A biochar material, and a method of making and using the same

Abstract

The present application relates to the field of biochar materials, in particular to a biochar material, a preparation method and application thereof. The present application provides a preparation method of a biochar material, characterized in that the method comprises the following steps: S101 obtaining a first mixed solution; S102 obtaining a first precursor; S103 obtaining a second precursor; S104 obtaining a first material; and S105 obtaining the biochar material. The biochar material prepared by the present application can be used for directional adsorption of pigments (such as lutein and chlorophyll), and is suitable for application to QuEChERS method pretreatment.

Description

[0001] This application claims priority to Chinese invention patent application [CN2024117328411], filed on November 28, 2024, entitled "A biochar material and its preparation method and application", which is incorporated herein by reference in its entirety. Technical Field

[0002] This invention relates to the field of biochar materials, specifically to a biochar material, its preparation method, and its application. Background Technology

[0003] With the expansion of medicinal crop planting areas and the extension of planting years, the occurrence of diseases, pests, and weeds affecting medicinal crops is becoming increasingly serious. Currently, the control of diseases, pests, and weeds in medicinal crop production in my country mainly relies on chemical pesticides. However, the unreasonable use of pesticides may lead to potential hazards from pesticide residues. Therefore, it is necessary to monitor pesticide residues in medicinal crops to safeguard food safety.

[0004] Chrysanthemum is a multifunctional medicinal crop with pharmacological effects encompassing heat-clearing and detoxifying, liver-soothing and vision-improving, antibacterial and anti-inflammatory, lipid-lowering, antioxidant, vasodilator, blood pressure-lowering, and anti-tumor properties. In recent years, with the in-depth exploration of the rich pharmacological effects of chrysanthemum, its planting area has shown a significant expansion trend. However, in the process of chrysanthemum cultivation, pest and disease problems have become increasingly prominent. In pursuit of high yields and to ensure the quality of chrysanthemums, growers have been forced to adopt pesticide control measures to protect chrysanthemums from pests and diseases. This practice simultaneously raises dual issues of food safety and ecological safety. Compared with other plants, chrysanthemums have a complex composition, containing not only a large amount of pigments but also a large amount of oils, flavonoids, and other components, which places higher demands on the detection methods of pesticide residues in chrysanthemums.

[0005] Honeysuckle is a traditional Chinese medicinal and edible plant with a wide distribution and significant ornamental, economic, edible, and medicinal value. However, honeysuckle is susceptible to pests and diseases during cultivation, leading many growers to use chemical pesticides for control. Therefore, honeysuckle is a key variety of concern due to its high pesticide residue levels. Currently, the biggest challenge in detecting trace pesticide residues in honeysuckle using mainstream detection methods is the presence of pigments. This is because honeysuckle undergoes color changes during its development due to endogenous pigment variations, and these pigments can significantly interfere with trace pesticide detection. Furthermore, the honeysuckle matrix is ​​characterized by its dark color and high content of xanthophyll and chlorophyll. Therefore, detecting pesticide residues in honeysuckle remains challenging.

[0006] Mulberry leaves are a commonly used bulk Chinese medicinal herb, considered both food and medicine. Modern pharmacological research shows that mulberry leaves possess various pharmacological effects, including anti-inflammatory, antioxidant, anti-tumor, hypoglycemic, lipid-regulating, liver-protective, and cardioprotective properties. Furthermore, as a primary food source for silkworms, the safety of mulberry leaves directly impacts their health, thus affecting silk production. In recent years, with the increasing variety and amount of pesticides used, mulberry leaves have become a key area of ​​concern due to the high levels of pesticide residues. However, current mainstream detection methods for trace pesticide residues in mulberry leaves face challenges due to the presence of abundant lutein, chlorophyll, flavonoids, and polysaccharides.

[0007] The pesticide residue analysis process includes two parts: sample pretreatment and instrumental analysis. The cumbersome sample pretreatment process severely limits analytical efficiency. The development of the QuEChERS method has simplified the sample pretreatment procedure, where the selection of the purifying agent is crucial, primarily affecting the purification effect of the matrix and the pesticide recovery rate. The specific surface area, porous structure, and tunable surface chemical properties of carbon materials are gradually emerging in improving the QuEChERS method. Carbon nanotubes, carbon dots, graphene / graphene oxide, fullerenes, and their derivatives have all achieved good results. However, the raw materials for these carbon materials are mostly derived from petroleum-based materials, which is not only environmentally unfriendly but also consumes a huge amount of non-renewable resources like petroleum.

[0008] Biochar materials are derived from biomass as a carbon source. They not only have a wide availability but also possess a certain adsorption capacity, thus serving as adsorbents to remove pesticide residues. However, for pesticide residue analysis, existing technologies typically modify biochar materials with metal ions (e.g., ZnCl2) or metal oxides (e.g., Fe3O4) to apply the modified biochar materials to the sample pretreatment stage. Chinese patent application CN117191536A discloses the application of magnetic biochar materials as a purification agent in the QuEChERS pretreatment method. In this application, the magnetic biochar material is Fe3O4-modified biochar. It explicitly states that directly using biochar in the sample pretreatment process presents a problem of difficulty in separation; therefore, Fe3O4 needs to be assembled onto the biochar material before it can be used for pesticide residue analysis. Summary of the Invention

[0009] In a first aspect, the present invention provides a method for preparing biochar material, characterized by comprising the following steps:

[0010] S101 adds biomass material to the first solution for pretreatment to obtain the first mixture;

[0011] In some embodiments, the biomass material includes straw, sawdust, or loofah sponge.

[0012] In some embodiments, the straw is corn straw.

[0013] In some embodiments, the wood chips are balsa wood chips.

[0014] In some embodiments, the biomass material comprises 40-60 mesh.

[0015] In some embodiments, the first solution comprises a hydrogen peroxide solution or a hypochlorite solution.

[0016] In some embodiments, when the first solution is a hypochlorite solution, the pretreatment method includes: immersing the biomass material in the hypochlorite solution for a first time period to obtain a first mixture.

[0017] In some embodiments, the first time period includes 4-6 hours.

[0018] In some embodiments, the effective chlorine content of the hypochlorite solution includes 2%-5% by mass.

[0019] In some embodiments, when the first solution is a hydrogen peroxide solution, the pretreatment method includes: adding the biomass material to the hydrogen peroxide solution and heating for a third time period to obtain a first mixture.

[0020] In some embodiments, the third time period includes 2-4 hours.

[0021] In some embodiments, the concentration of the hydrogen peroxide solution includes 2-5 mol / L.

[0022] In some embodiments, the ratio of the biomass material to the first solution includes 1.0 g: 40-60 mL.

[0023] S102 The biomass material in the first mixture is placed in water and subjected to a hydrothermal reaction to obtain the first precursor;

[0024] In some embodiments, the temperature of the hydrothermal reaction includes 200-240°C.

[0025] In some embodiments, the hydrothermal reaction time includes 4-6 hours.

[0026] S103 Vacuum dry the first precursor to obtain the second precursor;

[0027] S104 carbonizes the second precursor to obtain the first material;

[0028] In some embodiments, the carbonization setting temperature includes 500-900°C.

[0029] In some embodiments, the carbonization setting temperature includes 600-800°C.

[0030] In some embodiments, the carbonization temperature is set at 500, 600, 700, 800, or 900°C.

[0031] In some embodiments, the heating rate of the carbonization includes 5-10 °C / min.

[0032] S105 The first material is immersed in the second solution for a second time period, and then vacuum dried to obtain the biochar material.

[0033] In some embodiments, the second solution comprises one or more of sulfuric acid, hydrochloric acid, and nitric acid.

[0034] In some embodiments, the second solution comprises hydrochloric acid, nitric acid, or a combination thereof.

[0035] In some embodiments, the concentration of the second solution includes 0.5-1M.

[0036] In some embodiments, the concentration of the hydrochloric acid includes 0.5-1M.

[0037] In some embodiments, the concentration of the nitric acid includes 0.5-1M.

[0038] In some embodiments, the second time period includes at least 8 hours.

[0039] Secondly, the present invention provides biochar materials prepared by the above-described preparation method.

[0040] Thirdly, the present invention provides the application of the above-mentioned biochar material in the preparation of pesticide residue pretreatment reagents.

[0041] In some embodiments, the pesticide residue pretreatment reagent is used for the targeted adsorption of pigments in the sample.

[0042] In this invention, "directional adsorption" refers to the selective adsorption of pigments (e.g., chlorophyll and / or xanthophyll) contained in the sample in the presence of a sample matrix, while hardly adsorbing trace amounts of pesticides.

[0043] In some embodiments, the pigments include chlorophyll and / or xanthophyll.

[0044] In some embodiments, the pesticide residue pretreatment reagent is used for medicinal crop samples.

[0045] In some embodiments, the pesticide residue pretreatment reagent is used for samples of Chinese medicinal materials.

[0046] In some embodiments, the pesticide residue pretreatment reagent is used for chrysanthemum samples, honeysuckle samples, or mulberry leaf samples.

[0047] In some embodiments, the biochar material is used in combination with an adsorbent material.

[0048] In some embodiments, the pesticide residue pretreatment reagent further includes an adsorbent material.

[0049] In some embodiments, the adsorbent material comprises ethylenediamine-N-propylsilane (PSA).

[0050] In some embodiments, the mass ratio of the biochar material to the adsorbent material includes (5-8):1.

[0051] In some embodiments, the pesticide residue pretreatment reagent includes the biochar material and ethylenediamine-N-propylsilane.

[0052] In some embodiments, the mass ratio of the biochar material and the ethylenediamine-N-propylsilane in the pesticide residue pretreatment reagent is (5-8):1.

[0053] In some embodiments, the mass ratio of the biochar material to the ethylenediamine-N-propylsilane is (6-8):1.

[0054] Fourthly, the present invention also provides a sample pretreatment kit based on QuEChERS, characterized in that the sample pretreatment kit includes a pesticide residue pretreatment reagent, wherein the pesticide residue pretreatment reagent includes the above-mentioned biochar material.

[0055] In some embodiments, the pesticide residue pretreatment reagent is configured for pretreatment purification of a medicinal crop sample.

[0056] In some embodiments, the medicinal crop sample includes chrysanthemum sample, honeysuckle sample, or mulberry leaf sample.

[0057] In some embodiments, the pesticide residue pretreatment reagent further includes an adsorbent material.

[0058] In some embodiments, the adsorbent material comprises ethylenediamine-N-propylsilane, and the mass ratio of the biochar material to the adsorbent material comprises (5-8):1.

[0059] In some embodiments, the mass of one sample of medicinal crop includes 2-3g.

[0060] In some embodiments, the mass of one medicinal crop sample is 2.5g.

[0061] In some embodiments, the mass ratio of the pesticide residue pretreatment reagent to the medicinal crop sample includes 1:(5-20).

[0062] In some embodiments, the mass ratio of the pesticide residue pretreatment reagent to the medicinal crop sample includes 1:(8-15).

[0063] In some embodiments, the mass ratio of the pesticide residue pretreatment reagent to the medicinal crop sample is 1:(9-12).

[0064] In some embodiments, when the mass of one medicinal crop sample is 2.5g, the pesticide residue pretreatment reagent may include 125-500mg, 150-225mg, or 180-240mg of biochar material.

[0065] In some embodiments, when the mass of one medicinal crop sample is 2.0g, the pesticide residue pretreatment reagent may include 100-400mg, 120-150mg, or 140-195mg of biochar material.

[0066] In some embodiments, when the mass of the chrysanthemum sample is 2.5g, the pesticide residue pretreatment reagent may include 180-240mg of biochar material.

[0067] In some embodiments, the pesticide residue pretreatment reagent may further include 30 mg of ethylenediamine-N-propylsilane.

[0068] In some embodiments, the sample pretreatment kit further comprises an anhydrous polar reagent, which includes one or more of ethyl acetate, acetonitrile, and methanol.

[0069] In some embodiments, the anhydrous polar reagent is anhydrous acetonitrile.

[0070] Fifthly, the present invention also provides a method for detecting multiple trace pesticide residues in medicinal crop samples using HPLC-MS / MS, the method being based on the above-mentioned sample pretreatment kit and comprising the following steps:

[0071] S201 Add the anhydrous polar solvent to the medicinal crop sample for extraction to obtain a medicinal crop extract;

[0072] In some embodiments, the medicinal crop sample is in powder form.

[0073] S202 The medicinal crop extract (preferably 1 / 3 of the medicinal crop extract obtained in S201) is added to the pesticide residue pretreatment reagent for shaking extraction. Then, the supernatant is filtered and injected into an HPLC-MS / MS instrument for trace pesticide residue detection.

[0074] In some embodiments, the medicinal crop sample includes chrysanthemum sample, honeysuckle sample, or mulberry leaf sample.

[0075] In some embodiments, the mass of the medicinal crop sample includes 2-3g.

[0076] In some embodiments, the mass of the medicinal crop sample is 2.5g.

[0077] In some embodiments, the mass ratio of the pesticide residue pretreatment reagent to the medicinal crop sample includes 1:(5-20).

[0078] In some embodiments, the mass ratio of the pesticide residue pretreatment reagent to the medicinal crop sample includes 1:(8-15).

[0079] In some embodiments, the mass ratio of the pesticide residue pretreatment reagent to the medicinal crop sample is 1:(9-12).

[0080] In some embodiments, when the mass of one medicinal crop sample is 2.5g, the pesticide residue pretreatment reagent may include 125-500mg, 150-225mg, or 180-240mg of biochar material.

[0081] In some embodiments, when the mass of one medicinal crop sample is 2.0g, the pesticide residue pretreatment reagent may include 100-400mg, 120-150mg, or 140-195mg of biochar material.

[0082] In some embodiments, when the mass of the chrysanthemum sample is 2.5g, the pesticide residue pretreatment reagent may include 180-240mg of biochar material.

[0083] S203 was separated from the supernatant of S202 by high performance liquid chromatography (HPLC). The HPLC method used a C18 column at a column temperature of 40°C and gradient elution was performed with 0.1% formic acid acetonitrile solution as mobile phase A and 0.1% formic acid water as mobile phase B.

[0084] S204 uses tandem mass spectrometry to analyze the substances separated by high performance liquid chromatography described in S203, using ESI as the ion source and employing multiple reaction monitoring mode.

[0085] In some embodiments, the gradient elution conditions are:

[0086] 0min: A% - B%: 30-70;

[0087] 12min: A% - B%: 70 - 0;

[0088] 14min: A% - B%: 70 - 0;

[0089] 14.01min: A%-B%: 30-70.

[0090] In some embodiments, the nebulizing gas flow rate of the tandem mass spectrometry is 3.0 L / min; the drying gas flow rate is 10 L / min; and the heating gas flow rate is 10 L / min.

[0091] In some embodiments, the interface temperature of the tandem mass spectrometry instrument is 300°C; the DL temperature is 150°C; and the heating block temperature is 400°C.

[0092] Sixthly, the present invention also provides the application of the above-mentioned biochar material in the preparation of a QuEChERS-based sample pretreatment kit, characterized in that the sample pretreatment kit includes a pesticide residue pretreatment reagent, and the pesticide residue pretreatment reagent includes the biochar material.

[0093] In some embodiments, the pesticide residue pretreatment reagent is configured for pretreatment purification of a medicinal crop sample.

[0094] In some embodiments, the medicinal crop sample includes chrysanthemum sample, honeysuckle sample, or mulberry leaf sample.

[0095] In some embodiments, the pesticide residue pretreatment reagent further includes an adsorbent material.

[0096] In some embodiments, the adsorbent material comprises ethylenediamine-N-propylsilane, and the mass ratio of the biochar material to the adsorbent material comprises (5-8):1.

[0097] In some embodiments, the mass of one sample of medicinal crop includes 2-3g.

[0098] In some embodiments, the mass of one medicinal crop sample is 2.5g.

[0099] In some embodiments, the mass ratio of the pesticide residue pretreatment reagent to the medicinal crop sample includes 1:(5-20).

[0100] In some embodiments, the mass ratio of the pesticide residue pretreatment reagent to the medicinal crop sample includes 1:(8-15).

[0101] In some embodiments, the mass ratio of the pesticide residue pretreatment reagent to the medicinal crop sample is 1:(9-12).

[0102] In some embodiments, when the mass of one medicinal crop sample is 2.5g, the pesticide residue pretreatment reagent may include 125-500mg, 150-225mg, or 180-240mg of biochar material.

[0103] In some embodiments, when the mass of one medicinal crop sample is 2.0g, the pesticide residue pretreatment reagent may include 100-400mg, 120-150mg, or 140-195mg of biochar material.

[0104] In some embodiments, when the mass of the chrysanthemum sample is 2.5g, the pesticide residue pretreatment reagent may include 180-240mg of biochar material.

[0105] In some embodiments, the pesticide residue pretreatment reagent may further include 30 mg of ethylenediamine-N-propylsilane.

[0106] In some embodiments, the sample pretreatment kit further comprises an anhydrous polar reagent, which includes one or more of ethyl acetate, acetonitrile, and methanol.

[0107] In some embodiments, the anhydrous polar reagent is anhydrous acetonitrile.

[0108] Compared with the prior art, the beneficial effects of the present invention include at least the following aspects:

[0109] To enable biochar materials to be used in pesticide residue analysis, existing techniques typically modify them with metal ions (e.g., ZnCl2) or metal oxides (e.g., Fe3O4). Furthermore, existing techniques suggest that biochar materials not modified with metal ions or magnetically are difficult to use in pesticide residue analysis, particularly as a purifying agent in the QuEChERS pretreatment method.

[0110] The method for preparing biochar materials provided by this invention creatively combines hypochlorite / hydrogen peroxide treatment, hydrothermal treatment, and pyrolysis. It has been found that these three steps synergistically ensure the directional adsorption of pigments (such as lutein and chlorophyll) by the biochar materials prepared by this invention (i.e., no retention effect on various pesticides, but retention effect on pigments), and are suitable for application in the pretreatment of the QuEChERS method.

[0111] Specifically, this invention utilizes hypochlorite (e.g., sodium hypochlorite) / hydrogen peroxide to treat straw powder, thereby oxidizing and degrading lignin in biomass materials (e.g., straw powder). However, this invention has found that hypochlorite / hydrogen peroxide, as broad-spectrum oxidants, while oxidizing and degrading lignin, also degrades some cellulose in the biomass material, thereby destroying the pore structure of the biomass material. This leads to further damage to the pore structure of the biomass material during subsequent hydrothermal treatment and pyrolysis, ultimately preventing the formation of biochar material. While sodium hydroxide + sodium hypochlorite can promote the dissolution of lignin, it cannot improve the directional adsorption performance of pigments in biochar material. This invention, by controlling the pretreatment method of biomass material (e.g., soaking time and ratio in hypochlorite / hydrogen peroxide solution), effectively reduces the binding force between lignin, cellulose, and hemicellulose in the biomass material and breaks down the natural anti-degradation barrier of lignin, while maintaining the integrity of the original cellulose structure. This endows the cellulose surface with more oxygen-containing functional groups, providing a structural basis for subsequent hydrothermal treatment and pyrolysis (i.e., ensuring the stability of the biochar pore structure).

[0112] Furthermore, this invention involves sequentially hydrothermal treatment and pyrolysis of pretreated biomass materials (e.g., straw powder treated with hypochlorite) and biochar. Since the pore structure of the pretreated biomass material has already been altered to some extent, hydrothermal treatment and pyrolysis still negatively impact the stability of the biochar's pore structure. To address this, this invention, by coordinating factors such as the temperature of the hydrothermal treatment and pyrolysis, endows the cellulose surface of the pretreated biomass material with more oxygen-containing functional groups. This ensures that the stability of the biochar's pore structure is not affected while further expanding the porosity of the cellulose surface and increasing the specific surface area of ​​the biochar material. Furthermore, this invention has found that, compared to sulfuric acid treatment, appropriate concentrations of hydrochloric acid and / or nitric acid treatment can produce a better synergistic effect with hypochlorite / hydrogen peroxide treatment, hydrothermal treatment, and pyrolysis, forming mesoporous materials and further improving the purification effect and adsorption efficiency of pigments in complex matrices of various medicinal crop samples (especially honeysuckle and mulberry leaf samples).

[0113] Compared with traditional adsorbent material production processes, the method provided by this invention is highly cost-effective, with costs significantly lower than petroleum or asphalt-based materials. It also saves a considerable amount of energy and is environmentally friendly. Furthermore, the method provided by this invention offers high yield, produces high-quality biochar materials, generates virtually no byproducts such as tar and ash, and has low preparation difficulty and risk, making it a promising candidate for industrial applications.

[0114] Furthermore, it is important to emphasize that the biochar material prepared in this invention, without undergoing metal ion activation modification and / or magnetic modification, unexpectedly functions as a directional adsorbent in the analysis of pesticide residues in complex matrices of various medicinal crop samples pretreated using the QuEChERS method. This achieves effective purification of pigments, fats, and flavonoids in the medicinal crop extracts, whereas biochar materials obtained solely through hydrothermal treatment or pyrolysis are unlikely to achieve the same purification effect on pigments and fats in complex matrices. Based on the biochar material prepared in this invention, the detection limits for pesticides using HPLC-MS / MS to detect multiple trace pesticide residues in honeysuckle are 0.00001-0.00016 mg·kg⁻¹. -1 The limit of quantitation is 0.00002-0.00047 mg / kg. -1 The detection limits for the method of detecting multiple trace pesticide residues in mulberry leaves are 0.00001–0.0015 mg·kg⁻¹. -1 The limit of quantitation is 0.00002–0.0004 mg / kg. -1 In addition, considering the spiked recoveries of several pesticides that are significantly affected by the matrix and purification materials (such as amphetamine, mesosulfuron, chlorsulfuron, and amitraz), commercial adsorbent materials (such as GCB and PSA) exhibit adsorption effects on these pesticides. However, the biochar material prepared in this invention does not show specific adsorption effects on these pesticides, making it more suitable as a pesticide residue pretreatment reagent based on the QuECHERS method.

[0115] The biochar material prepared by this invention can effectively replace commercial adsorbents (such as GCB). Compared to commercial adsorbents, the biochar material prepared by this invention has a lower preparation cost (approximately US$0.5 per gram of biochar) and is more eco-friendly. Attached Figure Description

[0116] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. The elements or parts in the drawings are not necessarily drawn to scale. Obviously, the drawings described below are some embodiments of the present invention, and those skilled in the art can obtain other drawings based on these drawings without any creative effort.

[0117] Figure 1 The graph shows the results of pigment content in the matrix before and after purification by the biochar material of the present invention.

[0118] Figure 2The graph shows the effect of different amounts of biochar material on the spiked recovery rates of 31 pesticides.

[0119] Figure 3 A graph showing the comparison between the purification effects of biochar compound materials and commercially available materials;

[0120] Figure 4 A comparison chart showing the purification effects of different materials;

[0121] Figure 5 A comparative graph showing the matrix effects of 31 pesticides in chrysanthemum extract purified by optimized purification materials.

[0122] Figure 6 SEM images showing the morphological changes of biochar materials before and after adsorption;

[0123] Figure 7 The adsorption isotherm of biochar material;

[0124] Figure 8 The image shows a comparison of the purification effects of optimized biochar materials on honeysuckle extract (top) and mulberry leaf extract (bottom).

[0125] Figure 9 The infrared spectrum of biochar material after nitric acid functionalization is shown.

[0126] Figure 10 The adsorption isotherm of biochar material after nitric acid functionalization. Detailed Implementation

[0127] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.

[0128] In this document, "and / or" includes any and all combinations of one or more of the listed related items.

[0129] In this article, "multiple" means two or more, that is, it includes two, three, four, five, etc.

[0130] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes that element.

[0131] As used in this specification, the term "about" typically means + / -5% of the value, more typically + / -4%, more typically + / -3%, more typically + / -2%, even more typically + / -1%, and even more typically + / -0.5%.

[0132] In this specification, certain embodiments may be disclosed in a range-bound format. It should be understood that this "range-bound" description is merely for convenience and brevity and should not be construed as a rigid limitation on the disclosed range. Therefore, the description of a range should be considered as having specifically disclosed all possible subranges and the individual numerical values ​​within those ranges. For example, a description of the range 1-6 should be considered as having specifically disclosed subranges such as from 1 to 3, from 1 to 4, from 1 to 5, from 2 to 4, from 2 to 6, from 3 to 6, etc., and the individual numbers within those ranges, such as 1, 2, 3, 4, 5, and 6. This rule applies regardless of the breadth of the range.

[0133] Detailed description of the attached figures

[0134] Figure 1 A shows a comparison between unpurified chrysanthemum extract and extracts purified with 180 / 240 mg biochar material. From left to right: unpurified, purified with 180 mg biochar material, purified with 180 mg biochar material, purified with 240 mg biochar material, and purified with 240 mg biochar material. B shows chrysanthemum extracts purified with 30, 60, 90, and 120 mg biochar material (from left to right). C shows the quantitative results comparing the chlorophyll and xanthophyll content in solutions purified with different amounts of biochar material.

[0135] Figure 2A represents the spiked recoveries of 15 pesticides (methamidophos, terbufos, phosmet, bensulfuron-methyl, metsulfuron-methyl, chlorsulfuron-methyl, thionylphos, chlorpyrifos, phosmet, phosphamidon, phosphamidon, phosmet, ethoprophos, ethoprophos, amitraz, methyl isofenphos, etc., hereinafter the same) in solutions purified with different amounts of biochar material. B represents the spiked recoveries of 4 pesticides (benzylphos, phorate, aldicarb, and terbufos, hereinafter the same) in solutions purified with different amounts of biochar material. C represents the spiked recoveries of 2 pesticides (carbofuran and demeton-methyl, hereinafter the same) in solutions purified with different amounts of biochar material. D represents the pass rates of spiked recoveries of different pesticides in solutions purified with different amounts of biochar material.

[0136] Figure 3 A represents the spiked recoveries of 15 pesticides in solutions purified with different biochar compound materials. B represents the spiked recoveries of 4 pesticides in solutions purified with different biochar compound materials. C represents the spiked recoveries of 2 pesticides in solutions purified with different biochar compound materials. D represents the spiked recoveries of 15 pesticides in solutions purified with commercially available materials and biochar materials. E represents the spiked recoveries of 4 pesticides in solutions purified with commercially available materials and biochar materials. F represents the spiked recoveries of 2 pesticides in solutions purified with commercially available materials and different biochar compound materials.

[0137] Figure 4 From left to right: Unpurified; Purified with GCB-80mg; Purified with MWCNTS-180mg; Purified with PSA-180mg; Purified with C18-180mg; Purified with biochar material-180mg+C18-30mg; Purified with biochar material-180mg+PSA-30mg; Purified with biochar material-180mg+PSA-30mg+C18-30mg.

[0138] Figure 8 In the left image, from left to right, the groups are: unpurified, delignified + hydrothermal treatment + pyrolysis treatment, hydrothermal treatment + pyrolysis treatment, delignified + pyrolysis treatment, direct pyrolysis, and delignified + hydrothermal treatment. In the right image, from left to right, the groups are: unpurified, delignified + hydrothermal treatment + pyrolysis treatment, hydrothermal treatment + pyrolysis treatment, delignified + pyrolysis treatment, direct pyrolysis, and delignified + hydrothermal treatment.

[0139] Example 1: Materials and Methods

[0140] 1.1 Reagents and Instruments

[0141] Corn stalks were collected from Hebei Province, China. The 31 pesticide reference standards (see table below) were obtained from the Tanmo Quality Inspection Reference Material Center. NaOCl was from Tianjin Fuchen Chemical, H2SO4 from Beijing Reagent, NaCl from Sinopharm Group, and formic acid from Aladdin. Acetonitrile was from Merck. MWCNTs were from Suzhou Hengqiu Technology (Suzhou, China), GCB-N and C18 from Beijing Kedenos Technology Co., Ltd. (Beijing, China), PSA from Tianjin Bona Ager Technology Co., Ltd. (Tianjin, China), and Oasis HLB solid-phase extraction columns from Waters Technologies Co., Ltd.

[0142] serial number pesticide name serial number pesticide name 1 Tamiflu 17 terbufos 2 Chlorpyrifos 18 Methyl sulfone 3 Control of pyrophos 19 Systemic phosphorus-S 4 Long-lasting phosphorus 20 3-Hydroxycarbofuran 5 Ambutanol 21 Phosphorus 6 mesosulfuron 22 Benzene sulfone 7 Chlorsulfuron 23 tert-butyl sulfone 8 Insecticidal amitraz 24 tert-butyl sulfoxide 9 Thiocyclic phosphorus 25 Phosphorus 10 Phosphine 26 Methylphosphorus sulfoxide 11 Methyl isofenphos 27 Systemic phosphorus-O 12 Earthworm sulfur phosphorus 28 Thiamethoxam 13 Sulfur-lined phosphorus 29 Phosphamide 14 Methamidophos 30 Tttrium sulfone 15 Benzene Phosphorus 31 Carbofuran 16 Benzene sulfoxide

[0143] The LC-40A liquid chromatography-mass spectrometry system (LCMS-8045) was purchased from Shimadzu Corporation, Japan. The N5000 spectrophotometer was purchased from Shanghai Youke Instrument Co., Ltd. The universal high-speed pulverizer was purchased from Tianjin Test Instrument Co., Ltd. The high-power multi-tube vortex mixer was purchased from Beijing Kedenos Technology Co., Ltd. The tube furnace was purchased from Beijing Fuleimeng Experimental Equipment Co., Ltd. The JJ 500 electronic balance (0.01g) was purchased from Changshu Shuangjie Test Instrument Factory. The AL104-IC electronic balance (0.0001g) was purchased from Mettler Toledo. Eppendorf measuring range: 20–200 μL and 100–1000 μL. The MPE series high-throughput parallel evaporator was purchased from RayKol Group Corp., Ltd. (Xiamen, China). The samples were characterized using a specific surface area analyzer – BelSorp Max (MicrotracBEL, Japan) and a scanning electron microscope – Zeiss Ultra 55 (Shanghai, China).

[0144] 1.2 Preparation of biochar materials

[0145] To prepare biochar, corn stalks were first ground into powder and passed through a 40-mesh sieve. Then, the sieved corn stalk powder was soaked in NaOCl (with an effective chlorine content of approximately 5%) at a ratio of 1g corn stalk powder to 50mL NaOCl for 4 hours. The NaOCl residue on the surface of the stalks was washed away with deionized water until no noticeable chlorine odor was detected.

[0146] The cleaned corn stalk powder and an appropriate amount of deionized water were placed in a reaction vessel and treated in an oven at 220°C for 4 hours to prepare the precursor. After heating, the reaction vessel was allowed to cool completely. The corn stalk powder was then removed from the reaction vessel and washed with deionized water until the color of the aqueous solution no longer changed. The corn stalk powder was then placed in a vacuum drying oven and vacuum dried at 60°C to obtain the carbonized precursor.

[0147] The dried carbonization precursor was passed through a 40-mesh sieve and placed in a quartz boat. A tube furnace was set to 800°C with a heating rate of 5°C / min to carbonize the corn stalk powder. The entire carbonization process was carried out under a nitrogen atmosphere. After carbonization, the biochar was soaked in 0.5M sulfuric acid overnight, washed with water until the aqueous solution was neutral, and then vacuum dried to obtain the biochar material of this invention.

[0148] 1.3 Pretreatment of Chrysanthemums

[0149] For the pretreatment of chrysanthemum, firstly, pulverize the chrysanthemum and pass it through a 40-mesh sieve, then set aside. Take 2.5g of the sieved chrysanthemum powder into a 50mL centrifuge tube, add 1g of sodium chloride and one ceramic homogenizer suitable for a 50mL centrifuge tube, and add 25mL of acetonitrile. Vortex for 5min at 3000r / min using a high-power multi-tube vortex mixer. Centrifuge and collect the supernatant. Add another 25mL of acetonitrile to the centrifuge tube, repeat the vortexing and centrifugation, and collect the supernatant. Repeat this process 3 times, combine the supernatants, and concentrate them using a parallel concentrator. After concentration, add 5mL of acetonitrile to the tube to reconstitute and obtain the chrysanthemum extract.

[0150] 1.4 Purification of Chrysanthemum Extract

[0151] Take 3 mL of chrysanthemum extract into a centrifuge tube containing biochar material, vortex at 3000 r / min for 5 min and centrifuge at 13000 r / min for 8 min to obtain the supernatant, which is the purified chrysanthemum solution.

[0152] 1.5 Determination of lutein, chlorophyll and fat content in solution

[0153] Chlorophyll content was determined according to the standard "Determination of Chlorophyll Content in Fruits, Vegetables and Their Products - Spectrophotometric Method" (NY / T1783082-2017). Lutein content was determined according to the standard "National Food Safety Standard - Determination of Lutein in Food" (GB 5009.248-2016). Fat content was determined according to the standard "National Food Safety Standard - Determination of Fat in Food" (GB 5009.6-2016).

[0154] 1.6 HPLC-MS / MS conditions

[0155] Pesticides were detected using an LCMS-8045 liquid chromatography-mass spectrometry (LCMS) system. The chromatographic column was a Shim-pack GIST-HP C18 (2.1 × 100 mm, 3 μm) (Shimadzu Corporation, Kyoto). The column temperature was 40 °C, and the injection volume was 5 μL. The mobile phase consisted of 0.1% formic acid-acetonitrile solution (A) and 0.1% formic acid aqueous solution (B), with a flow rate of 0.3 mL / min. The chromatographic conditions were: 30-70% A for 2 min from 0 to 12 min; 70-30% A for 14-14.01 min, held until 17 min. Pesticide analysis was performed using ESI positive ion mode and multiple reaction monitoring (MRM). The nebulizer gas flow rate was 3.0 L / min, the drying gas flow rate was 10 L / min, the heating gas flow rate was 10 L / min, the interface temperature was 300 °C, the DL temperature was 150 °C, and the heating block temperature was 400 °C.

[0156] 1.7 Methodological Examination

[0157] According to document SANTE / 11312 / 2021v2 (SANTE, 2021), the feasibility of the developed method was validated using the following parameters: linearity, matrix effect, accuracy, precision, limit of detection (LOD), and limit of quantitation (LOQ). The instrument was calibrated daily during the experiments. The linearity of the method was validated by adding a mixed standard solution of 31 pesticides at seven levels (1, 5, 10, 50, 100, 200, 300, and 500 μg / L) to a chrysanthemum blank matrix solution. The matrix effect of the method was evaluated by comparing the slope ratios of the solvent-based and matrix-matched calibration curves for all target pesticides. The accuracy and precision of the method were validated by testing the spiked recoveries (n=6) and reproducibility of the 31 pesticides at three levels (0.02, 0.1, and 0.2 mg / kg), respectively.

[0158] 1.8 Analysis of Material Pore Structure

[0159] The specific surface area and pore structure of biochar materials were analyzed and tested using a fully automated specific surface area and pore size analyzer. Samples were weighed, placed in test tubes, pretreated, and vacuum dried for 12 hours to remove impurities before testing at 77K in liquid nitrogen. Specific surface area was calculated using the Brunauer-Emmett-Teller method and the Langmuir method. Results were processed using the Barret, Joyner, and Halenda method (BJH method) to better reflect the pore structure of the samples.

[0160] 1.9 Structural Analysis of Materials Using Scanning Electron Microscopy

[0161] A Zeiss ULTRA55 scanning electron microscope was used. Before testing, the sample was vacuum dried at 120℃ for 12 hours. Then, the powder sample was attached to a copper column with conductive adhesive. Gold was sprayed onto the surface of the sample under a vacuum of 10⁻² mbar for 60 seconds. The copper column was then fixed to the sample stage with conductive adhesive for scanning. The working distance was set to 4.6 mm and the accelerating voltage was set to 3.00 kV.

[0162] Example 2

[0163] The purification effect of biochar materials on pigments in the matrix

[0164] Chrysanthemums contain numerous active ingredients, which not only make them a complex matrix for pesticide detection but also pose challenges to detection instruments. Among all components, pigments and fats cause the greatest difficulties in detection. The inventors discovered that a large amount of pigment can significantly affect the accuracy of results and lead to false positives. Furthermore, the presence of fats in the matrix may cause some lipophilic pesticides to accumulate in the fat, thus affecting the quality of results, the sensitivity of the method, sample throughput, and instrument maintenance and downtime. Therefore, the ability to remove pigments and fats is an important indicator for evaluating the pretreatment level of purification materials.

[0165] like Figure 1 As shown in Table 1, after purification with biochar, the color of the purified solution became significantly lighter, and the contents of lutein and chlorophyll in the matrix decreased by 71.03% and 85.34%, respectively. The fat content of the chrysanthemum extract without biochar purification was 1.2 g / 100g. -1 After purification with biochar materials, the fat content in the solution is 1.0g / 100g. -1 This demonstrates that the prepared biochar material has a high ability to purify pigments, and although its ability to purify fats is weaker, it can still remove a small portion of fats, making it suitable for pretreatment of pesticide residues in chrysanthemums.

[0166] Table 1

[0167]

[0168] To determine the specific dosage of biochar material, spiked recovery rate tests were conducted. According to the requirements of the Chinese Pharmacopoeia (2020 edition), pesticide residue detection methods should meet the requirement that the spiked recovery rate of each pesticide is between 70% and 120%, and can be appropriately relaxed to between 60% and 130% if repeatability is required. The spiked recoveries of phenylphosphine (calculated as the sum of phenylphosphine, phenylphosphine sulfone, and phenylphosphine sulfoxide), phorate (calculated as the sum of phorate, phorate sulfone, and phorate sulfoxide), aldicarb (calculated as the sum of aldicarb, aldicarb sulfone, and aldicarb sulfoxide), and terbufos (calculated as the sum of terbufos, terbufo sulfone, and terbufo sulfoxide) were considered acceptable within the range of 180-390%. The spiked recoveries of carbofuran (calculated as the sum of carbofuran and 3-hydroxycarbofuran) and demeton-methyl (calculated as the sum of demeton-O and demeton-S) were considered acceptable if they reached 120-260%. Specifically, in the preparation of chrysanthemum extract, a mixed standard solution prepared from 31 pesticides was added to the centrifuge tube, and the remaining operations were consistent with the methods described in sections 1.2 and 1.3.

[0169] After purification with different amounts of biochar material, the pesticide spike recovery rates in the matrix were as follows: Figure 2 As shown. Figure 2 A compares the recoveries of 15 pesticides at six spiking levels. From... Figure 2 As observed in Figure A, with the increase of biochar material dosage, the spiked recoveries of six pesticides—terbufos, thion, phosmet, amitraz, methyl isofenphos, and terbufos—gradually increased to the acceptable limit. This may be because when the biochar material dosage is low, the purification of interfering substances in the chrysanthemum extract is insufficient, masking trace amounts of pesticides and thus resulting in spiked recoveries failing to meet the standard. The spiked recoveries of phosmet and thion decreased to some extent with increasing biochar material dosage. However, regardless of changes in biochar material dosage, the spiked recoveries of mefenoxam remained below the specified range. Figure 2 C). Figure 2 D represents the compiled spiked recovery rates of 15 pesticides, excluding 6 pesticides such as benzoyl peroxide. As shown in the figure, the spiked recovery rates of all 15 pesticides increased significantly with the increase in biochar material dosage. The number of pesticides with spiked recovery rates in the range of 60-120% increased with the increase in biochar material dosage. Considering both pigment removal ability and spiked recovery rate, this example ultimately selected 180 mg of biochar material for subsequent experiments.

[0170] Example 3

[0171] To achieve better purification results, this embodiment uses commercially available degreasing and purifying agents PSA and C18, combined with biochar materials. The purification effect is as follows: Figure 3 and Figure 4As shown in the figure, compared with the unpurified chrysanthemum extract, the pigment removal effect was significantly improved after purification with biochar material combined with PSA and / or C18. The spiked recovery results also show that the spiked recovery rate of 31 pesticides was improved after combining biochar material with PSA and / or C18. After combining biochar material with PSA, among the 31 pesticides, only the spiked recovery rates of phosmet, phorate, methamidophos, and demeton-methyl did not meet the spiked recovery rate standard, with spiked recovery rates of 54.21%, 134.18%, 1413.41%, and 111.05%, respectively. Figure 4 As shown, the results obtained from the combination of biochar material with PSA and C18 were similar to those obtained from the combination of biochar material with PSA alone. However, the recovery rate of amitraz in the combination of biochar material with PSA and C18 decreased to below the acceptable level. Finally, 180 mg biochar + 30 mg PSA was selected as the adsorbent (purification material) for the QuEChERS method to detect the spiked recoveries of 31 pesticides in chrysanthemum.

[0172] To test whether the prepared biochar material can replace the adsorbents commonly used in the commercially available QuEChERS method, this example compares the purification effects of GCB, MWCNTs, PSA, and C18 with those of the biochar material. The results are as follows: Figure 3 As shown in the figure, compared with unpurified chrysanthemum extract, GCB (graphitized carbon black) has the best pigment purification ability among commercially available purification materials, followed by MWCNTs (multi-walled carbon nanotubes), then PSA, while C18 has poor pigment purification ability. Comparing the spiked recoveries of several groups, at the same dosage, pesticide spiked recoveries of 16.13%, 16.13%, 16.13%, and 19.36% respectively failed to meet the requirements. Specifically, GCB has a strong adsorption capacity for amitraz, resulting in a spiked recovery of only 14.22% for amitraz; while MWCNTs performed better than GCB. Another commercially available QuEChERS method adsorbent with strong adsorption capacity, PSA, showed lower spiked recoveries for sulfonamide pesticides (including amphetamine sulfate, mesosulfuron, and chlorsulfuron) than all test groups. Biochar materials and purification materials compounded with PSA can solve the above two problems. The spiked recoveries of amitraz and sulfonamide pesticides (including amitraz, mesosulfuron, and chlorsulfuron) are all within the acceptable limits.

[0173] Tables 2 and 3 list the linear regression equations, linear ranges, limits of detection, limits of quantitation, and recoveries of 31 pesticides in chrysanthemum matrix after purification with optimized purification material (180 mg biochar + 30 mg PSA). The purified chrysanthemum matrix solutions were spiked at concentrations of 0.02 mg / kg, 0.1 mg / kg, and 0.2 mg / kg, and the recoveries were determined (n = 6). The results showed good linearity between peak area and concentration, with a correlation coefficient (R²) of [missing value]. 2 The range was 0.9980–0.9998. The limits of detection (LOD) and lowest detection (LOD) for all pesticides were calculated as 3 times and 10 times the signal-to-noise ratio (S / N) of the quantitative ion pair, respectively. The method detection limit was 0.00002–0.0054 mg / kg, and the limit of quantitation ranged from 0.00007–0.01638 mg / kg. Except for mefenoxam, the recoveries of the 31 pesticides were all within the acceptable range, with relative standard deviations ranging from 0.93% to 21.54%.

[0174] Table 2. Linear regression equations, linear ranges, LOD (mg / kg), LOQ (mg / kg), recoveries, precision, and relative standard deviations (RSD) of 15 pesticides in chrysanthemum substrate (n=6)

[0175]

[0176] Table 3. Linear regression equations, linear range, LOD (mg / kg), LOQ (mg / kg), recovery rate, precision, and relative standard deviation (RSD) for six pesticides (n=6)

[0177]

[0178] Figure 5 This study compares the matrix effects of 31 pesticides in chrysanthemum extract purified with optimized purification materials. The figure shows that all 31 pesticides exhibit matrix effects. For 19.35% of the pesticides, the matrix effect is within ±20%, indicating they are largely unaffected by matrix effects. The other pesticides show medium to high matrix effects, which affect the accuracy of pesticide quantification. Therefore, a standard curve was prepared using chrysanthemum matrix extract to accurately quantify the 31 pesticides.

[0179] Example 4

[0180] In this embodiment, the biochar material before and after adsorption was characterized using a specific surface area analyzer and a scanning electron microscope.

[0181] Figure 6These are scanning electron microscope (SEM) images of the biochar material before and after adsorption. Overall, the biochar material exhibits a three-dimensional porous structure. Compared to the highly ordered structure of graphitized carbon black, the structure of biochar is more disordered, which may explain why it does not retain many pesticides but retains pigments. After adsorption, the structure of the biochar material collapses to some extent, with the pores changing from nearly circular to crescent-shaped. The pores become smaller, the pore boundaries are no longer clear, and it is covered with many fine particles. Under magnification, it can be observed that the surface of the biochar material before adsorption is relatively smooth, while the surface of the biochar material after adsorption increases in three-dimensionality, and more regular spherical particles can be observed.

[0182] To investigate the pore structure of biochar materials, the specific surface area and pore structure of the biochar materials were analyzed and tested using a fully automated specific surface area and pore size analyzer. The results are as follows: Figure 7 As shown, the adsorption capacity increases rapidly with increasing pressure, reaching saturation at a certain pressure. This phenomenon is generally referred to as a Type I adsorption isotherm, mainly due to the rapid saturation of adsorption capacity in the narrow micropores of the material at relatively low pressure. Pore size analysis also confirms this; the figure shows that the pore size of the biochar material is <5 nm, indicating that the biochar material prepared in this invention is microporous biochar. The specific surface area of ​​the obtained biochar material was measured to be 351.43 m². 2 / g.

[0183] Example 5

[0184] This embodiment optimizes the method of Example 1 and examines the purification effect of the optimized biochar material on pigments in other medicinal crop samples (such as honeysuckle and mulberry leaves).

[0185] 5.1 Screening of biomass materials

[0186] The purchased corn stalks, basa sawdust, and loofah sponges should be processed as follows:

[0187] Corn stalks: After drying the corn stalks in an oven at 60℃ overnight, cut them into small pieces with scissors, crush them in a pulverizer, pass them through a 40-mesh sieve, and store them in a sealed bag for later use.

[0188] Balsa wood chips: Dry balsa wood chips in an oven at 60°C overnight, then seal and store for later use.

[0189] Loofah pulp: After washing away any loofah flesh and seeds with deionized water, dry in an oven at 60℃. After drying, cut into small pieces with scissors, further grind in a grinder, and then seal for later use.

[0190] Preparation of biochar materials based on corn stalks, basa wood chips, and loofah sponge

[0191] To evaluate the adsorption performance of the three biomass materials, biochar materials were prepared using the scheme of Example 1, with each of the three biomass materials as raw materials. Specifically, the biomass materials were impregnated with sodium hypochlorite, followed by hydrothermal treatment in a reaction vessel, drying, and then carbonization in a tubular furnace to obtain the final biochar materials.

[0192] The purification effects of biochar materials prepared based on three biomass materials on pigments in honeysuckle extract are shown in Table 4 (30 mg biochar material, 2.5 g honeysuckle, preparation method of honeysuckle extract is shown below). The results in Table 4 show that all biochar materials prepared based on the three biomass materials can directionally adsorb pigments in honeysuckle extract, with corn straw showing the best pigment purification effect.

[0193] Table 4

[0194]

[0195] The preparation method of medicinal crop extract (pretreatment of medicinal materials) is as follows: First, the medicinal crop (e.g., honeysuckle, mulberry leaves) is pulverized and passed through a 40-mesh sieve. 2.5g of the sieved medicinal crop powder is placed in a 50mL centrifuge tube, along with 1g of sodium chloride and one ceramic homogenizer suitable for a 50mL centrifuge tube, and 25mL of acetonitrile. The mixture is vortexed for 5 minutes at 3000r / min using a high-powered multi-tube vortex mixer. The supernatant is then collected after centrifugation. Another 25mL of acetonitrile is added to the centrifuge tube, and the vortexing and centrifugation are repeated three times. The combined supernatants are then concentrated using a parallel concentrator. After concentration, 5mL of acetonitrile is added to the tube to reconstitute the extract, yielding the medicinal crop extract.

[0196] 5.2 Optimization of Preprocessing Methods

[0197] Next, the following three methods for delignination were selected to treat corn stalks: (1) sodium hydroxide + sodium sulfite, (2) hydrogen peroxide, and (3) sodium hypochlorite.

[0198] (1) Sodium hydroxide + sodium sulfite: Add 250 mL each of sodium hydroxide (2.5 mol / L) and sodium sulfite (0.4 mol / L) to a beaker. Heat the solution to boiling, add corn stalk powder, maintain a gentle boil for 2 hours, filter out the corn stalk powder, rinse with plenty of deionized water, and dry in an oven at 60°C to obtain the final product.

[0199] (2) Hydrogen peroxide: Hydrogen peroxide (2.5 mol / L) was added to corn stalk powder at a ratio of 1 g powder to 50 mL, dispersed, heated to a slight boiling state and maintained for 2 h. After 2 h, it was filtered and washed, and finally dried in an oven at 60 °C to obtain the final product.

[0200] (3) Sodium hypochlorite: Sodium hypochlorite (effective chlorine concentration ≥5%) was added to corn stalk powder at a ratio of 1g powder to 50mL, dispersed, and allowed to stand for 4 hours. After 4 hours, the corn stalk powder was filtered and washed, and finally dried in an oven at 60℃ to obtain the final product.

[0201] The optimal pretreatment method was evaluated based on the pigment purification effect of each group of materials on chlorophyll and xanthophyll in honeysuckle.

[0202] The possible principles of the three pretreatment methods for delignification of biomass materials are as follows:

[0203] In the sodium hydroxide + sodium hypochlorite combination, sodium sulfite reacts with water in solution to generate reducing sulfurous acid (H₂SO₃). This reducing agent can reduce certain functional groups in lignin, thereby destroying the phenolic groups and other functional groups, making its structure unstable and promoting its decomposition. Sodium hydroxide provides an alkaline environment for sodium sulfite. Under alkaline conditions, the water solubility of lignin increases, reducing its adhesion between cellulose chains and thus promoting lignin dissolution. Hydrogen peroxide and sodium hypochlorite are both oxidizing agents that can generate hydroxyl radicals (·OH) and other reactive oxygen species under appropriate conditions. Hydroxyl radicals are highly reactive and can attack the phenolic hydroxyl groups and aromatic rings in lignin, leading to lignin breakage and oxidation, thereby reducing the degree of polymerization of lignin and achieving a delignification effect.

[0204] The comparison results of the three pretreatment methods (30mg biochar material) on the pigment purification effect of honeysuckle are shown in Table 5-1 below.

[0205] Table 5-1

[0206]

[0207] The comparison results of the pigment purification effects of three pretreatment methods (30mg biochar material) on mulberry leaves are shown in Table 5-2 below.

[0208] Table 5-2

[0209]

[0210] As can be seen from Tables 5-1 and 5-2, the pigment purification capacity of biochar materials prepared by the three pretreatment methods in honeysuckle matrix is: hydrogen peroxide > sodium hypochlorite > sodium hydroxide + sodium sulfite. The pigment purification capacity in mulberry leaf matrix is: sodium hypochlorite > hydrogen peroxide > sodium hydroxide + sodium sulfite.

[0211] The above results indicate that not all delignination methods are suitable for pretreatment of biomass materials. This may be because the principle of lignin removal using sodium hydroxide and sodium sulfite is to dissolve some of the lignin, while the principle of lignin removal using hydrogen peroxide and sodium hypochlorite is to oxidize the lignin, thereby destroying its structure. This destruction of the lignin structure may further increase the specific surface area of ​​the biochar material, thus making its pigment purification ability superior to the sodium hydroxide + sodium sulfite group. Furthermore, the pigment purification abilities of the biochar materials treated with hydrogen peroxide and sodium hypochlorite in honeysuckle are similar to those in mulberry leaves. Considering the price, risk factor, and availability of hydrogen peroxide and sodium hypochlorite, sodium hypochlorite was ultimately chosen for subsequent experiments.

[0212] 5.3 Optimization of carbonization process

[0213] Based on whether lignin removal, hydrothermal treatment, and pyrolysis carbonization were performed, the samples were divided into 5 groups as follows:

[0214] 1. Lignification + Hydrothermal + Pyrolysis

[0215] 2 Direct pyrolysis

[0216] 3. Hydrothermal + Pyrolysis

[0217] 4. Delignination + hydrothermal treatment

[0218] 5. Delignination + Pyrolysis

[0219] The hydrothermal treatment steps specifically include: adding an appropriate amount of pretreated corn stalk powder and a small amount of water to the polytetrafluoroethylene lining of a laboratory reactor (the volume should not exceed 2 / 3 of the reactor lining's capacity). After closing the reactor and tightening the reactor screws, move the entire reactor into an oven. Set the oven temperature to 220℃ and treat for 4 hours. After the reactor has cooled naturally in the oven, remove it. Open the reactor lining and filter the contents. After washing with deionized water, dry it in a vacuum drying oven at 60℃. After passing through a 40-mesh sieve, the carbonized precursor is obtained.

[0220] The specific steps of pyrolysis carbonization include: After opening the N2 gas cylinder connected to the tubular furnace, purging the furnace tubes for approximately 5 minutes, then placing an appropriate amount of carbonization precursor into a quartz boat (the amount to be carbonized each time should be determined based on the surface area of ​​the quartz boat). After placing the carbonization precursor along with the quartz boat in the center of the furnace tubes, install the furnace flange and immerse the furnace exhaust pipe in an aqueous solution. Set the furnace temperature to 800℃ and the heating rate to 5℃ / min. After carbonization is complete, turn off the furnace power and maintain nitrogen purging for a period of time. Once the furnace has cooled to room temperature, remove the quartz boat.

[0221] The optimal carbonization process was evaluated based on the purification effect of each group of materials on chlorophyll and xanthophyll in honeysuckle.

[0222] 60 mg of biochar material prepared by each of the five carbonization processes was taken and tested for its adsorption effect on pigments in honeysuckle extract (a. hydrothermal + pyrolysis, b. delignification + pyrolysis, c. delignification + hydrothermal, d. delignification + hydrothermal + pyrolysis, e. direct pyrolysis). The results are shown in Table 6-1 below. Figure 8 The results of the test on the adsorption effect of pigments in mulberry leaf extract are shown in Table 6-2 below. Figure 8 The results are shown in the figure below. The results show that the biochar material prepared by the carbonization process of delignification + hydrothermal + pyrolysis exhibits excellent pigment purification effect and is suitable for the pretreatment of complex matrices of different medicinal materials (such as chrysanthemum, honeysuckle, mulberry leaves, etc.).

[0223] The purification effects of honeysuckle and mulberry leaf extracts showed a consistent ranking: delignification + hydrothermal treatment + pyrolysis treatment group > hydrothermal treatment + pyrolysis treatment group > delignification + pyrolysis treatment group > direct pyrolysis group > delignification + hydrothermal treatment group. The results indicate that delignification, hydrothermal treatment, and pyrolysis treatment have a synergistic effect, and the absence of any one of these processes significantly affects the adsorption performance of the final product.

[0224] Hydrothermal treatment contributed more to the adsorption performance of biochar than delignification treatment, which may be related to the significant increase in oxygen-containing functional groups on the surface of corn stalks during hydrothermal treatment. The purified liquid from the delignification + hydrothermal treatment group exhibited a significant color difference anomaly, possibly attributed to the high-pressure, high-temperature hydrothermal environment intensifying lignin dissolution, leading to a color-changing effect of dissolved lignin under the action of organic solvents. Based on these experimental results, a combination of delignification, hydrothermal treatment, and pyrolysis of corn stalks was ultimately chosen to prepare biochar materials for the purification of honeysuckle and mulberry leaf extracts.

[0225] Table 6-1: Comparison of pigment purification effects in honeysuckle extract

[0226]

[0227] Table 6-2: Comparison of pigment purification effects in mulberry leaf extract

[0228]

[0229] 5.4 Optimization of carbonization temperature

[0230] Based on the optimized carbonization process in section 5.3, the carbonization temperature was further optimized, specifically by conducting pyrolysis at five temperatures: 500, 600, 700, 800, and 900℃. The optimal carbonization temperature was evaluated based on the purification effects of each material group on chlorophyll and xanthophyll in honeysuckle.

[0231] The purification effects of 30 mg of biochar material obtained by pyrolysis of carbonized precursors at 500, 600, 700, 800, and 900℃ on chlorophyll and xanthophyll in honeysuckle extract were compared. The results are shown in Table 7 below. The results show that maintaining the carbonization temperature between 500 and 900℃ can achieve better pigment purification effects.

[0232] Table 7

[0233]

[0234] Note: The reason for the difference between the results of honeysuckle extract in Table 7 and the blank groups in Tables 4 and 5-1 is that the honeysuckle extract was diluted by a factor of 6 in this experiment.

[0235] 5.5 Functionalization Method Optimization

[0236] To further optimize the adsorption performance of biochar materials, acid functionalization treatment was performed. Specifically, a small amount of biochar material and a prepared acid solution were mixed in a stoppered conical flask at a ratio of 250 mg biochar to 250 mL sodium acid solution, and allowed to stand overnight. The next day, the biochar material was washed with deionized water until the pH of the effluent was neutral. The material was then dried in a vacuum drying oven to obtain the acid-functionalized biochar material. The experimental groups are as follows:

[0237] 1. Hydrochloric acid

[0238] 2. Sulfuric acid

[0239] 3 nitric acid

[0240] 4 hydrochloric acid + sulfuric acid

[0241] 5 hydrochloric acid + nitric acid

[0242] 6 sulfuric acid + nitric acid

[0243] 7. Hydrochloric acid + sulfuric acid + nitric acid

[0244] Note: The concentrations of nitric acid, hydrochloric acid, and sulfuric acid are approximately 0.5 mol / L; hydrochloric acid + sulfuric acid refers to the concentrations of hydrochloric acid and sulfuric acid being approximately 0.5 mol / L each.

[0245] The results of the acid-functionalized biochar material (30mg) on ​​the pigment purification effect (honeysuckle) are shown in Table 8. Acid functionalization treatment with hydrochloric acid, sulfuric acid, and nitric acid improved the purification effect of the biochar material on the pigments in honeysuckle extract. Among these, the biochar material treated with hydrochloric acid and / or nitric acid showed the best pigment purification effect.

[0246] Table 8

[0247]

[0248] The results of the acid-functionalized biochar material (30mg) on ​​pigment purification (mulberry leaf) are shown in Table 9. Acid functionalization treatment with hydrochloric acid, sulfuric acid, and nitric acid improved the purification effect of the biochar material on pigments in mulberry leaf extract. Among these, the biochar material treated with sulfuric acid and nitric acid showed the best pigment purification effect. After comprehensive evaluation, nitric acid was ultimately selected for acid functionalization of the biochar.

[0249] Table 9

[0250]

[0251] Infrared spectral characteristics of biochar materials functionalized with nitric acid, such as Figure 9 As shown. In the original biochar sample (the difference between the original biochar sample and the biochar material after nitric acid functionalization is that the original biochar sample was not functionalized with nitric acid), 3398 cm⁻¹ -1 The nearby weak absorption peaks are attributed to the OH stretching vibration modes of alcohols, phenols, and adsorbed water, and may also include the NH stretching vibration mode; 1557 cm⁻¹ -1 The broad peak shape in the vicinity is mainly located in the characteristic absorption region of aromatic compounds and is related to the C=C stretching vibration mode of the benzene ring. This peak is relatively broad and may also contain some carbonyl C=O stretching vibration modes; at 1092 cm⁻¹ -1 The strong peaks in the vicinity are mainly attributed to the Si-O and CO stretching vibration modes, at 799 cm⁻¹. -1 The nearby absorption peaks are related to the out-of-plane CH stretching vibration mode of the aromatic ring and the Si-O symmetric stretching vibration mode. From the above qualitative results, it can be seen that the biochar samples mainly contain OH, C=C, and CO groups. These functional groups can form stable bonds with other small molecules through physical and chemical interactions, thereby effectively removing these components through different adsorption mechanisms. Of course, the pore size distribution and specific surface area of ​​biochar also affect the diffusion and adsorption of small molecule compounds in biochar. At 1092 cm⁻¹... -1 and 799cm -1 The absorption peak intensity at this point is extremely high, indicating that the content of organic groups on the surface of the biochar material is low, which may be due to the high preparation temperature of the biochar.

[0252] The infrared spectral characteristics of the biochar material (HNO3-BC) after nitric acid functionalization did not change significantly, but at 1386 cm⁻¹... -1 The presence of a sharp peak in the -NO2 stretching vibration nearby confirms the successful modification of biochar material by nitric acid. This modification process can improve adsorption efficiency by introducing oxygen-containing functional groups such as -NO2 and NO3- onto the surface of biochar material, which can then form stable complexes with various interfering substances through chemical reactions or coordination.

[0253] Nitric acid modification increases the surface oxygen, nitrogen, and silicon content of biochar materials. The increased silicon content may be due to the reduction of carbon content in the biochar material after nitric acid modification, which indirectly increases the silicon content. The increase in oxygen and nitrogen is due to the oxidation of the biochar surface by nitric acid, which adds new functional groups to the biochar surface.

[0254] Analysis of the adsorption isotherms of the nitric acid-functionalized biochar material reveals that both adsorption and desorption belong to type IV(a) adsorption isotherms, and both adsorption isotherms exhibit H3-type hysteresis loops. This type of hysteresis loop is commonly found in slit-type mesoporous materials. As shown in Table 10, after BET fitting, the specific surface area of ​​the nitric acid-functionalized biochar material is 249.52 m². 2 ·g -1 This phenomenon may be caused by the oxidation and destruction of some of the pore structure during the nitric acid impregnation process.

[0255] Table 10

[0256]

[0257] The embodiments of the present invention have been described above with reference to the accompanying drawings. However, the present invention is not limited to the specific embodiments described above. The specific embodiments described above are merely illustrative and not restrictive. Those skilled in the art can make many other forms under the guidance of the present invention without departing from the spirit and scope of the claims. All of these forms are within the protection scope of the present invention.

Claims

1. The application of a biochar material in the preparation of a QuEChERS-based pesticide residue pretreatment reagent, characterized in that, The pesticide residue pretreatment reagent is used for the targeted adsorption of pigments in the sample, which includes medicinal crop samples. The biochar material is prepared by the following method: S101 Biomass materials are added to the first solution for pretreatment to obtain the first mixture; S102 The biomass material in the first mixture is placed in water and subjected to a hydrothermal reaction to obtain the first precursor; S103 Vacuum dry the first precursor to obtain the second precursor; S104 Carbonizes the second precursor to obtain the first material; S105 The first material is immersed in the second solution for a second time period and then vacuum dried to obtain the biochar material; Wherein, the first solution includes hydrogen peroxide solution or hypochlorite solution; the hydrothermal reaction temperature in step S102 includes 200-240℃, and the hydrothermal reaction time includes 4-6 hours; the carbonization setting temperature in step S104 includes 500-900℃, and the carbonization heating rate includes 5-10℃ / min; the second solution includes hydrochloric acid, nitric acid, or a combination thereof; when the first solution is hypochlorite solution, the pretreatment method includes: soaking the biomass material in the hypochlorite solution for a first time period to obtain a first mixture; the ratio of the biomass material to the hypochlorite solution includes 1.0g:40-60mL.

2. The application as described in claim 1, characterized in that, The samples include chrysanthemum samples, honeysuckle samples, or mulberry leaf samples.

3. The application as described in claim 1, characterized in that, The pesticide residue pretreatment reagent also includes an adsorption material.

4. The application as described in claim 1, characterized in that, The biomass materials include straw, sawdust, or loofah sponge.

5. The application of a biochar material in the preparation of a QuEChERS-based sample pretreatment kit, characterized in that, The sample pretreatment kit includes a pesticide residue pretreatment reagent, which includes the biochar material. The pesticide residue pretreatment reagent is configured for pretreatment and purification of a medicinal crop sample. The biochar material is prepared by the following method: S101 Biomass materials are added to the first solution for pretreatment to obtain the first mixture; S102 The biomass material in the first mixture is placed in water and subjected to a hydrothermal reaction to obtain the first precursor; S103 Vacuum dry the first precursor to obtain the second precursor; S104 Carbonizes the second precursor to obtain the first material; S105 The first material is immersed in the second solution for a second time period and then vacuum dried to obtain the biochar material; Wherein, the first solution includes hydrogen peroxide solution or hypochlorite solution; the hydrothermal reaction temperature in step S102 includes 200-240℃, and the hydrothermal reaction time includes 4-6 hours; the carbonization setting temperature in step S104 includes 500-900℃, and the carbonization heating rate includes 5-10℃ / min; the second solution includes hydrochloric acid, nitric acid, or a combination thereof; when the first solution is hypochlorite solution, the pretreatment method includes: soaking the biomass material in the hypochlorite solution for a first time period to obtain a first mixture; the ratio of the biomass material to the hypochlorite solution includes 1.0g:40-60mL.

6. The application as described in claim 5, characterized in that, The pesticide residue pretreatment reagent is configured for pretreatment purification of a honeysuckle sample or a mulberry leaf sample.

7. The application as described in claim 5, characterized in that, The pesticide residue pretreatment reagent also includes an adsorption material.

8. The application as described in claim 5, characterized in that, The biomass materials include straw, sawdust, or loofah sponge.

Images