A biochar with high catalytic activity, its preparation method and its application in removing pesticides from drinking water

Abstract

The present invention relates to the technical field of drinking water treatment, and specifically to a highly catalytically active biochar and its preparation method and application in removing pesticides from drinking water. The preparation method includes: 1) removing the roots of fresh water hyacinths, cleaning them, drying them, and pulverizing and sieving them to obtain a fine and uniform powder; 2) putting the obtained powder into a sodium hydroxide solution for stirring treatment, standing to obtain a solid and washing it until neutral, drying it and then adding it together with magnesium chloride into pure water; drying the solid obtained by solid-liquid separation, placing it in a tubular furnace for pyrolysis, and then cooling it to room temperature; then grinding and sieving it, adding it into ethanol to form a dispersion, and then adding 3-aminopropyltriethoxysilane for a functionalization reaction; filtering the dispersion after the functionalization reaction, rinsing the obtained solid and then drying it to obtain functionalized magnesium-modified water hyacinth-based biochar. Activating peroxymonosulfate with the prepared biochar can efficiently remove organic pesticides from drinking water.

Description

Technical Field

[0001] The present invention relates to the technical field of drinking water treatment, and particularly to a biochar with high catalytic activity, a preparation method thereof, and an application thereof in removing pesticides from drinking water. Background Art

[0002] With the rapid development of industrialization and agricultural production, the problem of drinking water pollution has become increasingly serious. In particular, pesticide residues pose a major threat to the safety of drinking water. Pesticides such as imidacloprid have become one of the common drinking water pollutants due to their extensive use. These compounds have strong toxicity and are not easily degraded in the environment. Long-term presence in drinking water will cause potential harm to human health. Therefore, it is particularly urgent to develop new and efficient drinking water treatment technologies.

[0003] As an environmentally friendly and low-cost adsorption material and catalytic material, biochar has been widely used in the field of water treatment. Biochar has a porous structure and a high specific surface area, which can effectively adsorb organic pollutants in water. After biochar is modified by methods such as acid-base activation or metal loading, its specific surface area will become larger, with a higher adsorption capacity and adsorption sites, and can better adsorb pesticide residues in drinking water. Although modified biochar shows good performance in adsorbing pollutants due to its high specific surface area and rich pore structure, it also has some obvious limitations. First, the removal of pollutants by traditional biochar mainly relies on physical adsorption, which means that the pollutants only transfer from the water phase to the solid phase and are not completely degraded. Second, the adsorption capacity of biochar is limited and will gradually reach a saturated state over time during use, thus losing its adsorption capacity. Therefore, it is necessary to replace or regenerate it regularly. If the regeneration treatment is improper, the adsorbed pollutants may cause secondary pollution. Therefore, it is difficult to achieve persistent and efficient pollutant removal solely relying on the adsorption of traditional biochar.

[0004] As a catalytic material, biochar can degrade residual organic pesticides in drinking water into non-toxic small molecule substances or completely mineralize them into carbon dioxide and water through advanced oxidation methods. However, the catalytic ability of biochar itself is limited, and it needs to be modified to enhance its catalytic ability to better activate oxidants. In previous studies, researchers modified biochar with transition metals (such as iron, copper, manganese, cobalt, etc.) to improve its catalytic activation ability. However, metal ion leaching problems are likely to occur during the catalytic process of transition metals, which will cause secondary pollution.

[0005] Magnesium is an environmentally friendly metal that does not cause secondary pollution to drinking water and is an ideal metal for modifying biochar. Magnesium has high chemical activity and strong alkalinity, and can be rapidly converted into magnesium oxide and magnesium hydroxide at high temperatures. These compounds can form stable nanostructures on the surface of biochar, which can not only provide abundant active sites, but also significantly enhance the mechanical strength and thermal stability of biochar. The strong alkalinity and hydrophilicity of magnesium significantly change the surface chemical properties of biochar, promoting the generation of persistent free radicals. These free radicals can activate peroxymonosulfate (PMS) molecules to generate oxidation active species with high oxidation ability (such as sulfate radicals), so the catalytic efficiency can be significantly improved.

[0006] Magnesium-modified biochar can produce a synergistic effect with PMS, promoting the activation of PMS and generating active free radicals with high redox potential. This process is achieved through the interaction of magnesium ions with the complexes formed by surface functional groups of biochar. These complexes not only change the charge distribution on the biochar surface, increase the number of active sites, but also promote the transfer of electrons from biochar to PMS, accelerating the process of PMS decomposition into sulfate radicals. Therefore, magnesium-modified biochar can more effectively remove refractory organic pollutants in drinking water and even convert them into harmless small molecules or mineralize them into carbon dioxide and water.

[0007] Specifically, magnesium ions form complexes of the type Mg 2+ +2RCOO - →Mg(RCOO)2 with carboxyl groups on the biochar surface, which helps to improve the adsorption capacity of biochar for PMS and further promotes the decomposition of PMS. In addition, magnesium ions can also form similar complex structures with hydroxyl groups and phenolic hydroxyl groups, such as Mg 2+ +2ROH→Mg(ROH)2 or Mg 2+ +2C6H4OH→Mg(C6H4O)2. Such complexes enhance the redox performance of biochar and thus improve the efficiency of activating PMS. In this way, magnesium-modified biochar not only improves the activation rate of PMS, but also enhances the degradation effect of the whole system on organic pollutants in water.

[0008] Water hyacinth is an aquatic plant with rapid growth and wide distribution, and has extremely high biomass production. In recent years, water hyacinth has received extensive attention due to its multiple advantages in environmental governance and resource utilization. Preparing biochar from water hyacinth can not only effectively control its overgrowth and prevent negative impacts on the aquatic ecosystem, but also convert this potential waste into valuable resources.

[0009] In traditional biochar preparation methods, the biomass raw materials need to be pyrolyzed once first. After pyrolysis, the biochar is subjected to acid-base treatment to remove the minerals in the biochar, improve the purity and specific surface area of the biochar, and form a porous biochar structure. During the acid treatment process, the acid solution reacts with the minerals on the biochar surface, generating soluble salts, which are thus removed. The alkali treatment can change the surface chemical properties of the biochar, increasing its hydrophilicity and reactivity. During the alkali treatment process, the alkali solution reacts with the organic functional groups on the biochar surface, forming new chemical bonds, thereby changing the surface characteristics of the biochar. In order to endow the biochar with better adsorption or catalytic ability, the biochar after acid-base treatment usually needs to be impregnated with metals. Commonly used metal ions include iron, copper, manganese, cobalt, etc. The metal ions will be fixed on the biochar surface through adsorption and chemical bonding, and then a supported catalyst is formed. The biochar after metal impregnation usually needs to be pyrolyzed again to ensure that the metal ions are completely converted into metal oxides or hydroxides and firmly combined with the biochar. This process can further improve the thermal stability and catalytic activity of the biochar. During the secondary pyrolysis process, the metal ions undergo phase changes under high-temperature conditions, forming metal oxides or hydroxides with high catalytic activity. These compounds combine with the active sites on the biochar surface, forming a large number of highly efficient catalytic sites and functional groups. However, these preparation methods require pyrolysis treatment two or more times, and the operation is complex. In addition, during the pyrolysis process, the lignin contained in the unpretreated biomass raw materials is difficult to be completely decomposed or carbonized, and the formed carbonized structure will occupy the pores of the material, thus affecting its catalytic activity; the ash and coke formed by the incompletely decomposed hemicellulose during the pyrolysis process will block the pores of the biochar, thus affecting its catalytic activity; the ash (such as silicon, aluminum, iron, calcium, etc.) formed by the unpretreated biomass during the pyrolysis process will also undergo side reactions with the metal catalyst, resulting in a reduction in its catalytic efficiency.

[0010] CN113522241A discloses an iron-magnesium modified biochar, its preparation method and use. This invention uses iron-magnesium bimetals to modify biochar and uses it to adsorb and remove phosphorus or other substances in sewage. The technical solution is to pyrolyze the original biochar completed by biomass pyrolysis again after iron-magnesium modification to prepare an iron-magnesium bimetal modified biochar and use it as an adsorbent. The preparation of the modified biochar in this technical solution includes two pyrolysis treatments. First, biomass needs to be pyrolyzed into the original biochar, and then through bimetal modification treatment and re-pyrolysis treatment, the operation is cumbersome. The biochar prepared by this technical solution has good adsorption performance and can adsorb and remove pollutants in drinking water, but the pollutants only transfer from the water phase to the adsorbent. When the adsorbent reaches adsorption saturation or breakthrough of the effluent, it needs to be regenerated to restore its adsorption capacity. During this process, a large amount of regeneration liquid containing high-concentration pollutants will be generated. The treatment and disposal of the regeneration liquid are difficult, costly, and prone to secondary pollution. In addition, in this technical solution, the first pyrolysis is to directly pyrolyze and carbonize the biomass raw material. In this step, the persistent free radicals in the biomass cannot be retained. After subsequent modification and re-pyrolysis treatment, it can only increase the chemical adsorption capacity of the biochar material, and it is difficult to endow it with the ability to catalytically activate oxidants to generate strongly oxidizing reactive oxygen species (ROS).

[0011] CN118458739A discloses a modified biochar and its preparation method. The process route of this invention is: pine nut shell → pyrolysis to prepare the original biochar → NaOH activation → re-pyrolysis → citric acid soaking treatment → modified biochar. The disadvantage of this technical solution is that the material preparation process includes two pyrolysis treatments and two activation treatments, with a complex preparation program, high operation difficulty, and high cost. And the preparation program of this technical solution is similar to that of many other related patents. First, the biomass raw material is pyrolyzed, and then NaOH is used to activate the prepared original biochar. Although this treatment can make the prepared material obtain a larger specific surface area and a more perfect pore structure, the NaOH activation treatment will also damage the pore structure of the biochar; then citric acid is used to soak it, which is acid activation, and its main function is to increase the specific surface of the biochar and the number of hydrogen bonds. However, the biochar prepared by this method basically does not have catalytic sites and can only be used as an adsorbent.

[0012] CN117509874A discloses a method for activating persulfate with coconut shell biochar as an activator to treat organic wastewater. The technical solution first pyrolyzes coconut shell powder to obtain raw biochar, then uses potassium ferrate to modify the prepared raw biochar, and finally pyrolyzes the modified biochar again and uses it as a catalyst to activate persulfate to remove rhodamine B in aqueous solution. This technical solution first pyrolyzes biomass raw materials to prepare raw biochar, and then sequentially modifies and re-pyrolyzes it to obtain modified biochar. This method increases energy consumption and production costs compared with the one-step pyrolysis method. Moreover, during the modification process of this solution, by-products such as Fe(OH)3 and KOH will be generated, and the by-products need to be treated, increasing the preparation cost of the materials. In addition, this solution mainly targets pollutants in organic wastewater such as rhodamine B, and the water quality adaptability and stability of the materials are both poor, and it is not applicable to the field of drinking water treatment. Summary of the Invention

[0013] In view of the above problems, the present invention provides a highly catalytically active biochar and its preparation method and application in removing pesticides in drinking water. Through magnesium modification treatment, the performance of water hyacinth biochar is further improved, especially showing significant advantages in catalytically activating PMS to remove organic pollutants (such as imidacloprid) in water. This method can not only achieve efficient removal of pollutants in drinking water, but also promote the resource utilization of waste and environmental protection, which is in line with the concept of sustainable development.

[0014] The present invention first pretreats biomass powder with NaOH to remove impurities in the biomass while changing the cellulose and lignin structures of the biomass and infiltrating trace amounts of alkali into the interior of the biomass, thereby introducing more hydrophilic groups such as hydroxyl groups and strengthening the effect of subsequent Mg modification, so that the number of catalytic active sites of the prepared material can be increased; then, 3-aminopropyltriethoxysilane (APTES) is used to strengthen the function of the biochar obtained after Mg modification and pyrolytic carbonization to improve the catalytic effect and material stability of the prepared material; finally, the optimal preparation parameters of APTES-functionalized magnesium-modified water hyacinth-based biochar (WHMBC600) and the optimal process parameters for activating PMS to remove imidacloprid in drinking water are determined through experiments, and the water quality adaptability and cyclic reuse performance of the prepared material are verified.

[0015] To efficiently remove the residues of organic pesticides in drinking water and ensure the safety of drinking water quality, the present invention utilizes WHMBC600 to activate PMS to generate ROS, which can achieve the efficient removal of pesticides such as imidacloprid in drinking water in a short time and does not produce toxic and harmful metal ions that cause secondary pollution of water quality. It is expected to popularize and apply the biochar prepared by the present invention to the advanced oxidation water treatment field of activating oxidants to remove organic pollutants in water, overcoming the defects of long time, low efficiency, difficult recovery, and high risk of using biochar as an adsorbent to remove pollutants in the prior art, and solving the deficiencies such as poor catalytic activity of carbon-based catalysts, cumbersome preparation operations, high production costs, poor water quality adaptability, and poor recycling performance at present.

[0016] Specifically, the present application provides the following technical solutions:

[0017] A preparation method of a biochar with high catalytic activity, comprising the following steps:

[0018] (1) Raw material preparation

[0019] Select fresh water hyacinths, remove the roots, and wash them clean with deionized water; dry the water hyacinths until all the moisture is removed; crush the dried water hyacinths and sieve them to obtain fine and uniform water hyacinth powder.

[0020] (2) Preparation of modified biochar

[0021] Put the water hyacinth powder into a NaOH solution and stir it, then let it stand to obtain sedimented solid particles, and wash them with deionized water until neutral. Dry the obtained solid to obtain WH.

[0022] Add WH and MgCl2 to pure water together, stir and then let it stand; separate the solid from the liquid and dry the obtained solid. Place the dried solid in a tubular furnace filled with nitrogen for pyrolysis. After the pyrolysis is completed, cool it to room temperature; use a mortar to grind the magnesium-modified biochar obtained after pyrolysis carbonization, and then sieve it to obtain magnesium-modified biochar solid powder.

[0023] Add the magnesium-modified biochar solid powder to ethanol to form a magnesium-modified biochar dispersion liquid, then add a certain amount of APTES and stir to functionalize the magnesium-modified biochar; filter the reacted dispersion liquid to obtain a functionally enhanced magnesium-modified biochar solid powder, then use deionized water to rinse the residual ethanol and unreacted APTES on it, and finally place the rinsed biochar solid in an oven for drying to obtain WHMBC600.

[0024] Further, in the step (1), the water hyacinths are placed in an oven at 80 °C for drying until all the moisture is removed. Among them, the sieve mesh number is 100 mesh.

[0025] Further, in step (2), water hyacinth powder is put into a 25 mM NaOH solution, stirred for 1 h, allowed to stand for 0.5 h to obtain sedimented solid particles, and washed with deionized water until neutral. The obtained solid is placed in an oven at 80 °C for drying treatment to obtain WH.

[0026] Further, in step (2), the alkali-treated WH and MgCl2 are added to pure water at a mass ratio of 1:5, stirred with a magnetic stirrer for 12 h, and then allowed to stand for 0.5 h to obtain sedimented solid particles; the solid obtained after solid-liquid separation is placed in an oven at 80 °C for drying treatment, and the dried solid is placed in a tubular furnace filled with nitrogen and pyrolyzed at 600 °C for 2 h. After pyrolysis is completed, it is cooled to room temperature of 20-25 °C; the magnesium-modified biochar obtained after pyrolysis and carbonization treatment is ground with a mortar, and then passed through a 100-mesh sieve to obtain magnesium-modified carbon solid powder.

[0027] Further, in step (2), the magnesium-modified carbon solid powder is added to ethanol to form a magnesium-modified biochar dispersion, and then APTES is added to functionalize the magnesium-modified biochar under the stirring of a magnetic stirrer for 1 h; the reaction dispersion is filtered through a 0.22-μm filter membrane to obtain functionally enhanced magnesium-modified carbon solid powder, and then the residual ethanol and APTES on it are rinsed off with deionized water. Finally, the rinsed solid is placed in an oven at 80 °C for drying treatment to obtain WHMBC600.

[0028] Among them, the mass-volume ratio of the magnesium-modified carbon solid powder to APTES is 1:0.05.

[0029] The highly catalytically active biochar prepared by the present invention is used to remove pesticides in drinking water, and the pesticides include imidacloprid, fipronil, glyphosate, DDT, etc. The specific method is as follows: PMS is added to the drinking water containing pesticides, and then highly catalytically active biochar is added, and the mixture is oscillated in a 25 °C constant temperature water bath oscillator at a speed of 180 r / min. Among them, the PMS is potassium peroxymonosulfate.

[0030] Samples are taken at set time intervals. After adding an excessive amount of sodium thiosulfate to quench the reaction, the mixture is filtered through a 0.22-μm filter membrane, and then the concentration of pesticides in the water is measured using an ultra-high performance liquid chromatography-tandem triple quadrupole mass spectrometer.

[0031] Before the pyrolysis of the biomass of the present invention, NaOH alkaline solution pretreatment is carried out first. The biomass raw material is treated with 25 mM NaOH solution under stirring conditions at room temperature for 1 h. During the alkaline solution pretreatment, NaOH can change the cellulose and lignin structures of the biomass, break the ester bonds and ether bonds in the lignin, make it partially dissolve or degrade, and reduce the lignin content in the biomass. Specifically, the alkali treatment can remove the aromatic rings and phenolic hydroxyl groups in the lignin, destroy the three-dimensional network structure of its raw materials, and separate it from the biomass matrix. This process not only removes part of the lignin, but also generates phenoxy radicals and other oxygen-containing radicals; the alkaline solution pretreatment can also change the cellulose structure, increase the accessibility and reactivity of cellulose, convert part of the crystalline region of cellulose into amorphous state, reduce the crystallinity of cellulose, and thus expose more active sites, which is helpful for subsequent chemical modification and functionalization. During this process, the hydroxyl groups in cellulose can be activated to generate alkoxy radicals; the alkali washing can also degrade hemicellulose, further improving the accessibility and reactivity of the biomass. The removal of hemicellulose can increase the porosity and specific surface area of the biomass and improve its adsorption and catalytic properties. The biomass pretreated with the alkaline solution is repeatedly rinsed with deionized water until it is neutral to remove the residual NaOH, and then the biomass pretreated with the alkaline solution is placed in a magnesium salt solution and stirred. The trace amount of NaOH remaining in the biomass will react with magnesium ions to form magnesium hydroxide nanolayers. During the treatment with the magnesium solution, not only the metal content in the biomass is increased, but also the magnesium ions can penetrate deep into the interior of the biomass. The biomass treated with the magnesium solution is directly subjected to pyrolysis treatment. During this process, the magnesium ions are converted into magnesium oxide and magnesium hydroxide, and these compounds are firmly combined with the biochar to form a stable nanostructure. Magnesium oxide and magnesium hydroxide form rich active sites during the pyrolysis process. These structures not only provide efficient catalytic active centers, but also enhance the mechanical strength and thermal stability of the biochar.

[0032] APTES is a silane coupling agent whose chemical structure contains a silyl group and an amino group. The silyl group can generate silanol groups through hydrolysis reaction, and then react with the hydroxyl groups on the surface of biochar to form stable silicon-oxygen bonds, improving the durability and stability of the material. The amino group provides hydrophilicity and reactivity. It can form hydrogen bonds with water molecules, so it can improve the hydrophilicity of biochar, and can form coordination bonds with metal ions, enhancing the fixation of metal ions, and then increasing the density and stability of catalytic active centers. After modification with APTES, functional groups such as amino groups are introduced onto the surface of magnesium-modified biochar. These groups can further participate in chemical reactions, such as forming amide bonds with carboxylic acids and reacting with oxidants such as PMS to generate free radicals with high oxidation ability, thus significantly improving the efficiency of activating oxidants to remove organic matters. The functional strengthening treatment step of APTES is to first disperse magnesium-modified biochar in an ethanol solvent, then add an appropriate amount of APTES, stir and react for 1 h, and then wash with deionized water and dry in an oven. The functionalized biochar has been significantly improved in terms of hydrophilicity, catalytic activity and stability, and is particularly suitable for removing organic pollutants such as imidacloprid in drinking water. In addition, if biochar is modified with other metals, such as iron, copper, manganese, cobalt, etc., the metal ion leaching can be effectively inhibited after treatment with APTES, improving its secondary pollution problem. After functionalization, it is necessary to wash thoroughly with deionized water to remove the unreacted APTES on the material surface.

[0033] Compared with the prior art, the highly catalytically active biochar, its preparation method and its application in removing imidacloprid in drinking water of the present invention have at least the following beneficial effects:

[0034] (1) When preparing the biochar catalyst by using the technology of the present invention, only one-step pyrolysis method is needed. The modification method and operation steps are simple, and the prepared material has high-efficiency and stable catalytic effects.

[0035] (2) The preparation method of the present invention sequentially performs NaOH pretreatment, Mg 2+ modification, pyrolytic carbonization, APTES functional strengthening and other treatment steps to prepare WHMBC600. The relevant treatments significantly enhance the hydrophilicity, catalytic activity, water quality adaptability and recycling use performance of the biochar.

[0036] (3) Compared with the method of preparing biochar by adsorbing and activating oxidants to remove organic matters in drinking water in the prior art, the highly catalytically active biochar WHMBC600 prepared by the present invention can activate PMS to efficiently remove different kinds of pesticides in drinking water. The removal rates of 10 mg / L different pesticide aqueous solutions after being treated by the WHMBC600 / PMS system for 60 min are all nearly 100%.

[0037] (4) Ability to efficiently activate PMS: By subjecting WH to alkali pretreatment, magnesium modification, pyrolysis, and functionalization in sequence, the specific surface area, pore structure, and catalytic activity of the prepared biochar were significantly improved. The test results show that the efficiency of removing imidacloprid from water by combining highly catalytically active biochar WHMBC600 with PMS is much higher than that of using unmodified biochar (WHBC600) alone, WHMBC600 alone, PMS alone, or the combination of WHBC600 / PMS to remove imidacloprid.

[0038] (5) The technical method of the present invention can achieve a high removal rate of imidacloprid within a wide range of solution pH and temperature, has strong water quality adaptability, and still has high catalytic activity after multiple cycles of regeneration, showing great potential for engineering applications.

[0039] The following further describes the highly catalytically active biochar of the present invention, its preparation method, and its application in removing imidacloprid from drinking water in conjunction with the accompanying drawings. Description of the Drawings

[0040] Figure 1 It is the SEM image of WHBC600.

[0041] Figure 2 It is the SEM image of WHMBC600.

[0042] Figure 3 It is the Raman spectra of WHBC600 and WHMBC600.

[0043] Figure 4 It is the removal rate of imidacloprid in the experimental system (Experimental Example 1) and the control systems (Experimental Examples 2 - 5).

[0044] Figure 5 It is the solution salinity at 120 min of treatment in the system of Experimental Example 1.

[0045] Figure 6 It is the effect of NaOH concentration on the efficiency of activating PMS by WHMBC600 to oxidize and remove imidacloprid in Experimental Example 6.

[0046] Figure 7 It is the effect of the mass ratio of MgCl2 to WH on the efficiency of activating PMS by WHMBC600 to oxidize and remove imidacloprid in Experimental Example 7.

[0047] Figure 8 It is the effect of pyrolysis temperature on the efficiency of activating PMS by WHMBC600 to oxidize and remove imidacloprid in Experimental Example 8.

[0048] Figure 9 It is the effect of the addition amount of APTES on the efficiency of activating PMS by WHMBC600 to oxidize and remove imidacloprid in Experimental Example 9.

[0049] Figure 10 The influence of the initial imidacloprid concentration on the removal efficiency of imidacloprid by the WHMBC600 / PMS system in Experimental Example X.

[0050] Figure 11 The influence of the addition amount of WHMBC600 on the removal efficiency of imidacloprid by the WHMBC600 / PMS system in Experimental Example XI.

[0051] Figure 12 The influence of the initial PMS concentration on the removal efficiency of imidacloprid by the WHMBC600 / PMS system in Experimental Example XII.

[0052] Figure 13 The influence of the initial pH of the solution on the removal efficiency of imidacloprid by the WHMBC600 / PMS system in Experimental Example XIII.

[0053] Figure 14 The influence of the reaction temperature on the removal efficiency of imidacloprid by the WHMBC600 / PMS system in Experimental Example XIV.

[0054] Figure 15 The influence of the WHMBC600 / PMS system on the removal efficiency of imidacloprid in drinking water under the actual drinking water matrix in Experimental Example XV.

[0055] Figure 16 The removal rates of different types of pesticides in the WHMBC600 / PMS system in Experimental Example XVI.

[0056] Figure 17 The efficiency of the WHMBC600 / PMS system for removing imidacloprid after regeneration treatment with different types of regenerants in Experimental Example XVII. Detailed implementation manners

[0057] The abbreviations involved in the experiments of the present invention are explained as follows:

[0058] WH: Water hyacinth powder pretreated with NaOH solution.

[0059] WHBC600: Water hyacinth-based biochar without NaOH pretreatment, magnesium impregnation modification, and APTES functionalization

[0060] WHMBC600: Water hyacinth-based biochar after NaOH pretreatment, magnesium impregnation modification, and APTES functionalization.

[0061] Experimental Example 1

[0062] (1) Preparation of biochar

[0063] Raw material preparation: ① Select fresh water hyacinths, remove the roots, and wash them thoroughly with deionized water; ② Place the water hyacinths in an 80°C oven for drying until all the moisture is removed; ③ Use a high-speed pulverizer to crush the dried water hyacinths, and then pass them through a 100-mesh sieve to obtain fine and uniform water hyacinth powder.

[0064] Preparation of unmodified biochar: ① Place the water hyacinth powder in a nitrogen-purged tube furnace and pyrolyze it at 600°C for 2 h. After pyrolysis, cool it to room temperature (20 - 25°C); ② Use a mortar to grind the biochar obtained after pyrolysis and carbonization, and then pass it through a 100-mesh sieve to obtain unmodified water hyacinth-based biochar powder WHBC600 (for experimental control).

[0065] Preparation of modified biochar: ① Put the water hyacinth powder into a 25 mM NaOH solution, stir it with a magnetic stirrer for 1 h, then let it stand for 0.5 h to obtain sedimented solid particles, and wash them with deionized water until neutral. Put the obtained solid into an 80°C oven for drying to obtain WH; ② Mix WH and MgCl2 in a mass ratio of 1:5 (i.e., 2 g WH and 10 g MgCl2), add the mixture to 100 mL of pure water, stir it with a magnetic stirrer for 12 h, then let it stand for 0.5 h to obtain sedimented solid particles; ③ After separating the solid and liquid, place the obtained solid in an 80°C oven for drying, then place the dried solid in a nitrogen-purged tube furnace and pyrolyze it at 600°C for 2 h. After pyrolysis, cool it to room temperature (20 - 25°C); ④ Use a mortar to grind the magnesium-modified biochar obtained after pyrolysis and carbonization, and then pass it through a 100-mesh sieve to obtain magnesium-modified carbon solid powder; ⑤ Add 1 g of magnesium-modified carbon solid powder to 50 mL of ethanol to form a magnesium-modified biochar dispersion, and then add 0.05 mL of APTES to the dispersion. Under the stirring of a magnetic stirrer, functionalize the magnesium-modified biochar for 1 h; ⑥ Filter the reacted dispersion through a 0.22 μm filter membrane. Wash the obtained functionalized magnesium-modified carbon solid powder with deionized water to remove the residual ethanol and APTES. Finally, place the washed solid in an 80°C oven for drying to obtain functionalized magnesium-modified water hyacinth-based biochar WHMBC600.

[0066] (2) Experiment on removing imidacloprid from water: ① Prepare 50 mL of imidacloprid solution with a concentration of 10 mg / L (prepared with pure water); ② Add PMS solution to the imidacloprid solution to ensure its concentration is 4 mM; ③ Add WHMBC600 with a concentration of 0.6 g / L (i.e., 0.03 g of WHMBC600) to the above solution, and measure the initial pH of the solution to be 6.5 (the pH is not adjusted except for the experiment investigating the effect of solution pH on the removal efficiency of the target substance); ④ Oscillate in a constant temperature water bath oscillator at 25 °C at a speed of 180 r / min, regularly sample at predetermined times (0, 5, 10, 20, 30, 45, 60 min) and measure the imidacloprid concentration, and calculate the removal rate of the target substance.

[0067] Among them, PMS uses potassium hydrogen persulfate.

[0068] Experimental Example Two

[0069] Different from Experimental Example One, in Experimental Example Two, WHMBC600 was not added in the experiment of removing imidacloprid from water, serving as a single PMS control group, and the remaining steps were the same as those in Experimental Example One.

[0070] Experimental Example Three

[0071] Different from Experimental Example One, in Experimental Example Three, PMS and WHMBC600 were not added in the experiment of removing imidacloprid from water, and WHBC600 was added, serving as a single unmodified biochar control group, and the remaining steps were the same as those in Experimental Example One.

[0072] Experimental Example Four

[0073] Different from Experimental Example One, in Experimental Example Four, PMS was not added in the experiment of removing imidacloprid from water, serving as a single WHMBC600 control group, and the remaining steps were the same as those in Experimental Example One.

[0074] Experimental Example Five

[0075] Different from Experimental Example One, in Experimental Example Five, WHMBC600 was not added in the experiment of removing imidacloprid from water, and WHBC600 and PMS were added as a control group for removing imidacloprid from water by activating PMS with unmodified water hyacinth-based biochar, and the remaining steps were the same as those in Experimental Example One.

[0076] Experimental Example Six

[0077] Different from Experimental Example One, during the pretreatment process of water hyacinth powder in Experimental Example Six, NaOH solutions with concentrations of 0, 0.05, 0.1, 0.15, 0.2, 0.25, and 0.3 mol / L were used respectively. Samples were taken to detect the imidacloprid concentration at 60 min of reaction to determine the effect of NaOH concentration during the alkali pretreatment process on the efficiency of removing imidacloprid from drinking water by WHMBC600 / PMS.

[0078] Experimental Example Seven

[0079] Different from Experimental Example One, in Experimental Example Seven, 0.03 g of WHMBC6–1, WHMBC6–2, WHMBC6–3, WHMBC6–4, WHMBC6–5, WHMBC6–6, WHMBC6–7, and WHMBC6–8 were respectively added to 50 mL of a solution containing imidacloprid (10 mg / L) and PMS (4 mM). Samples were taken at 60 min of reaction to detect the imidacloprid concentration, and the optimal carbon–magnesium ratio during the magnesium modification process was determined. The remaining steps were the same as those in Experimental Example One.

[0080] Among them, in WHMBC6–1, WHMBC6–2, WHMBC6–3, WHMBC6–4, WHMBC6–5, WHMBC6–6, WHMBC6–7, and WHMBC6–8 described in Experimental Example Seven, the weight ratios of WH to MgCl2 were 1:1, 1:2, 1:3, 1:4, 1:5, 1:6, 1:7, and 1:8, respectively.

[0081] Experimental Example Eight

[0082] Different from Experimental Example One, in Experimental Example Eight, the pyrolysis temperatures of WHMBC600 were set at 400, 500, 600, and 700 °C, respectively. Samples were taken at 60 min of reaction to detect the imidacloprid concentration, the effect of the pyrolysis temperature on the efficiency of WHMBC600 activating PMS to remove imidacloprid was determined, and the optimal pyrolysis temperature was determined.

[0083] Experimental Example Nine

[0084] Different from Experimental Example One, in Experimental Example Nine, 0, 0.01, 0.02, 0.03, 0.04, 0.05, and 0.06 mL of APTES were respectively used to conduct functional strengthening treatment on the magnesium–modified water hyacinth–based biochar. Samples were taken at 60 min of reaction to detect the imidacloprid concentration, and the optimal APTES addition amount was determined.

[0085] Experimental Example Ten

[0086] Different from Experimental Example One, in Experimental Example Ten, the concentrations of imidacloprid in the reaction solution were set at 5, 10, and 20 mg / L, respectively. The effect of the initial imidacloprid concentration on the oxidation efficiency of the WHMBC600 / PMS system for removing imidacloprid in water was determined. The remaining steps were the same as those in Experimental Example One.

[0087] Experimental Example Eleven

[0088] Different from Experimental Example 1, in Experimental Example 11, 0.01, 0.02, 0.03, 0.04, and 0.05 g of WHMBC600 (i.e., WHMBC600 with concentrations of 0.2, 0.4, 0.6, 0.8, and 1.0 g / L) were respectively added to the reaction system to determine the optimal carbon dosage when the WHMBC600 / PMS system oxidatively removed imidacloprid in water. The remaining steps were the same as those in Experimental Example 1.

[0089] Experimental Example 12

[0090] Different from Experimental Example 1, in Experimental Example 12, the concentrations of PMS added to the reaction system were respectively set to 0.5, 1, 2, 4, 6, and 8 mM. Samples were taken at 60 min of reaction to detect the imidacloprid concentration, and the effect of the initial PMS concentration on the oxidation efficiency of the WHMBC600 / PMS system for removing imidacloprid in water was determined. The remaining steps were the same as those in Experimental Example 1.

[0091] Experimental Example 13

[0092] Different from Experimental Example 1, in Experimental Example 13, 0.1 mM NaOH and 0.1 mM HCl were used to adjust the initial pH of the reaction solution, and the initial pH of the solution was respectively set to 3.0, 5.0, 6.5, 7.0, and 9.0 to determine the effect of the initial pH of the solution on the oxidation efficiency of the WHMBC600 / PMS system for removing imidacloprid in water. The remaining steps were the same as those in Experimental Example 1.

[0093] Experimental Example 14

[0094] Different from Experimental Example 1, in Experimental Example 14, the temperature of the constant-temperature water bath oscillator was respectively set to 25, 35, and 45 °C to determine the effect of the reaction temperature on the oxidation efficiency of the WHMBC600 / PMS system for removing imidacloprid in water. The remaining steps were the same as those in Experimental Example 1.

[0095] Experimental Example 15

[0096] Different from Experimental Example 1, in Experimental Example 15, 50 mL of the imidacloprid solution was prepared with tap water, and samples were taken at 60 min of reaction to detect the imidacloprid concentration to determine the efficiency of the WHMBC600 / PMS system for oxidatively removing imidacloprid under actual drinking water matrix conditions.

[0097] Experimental Example 16

[0098] Different from Experimental Example 1, the imidacloprid in the target solution in Experimental Example 1 was respectively replaced with glyphosate, DDT, and fipronil at the same concentration (10 mg / L). Samples were taken at 60 min of reaction to detect the imidacloprid concentration, and the removal rates of different pesticides by the WHMBC600 / PMS system were determined. The remaining experimental steps were the same as those in Experimental Example 1.

[0099] Experimental Example 17

[0100] Weigh 0.12 g of WHMBC600 used in the WHMBC600 / PMS system, and add it to 50 mL of methanol, 0.2 mol / L NaOH, and 0.2 mol / L HCl respectively. Then place it in a constant temperature (25 °C) water bath shaker and shake for 3 h. Then filter the obtained WHMBC600 and dry it in an oven at 80 °C to obtain the regenerated WHMBC600. Add 0.03 g of the regenerated WHMBC600 to the WHMBC600 / PMS reaction system, and take a sample to detect the imidacloprid concentration at 60 min of reaction. Repeat the above steps 4 times to determine the regeneration performance of WHMBC600. The remaining experimental steps are the same as those in Experimental Example 1.

[0101] The specific experimental results of the above experimental examples are as follows:

[0102] Figure 1 is the SEM image of WHBC600, Figure 2 is the SEM image of WHMBC600. From Figure 1 and Figure 2 it can be seen that after being treated by the method of the present invention, the surface of the biochar becomes rougher, has a larger specific surface area, and can provide more active sites, so the catalytic effect of the material can be improved.

[0103] From Figure 3 it can be seen that the I D / I G of magnesium-modified WHMBC600 increases from 0.79 of unmodified WHBC600 to 0.87, indicating that the modified and functionally treated WHMBC600 contains more C atom crystal defects, which can provide more activation sites for activating oxidants to degrade and remove pollutants.

[0104] From Figure 4 it can be seen that the WHMBC600 / PMS system can achieve a high removal efficiency of imidacloprid. This is because WHMBC600 as a catalyst can effectively activate PMS to generate ROS, while WHBC600 fails to improve the efficiency of PMS oxidation to remove imidacloprid.

[0105] From Figure 5 it can be seen that when the imidacloprid aqueous solution is treated by the WHMBC600 / PMS system for 120 min, it reaches a relatively high mineralization degree (TOC removal rate is 45.4%), which is significantly higher than the existing oxidation water treatment technology, indicating that the modified biochar prepared by the present invention can efficiently activate PMS to convert organic matter in water into carbon dioxide and water.

[0106] From Figure 6It can be seen that the concentration of NaOH during the pretreatment of water hyacinth powder has a significant effect on the efficiency of WHMBC600-activated PMS oxidation for the removal of imidacloprid in water. When the NaOH concentration is 25 mM, the activation performance of WHMBC600 is the highest. Too high or too low concentration will significantly reduce the activation performance of WHMBC600.

[0107] It can be seen from Figure 7 that during the WH modification treatment, the mass ratio of WH to MgCl2 can significantly affect the catalytic activation efficiency of the modified biochar. When the mass ratio of MgCl2 to WH ≤ 5, with the increase of the mass ratio, the activation performance of WHMBC600 gradually improves; when the mass ratio of MgCl2 to WH is further increased, the efficiency of WHMBC600-activated PMS for degrading imidacloprid does not change significantly. Therefore, considering the removal efficiency of the target substance and the material preparation cost, the optimal mass ratio of WH to MgC12 is 1:5.

[0108] It can be seen from Figure 8 that the pyrolysis temperature has a great influence on the efficiency of the WHMBC600 / PMS system for oxidizing and removing imidacloprid in water. Too high or too low pyrolysis temperature is not conducive to the formation of the pore structure and surface catalytic sites of the biochar, so it will significantly affect the efficiency of the modified biochar for activating PMS. Considering the catalytic activation performance and preparation cost of the biochar, the optimal pyrolysis temperature is 600 °C.

[0109] It can be seen from Figure 9 that after the biochar treated by pyrolysis is further treated by APTES functional enhancement, the hydrophilicity, catalytic activity and stability of the biochar can be improved, so it can significantly improve the efficiency of WHMBC600-activated PMS oxidation for removing imidacloprid in water. When 1 g of pyrolyzed biochar is dispersed in 50 mL of ethanol, and then 0.05 mL of APTES is added to the dispersion for functionalization treatment, the performance of activating PMS is the highest. When the addition amount of APTES ≤ 0.05 mL, the activation performance of WHMBC600 increases with the increase of the addition amount of APTES, but further increasing the addition amount of APTES causes the pore structure of WHMBC600 to be blocked, so the activation performance of WHMBC600 is reduced. Therefore, the optimal addition amount of APTES is 0.05 mL.

[0110] It can be seen from Figure 10It can be seen that during the process of increasing the concentration of imidacloprid in the WHMBC600 / PMS system from 5 mg / L to 10 mg / L, its removal rate gradually decreases. When the initial imidacloprid concentration is ≤10 mg / L and the reaction time is 60 min, the removal rate of imidacloprid is above 97%. When the initial imidacloprid concentration increases to 20 mg / L, the removal rate of imidacloprid is still as high as 77.7%. And the concentration of imidacloprid in drinking water is much lower than this concentration (generally at the μg / L level), so the target substance can be removed by 100% in a shorter time.

[0111] It can be seen from Figure 11 that the dosage of WHMBC600 has a significant impact on the oxidation efficiency of imidacloprid removal in the WHMBC600 / PMS system. When the dosage of WHMBC600 increases from 0.2 g / L to 0.6 g / L, that is, when the dosage increases from 0.01 g to 0.03 g, the removal rate of imidacloprid increases significantly. However, when the dosage of WHMBC600 further increases from 0.6 g / L to 1.0 g / L, that is, when the dosage increases from 0.03 g to 0.05 g, the increase in the removal rate of imidacloprid is relatively small. Therefore, considering the utilization efficiency of the catalyst and the process treatment cost, 0.6 g / L (i.e., the dosage of 0.03 g) is selected as the optimal dosage of WHMBC600.

[0112] It can be seen from Figure 12 that the initial PMS concentration has a significant impact on the oxidation efficiency of imidacloprid removal in the WHMBC600 / PMS system. When the initial PMS concentration increases from 0.5 mM to 4 mM, the removal rate of imidacloprid increases significantly. However, when the initial PMS concentration further increases to 8 mM, the removal rate of imidacloprid decreases significantly. This is because at low initial PMS concentrations, increasing the amount of PMS added can significantly increase the generation amount of ROS in the WHMBC600 / PMS system, so the removal rate of imidacloprid in the system can be significantly improved; when the PMS concentration is further increased, it will quench the ROS generated in the WHMBC600 / PMS system, resulting in a significant decrease in the removal rate of imidacloprid in the system. Therefore, the optimal initial PMS concentration in the WHMBC600 / PMS system is 4 mM.

[0113] It can be seen from Figure 13It can be seen that during the process of increasing the initial pH of the solution from 3.0 to 9.0, the removal rate of imidacloprid in the WHMBC600 / PMS system shows a trend of first increasing and then decreasing. When pH = 6.5, the removal rate of imidacloprid is the highest (98.7%); when pH = 7.0 and 5.0, the removal rates of imidacloprid are 93.4% and 88.7% respectively; when pH = 9.0, the removal rate of imidacloprid is 83.1%; when pH = 3, the removal rate of imidacloprid is 61.3%. Therefore, when pH = 5 - 9 (the pH value of natural water bodies is generally 6.5 - 8.5), the WHMBC600 / PMS system can achieve a high removal rate of imidacloprid.

[0114] It can be seen from Figure 14 that the removal rate of imidacloprid in the WHMBC600 / PMS system shows a trend of first increasing and then decreasing with the increase of the reaction temperature. When the reaction temperature is 25°C, the removal rate of imidacloprid after 60 min of treatment is 97.7%; when the reaction temperatures are 35°C and 45°C respectively, the removal rates of imidacloprid after 60 min of treatment both reach 100%. Therefore, when the reaction temperature is 25 - 45°C, the WHMBC600 / PMS system can efficiently remove imidacloprid in water.

[0115] It can be seen from Figure 15 that in the WHMBC600 / PMS system, the removal rate of imidacloprid in the tap water matrix is lower than that in pure water, indicating that coexisting ions and organic substances in water will consume the ROS generated in the system, but the removal rate of imidacloprid (10 mg / L) in tap water after 60 min of treatment by the WHMBC600 / PMS process is still as high as 91.7%. Therefore, the WHMBC600 / PMS system has strong water quality adaptability and engineering application potential.

[0116] It can be seen from Figure 16 that when using the WHMBC600 / PMS system to treat simulated water samples of different types of pesticides for 60 min, a high removal rate of the target substances (>90%) can be achieved. Among them, the removal rates of imidacloprid, fipronil, glyphosate and DDT are 97.7%, 91.8%, 91.2% and 90.1% respectively, indicating that the product of the present invention can efficiently remove different types of pesticides in drinking water.

[0117] It can be seen from Figure 17It can be seen that when different regenerants are used to regenerate the used biochar in the WHMBC600 / PMS system, relatively good regeneration efficiency can be achieved. Among them, NaOH has the best regeneration effect as the regenerant. When the WHMBC600 activated by PMS with four cycles of regeneration is used to treat the imidacloprid aqueous solution for 60 minutes, the removal rate of imidacloprid still reaches 90.1%. When methanol and hydrochloric acid are used as catalysts, the regeneration efficiency of four cycles can also reach 72.1% and 67.5% respectively. Therefore, WHMBC600 in the method of the present invention has stable and efficient reusability.

[0118] It can be seen from the above experimental results that:

[0119] In the present invention, by pretreating the biomass raw material with an alkali solution, the cellulose structure of the raw material can be changed, lignin can be removed, and phenolic oxygen radicals and alkoxy radicals can be generated. These radicals can provide additional electron donors or acceptors, promoting the electron transfer process in the catalytic reaction, and thus better activating PMS. After the alkali pretreatment, it is rinsed with deionized water until neutral and then subjected to magnesium modification and one-step pyrolysis, forming stable magnesium oxide and magnesium hydroxide structures on the surface and inside of the biochar, further improving its catalytic activity. Finally, through APTES functional strengthening treatment, its catalytic property and stability are improved, and APTES-functionalized magnesium-modified water hyacinth-based biochar (WHMBC600) is successfully prepared. This material has a larger specific surface area, a more abundant pore structure, better catalytic activity, stronger water quality adaptability, and better reusability.

[0120] Different from the traditional technology of using NaOH to activate biochar, the present invention uses an aqueous solution of NaOH with a certain concentration to pretreat water hyacinth powder, changing the cellulose and lignin structures of the biomass, and infiltrating a small amount of alkali into the biomass, introducing more hydrophilic groups such as hydroxyl groups, which is beneficial to strengthening the effect of subsequent Mg modification.

[0121] The present invention uses a MgCl2 solution with an appropriate concentration to impregnate and stir the alkali-treated biomass, which is beneficial to generating Mg(OH)2 microflocs on the surface of the biomass and uniformly distributing them on the surface of the biomass raw material. The generated Mg(OH)2 microflocs also promote the 2+ adsorption of Mg on the surface of the biomass, enhancing the Mg loading amount on the biomass material.

[0122] In the present invention, the Mg-impregnated and stirred modified biomass is pyrolyzed and carbonized under suitable temperature conditions. The pyrolysis object is water hyacinth powder loaded with Mg(OH)2 microflocs, adsorbed with Mg 2+ and infiltrated with a small amount of alkali. The relevant actions of its internal components make the biochar generated after the pyrolysis of the biomass have a larger specific surface area, a more developed pore structure, and more catalytic active sites.

[0123] In the present invention, APTES is used to functionalize biochar dispersed in ethanol, further improving the catalytic performance and recycling performance of WHMBC600.

[0124] The magnesium-modified water hyacinth-based biochar prepared in the present invention has better activity in activating PMS. Under the conditions of appropriate addition amounts of WHMBC600 and PMS, the WHMBC600 / PMS system has a high removal rate for different pesticides in pure water within a short treatment time and has a strong water quality adaptability.

[0125] The method for preparing WHMBC600 by the technology of the present invention has a simple procedure and low cost, is suitable for large-scale production, and has great potential for engineering applications. The highly catalytically active biochar prepared in the present invention neither produces toxic and harmful metal ions that cause secondary pollution of water quality nor shows good stability and reusability in practical applications, providing an economically feasible and environmentally friendly solution for solving the problem of pesticide pollution in drinking water and the resource utilization of water hyacinths.

[0126] The preparation method of the present invention is easy to operate, saves more energy compared with the distributed calcination method, and has higher economic efficiency and environmental friendliness.

[0127] The embodiments described above are only used to describe the preferred embodiments of the present invention and do not limit the scope of the present invention. Without departing from the design spirit of the present invention, various deformations and improvements made by those of ordinary skill in the art to the technical solutions of the present invention shall fall within the protection scope determined by the claims of the present invention.

Claims

1. A preparation method of a biochar with high catalytic activity, characterized in that, It includes the following steps: (1) Raw material preparation Select fresh water hyacinths, remove the roots, and wash them clean with deionized water; dry the water hyacinths until all the moisture is removed; crush the dried water hyacinths and sieve them to obtain fine and uniform water hyacinth powder. (2) Preparation of modified biochar Put the water hyacinth powder into a NaOH solution and stir it. Let it stand to obtain sedimented solid particles, then wash them with deionized water until neutral, and dry the obtained solid to get the water hyacinth powder after alkali treatment, denoted as WH. Add WH and MgCl2 to pure water, stir for a certain time and then let it stand; separate the solid from the liquid and dry the obtained solid. Place the dried solid in a tubular furnace filled with nitrogen for pyrolysis, and cool it to room temperature after pyrolysis is completed; use a mortar to grind the magnesium-modified biochar obtained after pyrolysis carbonization, and then sieve it to obtain magnesium-modified carbon solid powder. Add the magnesium-modified carbon solid powder to ethanol to form a magnesium-modified biochar dispersion. Add a certain amount of 3-aminopropyltriethoxysilane to the dispersion, and then functionalize the magnesium-modified biochar under stirring conditions; filter the reaction dispersion, filter out the obtained functionally enhanced magnesium-modified carbon solid powder, rinse the residual ethanol and 3-aminopropyltriethoxysilane with deionized water, and then dry the rinsed solid to obtain functionalized magnesium-modified water hyacinth-based biochar.

2. The preparation method of the highly catalytically active biochar according to claim 1, wherein: In step (1), place the water hyacinths in an oven at 80 °C for drying until all the moisture is removed.

3. The preparation method of the highly catalytically active biochar according to claim 2, characterized in that: In step (1), the sieve mesh number is 100 mesh.

4. The preparation method of the highly catalytically active biochar according to claim 3, wherein: In step (2), put the water hyacinth powder into a 25 mM NaOH solution, stir it with a magnetic stirrer for 1 h, then let it stand for 0.5 h to obtain sedimented solid particles, and wash them with deionized water until neutral. Place the obtained solid in an oven at 80 °C for drying.

5. The preparation method of the highly catalytically active biochar according to claim 4, wherein: In step (2), add the WH after alkali treatment and MgCl2 to pure water at a mass ratio of 1:5, stir with a magnetic stirrer for 12 h, then let it stand for 0.5 h to obtain sedimented solid particles; separate the solid from the liquid and dry the obtained solid in an oven at 80 °C. Place the dried solid in a tubular furnace filled with nitrogen and pyrolyze it at 600 °C for 2 h, and cool it to room temperature of 20 - 25 °C after pyrolysis is completed; use a mortar to grind the magnesium-modified biochar obtained after pyrolysis carbonization, and then sieve it through a 100-mesh sieve to obtain magnesium-modified carbon solid powder.

6. The preparation method of the highly catalytically active biochar according to claim 5, wherein: In step (2), add the magnesium-modified carbon solid powder to ethanol to form a magnesium-modified biochar dispersion, and then add a certain amount of 3-aminopropyltriethoxysilane to functionalize the magnesium-modified biochar under the stirring of a magnetic stirrer for 1 h; filter the reaction dispersion through a 0.22 μm filter membrane, filter out the obtained functionally enhanced magnesium-modified carbon solid powder, and rinse the residual ethanol and 3-aminopropyltriethoxysilane with deionized water. Finally, dry the rinsed solid in an oven at 80 °C to obtain functionalized magnesium-modified water hyacinth-based biochar, denoted as WHMBC600.

7. The preparation method of the highly catalytically active biochar according to claim 6, wherein: The mass-volume ratio of the magnesium-modified carbon solid powder to 3-aminopropyltriethoxysilane is 1:0.

05.

8. The highly catalytically active biochar prepared by the preparation method according to any one of claims 1-7.

9. Use of the highly catalytically active biochar according to claim 8 in removing pesticides from drinking water, characterized in that: The pesticides include imidacloprid, fipronil, glyphosate, and DDT.

10. Use of the highly catalytically active biochar according to claim 9 in removing pesticides from drinking water, characterized in that: Add persulfate with a concentration of 4 mM to the drinking water containing pesticides, and then add 0.03 g of highly catalytically active biochar, and oscillate in a constant temperature water bath oscillator to remove the pesticides in the drinking water.

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