Method for preparing a remediation agent for water and soil contaminated by the herbicide sulfometuron-methyl and use thereof
By modifying corn straw biochar with nano-zero-valent iron and loading it with microbial agents, the problems of low adsorption capacity, easy saturation, and high cost in the remediation of water and soil polluted by mefensulfuron-methyl herbicide were solved, achieving efficient and rapid degradation of pollutants.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- EAST CHINA UNIV OF SCI & TECH
- Filing Date
- 2024-05-09
- Publication Date
- 2026-05-12
AI Technical Summary
Existing biochar and nano-zero-valent iron modified biochar materials have problems such as low adsorption capacity, easy saturation, limited degradation effect and high cost when treating water and soil polluted by methasulfuron herbicide. In addition, nano-zero-valent iron is prone to agglomeration, and the microbial remediation effect is unstable.
Nano-zero-valent iron modified corn straw biochar material was loaded with microbial agents and prepared by carbothermal reduction method. Degrading bacteria were then fixed on it to form a composite material for the remediation of polluted water and soil.
This approach achieves efficient, rapid, and green remediation of mefensulfuron herbicide, reduces material costs, enhances the dispersibility and microbial activity of nano-zero-valent iron, and improves the ability to completely degrade mefensulfuron.
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Figure CN118598373B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the technical field of pesticide pollution remediation materials in environmental protection, specifically relating to the preparation method and application of a remediation agent for water and soil polluted by methimazole herbicide, particularly concerning the remediation of water and soil polluted by methimazole herbicide. Background Technology
[0002] Methimazole is a non-selective herbicide mainly used for weed control in various types of non-arable land such as woodlands, wastelands, and forest firebreaks, as well as in orchards with deep-rooted fruit trees. Methimazole is effective against monocots, dicots, and shrubs, and is characterized by good systemic activity, a wide weeding range, and a long residual effect. However, improper use of methimazole can cause phytotoxicity, affecting crop growth and even rendering farmland unsuitable for normal planting for one to two years. Studies have shown that methimazole can inhibit growth indicators in maize plants such as plant height, ear length, and kernel size; low concentrations of methimazole have adverse effects on potato roots and tubers, potentially leading to abnormal growth or functional impairment, while high concentrations can significantly increase the number of deformed potato tubers.
[0003] Biochar is a carbon-rich material prepared from biomass through anaerobic high-temperature pyrolysis. Its abundant surface functional groups, aromaticity, and negative surface charge give it a strong adsorption capacity for both organic and inorganic pollutants. However, biochar struggles to completely degrade organic pollutants, leading to secondary pollution. Nano-zero-valent iron (nZVI) can effectively remove organic pollutants based on its redox properties, but NZVI particles tend to agglomerate and are easily oxidized, reducing reactivity; furthermore, excessive dosage can cause environmental toxicity. On the other hand, the use of microbial co-metabolism to degrade herbicides is gaining attention; however, the effectiveness of microbial remediation is easily affected by environmental factors, resulting in unstable remediation effects. Therefore, NZVI-modified biochar composite microbial agents not only improve the degradation effect on methasulfuron-methyl but also reduce the agglomeration tendency of NZVI, enhancing its reactivity. It also acts as a carrier for microorganisms, enhancing their activity and further improving the adsorption performance and pollutant removal capacity of biochar. Currently, some researchers have explored and studied related materials, as shown below:
[0004] (1) CN202111416275.X discloses a biochar-supported microbial material soil remediation agent and its preparation method. This invention can effectively solidify and stabilize lead, reduce the harshness of the environmental conditions required by traditional microorganisms, and reduce the production cost. It is conducive to the high-value utilization of corn straw and has broad industrial prospects and market value. (2) CN201811481389.0 discloses a method for biochar-supported surfactant coupled with microbial plants to remediate petroleum-contaminated soil. This invention adopts in-situ remediation technology, which does not damage the environment or cause secondary pollution during the remediation process. It is green and environmentally friendly and realizes a composite remediation mode with good green circular remediation effect. (3) AU2020103433(A4) discloses a method for preparing magnetic biochar using kitchen waste. By recycling kitchen waste, environmental hazards are reduced and good social and environmental benefits are achieved. (4) CN202210741637.0 discloses a method for preparing straw biochar loaded with nano-zero valent iron materials and its application. It has the advantages of low cost, good adsorption performance, non-agglomeration, high removal efficiency, simple process and convenient operation. It can be applied to the in-situ remediation or pumping treatment of heavy metal lead and new organic pollutant sulfamethoxazole complex pollution. (5) CN202210405459.4 discloses a method for preparing magnetic sludge biochar that can be applied to the efficient degradation of sulfamethoxazole by activated persulfate. It can achieve efficient degradation of sulfamethoxazole in water, and its strong magnetism can enable its recycling. (6) CN201611259617.0 discloses corn straw biochar and its use in adsorbing herbicides. This corn straw biochar has excellent adsorption effect on herbicides.
[0005] However, current applications of biochar and modified biochar materials do not address the remediation of water and soil contaminated by mefensulfuron-methyl herbicide. Existing biochars, such as cyanobacteria-based biochar, eucalyptus biochar, and straw biochar, have low adsorption capacity for organic pollutants, are easily saturated, and pose a risk of releasing pollutants after saturation, and cannot completely remove pollutants. Nano-zero-valent iron-modified biochar materials exhibit low removal rates and limited degradation effects for organic pollutants, and their remediation costs are high. Therefore, there is an urgent need to provide a new remediation agent for water and soil contaminated by mefensulfuron-methyl herbicide, along with its preparation method and applications. Summary of the Invention
[0006] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing and applying a methamidosulfuron herbicide-contaminated water and soil remediation agent. Specifically, it relates to a methamidosulfuron herbicide-contaminated water and soil remediation agent made of nano-zero-valent iron modified corn straw biochar material loaded with microbial agents, which can efficiently remove methamidosulfuron herbicide from water and soil.
[0007] The specific technical solution adopted in this invention is as follows:
[0008] In a first aspect, the present invention provides a method for preparing a remediation agent for water and soil contaminated by mefensulfuron-methyl herbicide, as detailed below:
[0009] Corn stalk powder was added to an aqueous solution containing ferric chloride hexahydrate, stirred and separated, and the solidified material was dried to obtain a composite material precursor. The composite material precursor was then subjected to a carbothermal reduction method, using hydrogen or carbon monoxide generated by pyrolysis under high temperature and oxygen-deficient conditions to reduce ferric iron, thereby generating nano-zero ferric iron that was loaded onto the surface of biochar to obtain nano-zero ferric iron modified biochar. The fermentation broth of degrading bacteria was fixed onto the nano-zero ferric iron modified biochar by physical adsorption, and after freeze-drying, a methamidosulfuron herbicide-contaminated water and soil remediation agent was obtained.
[0010] Preferably, the preparation process of the composite material precursor is as follows:
[0011] Corn stalk powder was washed with water and dried, then added to an aqueous solution containing ferric chloride hexahydrate and stirred thoroughly to obtain a suspension containing a solidified product. The suspension was left to stand at room temperature for 24 hours, and then centrifuged to obtain the lower solidified product. The solidified product was dried at 80°C to obtain the composite material precursor.
[0012] Preferably, in the composite material precursor, the mass ratio of corn stalk powder to ferric chloride hexahydrate is 1:2.7.
[0013] Preferably, the carbothermic reduction method is as follows:
[0014] The composite material precursor was pyrolyzed at 700°C for 2 hours in an inert gas atmosphere and then cooled to room temperature to obtain nano-zero-valent iron modified biochar.
[0015] Furthermore, the inert gas is nitrogen, with a flow rate of 80 mL / min; the heating rate during pyrolysis is 5 °C / min, and the cooling rate during cooling is 10 °C / min.
[0016] Preferably, the fermentation broth of the degrading bacteria is Bacillus megaterium.
[0017] Furthermore, the particle size of the nano-zero-valent iron modified biochar is 0.25-0.5 mm, the immobilization time of the degrading bacteria fermentation broth is 26 hours, and the mass-to-volume ratio of the nano-zero-valent iron modified biochar to the degrading bacteria fermentation broth is 6%.
[0018] Preferably, the physical adsorption method refers to immersing nano-zero-valent iron modified biochar in the fermentation broth of degrading bacteria and fixing it by shaking at 30°C and 150 rpm.
[0019] Secondly, the present invention provides a methimazole herbicide-contaminated water and soil remediation agent obtained by any of the preparation methods described in the first aspect.
[0020] Thirdly, the present invention provides an application of the methimazole herbicide-contaminated water and soil remediation agent described in the second aspect in the remediation of water and soil contaminated by methimazole herbicide.
[0021] Compared with the prior art, the present invention has the following advantages:
[0022] (1) The raw material for the preparation of the product of this invention is waste corn stalk residue, which is widely available and inexpensive. The resource utilization of waste reduces the high cost of composite materials. At the same time, it leverages the advantages of high carbon content and dense porous structure of corn stalks, solves the environmental problems caused by large amounts of waste corn stalks, and proposes a new strategy for pollution reduction and carbon reduction.
[0023] (2) The nano-zero-valent iron modified corn straw biochar composite microbial agent prepared in this invention is a ternary composite material, which is formed by combining nano-zero-valent iron and corn straw biochar, and then combining them with microbial agents. The loading of nano-zero-valent iron can maintain its high reactivity and increase its dispersibility and stability. The loading of microorganisms can achieve the complete degradation of methasulfuron, and the nano-zero-valent iron modified biochar as a carrier can enhance the adaptability of microorganisms to the environment and strengthen their activity.
[0024] (3) This invention proposes a novel modification approach in the material preparation process: co-impregnation of ferric chloride hexahydrate and corn stalks, followed by a carbothermal reduction method. This method utilizes the reducing gases released by the corn stalk biochar under high-temperature conditions to achieve one-step pyrolysis, resulting in nano-zero-valent iron modified corn stalk biochar. This eliminates the need for adding reducing agents and secondary pyrolysis, effectively saving raw materials and energy consumption, and significantly reducing product preparation costs. Combining nano-zero-valent iron modification with microbial loading technology, the composite material overcomes the tendency of nano-zero-valent iron to aggregate, achieving rapid and efficient removal of mefensulfuron herbicide. It also enhances microbial activity and strengthens the degradation of mefensulfuron, making it a multifunctional material suitable for in-situ remediation and improvement of contaminated soil.
[0025] (4) The methimazole herbicide remediation agent of the present invention has the advantages of rapid, efficient and green removal of methimazole herbicide from water and soil, and has important application value in the actual process of remediating water bodies, farmland or site soil polluted by methimazole herbicide. Attached Figure Description
[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0027] Figure 1 These are diagrams showing the removal effect of methimazole herbicide on polluted water and soil by the soil remediation agent provided in Examples 4-6 of this invention.
[0028] Figure 2 This is a diagram showing the removal effect of methimazole herbicide on polluted water and soil by the soil remediation agent provided in Example 7 of the present invention on different concentrations of methimazole in the soil.
[0029] Figure 3 Scanning electron microscopy of the surface of water bodies and soil remediation agents contaminated by methimazole herbicide provided in Example 1 of this invention. Figure 1 .
[0030] Figure 4 Scanning electron microscopy of the surface of the water and soil remediation agent material for methimazole herbicide pollution provided in Example 1 of this invention. Figure 2 .
[0031] Figure 5 This is a scanning electron microscope image of the surface of nano-zero-valent iron modified biochar in Example 1 of the present invention.
[0032] Figure 6 This is a response surface plot showing the optimized preparation steps of the herbicide methimazole for water and soil remediation in Example 2 of the present invention.
[0033] Figure 7 The graph shows the degradation rate of methasulfuron by the four degrading bacteria in Example 3. Detailed Implementation
[0034] The present invention will be further described and illustrated below with reference to the accompanying drawings and specific embodiments. The technical features of each embodiment of the present invention can be combined accordingly, provided that there is no mutual conflict.
[0035] This invention provides a method for preparing a remediation agent for water and soil contaminated by mefensulfuron-methyl herbicide. The specific preparation method is as follows:
[0036] S1: Add corn stalk powder to an aqueous solution containing ferric chloride hexahydrate, stir and separate, then dry the solidified material to obtain the composite material precursor.
[0037] As a preferred embodiment of the present invention, the preparation process of the composite material precursor is as follows:
[0038] Corn stalk powder was washed with water and dried, then added to an aqueous solution containing ferric chloride hexahydrate and stirred thoroughly to obtain a suspension containing a solidified product. The suspension was left to stand at room temperature for 24 hours, and then centrifuged to obtain the lower solidified product. The solidified product was dried at 80°C to obtain the composite material precursor.
[0039] In a preferred embodiment of the present invention, the mass ratio of corn stalk powder and ferric chloride hexahydrate in the composite material precursor is 1:2.7.
[0040] S2: The obtained composite precursor is subjected to carbothermal reduction, where hydrogen or carbon monoxide generated by pyrolysis under high-temperature and oxygen-deficient conditions is used to reduce ferric iron (Fe(III)), thereby loading nano-zero ferric iron onto the surface of biochar to obtain nano-zero ferric iron modified biochar. The nano-zero ferric iron modified biochar obtained in this step is distributed in a sheet-like manner.
[0041] As a preferred embodiment of the present invention, the specific operation steps of the carbothermic reduction method are as follows:
[0042] The composite precursor obtained from S1 was pyrolyzed in a tube furnace at 700°C for 2 hours under an inert gas atmosphere, and then cooled to room temperature to obtain nano-zero-valent iron modified biochar.
[0043] Specifically, nitrogen can be used as the inert gas, with a flow rate of 80 mL / min; in the tube furnace, the heating rate during pyrolysis is 5 °C / min, and the cooling rate during cooling is 10 °C / min.
[0044] S3: The fermentation broth of the degrading bacteria was fixed onto the obtained nano-zero-valent iron modified biochar by physical adsorption, and then freeze-dried to obtain a remediation agent for water and soil polluted by methasulfuron herbicide.
[0045] As a preferred embodiment of the present invention, the physical adsorption method refers to culturing Bacillus megaterium to the logarithmic phase, then immersing nano-zero-valent iron modified biochar in the fermentation broth of the degrading bacteria, and fixing it by shaking in a shaker at 30°C and 150 rpm.
[0046] In a preferred embodiment of the present invention, the fermentation broth for the degradation bacteria can be Bacillus megaterium. In this case, the particle size of the nano-zero-valent iron modified biochar is 0.25-0.5 mm, the immobilization time of the fermentation broth for the degradation bacteria is 26 h, and the mass-to-volume ratio of the nano-zero-valent iron modified biochar to the fermentation broth for the degradation bacteria is 6%.
[0047] In other words, before proceeding to step S3, the obtained nano-zero-valent iron modified biochar of various particle sizes can be screened to select nano-zero-valent iron modified biochar with a particle size of 0.25-0.5mm for step S3, in order to obtain a better treatment effect.
[0048] The methamidosulfuron herbicide-contaminated water and soil remediation agent obtained by the above preparation method can be used to remediate water and soil contaminated by methamidosulfuron herbicide. When this remediation agent is used to remediate soil, the dosage is 0.1 wt% to 1 wt%.
[0049] The preparation method and corresponding effects of the present invention will be specifically illustrated below through examples.
[0050] Example 1
[0051] This embodiment yields a methamidosulfuron-methyl herbicide-contaminated water and soil remediation agent. The preparation method is as follows:
[0052] Ferric chloride hexahydrate was dissolved in deionized water to obtain a mixed solution. Corn stalk powder was washed and dried with deionized water, then added to the mixed solution and stirred to obtain a suspension containing a solid (the mass ratio of corn stalk powder to ferric chloride hexahydrate was 1:2.7). The suspension was placed at room temperature for 24 hours. The suspension was centrifuged to obtain the lower solid layer. The solid was dried in an 80°C oven to obtain the composite material precursor. The composite material precursor was calcined in a tube furnace at 700°C for 2 hours under a nitrogen atmosphere (flow rate of 80 mL / min) (heating rate of 5°C / min, cooling rate of 10°C / min), and then cooled to room temperature to obtain nano-zero-valent iron modified biochar (nZVI-BC). Figure 5 As shown, nZVI-BC exhibits a distinct porous structure, with nano-zero-valent iron particles fixed on the surface or within the pores of the biochar. Loading nano-zero-valent iron particles onto biochar can, to some extent, inhibit their aggregation and maintain reactivity. Bacillus megaterium was cultured to the logarithmic growth phase, and nZVI-BC was added to the Bacillus megaterium fermentation broth. The mixture was then fixed in a shaker at 30°C and 150 rpm for 26 hours to obtain a remediation agent for water and soil contaminated with methasulfuron-methyl herbicide.
[0053] Figure 3 and Figure 4 The images show electron microscope (EM) images of the water and soil remediation agents contaminated by the methimazole herbicide obtained in this embodiment. Figure 3 The typical pore structure of nZVI-BC was still present in the water and soil remediation agent contaminated by methasulfuron-methyl observed at a scale of 20 μm, indicating that the basic structure of the material was not destroyed when loaded with Bacillus megaterium. Figure 4 The images show the remediation agents for water and soil contaminated by methasulfuron-methyl herbicide observed at a scale of 5 μm. It can be seen that Bacillus megaterium is attached to the surface of nZVI-BC, indicating that the compound bacterial agent was successfully prepared.
[0054] The material prepared by this invention can solve the problems of easy saturation of biochar adsorption, the risk of desorption and re-release of herbicides, and the inability to completely degrade herbicides. At the same time, it solves the problems of easy aggregation and oxidation of nano-zero-valent iron during the pollution remediation process, as well as the problems of the activity of methasulfuron-degrading bacteria being easily affected by the environment and the unstable performance. Finally, the prepared nZVI / BC-microbial composite agent (i.e., methasulfuron-contaminated water and soil remediation agent) has a larger specific surface area, high adsorption performance and high reactivity, and can achieve the purpose of efficiently removing methasulfuron-contaminated water and soil.
[0055] Example 2
[0056] To optimize the preparation steps of the herbicide-treated methamidosulfuron-methyl water and soil remediation agent, this embodiment discusses and optimizes parameters such as the particle size, immobilization time, and carbon-spore dosage ratio of nano-zero-valent iron modified biochar in S3, as detailed below:
[0057] The nZVI-BC particle size range was divided into <0.25mm, 0.25mm-0.5mm, and >0.5mm; the immobilization time was divided into 12h, 24h, and 36h; and the carbon-based bacteria dosage ratio (g / L) was divided into 2%, 5%, and 10%. Based on the results of the single-factor experiments, a Box-Behnken design was performed using DesignExpert 13 software, with the degradation rate of mefensulfuron as the evaluation index, to obtain the optimal preparation conditions for the mefensulfuron herbicide-contaminated water and soil remediation agent. The experimental design is shown in Table 1.
[0058] Table 1
[0059]
[0060]
[0061] Note: A: Biochar particle size, -1 (<0.25mm), 0 (0.25mm-0.5mm), 1 (>0.5mm); B: Immobilization time, -1 (12h), 0 (24h), 1 (48h); C: Charcoal-to-organic bacteria ratio, -1 (2%), 0 (5%), 1 (10%).
[0062] The results show that the model has good correlation (R). 2 =0.95). Among the three influencing factors of nano-zero valent iron modified biochar particle size, immobilization time and biochar-to-microorganism ratio, the biochar-to-microorganism ratio had no significant effect on the degradation rate of methasulfuron (p>0.05), while the biochar particle size (p<0.05) and immobilization time (p<0.05) had significant effects on the degradation rate of methasulfuron.
[0063] like Figure 6As shown, response surface plots were plotted to further visually observe the effects of the three factors on the degradation rate of methasulfuron. Analysis of the results revealed that the optimal preparation conditions for the degradation of methasulfuron by the immobilized bacterial agent were: biochar particle size of 0.25-0.5 mm, immobilization time of 26 hours, and a biochar-to-bacterial dosage ratio of 6%.
[0064] Example 3
[0065] To optimize the preparation steps of the herbicide-treated water and soil remediation agent, this embodiment also screened and optimized the types of degrading bacteria fermentation broth and degradation conditions, as detailed below:
[0066] Through a survey of major microbial culture centers, including the China General Microbiological Culture Collection Center (CGMCC), the China Industrial Microbiological Culture Collection Center (CICC), the American Type Culture Collection Center (ATCC), and the China Agricultural Microbiological Culture Collection Center (ACCC), and considering both the availability of strains and their matching with the characteristics of the isolation sources, *Bacillus megaterium*, *Pseudomonas fluorescens*, *Escherichia coli*, and *Mycobacterium virgaurea* were selected to investigate their degradation effects on bensulfuron-methyl and mefensulfuron-methyl. Basic information on the strains is as follows:
[0067] Strain 1: Bacillus megaterium:ACCC 10881 (rice rhizosphere—Capital Normal University, Luanxian County, Tangshan City, Hebei Province, 2006)
[0068] Strain 2: Escherichia coli (Fermentation Industry - School of Bioengineering, East China University of Science and Technology)
[0069] Strain 3: Mycobacterium neoaurum: ATCC 25795 (Soil - Wuhan Warner Biotechnology Co., Ltd., Wuhan, Hubei Province, 1994)
[0070] The three degrading bacteria were inoculated into 50 mL of LB liquid medium and cultured in a constant temperature shaking incubator at 150 rpm and 30 ℃ until the logarithmic phase. They were then centrifuged at 8000 r / min and 4 ℃ for 5 min using a high-speed refrigerated centrifuge. The precipitate was washed three times with MSM culture medium, resuspended, and a bacterial suspension with OD600 = 1.0 was prepared as the seed culture.
[0071] The prepared 100 mg / L stock solution of methasulfuron was diluted to 25 mg / L using MSM medium. The inoculum amount of each strain was 1%, and each treatment group was replicated in triplicate. The cultures were incubated at 30°C and 150 rpm for 5 days to investigate the degradation effect of the four strains on methasulfuron.
[0072] The degradation rates of methasulfuron-methyl (SMTM) by four degrading bacteria are as follows: Figure 7 As shown, A, B, and C represent Bacillus megaterium, Escherichia coli, and Mycobacterium neoaurum, respectively. After 5 days, Bacillus megaterium achieved a degradation rate of 87.4% for methasulfuron-methyl; while the degradation rates of Escherichia coli and Mycobacterium neoaurum were both below 10%. The results indicate that Bacillus megaterium has a superior degradation effect compared to Escherichia coli and Mycobacterium neoaurum, therefore Bacillus megaterium was selected as the optimal degrading bacterium for methasulfuron-methyl.
[0073] Example 4
[0074] This embodiment uses the methamidosulfuron herbicide-contaminated water and soil remediation agent obtained in Example 1 to determine the removal performance of methamidosulfuron herbicide in soil, as detailed below:
[0075] Step 1: Soil was collected from farmland in Fengxian District, Shanghai (30°55'N, 121°42'E) where no methamidosulfuron herbicide had been applied. The soil was air-dried under natural conditions and ground through an 80-mesh sieve. 10 mg of solid methamidosulfuron was dissolved in 100 mL of acetonitrile to prepare a 100 mg / L methamidosulfuron solution. 1 mL of this solution was added to 10 g of air-dried soil and stirred thoroughly. After the acetonitrile evaporated, 190 g of uncontaminated soil was mixed with the solution to obtain 0.5 mg / kg methamidosulfuron-contaminated soil. 1% (w / w, %) of methamidosulfuron herbicide-contaminated water and soil remediation agent were added to this methamidosulfuron-contaminated soil, while ensuring that the soil moisture content remained at 60% of field capacity throughout the experimental period.
[0076] Step 2: Take samples on day 21, and then perform the operation in step 3 on the obtained soil samples.
[0077] Step 3: Weigh 5g of soil sample (air-dried and passed through an 80-mesh sieve) into a 50mL centrifuge tube, add 2mL of water, let stand for 5min, then add 20mL of extraction solution (acetic acid / acetonitrile = 1 / 99, v / v), 4g of anhydrous magnesium sulfate and 1g of sodium chloride, vortex for 1min to fully mix the soil sample and extraction solution, centrifuge for 10min (8000r / min), transfer 5mL of supernatant to a 10mL centrifuge tube, add 800mg of anhydrous magnesium sulfate and 200mg of purification agent C18, vortex and centrifuge for 10min (8000r / min), take 2mL of supernatant, filter through a 0.22μm filter membrane, and detect by liquid chromatography-mass spectrometry (LC-MS).
[0078] The results are as follows Figure 1 As shown, Figure 1The image shows the removal effect of the methamidosulfuron herbicide-contaminated soil remediation agent designed for this embodiment on methamidosulfuron in the soil. From... Figure 1 As can be seen, when the initial concentration of mefensulfuron in the contaminated soil was 0.5 mg / kg, the residual concentration of mefensulfuron in the water and soil after remediation with the herbicide was 0.13 mg / kg, with a degradation rate of 74%.
[0079] Example 5
[0080] This embodiment uses the methamidosulfuron herbicide-contaminated water and soil remediation agent obtained in Example 1 to determine the removal performance of methamidosulfuron herbicide in soil, as detailed below:
[0081] Step 1: Soil was collected from farmland in Fengxian District, Shanghai (30°55'N, 121°42'E) where no methamidosulfuron herbicide had been applied. The soil was air-dried under natural conditions and ground through an 80-mesh sieve. 10 mg of solid methamidosulfuron was dissolved in 100 mL of acetonitrile to prepare a 100 mg / L methamidosulfuron solution. This 10 mL solution was added to 10 g of air-dried soil and stirred thoroughly. After the acetonitrile evaporated, 190 g of uncontaminated soil was mixed with the solution to obtain 5 mg / kg methamidosulfuron-contaminated soil. 1% (w / w, %) of methamidosulfuron herbicide-contaminated water and soil remediation agent were added to this methamidosulfuron-contaminated soil, while ensuring that the soil moisture content remained at 60% of field capacity throughout the experimental period.
[0082] Step 2: Take samples on day 21, and then perform the operation in step 3 on the obtained soil samples.
[0083] Step 3: Weigh 5g of soil sample (air-dried and passed through an 80-mesh sieve) into a 50mL centrifuge tube, add 2mL of water, let stand for 5min, then add 20mL of extraction solution (acetic acid / acetonitrile = 1 / 99, v / v), 4g of anhydrous magnesium sulfate and 1g of sodium chloride, vortex for 1min to fully mix the soil sample and extraction solution, centrifuge for 10min (8000r / min), transfer 5mL of supernatant to a 10mL centrifuge tube, add 800mg of anhydrous magnesium sulfate and 200mg of purification agent C18, vortex and centrifuge for 10min (8000r / min), take 2mL of supernatant, filter through a 0.22μm filter membrane, and detect by liquid chromatography-mass spectrometry (LC-MS).
[0084] The results are as follows Figure 1 As shown, Figure 1 The image shows the removal effect of the methamidosulfuron herbicide-contaminated soil remediation agent designed for this embodiment on methamidosulfuron in the soil. From... Figure 1As can be seen, when the initial concentration of mefensulfuron in the contaminated soil was 5 mg / kg, the residual concentration of mefensulfuron in the water and soil after remediation with the herbicide was 0.48 mg / kg, and the degradation rate was 90.4%.
[0085] Example 6
[0086] This embodiment uses the methamidosulfuron herbicide-contaminated water and soil remediation agent obtained in Example 1 to determine the removal performance of methamidosulfuron herbicide in soil, as detailed below:
[0087] Step 1: Soil was collected from farmland in Fengxian District, Shanghai (30°55'N, 121°42'E) where no methamidosulfuron herbicide had been applied. The soil was air-dried under natural conditions and ground through an 80-mesh sieve. 10 mg of solid methamidosulfuron was dissolved in 100 mL of acetonitrile to prepare a 100 mg / L methamidosulfuron solution. 40 mL of this solution was added to 10 g of air-dried soil and stirred thoroughly. After the acetonitrile evaporated, 190 g of uncontaminated soil was mixed with the solution to obtain 20 mg / kg methamidosulfuron-contaminated soil. 1% (w / w, %) of methamidosulfuron herbicide-contaminated water and soil remediation agent were added to this methamidosulfuron-contaminated soil, while ensuring that the soil moisture content remained at 60% of field capacity throughout the experimental period.
[0088] Step 2: Take samples on day 21, and then perform the operation in step 3 on the obtained soil samples.
[0089] Step 3: Weigh 5g of soil sample (air-dried and passed through an 80-mesh sieve) into a 50mL centrifuge tube, add 2mL of water, let stand for 5min, then add 20mL of extraction solution (acetic acid / acetonitrile = 1 / 99, v / v), 4g of anhydrous magnesium sulfate and 1g of sodium chloride, vortex for 1min to fully mix the soil sample and extraction solution, centrifuge for 10min (8000r / min), transfer 5mL of supernatant to a 10mL centrifuge tube, add 800mg of anhydrous magnesium sulfate and 200mg of purification agent C18, vortex and centrifuge for 10min (8000r / min), take 2mL of supernatant, filter through a 0.22μm filter membrane, and detect by liquid chromatography-mass spectrometry (LC-MS).
[0090] The results are as follows Figure 1 As shown, Figure 1 The image shows the removal effect of the methamidosulfuron herbicide-contaminated soil remediation agent designed for this embodiment on methamidosulfuron in the soil. From... Figure 1 As can be seen, when the initial concentration of mefensulfuron in the contaminated soil was 20 mg / kg, the residual concentration of mefensulfuron in the water and soil after remediation with the herbicide was 0.58 mg / kg, and the degradation rate was 97.1%.
[0091] Example 7
[0092] This embodiment uses the methamidosulfuron herbicide-contaminated water and soil remediation agent obtained in Example 1 to determine the removal performance of methamidosulfuron herbicide in soil, as detailed below:
[0093] Step 1: Soil was collected from farmland in Fengxian District, Shanghai (30°55'N, 121°42'E) where no methamidosulfuron herbicide had been applied. The soil was air-dried under natural conditions and ground through an 80-mesh sieve. 10 mg of solid methamidosulfuron was dissolved in 100 mL of acetonitrile to prepare a 100 mg / L methamidosulfuron solution. This 10 mL solution was added to 10 g of air-dried soil and stirred thoroughly. After the acetonitrile evaporated, 190 g of uncontaminated soil was mixed with the solution to obtain 5 mg / kg methamidosulfuron-contaminated soil. 1% (w / w, %) of methamidosulfuron herbicide-contaminated water and soil remediation agent were added to this methamidosulfuron-contaminated soil, while ensuring that the soil moisture content remained at 60% of field capacity throughout the experimental period.
[0094] Step 2: Take samples on days 1, 3, 5, 7, 14 and 21 respectively, and then perform the operation in step 3 on the obtained soil samples.
[0095] Step 3: Weigh 5g of soil sample (air-dried and passed through an 80-mesh sieve) into a 50mL centrifuge tube, add 2mL of water, let stand for 5min, then add 20mL of extraction solution (acetic acid / acetonitrile = 1 / 99, v / v), 4g of anhydrous magnesium sulfate and 1g of sodium chloride, vortex for 1min to fully mix the soil sample and extraction solution, centrifuge for 10min (8000r / min), transfer 5mL of supernatant to a 10mL centrifuge tube, add 800mg of anhydrous magnesium sulfate and 200mg of purification agent C18, vortex and centrifuge for 10min (8000r / min), take 2mL of supernatant, filter through a 0.22μm filter membrane, and detect by liquid chromatography-mass spectrometry (LC-MS).
[0096] Results of a 21-day trial of methimazole-contaminated water and soil remediation agents for methimazole-contaminated soil: Figure 2As shown in the figure, at day 5, the residual concentrations of methasulfuron in the soils treated with Bacillus megaterium, nano-zero-valent iron modified biochar (Bacillus megaterium+BC), and methamidosulfuron herbicide-contaminated water and soil remediation agents (Bacillus megaterium+nZVI-BC) were 1.99 mg / kg, 1.23 mg / kg, and 0.61 mg / kg, respectively, with degradation rates of 60.2%, 75.4%, and 87.8%. At day 21, the residual concentrations of methasulfuron in the soils treated with Bacillus megaterium, nano-zero-valent iron modified biochar, and methamidosulfuron herbicide-contaminated water and soil remediation agents were 1.47 mg / kg, 0.48 mg / kg, and 0.47 mg / kg, respectively, with degradation rates of 70.6%, 90.4%, and 90.6%. The results showed that the methamidosulfuron herbicide-contaminated water and soil remediation agent could rapidly degrade methamidosulfuron in the soil within 5 days, with a better remediation effect than the group treated with only microorganisms. After 7-21 days following the addition of the methamidosulfuron herbicide-contaminated water and soil remediation agent, the residual levels of methamidosulfuron herbicide in the soil tended to stabilize.
[0097] Furthermore, the methimazole herbicide-contaminated water and soil remediation agent obtained in this invention can theoretically be used not only for the remediation of methimazole-contaminated water and soil, but also for the remediation of water and soil contaminated by pyrimisulfuron, nicosulfuron, chlorpyrifos, etc.
[0098] In summary, this invention increases the specific surface area of corn stalk biochar by loading nano-zero-valent iron onto its surface, while simultaneously improving the dispersibility and retaining the activity of the nano-zero-valent iron. This addresses the problems of easy saturation, easy desorption, and inability to completely degrade organic matter found in traditional biochar. The methamidosulfuron-methyl herbicide-contaminated water and soil remediation agent of this invention has a larger specific surface area, high adsorption efficiency, and high reactivity, enabling rapid, efficient, and green remediation of methamidosulfuron-methyl-contaminated water and soil.
[0099] The embodiments described above are merely preferred embodiments of the present invention and are not intended to limit the invention. Those skilled in the art can make various changes and modifications without departing from the spirit and scope of the invention. Therefore, all technical solutions obtained through equivalent substitution or transformation fall within the protection scope of the present invention.
Claims
1. A method for preparing a remediation agent for water and soil contaminated by mefensulfuron-methyl herbicide, characterized in that, Specifically as follows: Corn stalk powder was added to an aqueous solution containing ferric chloride hexahydrate, stirred and separated, and the solidified material was dried to obtain a composite material precursor. The composite material precursor was then subjected to a carbothermal reduction method, in which hydrogen or carbon monoxide generated by pyrolysis under high temperature and oxygen-deficient conditions was used to reduce ferric iron, so that the generated nano-zero ferric iron was loaded on the surface of biochar to obtain nano-zero ferric iron modified biochar. The fermentation broth of the degrading bacteria was fixed onto the nano-zero-valent iron modified biochar by physical adsorption, and then freeze-dried to obtain a remediation agent for water and soil polluted by mefensulfuron-methyl herbicide. The carbothermal reduction method is as follows: the composite material precursor is pyrolyzed at 700°C for 2 hours in an inert gas atmosphere, and then cooled to room temperature to obtain nano-zero-valent iron modified biochar. The fermentation broth of the degrading bacteria is Bacillus megaterium.
2. The preparation method of the methimazole herbicide-contaminated water and soil remediation agent according to claim 1, characterized in that, The preparation process of the composite material precursor is as follows: Corn stalk powder was washed with water and dried, then added to an aqueous solution containing ferric chloride hexahydrate and stirred thoroughly to obtain a suspension containing a solidified product. The suspension was left to stand at room temperature for 24 hours, and then centrifuged to obtain the lower solidified product. The solidified product was dried at 80°C to obtain the composite material precursor.
3. The preparation method of the methimazole herbicide-contaminated water and soil remediation agent according to claim 1, characterized in that, In the composite material precursor, the mass ratio of corn stalk powder to ferric chloride hexahydrate is 1:2.
7.
4. The preparation method of the herbicide-based water and soil remediation agent according to claim 1, characterized in that, The inert gas used is nitrogen, with a flow rate of 80 mL / min; the heating rate during pyrolysis is 5℃ / min, and the cooling rate during cooling is 10℃ / min.
5. The preparation method of the methimazole herbicide-contaminated water and soil remediation agent according to claim 1, characterized in that, The nano-zero-valent iron modified biochar has a particle size of 0.25-0.5 mm, the immobilization time of the degrading bacteria fermentation broth is 26 hours, and the mass-to-volume ratio of nano-zero-valent iron modified biochar to degrading bacteria fermentation broth is 6%.
6. The preparation method of the herbicide-based water and soil remediation agent according to claim 1, characterized in that, The physical adsorption method refers to immersing nano-zero-valent iron modified biochar in the fermentation broth of degrading bacteria and fixing it by shaking at 30°C and 150 rpm.
7. A herbicide remediation agent for polluted water and soil obtained by any of the preparation methods described in claims 1 to 6.
8. An application of the methimazole herbicide-contaminated water and soil remediation agent according to claim 7 in the remediation of water and soil contaminated by methimazole herbicide.