Biochar material as well as preparation method and application thereof

Abstract

The invention relates to the field of biochar materials, in particular to a biochar material and a preparation method and application thereof. The invention provides a preparation method of a biochar material, which is characterized by comprising 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 invention can perform directional adsorption on pigments (such as lutein and chlorophyll), and is suitable for being applied to QuEChERS method pretreatment.

Description

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

[0002] The present invention relates to the field of biochar materials, and in particular to a biochar material and a preparation method and application thereof. Background Art

[0003] With the expansion of the planting area of ​​medicinal crops and the extension of the planting years, the occurrence of diseases, insect pests and weeds in medicinal crops is becoming more and more serious. At present, the prevention and control of diseases, insect pests and weeds in the production of medicinal crops in my country mainly rely on chemical pesticides. However, unreasonable use of pesticides may bring potential hazards of pesticide residues. Therefore, it is necessary to monitor people's food safety by detecting pesticide residues in medicinal crops.

[0004] Chrysanthemum is a multifunctional medicinal crop. Its pharmacological effects include clearing away heat and detoxifying, calming the liver and improving eyesight, antibacterial and anti-inflammatory, lowering blood lipids, anti-oxidation, vasodilation, lowering blood pressure, and anti-tumor. 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, the problem of pests and diseases has become increasingly prominent. In order to pursue high yields and ensure the quality of chrysanthemums, growers have no choice but to take pesticide control measures to protect chrysanthemums from pests and diseases. This practice has also raised the dual issues of food safety and ecological safety. Compared with other plants, chrysanthemums have a complex composition. They not only contain a large amount of pigments, but also a large amount of oils, flavonoids and other ingredients, which puts higher requirements on the detection method of pesticide residues in chrysanthemums.

[0005] Honeysuckle is a traditional Chinese medicinal and edible plant. It is widely distributed and has ornamental, economic, edible and strong medicinal value. Honeysuckle is susceptible to pests and diseases during the planting process. Many growers choose chemical pesticides to prevent and control them. Therefore, honeysuckle is a key focus variety for excessive pesticide residues. The biggest challenge encountered by the mainstream detection methods currently used in the detection of trace pesticide residues in honeysuckle is the presence of pigments in honeysuckle. This is because the color of honeysuckle crops changes during development due to changes in their endogenous pigments, and these pigment components will cause great interference to trace pesticide detection. In addition, the honeysuckle matrix is ​​characterized by dark color and contains a large amount of lutein and chlorophyll. Therefore, the detection of pesticide residues in honeysuckle is challenging.

[0006] Mulberry leaves are a commonly used and bulky variety of Chinese medicinal materials, and are both medicinal and edible. Modern pharmacological studies have shown that mulberry leaves have multiple pharmacological effects, including anti-inflammatory, antioxidant, anti-tumor, hypoglycemic, lipid-regulating, liver and heart protection. In addition, as the main food source for silkworms, the safety of mulberry leaves is directly related to the health of silkworms, which in turn affects the yield of silk. In recent years, with the increasing number of pesticide types and usage, mulberry leaves have become a key focus of attention for pesticide residues that are prone to exceeding the standard. However, the challenges encountered by the mainstream detection methods currently used in the detection of trace pesticide residues in mulberry leaves are the presence of a large amount of lutein and chlorophyll as well as flavonoids and polysaccharides in mulberry leaves.

[0007] The pesticide residue analysis process includes two parts: sample pretreatment and instrumental analysis. The cumbersome sample pretreatment seriously limits the analysis efficiency. The development of the QuEChERS method has simplified the operational process of sample pretreatment, among which the selection of purifiers is crucial, mainly affecting the purification effect of the matrix and the recovery rate of pesticides. The specific surface area, porous structure and adjustable surface chemical properties of carbon materials have gradually emerged in the improvement of the QuEChERS method. Carbon materials such as carbon nanotubes, carbon dots, graphene / graphene oxide, fullerene and its derivatives have achieved good results, but the raw materials of the above carbon materials are mostly derived from petroleum substrates, which are not only not environmentally friendly, but also consume a huge amount of non-renewable resources such as petroleum.

[0008] Biochar material is a material derived from biomass as a carbon source. It not only has a wide range of sources, but also has a certain adsorption capacity. Therefore, it can be used as an adsorbent to adsorb pesticides to achieve the removal of pesticide residues. However, for pesticide residue analysis, the prior art usually uses metal ions (such as ZnCl2) or metal oxides (such as Fe3O4) to modify the biochar material, so as to apply the modified biochar material to the sample pretreatment stage of pesticide residue analysis. Chinese patent application CN117191536A discloses the use of a magnetic biochar material as a purifier in the QuEChERS pretreatment method, wherein the magnetic biochar material is Fe3O4-modified biochar, which clearly mentions that biochar is not easy to separate when used directly in the sample pretreatment process, so Fe3O4 needs to be assembled on the biochar material before it can be applied to pesticide residue analysis. Summary of the invention

[0009] In a first aspect, the present invention provides a method for preparing a biochar material, characterized in that it comprises the following steps:

[0010] S101: adding biomass material to the first solution for pretreatment to obtain a first mixed solution;

[0011] In some embodiments, the biomass material includes straw, wood chips, or loofah.

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

[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: soaking the biomass material in the hypochlorite solution for a first period of time to obtain a first mixed solution.

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

[0018] In some embodiments, the effective chlorine content of the hypochlorite solution comprises 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 period of time to obtain a first mixed solution.

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

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

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

[0023] S102 placing the biomass material in the first mixed solution in water and performing a hydrothermal reaction to obtain a first precursor;

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

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

[0026] S103 vacuum-drying the first precursor to obtain a second precursor;

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

[0028] In some embodiments, the carbonization temperature is set to be 500-900°C.

[0029] In some embodiments, the carbonization temperature is set to be 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 is 5-10° C. / min.

[0032] S105: Soak the first material in a second solution for a second period of time, and obtain the biochar material after vacuum drying.

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

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

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

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

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

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

[0039] In a second aspect, the present invention provides a biochar material prepared by the above preparation method.

[0040] In a third aspect, the present invention provides the use 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 targeted adsorption of pigments in the sample.

[0042] In the present invention, "directional adsorption" means that in the presence of a matrix of the sample, the pigment (such as chlorophyll and / or xanthophyll) contained in the sample is selectively adsorbed, while trace amounts of pesticides are hardly adsorbed.

[0043] In some embodiments, the pigment comprises 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 Chinese medicinal materials samples.

[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 pre-treatment reagent also includes an adsorption material.

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

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

[0051] In some embodiments, the pesticide residue pre-treatment 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 comprises (5-8):1.

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

[0054] In a fourth aspect, the present invention further provides a sample pretreatment kit based on QuEChERS, characterized in that the sample pretreatment kit comprises a pesticide residue pretreatment reagent, and the pesticide residue pretreatment reagent comprises the above-mentioned biochar material.

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

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

[0057] In some embodiments, the pesticide residue pre-treatment reagent also includes an adsorption material.

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

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

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

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

[0062] In some embodiments, the mass ratio of the pesticide residue pretreatment reagent to the medicinal crop sample comprises 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 the medicinal crop sample is 2.5 g, the pesticide residue pretreatment reagent may include 125-500 mg, 150-225 mg or 180-240 mg of biochar material.

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

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

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

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

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

[0070] In a fifth aspect, the present invention also provides a method for detecting a plurality of 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: adding 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 the form of a powder.

[0073] S202: adding the medicinal crop extract (preferably 1 / 3 of the medicinal crop extract obtained in S201) to the pesticide residue pretreatment reagent for extraction by shaking, and then filtering the supernatant and injecting it into an HPLC-MS / MS instrument for trace pesticide residue detection;

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

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

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

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

[0078] In some embodiments, the mass ratio of the pesticide residue pretreatment reagent to the medicinal crop sample comprises 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 the medicinal crop sample is 2.5 g, the pesticide residue pretreatment reagent may include 125-500 mg, 150-225 mg or 180-240 mg of biochar material.

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

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

[0083] S203 uses high performance liquid chromatography to separate the supernatant of S202, wherein the high performance liquid chromatography uses a C18 chromatographic column, the column temperature is 40° C., and 0.1% formic acid acetonitrile solution is used as mobile phase A and 0.1% formic acid water is used as mobile phase B for gradient elution;

[0084] S204 uses tandem mass spectrometry to analyze the substances separated by the high performance liquid chromatography described in S203, using ESI as the ion source and adopting a multi-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] In a sixth aspect, the present invention also provides an application of the above-mentioned biochar material in the preparation of a QuEChERS-based sample pretreatment kit, characterized in that the sample pretreatment kit comprises a pesticide residue pretreatment reagent, and the pesticide residue pretreatment reagent comprises the biochar material.

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

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

[0095] In some embodiments, the pesticide residue pre-treatment reagent also includes an adsorption material.

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

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

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

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

[0100] In some embodiments, the mass ratio of the pesticide residue pretreatment reagent to the medicinal crop sample comprises 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 the medicinal crop sample is 2.5 g, the pesticide residue pretreatment reagent may include 125-500 mg, 150-225 mg or 180-240 mg of biochar material.

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

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

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

[0106] In some embodiments, the sample pretreatment kit further comprises an anhydrous polar reagent, and the anhydrous polar reagent comprises 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] In order to apply biochar materials to pesticide residue analysis, the prior art usually uses metal ions (such as ZnCl2) or metal oxides (such as Fe3O4) to modify biochar materials. In fact, the prior art also believes that biochar materials that have not been activated or magnetically modified with metal ions are difficult to apply to pesticide residue analysis, especially difficult to use as a purifier in the QuEChERS pretreatment method.

[0110] The method for preparing the biochar material provided by the present invention creatively combines hypochlorite / hydrogen peroxide treatment, hydrothermal treatment and pyrolysis, and it is found that these three steps synergistically ensure the directional adsorption of pigments (such as lutein and chlorophyll) by the biochar material prepared by the present invention (that is, it has no retention effect on a variety of pesticides but has a retention effect on pigments), and is suitable for application to QuEChERS pre-treatment.

[0111] Specifically, the present invention utilizes hypochlorite (e.g., sodium hypochlorite) / hydrogen peroxide to treat straw powder to oxidize and degrade lignin in biomass materials (e.g., straw powder). However, the present invention finds that hypochlorite / hydrogen peroxide, as a broad-spectrum oxidant, will degrade part of the cellulose in the biomass material while oxidizing and degrading lignin, thereby destroying the pore structure of the biomass material, causing the pore structure of the biomass material to be further destroyed in the subsequent hydrothermal treatment and pyrolysis, and ultimately unable to generate biochar materials. Although sodium hydroxide + sodium hypochlorite can promote the dissolution of lignin, it cannot improve the directional adsorption performance of biochar materials for pigments. The present invention effectively reduces the binding force between lignin, cellulose, and hemicellulose in the biomass material and breaks the natural anti-degradation barrier of lignin by controlling the pretreatment method of the biomass material (e.g., the immersion time and ratio in the hypochlorite solution / hydrogen peroxide solution), while maintaining the integrity of the original structure of cellulose, giving the cellulose surface more oxygen-containing functional groups, and providing a structural basis for subsequent hydrothermal treatment and pyrolysis (i.e., ensuring the stability of the pore structure of biochar).

[0112] Further, the present invention sequentially hydrothermally treats and pyrolyzes the biomass material pretreated with hypochlorite / hydrogen peroxide (e.g., straw powder treated with hypochlorite). Since the pore structure of the pretreated biomass material has been changed to a certain extent, hydrothermally treating and pyrolyzing it still has an adverse effect on the stability of the pore structure of the biochar. For this, the present invention, by coordinating factors such as the temperature of the hydrothermal treatment and the pyrolysis, gives the cellulose surface retained by the pretreated biomass material more oxygen-containing functional groups, while ensuring that the stability of the pore structure of the biochar is not affected, further expands the pores on the cellulose surface, and increases the specific surface area of ​​the biochar material. Further, the present invention finds that, relative to sulfuric acid treatment, hydrochloric acid and / or nitric acid treatment at an appropriate concentration can produce better synergy with hypochlorite / hydrogen peroxide treatment, hydrothermal treatment, and pyrolysis to form a mesoporous material, further improving the purification effect and adsorption efficiency of pigments in complex matrices of different medicinal crop samples (especially honeysuckle samples and mulberry leaf samples).

[0113] Compared with the traditional adsorption material production process, the method provided by the present invention is cost-effective, the cost is significantly lower than that of petroleum or asphalt-based materials, and a large amount of energy can be saved, which is eco-friendly. In addition, the method provided by the present invention has a high yield, the prepared biochar material is of high quality, almost no by-products such as tar and ash are produced, the preparation difficulty and risk are low, and it has a good industrial application prospect.

[0114] In addition, it should be emphasized that the biochar material prepared by the present invention, without undergoing metal ion activation modification and / or magnetic modification, can unexpectedly be used as a directional adsorbent for the analysis of pesticide residues in complex matrices of different medicinal crop samples pre-treated by the QuEChERS method, achieving effective purification of pigments, fats, and flavonoids in medicinal crop extracts, while biochar materials obtained simply by hydrothermal treatment or pyrolysis are difficult to achieve the purification effect of pigments and fats in complex matrices. Based on the biochar material prepared by the present invention, the detection limit of the method for detecting multiple trace pesticide residues in honeysuckle using HPLC-MS / MS is 0.00001-0.00016 mg·kg -1 , the limit of quantification is 0.00002-0.00047mg·kg -1 ; The detection limit of the method for detecting various trace pesticide residues in mulberry leaves is 0.00001~0.0015mg·kg -1 , the limit of quantification is 0.00002~0.0004mg·kg -1 In addition, judging from the spiked recoveries of several pesticides that are greatly affected by the matrix and purification materials (e.g., ethametsulfuron-methyl, metsulfuron-methyl, chlorsulfuron-methyl, and chlordimeform), commercial adsorption materials (e.g., GCB, PSA) have adsorption effects on these pesticides, while the biochar material prepared by the present invention has no specific adsorption effect on these pesticides, and is therefore more suitable as a pretreatment reagent for pesticide residues based on the QuECHERS method.

[0115] The biochar material prepared by the present invention can be a good substitute for commercial adsorption materials (such as GCB). Compared with commercial adsorption materials, the biochar material prepared by the present invention has a lower preparation cost (the preparation cost per gram of biochar is about 0.5 US dollars) and is more eco-friendly. BRIEF DESCRIPTION OF THE DRAWINGS

[0116] In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, each element or part is not necessarily drawn according to the actual scale. Obviously, the drawings described below are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can also be obtained based on these drawings without paying creative labor.

[0117] Figure 1 The result diagram is a graph showing the pigment content in the matrix before and after purification by the biochar material of the present invention;

[0118] Figure 2This is the result diagram of the effect of different amounts of biochar materials on the spiked recoveries of 31 pesticides;

[0119] Figure 3 This is a comparison chart of the purification effect of biochar composite materials and commercially available materials;

[0120] Figure 4 This is a comparison chart of the purification effects of different materials;

[0121] Figure 5 This is a comparison of the matrix effects of 31 pesticides in chrysanthemum extracts purified by optimized purification materials;

[0122] Figure 6 This is the SEM result of the morphological changes of biochar materials before and after adsorption;

[0123] Figure 7 is the adsorption isotherm of biochar material;

[0124] Figure 8 The comparison results of the purification effect of optimized biochar materials on honeysuckle extract (above) and mulberry leaf extract (below);

[0125] Fig. 9 This is the infrared spectrum result of the biochar material after nitric acid functionalization treatment;

[0126] Fig.10 This is the adsorption isotherm of biochar material after nitric acid functionalization treatment. DETAILED DESCRIPTION

[0127] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of the present invention.

[0128] Herein "and / or" includes any and all combinations of one or more of the associated listed items.

[0129] Herein, "plurality" means two or more than two, ie, it includes two, three, four, five, etc.

[0130] It should be noted that, in this article, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "comprises a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element.

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

[0132] In this specification, some embodiments may be disclosed in a format of being in a range. It should be understood that this description of "being in a range" is only for convenience and brevity, and should not be interpreted as a rigid limitation on the disclosed range. Therefore, the description of the range should be considered to have specifically disclosed all possible sub-ranges and independent numerical values ​​within this range. For example, the description of the range 1-6 should be considered to have specifically disclosed sub-ranges 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., as well as individual numbers within this range, such as 1, 2, 3, 4, 5 and 6. Regardless of the breadth of the range, the above rules apply.

[0133] Detailed description with drawings

[0134] Figure 1 :A is a comparison of the unpurified chrysanthemum extract and the chrysanthemum extract purified by 180 / 240 mg biochar material. From left to right, they are the chrysanthemum extracts that are unpurified, purified by 180 mg biochar material, purified by 180 mg biochar material, purified by 240 mg biochar material, and purified by 240 mg biochar material. B is the chrysanthemum extract purified by 30, 60, 90, and 120 mg biochar material (from left to right). C is the quantitative result of the comparison of chlorophyll and lutein content in the solution purified by different amounts of biochar material.

[0135] Figure 2:A is the spiked recoveries of 15 pesticides (methamidophos, chlorfenthion, chlorpyrifos, ethametsulfuron, metsulfuron, chlorsulfuron, cadasthofos, chlorfenapyr, coumaphos, thiophanate-methyl, phosphamidon, monocrotophos, ethoxyproline, chlordimeform, methyl isofenphos, the same below) in the solution purified by different amounts of biochar materials. B is the spiked recoveries of 4 pesticides (fenamidophos, phorate, aldicarb and terbuthion, the same below) in the solution purified by different amounts of biochar materials. C is the spiked recoveries of 2 pesticides (carbofuran and demeton, the same below) in the solution purified by different amounts of biochar materials. D is the qualified rate of spiked recoveries of different pesticides in the solution purified by different amounts of biochar materials.

[0136] Figure 3 : A is the spiked recovery rate of 15 pesticides in the solution after purification by different biochar composite materials. B is the spiked recovery rate of 4 pesticides in the solution after purification by different biochar composite materials. C is the spiked recovery rate of 2 pesticides in the solution after purification by different biochar composite materials. D is the spiked recovery rate of 15 pesticides in the solution after purification by commercial materials and biochar materials. E is the spiked recovery rate of 4 pesticides in the solution after purification by commercial materials and biochar materials. F is the spiked recovery rate of 2 pesticides in the solution after purification by commercial materials and different biochar composite materials.

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

[0138] Figure 8 : In the left figure, from left to right: unpurified, delignification + hydrothermal treatment + pyrolysis treatment group, hydrothermal treatment + pyrolysis treatment group, delignification + pyrolysis treatment group, direct pyrolysis group, delignification + hydrothermal treatment group. In the right figure, from left to right: unpurified, delignification + hydrothermal treatment + pyrolysis treatment group, hydrothermal treatment + pyrolysis treatment group, delignification + pyrolysis treatment group, direct pyrolysis group, delignification + hydrothermal treatment group.

[0139] Example 1: Materials and methods

[0140] 1.1 Reagents and instruments

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

[0142] serial number Pesticide name serial number Pesticide name 1 Aldicarb 17 Terbuthion 2 Chlorpheniramine 18 Phorate sulfone 3 Phosphorus 19 Demeton-S 4 Monocrotophos 20 3-Hydroxycarbofuran 5 Ethamisulfuron 21 Ethoprophos 6 Metsulfuron-methyl 22 Fenamiphos sulfone 7 Chlorsulfuron 23 Terbuthion Sulfone 8 Chlormeform 24 Terbufos sulfoxide 9 Sulfate 25 Phorate 10 Coumaphos 26 Phorate sulfoxide 11 Isothioate-methyl 27 Demeton-O 12 Fonfothion 28 Aldicarb sulfone 13 Sulfadone 29 Phosphamide 14 Methamidophos 30 Aldicarb sulfoxide 15 Fenamiphos 31 Carbofuran 16 Fenamiphos sulfoxide

[0143] LC-40A liquid chromatography-mass spectrometer LCMS-8045 was purchased from Shimadzu Corporation, Japan. N5000 spectrophotometer was purchased from Shanghai Youke Instrument Co., Ltd. Universal high-speed pulverizer was purchased from Tianjin Testing Instrument Co., Ltd. Powerful multi-tube vortex mixer was purchased from Beijing Codenos Technology Co., Ltd. Tube furnace was purchased from Beijing Fulaimeng Experimental Equipment Co., Ltd. JJ 500 electronic balance (0.01 g) was purchased from Changshu Shuangjie Testing Instrument Factory. AL104-IC electronic balance (0.0001 g) was purchased from Mettler-Toledo. Eppendorf range: 20-200 μL and 100-1000 μL. MPE series high-throughput parallel evaporator was purchased from RayKol Group Corp., Ltd. (Xiamen, China). The samples were characterized using a surface area tester-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 (effective chlorine content of about 5%) at a ratio of 1 g corn stalk powder to 50 mL NaOCl for 4 h. The NaOCl remaining on the surface of the stalks was washed off with deionized water until no obvious chlorine smell could be smelled.

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

[0147] The dried carbonized precursor was passed through a 40-mesh sieve and placed in a quartz boat. The temperature of the tube furnace was set to 800°C and the heating rate was 5°C / min to carbonize the corn stalk powder. The entire carbonization process was carried out under a N2 atmosphere. The biochar after carbonization 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 the present invention.

[0148] 1.3 Pretreatment of chrysanthemum

[0149] For the pretreatment of chrysanthemum, first crush the chrysanthemum and pass it through a 40-mesh sieve for later use. Take 2.5g of the sieved chrysanthemum powder in a 50mL centrifuge tube, add 1g of sodium chloride and a ceramic homogenizer suitable for 50mL centrifuge tubes, and add 25mL of acetonitrile. Vortex for 5min on a powerful multi-tube vortex mixer at 3000r / min. Centrifuge and take the supernatant. Add 25mL of acetonitrile to the centrifuge tube again, repeat the vortex and centrifuge to take the supernatant, repeat 3 times, and combine the supernatants for concentration on a parallel concentrator. After concentration, add 5mL of acetonitrile to the tube for re-dissolution to 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 on a strong multi-tube vortex mixer, and centrifuge at 13000 r / min for 8 min to obtain the supernatant, which is the chrysanthemum purified liquid.

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

[0153] The chlorophyll test is carried out in accordance with the provisions of the "Spectrophotometric Method for Determination of Chlorophyll Content in Fruits, Vegetables and Their Products" (NY / T1783082-2017), and the lutein test is carried out in accordance with the provisions of the "National Food Safety Standard for Determination of Lutein in Foods" (GB 5009.248-2016). The fat test is carried out in accordance with the provisions of the "National Food Safety Standard for Determination of Fat in Foods" (GB 5009.6-2016).

[0154] 1.6 HPLC-MS / MS conditions

[0155] Pesticides were detected by liquid chromatography mass spectrometer LCMS-8045, and the chromatographic column was Shim-pack GIST-HP C18 (2.1×100mm, 3μm) (Shimadzu Corporation, Japan) (Kyoto). The temperature of the chromatographic column was 40°C, and the injection volume was 5μL. The mobile phase was 0.1% formic acid acetonitrile solution (A) and 0.1% formic acid aqueous solution (B), and the flow rate was 0.3mL / min. The chromatographic conditions were: 30-70% A within 0-12min, maintained for 2min; 70-30% A within 14-14.01min, maintained to 17min. Pesticide analysis was performed in ESI positive ion mode, and the scanning mode was multiple reaction monitoring (MRM); the nebulizer gas flow rate was 3.0L / min, the drying gas flow rate was 10L / min, the heating gas flow rate was 10L / 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 Review

[0157] According to document SANTE / 11312 / 2021v2 (SANTE, 2021), the developed method was validated for its feasibility using the following parameters: linearity, matrix effect, accuracy, precision, limit of detection (LOD) and limit of quantification (LOQ). During the experiment, the instrument was calibrated every day. The linearity of the method was verified by adding 7 levels (1, 5, 10, 50, 100, 200, 300, 500 μg / L) of mixed standard solutions of 31 pesticides to the blank matrix solution of chrysanthemum. The matrix effect of the method was evaluated by comparing the slope ratio of the solvent-based and matrix-matched calibration curves of all target pesticides. The spiked recoveries (n=6) and reproducibility tests of the 31 pesticides at three levels (0.02, 0.1 and 0.2 mg / kg) were tested to verify the accuracy and precision of the method, respectively.

[0158] 1.8 Material pore structure analysis

[0159] The specific surface area and pore structure of biochar materials were analyzed and tested using a fully automatic specific surface area and pore size analyzer. The samples were weighed, placed in a test tube, vacuum dried for 12 hours after pretreatment, and tested under 77K liquid nitrogen after impurities were removed. The specific surface area was calculated using the Brunauer-Emmett-Teller method and the Langmuir method, and the results were processed using the Barret, Joyner and Halenda method (BJH method for short) to better reflect the pore structure of the sample.

[0160] 1.9 Scanning electron microscope structure analysis of materials

[0161] A Zeiss UL TRA55 scanning electron microscope was used. The samples were vacuum dried at 120°C for 12 h before testing. The powder samples were then pasted on a copper column with conductive glue. Gold was sprayed on the surface under a vacuum condition of 10-2 mbar for 60 s. The copper column was then fixed on the sample stage with conductive glue for scanning. The working distance was set to 4.6 mm and the acceleration voltage was set to 3.00 kV.

[0162] Embodiment 2

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

[0164] There are many active ingredients in chrysanthemum, which not only make chrysanthemum a complex matrix in pesticide detection, but also cause certain troubles to the detection instruments. Among all the ingredients, pigments and fats cause the greatest trouble to detection. The inventors found that a large amount of pigments will significantly affect the accuracy of the results and lead to false positives. The presence of fat in the matrix may cause some lipophilic pesticides to be enriched in fat, which in turn affects the quality of the results, the sensitivity of the method, the sample throughput, and the maintenance and downtime of the instrument. 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 by biochar, the color of the purified liquid 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 / 100 g -1 , the fat content in the solution after purification by biochar material is 1.0g·100g -1 This proves that the prepared biochar material has a high ability to purify pigments. Although its ability to purify fat is weaker, it can also remove a small part of fat and can be used for the pretreatment of pesticide residues in chrysanthemums.

[0166] Table 1

[0167]

[0168] In order to determine the specific amount of biochar material, a spike recovery test was conducted. According to the requirements of the Chinese Pharmacopoeia (2020 edition), the pesticide residue detection method should meet the spike recovery rate of each pesticide between 70% and 120%, which can be appropriately relaxed to between 60% and 130% if repeatability is met. The spiked recoveries of fenamiphos (calculated as the sum of fenamiphos, fenamiphos sulfone and fenamiphos 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, terbufos sulfone and terbufos sulfoxide) were within the qualified range of 180-390%, and the spiked recoveries of carbofuran (calculated as the sum of carbofuran and 3-hydroxycarbofuran) and idemeton (calculated as the sum of idemeton-O and idemeton-S) were between 120-260%, which was considered qualified. Specifically, in the process of preparing the chrysanthemum extract, a mixed standard solution prepared by 31 kinds of pesticides was added to the centrifuge tube, and the rest of the operations were consistent with the methods under 1.2 and 1.3.

[0169] The recovery rates of pesticide spikes in the matrix after purification with different amounts of biochar materials are as follows: Figure 2 shown. Figure 2 A is the comparison of the spiked recoveries of 15 pesticides at 6 levels. Figure 2 It can be observed in A that with the increase in the amount of biochar material, the spiked recoveries of six pesticides, including chlorpyrifos, cadusin, coumaphos, chlordimeform, methyl isoflavone, and terbufos, gradually increased to the qualified limit. The reason may be that when the amount of biochar material is small, the purification of interfering substances in the chrysanthemum extract is not thorough enough, which causes masking of trace amounts of pesticides, resulting in the spiked recoveries not meeting the standard. The spiked recoveries of chlorpyrifos and chlorpyrifos decreased to a certain extent with the increase in the amount of biochar material. As for systemic phos, its spiked recovery rate is always lower than the specified range ( Figure 2 C). Figure 2 D is the qualified rate of spiked recovery of 15 pesticides except 6 pesticides such as fenamiphos. It can be seen from the figure that the spiked recovery of 15 pesticides shows a significant upward trend with the increase of biochar material dosage, and the types of pesticides with spiked recovery in the range of 60-120% increase with the increase of biochar material dosage. Considering the pigment removal ability and the qualified rate of spiked recovery, this example finally selected 180mg biochar material for subsequent experiments.

[0170] Embodiment 3

[0171] In order to achieve better purification effect, this example selects commercially available common degreasing purifiers PSA and C18 to be compounded with biochar materials. Figure 3 and Figure 4As shown. From the figure, it can be seen that compared with the unpurified chrysanthemum extract, the pigment removal effect is obvious after purification by the material compounded with biochar material and PSA and / or C18. From the results of the spiked recovery rate, it can also be seen that after the biochar material is compounded with PSA and / or C18, the qualified rate of the spiked recoveries of 31 pesticides is also improved. After the biochar material is compounded with PSA, among the 31 pesticides, only the spiked recoveries of chlorpyrifos, chlorpyrifos, methyl parathion and chlorpyrifos did not meet the spiked recovery rate standard, and the spiked recoveries were 54.21%, 134.18%, 1413.41% and 111.05%, respectively. As Figure 4 As shown in the figure, the results obtained by compounding the biochar material with PSA and C18 are similar to those obtained by compounding the biochar with PSA, but the recovery rate of chlordimeform in the compounding of the biochar material with PSA and C18 is reduced to the qualified line. Finally, 180 mg of biochar + 30 mg of PSA was selected as the adsorbent (purification material) for the QuEChERS method for the recovery rate detection of 31 pesticides in chrysanthemum.

[0172] In order to test whether the prepared biochar material can replace the adsorbent commonly used in the QuEChERS method currently on the market, this example selected GCB, MWCNTs, PSA, and C18 to compare the purification effects of biochar materials. Figure 3 As shown in the figure, it can be seen that compared with the unpurified chrysanthemum extract, the most outstanding pigment purification ability among the commercially available purification materials is GCB (graphitized carbon black), followed by MWCNTs (multi-walled carbon nanotubes), and then PSA, while the purification ability of C18 pigment is poor. Comparing the spiked recovery rates of several groups, at the same addition amount, 16.13%, 16.13%, 16.13%, and 19.36% of the pesticide spiked recoveries did not meet the requirements. From the specific spiked recovery rate values, GCB has a strong adsorption capacity for chlordimeform, resulting in a spiked recovery rate of chlordimeform of only 14.22%; while MWCNTs performed better than GCB. Another commercially available QuEChERS method commonly used adsorption material PSA with strong adsorption capacity has a lower spiked recovery rate for sulfonyl pesticides (including ethametsulfuron, metsulfuron-methyl, and chlorsulfuron) than all test groups. The biochar materials and the purification materials obtained by compounding the biochar materials with PSA can solve the above two problems. The spiked recoveries of chlordimeform and sulfone-methyl pesticides (including ethametsulfuron-methyl, metsulfuron-methyl, and chlorsulfuron-methyl) are all within the acceptable limits.

[0173] Tables 2 and 3 list the linear regression equation, linear range, detection limit, quantification limit and recovery rate of 31 pesticides in chrysanthemum matrix after purification by optimized purification materials (180 mg biochar + 30 mg PSA). The purified chrysanthemum matrix solution was spiked with 0.02 mg / kg, 0.1 mg / kg and 0.2 mg / kg, and the spike recovery rate was determined (n = 6). The results showed that the peak area and concentration had good linearity, and the correlation coefficient (R 2 ) was in the range of 0.9980 to 0.9998. The detection limit (LOD) and minimum detection limit (LOD) of all pesticides were calculated as 3 times and 10 times the signal-to-noise ratio (S / N) of the quantitative ion pair, respectively. The detection limit of the method was 0.00002 to 0.0054 mg / kg, the quantification limit range was 0.00007-0.01638 mg / kg, and the spiked recoveries of 31 pesticides were within the qualified range except for demeton, with relative standard deviations of 0.93 to 21.54%.

[0174] Table 2 Linear regression equation, linear range, LOD (mg / kg), LOQ (mg / kg), recovery, precision and relative standard deviation (RSD) of 15 pesticides in chrysanthemum matrix (n=6)

[0175]

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

[0177]

[0178] Figure 5 This is a comparison of the matrix effects of 31 pesticides in chrysanthemum extracts purified by optimized purification materials. As can be seen from the figure, all 31 pesticides have matrix effects, and 19.35% of the 31 pesticides have matrix effects within ±20%, which are basically not affected by matrix effects. Other pesticides have medium and high matrix effects, which affect the accuracy of pesticide quantification. Therefore, chrysanthemum matrix extracts were used to prepare standard curves during the experiment to accurately quantify 31 pesticides.

[0179] Embodiment 4

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

[0181] Figure 6The following are scanning electron microscope images of biochar materials before and after adsorption. As a whole, it can be seen that the biochar material presents a three-dimensional porous structure. Compared with graphitized carbon black with a highly ordered structure, the structure of the biochar material is more disordered, which may be the reason why the biochar material has no retention effect on many pesticides but has a retention effect on pigments. After adsorption, the structure of the biochar material collapsed to a certain extent, and the pores changed from nearly circular to crescent-shaped. After adsorption, the pores of the biochar material became smaller, the pore edge boundaries were no longer clear, and were covered with more fine particles. After magnification, it can be observed that the surface of the biochar material before adsorption is relatively flat, while the surface three-dimensionality of the biochar material after adsorption increases, and more regular spherical particles can be observed.

[0182] In order to explore the pore structure of biochar materials, the specific surface area and pore structure of biochar materials were analyzed and tested using a fully automatic specific surface area and pore size analyzer. Figure 7 As shown in the figure, as the pressure increases, the adsorption amount increases rapidly, and the adsorption amount reaches saturation after reaching a certain pressure. This phenomenon is generally called Type I adsorption isotherm, which is mainly caused by the fact that the adsorption amount of the narrow micropores in the material quickly reaches saturation at a lower pressure. Pore size analysis can also confirm this. It can be seen in the figure that the pore size of the biochar material is <5nm, indicating that the biochar material prepared by the present invention is microporous biochar. The specific surface area of ​​the obtained biochar material was measured to be 351.43m 2 / g.

[0183] Embodiment 5

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

[0185] 5.1 Screening of biomass materials

[0186] The purchased corn stalks, balsa sawdust, and loofah were processed as follows:

[0187] Corn stalks: Dry the corn stalks in an oven at 60°C overnight, cut them into small pieces with scissors, grind them with a grinder, pass them through a 40-mesh sieve and store them in a sealed bag for later use.

[0188] Balsa sawdust: Dry the balsa sawdust in an oven at 60°C overnight, seal and set aside.

[0189] Sponge gourd pulp: Wash with deionized water to remove the remaining sponge gourd pulp and seeds, and then dry in an oven at 60°C. After drying, cut into small pieces with scissors, further crush with a grinder, and seal for later use.

[0190] Preparation of biochar materials based on corn straw, basa sawdust and loofah

[0191] In order to evaluate the adsorption performance of the three biomass materials, the scheme of Example 1 was adopted to prepare biochar materials using the three biomass materials as raw materials, including: the biomass materials were treated with sodium hypochlorite, then subjected to hydrothermal treatment in a reactor, and then dried and carbonized in a tubular furnace to finally obtain the biochar materials.

[0192] The purification effects of the biochar materials prepared based on the three biomass materials on the pigments in the honeysuckle extract are shown in Table 4 (30 mg of biochar material, 2.5 g of honeysuckle, and the preparation method of the honeysuckle extract is shown below). The results in Table 4 show that the biochar materials prepared based on the three biomass materials can all play a directional adsorption role on the pigments in the honeysuckle extract, among which corn stalks have the best pigment purification effect.

[0193] Table 4

[0194]

[0195] Among them, the preparation method of the medicinal crop extract (pretreatment of medicinal crops) is as follows: First, the medicinal crops (such as honeysuckle, mulberry leaves) are crushed and passed through a 40-mesh sieve for later use. Take 2.5g of the sieved medicinal crop powder in a 50mL centrifuge tube, add 1g of sodium chloride and a ceramic homogenizer suitable for a 50mL centrifuge tube, and add 25mL of acetonitrile. Vortex for 5min on a powerful multi-tube vortex mixer at 3000r / min. Centrifuge and take the supernatant. Add 25mL of acetonitrile to the centrifuge tube again, repeat the vortex and centrifuge to take the supernatant, repeat 3 times, and combine the supernatants for concentration on a parallel concentrator. After concentration, add 5mL of acetonitrile to the tube for re-dissolution to obtain the medicinal crop extract.

[0196] 5.2 Pretreatment method optimization

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

[0198] (1) Sodium hydroxide + sodium sulfite: Add 250 mL of sodium hydroxide (2.5 mol / L) and sodium sulfite (0.4 mol / L) to a beaker. Heat the solution to boiling, then add corn stalk powder. Keep the solution at a slight boiling state for 2 hours, filter out the corn stalk powder, rinse it with a large amount of deionized water, and dry it in an oven at 60°C.

[0199] (2) Hydrogen peroxide: Add hydrogen peroxide (2.5 mol / L) to corn stalk powder at a ratio of 1 g powder to 50 mL, disperse, heat to a slightly boiling state and maintain for 2 h. After 2 h, filter and wash, and finally dry in an oven at 60 °C.

[0200] (3) Sodium hypochlorite: Sodium hypochlorite (effective chlorine concentration ≥ 5%) was added to corn stalk powder at a ratio of 1 g powder to 50 mL, and the mixture was allowed to stand for 4 h after dispersion. After 4 h, the corn stalk powder was filtered and washed, and finally dried in an oven at 60°C.

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

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

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

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

[0205] Table 5-1

[0206]

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

[0208] Table 5-2

[0209]

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

[0211] The above results show that not all delignification methods are suitable for pretreatment of biomass materials. The reason for this result may be that the principle of removing lignin by sodium hydroxide + sodium sulfite is to dissolve part of the lignin, while the principle of removing lignin by hydrogen peroxide and sodium hypochlorite is to oxidize lignin and thus destroy the lignin structure. In the process of destroying the lignin structure, the specific surface area of ​​the biochar material may be increased again, making its ability to purify pigments better than that of the sodium hydroxide + sodium sulfite group. The pigment purification ability of the biochar materials treated with hydrogen peroxide and sodium hypochlorite in honeysuckle is similar to that in mulberry leaves. After considering the price, risk factor, and availability of hydrogen peroxide and sodium hypochlorite, sodium hypochlorite was finally selected for subsequent experiments.

[0212] 5.3 Carbonization process optimization

[0213] According to whether delignification, hydrothermal treatment, and pyrolysis carbonization were performed, they were divided into 5 groups, as follows:

[0214] 1. Delignification + hydrothermal + pyrolysis

[0215] 2 Direct pyrolysis

[0216] 3. Hydrothermal + Pyrolysis

[0217] 4 Delignification + Hydrothermal

[0218] 5. Delignification + Pyrolysis

[0219] The hydrothermal treatment steps specifically include: taking an appropriate amount of pretreated corn stalk powder and a small amount of water and adding them to the polytetrafluoroethylene lining of the laboratory reactor (the capacity shall not exceed 2 / 3 of the reactor lining capacity). After closing the reactor and tightening the reactor screw, move the reactor as a whole into the oven. Set the oven temperature to 220°C for 4 hours, and take out the reactor after the reactor is naturally cooled in the oven. Open the reactor lining and filter the contents. After washing with deionized water, dry it at 60°C in a vacuum drying oven, and pass it through a 40-mesh sieve to obtain a carbonized precursor.

[0220] The steps of pyrolysis carbonization specifically include: after opening the N2 gas cylinder connected to the tube furnace, purge the tube furnace tube for about 5 minutes, take an appropriate amount of carbonization precursor into the quartz boat (the amount of carbonization each time should be determined according to the surface area of ​​the quartz boat). After placing the carbonization precursor together with the quartz boat in the center of the tube furnace tube, install the tube furnace flange and place the tube furnace exhaust pipe in the aqueous solution, set the tube furnace temperature to 800°C, and the heating rate to 5°C / min. After the carbonization is completed, turn off the power of the tube furnace and keep the nitrogen purge for a while. After the tube furnace cools to room temperature, take out the quartz boat.

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

[0222] 60 mg of biochar materials prepared by the above five carbonization processes were taken respectively to test the pigment adsorption effect in honeysuckle extract (among which, a. hydrothermal + pyrolysis, b. delignification + pyrolysis, c. delignification + hydrothermal, d. delignification + hydrothermal + pyrolysis, e. direct pyrolysis). The results are shown in Table 6-1 and Figure 8 The test results of the pigment adsorption effect in mulberry leaf extract are shown in Table 6-2 and Figure 8 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 plants (such as chrysanthemum, honeysuckle, mulberry leaves, etc.).

[0223] The purification effects of honeysuckle and mulberry leaf extracts were ranked in a consistent order: delignification + hydrothermal treatment + pyrolysis treatment group > hydrothermal treatment + pyrolysis treatment group > delignification + pyrolysis treatment group > direct pyrolysis group > delignification + hydrothermal treatment group. From the results, it can be seen that delignification, hydrothermal treatment and pyrolysis treatment have a synergistic effect, and the absence of any process will significantly affect the adsorption performance of the final product.

[0224] The contribution of hydrothermal treatment to the adsorption performance of biochar is higher than that of delignification treatment, which may be related to the significant increase of oxygen-containing functional groups on the surface of corn straw during hydrothermal treatment. The purified liquid of the delignification + hydrothermal treatment group showed obvious color difference abnormality, which may be attributed to the high-pressure and high-temperature hydrothermal environment that aggravated the dissolution of lignin, resulting in the color development effect of dissolved lignin under the action of organic solvents. Based on the above experimental results, the combination of delignification + hydrothermal treatment + pyrolysis treatment of corn straw was finally selected to prepare biochar materials for purification of honeysuckle and mulberry leaf extracts.

[0225] Table 6-1: Comparison of the purification effect of pigments in honeysuckle extract

[0226]

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

[0228]

[0229] 5.4 Carbonization temperature optimization

[0230] Based on the optimized carbonization process in 5.3, the carbonization temperature was optimized, that is, pyrolysis was performed at five temperatures: 500, 600, 700, 800, and 900°C. The optimal carbonization temperature was evaluated based on the purification effect of each group of materials on chlorophyll and lutein in honeysuckle.

[0231] 30 mg of biochar materials obtained by pyrolysis of carbonized precursors at 500, 600, 700, 800, and 900 °C were accurately weighed to compare the purification effects of chlorophyll and lutein in honeysuckle extract, and the comparison results are shown in Table 7. The results show that maintaining the carbonization temperature at 500-900 °C can achieve better pigment purification effects.

[0232] Table 7

[0233]

[0234] Note: The reason why the results of the blank group honeysuckle extract in Table 7 are different from those in Table 4 and Table 5-1 is that the honeysuckle extract was diluted 6 times in this experiment.

[0235] 5.5 Functionalization method optimization

[0236] In order to further optimize the adsorption performance of biochar materials, the biochar materials were acid-functionalized. Specifically: a small amount of biochar materials and the prepared acid solution were taken in a stoppered conical flask, mixed at a ratio of 250 mg biochar: 250 mL sodium acid solution, and left to stand overnight. The next day, the biochar materials were washed with deionized water until the pH value of the effluent was neutral. The acid-functionalized biochar materials were dried in a vacuum oven. The experimental groups were 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] 7Hydrochloric 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 means that the concentrations of hydrochloric acid and sulfuric acid are approximately 0.5 mol / L respectively.

[0245] The results of the acid-functionalized biochar material (30 mg) on ​​the pigment purification effect (honeysuckle) are shown in Table 8. The acid-functionalized treatment with hydrochloric acid, sulfuric acid, and nitric acid improved the purification effect of the biochar material on the pigment of the honeysuckle extract, among which the biochar material treated with hydrochloric acid and / or nitric acid had a better purification effect on the pigment.

[0246] Table 8

[0247]

[0248] The results of the acid-functionalized biochar material (30 mg) on ​​the pigment purification effect (mulberry leaf) are shown in Table 9. The acid-functionalized treatment with hydrochloric acid, sulfuric acid, and nitric acid improved the purification effect of the biochar material on the pigment of the mulberry leaf extract, among which the biochar material treated with sulfuric acid + nitric acid had a better purification effect on the pigment. After comprehensive evaluation, nitric acid was selected to perform the acid-functionalized treatment on the biochar.

[0249] Table 9

[0250]

[0251] The infrared spectral characteristics of biochar materials after nitric acid functionalization treatment are as follows Fig. 9 In the original biochar sample (the difference between the original biochar sample and the biochar material after nitric acid functionalization treatment is that the original biochar sample is not treated with nitric acid functionalization), 3398cm -1 The weak absorption peaks near 1557cm are attributed to the OH stretching vibration mode of alcohol, phenol and adsorbed water, and may also include the NH stretching vibration mode; -1 The broad peak shape near 1092cm is mainly located in the characteristic absorption region of aromatics, which is related to the C=C stretching vibration mode of the benzene ring. The peak is relatively broad and may also contain part of the carbonyl C=O stretching vibration mode. -1 The strong peaks near 799 cm are mainly attributed to the stretching vibration modes of Si-O and CO. -1 The absorption peaks near are related to the CH stretching vibration mode outside the aromatic ring plane 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, CO and other groups. These functional groups can form stable combinations with other small molecules through physical and chemical reactions, thereby effectively removing these components through different adsorption mechanisms. Of course, the pore size distribution and specific surface area of ​​biochar will also affect the diffusion and adsorption of small molecule compounds in biochar. At 1092cm -1 and 799cm -1 The absorption peak intensity at is extremely high, indicating that the content of organic groups on the surface of the biochar material is low, which may be caused by the high temperature of biochar preparation.

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

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

[0254] From the adsorption isotherms of the biochar material after nitric acid functionalization treatment, it can be analyzed that the adsorption and desorption of the biochar material belong to type IV (a) adsorption isotherms, and the adsorption isotherms all have H3 type hysteresis loops, which are often produced in narrow mesoporous materials. As shown in Table 10, after BET fitting, the specific surface area of ​​the biochar material after nitric acid functionalization treatment is 249.52 m 2 ·g -1 The reason for this phenomenon may be that part of the pore structure was oxidized and destroyed during the nitric acid impregnation process.

[0255] Table 10

[0256]

[0257] The embodiments of the present invention are described above in conjunction with the accompanying drawings, but the present invention is not limited to the above-mentioned specific implementation modes, which are merely illustrative rather than restrictive. Under the guidance of the present invention, ordinary technicians in this field can also make many forms without departing from the scope of protection of the present invention and the claims, all of which are within the protection of the present invention.

Claims

1. A method for preparing a biochar material, characterized in that: The following steps are involved: S101: adding biomass material to the first solution for pretreatment to obtain a first mixed solution; S102 placing the biomass material in the first mixed solution in water and performing a hydrothermal reaction to obtain a first precursor; S103 vacuum-drying the first precursor to obtain a second precursor; S104 carbonizing the second precursor to obtain a first material; S105: soaking the first material in a second solution for a second period of time, and obtaining the biochar material after vacuum drying; Wherein, the first solution includes hydrogen peroxide solution or hypochlorite solution; the temperature of the hydrothermal reaction in step S102 includes 200-240°C, and the time of the hydrothermal reaction includes 4-6 hours; the set temperature of the carbonization in step S104 includes 500-900°C, and the heating rate of the carbonization includes 5-10°C / min, and the second solution includes hydrochloric acid, nitric acid or a combination thereof.

2. The method according to claim 1, characterized in that The biomass material includes straw, wood chips or loofah.

3. The method according to claim 1, characterized in that When the first solution is a hypochlorite solution, the pretreatment method includes: soaking the biomass material in the hypochlorite solution for a first period of time to obtain a first mixed solution.

4. The method according to claim 3, characterized in that The ratio of the straw powder to the hypochlorite solution includes 1.0 g: 40-60 mL.

5. The biochar material prepared by the preparation method according to any one of claims 1 to 4.

6. The use of the biochar material according to claim 5 in the preparation of a QuEChERS-based pesticide residue pretreatment reagent, characterized in that: The pesticide residue pre-treatment reagent is used for directional adsorption of pigments in samples, and the samples include medicinal crop samples.

7. The use according to claim 6, characterized in that The samples include chrysanthemum samples, honeysuckle samples or mulberry leaf samples.

8. The use according to claim 7, characterized in that The pesticide residue pre-treatment reagent also includes an adsorption material.

9. The use of the biochar material according to claim 5 in preparing a sample pretreatment kit based on QuEChERS, characterized in that: The sample pretreatment kit comprises a pesticide residue pretreatment reagent, the pesticide residue pretreatment reagent comprises the biochar material, and the pesticide residue pretreatment reagent is configured to be used for pretreatment and purification of a medicinal crop sample.

10. The use according to claim 9, characterized in that The pesticide residue pretreatment reagent is configured to be used for pretreatment and purification of a honeysuckle sample or a mulberry leaf sample.

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