High-catalytic-activity biochar, preparation method and application of high-catalytic-activity biochar in removal of pesticide in drinking water

Abstract

The invention relates to the technical field of drinking water treatment, in particular to high-catalytic-activity biochar, a preparation method and application of the high-catalytic-activity biochar to removal of pesticides in drinking water. The preparation method comprises the following steps: 1) removing roots of fresh water hyacinth, cleaning, drying, crushing and sieving to obtain fine and uniform powder; (2) putting the obtained powder into a sodium hydroxide solution, stirring, standing to obtain a solid, washing to be neutral, drying, and adding into pure water together with magnesium chloride; drying the solid obtained by solid-liquid separation, pyrolyzing in a tubular furnace, and cooling to room temperature; the preparation method comprises the following steps: grinding and sieving the raw materials, adding the raw materials into ethanol to form a dispersion liquid, and adding 3-aminopropyltriethoxysilane to carry out a functionalization reaction; and filtering the dispersion liquid after the functionalization reaction, washing the obtained solid, and drying to obtain the functionalized magnesium-modified water hyacinth-based biochar. The prepared charcoal activated peroxymonosulfate can be used for efficiently removing organic pesticides in drinking water.

Description

Technical Field

[0001] The present invention relates to the technical field of drinking water treatment, and in particular to a biochar with high catalytic activity, a preparation method 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 is becoming increasingly serious, especially pesticide residues, which pose a major threat to drinking water safety. Pesticides such as imidacloprid have become one of the common drinking water pollutants due to their widespread use. These compounds are highly toxic and difficult to degrade in the environment. Their long-term presence in drinking water will cause potential harm to human health. Therefore, it is particularly urgent to develop new, efficient and economical drinking water treatment technologies.

[0003] As an environmentally friendly and low-cost adsorption 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 modification methods such as acid-base activation or metal loading, the specific surface area of ​​biochar will become larger, with higher adsorption capacity and adsorption sites, which can better adsorb pesticide residues in drinking water. Although the 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 are only transferred from the water phase to the solid phase and are not completely degraded. Secondly, the adsorption capacity of biochar is limited. It will gradually reach a saturated state over time during use, thereby losing its adsorption capacity, so it needs to be replaced or regenerated regularly. If the regeneration is not handled properly, the adsorbed pollutants may cause secondary pollution. Therefore, it is difficult to achieve long-term and efficient pollutant removal by relying solely on the adsorption effect of traditional biochar.

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

[0005] Magnesium metal is an environmentally friendly metal that does not cause secondary pollution to drinking water and is an ideal metal for biochar modification. 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 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 and promote the generation of persistent free radicals. These free radicals can activate peroxymonosulfate (PMS) molecules to generate oxidatively active species with high oxidizing ability (such as sulfate radicals), thus significantly improving the catalytic efficiency.

[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 between magnesium ions and complexes formed by functional groups on the surface of biochar. These complexes not only change the charge distribution on the surface of biochar and increase the number of active sites, but also promote the transfer of electrons from biochar to PMS, accelerating the decomposition of PMS 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 react with carboxyl groups on the surface of biochar to form Mg 2+ +2RCOO - →Mg(RCOO)2 type complex, which helps to improve the adsorption capacity of biochar for PMS and further promote the decomposition of excessive PMS. In addition, magnesium ions can also form similar complex structures with hydroxyl and phenolic hydroxyl groups, such as Mg 2+ +2ROH→Mg(ROH)2 or Mg 2+ +2C6H4OH→Mg(C6H4O)2, such complexes enhance the redox properties of biochar, thereby improving the efficiency of activating PMS. In this way, magnesium-modified biochar not only improves the activation rate of PMS, but also improves the degradation effect of the entire system on organic pollutants in water.

[0008] Water hyacinth is a fast-growing, widely distributed aquatic plant with extremely high biomass yield. In recent years, water hyacinth has attracted widespread attention due to its multiple advantages in environmental governance and resource utilization. Using water hyacinth as a raw material to prepare biochar can not only effectively control its overgrowth and prevent negative impacts on aquatic ecosystems, but also transform this potential waste into a valuable resource.

[0009] In the traditional biochar preparation method, the biomass raw material needs to be pyrolyzed once, and the pyrolyzed biochar is treated with acid and alkali 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 reacts with the minerals on the surface of the biochar to generate soluble salts, which are then removed. Alkali treatment can change the surface chemical properties of biochar, increase its hydrophilicity and reactivity. During the alkaline treatment process, the alkali reacts with the organic functional groups on the surface of the biochar to form new chemical bonds, thereby changing the surface properties of the biochar. In order to make the biochar have better adsorption or catalytic capacity, it is usually necessary to impregnate the biochar after acid and alkali treatment with metals. Commonly used metal ions include iron, copper, manganese, cobalt, etc. The metal ions are fixed on the surface of the biochar by adsorption and chemical bonding, thereby forming a loaded catalyst. 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 bonded to the biochar. This process can further improve the thermal stability and catalytic activity of the biochar. During the secondary pyrolysis process, metal ions undergo phase changes under high temperature conditions and can form metal oxides or hydroxides with high catalytic activity. These compounds combine with the active sites on the surface of biochar to form a large number of efficient catalytic sites and functional groups. However, these preparation methods require two or more pyrolysis treatments, which are complicated to operate. In addition, during the pyrolysis process, the lignin contained in the untreated biomass raw materials is difficult to completely decompose or carbonize, and the carbonized structure formed will occupy the pores of the material, thereby affecting its catalytic activity; the ash and coke formed by the hemicellulose that is not completely decomposed during the pyrolysis process will block the pores of the biochar, thereby affecting its catalytic activity; the ash (such as silicon, aluminum, iron, calcium, etc.) formed during the pyrolysis of untreated biomass will also react with the metal catalyst, resulting in a decrease in its catalytic efficiency.

[0010] CN113522241A discloses a kind of iron-magnesium modified biochar and its preparation method and use. The invention uses iron-magnesium bimetal to modify biochar, and uses it to adsorb and remove phosphorus or other substances in sewage. The technical scheme is to modify the original biochar after biomass pyrolysis with iron-magnesium and then pyrolyze it again to prepare iron-magnesium bimetal modified biochar, and use it as an adsorbent. The preparation of modified biochar in the technical scheme includes two-step pyrolysis treatment, and the biomass needs to be first prepared into original biochar by pyrolysis treatment, and then subjected to bimetal modification treatment and pyrolysis treatment again, which is cumbersome to operate. The biochar prepared in the technical scheme has good adsorption performance and can adsorb and remove pollutants in drinking water, but the pollutants are only transferred from the water phase to the adsorbent. When the adsorbent reaches adsorption saturation or the effluent penetrates, it needs to be regenerated to restore its adsorption capacity. In this process, a large amount of regeneration liquid containing high concentrations of pollutants will be produced. The treatment and disposal of the regeneration liquid is difficult and costly, and it is easy to cause secondary pollution. In addition, in this technical solution, the first pyrolysis is to directly pyrolyze and carbonize the biomass raw materials. In this step, the persistent free radicals in the biomass cannot be retained. After subsequent modification and re-pyrolysis treatment, the chemical adsorption capacity of the biochar material can only be increased, and it is difficult to enable it to have the ability to catalyze the activation of oxidants to produce strong oxidizing reactive oxygen species (ROS).

[0011] CN118458739A discloses a modified biochar and a preparation method thereof. The process route of the invention is: pine nut shell → pyrolysis to prepare 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, the preparation procedure is complicated, the operation is difficult, and the cost is high. And this technical solution is similar to the preparation procedures of many other related patents. The biomass raw material is first pyrolyzed, and then the prepared original biochar is activated with NaOH. Although this treatment can make the prepared material obtain a larger specific surface area and a more complete pore structure, the NaOH activation treatment will also destroy 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 area of ​​the biochar and increase the number of hydrogen bonds. However, the biochar prepared by this method basically has no catalytic sites and can only be used as an adsorbent.

[0012] CN117509874A discloses a method for treating organic wastewater by activating persulfate using coconut shell biochar as an activator. The technical solution first pyrolyzes coconut shell powder to obtain original biochar, then uses potassium ferrate to modify the prepared original biochar, and finally pyrolyzes the modified biochar again, and uses it as a catalyst to activate persulfate to remove rhodamine B in the aqueous solution. The technical solution first pyrolyzes the biomass raw material to prepare the original biochar, and then sequentially modifies and pyrolyzes it to obtain the modified biochar. This method increases energy consumption and production costs compared to the one-step pyrolysis method, and during the modification process of the scheme, byproducts such as Fe(OH)3 and KOH are produced, and the byproducts need to be processed, which increases the preparation cost of the material. In addition, the scheme is mainly for pollutants such as rhodamine B in organic wastewater, and the water quality adaptability and stability of the material are poor, and it is not suitable for the field of drinking water treatment. Summary of the invention

[0013] In view of the above problems, the present invention provides a high catalytic activity biochar and a preparation method and its application in removing pesticides in drinking water. Through magnesium modification treatment, the performance of water hyacinth biochar is further improved, especially in catalytic activation of 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 firstly pretreats biomass powder by using NaOH, which can change the cellulose and lignin structures of the biomass while removing impurities in the biomass, and infiltrate trace 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 as to increase the number of catalytic active sites of the prepared material; then, the biochar obtained after Mg modification and pyrolysis carbonization is functionally enhanced by using 3-aminopropyltriethoxysilane (APTES) to improve the catalytic effect and material stability of the prepared material; finally, the optimal preparation parameters of APTES functionally enhanced 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 recycling and reuse performance of the prepared material are verified.

[0015] In order to efficiently remove organic pesticide residues in drinking water and ensure the safety of drinking water quality, the present invention uses WHMBC600 to activate PMS to produce ROS, which can achieve 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 that the biochar prepared by the present invention will be promoted and applied to the field of advanced oxidation water treatment for removing organic pollutants in water by activated oxidants, overcoming the defects of the prior art that biochar is used as an adsorbent to remove pollutants for a long time, low efficiency, difficult recovery, and high risk, and solving the current carbon-based catalysts. The catalytic activity is poor, the preparation operation is cumbersome, the production cost is high, the water quality adaptability and the recycling performance are poor.

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

[0017] A method for preparing biochar with high catalytic activity comprises the following steps:

[0018] (1) Raw material preparation

[0019] Select fresh water hyacinth, remove the roots, and clean it with deionized water; dry the water hyacinth until the water is completely removed; crush the dried water hyacinth, and sieve to obtain water hyacinth powder with fine and uniform particles.

[0020] (2) Preparation of modified biochar

[0021] The water hyacinth powder is placed in a NaOH solution and stirred, and then allowed to stand to obtain precipitated solid particles, which are washed with deionized water until neutral, and the obtained solid is dried to obtain WH.

[0022] WH and MgCl2 are added into pure water together, stirred and then allowed to stand; the solid obtained after solid-liquid separation is dried, and the dried solid is placed in a tubular furnace into which nitrogen is passed for pyrolysis, and after the pyrolysis is completed, it is cooled to room temperature; the magnesium-modified biochar obtained after pyrolysis and carbonization treatment is ground in a mortar, and then sieved to obtain a magnesium-modified biochar solid powder.

[0023] The magnesium-modified biochar solid powder is added to ethanol to form a magnesium-modified biochar dispersion, and then a certain amount of APTES is added and stirred to functionalize the magnesium-modified biochar; the dispersion after the reaction is filtered to obtain a functionally enhanced magnesium-modified biochar solid powder, and then the residual ethanol and unreacted APTES are rinsed off with deionized water, and finally the rinsed biochar solid is placed in an oven for drying to obtain WHMBC600.

[0024] Furthermore, in step (1), the water hyacinth is placed in an oven at 80° C. for drying until the water is completely removed. The mesh size of the sieve is 100 meshes.

[0025] Furthermore, in the step (2), the water hyacinth powder is placed in a 25 mM NaOH solution and stirred for 1 hour, and allowed to stand for 0.5 hours to obtain precipitated solid particles, which are then washed with deionized water until neutral, and the obtained solid is placed in an oven at 80° C. for drying to obtain WH.

[0026] Furthermore, in the step (2), the alkali-treated WH and MgCl2 are added to pure water in a mass ratio of 1:5, stirred for 12 hours using a magnetic stirrer, and then allowed to stand for 0.5 hours to obtain precipitated solid particles; the solid obtained after solid-liquid separation is placed in an 80°C oven for drying, and the dried solid is placed in a tubular furnace with nitrogen introduced at 600°C for pyrolysis for 2 hours, and after the 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 in a mortar, and then passed through a 100-mesh sieve to obtain a magnesium-modified carbon solid powder.

[0027] Furthermore, in the 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 stirring with a magnetic stirrer for 1 hour; the dispersion after the reaction is filtered through a 0.22 μm filter membrane to obtain a functionally enhanced magnesium-modified carbon solid powder, and then the residual ethanol and APTES on the solid powder are rinsed with deionized water, and finally the rinsed solid is placed in an 80° C. oven for drying to obtain WHMBC600.

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

[0029] The high catalytic activity biochar prepared by the present invention is used to remove pesticides in drinking water, and the pesticides include imidacloprid, fipronil, glyphosate and DDT. The specific method is: PMS is added to the drinking water containing pesticides, and then the high catalytic activity biochar is added, and the drinking water is shaken at a speed of 180r / min in a constant temperature water bath shaker at 25°C. The PMS is potassium persulfate.

[0030] Sampling was performed at set time intervals, and after adding excess sodium thiosulfate to quench the reaction, the sample was filtered through a 0.22 μm filter membrane, and then the concentration of pesticides in the water was determined using an ultra-high performance liquid chromatography-tandem triple quadrupole mass spectrometer.

[0031] Before the biomass of the present invention is pyrolyzed, it is first pretreated with NaOH alkali solution. The biomass raw material is treated with 25mM NaOH solution under stirring at room temperature for 1h. During the alkali solution pretreatment process, NaOH can change the cellulose and lignin structure of the biomass, interrupt the ester bonds and ether bonds in the lignin, partially dissolve or degrade it, and reduce the lignin content in the biomass. Specifically, alkali treatment can remove the aromatic rings and phenolic hydroxyl groups in 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 phenoloxyl radicals and other oxygen-containing free radicals; alkali solution pretreatment can also change the cellulose structure, increase the accessibility and reactivity of cellulose, convert part of the crystalline region of cellulose into an amorphous state, reduce the crystallinity of cellulose, thereby exposing more active sites, which is helpful for subsequent chemical modification and functionalization. In this process, the hydroxyl groups in cellulose can be activated to generate alkoxyl radicals; alkali washing can also degrade hemicellulose, further improving the accessibility and reactivity of biomass. The removal of hemicellulose can increase the porosity and specific surface area of ​​biomass and improve its adsorption and catalytic properties. The biomass pretreated with alkali solution is repeatedly rinsed with deionized water to neutrality to remove residual NaOH, and then the biomass pretreated with alkali 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. In the process of magnesium solution treatment, not only the metal content in the biomass is increased, but also the magnesium ions can penetrate deeply into the biomass. The biomass treated with magnesium solution is directly pyrolyzed. In this process, magnesium ions are converted into magnesium oxides and magnesium hydroxides, which are firmly bound to biochar to form stable nanostructures. Magnesium oxides and magnesium hydroxides form abundant active sites during pyrolysis. These structures not only provide efficient catalytic active centers, but also enhance the mechanical strength and thermal stability of biochar.

[0032] APTES is a silane coupling agent, and its chemical structure contains silane groups and amino groups. Silane groups can generate silanol groups through hydrolysis reaction, and then react with hydroxyl groups on the surface of biochar to form stable silicon-oxygen bonds, thereby improving the durability and stability of the material. Amino groups provide hydrophilicity and reactivity. They can form hydrogen bonds with water molecules, so they can improve the hydrophilicity of biochar, and can form coordination bonds with metal ions to enhance the fixation of metal ions, thereby increasing the density and stability of catalytic active centers. After APTES modification, functional groups such as amino groups are introduced to 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 oxidizing ability, thereby significantly improving the efficiency of activating oxidants to remove organic matter. The APTES functional enhancement treatment steps are to first disperse the magnesium-modified biochar in an ethanol solvent, then add an appropriate amount of APTES, stir the reaction for 1 hour, then wash it with deionized water and place it in an oven for drying. The hydrophilicity, catalytic activity and stability of the functionalized biochar have been significantly improved, and it is particularly suitable for removing organic pollutants such as imidacloprid in drinking water. In addition, if the biochar is modified with other metals, such as iron, copper, manganese, cobalt, etc., it can effectively inhibit the overflow of metal ions after APTES treatment and improve its secondary pollution problem. After functionalization, it needs to be fully washed with deionized water to remove the unreacted APTES on the surface of the material.

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

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

[0035] (2) The preparation method of the present invention sequentially pre-treats the water hyacinth powder with NaOH, Mg 2+ WHMBC600 was prepared through modification, pyrolysis carbonization, APTES functional enhancement and other treatment steps. The related treatments significantly enhanced the hydrophilicity, catalytic activity, water quality adaptability and recyclability of biochar.

[0036] (3) Compared with the prior art method of preparing biochar to remove organic matter from drinking water by adsorption and activation of oxidants, the high catalytic activity biochar WHMBC600 prepared by the present invention can activate PMS to efficiently remove different types of pesticides in drinking water. The removal rates of 10 mg / L aqueous solutions of different pesticides after being treated by the WHMBC600 / PMS system for 60 minutes were all close to 100%.

[0037] (4) Ability to efficiently activate PMS: Alkaline pretreatment, magnesium modification, pyrolysis and functionalization of WH in sequence significantly improved the specific surface area, pore structure and catalytic activity of the prepared biochar. The experimental results show that the efficiency of the high catalytic activity biochar WHMBC600 combined with PMS in removing imidacloprid from water is much higher than that of unmodified biochar (WHBC600), WHMBC600, PMS or WHBC600 / PMS combined in removing imidacloprid.

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

[0039] The highly catalytically active biochar of the present invention, its preparation method, and its application in removing imidacloprid from drinking water are further described below in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

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

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

[0042] Figure 3 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 system (experimental examples 2 to 5).

[0044] Figure 5 It is the mineralization degree of the solution in the system of Experimental Example 1 after 120 minutes of treatment.

[0045] Figure 6 This is the effect of NaOH concentration on the efficiency of WHMBC600 activated PMS oxidation to remove imidacloprid in Experimental Example 6.

[0046] Figure 7 This is the effect of the mass ratio of MgCl2 to WH in Experimental Example 7 on the efficiency of PMS oxidation removal by WHMBC600 activation.

[0047] Figure 8 This is the effect of pyrolysis temperature on the efficiency of WHMBC600 activated PMS oxidation to remove imidacloprid in Experimental Example 8.

[0048] Fig. 9 This is the effect of the amount of APTES added in Experimental Example 9 on the efficiency of WHMBC600 activating PMS to oxidatively remove imidacloprid.

[0049] Fig.10 This is the effect of the initial imidacloprid concentration in Experimental Example 10 on the removal efficiency of imidacloprid by the WHMBC600 / PMS system.

[0050] Fig.11 This is the effect of the amount of WHMBC600 added in Experimental Example 11 on the removal efficiency of imidacloprid by the WHMBC600 / PMS system.

[0051] Fig.12 This is the effect of the initial PMS concentration on the removal efficiency of imidacloprid by the WHMBC600 / PMS system in Experimental Example 12.

[0052] Fig.13 This is the effect of the initial pH of the solution in Experimental Example 13 on the removal efficiency of imidacloprid by the WHMBC600 / PMS system.

[0053] Fig.14 This is the effect of reaction temperature on the removal efficiency of imidacloprid by the WHMBC600 / PMS system in Experimental Example 14.

[0054] Fig.15 This is the effect of the WHMBC600 / PMS system on the removal efficiency of imidacloprid in drinking water under the actual drinking water matrix in Experimental Example 15.

[0055] Fig.16 This is the removal rate of different types of pesticides in the WHMBC600 / PMS system in Experimental Example 16.

[0056] Fig.17 The removal efficiency of imidacloprid by the WHMBC600 / PMS system after regeneration with different types of regeneration agents in Experimental Example 17. DETAILED DESCRIPTION

[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 hyacinth, remove the roots, and wash it with deionized water; ② Place the water hyacinth in an 80℃ oven to dry until the moisture is completely removed; ③ Use a high-speed grinder to crush the dried water hyacinth, and pass it through a 100-mesh sieve to obtain water hyacinth powder with fine and uniform particles.

[0064] Preparation of unmodified biochar: ① Place the water hyacinth powder in a tubular furnace with nitrogen and pyrolyze it at 600℃ for 2h, and cool it to room temperature (20-25℃) after the pyrolysis is completed; ② Use a mortar to grind the biochar obtained after pyrolysis and carbonization treatment, 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 Place water hyacinth powder in a 25 mM NaOH solution, stir with a magnetic stirrer for 1 h, let stand for 0.5 h to allow solid particles to settle, wash with deionized water until neutral, and dry the solid in an oven at 80 °C to obtain WH; ② Add WH to MgCl2 at a mass ratio of 1:5 (i.e. 2 g WH was mixed with 10gMgCl2), the mixture was added to 100mL pure water, stirred with a magnetic stirrer for 12h, and then allowed to stand for 0.5h to obtain solid particle sedimentation; ③ the solid obtained after solid-liquid separation was placed in an 80°C oven for drying, and then the dried solid was placed in a tubular furnace with nitrogen introduced and pyrolyzed at 600°C for 2h, and cooled to room temperature (20-25°C) after pyrolysis was completed; ④ the magnesium-modified biochar obtained after pyrolysis carbonization was ground in a mortar, and then passed through a 100-mesh sieve to obtain a magnesium-modified carbon solid powder; ⑤ 1g of magnesium-modified carbon solid powder was added to 50mL of ethanol to form a magnesium-modified biochar dispersion, and then 0.05mL of APTES, the magnesium-modified biochar was functionalized for 1 hour under the stirring action of a magnetic stirrer; ⑥ The dispersion after the reaction was filtered through a 0.22μm filter membrane, and the functionalized magnesium-modified carbon solid powder was filtered out and the residual ethanol and APTES were rinsed with deionized water. Finally, the rinsed solid was placed in an oven at 80℃ for drying to obtain the functionalized magnesium-modified water hyacinth-based biochar WHMBC600.

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

[0067] Among them, PMS uses potassium persulfate.

[0068] Experimental Example 2

[0069] Different from Experimental Example 1, WHMBC600 was not added to the experiment of removing imidacloprid in water in Experimental Example 2, which was used as a single PMS control group. The remaining steps were the same as those in Experimental Example 1.

[0070] Experimental Example 3

[0071] Different from Experimental Example 1, in Experimental Example 3, no PMS and WHMBC600 were added to remove imidacloprid from water. WHBC600 was added as a single unmodified biochar control group, and the rest of the steps were the same as in Experimental Example 1.

[0072] Experimental Example 4

[0073] Different from Experimental Example 1, in Experimental Example 4, no PMS was added to remove imidacloprid from water, and a single WHMBC600 control group was used. The remaining steps were the same as those in Experimental Example 1.

[0074] Experimental Example 5

[0075] Different from Experimental Example 1, WHMBC600 was not added in the experiment of removing imidacloprid from water in Experimental Example 5. WHBC600 and PMS were added as the control group for removing imidacloprid from water by activating PMS with unmodified water hyacinth-based biochar, and the rest of the steps were the same as Experimental Example 1.

[0076] Experimental Example 6

[0077] Different from Experimental Example 1, during the pretreatment of water hyacinth powder in Experimental Example 6, 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 after 60 minutes of reaction to determine the effect of NaOH concentration on the efficiency of WHMBC600 / PMS in removing imidacloprid from drinking water during alkaline solution pretreatment.

[0078] Experimental Example 7

[0079] Different from Experimental Example 1, in Experimental Example 7, 0.03 g of WHMBC6-1, WHMBC6-2, WHMBC6-3, WHMBC6-4, WHMBC6-5, WHMBC6-6, WHMBC6-7 and WHMBC6-8 were added to 50 mL of a solution containing imidacloprid (10 mg / L) and PMS (4 mM), and samples were taken to detect the imidacloprid concentration after 60 minutes of reaction to determine the optimal carbon-magnesium ratio in the magnesium modification process. The remaining steps were the same as in Experimental Example 1.

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

[0081] Experimental Example 8

[0082] Different from Experimental Example 1, the pyrolysis temperature of WHMBC600 in Experimental Example 8 was set to 400, 500, 600 and 700°C, respectively. Samples were taken to detect the imidacloprid concentration after 60 minutes of reaction to determine the effect of pyrolysis temperature on the efficiency of WHMBC600 in activating PMS to remove imidacloprid, and to determine the optimal pyrolysis temperature.

[0083] Experimental Example 9

[0084] Different from Experimental Example 1, in Experimental Example 9, 0, 0.01, 0.02, 0.03, 0.04, 0.05 and 0.06 mL APTES were used to enhance the function of magnesium-modified water hyacinth-based biochar, and samples were taken to detect the imidacloprid concentration after 60 minutes of reaction to determine the optimal amount of APTES added.

[0085] Experimental Example 10

[0086] Different from Experimental Example 1, the concentration of imidacloprid in the reaction solution of Experimental Example 10 was set to 5, 10 and 20 mg / L, respectively, to determine the effect of the initial imidacloprid concentration on the oxidative removal efficiency of imidacloprid in water by the WHMBC600 / PMS system. The remaining steps were the same as those in Experimental Example 1.

[0087] Experimental Example 11

[0088] Different from Experimental Example 1, in Experimental Example 11, 0.01, 0.02, 0.03, 0.04 and 0.05 g WHMBC600 (i.e., WHMBC600 at concentrations of 0.2, 0.4, 0.6, 0.8 and 1.0 g / L) were added to the reaction system to determine the optimal carbon dosage for the WHMBC600 / PMS system to oxidize and remove imidacloprid in water, and the remaining steps were the same as 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 set to 0.5, 1, 2, 4, 6 and 8 mM, respectively. Samples were taken to detect the imidacloprid concentration after 60 minutes of reaction to determine the effect of the initial PMS concentration on the oxidative removal efficiency of imidacloprid in water by the WHMBC600 / PMS system. The remaining steps were the same as in Experimental Example 1.

[0091] Experimental Example 13

[0092] Different from Experimental Example 1, Experimental Example 13 used 0.1 mM NaOH and 0.1 mM HCl to adjust the initial pH of the reaction solution. The initial pH of the solution was set to 3.0, 5.0, 6.5, 7.0 and 9.0, respectively, to determine the effect of the initial pH of the solution on the oxidative removal efficiency of imidacloprid in water by the WHMBC600 / PMS system. The remaining steps were the same as 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 set to 25, 35 and 45°C, respectively, to determine the effect of reaction temperature on the oxidative removal efficiency of imidacloprid in water by the WHMBC600 / PMS system. The remaining steps were the same as in Experimental Example 1.

[0095] Experimental Example 15

[0096] Different from Experimental Example 1, in Experimental Example 15, 50 mL of imidacloprid solution was prepared using tap water, and samples were taken to detect the imidacloprid concentration after 60 minutes of reaction to determine the efficiency of the WHMBC600 / PMS system in oxidative removal of imidacloprid under actual drinking water matrix conditions.

[0097] Experimental Example 16

[0098] The difference from Experimental Example 1 is that the imidacloprid in the target solution in Experimental Example 1 was replaced with glyphosate, DDT, and fipronil of the same concentration (10 mg / L), and samples were taken to detect the imidacloprid concentration after 60 minutes of reaction to determine the removal rate of different pesticides by the WHMBC600 / PMS system. The rest of the experimental steps were the same as in Experimental Example 1.

[0099] Experimental Example 17

[0100] Weigh 0.12g of WHMBC600 after use in the WHMBC600 / PMS system, add it to 50mL methanol, 0.2mol / L NaOH, and 0.2mol / L HCl respectively, then place it in a constant temperature (25°C) water bath shaker for 3h, and then place the filtered WHMBC600 in an 80°C oven for drying to obtain the regenerated WHMBC600. Add 0.03g of regenerated WHMBC600 to the WHMBC600 / PMS reaction system, take a sample to detect the imidacloprid concentration after 60min of reaction, repeat the above steps 4 times to determine the regeneration performance of WHMBC600, and 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 This is the SEM image of WHBC600. Figure 2 This is the SEM image of WHMBC600. 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 and has a larger specific surface area, which can provide more active sites, thereby improving the catalytic effect of the material.

[0103] Depend on Figure 3 It can be seen that the I of WHMBC600 after magnesium modification D / I G It increased from 0.79 of unmodified WHBC600 to 0.87, indicating that the modified and functionalized WHMBC600 contained more C atom crystal defects, which could provide more activation sites for the activated oxidant to degrade and remove pollutants.

[0104] Depend on 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] Depend on Figure 5 It can be seen that the imidacloprid aqueous solution reached a higher mineralization degree (TOC removal rate was 45.4%) after being treated with the WHMBC600 / PMS system for 120 minutes, 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] Depend on Figure 6It can be seen that the concentration of NaOH during water hyacinth powder pretreatment has a significant effect on the efficiency of WHMBC600 in activating PMS to oxidize and remove imidacloprid in water. When the NaOH concentration is 25mM, the activation performance of WHMBC600 is the highest, and too high or too low a concentration will significantly reduce the activation performance of WHMBC600.

[0107] Depend on Figure 7 It can be seen 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 is ≤5, the activation performance of WHMBC600 gradually improves with the increase of its mass ratio; when the mass ratio of MgCl2 to WH is further increased, the efficiency of WHMBC600 in activating PMS to degrade imidacloprid does not change significantly. Therefore, considering the removal efficiency of the target and the material preparation cost, the optimal mass ratio of WH to MgCl2 is 1:5.

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

[0109] Depend on Fig. 9 It can be seen that the hydrophilicity, catalytic activity and stability of biochar after pyrolysis treatment can be improved by APTES functional enhancement treatment, so it can significantly improve the efficiency of WHMBC600 in activating PMS to oxidize and remove imidacloprid in water. 1g of pyrolysis biochar was dispersed in 50mL of ethanol, and then 0.05mL of APTES was added to the dispersion for functionalization treatment. The performance of activating PMS was the highest. When the amount of APTES added was ≤0.05mL, the activation performance of WHMBC600 increased with the increase of APTES addition, but further increasing the amount of APTES added caused the pore structure of WHMBC600 to be blocked, resulting in a decrease in the activation performance of WHMBC600. Therefore, the optimal amount of APTES added was 0.05mL.

[0110] Depend on Fig.10It can be seen that as the concentration of imidacloprid in the WHMBC600 / PMS system increases 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%. The concentration of imidacloprid in drinking water is much lower than this concentration (generally μg / L level), so 100% removal of the target can be achieved in a shorter time.

[0111] Depend on Fig.11 It can be seen that the dosage of WHMBC600 has a significant effect on the efficiency of oxidative removal of imidacloprid in water by the WHMBC600 / PMS system. When the dosage of WHMBC600 increased from 0.2g / L to 0.6g / L, that is, the dosage increased from 0.01g to 0.03g, the removal rate of imidacloprid increased significantly. However, when the dosage of WHMBC600 was further increased from 0.6g / L to 1.0g / L, that is, the dosage increased from 0.03g to 0.05g, the increase in the removal rate of imidacloprid was small. Therefore, considering the utilization efficiency of the catalyst and the process treatment cost, 0.6g / L, that is, the dosage of 0.03g, was selected as the optimal dosage of WHMBC600.

[0112] Depend on Fig.12 It can be seen that the initial PMS concentration has a significant effect on the efficiency of oxidative removal of imidacloprid in the WHMBC600 / PMS system. When the initial PMS concentration increases from 0.5mM to 4mM, the removal rate of imidacloprid increases significantly, but when the initial PMS concentration further increases to 8mM, the removal rate of imidacloprid decreases significantly. This is because, when the initial PMS concentration is low, increasing the amount of PMS added can significantly increase the amount of ROS generated in the WHMBC600 / PMS system, so it can significantly improve the removal rate of imidacloprid in the system; 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 4mM.

[0113] Depend on Fig.13It can be seen that when the initial pH of the solution increases from 3.0 to 9.0, the removal rate of imidacloprid in the WHMBC600 / PMS system shows a trend of increasing first 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 as high as 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 to 9 (the pH value of natural water is generally 6.5 to 8.5), the WHMBC600 / PMS system can achieve a high removal rate of imidacloprid.

[0114] Depend on Fig.14 It can be seen that the removal rate of imidacloprid in the WHMBC600 / PMS system shows a trend of increasing first and then decreasing with the increase of reaction temperature. When the reaction temperature is 25℃, the removal rate of imidacloprid after 60min treatment is 97.7%; when the reaction temperature is 35℃ and 45℃, the removal rate of imidacloprid after 60min treatment is 100%. Therefore, when the reaction temperature is 25-45℃, the WHMBC600 / PMS system can effectively remove imidacloprid in water.

[0115] Depend on Fig.15 It can be seen that in the WHMBC600 / PMS system, the removal rate of imidacloprid in tap water matrix is ​​lower than that in pure water, indicating that the coexisting ions and organic matter in water will consume the ROS generated in the system, but the removal rate of imidacloprid (10 mg / L) in tap water after 60 minutes 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] Depend on Fig.16 It can be seen that when the WHMBC600 / PMS system is used to treat simulated water samples of different types of pesticides for 60 minutes, 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 effectively remove different types of pesticides in drinking water.

[0117] Depend on Fig.17It can be seen that the use of different regeneration agents to regenerate the used biochar in the WHMBC600 / PMS system can achieve relatively good regeneration efficiency. Among them, the regeneration effect is best when NaOH is used as the regeneration agent. When the imidacloprid aqueous solution is treated with PMS activated by four-cycle regeneration WHMBC600 for 60 minutes, the removal rate of imidacloprid still reaches 90.1%. When methanol and hydrochloric acid are used as catalysts, the efficiency of four-cycle regeneration can reach 72.1% and 67.5% respectively. Therefore, WHMBC600 in the method of the present invention has stable and efficient reuse performance.

[0118] From the above experimental results, we can see that:

[0119] The present invention can change the cellulose structure of the raw material, remove lignin, generate phenoloxy radicals and alkoxy radicals by pre-treating the biomass raw material with alkali solution, and these free radicals can provide additional electron donors or acceptors, promote the electron transfer process in the catalytic reaction, and thus better activate PMS. After the alkali solution pre-treatment, it is rinsed to neutrality with deionized water and subjected to magnesium modification and one-step pyrolysis, forming a stable magnesium oxide and magnesium hydroxide structure on the surface and inside of the biochar, further improving its catalytic activity. Finally, the APTES functional strengthening treatment is used to improve its catalytic performance and stability, and the APTES functionalized magnesium-modified water hyacinth-based biochar (WHMBC600) is successfully prepared. The material has a larger specific surface area, a richer pore structure, a better catalytic activity, a stronger ability to adapt to water quality, and a better reusability.

[0120] Different from the traditional technology of using NaOH to activate biochar, the present invention uses a certain concentration of NaOH aqueous solution to pretreat water hyacinth powder, which changes the cellulose and lignin structure of the biomass, infiltrates trace amounts of alkali into the biomass, introduces more hydrophilic groups such as hydroxyl groups, and is beneficial to enhance the effect of subsequent Mg modification.

[0121] The present invention uses a MgCl2 solution of appropriate concentration to immerse and stir the biomass after alkali treatment, which is conducive to the formation of Mg(OH)2 micro-flocs on the surface of the biomass and uniform distribution on the surface of the biomass raw material. The generated Mg(OH)2 micro-flocs also promotes the Mg 2+ Adsorption on the biomass surface enhances the Mg loading on the biomass material.

[0122] The present invention performs pyrolysis and carbonization treatment on the biomass modified by Mg impregnation and stirring under suitable temperature conditions, and the pyrolysis object is the biomass loaded with Mg(OH)2 micro-flocs and adsorbed with Mg 2+ , water hyacinth powder is infiltrated with trace amounts of alkali, and the related effects of its internal components make the biochar generated after biomass pyrolysis have a larger specific surface area, a more developed pore structure and more catalytic active sites.

[0123] The present invention uses APTES to perform functionalization treatment on biochar dispersed in ethanol, thereby further improving the catalytic performance and repeated recycling performance of WHMBC600.

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

[0125] The method for preparing WHMBC600 by the technology of the present invention is simple in procedure, low in cost, suitable for large-scale production, and has great potential for engineering application. The high catalytic activity biochar prepared by the present invention does not produce toxic and harmful metal ions that cause secondary water pollution, and can show good stability and reusability in practical applications, providing an economically feasible and environmentally friendly solution to solve the problem of pesticide pollution in drinking water and the resource utilization of water hyacinth.

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

[0127] The embodiments described above are merely descriptions of preferred implementation modes of the present invention and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for preparing biochar with high catalytic activity, characterized in that: The following steps are involved: (1) Raw material preparation Select fresh water hyacinth, remove the roots, and clean it with deionized water; dry the water hyacinth until the water is completely removed; crush the dried water hyacinth, and sieve to obtain water hyacinth powder with fine and uniform particles; (2) Preparation of modified biochar The water hyacinth powder is placed in a NaOH solution and stirred, and allowed to stand to obtain precipitated solid particles, which are then washed with deionized water until neutral, and the obtained solid is dried to obtain an alkali-treated water hyacinth powder, which is recorded as WH; Add WH and MgCl2 into pure water, stir for a certain period of time and then let it stand; dry the solid obtained after solid-liquid separation, place the dried solid in a tubular furnace with nitrogen gas for pyrolysis, and cool it to room temperature after the pyrolysis is completed; grind the magnesium-modified biochar obtained after pyrolysis carbonization in a mortar, and then sieve it to obtain magnesium-modified carbon solid powder; The magnesium-modified carbon solid powder is added to ethanol to form a magnesium-modified biochar dispersion, a certain amount of 3-aminopropyltriethoxysilane is added to the dispersion, and the magnesium-modified biochar is functionalized under stirring conditions; the dispersion after the reaction is filtered to filter out the obtained magnesium-modified carbon solid powder with enhanced functionality, the residual ethanol and 3-aminopropyltriethoxysilane are rinsed off with deionized water, and the rinsed solid is dried to obtain functionalized magnesium-modified water hyacinth-based biochar.

2. The method for preparing biochar with high catalytic activity according to claim 1, characterized in that: In the step (1), the water hyacinth is placed in an oven at 80° C. for drying until the moisture is completely removed.

3. The method for preparing biochar with high catalytic activity according to claim 2, characterized in that: In the step (1), the mesh size of the sieve is 100 meshes.

4. The method for preparing biochar with high catalytic activity according to claim 3, characterized in that: In the step (2), the water hyacinth powder is placed in a 25 mM NaOH solution, stirred with a magnetic stirrer for 1 hour, and then allowed to stand for 0.5 hours to obtain precipitated solid particles, which are then washed with deionized water to neutrality, and the obtained solid is placed in an oven at 80° C. for drying.

5. The method for preparing biochar with high catalytic activity according to claim 4, characterized in that: In the step (2), the alkali-treated WH and MgCl2 are added to pure water in a mass ratio of 1:5, stirred for 12 hours using a magnetic stirrer, and then allowed to stand for 0.5 hours to obtain precipitated solid particles; the solid obtained after solid-liquid separation is placed in an 80°C oven for drying, and the dried solid is placed in a tubular furnace into which nitrogen is introduced and pyrolyzed at 600°C for 2 hours, and after the pyrolysis is completed, it is cooled to room temperature of 20-25°C; the magnesium-modified biochar obtained after the pyrolysis carbonization treatment is ground in a mortar, and then passed through a 100-mesh sieve to obtain a magnesium-modified carbon solid powder.

6. The method for preparing biochar with high catalytic activity according to claim 5, characterized in that: In the step (2), magnesium-modified carbon solid powder is added to ethanol to form a magnesium-modified biochar dispersion, and then a certain amount of 3-aminopropyltriethoxysilane is added to functionalize the magnesium-modified biochar under stirring with a magnetic stirrer for 1 hour; the dispersion after the reaction is filtered through a 0.22 μm filter membrane to filter out the obtained functionally enhanced magnesium-modified carbon solid powder, and the residual ethanol and 3-aminopropyltriethoxysilane are rinsed with deionized water, and finally the rinsed solid is placed in an 80° C. oven for drying to obtain a functionalized magnesium-modified water hyacinth-based biochar, which is recorded as WHMBC600.

7. The method for preparing biochar with high catalytic activity according to claim 6, characterized in that: The mass volume ratio of the magnesium-modified carbon solid powder to 3-aminopropyltriethoxysilane is 1:0.

05.

8. Biochar with high catalytic activity obtained by the preparation method according to any one of claims 1 to 7.

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

10. The use of the highly catalytically active biochar in removing pesticides from drinking water according to claim 9, characterized in that: Peroxymonosulfate at a concentration of 4 mM was added to the drinking water containing pesticides, and then 0.03 g of highly catalytically active biochar was added, and the mixture was shaken in a constant temperature water bath shaker to remove the pesticides from the drinking water.

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