and stirred for 1 h to obtain a BC-MnSO4·H2O mixed solution. 60 mL of KMnO4 solution was slowly added to 67.5 mL of NaOH solution while vigorously stirring to obtain a NaOH-KMnO4 mixed solution. Under continuous stirring, the BC-MnSO4·H2O mixed solution was added dropwise to the NaOH-KMnO4 mixed solution. A black precipitate formed during stirring. After stirring for 2 h, the mixture was stopped, allowed to stand for 4 h, and then aged at 60 °C for 12 h. The bottom of the beaker showed a dark brown precipitate. The supernatant was removed with a pipette, and the precipitate was washed several times with ultrapure water until the conductivity of the filtrate was less than 20 μS·cm. -1 The washed sample was dried at 80℃ for 12 hours, ground and stored to obtain a biochar in-situ supported manganese oxide adsorbent with a modification ratio of 0.75:1, named 0.75:1MnO2 / BC-700.

[0063] Example 2

[0064] A method for preparing an in-situ supported manganese oxide adsorbent on biochar is basically the same as in Example 1, except that:

[0065] Preparation of adsorbent:

[0066] 1.3915 g of BC-700 and 80 mL of MnSO4·H2O were mixed and stirred for 1 h to obtain a BC-MnSO4·H2O mixed solution. 80 mL of KMnO4 solution was slowly added to 90 mL of NaOH solution while vigorously stirring to obtain a NaOH-KMnO4 mixed solution. Under continuous stirring, the BC-MnSO4·H2O mixed solution was added dropwise to the NaOH-KMnO4 mixed solution. A black precipitate formed during stirring. After stirring for 2 h, the mixture was stopped, allowed to stand for 4 h, and then aged at 60 °C for 12 h. The bottom of the beaker showed a dark brown precipitate. The supernatant was removed with a pipette, and the precipitate was washed several times with ultrapure water until the conductivity of the filtrate was less than 20 μS·cm. -1 The washed sample was dried at 80℃ for 12 hours, ground and stored to obtain a biochar in-situ supported manganese oxide adsorbent with a modification ratio of 1:1, named 1:1MnO2 / BC-700.

[0067] Example 3

[0068] A method for preparing an in-situ supported manganese oxide adsorbent on biochar is basically the same as in Example 1, except that:

[0069] Preparation of adsorbent:

[0070] 1.3915 g of BC-700 and 40 mL of MnSO4·H2O were mixed and stirred for 1 h to obtain a BC-MnSO4·H2O mixed solution. 40 mL of KMnO4 solution was slowly added to 45 mL of NaOH solution while vigorously stirring until homogeneous, resulting in a NaOH-KMnO4 mixed solution. Under continuous stirring, the BC-MnSO4·H2O mixed solution was added dropwise to the NaOH-KMnO4 mixed solution. A black precipitate formed during stirring. After stirring for 2 h, the mixture was stopped, allowed to stand for 4 h, and then aged at 60 °C for 12 h. The bottom of the beaker showed a dark brown precipitate. The supernatant was removed with a pipette, and the precipitate was washed several times with ultrapure water until the conductivity of the filtrate was less than 20 μS·cm. -1 The washed sample was dried at 80℃ for 12 hours, ground and stored to obtain a biochar in-situ supported manganese oxide adsorbent with a modification ratio of 0.5:1, named 0.5:1MnO2 / BC-700.

[0071] Example 4

[0072] A method for preparing an in-situ supported manganese oxide adsorbent on biochar is basically the same as in Example 1, except that:

[0073] Preparation of adsorbent:

[0074] 1.3915 g of BC-700 and 16 mL of MnSO4·H2O were mixed and stirred for 1 h to obtain a BC-MnSO4·H2O mixed solution. 16 mL of KMnO4 solution was slowly added to 18 mL of NaOH solution while vigorously stirring until homogeneous, resulting in a NaOH-KMnO4 mixed solution. Under continuous stirring, the BC-MnSO4·H2O mixed solution was added dropwise to the NaOH-KMnO4 mixed solution. A black precipitate formed during stirring. After stirring for 2 h, the mixture was stopped, allowed to stand for 4 h, and then aged at 60 °C for 12 h. The bottom of the beaker showed a dark brown precipitate. The supernatant was removed with a pipette, and the precipitate was washed several times with ultrapure water until the conductivity of the filtrate was less than 20 μS·cm. -1 The washed sample was dried at 80℃ for 12 hours, ground and stored to obtain a biochar in-situ supported manganese oxide adsorbent with a modification ratio of 0.2:1, named 0.2:1MnO2 / BC-700.

[0075] Example 5

[0076] A method for preparing an in-situ supported manganese oxide adsorbent on biochar is basically the same as in Example 1, except that:

[0077] Preparation of adsorbent:

[0078] 1.3915 g of BC-700 and 8 mL of MnSO4·H2O were mixed and stirred for 1 h to obtain a BC-MnSO4·H2O mixed solution. 8 mL of KMnO4 solution was slowly added to 9 mL of NaOH solution while vigorously stirring to obtain a NaOH-KMnO4 mixed solution. Under continuous stirring, the BC-MnSO4·H2O mixed solution was added dropwise to the NaOH-KMnO4 mixed solution. A black precipitate formed during stirring. After stirring for 2 h, the mixture was stopped, allowed to stand for 4 h, and then aged at 60 °C for 12 h. The bottom of the beaker showed a dark brown precipitate. The supernatant was removed with a pipette, and the precipitate was washed several times with ultrapure water until the conductivity of the filtrate was less than 20 μS·cm. -1 The washed sample was dried at 80℃ for 12 hours, ground and stored to obtain a biochar in-situ supported manganese oxide adsorbent with a modification ratio of 0.1:1, named 0.1:1MnO2 / BC-700.

[0079] Comparative Example 1

[0080] A method for preparing a biochar adsorbent includes the following steps:

[0081] Preparation of biochar: Mix 10g of spore powder with 50mL of 2mol·L⁻¹ solution. -1The KOH solution was added to the corundum ceramic boat and stirred evenly with a glass rod for 2 hours. The mixture was then placed in a constant temperature drying oven and dried at 120°C for 12 hours. The dried sample was then pushed into the middle of the tube of a tube furnace. The furnace plugs were placed on both sides of the corundum ceramic boat containing the sample. The sides were closed and nitrogen gas was introduced, and the furnace was heated at 5°C / min. -1 The temperature was increased to 700℃ and held for 2 hours for high-temperature carbonization. When the temperature in the tube furnace dropped below 100℃, the quartz boat was removed, and the carbonized sample was transferred to a clean, dry 250mL beaker. An appropriate volume of distilled water was added, and then 12 mol·L⁻¹ was added dropwise using a dropper. -1 Hydrochloric acid was added dropwise while stirring, and the pH was tested with pH paper until the solution became strongly acidic, with the pH less than 2 during stirring. A magnetic stir bar was added, and the sample was placed on a magnetic stirrer. The mixture was soaked and stirred for 24 hours to remove metallic compound impurities. After complete acid washing, the sample was vacuum filtered using a circulating water vacuum pump and washed with ultrapure water until the filtrate flowing from the bottom of the funnel was neutral when tested with pH paper. The filtered sample and filter paper were transferred together with tweezers to a petri dish, capped, and labeled. The sample was then placed in a forced-air drying oven set to 100℃ and dried for 24 hours to obtain spore powder biochar. The sample was labeled: BC-700.

[0082] Comparative Example 2

[0083] A method for preparing a biochar adsorbent includes the following steps:

[0084] Preparation of biochar: Mix 10g of spore powder with 50mL of 2mol·L⁻¹ solution. -1 The KOH solution was added to the corundum ceramic boat and stirred evenly with a glass rod for 2 hours. The mixture was then placed in a constant temperature drying oven and dried at 120°C for 12 hours. The dried sample was then pushed into the middle of the tube of a tube furnace. The furnace plugs were placed on both sides of the corundum ceramic boat containing the sample. The sides were closed and nitrogen gas was introduced, and the furnace was heated at 5°C / min. -1 The temperature was increased to 600℃ and held for 2 hours for high-temperature carbonization. When the temperature in the tube furnace dropped below 100℃, the quartz boat was removed, and the carbonized sample was transferred to a clean, dry 250mL beaker. An appropriate volume of distilled water was added, and then 12 mol·L⁻¹ was added dropwise using a dropper. -1Hydrochloric acid was added dropwise while stirring, and the pH was tested with pH paper until the solution became strongly acidic, with the pH less than 2 during stirring. A magnetic stir bar was added, and the sample was placed on a magnetic stirrer. The sample was soaked and stirred for 24 hours to remove metallic compound impurities. After complete acid washing, the sample was vacuum filtered using a circulating water vacuum pump and washed with ultrapure water until the filtrate flowing from the bottom of the funnel was neutral when tested with pH paper. The filtered sample and filter paper were transferred together with tweezers to a petri dish, covered, and labeled. The sample was then placed in a forced-air drying oven set to 100℃ and dried for 24 hours to obtain spore powder biochar. The sample was labeled: BC-600.

[0085] Comparative Example 3

[0086] A method for preparing a biochar adsorbent includes the following steps:

[0087] Preparation of biochar: Mix 10g of spore powder with 50mL of 2mol·L⁻¹ solution. -1 The KOH solution was added to the corundum ceramic boat and stirred evenly with a glass rod for 2 hours. The mixture was then placed in a constant temperature drying oven and dried at 120°C for 12 hours. The dried sample was then pushed into the middle of the tube of a tube furnace. The furnace plugs were placed on both sides of the corundum ceramic boat containing the sample. The sides were closed and nitrogen gas was introduced, and the furnace was heated at 5°C / min. -1 The temperature was increased to 800℃ and held for 2 hours for high-temperature carbonization. When the temperature in the tube furnace dropped below 100℃, the quartz boat was removed, and the carbonized sample was transferred to a clean, dry 250mL beaker. An appropriate volume of distilled water was added, and then 12 mol·L⁻¹ was added dropwise using a dropper. -1 Hydrochloric acid was added dropwise while stirring, and the pH was tested with pH paper until the solution became strongly acidic, with the pH less than 2 during stirring. A magnetic stir bar was added, and the sample was placed on a magnetic stirrer. The mixture was soaked and stirred for 24 hours to remove metallic compound impurities. After complete acid washing, the sample was vacuum filtered using a circulating water vacuum pump and washed with ultrapure water until the filtrate flowing from the bottom of the funnel was neutral when tested with pH paper. The filtered sample and filter paper were transferred together with tweezers to a petri dish, capped, and labeled. The sample was then placed in a forced-air drying oven set to 100℃ and dried for 24 hours to obtain spore powder biochar. The sample was labeled: BC-800.

[0088] The structural properties of the biochar in situ supported manganese oxide adsorbents prepared in Examples 1-5 and the spore powder biochar prepared in Comparative Examples 1-3 were tested. Since the biochar in situ supported manganese oxide adsorbents prepared in Examples 1-5 have similar structures, the biochar in situ supported manganese oxide adsorbent prepared in Example 1 is used as an example and named MB-700. A comparative study is conducted with Comparative Example 1 (BC-700) to illustrate its structural advantages.

[0089] Figure 1 These are scanning electron microscope (SEM) images of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention. Figure 1 In the figures, (a) shows the morphology of Comparative Example 1 at a size of 5 μm, (b) shows the morphology of Comparative Example 1 at a size of 500 nm, and (c) shows the morphology of Example 1 at a size of 5 μm. The morphology and structure of BC-700 and MB-700 were studied using scanning electron microscopy (SEM). Figure 1 As shown. BC-700 image ( Figure 1 b) exhibits a porous structure with a smooth surface and varying micropore sizes. The MB-700 surface ( Figure 1 (d) The particles exhibit an irregular shape, with a large number of particles uniformly deposited on the surface of the biochar. Some molecules aggregate to form clusters, indicating that the MnO2 nanoparticles have been successfully coated on the biochar surface. Such microsphere and aggregate structures formed on the biochar surface can provide more contact sites for binding with pollutants.

[0090] Figure 2 The images show the X-ray diffraction patterns of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention. The crystal structure and phase composition characteristics of MB-700 and BC-700 were studied by X-ray diffraction spectroscopy analysis. Figure 2 It can be seen that after loading manganese oxide, the intensity of the impurity peak of BC-700 is significantly reduced, and MB-700 shows characteristic peaks at 2θ = 37.6° and 65.9°, indicating that MnO2 was successfully loaded on the BC surface.

[0091] Figure 3 The X-ray photoelectron spectra of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention are shown. Figure 3 In the diagram, 'a' represents the full spectrum, 'b' represents C 1s, 'c' represents O 1s, and 'd' represents Mn 2p. The XPS full spectrum shows that the adsorbent is mainly composed of C, N, and O. Figure 3 a). The Mn2p peak exists only in MB-700. Figure 3 In spectrum b, the C 1s peaks are located around 284.8 eV, 286.5 eV, 288.8 eV, and 291.26 eV (292.24 eV), which are attributed to C / C=C, CO, C=O, and OC=O (π-π) bonds, respectively. From the O1s spectrum ( Figure 3 c) can be fitted with three peaks, which for MB-700 are located near 530.1 eV (Mn-O), 533.19 eV (CO / OH), and 531.59 eV (C=O), respectively. Figure 3 In d, Mn2p 1 / 2 and Mn2p 3 / 2The interval was 11.5 eV, and peak fitting using the multiple splitting method showed that MnO2 in MB-700 mainly took the form of Mn. 4+ It exists in form, but is accompanied by a small amount of Mn. 3+ .

[0092] The pore structure characteristics of the adsorbents in Example 1 and Comparative Example 1 were tested, and the results are shown in Table 1 and... Figure 4 As shown.

[0093] Table 1. Pore structures of the adsorbents in Example 1 and Comparative Example 1

[0094]

[0095] Table 1 lists the pore structure characteristics of BC-700 and MB-700. Compared with the original biochar, due to the introduction of MnO2, some pores were blocked, and the specific surface area, micropore specific surface area, and micropore volume of MB-700 all decreased to varying degrees. Figure 4 The figures show the N2 adsorption-desorption isotherms and pore size distribution of Example 1 and Comparative Example 1 of this invention at 77.3 K. Figure 4 In the diagram, (a) represents the adsorption-desorption isotherm, and (b) represents the pore size distribution. From... Figure 4 (a) It can be observed that both BC-700 and MB-700 exhibit type I adsorption-desorption isotherms at relatively low pressures of 0-0.1, showing strong nitrogen adsorption, indicating that these materials mainly contain micropores. At relative pressures of 0.9–1.0, the adsorption is slightly steeper, indicating the presence of large pores in BC-700 and MB-700. Meanwhile, MB-700 shows an H3-type hysteresis loop, indicating the presence of fracture pores within MB-700. Figure 4 (b) The pore size distributions of BC-700 and MB-700 calculated using density functional theory. It can be clearly seen that both BC-700 and MB-700 are predominantly micropores. The peaks of BC-700 are centered at 0.59, 0.82, 0.96, and 1.15 nm, while those of MB-700 are centered at 0.59 nm, 0.82 nm, and 1.01 nm. The mesopores of BC-700 and MB-700 show significant growth in the 2.0–3.0 nm peak range, with peaks above 3.0 nm showing substantial degradation. BC-700 and MB-700 possess abundant narrow mesopores, providing a high accessible surface area for ion diffusion.

[0096] The adsorbents prepared in Examples 1-5 and Comparative Examples 1-3 were used to adsorb and remove tetracycline from water, specifically including the following steps:

[0097] Using 0.01 mol·L -1NaCl (pH 6.0 ± 0.05) was used as the background electrolyte (except for experiments on the influence of coexisting ions), 0.01–1 mol·L⁻¹. -1 The initial pH was adjusted with NaOH and HCl, and two parallel sets were set up.

[0098] 1.1 Impact of Load Ratio

[0099] First, the adsorbents prepared in Examples 1-5 and Comparative Examples 1-3 were used to prepare an appropriate amount of sample suspension (3.75 g·L⁻¹) using a background electrolyte solution. -1 Disperse for 12 hours (pH 6.0 ± 0.05); then, prepare 625 mg·L⁻¹ electrolyte using background electrolyte. -1 The TC (pH 6.0±0.05) stock solution was prepared; subsequently, 2.8 mL of NaCl and 1.2 mL of TC were transferred to the corresponding labeled brown bottles, and finally, 1 mL of sample suspension was quickly added and the bottles were immediately placed in an air bath constant temperature shaker (25℃, 280 r·min). -1 After reacting at a constant temperature for 24 hours, samples were taken and quickly filtered through a 0.22 μm filter membrane into centrifuge tubes, stored in the dark, and the concentration of TC was determined at λ = 357 nm using an ultraviolet spectrophotometer.

[0100] 1.2 Experiments with different solid-liquid ratios

[0101] First, appropriate amounts of sample suspensions (5.0 g·L⁻¹) for Example 1 and Comparative Example 1 were prepared using background electrolyte. -1 ) and TC (625 mg·L -1 The mother liquor and the pH of both solutions were adjusted to 6.0 ± 0.05. Next, 3.55, 3.3, 3.05, 2.8, 2.3, and 1.8 mL of background electrolyte, 0.25, 0.5, 0.75, 1.0, 1.5, and 2.0 mL of sample suspension, and 1.2 mL of TC were transferred to the corresponding labeled brown bottles. Finally, the brown bottles were placed in a shaker (25℃, 280 rpm). -1 After reacting for 24 hours, the mixture was filtered through a 0.22 μm filter and stored in the dark until analysis. The total reaction volume was 10 mL, with solid-liquid ratios of 0.25, 0.5, 0.75, 1.0, 1.5, and 2.0 g·L⁻¹. -1 .

[0102] 1.3 Experiments with different initial TC concentrations

[0103] Initial concentrations were 50, 100, 150, 200, 250, 300, 350, 400, 450, and 500 mg·L. -1 TC.

[0104] 1.4 Experiments with different initial pH values

[0105] Prepare an appropriate amount of 0.01 mol·L⁻¹-1 NaCl solution was prepared, and 10 portions of 32 mL (1.5 g·L⁻¹) of solution with pH values ​​of 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11 were prepared using this solution. -1 The sample suspension (equilibrated for 12 h); prepare 100 mL of a 300 mg·L⁻¹ solution. -1 The initial pH of TC was set to 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11. First, 10 mL of TC (150 mg / L) was transferred... -1 Pour the solution into a brown bottle, then quickly add 10 mL of sample suspension. Adjust the pH to the appropriate value and immediately place the bottle in an air bath constant temperature shaker (25℃, 280 rpm). -1 )Isothermal oscillation for 24 hours.

[0106] 1.5 Experiments on different ion types and ion strength

[0107] Select different concentrations of K + Na + Ca 2+ Mg 2+ Ions were used as the background electrolyte for the removal of total toxicity (TC) in the composite material. The reagents and their concentrations were as follows: KCl, NaCl, CaCl2, MgCl2 (0, 0.01, 0.05, 0.1 mol·L⁻¹). -1 In Example 1 and Comparative Example 1, appropriate amounts of sample suspensions (3.75 g / L) were prepared using background electrolyte solution and dispersed for 12 h (pH 6.0 ± 0.05); subsequently, 187.5 mg / L of the solution was prepared using background electrolyte. -1 The TC (pH 6.0±0.05) stock solution was prepared; finally, 4 mL of TC was transferred to the corresponding labeled brown bottle, and 1 mL of sample suspension was quickly added. The bottle was immediately placed in an air bath constant temperature shaker (25℃, 280 r·min). -1 It was oscillated at a constant temperature for 24 hours.

[0108] 1.6 Cyclic Experiment

[0109] First, prepare an appropriate amount of sample suspension (3.75 g·L⁻¹) using the background electrolyte solution. -1 Disperse for 12 hours (pH 6.0 ± 0.05); then, prepare 625 mg·L⁻¹ electrolyte using background electrolyte. -1 The TC (pH 6.0±0.05) stock solution was prepared; subsequently, 2.8 mL of NaCl and 1.2 mL of TC were transferred to the corresponding labeled brown bottles, and finally, 1 mL of sample suspension was quickly added and the bottles were immediately placed in an air bath constant temperature shaker (25℃, 280 r·min). -1 After reacting at a constant temperature for 24 hours, the mixture was centrifuged at 1000 r·min. -1(6 min), the supernatant was filtered through a 0.22 μm filter and stored in the dark for later analysis. The minerals were washed several times with ultrapure water and the process was repeated at least 5 times. The concentration of TC was determined at λ = 357 nm using a UV spectrophotometer.

[0110] Figure 5 This diagram illustrates the effect of the adsorbents prepared in Examples 1-5 and Comparative Examples 1-3 of this invention on the removal efficiency and adsorption capacity of TC at the same concentration. Figure 5 As shown, biochar was prepared by controlling the carbonization temperature, and biochar materials with different manganese dioxide to biochar modification ratios were prepared. These materials were then used to adsorb the same concentration (150 mg·L⁻¹). -1 The TC solution was prepared, and the residual TC concentration in the solution was measured after 24 hours. The removal rate of TC by different biochars was calculated. The results are as follows: Figure 1 As shown, when the carbonization temperature is 600°C, the removal rate is only 21.8%. When the carbonization temperature increases to 700°C, the removal rate increases to 78.9%, a three-fold increase. However, when the carbonization temperature further increases to 800°C, the removal rate only increases by 5.4%. The yield of BC decreases with increasing carbonization temperature. Considering energy consumption, the BC obtained at a carbonization temperature of 700°C was selected in subsequent adsorption experiments, denoted as BC-700. When the modification ratio increases from 0.1:1 to 0.75:1, the removal efficiency increases from 66.02% to 85.11%. However, when the loading ratio further increases to 1:1, the removal rate only increases by 2.26%. Given the excellent physicochemical properties and adsorption performance of 0.75:1 MnO2 / BC-700, a manganese dioxide modified biochar material with a modification ratio of 0.75:1 was selected in the following adsorption experiments, denoted as MB-700.

[0111] In an adsorption system, determining the amount of adsorbent is a crucial factor affecting the adsorbent-adsorption equilibrium. Figure 6 This is a graph showing the effect of the amount of adsorbent prepared in Example 1 and Comparative Example 1 on the TC removal efficiency and adsorption capacity. Figure 6 As shown, the adsorption capacity of TC gradually decreases with increasing adsorbent dosage. This is mainly because excessive dosage leads to an excessive number of adsorption sites, reducing the utilization rate of the adsorbent. The removal rate of TC increases with increasing adsorbent dosage, primarily due to the increase in the number of adsorption sites. However, with increasing adsorbent dosage, the increase rate of TC removal by BC-700 is significantly greater than that by MB-700, while the decrease rate of TC adsorption capacity by BC-700 is less than that by MB-700. This may be because the pore-filling mechanism contributes more to TC removal by BC-700 than that by MB-700. Figure 6 It can be seen that when the adsorbent dosage is 0.75 g·L⁻¹ -1At that time, BC-700 and MB-700 showed very significant removal effects on antibiotic contaminants, with BC-700 achieving a removal rate of 77% and MB-700 approaching 86%. This facilitates comparative observation of experimental results.

[0112] Figure 7 This diagram illustrates the effect of different pH values ​​on the TC removal efficiency and adsorption capacity of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention. Figure 7 As shown, the removal rate of TC by MB-700 did not change significantly across different pH ranges, indicating that electrostatic interaction is not the primary mechanism for TC adsorption by MB-700. Other interactions, including π-π interactions and hydrogen bonds, may have formed between antibiotics and the carboxyl or hydroxyl groups on the surface of the novel biochar composite material. Furthermore, some TC can be adsorbed by MnO2 particles on the biochar surface. Overall, pH has no significant effect on the adsorption of TC by the novel biochar composite material; it can effectively remove TC from water under acidic, neutral, and weakly alkaline conditions, indicating that MB-700 has a wide pH adaptability range. However, the removal rate of TC by BC-700 varied significantly under different pH levels, suggesting that the pH-dependent adsorption of TC by BC-700 indicates that electrostatic interaction plays a crucial role in adsorption.

[0113] Figure 8 This is a graph showing the effect of different temperatures on the TC removal efficiency of the adsorbents prepared in Example 1 and Comparative Example 1 of the present invention. Figure 7 (a) is Comparative Example 1, and (b) is Example 1. Figure 8 The adsorption processes of BC-700 and MB-700 on TC in solution at 298 K, 308 K, and 318 K are shown as changes over time. Figure 7 It can be seen that the removal rates of BC-700 and MB-700 increase with time at all temperatures. Within the first 480 minutes of the reaction, the removal rate of TC by BC-700 and MB-700 increases rapidly. This is partly due to TC quickly occupying easily accessible adsorption sites on the surfaces of BC-700 and MB-700 through physical adsorption, and partly due to the high initial tetracycline concentration, which provides a strong adsorption driving force, leading to a faster adsorption rate. After 1440 minutes of adsorption, the adsorption of TC by BC-700 and MB-700 gradually reaches equilibrium, and the increase in removal rate slows down. This is because more active sites are occupied, reaching saturation, and the adsorption driving force weakens accordingly; at this point, it can be considered to have reached equilibrium. Therefore, the adsorption time in this invention was set at 1440 minutes. Comparing the reaction progress at the three temperatures, under the same stage conditions, increasing the temperature promotes the adsorption of TC by BC-700 and MB-700.

[0114] Figure 9This is a graph showing the effect of different temperatures and TC concentrations on the TC removal efficiency of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention. Figure 9 (a) is Comparative Example 1, and (b) is Example 1. Figure 9 The adsorption effects of BC-700 and MB-700 on tetracycline solutions of different concentrations were compared at ambient temperatures of 298K, 308K, and 318K. Figure 9 It can be seen that the removal rate of TC by BC-700 gradually decreases with increasing initial concentration. This may be because the initial concentration of TC affects its pressure gradient; the higher the initial concentration of TC, the greater its adsorption driving force, causing TC molecules in the solution to continuously move towards the adsorption site. However, for MB-700, the removal rate of TC by MB-700 changes very little with increasing initial concentration, remaining above 80%, but it cannot completely remove TC. This may be because when TC is at a low concentration, the solvent water competes with TC for adsorption.

[0115] During the TC adsorption process, ambient temperature has a certain impact on the TC removal by BC-700 and MB-700. Figure 8 and Figure 9 The adsorption effects of BC-700 and MB-700 on tetracycline solution were indirectly shown at ambient temperatures of 298 K, 308 K, and 318 K. The overall trend indicates that the adsorption capacity of BC-700 and MB-700 for tetracycline gradually increases with increasing ambient temperature, suggesting that increasing temperature accelerates the adsorption reaction and that the process is endothermic. This phenomenon can be explained by the fact that higher temperatures facilitate the transfer and diffusion of tetracycline molecules from the aqueous phase to the surfaces of BC-700 and MB-700, leading to a higher tetracycline removal rate. It is noteworthy that at lower initial tetracycline solution concentrations (50 mg·L⁻¹), the adsorption capacity of BC-700 and MB-700 gradually increases. -1 The ambient temperature did not significantly affect the adsorption of tetracycline by BC-700. However, as the concentration of antibiotics continued to increase, the adsorption capacity of BC-700 for tetracycline increased with the rise in ambient temperature, indicating that at low concentrations, temperature did not have a significant impact on the adsorption of TC by BC-700.

[0116] Figure 10 This is a graph showing the effect of coexisting ions on TC removal by the adsorbents prepared in Example 1 and Comparative Example 1 of the present invention. Figure 10 The effects of four common ions at different concentrations on the adsorption of TC by BC-700 and MB-700 were demonstrated. Overall, an inhibitory effect was observed. This is partly because the ions adsorbed onto the materials bind with water molecules, forming a hydration layer that inhibits the contact and adsorption between BC-700 and MB-700. Another reason is that they bind with TC, occupying TC's adsorption sites. (The text also mentions Ca...) 2+ In comparison, Mg 2+With a smaller radius, Mg has a stronger attraction to water molecules, resulting in a thicker hydration layer. Furthermore, under neutral conditions, Mg... 2+ It can bind to more TC and occupy more adsorption sites, so its inhibitory effect on adsorption is greater than that of Ca. 2+ The influence of coexisting ions indicates that adsorption sites are crucial for adsorption, and competition and blocking of adsorption sites severely inhibit the adsorption of BC-700 and MB-700.

[0117] Reusability is a crucial parameter for the practical application of adsorbents. Used adsorbents can be regenerated and reused through a simple water washing process. Figure 11 The diagram shows the reusable use effect of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention. Figure 11 The comparison of the reusability of BC-700 and MB-700 for removing TC is shown, such as Figure 11 As shown, both exhibited high TC removal rates during the first use. However, for the used BC-700, the adsorption capacity decreased sharply by 96 mg / g after regeneration via water washing during the second use. -1 This indicates that used BC-700 cannot be effectively regenerated by washing with water. However, for used MB-700, after four adsorption regeneration cycles, the adsorption capacity decreased slightly, but still maintained a high level (adsorption rate decreased from 84.1% to 69.3%), indicating that MB-700 is easily regenerated by washing with water. The decrease in the adsorption performance of MB-700 may be due to partial pore blockage. Compared with methods in the literature (such as methanol washing, ethanol washing, HCl + ethanol washing, high-temperature treatment, and NaOH washing), the regeneration method involved in this invention is simpler and more environmentally friendly because it uses only water as the desorbent. Therefore, MB-700 is a highly efficient adsorbent for removing antibiotics from wastewater and has great potential for practical application.

[0118] The adsorption model of tetracycline in aqueous solution by the adsorbents of Example 1 and Comparative Example 1 is studied as follows.

[0119] 1. Adsorption kinetics

[0120] Figure 12 This is an adsorption kinetic diagram of TC by the adsorbents prepared in Example 1 and Comparative Example 1 of the present invention. Figure 12 In the examples, (a) is Comparative Example 1, and (b) is Example 1. Figure 12 As shown, BC-700 and MB-700 exhibit excellent adsorption capacity for TC. The adsorption capacity of TC on biochar increases rapidly within the first 240 minutes, and then gradually stabilizes. Due to the larger surface area and pore volume of BC-700 compared to MB-700, it has a larger adsorption capacity and a faster adsorption rate.

[0121] The parameters obtained from the adsorption kinetic model are shown in Table 2. According to R... 2 Pseudo-first-order and pseudo-second-order models are unsuitable for describing the interaction between TC and activated BC-700, while the Elovich model fits well (i.e., has the highest R-value). 2 (0.98-0.99)), considering the assumptions of this model, the activated BC-700 surface is energy-multiphase, and chemisorption interactions occur on the surface. Martins et al. also obtained similar results, reporting the adsorption kinetics of TC on NaOH-activated BC in macadamia nut shells. At the three temperatures studied, the pseudo-second-order, pseudo-first-order, and Elovich models were all well-suited to describe the TC adsorption behavior on MB-700. The fitting results showed that both physical adsorption and chemisorption play important roles in TC removal. The pseudo-second-order kinetic model showed better fitting results than the pseudo-first-order kinetic model, with higher correlation coefficients, and the measured equilibrium adsorption capacity (q) was also better. e ,exp) and predicted value (q) e The values ​​(cal) are relatively close, suggesting that chemisorption is the rate-limiting step. The Elovich model describes the heterogeneous diffusion reaction of TC adsorption on MB-700.

[0122] Table 2 Adsorption kinetic model parameters of the adsorbents prepared in Example 1 and Comparative Example 1

[0123]

[0124]

[0125] 2. Adsorption isotherm

[0126] Figure 13 The above are adsorption isotherm diagrams of the adsorbents prepared in Example 1 and Comparative Example 1 of this invention. Figure 13 (a) is Comparative Example 1, and (b) is 10-500 mg·L⁻¹ of Example 1. -1 The adsorption isotherms were obtained. Due to the limited surface adsorption sites on both biochar materials, the adsorption capacity increases with increasing initial TC concentration until adsorption equilibrium is reached. According to R... 2 Both the Langmuir and Sips models can fit the adsorption process of TC on BC-700 and MB-700 well. This indicates that the adsorption of TC on BC-700 and MB-700 is a non-uniform monolayer adsorption. Based on the Langmuir model, as shown in Table 3, at a solid-liquid ratio of 0.1 g·L⁻¹, -1 At 298 K, the maximum adsorption capacities of BC-700 and MB-700 were 157.4577 mg·g⁻¹, respectively. -1 4785.9470 mg·g -1Compared to raw biochar, MB-700 exhibits a 30-fold increase in adsorption capacity. This is because manganese oxides can interact with functional groups such as carboxyl and amino groups on organic matter to form complexes, significantly enhancing the adsorption capacity and affinity of biochar materials for TC. The 1 / n value of the heterogeneity factor, defined in the Freundlich model, shows high heterogeneity and is consistently less than 1, indicating a favorable adsorption process. This result is consistent with kinetic studies (i.e., a good fit with the Elovich model). The DR model shows high R... 2 (0.98), pore filling effect (E<8kJ·mol) -1 ) plays an important role in the adsorption of TC. In addition, the Temkin model of BC-700 fits well, indicating that there is a strong intermolecular interaction between BC-700 and TC during the adsorption process. The energy change of TC adsorption on BC-700 is affected by temperature and electrostatic interaction. Due to electrostatic interaction and non-uniform pores, the adsorption of TC on the BC-700 surface is exothermic (bT>1).

[0127] The manganese dioxide-modified biochar of this invention demonstrates a significant potential as a superior adsorbent for TC removal compared to other adsorbents reported in the literature. Therefore, MB-700 shows promising application prospects for TC removal in water.

[0128] Table 3. Isotherm model parameters of the adsorbents prepared in Example 1 and Comparative Example 1

[0129]

[0130]

[0131] 3. Adsorption thermodynamics

[0132] Figure 14 The 1nK adsorbent prepared in Example 1 and Comparative Example 1 of this invention adsorbs 1nK d The relationship between temperature and 1 / T is shown in the graph. To further evaluate the effect of temperature on the adsorption TC of BC-700 and MB-700, the standard free energy change (ΔG) during the adsorption process was calculated using the Gibbs free energy equation. 0 ), standard enthalpy change (ΔH) 0 and standard entropy change (ΔS) 0 The effect of temperature on the adsorption process was explained from the perspective of energy change, and the calculation results are shown in Table 4. At three different temperatures, ΔG... 0 All values ​​are negative, indicating that it is a spontaneous adsorption process, which is thermodynamically favorable. And ΔG 0 (298K)>ΔG 0 (308K)>ΔG 0(318K), indicating that spontaneous processes increase with increasing temperature. However, ΔG 0 Both values ​​are between -20 and 0, indicating that the main mechanism of TC adsorption by BC-700 and MB-700 is physical adsorption. ΔH 0 A positive value indicates that adsorption is a typical endothermic process, and that an increase in temperature favors adsorption, which is consistent with the experimental results. Typically, ΔH... 0 Corresponding to the adsorption forces (as shown in Table 5), their magnitudes can be used to determine the forces present during adsorption. A comparison reveals that the adsorption of TC by MB-700 is driven by both hydrogen bonding and dipole interactions, while the adsorption of TC by BC-700 is driven by coordination interactions. However, the ΔH values ​​for both differ. 0 All less than 60 kJ·mol -1 This indicates that the adsorption of TC by both is mainly physical adsorption. And ΔS 0 This is because both the adsorbent and the adsorbate are encapsulated in the hydration layer in the solution, and the water molecules are arranged in an orderly manner. When adsorption occurs, the adsorbent and the adsorbate come into contact, and the water molecules between the two hydration layers are forced to be disrupted, thereby increasing the entropy and the free energy between the solid and liquid, which makes the adsorption process tend to be stable.

[0133] Table 4. Thermodynamic parameters of adsorption of the adsorbents prepared in Example 1 and Comparative Example 1.

[0134]

[0135] Table 5. Correspondence between thermodynamic parameters and adsorption forces of the adsorbents prepared in Example 1 and Comparative Example 1.

[0136]

[0137] In summary, this invention uses spore powder biochar as a carrier and employs a chemical co-precipitation method to synthesize an in-situ supported manganese oxide adsorbent on biochar. The chemical formula for the reaction process is as follows:

[0138] 2KMnO4+3MnSO4·H2O+4NaOH→5MnO2↓+2Na2SO4+K2SO4+5H2O;

[0139] The biochar adsorbs manganese dioxide (MnO2) nanoparticles through the micropores of the biochar spores. The MnO2 nanoparticles coat the surface of the biochar, forming contact sites on the biochar surface that bind to the pollutant tetracycline (TC), thereby improving the removal efficiency of TC.

[0140] In summary, the spore powder biochar and the manganese oxide-supported spore powder biochar composite material prepared in this invention are environmentally friendly adsorbents for tetracycline antibiotics in water. The results show that both biochar materials exhibit highly efficient tetracycline adsorption characteristics, with an initial TC concentration of 150 mg·L⁻¹ at a reaction temperature of 25°C. -1 Under a wide initial pH range of 2-11, the removal rate of tetracycline by spore-based biochar remained stable at over 50%, while the removal rate of tetracycline by manganese oxide-loaded spore-based biochar composite material was consistently increased by over 30%. The adsorption data conformed to the pseudo-second-order kinetic model, Langmuir isotherm models, and Sips isotherm models. The main adsorption mechanisms of tetracycline on spore-based biochar were hydrogen bonding, pore-filling interactions, electrostatic interactions, and π-π interactions between adsorbents. In contrast, the main adsorption mechanisms of tetracycline on manganese oxide-loaded spore-based biochar composite material were surface complexation, π-π interactions, electrostatically assisted hydrogen bonding, pore-filling, and redox reactions.

[0141] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

[0142] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A method for preparing a biochar-supported manganese oxide adsorbent for adsorbing tetracycline, characterized in that, Includes the following steps: Mixture A is formed by mixing spore powder biochar and divalent manganese salt solution; mixture B is formed by mixing potassium permanganate solution and alkaline solution; mixture A is added to mixture B under stirring, and after standing at room temperature, it is aged at 60-80 ℃. Using spore powder biochar as a carrier, manganese dioxide nanoparticles are loaded in situ on spore powder biochar by chemical co-precipitation method to obtain biochar in situ loaded manganese oxide adsorbent. In the biochar in situ loaded manganese oxide adsorbent, contact sites for binding with tetracycline are formed on the surface of biochar. The spore powder biochar is Ganoderma lucidum spore powder biochar; The molar ratio of Mn to biochar from divalent manganese salt solutions is 0.68–6.7 mmol: 1 g. The specific method for preparing spore powder biochar is as follows: The spore powder and alkali modifier were mixed and pretreated, and then carbonized in a protective gas at 600-800 °C. After carbonization, hydrochloric acid was added and the mixture was soaked and stirred at room temperature. After drying, spore powder biochar was obtained. The ratio of spore powder to alkali modifier is 1 g: 5 ml, and the alkali modifier is 2 mol·L⁻¹. -1 potassium hydroxide solution; The pretreatment involved dispersing the spore powder and alkali modifier at room temperature for 2 hours, followed by drying at 120-150 °C for 12 hours; the carbonization heating rate was 5 °C·min. -1 The incubation time was 2 hours; the concentration of hydrochloric acid was 12 mol·L⁻¹. -1 The pH was less than 2 during stirring, the soaking and stirring time was 24 h, and the drying temperature was 100 ℃ for 24 h.

2. The method for preparing the in-situ supported manganese oxide adsorbent on biochar according to claim 1, characterized in that, The molar ratio of Mn in the divalent manganese salt solution and the potassium permanganate solution is 3:

2.

3. The method for preparing the in-situ supported manganese oxide adsorbent on biochar according to claim 1, characterized in that, The molar ratio of Mn in potassium permanganate solution to hydroxide ions in alkaline solution is 1:

2.

4. The method for preparing the in-situ supported manganese oxide adsorbent on biochar according to claim 1, characterized in that, The settling time was 4 hours, and the aging time was 12 hours. After aging, the filtered precipitate was washed with ultrapure water until the conductivity of the filtrate was less than 20 μS·cm. -1 The following method was used to obtain in-situ supported manganese oxide adsorbent by drying at 80 °C for 12 h.

5. A method for preparing an in-situ supported manganese oxide adsorbent on biochar according to any one of claims 1-4, characterized in that, The manganese oxide is manganese dioxide, and the mass ratio of biochar to manganese dioxide is 1:0.1-1.

6. The application of the biochar in-situ supported manganese oxide adsorbent according to claim 5 in the adsorption and removal of tetracycline from water.

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