CN110368897B - Coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area as well as preparation method and application thereof - Google Patents

Coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area as well as preparation method and application thereof Download PDF

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CN110368897B
CN110368897B CN201910636718.2A CN201910636718A CN110368897B CN 110368897 B CN110368897 B CN 110368897B CN 201910636718 A CN201910636718 A CN 201910636718A CN 110368897 B CN110368897 B CN 110368897B
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porous carbon
coal tar
nitrogen
surface area
specific surface
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CN110368897A (en
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王晓婷
朱博文
余谟鑫
张晨
蔡英健
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Anhui University of Technology AHUT
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    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/0203—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising compounds of metals not provided for in B01J20/04
    • B01J20/0259—Compounds of N, P, As, Sb, Bi
    • B—PERFORMING OPERATIONS; TRANSPORTING
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    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/02—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material
    • B01J20/20—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof comprising inorganic material comprising free carbon; comprising carbon obtained by carbonising processes
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/28—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties
    • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J20/28057—Surface area, e.g. B.E.T specific surface area
    • B01J20/28064—Surface area, e.g. B.E.T specific surface area being in the range 500-1000 m2/g
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
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    • B01J20/28054—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof characterised by their form or physical properties characterised by their surface properties or porosity
    • B01J20/28057—Surface area, e.g. B.E.T specific surface area
    • B01J20/28066—Surface area, e.g. B.E.T specific surface area being more than 1000 m2/g
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
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    • C02F1/28—Treatment of water, waste water, or sewage by sorption
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    • C—CHEMISTRY; METALLURGY
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    • C02F2101/30—Organic compounds
    • C02F2101/34—Organic compounds containing oxygen
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/30—Organic compounds
    • C02F2101/38—Organic compounds containing nitrogen
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2101/00—Nature of the contaminant
    • C02F2101/30—Organic compounds
    • C02F2101/40—Organic compounds containing sulfur

Abstract

The invention discloses coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area, a preparation method and application thereof, belonging to the field of wastewater adsorbents; in the preparation process of the porous carbon, coal tar is used as a carbon source, calcium oxide is used as a template, potassium hydroxide is used as an activating agent to prepare porous carbon, and the surface of the porous carbon is subjected to ethylenediamine immersion modification; the obtained porous carbon has a particle size of more than 2000m2The specific surface area is/g, the surface is rich in nitrogen functional groups, and the acid dye in the wastewater can be adsorbed; the method has the advantages of low operation cost, simple operation and stable operation, achieves the aim of efficiently removing the dye, and can realize the deep treatment and standard discharge of the dye wastewater at low cost.

Description

Coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area as well as preparation method and application thereof
Technical Field
The invention belongs to the technical field of porous carbon material preparation, and particularly relates to coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area, and a preparation method and application thereof.
Background
During the production and use of the dye, about 10-20% of the dye is discharged with the wastewater. Some dyes can enter human body through food chain, causing cell carcinogenesis and teratogenesis, so that the dye waste water brings harm to environment and human health. Common methods for treating dye wastewater at home and abroad include physical methods, chemical methods and biological methods. The adsorption method has the advantages of simple operation, good performance of treating pollutants under mild conditions, and wide application in dye wastewater treatment. The adsorbent is the core of the adsorption technology. The activated carbon has the advantages of developed pore structure, large specific surface area, abundant functional groups and the like, and is most widely used as an adsorbent in a water treatment process. However, since the dye has a large molecular size and is difficult to enter the microporous part of the activated carbon, the microporous activated carbon has a poor adsorption effect on the dye.
Disclosure of Invention
The invention aims to provide coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area, which has ultrahigh specific surface area and also contains a plurality of nitrogen-containing functional groups on the surface.
The invention also aims to provide a preparation method of the coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area.
The invention also aims to provide the application of the coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area in dye adsorption.
In order to achieve the technical purpose, the technical scheme adopted by the invention is as follows:
the first technical scheme is as follows:
the coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area contains abundant micropores, small holes and mesopores; the surface of the material contains nitrogen-containing functional groups; the specific surface area exceeds 2000m2/g。
As a further improvement of the present invention, the nitrogen-containing functional group is C-N-C, N- (C)3And C-N-H.
The second technical scheme is as follows:
a preparation method of coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area comprises the steps of preparing coal tar-based porous carbon by using coal tar as a carbon source, calcium oxide as a template and potassium hydroxide as an activating agent, and then carrying out immersion modification by using ethylenediamine.
As a further improvement of the method, the mass ratio of the coal tar to the calcium oxide is 1: 1-1: 3, and the mass ratio of the coal tar to the potassium hydroxide is 1: 1-1: 5.
As a further improvement, the dosage ratio of the ethylenediamine to the coal tar-based porous carbon is 0.5-1: 2.
As a further improvement of the invention, the preparation method comprises the following steps:
(1) respectively weighing coal tar, calcium oxide and potassium hydroxide, and grinding in a grinder to fully mix the materials to obtain reactants;
(2) placing the obtained reactant into a crucible, then placing the crucible into a tubular furnace, slowly and uniformly introducing nitrogen to exhaust air in the crucible, slowly and uniformly heating to 850-900 ℃, keeping the temperature for 55-65min at constant temperature, cooling to room temperature, turning off a power supply and the nitrogen, taking out the crucible, taking out a product, grinding, pickling, placing on a magnetic stirrer, uniformly stirring, standing, washing to neutrality, drying and sieving to obtain the coal tar-based porous carbon; preferably, the flow rate of the nitrogen introducing gas is 6 mL/min; ventilating for 30min to exhaust air; in the heating process, the heating rate is preferably controlled at 5 ℃/min, and the constant temperature holding time is preferably 60 min; 2M dilute hydrochloric acid is preferably selected in the acid washing process; the magnetic stirring time is preferably 24 hours, and then the mixture is kept stand for 6 hours; the drying process is preferably carried out in a constant-temperature drying oven at 110 ℃, and the drying time is preferably 24 h.
(3) And mixing the coal tar-based porous carbon with an ethylenediamine solution, uniformly stirring, filtering, washing with water, and drying to obtain the coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area.
The third technical scheme is as follows:
the coal tar-based nitrogen-containing porous carbon with the ultrahigh specific surface area is applied to dye adsorption, and is used as an adsorbent.
As a further improvement of the present invention, the dyes are the acid dyes Congo Red and acid dye magenta.
As a further improvement of the invention, the saturated adsorption capacity of the coal tar-based nitrogen-containing porous carbon adsorbent with the ultrahigh specific surface area to Congo red and acid fuchsin reaches 3500mg/g and 2500mg/g respectively.
Compared with the prior art, the invention has the following technical effects:
coal tar is a complex mixture of high-aromatic hydrocarbons, mostly polycyclic and fused cyclic compounds with or without side chains and heterocyclic compounds containing oxygen, sulfur and nitrogen, and contains a small amount of aliphatic hydrocarbons, naphthenic hydrocarbons and unsaturated hydrocarbons, as well as coal dust, coke dust and pyrolytic carbon. The coal tar just recovered also contains about 5% of water in which various inorganic salts and other impurities are dissolved. The high-temperature coal tar contains 1 ten thousand of compounds, which can be divided into neutral hydrocarbons, acidic phenols, basic pyridine and quinoline compounds according to chemical properties. In 1819, England Garden (Garden) and Brand (Brand) found naphthalene in coal tar, the first compound found in coal tar. The subsequent scientists, mainly in the UK and Germany, have discovered successively anthracene, phenol, aniline, quinoline, pyridine, pyrene and pyrene
Figure BDA0002130569040000031
And the like. By 1972, 480 compounds were identified which were present in a total amount of 55% by mass of coal tar, including 174 neutral compounds, 63 acidic compounds, 113 basic compounds, and the balance of fused rings and oxygen and sulfur-containing heterocyclic compounds.
The coal tar is used as a carbon source, on one hand, the source is rich, the price is low, on the other hand, because the coal tar is rich in compound types, the porous carbon material prepared by using the coal tar as the carbon source contains rich functional groups, and the porous carbon material has a multifunctional group which can enable the porous carbon to have the performance of adsorbing and treating wastewater which is obviously superior to that of common activated carbon; the nitrogenous functional groups contained in the coal tar-based nitrogen-containing porous carbon have alkalinity, can effectively form chemical adsorption with acid dyes, particularly has excellent adsorption performance on the acid dyes, and an isothermal adsorption experiment shows that the maximum adsorption amount of the coal tar-based nitrogen-containing porous carbon on Congo red is 3500mg/g and the maximum adsorption amount of the coal tar-based nitrogen-containing porous carbon on acid fuchsin is 2500 mg/g. In the field of dye adsorption, the adsorption capacity of the adsorbent is high. In addition, compounds with rich varieties in coal tar can react differently in the activation process, so that pore structures with different sizes are formed, the porous carbon material has rich pore size varieties and pore size numbers, the prepared nitrogen-containing porous carbon material has ultrahigh specific surface area, and the adsorption performance of the nitrogen-containing porous carbon material is further optimized.
The invention takes the ethylenediamine as the modifier, can stabilize and enrich the variety and the number of the nitrogen-containing functional groups on the surface of the coal tar-based activated carbon, thereby further improving the adsorption performance of the coal tar-based nitrogen-containing porous carbon material.
The coal tar-based nitrogen-containing porous carbon material is mainly applied to adsorption of acid dyes, and a multilayer adsorption method is adopted for porous carbon which adsorbs the dyes. On the premise of not changing the structure of the porous carbon, the utilization rate of the existing pores of the adsorbent is increased, the total adsorption capacity of the adsorbent is increased, and compared with a regeneration technology, the method is more economic and environment-friendly, and provides a new idea for treating the adsorbent which adsorbs the dye.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed in the embodiments will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings without creative efforts.
FIG. 1 is a scanned image of coal tar-based nitrogen-containing porous carbon prepared in example 1;
FIG. 2 is a transmission diagram of the coal tar-based nitrogen-containing porous carbon prepared in example 1;
FIG. 3 is a XPS survey of coal tar based nitrogen containing porous carbon prepared in example 1;
FIG. 4 is an Nls orbital analysis of the coal tar-based nitrogen-containing porous carbon prepared in example 1;
fig. 5 is the results of the isothermal adsorption experiment (single layer adsorption) of the acid dye by the coal tar-based nitrogen-containing porous carbon prepared in example 1.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The first technical scheme is as follows:
the coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area contains abundant micropores, small holes and mesopores; the surface of the material contains nitrogen-containing functional groups; the specific surface area exceeds 2000m2/g。
As a further improvement of the present invention, the nitrogen-containing functional group is C-N-C, N- (C)3And C-N-H.
The second technical scheme is as follows:
a preparation method of coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area comprises the steps of preparing coal tar-based porous carbon by using coal tar as a carbon source, calcium oxide as a template and potassium hydroxide as an activating agent, and then carrying out immersion modification by using ethylenediamine.
As a further improvement of the method, the mass ratio of the coal tar to the calcium oxide is 1: 1-1: 3, and the mass ratio of the coal tar to the potassium hydroxide is 1: 1-1: 5.
As a further improvement, the dosage ratio of the ethylenediamine to the coal tar-based porous carbon is 0.5-1: 2.
As a further improvement of the invention, the preparation method comprises the following steps:
(1) respectively weighing coal tar, calcium oxide and potassium hydroxide, and grinding in a grinder to fully mix the materials to obtain reactants;
(2) placing the obtained reactant into a crucible, then placing the crucible into a tubular furnace, slowly and uniformly introducing nitrogen to exhaust air in the crucible, slowly and uniformly heating to 850-900 ℃, keeping the temperature for 55-65min at constant temperature, cooling to room temperature, turning off a power supply and the nitrogen, taking out the crucible, taking out a product, grinding, pickling, placing on a magnetic stirrer, uniformly stirring, standing, washing to neutrality, drying and sieving to obtain the coal tar-based porous carbon; preferably, the flow rate of the nitrogen introducing gas is 6 mL/min; ventilating for 30min to exhaust air; in the heating process, the heating rate is preferably controlled at 5 ℃/min, and the constant temperature holding time is preferably 60 min; 2M dilute hydrochloric acid is preferably selected in the acid washing process; the magnetic stirring time is preferably 24 hours, and then the mixture is kept stand for 6 hours; the drying process is preferably carried out in a constant-temperature drying oven at 110 ℃, and the drying time is preferably 24 h.
(3) And mixing the coal tar-based porous carbon with an ethylenediamine solution, uniformly stirring, filtering, washing with water, and drying to obtain the coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area.
The third technical scheme is as follows:
the coal tar-based nitrogen-containing porous carbon with the ultrahigh specific surface area is applied to dye adsorption, and is used as an adsorbent.
As a further improvement of the invention, the adsorption is carried out by a multilayer adsorption method, which comprises the following steps:
(1) adsorption of the first layer: adding the adsorbent into 800mg/L acid dye Congo red dye water with the initial concentration of 100-;
(2) and (3) adsorption of a second layer: drying the first layer of absorbent saturated with Congo red, adding into the basic dye methylene blue dye water with the initial concentration of 100-450mg/L, standing for 36h at room temperature, wherein the adding amount of the absorbent is 0.25 g/L;
(3) and (3) adsorption of a third layer: and drying the second layer of adsorbent saturated with adsorbed methylene blue, adding the dried second layer of adsorbent into 800mg/L acid dye Congo red dye water with the initial concentration of 100-.
As a further improvement of the invention, the saturated adsorption capacity of the coal tar-based nitrogen-containing porous carbon adsorbent with the ultrahigh specific surface area to single-layer adsorption of Congo red and acid fuchsin reaches 3500mg/g and 2500mg/g respectively.
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in further detail below.
Example 1:
the embodiment provides coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area for dye adsorption, which is prepared by taking coal tar as a carbon source, calcium oxide as a template and potassium hydroxide as an activating agent and then carrying out ethylenediamine impregnation modification on the surface of the prepared porous carbon. The method comprises the following specific steps:
step 1: respectively weighing 5g of coal tar, 10g of calcium oxide and 20g of potassium hydroxide, and grinding in a grinder to fully mix the materials to obtain a reactant;
step 2: putting the obtained reactant into a crucible, putting the crucible into a tubular furnace, introducing nitrogen at the flow rate of 6mL/min, introducing the nitrogen for 30min to exhaust air in the device, heating to 900 ℃ at the heating rate of 5 ℃/min, keeping the temperature for 60min, cooling, turning off a power supply and the nitrogen when the tubular furnace is cooled to room temperature, taking out the crucible, taking out the obtained product, grinding, pickling with 2M hydrochloric acid, stirring on a magnetic stirrer for 24h, standing for 6h, washing to be neutral with distilled water, drying in a blast drying box at 110 ℃ for 24h, and sieving to obtain the coal tar-based porous carbon;
and step 3: and 2g of coal tar-based porous carbon is mixed with 100ml of solution containing 1g of ethylenediamine, and after the mixture is continuously stirred for 24 hours, the mixture is filtered, washed and dried to obtain the nitrogen-containing porous carbon.
The porous carbon prepared by the embodiment is of a porous structure, is rich in a large number of large micropores and small mesopores, has the morphological characteristics of a scanning graph and a transmission graph which are respectively shown as a graph 1 and a graph 2, and can be known from the graphs 1 and 2, the carbon coal tar based porous carbon is irregular bubble-shaped in morphology and has a rich pore channel structure under the synergistic action of the template and the potassium hydroxide, so that the adsorption of the dye is facilitated.
The porous carbon prepared in the embodiment has a porous structure and is rich in large micropores and small mesopores, the specific surface area and the pore size analyzer of the porous carbon material 3H-2000PM1 are used for measuring and analyzing the specific surface area, and the specific surface area of the porous carbon material obtained in the embodiment is 2310m through detection2/g。
The results of XPS analysis of the porous carbon prepared in this example are shown in FIG. 3, which shows that the adsorbent mainly contains two elements of carbon and oxygen, and in addition, contains a small amount of nitrogen.
The results of Nls orbital analysis of the porous carbon prepared in this example are shown in FIG. 4. As can be seen from FIG. 4, Nls is present mostly in the form of C-N-C (398.3eV), and C- (N)3(400.5eV), and a small amount in the form of C-N-H (401.8 eV).
As shown in FIG. 5, the results of the isothermal adsorption experiments on the nitrogen-containing porous carbon according to this example show that the saturated equilibrium adsorption amount of Congo red of the porous carbon is as high as 3500mg/g and the saturated equilibrium adsorption amount of acid fuchsin is as high as 2500 mg/g. The adsorption amount increases rapidly initially with increasing equilibrium concentration, and then changes slowly.
To verify the effect of activation temperature on the porous carbon structure, examples 2-4 were set.
Example 2:
the embodiment provides coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area for dye adsorption, which is prepared by taking coal tar as a carbon source, calcium oxide as a template and potassium hydroxide as an activating agent and then carrying out ethylenediamine impregnation modification on the surface of the prepared porous carbon. The method comprises the following specific steps:
step 1: respectively weighing 5g of coal tar, 10g of calcium oxide and 20g of potassium hydroxide, and grinding in a grinder to fully mix the materials to obtain a reactant;
step 2: putting the obtained reactant into a crucible, putting the crucible into a tubular furnace, introducing nitrogen at the flow rate of 6mL/min, introducing the nitrogen for 30min to exhaust air in the device, heating to 850 ℃ at the heating rate of 5 ℃/min, keeping the temperature for 60min, cooling, turning off a power supply and the nitrogen when the tubular furnace is cooled to room temperature, taking out the crucible, taking out the obtained product, grinding, pickling with 2M hydrochloric acid, stirring for 24h on a magnetic stirrer, standing for 6h, washing to be neutral with distilled water, drying for 24h in a blast drying box at 110 ℃, and sieving to obtain the coal tar-based porous carbon;
and step 3: and 2g of coal tar-based porous carbon is mixed with 100ml of solution containing 1g of ethylenediamine, and after the mixture is continuously stirred for 24 hours, the mixture is filtered, washed and dried to obtain the nitrogen-containing porous carbon.
Example 3
The embodiment provides coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area for dye adsorption, which is prepared by taking coal tar as a carbon source, calcium oxide as a template and potassium hydroxide as an activating agent and then carrying out ethylenediamine impregnation modification on the surface of the prepared porous carbon. The method comprises the following specific steps:
step 1: respectively weighing 5g of coal tar, 10g of calcium oxide and 20g of potassium hydroxide, and grinding in a grinder to fully mix the materials to obtain a reactant;
step 2: putting the obtained reactant into a crucible, putting the crucible into a tubular furnace, introducing nitrogen at the flow rate of 6mL/min, introducing the nitrogen for 30min to exhaust air in the device, heating to 870 ℃ at the heating rate of 5 ℃/min, keeping the temperature for 60min, cooling, turning off a power supply and the nitrogen when the tubular furnace is cooled to room temperature, taking out the crucible, taking out the obtained product, grinding, pickling with 2M hydrochloric acid, stirring on a magnetic stirrer for 24h, standing for 6h, washing to be neutral with distilled water, drying in a blast drying box at 110 ℃ for 24h, and sieving to obtain the coal tar-based porous carbon;
and step 3: and 2g of coal tar-based porous carbon is mixed with 100ml of solution containing 1g of ethylenediamine, and after the mixture is continuously stirred for 24 hours, the mixture is filtered, washed and dried to obtain the nitrogen-containing porous carbon.
The nitrogen-containing porous carbon materials prepared in examples 2 to 3 were analyzed respectively, the nitrogen-containing porous carbon materials prepared in examples 2 to 3 were rich in macro micropores and micro mesopores, the specific surface area of the porous carbon material in example 2 was 2180m, which was detected by measuring and analyzing the specific surface area and the pore size of the porous carbon material in example 3H-2000PM1 using a 3H-2000PM1 analyzer2(ii)/g; the specific surface area of the porous carbon material of example 3 was 2240m2/g。
Example 4
This example differs from example 1 only in that: the activation temperature is 950 ℃, the rest steps and parameters are the same as those of example 1, the nitrogen-containing porous carbon prepared in the example is analyzed, the nitrogen-containing porous carbon is found to be rich in large micropores and small mesopores, but the specific surface area of the porous carbon material of example 2 is detected to be 1790m by measuring and analyzing the specific surface area by using a 3H-2000PM1 porous carbon material specific surface area and pore size analyzer2The/g may be caused by collapse of part of the pore structure due to too high activation temperature.
To verify the effect of ethylenediamine dosage on the nitrogen-containing functional groups of the porous carbon material, examples 5-9 were set up.
Example 5
The embodiment provides coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area for dye adsorption, which is prepared by taking coal tar as a carbon source, calcium oxide as a template and potassium hydroxide as an activating agent and then carrying out ethylenediamine impregnation modification on the surface of the prepared porous carbon. The method comprises the following specific steps:
step 1: respectively weighing 5g of coal tar, 10g of calcium oxide and 20g of potassium hydroxide, and grinding in a grinder to fully mix the materials to obtain a reactant;
step 2: putting the obtained reactant into a crucible, putting the crucible into a tubular furnace, introducing nitrogen at the flow rate of 6mL/min, introducing the nitrogen for 30min to exhaust air in the device, heating to 900 ℃ at the heating rate of 5 ℃/min, keeping the temperature for 60min, cooling, turning off a power supply and the nitrogen when the tubular furnace is cooled to room temperature, taking out the crucible, taking out the obtained product, grinding, pickling with 2M hydrochloric acid, stirring on a magnetic stirrer for 24h, standing for 6h, washing to be neutral with distilled water, drying in a blast drying box at 110 ℃ for 24h, and sieving to obtain the coal tar-based porous carbon;
and step 3: 2g of coal tar-based porous carbon is mixed with 100ml of solution containing 0.5g of ethylenediamine, and after continuous stirring for 24 hours, the nitrogen-containing porous carbon is obtained by filtering, washing and drying.
Example 6
This example differs from example 5 only in step 3.
And step 3: 2g of coal tar-based porous carbon is mixed with 100ml of solution containing 0.7g of ethylenediamine, and after continuous stirring for 24 hours, the nitrogen-containing porous carbon is obtained by filtering, washing and drying.
Example 7
This example differs from example 5 only in step 3.
And step 3: and 2g of coal tar-based porous carbon is mixed with 100ml of solution containing 2g of ethylenediamine, and after the mixture is continuously stirred for 24 hours, the mixture is filtered, washed and dried to obtain the nitrogen-containing porous carbon.
Example 8
This example differs from example 5 only in step 3.
And step 3: and 2g of coal tar-based porous carbon is mixed with 150ml of solution containing 10g of ethylenediamine, and after the mixture is continuously stirred for 24 hours, the mixture is filtered, washed and dried to obtain the nitrogen-containing porous carbon.
Example 9
This example differs from example 5 only in step 3.
And step 3: and 2g of coal tar-based porous carbon is mixed with 200ml of solution containing 20g of ethylenediamine, and after the mixture is continuously stirred for 24 hours, the mixture is filtered, washed and dried to obtain the nitrogen-containing porous carbon.
XPS analysis of the porous carbons prepared in examples 5 to 9 revealed that the porous carbons prepared in examples 5 to 9 mainly contained two elements of carbon and oxygen, and contained a small amount of nitrogen in addition to the two elements.
Nls orbital analysis of the porous carbons prepared in examples 5-9 showed that Nls existed mostly as C-N-C (398.3eV) and C- (N)3(400.5eV), and slightly as C-N-H (401.8eV), but the kind and number of nitrogen-containing functional groups were substantially constant after increasing the amount of ethylenediamine, and the number of nitrogen-containing functional groups began to gradually decrease after the mass ratio of the porous carbon to ethylenediamine was between 1:5, wherein the porous carbon prepared in example 7 had the largest number of nitrogen-containing functional groups and the most abundant kinds.
Comparative example 1
This comparative example differs from example 1 only in that it has not been modified by ethylene diamine impregnation.
Comparative example 2
This comparative example modified ordinary activated carbon by the ethylene diamine impregnation of step (3) in example 1.
Comparative example 1
The blank control example is common active porous carbon.
Effect example 1:
the nitrogen-containing porous carbon prepared in examples 1 to 9, the porous carbon material prepared in comparative examples 1 to 2 and the activated carbon in the blank comparative example were subjected to adsorption treatment of the acid dye congo red as adsorbents by a multilayer adsorption method, comprising the following steps:
(1) adsorption of the first layer: adding the adsorbent into the Congo red dye water with the initial concentration of 700mg/L, and fully standing at room temperature, wherein the adding amount of the adsorbent is 0.125 g/L;
(2) and (3) adsorption of a second layer: drying the first layer of absorbent saturated with Congo red, continuously adding the first layer of absorbent into the dye wastewater treated in the step (1), standing for 36 hours at room temperature, wherein the adding amount of the absorbent is 0.25 g/L;
(3) and (3) adsorption of a third layer: and (3) drying the adsorbent adsorbed by the second layer, putting the dried adsorbent into the dye wastewater treated in the step (2), and standing the dried adsorbent for 36 hours at room temperature, wherein the putting amount of the adsorbent is 0.2 g/L.
The adsorption results are shown in Table 1.
TABLE 1
First layer adsorption capacity Second layer adsorption capacity Adsorption capacity of the third layer Total adsorption capacity
Example 1 3815 931 1001 5747
Example 2 3391 882 742 5015
Example 3 3443 901 858 5202
Example 4 2490 394 402 3286
Example 5 3520 839 895 5254
Example 6 3501 918 902 5321
Example 7 3899 935 1059 5893
Example 8 3845 923 989 5757
Example 9 3830 903 969 5702
Comparative example 1 2467 506 689 3662
Comparative example 2 2339 358 202 2899
Comparative example 1 1893 305 189 2387
Effect example 2:
the nitrogen-containing porous carbon prepared in examples 1 to 9, the porous carbon material prepared in comparative examples 1 to 2, and the activated carbon in the blank control example were subjected to adsorption treatment of acid dye magenta as an adsorbent by a multilayer adsorption method, and the steps were as follows: (1) adsorption of the first layer: adding the adsorbent into the Congo red dye water with the initial concentration of 600mg/L, and fully standing at room temperature, wherein the adding amount of the adsorbent is 0.125 g/L;
(2) and (3) adsorption of a second layer: drying the first layer of absorbent saturated with Congo red, continuously adding the first layer of absorbent into the dye wastewater treated in the step (1), standing for 36 hours at room temperature, wherein the adding amount of the absorbent is 0.25 g/L;
(3) and (3) adsorption of a third layer: and (3) drying the adsorbent adsorbed by the second layer, putting the dried adsorbent into the dye wastewater treated in the step (2), and standing the dried adsorbent for 36 hours at room temperature, wherein the putting amount of the adsorbent is 0.2 g/L.
The adsorption results are shown in Table 2.
TABLE 2
First layer adsorption capacity Second layer adsorption capacity Adsorption capacity of the third layer Total adsorption capacity
Example 1 2530 635 426 3591
Example 2 2469 623 408 3500
Example 3 2498 626 398 3522
Example 4 1563 206 132 1901
Example 5 2432 602 401 3435
Example 6 2451 623 431 3505
Example 7 2559 634 451 3644
Example 8 2542 626 442 3610
Example 9 2501 603 423 3527
Comparative example 1 1653 295 167 2115
Comparative example 2 1569 263 124 1956
Comparative example 1 1035 186 95 1316
As can be seen from tables 1-2, the nitrogen-containing porous carbon material prepared by the invention has good effect on adsorption of dye, and is obviously superior to common activated carbon; in addition, the nitrogen-containing porous carbon material prepared by the invention can be utilized for multiple times, so that the utilization rate of the adsorbent is greatly improved.
The above-described embodiments are merely illustrative of the preferred embodiments of the present invention, and do not limit the scope of the present invention, and various modifications and improvements of the technical solutions of the present invention can be made by those skilled in the art without departing from the spirit of the present invention, and the technical solutions of the present invention are within the scope of the present invention defined by the claims.

Claims (8)

1. The coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area is characterized in thatContains abundant micropores, small holes and mesopores; the surface of the material contains nitrogen-containing functional groups; the specific surface area exceeds 2000m2/g；
The preparation method of the coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area comprises the following steps: coal tar is used as a carbon source, calcium oxide is used as a template, potassium hydroxide is used as an activating agent to prepare coal tar base porous carbon, and then ethylenediamine is used for dipping modification to obtain the coal tar base porous carbon; the activation temperature was 900 ℃.
2. The coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area as claimed in claim 1, wherein the nitrogen-containing functional group is C-N-C, N- (C)3And C-N-H.
3. The coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area according to claim 1, wherein the mass ratio of the coal tar to the calcium oxide is 1: 1-1: 3, and the mass ratio of the coal tar to the potassium hydroxide is 1: 1-1: 5.
4. The coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area according to claim 1, wherein the mass ratio of the porous carbon to the ethylenediamine is 1: 10-4: 1.
5. The coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area according to claim 1, characterized by comprising the following steps:
(1) respectively weighing coal tar, calcium oxide and potassium hydroxide, and grinding in a grinder to fully mix the materials to obtain reactants;
(2) placing the obtained reactant into a crucible, then placing the crucible into a tubular furnace, slowly and uniformly introducing nitrogen to exhaust air in the crucible, slowly and uniformly heating to 900 ℃, keeping the constant temperature for 55-65min, then cooling, cooling to room temperature, turning off a power supply and the nitrogen, taking out the crucible, taking out a product, grinding, pickling, placing on a magnetic stirrer for uniformly stirring, standing, washing to neutrality, drying and sieving to obtain the coal tar-based porous carbon;
(3) and mixing the coal tar-based porous carbon with an ethylenediamine solution, uniformly stirring, filtering, washing with water, and drying to obtain the coal tar-based nitrogen-containing porous carbon with ultrahigh specific surface area.
6. The use of the coal tar-based ultra-high specific surface area nitrogen-containing porous carbon according to any one of claims 1 to 5 for adsorbing a dye, wherein the coal tar-based ultra-high specific surface area nitrogen-containing porous carbon is used as an adsorbent.
7. The use of claim 6, wherein the dyes are the acid dyes Congo Red and acid dye magenta.
8. The use of claim 6 or 7, wherein the saturated adsorption capacity of the coal tar-based nitrogen-containing porous carbon adsorbent with the ultrahigh specific surface area on single-layer adsorption of Congo red and acid fuchsin is 3500mg/g and 2500mg/g respectively.
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