A method for the pre-treatment of dioxin in a fly ash sample

Abstract

The application discloses a dioxin pretreatment method in fly ash samples, and belongs to the technical field of environmental organic pollutant analysis and detection. The pretreatment method comprises the following steps: (1) fly ash sample pretreatment: drying, grinding and acidizing the fly ash sample to make the dioxin more easily extracted; (2) fly ash sample extraction: filtering the product obtained in the step (1), performing Soxhlet extraction on the solid phase, performing liquid-liquid extraction on the liquid phase, and then combining and rotary-evaporating and concentrating; (3) fly ash sample extraction liquid purification: purifying the fly ash sample extraction liquid obtained in the step (2), including sequentially passing the extraction liquid through a purification column and a purification column to obtain an analysis sample. The method can remove the interference of polychlorinated biphenyl and polybrominated biphenyl ether on the detection of dioxin, is simple in process, easy to operate, greatly reduced in cost, high in detection accuracy and high in recovery rate.

Description

Technical Field

[0001] This application relates to a method for pretreatment of dioxins in fly ash samples, belonging to the field of environmental organic pollutant analysis and detection technology. Background Technology

[0002] Dioxins, also known as dioxins, are colorless, odorless, teratogenic, and carcinogenic lipid-soluble substances. Dioxins are actually a collective term for dioxins, which are aromatic organic compounds composed of one or two oxygen atoms linked to two chlorine atoms substituted into a benzene ring. Dioxins exhibit reproductive toxicity, neurotoxicity, endocrine toxicity, and immunotoxicity. Another characteristic of dioxin toxicity is that, as lipid-soluble compounds, they easily accumulate in the adipose tissue of organisms, are not easily degraded or excreted, and can continuously accumulate in the bodies of humans and animals to reach high concentrations, with a long latency period before obvious symptoms appear.

[0003] Dioxins are produced in the fly ash generated during the incineration of municipal solid waste, industrial waste, and electronic waste. Fly ash has a complex composition, and structurally similar polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) coexist with dioxins. When detecting dioxins in fly ash samples, PCBs and PBDEs act as interfering factors. Furthermore, while there are increasingly more methods for detecting dioxins, sample pretreatment and purification are necessary regardless of the method used. Traditional purification procedures are complex, especially involving the separation of PCBs and PBDEs, which further complicates the pretreatment process. Fully automated purification systems using disposable purification columns are expensive, resulting in high detection costs.

[0004] Chinese Patent CN 105510505 A, "Method for Determining Dioxin Content in Tea and Rice Samples," describes a sample pretreatment process involving rapid solvent extraction, silica gel column purification, activated carbon column purification, and nitrogen blowing concentration. The innovation lies in effectively reducing sample extraction and purification time, decreasing solvent usage, and improving pretreatment efficiency. However, the relatively simple silica gel column purification method cannot maximally remove organic contaminants from the test solution, especially non-polar impurities such as polycyclic aromatic hydrocarbons (PAHs), which significantly interfere with subsequent dioxin detection. Furthermore, this pretreatment method struggles to separate polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), further interfering with dioxin detection results. Therefore, it is not suitable for fly ash sample detection. Summary of the Invention

[0005] To address the aforementioned issues, a pretreatment method for dioxins in fly ash samples is provided. This method can remove the interference of polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) on the detection of dioxins. The process is simple, easy to operate, and significantly reduces costs, while also achieving high detection accuracy and high recovery rate.

[0006] According to one aspect of this application, a method for pretreating dioxins in fly ash samples is provided, comprising the following steps:

[0007] (1) Pretreatment of fly ash samples: The fly ash samples are dried, ground and acidified to make dioxins easier to extract;

[0008] (2) Extraction of fly ash samples: The product obtained in step (1) is filtered, subjected to Soxhlet extraction in solid phase, and liquid-liquid extraction in liquid phase, and then combined and concentrated by rotary evaporation.

[0009] (3) Purification of fly ash sample extract: The fly ash sample extract obtained in step (2) is purified by passing the extract through a purification column and a purification column in sequence to obtain the analytical sample.

[0010] Specifically, acidification involves soaking the fly ash sample in a 2-3 mol / L hydrochloric acid solution for 4-5 hours, with a mass ratio of fly ash sample to hydrochloric acid solution of 1:10-20.

[0011] Specifically, this application pre-treats fly ash samples by performing steps such as drying, grinding, and acidification to remove the interference of a large amount of metal salts and carbonaceous substances covering the surface of the fly ash samples, so as to ensure that the organic matter in the fly ash samples can be completely extracted.

[0012] Optionally, the purification column includes, from top to bottom, a neutral silica gel layer, an activated carbon layer, an alkaline alumina layer, a Florisil layer, and a modified graphitized carbon black layer; the purification column includes, from top to bottom, a glass fiber layer, a silica gel sulfate layer, and an anhydrous sodium sulfate layer; the purification column and the purification column are connected in series.

[0013] Specifically, it includes a purification column and a purification column, and makes specific limitations on the composition and arrangement order of the purification column and the purification column. The purification column is set up to separate and adsorb impurities in dioxins, and the purification column is set up to adsorb and separate polychlorinated biphenyls and polybrominated diphenyl ethers in fly ash, so as to eliminate their interference with the dioxin detection results and improve the accuracy of the detection results.

[0014] Optionally, the height ratio of the purification column to the purification column is (5-3):(2-3).

[0015] This application specifies the height ratio of the purification column and the purification column to ensure the effectiveness of purification and thus improve the accuracy of the detection results.

[0016] Optionally, in the purification column, the mass ratio of the neutral silica gel layer, activated carbon layer, alkaline alumina layer, Florisil layer, and modified graphitized carbon black layer is (2-3):1:(3-5):(2-4):(2-3).

[0017] Specifically, this application specifies the composition of each packing material in the purification column and the mass ratio of the neutral silica gel layer, activated carbon layer, basic alumina layer, Florisil layer, and modified graphitized carbon black layer in the purification column, in order to maximize the separation and adsorption of impurities in dioxins, such as phenolic substances, highly polar compounds, and polycyclic aromatic hydrocarbons, to ensure the purity of the sample, reduce the detection limit, and ensure the accuracy of the detection.

[0018] Optionally, in the purification column, the height ratio of the glass fiber layer, the silica gel sulfate layer, and the anhydrous sodium sulfate layer is (2-4):(7-10):1.

[0019] Specifically, this application specifies the composition and height ratio of the purification column to adsorb and separate polychlorinated biphenyls and polybrominated diphenyl ethers in fly ash, eliminate their interference with dioxin detection results, and improve the accuracy of detection results.

[0020] Optionally, the modified graphitized carbon black in the modified graphitized carbon black layer is prepared by modifying graphitized carbon black with alkyl chlorosilanes.

[0021] Specifically, the modified graphitized carbon black layer in this application is modified by using alkylchlorosilanes to introduce long-chain alkyl groups on the surface of the graphitized carbon black, thereby increasing the hydrophobicity of the graphitized carbon black surface, thereby enhancing the van der Waals forces and π-π interactions between it and non-polar impurities such as polycyclic aromatic hydrocarbons, and thus improving its adsorption capacity and adsorption efficiency for non-polar impurities such as polycyclic aromatic hydrocarbons.

[0022] Optionally, the method for preparing the modified graphitized carbon black includes the following steps:

[0023] S1 disperses graphitized carbon black in anhydrous ethanol;

[0024] S2 is added to alkyl chlorosilane, stirred until homogeneous, and then heated.

[0025] After S3 is cooled, it is filtered, washed, and dried to obtain modified graphitized carbon black.

[0026] Optionally, the alkylchlorosilane includes octadecyltrichlorosilane or dodecyltrichlorosilane; the mass ratio of the alkylchlorosilane to graphitized carbon black is (1.5-2.5):1.

[0027] Optionally, the heating treatment in S2 is performed at a temperature of 60–80°C for 1–2 hours.

[0028] Optionally, the glass fiber layer further includes activated carbon and titanium dioxide, wherein the mass ratio of glass fiber, activated carbon and titanium dioxide is (2-4):(1-3):(0.5-1).

[0029] Specifically, the glass fiber layer of this application also includes activated carbon and titanium dioxide, and the mass ratio of the three is limited to improve the adsorption capacity.

[0030] The beneficial effects of this application include, but are not limited to:

[0031] 1. The dioxin pretreatment method for fly ash samples according to this application can remove the interference of polychlorinated biphenyls and polybrominated diphenyl ethers on the detection of dioxins. The process is simple, easy to operate and the cost is greatly reduced. It also has high detection accuracy and high recovery rate.

[0032] 2. According to the dioxin pretreatment method for fly ash samples of this application, a pretreatment step is set up to destroy the complex matrix in fly ash and dissolve metal salts to remove the interference of a large amount of metal salts and carbonaceous matter covering the surface of fly ash samples, thereby improving the extraction efficiency of dioxins in fly ash; a purification column is used to separate and adsorb impurities in dioxins, and a purification column is used to adsorb and separate polychlorinated biphenyls and polybrominated diphenyl ethers in fly ash, thereby eliminating their interference with dioxin detection results and improving the accuracy of detection results.

[0033] 3. According to the dioxin pretreatment method in fly ash samples of this application, specific limitations are made on the composition, setting order, mass ratio and height ratio of the purification column and the purification column to ensure the effect of impurity adsorption and separation, and to achieve the technical effect of high detection accuracy and high recovery rate.

[0034] 4. According to the dioxin pretreatment method in fly ash samples of this application, by setting a modified graphitized carbon black layer and specifying the preparation method of the modified graphitized carbon black, long-chain alkyl groups are introduced on the surface of the graphitized carbon black to increase the hydrophobicity of the graphitized carbon black surface, thereby enhancing the van der Waals forces and π-π interactions between it and non-polar impurities such as polycyclic aromatic hydrocarbons, and thus improving its adsorption capacity and adsorption efficiency for non-polar impurities such as polycyclic aromatic hydrocarbons. Detailed Implementation

[0035] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0036] Unless otherwise specified, the raw materials used in the embodiments and comparative examples of this application were all purchased commercially.

[0037] Unless otherwise specified, the methods used in the embodiments and comparative examples of this application are conventional methods in the prior art.

[0038] Example 1

[0039] A method for pretreatment of dioxins in fly ash samples:

[0040] (1) Pretreatment of fly ash samples: The fly ash samples were dried, ground and acidified to make dioxins easier to extract; the acidification was carried out by soaking the fly ash samples in 2 mol / L hydrochloric acid solution for 4 h, and the mass ratio of fly ash samples to hydrochloric acid solution was 1:10.

[0041] (2) Extraction of fly ash samples: The product obtained in step (1) is filtered, and the solid phase is subjected to Soxhlet extraction, and the liquid phase is subjected to liquid-liquid extraction. The samples are then combined and concentrated by rotary evaporation. The Soxhlet extraction uses rapid solvent extraction with toluene as the solvent, and the liquid-liquid extraction uses dichloromethane as the solvent.

[0042] (3) Purification of fly ash sample extract: The fly ash sample extract obtained in step (2) is purified by passing the extract through a purification column and a purification column in sequence to obtain the analytical sample; wherein, the purification column includes a neutral silica gel layer, an activated carbon layer, an alkaline alumina layer, a Florisil layer, and a modified graphitized carbon black layer arranged from top to bottom, and the mass ratio of the neutral silica gel layer, activated carbon layer, alkaline alumina layer, Florisil layer, and modified graphitized carbon black layer is 2:1:3:2:2; the purification column includes a glass fiber layer, a silica sulfate layer, and an anhydrous sodium sulfate layer arranged from top to bottom, and the height ratio of the glass fiber layer, silica sulfate layer, and anhydrous sodium sulfate layer is 2:7:1; the height ratio of the purification column to the purification column is 5:2.

[0043] Preparation method of modified graphitized carbon black:

[0044] S1 disperses graphitized carbon black in anhydrous ethanol;

[0045] S2 is added with octadecyltrichlorosilane, the mass ratio of octadecyltrichlorosilane to graphitized carbon black is 1.5:1, stirred evenly, and then heated at 60℃ for 1 hour.

[0046] After S3 is cooled, it is filtered, washed, and dried to obtain modified graphitized carbon black.

[0047] Example 2

[0048] A method for pretreatment of dioxins in fly ash samples:

[0049] (1) Pretreatment of fly ash samples: The fly ash samples were dried, ground and acidified to make dioxins easier to extract; the acidification was carried out by soaking the fly ash samples in 3 mol / L hydrochloric acid solution for 4 h, and the mass ratio of fly ash samples to hydrochloric acid solution was 1:20.

[0050] (2) Extraction of fly ash samples: The product obtained in step (1) is filtered, and the solid phase is subjected to Soxhlet extraction, and the liquid phase is subjected to liquid-liquid extraction. The samples are then combined and concentrated by rotary evaporation. The Soxhlet extraction uses rapid solvent extraction with toluene as the solvent, and the liquid-liquid extraction uses dichloromethane as the solvent.

[0051] (3) Purification of fly ash sample extract: The fly ash sample extract obtained in step (2) is purified, including the extract passing through a purification column and a purification column in sequence to obtain the analytical sample; wherein, the purification column includes a neutral silica gel layer, an activated carbon layer, an alkaline alumina layer, a Florisil layer, and a modified graphitized carbon black layer arranged from top to bottom, and the mass ratio of the neutral silica gel layer, activated carbon layer, alkaline alumina layer, Florisil layer, and modified graphitized carbon black layer is 3:1:5:4:3; the purification column includes a glass fiber layer, a silica sulfate layer, and an anhydrous sodium sulfate layer arranged from top to bottom, and the height ratio of the glass fiber layer, silica sulfate layer, and anhydrous sodium sulfate layer is 4:10:1; the height ratio of the purification column to the purification column is 1:1;

[0052] Preparation method of modified graphitized carbon black:

[0053] S1 disperses graphitized carbon black in anhydrous ethanol;

[0054] S2 is added with octadecyltrichlorosilane, the mass ratio of octadecyltrichlorosilane to graphitized carbon black is 2.5:1, stirred evenly, and then heated at 80℃ for 2 hours.

[0055] After S3 is cooled, it is filtered, washed, and dried to obtain modified graphitized carbon black.

[0056] Example 3

[0057] A method for pretreatment of dioxins in fly ash samples:

[0058] (1) Pretreatment of fly ash samples: The fly ash samples were dried, ground and acidified to make dioxins easier to extract; the acidification was carried out by soaking the fly ash samples in 2.5 mol / L hydrochloric acid solution for 4 hours, and the mass ratio of fly ash samples to hydrochloric acid solution was 1:15.

[0059] (2) Extraction of fly ash samples: The product obtained in step (1) is filtered, and the solid phase is subjected to Soxhlet extraction, and the liquid phase is subjected to liquid-liquid extraction. The samples are then combined and concentrated by rotary evaporation. The Soxhlet extraction uses rapid solvent extraction with toluene as the solvent, and the liquid-liquid extraction uses dichloromethane as the solvent.

[0060] (3) Purification of fly ash sample extract: The fly ash sample extract obtained in step (2) is purified by passing the extract through a purification column and a purification column in sequence to obtain the analytical sample; wherein, the purification column includes a neutral silica gel layer, an activated carbon layer, an alkaline alumina layer, a Florisil layer, and a modified graphitized carbon black layer arranged from top to bottom, and the mass ratio of the neutral silica gel layer, activated carbon layer, alkaline alumina layer, Florisil layer, and modified graphitized carbon black layer is 2:1:3:4:3; the purification column includes a glass fiber layer, a silica sulfate layer, and an anhydrous sodium sulfate layer arranged from top to bottom, and the height ratio of the glass fiber layer, silica sulfate layer, and anhydrous sodium sulfate layer is 3:8:1; the height ratio of the purification column to the purification column is 5:3.

[0061] Preparation method of modified graphitized carbon black:

[0062] S1 disperses graphitized carbon black in anhydrous ethanol;

[0063] S2 is added with octadecyltrichlorosilane, the mass ratio of octadecyltrichlorosilane to graphitized carbon black is 2:1, stirred evenly, and then heated at 70℃ for 2 hours.

[0064] After S3 is cooled, it is filtered, washed, and dried to obtain modified graphitized carbon black.

[0065] Example 4

[0066] A method for pretreatment of dioxins in fly ash samples:

[0067] (1) Pretreatment of fly ash samples: The fly ash samples were dried, ground and acidified to make dioxins easier to extract; the acidification was carried out by soaking the fly ash samples in 2.5 mol / L hydrochloric acid solution for 4 hours, and the mass ratio of fly ash samples to hydrochloric acid solution was 1:15.

[0068] (2) Extraction of fly ash samples: The product obtained in step (1) is filtered, and the solid phase is subjected to Soxhlet extraction, and the liquid phase is subjected to liquid-liquid extraction. The samples are then combined and concentrated by rotary evaporation. The Soxhlet extraction uses rapid solvent extraction with toluene as the solvent, and the liquid-liquid extraction uses dichloromethane as the solvent.

[0069] (3) Purification of fly ash sample extract: The fly ash sample extract obtained in step (2) is purified, including the extract passing through a purification column and a purification column in sequence to obtain the analytical sample; wherein, the purification column includes a neutral silica gel layer, an activated carbon layer, an alkaline alumina layer, a Florisil layer, and a modified graphitized carbon black layer arranged from top to bottom, and the mass ratio of the neutral silica gel layer, activated carbon layer, alkaline alumina layer, Florisil layer, and modified graphitized carbon black layer is 2:1:3:4:3; the purification column includes a glass fiber layer, a silica sulfate layer, and an anhydrous sodium sulfate layer arranged from top to bottom, and the height ratio of the glass fiber layer, silica sulfate layer, and anhydrous sodium sulfate layer is 3:8:1; the height ratio of the purification column to the purification column is 5:3; the glass fiber layer also includes activated carbon and titanium dioxide, and the mass ratio of glass fiber, activated carbon, and titanium dioxide is 2:1:0.5;

[0070] Preparation method of modified graphitized carbon black:

[0071] S1 disperses graphitized carbon black in anhydrous ethanol;

[0072] S2 is added with octadecyltrichlorosilane, the mass ratio of octadecyltrichlorosilane to graphitized carbon black is 2:1, stirred evenly, and then heated at 70℃ for 2 hours.

[0073] After S3 is cooled, it is filtered, washed, and dried to obtain modified graphitized carbon black.

[0074] Example 5

[0075] A method for pretreatment of dioxins in fly ash samples:

[0076] (1) Pretreatment of fly ash samples: The fly ash samples were dried, ground and acidified to make dioxins easier to extract; the acidification was carried out by soaking the fly ash samples in 2.5 mol / L hydrochloric acid solution for 4 hours, and the mass ratio of fly ash samples to hydrochloric acid solution was 1:15.

[0077] (2) Extraction of fly ash samples: The product obtained in step (1) is filtered, and the solid phase is subjected to Soxhlet extraction, and the liquid phase is subjected to liquid-liquid extraction. The samples are then combined and concentrated by rotary evaporation. The Soxhlet extraction uses rapid solvent extraction with toluene as the solvent, and the liquid-liquid extraction uses dichloromethane as the solvent.

[0078] (3) Purification of fly ash sample extract: The fly ash sample extract obtained in step (2) is purified, including the extract passing through a purification column and a purification column in sequence to obtain the analytical sample; wherein, the purification column includes a neutral silica gel layer, an activated carbon layer, an alkaline alumina layer, a Florisil layer, and a modified graphitized carbon black layer arranged from top to bottom, and the mass ratio of the neutral silica gel layer, activated carbon layer, alkaline alumina layer, Florisil layer, and modified graphitized carbon black layer is 2:1:3:4:3; the purification column includes a glass fiber layer, a silica sulfate layer, and an anhydrous sodium sulfate layer arranged from top to bottom, and the height ratio of the glass fiber layer, silica sulfate layer, and anhydrous sodium sulfate layer is 3:8:1; the height ratio of the purification column to the purification column is 5:3; the glass fiber layer also includes activated carbon and titanium dioxide, and the mass ratio of glass fiber, activated carbon, and titanium dioxide is 4:3:1;

[0079] Preparation method of modified graphitized carbon black:

[0080] S1 disperses graphitized carbon black in anhydrous ethanol;

[0081] S2 is added with octadecyltrichlorosilane, and the mass ratio of dodecyltrichlorosilane to graphitized carbon black is 2:1. The mixture is stirred evenly and then heated at 70°C for 2 hours.

[0082] After S3 is cooled, it is filtered, washed, and dried to obtain modified graphitized carbon black.

[0083] Example 6

[0084] The difference between Example 6 and Example 3 is that the purification column does not include a modified graphitized carbon black layer, but all other aspects are the same.

[0085] Example 7

[0086] The difference between Example 7 and Example 3 is that a graphitized carbon black layer is used instead of a modified graphitized carbon black layer in the purification column.

[0087] Example 8

[0088] The difference between Example 8 and Example 3 is that the graphitized carbon black layer, Florisil layer, alkaline alumina layer, activated carbon layer, and neutral silica gel layer are arranged sequentially from top to bottom in the purification column; the rest are the same.

[0089] Example 9

[0090] The difference between Example 9 and Example 3 is that the height ratio of the purification column to the purification column is 1:2, while all other aspects are the same.

[0091] Example 10

[0092] The difference between Example 10 and Example 3 is that the mass ratio of the neutral silica gel layer, activated carbon layer, alkaline alumina layer, Florisil layer, and modified graphitized carbon black layer in the purification column is 1:1:1:1:1, while the rest are the same.

[0093] Example 11

[0094] The difference between Example 11 and Example 4 is that the glass fiber layer also includes activated carbon and titanium dioxide, and the mass ratio of glass fiber, activated carbon and titanium dioxide is 1:1:1, while the rest are the same.

[0095] Comparative Example 1

[0096] The difference between Comparative Example 1 and Example 3 is that the purification column is not included; otherwise, they are the same.

[0097] Comparative Example 2

[0098] The difference between Comparative Example 2 and Example 3 is that in step (3), the sample first passes through a purification column and then through a cleansing column, while the rest are the same.

[0099] Experimental Example 1

[0100] The internal standard recovery rates of the analytical samples obtained in Examples 1-11 and Comparative Examples 1-2 were tested, with the internal standard added at a rate of 1000 pg (5 μL, 200 ng / mL). The test results are shown in Table 1.

[0101] Table 1 Recovery rate test results

[0102]

[0103]

[0104] The method for pretreatment of dioxins in fly ash samples provided in this application can remove the interference of polychlorinated biphenyls and polybrominated diphenyl ethers on the detection of dioxins. The method is simple, easy to operate and has a significantly reduced cost, and has high detection accuracy and high recovery rate.

[0105] The above description is merely an embodiment of this application, and the scope of protection of this application is not limited to these specific embodiments, but is determined by the claims of this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the technical concept and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for pretreatment of dioxins in fly ash samples, characterized in that, Includes the following steps: (1) Pretreatment of fly ash samples: The fly ash samples are dried, ground and acidified to make dioxins easier to extract; (2) Extraction of fly ash samples: The product obtained in step (1) is filtered, subjected to Soxhlet extraction in solid phase, and liquid-liquid extraction in liquid phase, and then combined and concentrated by rotary evaporation. (3) Purification of fly ash sample extract: The fly ash sample extract obtained in step (2) is purified, including passing the extract through a purification column and a purification column in sequence to obtain the analytical sample; The purification column comprises, from top to bottom, a neutral silica gel layer, an activated carbon layer, an alkaline alumina layer, a Florisil layer, and a modified graphitized carbon black layer; the purification column comprises, from top to bottom, a glass fiber layer, a silica gel sulfate layer, and an anhydrous sodium sulfate layer; the purification column and the purification column are connected in series. The modified graphitized carbon black in the modified graphitized carbon black layer is prepared by modifying graphitized carbon black with alkyl chlorosilanes.

2. The method for pretreatment of dioxins in fly ash samples according to claim 1, characterized in that, The height ratio of the purification column to the purification column is (5~3):(2~3).

3. The method for pretreatment of dioxins in fly ash samples according to claim 1, characterized in that, In the purification column, the mass ratio of the neutral silica gel layer, activated carbon layer, alkaline alumina layer, Florisil layer, and modified graphitized carbon black layer is (2-3):1:(3-5):(2-4):(2~3).

4. The method for pretreatment of dioxins in fly ash samples according to claim 1, characterized in that, In the purification column, the height ratio of the glass fiber layer, the silica gel sulfate layer, and the anhydrous sodium sulfate layer is (2~4):(7~10):

1.

5. The method for pretreatment of dioxins in fly ash samples according to claim 1, characterized in that, The preparation method of the modified graphitized carbon black includes the following steps: S1 disperses graphitized carbon black in anhydrous ethanol; S2 is added to alkyl chlorosilane, stirred until homogeneous, and then heated. After S3 is cooled, it is filtered, washed, and dried to obtain modified graphitized carbon black.

6. The method for pretreatment of dioxins in fly ash samples according to claim 5, characterized in that, The alkylchlorosilane includes octadecyltrichlorosilane or dodecyltrichlorosilane; the mass ratio of the alkylchlorosilane to graphitized carbon black is (1.5~2.5):

1.

7. The method for pretreatment of dioxins in fly ash samples according to claim 5, characterized in that, The heating treatment in S2 is carried out at a temperature of 60~80℃ for 1~2 hours.

8. The method for pretreatment of dioxins in fly ash samples according to claim 4, characterized in that, The glass fiber layer also includes activated carbon and titanium dioxide, and the mass ratio of glass fiber, activated carbon and titanium dioxide is (2~4):(1~3):(0.5~1).

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