Preparation method and application of carbon material for carbon dioxide-waste oil double-effect adsorption

Abstract

The invention discloses a preparation method and application of a carbon material for carbon dioxide-waste oil double-effect adsorption. The preparation method comprises the following steps: 1, grinding and mixing initial biochar and an activating agent, and then heating; 2, carrying out oxidation modification on the obtained porous structure biochar; and 3, carrying out plasma modification on the oxidation modified carbon material. The porous structure biochar is subjected to coupling modification of oxidation modification and plasma modification, the carbon material is subjected to pore structure modification, and particularly the micropore proportion is increased, so that an adsorption porous structure adapting to two different molecular types of CO2 and waste oil is formed on the surface of the carbon material; meanwhile, functional groups capable of enhancing CO2 adsorption and waste oil adsorption are introduced to the surface of the carbon material through surface modification, so that the carbon material has excellent CO2 and waste oil double-effect adsorption capacity.

Description

Technical Field

[0001] The invention belongs to the technical field of pollutant adsorption, and specifically relates to a method for preparing a carbon material for dual-effect adsorption of carbon dioxide and waste oil and its application. Background Art

[0002] Since the Industrial Revolution, global carbon emissions have continued to increase, putting tremendous pressure on the natural environment. As the main greenhouse gas, excessive emissions of carbon dioxide (CO2) are one of the key causes of global warming, further leading to melting glaciers, rising sea levels, and frequent extreme weather and natural disasters, which seriously threaten the human living environment. In addition, my country's oil refining industry, as the world's largest emitter of waste oil and CO2, faces the dual challenges of reducing pollution and carbon emissions while meeting energy needs. How to coordinate the treatment of waste oil and CO2 emissions has become an important issue that the oil refining industry needs to solve urgently.

[0003] One of the effective means to reduce greenhouse gas emissions is to capture CO2. The main capture processes currently include pre-combustion capture, post-combustion capture and oxygen-enriched combustion. Among them, post-combustion capture technology targets CO2 in flue gas after fossil fuel combustion and has been widely used in industrial fields such as power plants. Adsorption has become one of the key methods for CO2 capture due to its high efficiency and environmental protection. Among solid adsorbents, carbon materials occupy an important position in industrial applications due to their advantages of high specific surface area, high porosity and strong regeneration ability.

[0004] The adsorption method not only performs well in the field of CO2 capture, but also attracts much attention in the field of oil-water separation due to its convenience, rapidity and no secondary pollution. However, traditional waste oil adsorbents such as activated alumina, activated carbon and zeolite generally have limited adsorption capacity, which limits the breadth and depth of their practical applications.

[0005] Carbon materials are widely used in adsorption-related fields due to their chemical stability, thermal stability and excellent adsorption performance. The core methods for preparing high-efficiency carbon materials include crushing and screening of raw materials, carbonization and activation treatment. The activation process is mainly divided into physical activation, chemical activation and coupled activation: 1. Physical activation: Through an atmosphere such as water vapor, CO2 or air, water gas reacts with the raw materials to generate volatile gases, thereby etching the raw materials to form a porous structure. 2. Chemical activation: Chemical reagents (such as KOH, ZnCl, etc.) are used to react with the raw materials to generate carbonates or metal elements, which are inserted into the carbon layer to form pores. 3. Coupled activation: Combine physical activation and chemical activation to optimize pore-forming efficiency. However, although traditional activated carbon materials have excellent specific surface area, their adsorption capacity and selectivity are still limited. Especially in the field of multifunctional adsorption materials that simultaneously adsorb CO2 and waste oil, existing technologies cannot meet industrial needs. This technical bottleneck urgently needs to be broken through through innovative material design and process improvements. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preparing a carbon material for dual-effect adsorption of carbon dioxide and waste oil and its application, by regulating the surface pore size, shape and surface groups of the carbon material, to achieve efficient adsorption of two different molecular types (CO2 and waste oil), thereby improving the flexibility and adaptability of the material in treating wastewater and air pollution.

[0007] In a first aspect, the present invention provides a method for preparing a carbon material for dual-effect adsorption of carbon dioxide and waste oil, which comprises the following steps:

[0008] Step 1: Grind and mix the initial biochar and the activator, and then heat them at an activation temperature of 400° C. to 550° C. to obtain porous biochar.

[0009] Step 2: Oxidatively modify the porous biochar: add potassium persulfate (K2S2O8), phosphorus pentoxide (P2O5) and the porous biochar obtained in step 1 to concentrated sulfuric acid, and stir the reaction at 80°C to 120°C; separate the solid phase product to obtain an oxidatively modified carbon material.

[0010] Step 3: Plasma modification of the oxidized modified carbon material. Plasma discharge is performed on the oxidized modified carbon material in a plasma reactor; the discharge atmosphere is a mixture of argon and nitrogen; the discharge voltage is 25 kV to 50 kV; and the discharge time is 30 min to 60 min.

[0011] Preferably, the preparation process of the initial biochar in step 1 is: wash and dry the biomass raw material; the drying temperature is 80°C to 120°C, and the drying time is 10h to 12h. The biomass raw material is crushed and sieved through an 80-mesh to 120-mesh sieve to ensure uniform particle size. The obtained biomass powder is calcined. The calcination conditions are: in a nitrogen atmosphere, the nitrogen flow rate is 80mL / min to 120mL / min, heated to 500°C to 600°C at a heating rate of 3 to 8°C / min, and kept warm for 1h to 1.5h.

[0012] Preferably, the activator in step 1 is one or more of potassium hydroxide (KOH) and sodium amide (NaNH2); the mass ratio of the porous biochar to the activator is 1:(1-2). More preferably, the activator is a mixture of potassium hydroxide and sodium amide; the mass ratio of potassium hydroxide to sodium amide in the mixture is 1:1.

[0013] Preferably, the heating condition in step 1 is to heat to 550°C activation temperature at a heating rate of 3°C / min to 8°C / min in a nitrogen atmosphere (flow rate 80mL / min to 120mL / min), and keep warm for 1h to 1.5h. After the reaction is completed, neutralize to neutral with 0.5M to 1M hydrochloric acid and deionized water, and dry at 60°C to 80°C for 8h to 12h.

[0014] Preferably, in step 2, the mass ratio of the porous biochar, potassium persulfate, and phosphorus pentoxide is 1:(1-2):(1-2);

[0015] Preferably, the amount of carbon material used in step 2 is 1 / 60 g / ml relative to concentrated sulfuric acid.

[0016] Preferably, the stirring speed of the stirring reaction in step 2 is 100 r / min to 150 r / min; the stirring reaction time is 12 h to 20 h. After the reaction is completed, cool it, slowly add deionized water, and stir evenly. More preferably, after the stirring reaction, neutralize it with deionized water until the supernatant is neutral, filter it with suction and dry it at 60 to 80 ° C for 8 to 12 h.

[0017] Preferably, the discharge voltage in step three is 30 kV.

[0018] Preferably, in the discharge atmosphere of step three, the flow rate of the mixed gas of argon and nitrogen is 30 mL / min to 120 mL / min; the volume ratio of argon to nitrogen is (7 to 9):(1 to 3).

[0019] In a second aspect, the present invention provides a carbon material for dual-effect adsorption of carbon dioxide and waste oil; the carbon material is prepared by the aforementioned preparation method.

[0020] In a third aspect, the present invention provides an application of the aforementioned carbon material in carbon dioxide-waste oil dual-effect adsorption

[0021] In a fourth aspect, the present invention provides a carbon dioxide-waste oil dual-effect adsorption method, which comprises the following steps:

[0022] In step (1), the carbon material as described in claim 8 is used to simultaneously adsorb carbon dioxide and waste oil.

[0023] Step (2) placing the adsorption saturated carbon material in an organic solvent to extract and recover the waste oil.

[0024] Step (3) The carbon material extracted in step 2 is heated to 140-180° C. and kept warm for 1.5-2.5 hours to desorb carbon dioxide.

[0025] Preferably, the organic solvent is acetone or ethanol, preferably acetone.

[0026] Preferably, the temperature for desorption of carbon dioxide in step (3) is 160°C.

[0027] Preferably, the environment for desorption of carbon dioxide in step (3) is vacuum.

[0028] The present invention has the following beneficial effects:

[0029] 1. The present invention couples oxidation modification and plasma modification on the porous biochar, modifies the pore structure of the carbon material, especially increases the proportion of micropores, so that the surface of the carbon material forms an adsorption porous structure that is suitable for two different molecular types of CO2 and waste oil, so that the carbon material has excellent dual-effect adsorption capacity of CO2 and waste oil.

[0030] 2. The present invention performs surface modification of the porous biochar by combining oxidation modification and plasma modification. The oxidation modification can provide modification sites for plasma modification, thereby introducing functional groups that can enhance both CO2 adsorption and waste oil adsorption to the surface of the carbon material, thereby synergistically improving the adsorption capacity of the prepared carbon material for waste oil and CO2.

[0031] 3. The present invention can achieve independent desorption of CO2 and waste oil through extraction and heating treatment, thereby ensuring the recycling performance of the dual-effect adsorption carbon material. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 It is a scanning electron microscope comparison image of the carbon materials prepared in Example 1 of the present invention and Comparative Example 1 (part a corresponds to the scanning electron microscope image of Comparative Example 1, and part b corresponds to the scanning electron microscope image of Example 1).

[0033] Figure 2 TEM comparison images of the carbon material prepared in Example 1 of the present invention at different magnifications and the carbon material prepared in Comparative Example 1 (part a corresponds to the 100nm TEM image of Comparative Example 1, and parts b, c, and d correspond to the 100nm, 10nm, and 5nm TEM images of Example 1). DETAILED DESCRIPTION

[0034] The present invention is further described below.

[0035] Example 1

[0036] A method for preparing a carbon material for dual-effect adsorption of carbon dioxide and waste oil comprises the following steps:

[0037] Step 1: Raw material pretreatment.

[0038] Wheat straw was selected as the biomass raw material. The surface of the straw was washed with deionized water to remove the surface ash and impurities, and then placed in an oven at 105°C for drying overnight. The dried straw was crushed to about 100 mesh in a grinder, placed in a quartz boat and placed in a tubular furnace. The heating rate was controlled at 5°C / min, and the temperature was raised to 550°C and maintained for 1 hour. After the temperature was naturally cooled to room temperature, it was taken out to obtain the pretreated biochar sample.

[0039] In this embodiment, the calcination gas atmosphere is nitrogen.

[0040] In some other embodiments, the biomass raw material may also be bamboo charcoal or coconut shell.

[0041] Step 2: Prepare porous biochar by chemical activation method.

[0042] Weigh a certain mass of the pretreated wheat straw powder sample prepared in step 1, and then weigh twice the mass of the biochar sample of sodium amide, mix the two materials and grind them in a mortar until they are evenly mixed. Transfer the evenly mixed sample to a quartz boat, put it in a tube furnace, heat it to an activation temperature of 550°C at a heating rate of 5°C / min under a nitrogen atmosphere and keep it for 1h, take it out after cooling to room temperature, neutralize it with 1M HCl solution and deionized water to neutrality, and dry it in a 60°C oven overnight to obtain a biochar with a porous structure.

[0043] In this embodiment, the pretreated wheat straw powder sample weighed is 1.0 g, sodium amide (NaNH2) is used as an activator, the mixing and grinding time is 30 min; 1M HCl solution is used as a neutralizer.

[0044] In some other embodiments, KOH may also be used as the activating agent.

[0045] Step 3: Oxidative modification of porous biochar.

[0046] Measure a certain amount of concentrated sulfuric acid in a three-necked flask, weigh a certain amount of K2S2O8, P2O5, and the porous structure biochar obtained in step 2, add them to the three-necked flask and stir evenly. Keep the stirring speed at 120r / min, keep the reaction temperature at 120℃, and react for 18 hours. After the reaction is completed, cool to room temperature, slowly move the three-necked flask into 5L deionized water, and stir evenly. Use deionized water to wash and neutralize continuously until the supernatant is neutral, filter and dry to obtain the oxidized modified biochar material.

[0047] In this step, the oxidation modification can further introduce oxygen-containing groups to improve the material's adsorption performance for waste oil and CO2. At the same time, the increase in oxygen-containing functional groups provides sites for subsequent plasma doping.

[0048] In this embodiment, mixing and heating are achieved by a magnetic stirrer.

[0049] In this embodiment, the mass of the porous structure biochar weighed is 2 g, the mass of K2S2O8 is 2 g, and the mass of P2O5 is 2 g.

[0050] Step 4: Plasma modification of the biochar material obtained in step 3.

[0051] Weigh a certain mass of oxidatively modified biochar material and spread it in a tubular DBD reactor (dielectric barrier discharge reactor). Insert a small amount of quartz wool at the outlet of the DBD reactor to prevent the powder from overflowing. Continuously introduce a mixed gas of argon and nitrogen (Ar / N2=1 / 2) into the DBD reactor as the discharge atmosphere, and keep the gas flow rate at 60ml / min. Then connect the electrode for plasma discharge, detect the discharge voltage through an oscilloscope, keep the discharge voltage at 30kV, and discharge for 1h. Obtain plasma-modified biochar material (denoted as BC-P550).

[0052] In this step, plasma surface modification utilizes low-temperature plasma technology to introduce functional groups that enhance CO2 adsorption and waste oil adsorption on the material surface, and pore structure modification, especially the proportion of micropores, by regulating discharge parameters (such as voltage, time, atmosphere, etc.).

[0053] In this embodiment, the mass of the biochar material weighed is 0.3 g.

[0054] The biochar material obtained in this embodiment is successively subjected to oxidation modification and plasma modification, and the special surface structure and pore structure formed on the biochar material can simultaneously achieve the adsorption of carbon dioxide and waste oil. The waste oil in this embodiment specifically refers to waste pump oil or waste oil in refinery wastewater.

[0055] Comparative Example 1

[0056] A method for preparing a carbon material. The difference between this comparative example and Example 1 is that only steps one and two are performed, and steps three and four are not performed, to obtain an unmodified biochar material (denoted as BC).

[0057] The carbon materials obtained in Example 1 and Comparative Example 1 were characterized by SEM and TEM. Figure 1 As shown by Figure 1 It can be seen that there are fewer pores on the surface of the material before oxidation modification and plasma modification, while the number of pores increases significantly after modification. Figure 2 As shown, from Figure 2 It can be seen that the carbon material subjected to oxidation modification and plasma modification in Example 1 produces uniformly distributed worm-like nanopores having a very rich pore structure.

[0058] Comparative Example 2

[0059] A method for preparing a carbon material. The difference between this comparative example and Example 1 is that only steps one, two and three are performed, and step four is not performed, to obtain a biochar material (denoted as BC-O) that has only undergone oxidation modification but not plasma modification.

[0060] The oil absorption performance of the carbon material prepared in Comparative Example 1 was measured, with waste pump oil as the simulated pollutant. The adsorption method is from GB / T 3780.2-2017. The small beaker containing the oil to be tested and the dropper are placed on a balance and weighed, which is recorded as the initial mass. Weigh 0.3g of the material to be tested and place it on a culture dish. Use a dropper to drip oil onto the sample. Each drop is 4-5 drops. After adding, use a spatula to blend, stir, and press to make the oil penetrate into the sample. When the oil and the sample form a mass, each drop of oil must be fully ground with a spatula. When a semi-plastic paste with uniform consistency is formed, it is just not cracked or broken, can adhere to the surface of the culture medium, and there is no oil stain on the plate, it is the end point. Weigh the mass of the small beaker and the dropper containing the oil to be tested. The ratio of the difference between this mass and the initial mass to the mass of the material to be tested is the oil absorption of the material.

[0061] The oil absorption capacity of the carbon material prepared in Comparative Example 1 was tested. Three portions of the material were weighed separately, and the oil absorption of the material was measured using the above method. The three results were averaged to obtain the oil absorption of the material. The test results showed that the oil absorption of the three portions of the material was above 16 g / g, and it was considered that the material had good oil absorption performance. Compared with the adsorption capacity of the unmodified carbon material prepared in Comparative Example 1, it was found that the saturated oil absorption of the material before modification was only 11 g / g, and the material after oxidation modification increased by about 50% compared with that before modification.

[0062] The oil absorption performance and CO2 adsorption performance of the carbon material prepared in Example 1 were measured, and the CO2 adsorption capacity of the modified material was 4.99 mmol / g, and the oil absorption capacity reached 18 g / g. It can be seen that plasma modification not only improves the CO2 adsorption capacity of the carbon material, but also further improves the oil absorption capacity of the carbon material. Therefore, the carbon material prepared in Example 1 has a better prospect in the application of simultaneous adsorption of CO2 and waste oil.

[0063] The biochar materials obtained in Example 1, Comparative Examples 1 and 2 were characterized, and the surface functional groups and pore structures of the materials were analyzed, as follows:

[0064] The chemical element composition of the three biochar materials provided in Example 1, Comparative Examples 1 and 2 was measured by an organic element analyzer, and the results are shown in Table 1 below. According to the results in Table 1, it can be observed that after oxidative modification, the oxygen content of the biochar material has increased significantly, indicating that oxidative modification can significantly increase the number of oxygen-containing functional groups, which is beneficial to the adsorption of waste oil. After plasma modification, the oxygen content of the material has decreased, and at the same time, the nitrogen content has increased significantly, indicating that while plasma modification retains most of the oxygen-containing functional groups, some of the oxygen-containing functional groups are used as plasma doping sites and are consumed during the plasma modification process, thereby introducing more nitrogen-containing functional groups that are beneficial to adsorption.

[0065] Table 1 Bulk chemical element distribution of biochar modified by different methods

[0066]

[0067] The pore structures of the three materials provided in Example 1, Comparative Examples 1 and 2 were further characterized and analyzed by using a BSD-PS1 / 2 fully automatic specific surface area porosity analyzer. BET 、Kong Rong V t And the micropore ratio V mic / V t As shown in Table 2 below. By analyzing the data in Table 2, it can be seen that the specific surface area and pore volume of the material after oxidation modification are improved to a certain extent, but the proportion of micropores is slightly reduced. This is because during the oxidation modification process, more mesoporous holes are formed on the surface of the material, which are conducive to the adsorption of waste oil. After plasma modification, the total pore volume V t The micropore volume V mic and micropore ratio V mic / V t The reason is that during the plasma modification process, some macropores collapse to form micropores and mesopores, thereby enhancing the adsorption performance of carbon dioxide and waste oil at the same time. Through further characterization of the pore size distribution of the material, it was found that the pore size of the plasma-modified material is mainly concentrated at 0.59nm and 0.8nm. These narrow micropores can serve as effective adsorption sites for carbon dioxide, which is conducive to the adsorption of carbon dioxide by the material.

[0068] Table 2 Pore structure of biochar modified by different methods

[0069]

[0070] Example 2

[0071] A method for preparing a carbon material for dual-effect adsorption of carbon dioxide and waste oil, the difference between this embodiment and embodiment 1 is that the activation temperature in step 2 is different; in this embodiment, step 2 is heated to an activation temperature of 400°C at a heating rate of 5°C / min under a nitrogen atmosphere and maintained for 1 hour, and then taken out after cooling to room temperature. The carbon material prepared in this embodiment is recorded as BC-P400.

[0072] Example 3

[0073] A method for preparing a carbon material for dual-effect adsorption of carbon dioxide and waste oil, the difference between this embodiment and embodiment 1 is that the activation temperature in step 2 is different; in this embodiment, step 2 is heated to an activation temperature of 450°C at a heating rate of 5°C / min under a nitrogen atmosphere and maintained for 1 hour, and then taken out after cooling to room temperature. The carbon material prepared in this embodiment is recorded as BC-P450.

[0074] Example 4

[0075] A method for preparing a carbon material for dual-effect adsorption of carbon dioxide and waste oil, the difference between this embodiment and embodiment 1 is that the activation temperature in step 2 is different; in this embodiment, step 2 is heated to an activation temperature of 500°C at a heating rate of 5°C / min under a nitrogen atmosphere and maintained for 1 hour, and then taken out after cooling to room temperature. The carbon material prepared in this embodiment is recorded as BC-P500.

[0076] The carbon materials prepared in Examples 1-4 were tested for CO2 adsorption using a fully automatic specific surface area porosity analyzer. During the test, the material was first pretreated, i.e., vacuum drying and degassing at 160°C for 6 hours. The test temperature was 25°C and the pressure range was 0-1 bar. The test results are listed in Table 3 below.

[0077] Table 3 CO2 adsorption capacity of biochar at different activation temperatures (25℃, 1bar)

[0078]

[0079] It can be observed from Table 3 that the biochar sample activated at 550°C has the highest saturated adsorption capacity of CO2 at 25°C, reaching 4.52 mmol / g, indicating that within a certain temperature range, the adsorption capacity of biochar material for CO2 increases with the increase of activation temperature.

[0080] The specific surface area and micropore ratio of the carbon materials obtained in Examples 1-4 were characterized to further verify the influence of the specific surface area and micropores of the materials on the adsorption capacity of CO2.

[0081] The specific surface area and pore structure of the material were measured by a BSD-PS1 / 2 fully automatic specific surface area porosity analyzer. The degassing conditions were set to vacuum degassing at 160°C for 6 hours, and then the N2 adsorption / desorption experiment was carried out in a liquid nitrogen environment at 77K. Table 4 below shows the test results of the specific surface area and micropore ratio of the modified biochar at different temperatures.

[0082] Table 4 Specific surface area and micropore proportion of biochar at different activation temperatures

[0083]

[0084] It can be observed from Table 4 that the specific surface area of ​​the biochar sample activated at 550°C is the largest, but the micropore ratio of the biochar sample prepared at 500°C is the highest. According to previous literature, when the ratio of the pore size to the molecular dynamics diameter of the adsorbed substance is between 1.7-3.0, the adsorption capacity of the pores to the adsorbate reaches the maximum. The molecular dynamics diameter of CO2 is 0.33nm, so the adsorption performance of carbon dioxide mainly comes from micropores. The higher the micropore ratio of the material, the stronger the adsorption performance of the material for CO2 should be. Therefore, although the higher the activation temperature, the higher the specific surface area of ​​the material, too high a temperature will cause the micropore ratio of the material to decrease, thereby affecting the adsorption of CO2 by the material. Therefore, 550°C is selected as the optimal activation temperature.

[0085] Example 5

[0086] A method for preparing a carbon material for dual-effect adsorption of carbon dioxide and waste oil. The difference between this embodiment and embodiment 1 is that the discharge gas flow rate in step 4 is different; in this embodiment, in step 4, in a mixed gas atmosphere of argon and nitrogen, the gas flow rate is maintained at 30 mL / min, the discharge voltage is maintained at 30 kV, the discharge is performed for 60 minutes, and the discharge is taken out after cooling to room temperature. The carbon material prepared in this embodiment is recorded as BC-PQ 30 .

[0087] Example 6

[0088] A method for preparing a carbon material for dual-effect adsorption of carbon dioxide and waste oil. The difference between this embodiment and embodiment 1 is that the discharge gas flow rate in step 4 is different; in this embodiment, in step 4, in a mixed gas atmosphere of argon and nitrogen, the gas flow rate is maintained at 90mL / min, the discharge voltage is maintained at 30kV, the discharge is performed for 60min, and the carbon material is taken out after cooling to room temperature. The carbon material prepared in this embodiment is recorded as BC-PQ 90 .

[0089] Example 7

[0090] A method for preparing a carbon material for dual-effect adsorption of carbon dioxide and waste oil. The difference between this embodiment and embodiment 1 is that the discharge gas flow rate in step 4 is different; in this embodiment, in step 4, in a mixed gas atmosphere of argon and nitrogen, the gas flow rate is maintained at 120mL / min, the discharge voltage is maintained at 30kV, the discharge is performed for 60min, and the discharge is taken out after cooling to room temperature. The carbon material prepared in this embodiment is recorded as BC-PQ 120 .

[0091] The carbon materials prepared in Examples 1, 8, 9, and 10 were tested for CO2 and N2 adsorption using a fully automatic specific surface area porosity analyzer. The adsorption isotherms of single-component CO2 and N2 were fitted based on the dual-site Langmuir-Freundlich model (DSLF). The adsorption selectivity of the CO2 / N2 (15 / 85, v / v) mixed gas at 25°C was predicted using IAST. The results show that the CO2 / N2 adsorption selectivity trend is: BC-P550 (Example 1) > BC-PQ 90 (Example 6) > BC-PQ 30 (Example 5) > BC-PQ 120 (Example 7) > BC (Comparative Example 1). When the Ar / N2 gas flow rate is 60 mL / min, the CO2 / N2 adsorption selectivity is the highest

[0092] After determining the optimal modified gas flow rate conditions, the discharge voltage conditions for plasma modification are adjusted.

[0093] Example 8

[0094] A method for preparing a carbon material for dual-effect adsorption of carbon dioxide and waste oil. The difference between this embodiment and embodiment 1 is that the discharge voltage in step 4 is different. In this embodiment, step 4 is carried out under a mixed gas atmosphere of argon and nitrogen, with a gas flow rate of 60 mL / min, a discharge voltage of 25 kV, and a discharge of 60 min. The carbon material prepared in this embodiment is recorded as BC-PU 25 .

[0095] Example 9

[0096] A method for preparing a carbon material for dual-effect adsorption of carbon dioxide and waste oil. The difference between this embodiment and embodiment 1 is that the discharge voltage in step 4 is different; in this embodiment, step 4 is carried out in a mixed gas atmosphere of argon and nitrogen, with a gas flow rate of 60 mL / min, a discharge voltage of 40 kV, and a discharge of 60 min. The carbon material prepared in this embodiment is recorded as BC-PU 40 .

[0097] Example 10

[0098] A method for preparing a carbon material for dual-effect adsorption of carbon dioxide and waste oil. The difference between this embodiment and embodiment 1 is that the discharge voltage in step 4 is different. In this embodiment, step 4 is carried out under a mixed gas atmosphere of argon and nitrogen, with a gas flow rate of 60 mL / min, a discharge voltage of 50 kV, and a discharge time of 60 min. The carbon material prepared in this embodiment is recorded as BC-PU 50 .

[0099] The carbon materials prepared in Examples 1, 8, 9, and 10 were tested for CO2 and N2 adsorption using a fully automatic specific surface area porosity analyzer. The adsorption isotherms of single-component CO2 and N2 were fitted based on the dual-site Langmuir-Freundlich model (DSLF). The adsorption selectivity of the CO2 / N2 (15 / 85, v / v) mixed gas at 25°C was predicted using IAST. The results show that the trend followed by the CO2 / N2 selectivity is: BC-P550 (Example 1) > BC-PU 25 (Example 8) > BC-PU 40 (Example 9) > BC-PU 50 (Example 10) Therefore, it is believed that the discharge voltage of 30 kV in Example 1 is the optimal voltage condition for plasma modification.

Claims

1. A method for preparing a carbon material for dual-effect adsorption of carbon dioxide and waste oil, characterized in that: The following steps are involved: Step 1: grind and mix the initial biochar and the activator, and heat them at an activation temperature of 400° C. to 550° C. to obtain a porous biochar; Step 2, oxidatively modifying the porous biochar: adding potassium persulfate, phosphorus pentoxide and the porous biochar obtained in step 1 to concentrated sulfuric acid, stirring and reacting at 80° C. to 120° C.; separating the solid phase product to obtain an oxidatively modified carbon material; Step three: Plasma modifying the oxidized modified carbon material; performing plasma discharge on the oxidized modified carbon material in a plasma reactor; the discharge atmosphere is a mixture of argon and nitrogen; the discharge voltage is 25kV to 50kV; and the discharge time is 30min to 60min.

2. The method for preparing a carbon material for dual-effect carbon dioxide-waste oil adsorption according to claim 1, characterized in that: The preparation process of the initial biochar in step one is: washing and drying the biomass raw materials; crushing and sieving the biomass raw materials; calcining the obtained biomass powder; the activator in step one is one or more of potassium hydroxide and sodium amide; the mass ratio of the porous structure biochar to the activator is 1: (1~2).

3. The method for preparing a carbon material for dual-effect carbon dioxide-waste oil adsorption according to claim 1, characterized in that: The discharge voltage in step three is 30 kV.

4. The method for preparing a carbon material for dual-effect carbon dioxide-waste oil adsorption according to claim 1, characterized in that: The heating condition in step 1 is to heat to an activation temperature of 550° C. at a heating rate of 3° C. / min to 8° C. / min under a nitrogen atmosphere.

5. The method for preparing a carbon material for dual-effect carbon dioxide-waste oil adsorption according to claim 1, characterized in that: In step 2, the mass ratio of porous biochar, potassium persulfate and phosphorus pentoxide is 1:(1-2):(1-2).

6. The method for preparing a carbon material for dual-effect carbon dioxide-waste oil adsorption according to claim 1, characterized in that: The stirring speed of the stirring reaction in step 2 is 100 r / min to 150 r / min; the stirring reaction time is 12 h to 20 h.

7. The method for preparing a carbon material for dual-effect carbon dioxide-waste oil adsorption according to claim 1, characterized in that: In the discharge atmosphere of step three, the flow rate of the mixed gas of argon and nitrogen is 30 mL / min to 120 mL / min; the volume ratio of argon and nitrogen is (7 to 9):(1 to 3).

8. A carbon material for dual-effect adsorption of carbon dioxide and waste oil; characterized in that: Prepared by the preparation method as claimed in claim 1.

9. Use of the carbon material as claimed in claim 8 in dual-effect adsorption of carbon dioxide and waste oil.

10. A carbon dioxide-waste oil dual-effect adsorption method, characterized in that: The following steps are involved: Step (1) using the carbon material as claimed in claim 8 to simultaneously adsorb carbon dioxide and waste oil; Step (2) placing the adsorption saturated carbon material in an organic solvent to extract and recover the waste oil; Step (3) The carbon material extracted in step 2 is heated to 140-180° C. and kept warm for 1.5-2.5 hours to desorb carbon dioxide.

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