Preparation of activated carbon / expanded graphite composite material and its application in adsorption of volatile organic compounds

Abstract

The application relates to the technical field of volatile organic pollutant treatment, in particular to a kind of activated carbon / expanded graphite composite material preparation and its volatile organic compound adsorption application.The application comprises the following steps: (1) by water washing and acid liquid immersion pretreatment activated carbon and expanded graphite two kinds of powder, standby; (2) preparation phosphoric acid-aluminum hydroxide-chitosan colloidal solution is used as binder, and composite material microspheres are made; (3) activated carbon and expanded graphite are immersed in phosphoric acid-aluminum hydroxide-chitosan colloidal solution, and colloidal substance containing two kinds of powder is obtained, and activated carbon / expanded graphite composite material is prepared through wet balling and drying process.The heat regeneration of composite material under microwave irradiation at room temperature is realized, the heat desorption regeneration cost of activated carbon adsorption material is reduced, and the high engineering problem of activated carbon material VOCs saturated adsorption heat regeneration cost is effectively solved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of volatile organic pollutants treatment, more particularly, it relates to a kind of activated carbon / expanded graphite composite material preparation and its volatile organic compound adsorption application. BACKGROUND

[0002] With the use of a large number of organic solvents in petroleum chemical industry, printing, paint production, surface coating and other processes, the volatile organic compounds discharged during production cause serious air pollution. Volatile organic compounds, referred to as VOCs, have become one of the main air pollutants in China and the world. VOCs are a kind of irritating gas with strong harmful effect, which can cause mutation, carcinogenesis and teratogenesis, and has a significant negative impact on the physiological function of human organs; VOCs have high chemical activity and can participate in photochemical reactions under light to form photochemical smog, thus exacerbating the deterioration of ambient air quality. Therefore, the treatment of volatile organic pollutants is of great significance to improve ambient air quality and protect the ecological environment and human health. At present, the technologies for treating volatile organic pollutants mainly include thermal combustion method, catalytic combustion method, biological degradation method, photocatalytic degradation method, UV light oxygen catalysis, plasma mineralization decomposition, condensation method, adsorption method and membrane separation technology. Compared with other technologies, the adsorption method has the advantages of high VOCs disposal efficiency, simple operation, reusable adsorbent and low energy consumption, and is suitable for the adsorption disposal of medium and low concentration VOCs, so it is an effective, economical and widely used volatile organic compound treatment technology.

[0003] The most widely used adsorbent for VOCs adsorption disposal is granular, honeycomb and fibrous activated carbon, which has a relatively developed pore structure and a large specific surface area. The adsorption and capture of organic pollutant molecules are realized by the active sites on the surface of the particles and in the micropores, and then the efficient treatment of VOCs is realized. In the process of VOCs adsorption disposal, the activated carbon needs to be desorbed and regenerated after adsorption saturation. The activated carbon regeneration technologies include biological degradation regeneration, catalytic oxidation regeneration method, solvent regeneration method, electrochemical regeneration method and heating regeneration, among which the heating regeneration is the most widely used in engineering applications. Patent CN108246259A discloses a preparation method of biochar for efficient adsorption of organic matter. The biomass waste is washed, crushed, soaked with acid and alkali, and carbonized at high temperature to prepare a biochar material with porous, network structure, large specific surface area and excellent VOCs adsorption performance. However, this method is complicated, uses strong acid and alkali in the preparation process, has potential environmental hazards, and has high energy consumption, so its engineering application performance is poor.

[0004] In the patent CN109985601A, the applicant uses phosphorus-doped carbon nitride and activated carbon fiber as the main materials, and proposes an activated carbon fiber adsorbent for volatile organic compounds and a preparation method thereof. Through impregnation and drying treatment of phosphorus-containing precursor and nitrogen-containing precursor solution, a high-activity phosphorus-doped carbon nitride coating is loaded on the surface of activated carbon fiber, which improves the adsorption and desorption efficiency of activated carbon fiber for aldehyde and ketone volatile organic compounds, and improves the cyclic adsorption performance of the adsorbent. The activated carbon fiber adsorbent prepared by the patent technology has high adsorption capacity for high-concentration ketone organic compounds, but low adsorption capacity for low-concentration organic compounds. The regeneration performance and process of the adsorbent are not explicitly stated, and the disposal efficiency of the engineering application needs to be explored.

[0005] During the traditional heating regeneration process of activated carbon adsorbent materials, high-temperature calcination can cause a large amount of carbon loss, resulting in a decrease in the content of oxygen-containing functional groups on the surface of the adsorbent. At the same time, the carbonized residues of organic matter can cause a decrease in pore volume and blockage of micropore transmission channels, which in turn reduces the adsorption efficiency of activated carbon after heating regeneration. Compared with activated carbon, expanded graphite and graphene functional carbon materials can also effectively achieve the adsorption and disposal of VOCs, and their regeneration can be achieved by microwave irradiation, which is energy-saving, simple and convenient.

[0006] In the patent CN104874354A, the applicant first soaks the graphene film in an inorganic solution, and then processes it through bismuth-zinc metal surface loading, organic solution soaking, and high-temperature treatment, to obtain a graphene film with high adsorption capacity and high treatment efficiency, which can be used for the treatment of high-toxicity, low-concentration, and highly-flowable organic waste gas. However, the graphene film has few active sites on its surface and is difficult to regenerate by microwave irradiation. The patent CN109876773B mentions a method for adsorbing volatile organic compounds by expanded graphite and resource utilization of waste, which first washes and impregnates the expanded graphite to obtain expanded graphite coated with aluminum hydroxide-clay-diatomite on its surface, realizes the adsorption and disposal of VOCs and the microwave irradiation regeneration after adsorption saturation, and then processes the waste adsorbent through ozone oxidation, modified Hummer chemical oxidation, and chemical reduction to obtain graphene nanosheets, graphite oxide, and graphene functional materials in sequence, achieving the resource utilization of waste and reducing the generation of hazardous waste from the source. However, the VOCs adsorption and disposal efficiency of expanded graphite adsorbent still needs to be improved for engineering application. Therefore, it is an important measure to promote the pollution control of volatile organic compounds in industrial enterprises to develop a new adsorbent with low preparation cost, excellent VOCs adsorption performance, and simple and convenient saturation and desorption process, based on the excellent VOCs adsorption performance of activated carbon and the excellent microwave irradiation regeneration performance of expanded graphite. SUMMARY

[0007] The present disclosure provides a kind of activated carbon / expanded graphite composite material preparation and its volatile organic compounds adsorption application, the activated carbon / expanded graphite composite adsorption material prepared, not only retains the excellent VOCs adsorption performance of activated carbon, and give full play to the microwave irradiation heat generation characteristics of expanded graphite, realize the heat regeneration of composite material microwave irradiation at room temperature, reduce the heat desorption regeneration cost of activated carbon adsorption material, effectively solve the high cost of activated carbon material VOCs saturated adsorption heat regeneration engineering problem.

[0008] In a first aspect, the present disclosure provides a method for preparing an activated carbon / expanded graphite composite material, comprising the following steps:

[0009] (1) pretreat the two powders of activated carbon and expanded graphite by water washing and acid immersion, for standby use;

[0010] (2) prepare a phosphoric acid-aluminum hydroxide-chitosan colloidal solution as a binder to make composite material microspheres;

[0011] (3) immerse the activated carbon and expanded graphite in the phosphoric acid-aluminum hydroxide-chitosan colloidal solution to obtain a colloidal substance containing the two powders, and then prepare the activated carbon / expanded graphite composite material through a wet ball-making and drying process.

[0012] Preferably, in step (1), the method for preparing the expanded graphite comprises the following steps:

[0013] A1: the expanded graphite is prepared by an electrochemical anodic oxidation intercalation process, and the main equipment used includes a direct current stabilized power supply, a 250 mL beaker used as an electrolyte pool, and a microwave oven with a power of 500 W;

[0014] A2: the electrochemical reactor used for preparing the expanded graphite is composed of a direct current stabilized power supply, an electrolytic pool, a composite anode composed of natural graphite flakes and a stainless steel strip, and a ring-shaped copper mesh cathode;

[0015] A3: the natural flaky graphite is subjected to electrochemical intercalation and microwave puffing treatment.

[0016] Preferably, in step A1, the main materials used for preparing the expanded graphite include natural flaky graphite, sodium nitrate, glacial acetic acid, a stainless steel anode strip with a size of 20 cm x 1 cm x 0.3 cm, and a ring-shaped copper mesh cathode obtained by bending a copper mesh to a length of 20 cm and a width of 8 cm.

[0017] Preferably, in step A2, the composite anode is treated as follows: a cloth bag with a size of 1.5 cm x 6 cm is filled with natural graphite flakes, then one stainless steel strip is inserted into the cloth bag so that the natural graphite flakes are evenly distributed around the stainless steel electrode, and the ring-shaped cathode copper mesh is arranged around the anode.

[0018] Preferably, in step A3, the specific method of electrochemical intercalation and microwave expansion treatment of the natural flake graphite comprises the following steps:

[0019] B1: Prepare a sodium nitrate solution with a concentration of 45-50 g / L, add 100-120 mL of edible vinegar to the sodium nitrate solution, and stir well to prepare a sodium nitrate-vinegar aqueous solution;

[0020] B2: Add 125 mL of the sodium nitrate-vinegar aqueous solution to a 250 mL beaker used as an electrolyte pool, turn on the DC voltage stabilizing power switch, control the reaction current and reaction time to be 1-1.5 A and 1-2 h respectively, and carry out the electrochemical intercalation reaction of flake graphite at room temperature;

[0021] B3: After the electrochemical intercalation reaction of flake graphite is completed, turn off the power, first remove the composite anode, ultrasonically treat the flake graphite cloth bag for 3 min, then wash it thoroughly with water to remove the surface residues such as sodium nitrate and vinegar, and when the washing water is neutral, take out the intercalated flake graphite from the bag and place it in an oven for drying, with a drying temperature of 80°C and a drying time of 5-8 h, to obtain expanded graphite;

[0022] B4: Place 0.5 g of the expanded graphite in a microwave oven with a power of 500 W, turn on the microwave oven switch, and carry out microwave expansion treatment of the expanded graphite at room temperature, with a microwave expansion time controlled to be 15-20 s, to obtain expanded graphite with a fluffy structure and a worm-like morphology.

[0023] Preferably, the adsorption sites of the expanded graphite are removed by water washing to remove the surface ash of activated carbon and expanded graphite powder, and by acid immersion to remove inorganic salts, heavy metals and other impurities adsorbed inside the two powders, and the specific method comprises the following steps:

[0024] C1: Water washing process: Put the coconut shell activated carbon particles with an average particle size of 0.3 mm into a beaker, boil deionized water to wash for 3-5 min to remove the surface ash, filter, then boil again to wash, and repeat this process for 3 times, then place in a flask for standby after washing;

[0025] C2: Acid immersion process: oscillatory immersion in a 2-3 mol / L hydrochloric acid aqueous solution at a temperature of 40-50°C for 10 min, then filter, acid wash again, repeat this process for 3 times, then wash with water to pH=6-7, and then place in an oven for drying treatment at 120°C for 8-12 h, and seal and store after drying.

[0026] Preferably, in step (3), the preparation method of the phosphoric acid-aluminum hydroxide powder-chitosan gel-like solution by wet balling comprises the following steps:

[0027] D1: phosphoric acid with a mass concentration of 85%, deionized water, aluminum hydroxide powder, chitosan, the mass ratio of the substances is as follows: phosphoric acid: deionized water: aluminum hydroxide powder: chitosan = 1:1:2:3;

[0028] D2: the phosphoric acid and water are mixed in proportion, stirred uniformly to prepare a phosphoric acid aqueous solution, then the aluminum hydroxide powder is added to the phosphoric acid aqueous solution, stirred for 10-15 min to obtain a uniform emulsion, then the chitosan is added to the emulsion, and stirred for 20-30 min to obtain a light yellow gel solution.

[0029] Preferably, the gel solution is used to fully impregnate the two powders of the activated carbon and the expanded graphite, and the mixed gel is used to prepare spherical activated carbon / expanded graphite composite materials by wet balling, and the activated carbon, the expanded graphite, and the phosphoric acid-aluminum hydroxide powder-chitosan gel solution are used in a mass ratio of 1-3 g:1-3 g:2-5 mL.

[0030] The specific preparation method comprises the following steps:

[0031] E1: the activated carbon particles and the expanded graphite powder are added to the phosphoric acid-aluminum hydroxide-chitosan gel solution, and stirred at room temperature for 20-30 min to uniformly disperse and fully impregnate the activated carbon particles and the expanded graphite powder, to obtain a uniformly mixed paste;

[0032] E2: the paste containing the activated carbon particles and the expanded graphite impregnated material is placed in a balling machine to prepare spherical particles, and the average particle size of the spherical particles is about 0.85 cm.

[0033] E3: the prepared spherical particles are placed in a muffle furnace for high-temperature heat treatment, the heat treatment temperature is 550°C, and the heat treatment time is 3-5 h, and after the muffle furnace hearth temperature is naturally cooled to room temperature, the spherical activated carbon / expanded graphite composite adsorption material is obtained.

[0034] In a second aspect, the present disclosure provides an application of an activated carbon / expanded graphite composite material, and the activated carbon / expanded graphite composite adsorption material is used for adsorption and disposal of volatile organic compounds, and the application method specifically comprises the following steps:

[0035] H1: the VOCs gas is made to flow out of the heating device by the heating device and the air pump blowing effect in the VOCs generator, the temperature regulation range of the heating device is 25-50℃, the air pump blowing flow rate is 0.2-1.0 mL / min; in order to control the concentration of VOCs entering the adsorption column, another air pipeline is designed to blow air into the pipeline by the air pump blowing effect, so that the air is mixed with the VOCs gas in the gas mixing chamber, the gas mixing chamber is designed with a baffle, and the VOCs concentration at the inlet of the adsorption column is controlled to be 140-170 mg / m 3 ;

[0036] H2: a three-way sampling port is arranged in front of the adsorption column, and the adsorption column is filled with 10g of the activated carbon / expanded graphite composite material; when the VOCs gas enters the lower inlet of the adsorption column, the initial inlet concentration is determined by sampling, and with the adsorption of the activated carbon / expanded graphite composite material, the VOCs gas entering the adsorption column is adsorbed and captured by the adsorption material; when the outlet VOCs monitoring concentration of the adsorption column is not zero, the gas at the outlet is introduced into the tail gas treatment device, and the tail gas is treated by absorbing the sodium hypochlorite aqueous solution with a mass concentration of 10%.

[0037] Preferably, the activated carbon / expanded graphite composite adsorption material is used for methyl orange wastewater adsorption disposal after being discarded, and the specific process comprises the following steps:

[0038] S1: the waste of the activated carbon / expanded graphite composite material after adsorption failure is added to a 1wt% polyaluminum chloride solution, immersed at room temperature for 24h, and then taken out from the solution and placed in a 60℃ oven for drying for 24h;

[0039] S2: a methyl orange aqueous solution with a concentration of 12-18g / L is prepared, and 3-5g of the activated carbon / expanded graphite composite material after adsorption saturation is added to 100mL of the methyl orange solution, and the solution is slowly shaken at room temperature;

[0040] S3: the adsorption process control conditions of the activated carbon / expanded graphite waste composite material are that the initial concentration of the methyl orange is 15g / L, the pH value of the solution is controlled to be 3-5, the addition amount of the activated carbon / expanded graphite waste composite material is 4g / 100mL, the adsorption temperature is room temperature, and the adsorption time is 20min.

[0041] In summary, the application has the following beneficial effects:

[0042] 1. In the application, the purpose is to fully exert the excellent volatile organic compound adsorption performance of the granular activated carbon and the heat production characteristics of the microwave irradiation swelling of the expanded graphite, a preparation method of an activated carbon / expanded graphite composite material is provided, and the adsorption disposal efficiency of VOCs is explored;

[0043] 2. The activated carbon / expanded graphite composite adsorption material prepared in the application not only retains the excellent VOCs adsorption performance of activated carbon, but also fully utilizes the microwave irradiation heat generation characteristics of expanded graphite, realizes the heat generation regeneration of the composite material under microwave irradiation at room temperature, reduces the heat desorption regeneration cost of the activated carbon adsorption material, and effectively solves the engineering problem of high cost of heat regeneration of activated carbon materials after saturated adsorption of VOCs.

[0044] 3. The activated carbon / expanded graphite composite material prepared in the application has a spherical appearance, an average particle size of 0.85 cm, an average density of 2.0 g / cm 3 , an average specific surface area of 829.45 m 2 / g, an average pore volume of 0.44 m 3 / g, and an average pore size of 2.1 nm; when the VOCs concentration at the inlet of the adsorption column is 140-170 mg / m 3 , the adsorption saturation is reached after 347-381 min, and the VOCs adsorption capacity of the activated carbon / expanded graphite composite material is 216-231 mg / g.

[0045] It should be understood that the above general description and the following detailed description are only exemplary and explanatory, and cannot limit the protection scope of the present disclosure. BRIEF DESCRIPTION OF DRAWINGS

[0046] 1、 Figure 1 is a schematic diagram of an electrochemical reactor for preparing expanded graphite in the application;

[0047] 2、 Figure 2 is a preparation process of the activated carbon / expanded graphite composite adsorption material in the application;

[0048] 3、 Figure 3 is a schematic diagram of an adsorption device in the application;

[0049] 4、 Figure 4 is a microstructure of the activated carbon composite adsorption material in the application;

[0050] 5、 Figure 5 is a microstructure of the expanded graphite composite adsorption material in the application;

[0051] 6、 Figure 6 is an FTIR spectrum of the activated carbon / expanded graphite composite adsorption material in the application;

[0052] 7、 Figure 7 is a pore size distribution diagram of the activated carbon / expanded graphite composite adsorption material in the application. DETAILED DESCRIPTION

[0053] The application will be further described in detail in connection with the following examples. It is particularly pointed out that the following examples were prepared under conventional conditions or the conditions recommended by the manufacturer, and the raw materials used in the following examples can be obtained from ordinary commercial sources unless otherwise specified.

[0054] 1. Preparation of activated carbon / expanded graphite composite material

[0055] (1) Preparation of expanded graphite

[0056] 1) Expanded graphite was prepared by electrochemical anodic oxidation intercalation process. The main materials used in the preparation of expanded graphite were commercially available natural flake graphite, sodium nitrate, glacial acetic acid, stainless steel anode strips with a size of 20 cm x 1 cm x 0.3 cm, and a copper ring-shaped cathode with a length of 20 cm and a width of 8 cm. The main equipment used was a direct current stabilized power supply, a 250 mL beaker used as an electrolyte tank, and a microwave oven with a power of 500 W.

[0057] 2) Construction of electrochemical reactor

[0058] The electrochemical reactor used in the preparation of expanded graphite was composed of a direct current stabilized power supply, an electrolytic cell, a composite anode composed of natural graphite flakes and a stainless steel strip, and a ring-shaped copper cathode. The composite anode was filled with natural graphite flakes in a 1.5 cm x 6 cm cloth bag, and then one stainless steel strip was inserted into it, with the natural graphite flakes evenly distributed around the stainless steel electrode. The ring-shaped copper cathode was arranged around the anode in a ring-shaped manner, enhancing the transfer of electrons on the electrode and the conduction of ions in the electrolyte, and ensuring the efficiency of electrochemical intercalation of flake graphite. The schematic diagram of the electrochemical reactor is shown in Figure 1 .

[0059] 3) Electrochemical intercalation and microwave puffing of natural flake graphite

[0060] ① A sodium nitrate solution with a concentration of 45-50 g / L was prepared, and then 100-120 mL of edible vinegar was added to the sodium nitrate solution and stirred evenly to prepare a sodium nitrate-vinegar aqueous solution;

[0061] ② 125 mL of the sodium nitrate-vinegar aqueous solution was added to the 250 mL beaker used as the electrolyte tank, the direct current stabilized power supply switch was turned on, the reaction current and reaction time were controlled at 1-1.5 A and 1-2 h respectively, and the electrochemical intercalation reaction of flake graphite was carried out at room temperature;

[0062] ③After the electrochemical intercalation reaction of flake graphite is completed, the power is turned off, the composite anode is taken out first, the flake graphite bag is ultrasonically treated for 3 minutes, then it is washed with water to remove sodium nitrate and acetone on the surface, and when the washing water is neutral, the intercalated flake graphite is taken out of the bag and dried in an oven, the drying temperature is 80°C, and the drying time is 5-8 hours, so that expandable graphite is prepared;

[0063] ④0.5g of expandable graphite is placed in a microwave oven with a power of 500W, the microwave oven switch is turned on, and the expandable graphite is treated by microwave expansion at room temperature, the microwave expansion time is controlled to be 15-20 seconds, and after the microwave expansion is completed, the morphology of the expandable graphite changes from granular to fluffy worm-like, so that expanded graphite is prepared.

[0064] (2) Preparation of activated carbon / expanded graphite composite material

[0065] 1) Pretreatment of activated carbon and expanded graphite

[0066] The pretreatment process of the granular coconut shell activated carbon is as follows: the coconut shell activated carbon with an average particle size of 0.3mm is placed in a beaker containing deionized water, boiled for 3-5 minutes, and then filtered and washed with water, and this process is repeated 3 times to ensure that the surface ash is clean; then the washed granular coconut shell activated carbon is placed in a 2-3mol / L hydrochloric acid solution and soaked at 40-50°C for 10 minutes, the solution is stirred during the soaking process, then the solution is filtered and the activated carbon particles are washed with water until the washing water pH is 6-7; then the acid- soaked and water-washed activated carbon particles are dried in an oven at 120°C for 8-12 hours, and finally the treated granular coconut shell activated carbon is sealed and stored for use;

[0067] The pretreatment process of the expanded graphite is as follows: first, the prepared expanded graphite is placed in a beaker containing distilled water, ultrasonically treated at room temperature for 10 minutes, and then washed with water several times until the color of the washing water changes from the initial light yellow to colorless after standing; then the washed expanded graphite is dried in an oven, the drying temperature is 60°C, and the drying time is 3-5 hours; finally, the treated expanded graphite is placed in a stoppered reagent bottle for use.

[0068] 2) Preparation of phosphoric acid-aluminum hydroxide-chitosan gel solution

[0069] ①The raw materials for preparing the phosphoric acid-aluminum hydroxide-chitosan gel solution are: 85% mass concentration phosphoric acid, deionized water, aluminum hydroxide powder and chitosan, and the amount of each raw material has the following mass ratio relationship: phosphoric acid: deionized water: aluminum hydroxide powder: chitosan = 1:1:2:3;

[0070] (2) First, mix phosphoric acid and water in a certain proportion, stir well to prepare a phosphoric acid aqueous solution; then add aluminum hydroxide powder to the phosphoric acid aqueous solution, stir for 10-15 min to obtain a uniform emulsion; then add chitosan to the emulsion, stir well for 20-30 min to obtain a light yellow colloidal solution;

[0071] 3) Impregnation treatment of activated carbon and expanded graphite

[0072] The amounts of activated carbon, expanded graphite, and phosphoric acid-aluminum hydroxide powder-chitosan colloidal solution are as follows: 1-3 g: 1-3 g: 2-5 mL, and the specific process is as follows:

[0073] First, add activated carbon particles and expanded graphite powder to the phosphoric acid-aluminum hydroxide-chitosan colloidal solution, stir well at room temperature for 20-30 min to make the activated carbon particles and expanded graphite powder uniformly dispersed and fully impregnated, obtaining a uniform paste;

[0074] Then, place the activated carbon particle and expanded graphite powder paste impregnation in a ball making machine to obtain spherical particles, and the average particle size of the spherical particles is about 0.85 cm;

[0075] Finally, place the prepared spherical particles in a muffle furnace for high-temperature heat treatment, the heat treatment temperature is 550℃, and the heat treatment time is 3-5 h. When the furnace temperature of the muffle furnace naturally cools to room temperature, spherical activated carbon / expanded graphite composite adsorbent material is obtained, and the preparation process of the composite material is as shown in Figure 2 .

[0076] 2. Activated carbon / expanded graphite composite material adsorbing volatile organic compounds

[0077] (1) VOCs adsorption treatment system

[0078] The experimental device for adsorbing VOCs by the activated carbon / expanded graphite composite material of the present application is shown in Figure 3 , which is divided into a VOCs generating device, an adsorption column, and a tail gas treatment part. The selected VOCs target pollutants are ethyl acetate and toluene.

[0079] (2) VOCs adsorption treatment process

[0080] 1) In the VOCs generator, the VOCs gas flows out of the heating device with the air flow generated by the heating device and the air pump. The temperature of the heating device is controlled in the range of 25-50℃, and the air flow rate of the air pump is 0.2-1.0 mL / min. In order to control the concentration of VOCs entering the adsorption column, another air pipeline is designed to blow air into the pipeline by the air pump, so that the air is mixed with the VOCs gas in the gas mixing chamber. The baffle in the gas mixing chamber is beneficial to the full mixing of VOCs and air. The concentration of VOCs at the inlet of the adsorption column is controlled to be 140-170 mg / m 3 ;

[0081] 2) A three-way sampling port is provided before the adsorption column, and the adsorption column is filled with 10g of activated carbon / expanded graphite composite material. When the VOCs gas enters the lower inlet of the adsorption column, the initial inlet concentration is determined by sampling. With the adsorption of the activated carbon / expanded graphite composite material, the VOCs gas entering the adsorption column is adsorbed and captured by the adsorption material. When the outlet VOCs monitoring concentration is no longer zero, the gas at the outlet is introduced into the tail gas treatment device for tail gas treatment by the absorption liquid. The absorption liquid used in the present application is a 10% sodium hypochlorite aqueous solution.

[0082] (3) Microwave irradiation regeneration of activated carbon / expanded graphite composite material adsorption saturation

[0083] 1) After the activated carbon / expanded graphite composite material is saturated, it is taken out from the adsorption column for microwave irradiation regeneration. The specific process is as follows: first, 20g of adsorption saturated activated carbon / expanded graphite material is placed in a ceramic evaporating dish, then the evaporating dish is placed in a microwave oven with a rated frequency of 2450MHz and an output power of 600W, and the activated carbon / expanded graphite composite material is treated by microwave activation at room temperature. The microwave treatment time is 5min.

[0084] 2) After the microwave activation treatment is completed and the temperature of the evaporating dish is naturally cooled to room temperature, it is taken out from the microwave oven. The regeneration efficiency of the activated carbon / expanded graphite composite material after microwave treatment can reach 94.3%, and the composite material is added to the adsorption column after microwave irradiation treatment, which can be used for the adsorption treatment of volatile organic compounds.

[0085] 3) When the regeneration efficiency of the activated carbon / expanded graphite composite material is less than 65%, it is determined that it is no longer suitable for the adsorption treatment of volatile organic compounds, i.e. as an adsorption waste for treatment.

[0086] 3、Resource utilization of activated carbon / expanded graphite composite material after adsorption waste

[0087] (1) The waste of activated carbon / expanded graphite composite material after adsorption failure was added to 1wt% polyaluminum chloride aqueous solution, immersed at room temperature for 24h, then taken out from the solution and placed in an oven at 60℃ for drying for 24h;

[0088] (2) A methyl orange aqueous solution with a concentration of 12-18g / L was prepared, 3-5g of activated carbon / expanded graphite composite material after adsorption saturation was added to 100mL of methyl orange solution, the solution was slowly shaken at room temperature to realize the adsorption and capture of methyl orange dye molecules by the waste activated carbon / expanded graphite composite material;

[0089] (3) To realize efficient adsorption and capture of methyl orange dye molecules in aqueous solution, the adsorption process control conditions of the waste activated carbon / expanded graphite composite material were as follows: the initial concentration of methyl orange was 15g / L, the pH value of the solution was controlled at 3-5, the amount of waste activated carbon / expanded graphite composite material added was 4g / 100mL, the adsorption temperature was room temperature, and the adsorption time was 20min;

[0090] (4) After the waste activated carbon / expanded graphite composite material adsorbed and captured methyl orange dye, it could be finally disposed of by incineration according to the requirements for disposal of hazardous waste.

[0091] EMBODIMENT

[0092] EMBODIMENT 1

[0093] 1. Preparation of activated carbon / expanded graphite composite material

[0094] (1) Preparation of expanded graphite

[0095] 1) Expanded graphite was prepared by electrochemical anodic oxidation intercalation process. The main materials used for expanded graphite preparation included commercially available natural flake graphite, sodium nitrate, edible vinegar, stainless steel anode strip with a specification of 20cmx1cmx0.3cm, copper ring-shaped cathode with a length of 20cm and a width of 8cm, and a DC stabilized power supply, a 250mL beaker used as an electrolyte pool, and a 500W microwave oven.

[0096] 2) Construction of electrochemical reactor

[0097] The electrochemical reactor used for expanded graphite preparation consisted of a DC stabilized power supply, an electrolytic cell, a composite anode composed of natural graphite flakes and a stainless steel strip, and a ring-shaped copper cathode. The composite anode was prepared by filling a 1.5cmx6cm cloth bag with natural graphite flakes and then inserting a stainless steel strip into the bag so that the natural graphite flakes were evenly distributed around the stainless steel electrode. The ring-shaped cathode copper was arranged around the anode in a ring shape to enhance the transfer of electrons on the electrode and the conduction of ions in the electrolyte, thereby ensuring the efficiency of electrochemical intercalation of flake graphite.

[0098] 3) Electrochemical intercalation and microwave expansion of natural flake graphite

[0099] ①A 50g / L sodium nitrate solution was prepared, and then 100 mL of acetone was added to the sodium nitrate solution, which was stirred uniformly to prepare a sodium nitrate-acetone aqueous solution;

[0100] ②The 125 mL sodium nitrate-acetone aqueous solution was added to a 250 mL beaker used as an electrolyte pool, and the switch of a direct current stabilizing power supply was turned on. The current and time were controlled to be 1 A and 1 h, respectively, and the electrochemical intercalation reaction of flake graphite was carried out at room temperature;

[0101] ③After the electrochemical intercalation reaction of flake graphite was completed, the power was turned off, the composite anode was taken out first, the flake graphite cloth bag was ultrasonically treated for 3 min, and then it was washed with water to remove the residual sodium nitrate and acetone on the surface. When the washing water was neutral, the intercalated flake graphite was taken out of the bag and placed in an oven for drying. The drying temperature was 80℃, and the drying time was 6 h, thereby obtaining expandable graphite;

[0102] ④The 0.5 g of expandable graphite was placed in a microwave oven with a power of 500 W, and the microwave oven switch was turned on to microwave expand the expandable graphite at room temperature. The microwave expansion time was controlled to be 15 seconds, thereby obtaining expanded graphite.

[0103] (2) Preparation of activated carbon / expanded graphite composite material

[0104] 1) Pretreatment of activated carbon and expanded graphite

[0105] The pretreatment process of the granular coconut shell activated carbon was as follows: the coconut shell activated carbon with an average particle size of 0.3 mm was placed in a beaker containing deionized water, boiled for 3 min, and then filtered and washed with water. This process was repeated 3 times to ensure that the surface ash was completely cleaned. Then, the washed granular coconut shell activated carbon was placed in a 2 mol / L hydrochloric acid aqueous solution and soaked at 50℃ for 10 min. The solution was stirred during the soaking process, and then filtered and washed with water until the washing water pH was 7. Then, the acid- soaked and washed activated carbon particles were placed in an oven and dried at 120℃ for 8 h. Finally, the treated granular coconut shell activated carbon was sealed and stored for use;

[0106] The pretreatment process of the expanded graphite was as follows: the prepared expanded graphite was first placed in a beaker containing distilled water and ultrasonically treated at room temperature for 10 min, and then washed with water for multiple times until the color of the washing water changed from the initial light yellow to colorless after standing. Then, the washed expanded graphite was dried in an oven at a drying temperature of 60℃ for 5 h. Finally, the treated expanded graphite was placed in a stoppered reagent bottle for use.

[0107] 2) Preparation of phosphoric acid-aluminum hydroxide-chitosan colloidal solution

[0108] ①The raw materials used for the preparation of phosphoric acid-aluminum hydroxide-chitosan colloidal solution include 85% mass concentration phosphoric acid, deionized water, aluminum hydroxide powder, and chitosan, and the amount of each is in the following mass ratio: phosphoric acid: deionized water: aluminum hydroxide powder: chitosan = 1:1:2:3

[0109] ②First, mix phosphoric acid and water in a certain proportion, stir evenly to prepare a phosphoric acid aqueous solution; then add aluminum hydroxide powder to the phosphoric acid aqueous solution and stir for 10 minutes to obtain a uniform emulsion; then add chitosan to the emulsion and stir thoroughly for 20 minutes to obtain a light yellow colloidal solution.

[0110] 3) Impregnation treatment of activated carbon and expanded graphite

[0111] First, add activated carbon particles and expanded graphite powder to the phosphoric acid-aluminum hydroxide-chitosan colloidal solution and stir thoroughly at room temperature for 20 minutes to ensure uniform dispersion and sufficient impregnation of the activated carbon particles and expanded graphite powder, resulting in a paste of uniformly mixed powders; the amounts of activated carbon, expanded graphite, and phosphoric acid-aluminum hydroxide-chitosan colloidal solution are in the following ratio: 1.5g:1g:4ml, and the specific process is as follows:

[0112] Then, place the paste of activated carbon particles and expanded graphite powder in a ball making machine to obtain spherical particles with an average particle size of about 0.85cm;

[0113] Finally, heat treat the obtained spherical particles in a muffle furnace at a temperature of 550℃ for 3 hours to obtain spherical activated carbon / expanded graphite composite adsorbent material.

[0114] 2, Activated carbon / expanded graphite composite material adsorbs volatile organic compounds

[0115] (1) Ethyl acetate adsorption process

[0116] In the VOCs generator, ethyl acetate gas is made to flow out of the heating device along with the airflow generated by the air pump, the heating device temperature is controlled in the range of 30℃, the air pump blowing flow rate is 1.0mL / min, and 10g of composite material is filled in the adsorption column; the ethyl acetate concentration (calculated as non-methane hydrocarbons) at the inlet of the adsorption column is controlled at 140mg / m 3 , and a 10% mass concentration sodium hypochlorite aqueous solution is introduced at the outlet for tail gas treatment. After 347 minutes, the adsorption saturation is reached, and the adsorption capacity is 216mg / g.

[0117] Example 2

[0118] 1. Preparation of activated carbon / expanded graphite composite material

[0119] (1) Preparation of expanded graphite

[0120] The preparation process of the expanded graphite is the same as that of Example 1, and will not be described in detail.

[0121] 1) Construction of electrochemical reactor

[0122] The construction of the electrochemical reactor used for the preparation of the expanded graphite is the same as that of Example 1, and will not be described in detail.

[0123] 2) Electrochemical intercalation and microwave expansion of natural flake graphite

[0124] ① A sodium nitrate solution with a concentration of 45 g / L is prepared, and then 120 mL of acetone is added to the sodium nitrate solution, which is stirred uniformly to prepare a sodium nitrate-acetone aqueous solution;

[0125] ② The volume of the sodium nitrate-acetone aqueous solution is 125 mL, which is added to a 250 mL beaker used as an electrolyte pool. The switch of the direct current stabilizing power supply is turned on, and the reaction current and reaction time are controlled to be 1.5 A and 2 h, respectively. The electrochemical intercalation reaction of the flake graphite is carried out at room temperature;

[0126] ③ After the electrochemical intercalation reaction of the flake graphite is completed, the power supply is turned off. First, the composite anode is taken out, and the flake graphite cloth bag is ultrasonically treated for 3 min. Then, the flake graphite cloth bag is washed with water to remove the residual sodium nitrate and acetone on the surface. When the washing water is neutral, the intercalated flake graphite is taken out of the bag and placed in an oven for drying. The drying temperature is 80°C, and the drying time is 6 h, thereby obtaining the expandable graphite;

[0127] ④ 0.5 g of the expandable graphite is placed in a microwave oven with a power of 500 W. The microwave oven is turned on, and the expandable graphite is subjected to microwave expansion treatment at room temperature. The microwave expansion time is controlled to be 20 seconds, thereby obtaining the expanded graphite.

[0128] (2) Preparation of activated carbon / expanded graphite composite material

[0129] 1) Pretreatment of activated carbon and expanded graphite

[0130] The pretreatment process of the granular coconut shell activated carbon is as follows: the coconut shell activated carbon with an average particle size of 0.3 mm is placed in a beaker containing deionized water, boiled for 5 min, and then filtered and washed with water, and this process is repeated 3 times to ensure that the surface ash is completely cleaned; then the granular coconut shell activated carbon after water washing is placed in a 3 mol / L hydrochloric acid aqueous solution and soaked at 47°C for 10 min, the solution is stirred during the soaking process, then the solution is filtered and the activated carbon particles are washed with water until the washing water has a pH of 6; then the activated carbon particles after acid soaking and water washing are placed in an oven and dried at 120°C for 12 h, and finally the treated granular coconut shell activated carbon is sealed and stored for use

[0131] The pretreatment process of the expanded graphite is as follows: first, the prepared expanded graphite is placed in a beaker containing distilled water, ultrasonically treated at room temperature for 10 min, and then washed with water for multiple times until the color of the washing water changes from the initial light yellow to colorless after standing; then the washed expanded graphite is dried in an oven, the drying temperature is 60°C, and the drying time is 3 h; finally, the treated expanded graphite is placed in a stoppered reagent bottle for standby.

[0132] 2) Preparation of phosphoric acid-aluminum hydroxide-chitosan colloidal solution

[0133] The same as in Example 1, except that the aluminum hydroxide powder is added to the phosphoric acid aqueous solution, the stirring time is 15 min, and then the chitosan is added to the emulsion, and the stirring time is 30 min;

[0134] 3) Impregnation treatment of activated carbon and expanded graphite

[0135] The same as in Example 1, except that the amounts of activated carbon, expanded graphite, and phosphoric acid-aluminum hydroxide powder-chitosan colloidal solution are in the ratio of 1.5 g:1.5 g:3 ml;

[0136] 2) Ethyl acetate and toluene mixed gas adsorption process

[0137] The ethyl acetate and toluene mixed gas adsorption treatment process is basically the same as in Example 1. The ethyl acetate and toluene gas is made to flow out of the heating device by the air pump blowing effect, the temperature of the heating device is controlled in the range of 25°C, the air pump blowing flow rate is 0.8 mL / min, and 10 g of the composite material is filled in the adsorption column; the total concentration (calculated as non-methane hydrocarbons) of ethyl acetate and toluene at the inlet of the adsorption column is controlled to be 170 mg / m 3 , and a 10% sodium hypochlorite aqueous solution is introduced at the outlet for tail gas treatment. The experimental results show that the adsorption saturation is reached after 381 min, and the adsorption capacity is 231 mg / g.

[0138] Example 3

[0139] 1. Preparation of activated carbon / expanded graphite composite material

[0140] (1) Preparation of expanded graphite

[0141] The preparation process of the expanded graphite is the same as that of Example 1, and will not be described in detail.

[0142] 1) Construction of the electrochemical reactor for the preparation of expanded graphite The construction of the electrochemical reactor is the same as that of Example 1, and will not be described in detail.

[0143] 2) Electrochemical intercalation and microwave expansion of natural flake graphite

[0144] ① A sodium nitrate solution with a concentration of 47 g / L is prepared, and then 110 mL of acetone is added to the sodium nitrate solution, which is stirred uniformly to prepare a sodium nitrate-acetone aqueous solution;

[0145] ② The 125 mL sodium nitrate-acetone aqueous solution is added to a 250 mL beaker used as an electrolyte pool, and the switch of the direct current stabilizing power supply is turned on, and the reaction current and reaction time are controlled to be 1.2 A and 1.5 h respectively, and the electrochemical intercalation reaction of the flake graphite is carried out at room temperature;

[0146] ③ After the electrochemical intercalation reaction of the flake graphite is completed, the power supply is turned off, and first, the composite anode is taken out, and the flake graphite bag is ultrasonically treated for 3 min, and then it is washed with water to remove the residual sodium nitrate and acetone and other substances on the surface, and when the washing water is neutral, the intercalated flake graphite is taken out of the bag and placed in an oven for drying, the drying temperature is 80°C, and the drying time is 7 h, and the expandable graphite is prepared.

[0147] ④ 0.5 g of the expandable graphite is placed in a microwave oven with a power of 500 W, and the microwave oven switch is turned on to perform microwave expansion treatment on the expandable graphite at room temperature, and the microwave expansion time is controlled to be 17 seconds, and after the microwave expansion is completed, the morphology of the expandable graphite changes from granular to fluffy worm-like, and the expanded graphite is prepared.

[0148] (2) Preparation of activated carbon / expanded graphite composite material

[0149] 1) Pretreatment of activated carbon and expanded graphite

[0150] The pretreatment process of the granular coconut shell activated carbon is as follows: the coconut shell activated carbon with an average particle size of 0.3 mm is placed in a beaker containing deionized water, boiled for 4 min, and then filtered and washed with water, and this process is repeated 3 times to ensure that the surface ash is completely cleaned; then the granular coconut shell activated carbon after water washing is placed in a 2.5 mol / L hydrochloric acid solution at 48°C for 10 min, and the solution is stirred during the soaking process; then the solution is filtered and the activated carbon particles are washed with water until the washing water pH is 7; then the activated carbon particles after acid soaking and water washing are placed in an oven and dried at 120°C for 9 h; finally, the treated granular coconut shell activated carbon is sealed and stored for use;

[0151] The pretreatment process of the expanded graphite is as follows: first, the prepared expanded graphite is placed in a beaker containing distilled water, and ultrasonic treatment is carried out at room temperature for 10 min, and then washed with water for several times until the color of the washing water changes from light yellow to colorless after standing; then the washed expanded graphite is dried in an oven, the drying temperature is 60°C, and the drying time is 3.5 h; finally, the treated expanded graphite is placed in a stoppered reagent bottle for standby.

[0152] 2) Preparation of phosphoric acid-aluminum hydroxide-chitosan colloidal solution

[0153] The same as example 1, except that the aluminum hydroxide powder is added to the phosphoric acid aqueous solution, the stirring time is 17 min, and then the chitosan is added to the emulsion, and the stirring time is 23 min;

[0154] 3) Impregnation treatment of activated carbon and expanded graphite

[0155] The same as example 1, except that the amounts of activated carbon, expanded graphite, and phosphoric acid-aluminum hydroxide-chitosan colloidal solution are as follows: 2g:2g:3ml;

[0156] 2, Resource utilization of waste after ethyl acetate adsorption regeneration for methyl orange dye wastewater treatment process

[0157] (1) Microwave irradiation regeneration of activated carbon / expanded graphite composite material after adsorption saturation

[0158] 1) The process of adsorbing ethyl acetate gaseous pollutants by activated carbon / expanded graphite composite material, the process of microwave irradiation regeneration, and the process of adsorption and application are the same as example 1, and will not be described in detail;

[0159] 2) When the efficiency of microwave irradiation regeneration of activated carbon / expanded graphite composite material is less than 65%, it is determined that it is no longer suitable for adsorption treatment of volatile organic compounds, i.e. as an adsorption waste treatment.

[0160] (2) Resource utilization of waste activated carbon / expanded graphite composite material

[0161] 1) The waste of activated carbon / expanded graphite composite material after adsorption failure is added to 1wt% polyaluminum chloride solution, and is immersed at room temperature for 24h, and then is taken out from the solution and placed in a 60℃ oven for drying for 24h;

[0162] 2) A methyl orange aqueous solution with a concentration of 15g / L is prepared, 4g of the waste activated carbon / expanded graphite composite material after adsorption saturation is added to 1L of the methyl orange solution, and the solution is slowly shaken at room temperature to realize the adsorption and capture of methyl orange dye molecules by the waste activated carbon / expanded graphite composite material;

[0163] 3) To realize the efficient adsorption and capture of methyl orange dye molecules in the aqueous solution, the adsorption process control conditions of the waste activated carbon / expanded graphite composite material are as follows: the initial concentration of methyl orange is 15g / L, the pH value of the solution is controlled to be 3, the added amount of the waste activated carbon / expanded graphite composite material is 4g / 100mL, the adsorption temperature is room temperature, and the adsorption time is 20min, and the experimental results show that the decolorization rate of methyl orange is 99.6%, and the adsorption amount of methyl orange is 315mg / g.

[0164] 4) After the waste activated carbon / expanded graphite composite material adsorbs and captures methyl orange dye, it can be finally incinerated and harmlessly disposed according to the requirements for disposal of hazardous waste.

[0165] In summary, the activated carbon / expanded graphite composite material prepared by the application has excellent adsorption effect on volatile organic compounds, is suitable for microwave irradiation regeneration, and can realize the adsorption treatment of methyl orange dye wastewater after being discarded.

[0166] The above is only an exemplary specific embodiment of the present disclosure, but the protection scope of the present disclosure is not limited thereto, and any person skilled in the art can easily think of changes or replacements within the technical range disclosed by the present disclosure, which should be covered within the protection scope of the present disclosure. Therefore, the protection scope of the present disclosure should be subject to the protection scope of the claims.

Claims

1. A method for preparing an activated carbon / expanded graphite composite material for adsorbing volatile organic compounds, characterized in that, Includes the following steps: (1) Pre-treat activated carbon and expanded graphite powders by water washing and acid impregnation, and set aside for later use; (2) A phosphoric acid-aluminum hydroxide-chitosan gel solution was prepared and used as a binder to make composite microspheres; (3) Activated carbon and expanded graphite are impregnated in a phosphoric acid-aluminum hydroxide-chitosan colloidal solution to obtain a colloidal substance containing the two powders. The activated carbon / expanded graphite composite material is obtained by wet pelletizing and drying. Step (2) specifically includes: D1: Phosphoric acid with a mass concentration of 85%, deionized water, aluminum hydroxide powder, and chitosan are used. The mass ratio of the substances is as follows: Phosphoric acid: Deionized water: Aluminum hydroxide powder: Chitosan = 1:1:2:3; D2: Mix the phosphoric acid and water in a certain proportion and stir evenly to prepare a phosphoric acid aqueous solution. Then add aluminum hydroxide powder to the phosphoric acid aqueous solution and stir for 10-15 minutes to obtain a homogeneous emulsion. Then add the chitosan to the emulsion and stir thoroughly for 20-30 minutes to obtain a pale yellow gel-like solution. Step (3) specifically includes: E1: Add the activated carbon particles and the expanded graphite powder to the phosphate-aluminum hydroxide-chitosan colloidal solution, and stir thoroughly at room temperature for 20-30 minutes to ensure that the activated carbon particles and the expanded graphite powder are evenly dispersed and fully impregnated, thereby obtaining a uniformly mixed paste. E2: The spherical particles are obtained by placing the impregnated material containing activated carbon particles and expanded graphite paste in a pelletizing machine. The average particle size of the spherical particles is 0.85 cm. E3: The obtained spherical particles are placed in a muffle furnace for high-temperature heat treatment at a temperature of 550°C for 3-5 hours. After the temperature of the muffle furnace chamber cools naturally to room temperature, the spherical activated carbon / expanded graphite composite adsorbent material is obtained. The ratio of the amount of activated carbon, expanded graphite, and phosphoric acid-aluminum hydroxide powder-chitosan colloidal solution is 1-3g: 1-3g: 2-5mL. After the activated carbon / expanded graphite composite material is saturated with adsorption, it is removed from the adsorption column and regenerated by microwave irradiation.

2. The method for preparing an activated carbon / expanded graphite composite material for adsorbing volatile organic compounds according to claim 1, characterized in that, In step (1), the method for preparing expanded graphite includes the following steps: A1: The expanded graphite was prepared by an electrochemical anodic oxidation intercalation process. The main equipment used was a DC regulated power supply, a 250mL beaker used as an electrolyte cell, and a 500W microwave oven. A2: The electrochemical reactor used for the preparation of expanded graphite consists of a DC regulated power supply, an electrolytic cell, a composite anode composed of natural graphite flakes and stainless steel strips, and a ring-shaped copper mesh cathode. A3: Natural graphite flakes undergo electrochemical intercalation and microwave expansion treatment.

3. The method for preparing an activated carbon / expanded graphite composite material for adsorbing volatile organic compounds according to claim 2, characterized in that, In step A1, the main materials used in the preparation of expanded graphite include natural graphite flakes, sodium nitrate, glacial acetic acid, stainless steel anode strips with dimensions of 20cm×1cm×0.3cm, and a copper mesh cathode bent into a ring shape with a length of 20cm and a width of 8cm.

4. The method for preparing an activated carbon / expanded graphite composite material for adsorbing volatile organic compounds according to claim 2, characterized in that, In step A2, the composite anode is processed as follows: a 1.5cm×6cm cloth bag is filled with natural graphite flakes, and then a stainless steel strip is inserted into it so that the natural graphite flakes are evenly distributed around the stainless steel electrode. The annular copper mesh cathode is arranged around the anode.

5. The method for preparing an activated carbon / expanded graphite composite material for adsorbing volatile organic compounds according to claim 2, characterized in that, In step A3, the specific method for electrochemical intercalation and microwave expansion treatment of the natural graphite flakes includes the following steps: B1: To prepare a sodium nitrate solution with a concentration of 45-50 g / L, add 100-120 mL of edible vinegar to the sodium nitrate solution and stir it thoroughly to prepare a sodium nitrate-vinegar solution. B2: Add 125 mL of the sodium nitrate-acetic acid aqueous solution to a 250 mL beaker used as an electrolyte cell, turn on the DC regulated power supply switch, and control the reaction current and reaction time to 1-1.5 A and 1-2 h, respectively, to carry out the electrochemical intercalation reaction of graphite flakes at room temperature. B3: After the electrochemical intercalation reaction of the graphite flakes is completed, the power is turned off. First, the composite anode is removed, and the bag containing the graphite flakes is ultrasonically treated for 3 minutes. Then, it is thoroughly washed with water to remove the residual sodium nitrate and acetic acid substances on the surface. When the washing water is neutral, the intercalated graphite flakes are removed from the bag and placed in an oven to dry. The drying temperature is 80℃ and the time is 5-8 hours, thus obtaining expanded graphite. B4: Place 0.5g of the expanded graphite in a 500W microwave oven, turn on the microwave oven, and microwave the expanded graphite at room temperature. The microwave expansion time is controlled to be 15-20s. After the microwave expansion is completed, expanded graphite with a loose structure and worm-like morphology is obtained.

6. The method for preparing an activated carbon / expanded graphite composite material for adsorbing volatile organic compounds according to claim 1, characterized in that, The adsorption sites of the expanded graphite are removed by washing with water to remove ash from the surfaces of the activated carbon and expanded graphite powders, and by acid leaching to remove inorganic salts, heavy metals, and other adsorbed impurities from the two powders. The specific method includes the following steps: C1: Washing process: Put coconut shell activated carbon particles with an average particle size of 0.3mm into a beaker, boil them in deionized water for 3-5 minutes to remove surface ash, filter them and boil them in water again. Repeat this process 3 times. After washing, put them into a flask for later use. C2: Acid immersion process: Immerse in hydrochloric acid aqueous solution at 40-50℃ and 2-3mol / L for 10 minutes with shaking. After filtration, perform acid washing and immersion again. Repeat this process 3 times. Then wash with water until pH=6-7. After washing with water, place in an oven and dry at 120℃ for 8-12 hours. After drying, seal and store for later use.

7. The application of the activated carbon / expanded graphite composite material for adsorbing volatile organic compounds according to claims 1-6, characterized in that, The activated carbon / expanded graphite composite adsorbent material is used for the adsorption and treatment of volatile organic compounds, and the application method is detailed below. Includes the following steps: H1: Within the VOCs generator, a heating device and an air pump are used to blow VOCs gas out of the generator along with the airflow. The heating device temperature is controlled within the range of 25-50℃, and the air pump flow rate is 0.2-1.0 mL / min. To control the concentration of VOCs entering the adsorption column, another air pipeline is designed, which uses an air pump to blow air into the pipeline, allowing it to mix with the VOCs gas in a gas mixing chamber. A baffle is designed within the gas mixing chamber, and the VOCs concentration at the inlet of the adsorption column is controlled at 140-170 mg / m³. 3 ; H2: A three-way sampling port is provided in front of the adsorption column, and the adsorption column is filled with 10g of the activated carbon / expanded graphite composite material. When VOCs gas enters the inlet below the adsorption column, its initial inlet concentration is sampled and measured. As the adsorption of the activated carbon / expanded graphite composite material proceeds, the VOCs gas entering the adsorption column is adsorbed and captured by the adsorption material. When the VOCs concentration at the outlet of the adsorption column is no longer zero, the gas at the outlet is introduced into the tail gas treatment device, and the tail gas is absorbed and treated with a sodium hypochlorite aqueous solution with a mass concentration of 10%.

8. The application of the activated carbon / expanded graphite composite material for adsorbing volatile organic compounds according to claim 7, characterized in that, The activated carbon / expanded graphite composite adsorbent material, after being discarded, is used for the adsorption and treatment of methyl orange wastewater. The specific process includes the following steps: S1: The waste material after the adsorption failure of the activated carbon / expanded graphite composite material is added to a 1wt% polyaluminum chloride solution and soaked at room temperature for 24 hours. Then the waste material is taken out of the solution and placed in a 60℃ oven to dry for 24 hours. S2: Prepare a methyl orange aqueous solution with a concentration of 12-18 g / L. Add 3-5 g of the activated carbon / expanded graphite composite material after it has been saturated with adsorption to 100 mL of methyl orange solution and shake the solution slowly at room temperature. S3: The adsorption process control conditions of the activated carbon / expanded graphite waste composite material are as follows: the initial concentration of methyl orange is 15 g / L, the solution pH is controlled at 3-5, the amount of activated carbon / expanded graphite waste composite material added is 4 g / 100 mL, the adsorption temperature is room temperature, and the adsorption time is 20 min.

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