Bimetallic MOFs impregnated activated carbon adsorbent and its preparation method and application

Abstract

The present invention relates to the technical field of adsorption composite materials, and in particular to a bimetallic MOFs impregnated activated carbon adsorbent and a preparation method and application thereof. A Co and Zn bimetallic MOFs impregnated activated carbon adsorbent is synthesized by a one-pot method. A Co salt solution and a Zn salt solution are sequentially added to a 2-methylimidazole solution, wherein the molar ratio of the Co salt to the Zn salt is 1:0.5-2. After stirring and reacting for 20-40 minutes at room temperature, activated carbon is added to the obtained reaction solution, and after stirring for 1.5-2.5 hours, the mixture is centrifuged, washed, and dried to obtain a bimetallic MOFs impregnated activated carbon adsorbent. The bimetallic MOFs impregnated activated carbon adsorbent of the present invention has the characteristics of adjustable micropore size and structure, which ensures the uniform dispersion of metal ions, and thanks to the dual adsorption of Co, Zn bimetallic MOF and activated carbon, the Co-Zn-MOFs@AC adsorbent has excellent adsorption performance.

Description

Technical Field

[0001] The present invention relates to the technical field of adsorption composite materials, and in particular to a bimetallic MOFs impregnated activated carbon adsorbent and a preparation method and application thereof. Background Art

[0002] Most volatile organic compounds (VOCs) are highly toxic, carcinogenic and dangerous, which not only seriously harms human health, but also poses a serious threat to the ecological environment. Therefore, the development of a method and material for treating VOCs is of great significance to humans and the natural environment. Activated carbon is one of the most widely used adsorption materials because it has advantages such as rich pore structure, large specific surface area, and high porosity. Activated carbon materials are mainly based on microporous structures, and have shown good adsorption performance in the study of VOCs adsorption. However, due to the rich irregular microporous structure, it is easy to cause pore blockage during the adsorption process, which increases the mass transfer resistance and is not conducive to the desorption process.

[0003] In order to solve the above problems, impregnated activated carbon has been widely studied in VOCs adsorption materials. Impregnated activated carbon is a high-quality activated carbon carrier impregnated with different chemical agents to make it have the characteristics of chemical adsorption or catalytic absorption. After the addition of impregnating agent, activated carbon can undergo chemical adsorption or catalytic absorption with the adsorbate on the basis of the single physical adsorption of activated carbon, thereby greatly improving the adsorption efficiency. It is the main filling material for military protective equipment and is also used to remove a variety of industrial harmful and toxic gases. The choice of conventional impregnating agents is limited, and the chemical adsorption sites produced on the activated carbon are few, and the improvement of the adsorption efficiency of activated carbon is limited. Summary of the invention

[0004] In view of this, the purpose of the present invention is to provide a bimetallic MOFs impregnated activated carbon adsorbent and a preparation method and application thereof, which solves the problems of limited selection of conventional impregnating agents for existing impregnated activated carbon, few chemical adsorption sites generated on the activated carbon, and limited improvement in the adsorption efficiency of the activated carbon.

[0005] The present invention solves the above technical problems by the following technical means:

[0006] The first aspect of the present invention is to provide a bimetallic MOFs impregnated activated carbon adsorbent, wherein the impregnated activated carbon adsorbent is a Co, Zn bimetallic MOFs impregnated activated carbon adsorbent, and the molar ratio of Co to Zn is 1:0.5-2.

[0007] In combination with the first aspect, in some embodiments, the activated carbon is any one of wood activated carbon, coal activated carbon, coconut shell activated carbon and biomass activated carbon.

[0008] The second aspect of the present invention is to provide a method for preparing a bimetallic MOFs-impregnated activated carbon adsorbent, comprising the following steps:

[0009] A Co salt solution and a Zn salt solution are sequentially added to a 2-methylimidazole solution, wherein the molar ratio of the Co salt to the Zn salt is 1:0.5-2. After stirring and reacting for 20-40 minutes at room temperature, activated carbon is added to the obtained reaction solution, and after stirring for 1.5-2.5 hours, the solution is centrifuged, washed, and dried to obtain a bimetallic MOFs-impregnated activated carbon adsorbent.

[0010] In combination with the second aspect, in some embodiments, the mass ratio of the total mass of the Co salt and the Zn salt to the activated carbon is 3.9-4.7:0.01-0.06.

[0011] In combination with the second aspect, in some embodiments, the molar ratio of the Co salt to the Zn salt is 1:0.5-2.

[0012] In combination with the second aspect, in some embodiments, the Co salt is any one of cobalt nitrate, cobalt acetate, cobalt carbonate, cobalt sulfate and cobalt borate, and the Zn salt is any one of zinc nitrate, zinc acetate, zinc carbonate, zinc sulfate and zinc borate.

[0013] In combination with the second aspect, in some embodiments, the molar ratio of the total mole of the Co salt and the Zn salt to 2-methylimidazole is 1 to 1.5:1.

[0014] In combination with the second aspect, in some embodiments, the centrifugal rotation speed is set to 9000-11000 rpm.

[0015] The third aspect of the present invention is to provide the use of the above-mentioned bimetallic MOFs impregnated activated carbon adsorbent in gas adsorption.

[0016] In combination with the third aspect, in some embodiments, the gas is at least one of CO2, benzene, and toluene.

[0017] The present invention adopts a one-pot method to synthesize Co, Zn bimetallic MOFs impregnated activated carbon adsorbent (Co-Zn-MOFs@AC), which has the advantages of simple preparation process, low cost and suitability for mass production. The Co-Zn-MOFs@AC adsorbent has the characteristics of adjustable micropore size and structure, which ensures the uniform dispersion of metal ions. Thanks to the dual adsorption effect of Co, Zn bimetallic MOF and activated carbon, the Co-Zn-MOFs@AC adsorbent has excellent adsorption performance. Under the conditions of 298.2K and 5000kPa, the adsorption amount of AC for CO2 is about 139.0mg·g -1 The adsorption capacity of Co-Zn-MOFs@AC adsorbent for CO2 is as high as 509.6 mg·g-1 , and its specific surface area is as high as 1105.1m 2 ·g -1 ; Under 298.2K, the adsorption capacity of AC for benzene and toluene is about 322.53 mg / g and 335.58 mg / g, respectively, while the adsorption capacity of Co-Zn-MOFs@AC adsorbent for benzene and toluene is 518.10 mg / g and 521.38 mg / g, respectively. It can be seen that the bimetallic MOFs impregnated activated carbon adsorbent of the present invention has more chemical adsorption sites and better adsorption performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 It is the N2 adsorption-desorption isotherm of activated carbon powder and Co-Zn-MOFs@AC in Example 1 at 77K. DETAILED DESCRIPTION

[0019] The technical solutions in the embodiments of the present invention will be described clearly and completely below in combination with the implementation of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0020] In the following examples, if no specific conditions are specified, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. The raw materials, equipment or instruments used, if no manufacturer is specified, are all conventional products that can be obtained commercially.

[0021] The purpose of this application is to overcome the shortcomings of the prior art and provide a Co, Zn bimetallic MOFs impregnated activated carbon adsorbent and its preparation method and application, which can greatly improve the adsorption capacity of the adsorbent under the dual effects of physical adsorption of activated carbon and chemical adsorption of Co, Zn bimetallic MOFs.

[0022] This application adopts a one-pot method to synthesize Co and Zn bimetallic MOFs impregnated activated carbon adsorbent (Co-Zn-MOFs@AC), and the specific preparation method is as follows:

[0023] Co salt and Zn salt solution are sequentially added to 2-methylimidazole solution, wherein the molar ratio of Co salt to Zn salt is 1:0.5-2:1, and the molar ratio of the total mole of Co salt and Zn salt to 2-methylimidazole is 1-1.5:1. After stirring and reacting for 20-40 minutes at room temperature, a certain amount of activated carbon is added to the reaction solution, and after stirring for 1.5-2.5 hours, centrifugation, washing and drying are performed. The Co salt is any one of cobalt nitrate, cobalt acetate, cobalt carbonate, cobalt sulfate and cobalt borate, the Zn salt is any one of zinc nitrate, zinc acetate, zinc carbonate, zinc sulfate and zinc borate; and the activated carbon (AC) is any one of wood activated carbon, coal activated carbon, coconut shell activated carbon and biomass activated carbon.

[0024] The bimetallic MOFs impregnated activated carbon adsorbent and its preparation method of the present application are described in detail below through Examples 1-7:

[0025] Example 1

[0026] The preparation method of the bimetallic MOFs impregnated activated carbon adsorbent of this embodiment is as follows:

[0027] When the molar ratio of Co salt to Zn salt is 1:1, 2.184g Co(NO3)2·6H2O is dissolved in 30mL methanol and marked as solution A, 2.232g Zn(NO3)2·6H2O is dissolved in 30mL methanol and marked as solution B, and 2.464g 2-methylimidazole is dissolved in 60mL methanol and marked as solution C. Then, under ultrasonic conditions, solution A is slowly dripped into solution B, stirred for 5min until the solution is mixed evenly, and marked as solution D; then solution C is added to solution D at the same speed, stirred for 30min, and marked as solution E; then 10mg activated carbon is added to solution E and stirred for 2 hours. Finally, the product is centrifuged and washed with methanol solution, and washed several times at a speed of 10000 rpm to finally obtain Co-Zn-MOFs@AC. The activated carbon (AC) is any one of wood activated carbon, coal activated carbon, coconut shell activated carbon and biomass activated carbon. In this embodiment, coconut shell activated carbon is selected.

[0028] Example 2

[0029] The preparation method of the bimetallic MOFs impregnated activated carbon adsorbent of this embodiment is as follows:

[0030] When the molar ratio of Co salt to Zn salt is 1:2, 1.455g Co(NO3)2·6H2O is dissolved in 30mL methanol and marked as solution A, 2.975g Zn(NO3)2·6H2O is dissolved in 30mL methanol and marked as solution B, and 2.464g 2-methylimidazole is dissolved in 60mL methanol and marked as solution C. Then, under ultrasonic conditions, solution A is slowly dripped into solution B, stirred for 5min until the solution is mixed evenly, and marked as solution D; then solution C is added to solution D at the same speed, stirred for 30min, and marked as solution E; then 10mg activated carbon is added to solution E and stirred for 2 hours. Finally, the product is centrifuged and washed with methanol solution, and washed several times at a speed of 10000 rpm to finally obtain Co-Zn-MOFs@AC. The activated carbon (AC) is any one of wood activated carbon, coal activated carbon, coconut shell activated carbon and biomass activated carbon. In this embodiment, coconut shell activated carbon is selected.

[0031] Example 3

[0032] The preparation method of the bimetallic MOFs impregnated activated carbon adsorbent of this embodiment is as follows:

[0033] When the molar ratio of Co salt to Zn salt is 2:1, 2.911g Co(NO3)2·6H2O is dissolved in 30mL methanol and marked as solution A, 1.488g Zn(NO3)2·6H2O is dissolved in 30mL methanol and marked as solution B, and 2.464g 2-methylimidazole is dissolved in 60mL methanol and marked as solution C. Then, under ultrasonic conditions, solution A is slowly dripped into solution B, stirred for 5min until the solution is mixed evenly, and marked as solution D; then solution C is added to solution D at the same speed, stirred for 30min, and marked as solution E; activated carbon (10mg) is added to solution E and stirred for 2 hours. Finally, the product is centrifuged and washed with methanol solution, and washed several times at a speed of 10000 rpm to finally obtain Co-Zn-MOFs@AC. The activated carbon (AC) is any one of wood activated carbon, coal activated carbon, coconut shell activated carbon and biomass activated carbon. In this embodiment, coconut shell activated carbon is selected.

[0034] Example 4

[0035] The preparation method of the bimetallic MOFs impregnated activated carbon adsorbent of this embodiment is as follows:

[0036] When the molar ratio of Co salt to Zn salt is 1:1, 2.184g Co(NO3)2·6H2O is dissolved in 30mL methanol and marked as solution A, 2.232g Zn(NO3)2·6H2O is dissolved in 30mL methanol and marked as solution B, and 2.464g 2-methylimidazole is dissolved in 60mL methanol and marked as solution C. Then, under ultrasonic conditions, solution A is slowly dripped into solution B, stirred for 5min until the solution is mixed evenly, and marked as solution D; then solution C is added to solution D at the same speed, stirred for 20min, and marked as solution E; then 20mg activated carbon is added to solution E and stirred for 1.5 hours. Finally, the product is centrifuged and washed with methanol solution, and washed several times at a speed of 9000 rpm to finally obtain Co-Zn-MOFs@AC. The activated carbon (AC) is any one of wood activated carbon, coal activated carbon, coconut shell activated carbon and biomass activated carbon. In this embodiment, wood activated carbon is selected.

[0037] Example 5

[0038] The preparation method of the bimetallic MOFs impregnated activated carbon adsorbent of this embodiment is as follows:

[0039] When the molar ratio of Co salt to Zn salt is 1:1, 2.184g Co(NO3)2·6H2O is dissolved in 30mL methanol and marked as solution A, 2.232g Zn(NO3)2·6H2O is dissolved in 30mL methanol and marked as solution B, and 2.464g 2-methylimidazole is dissolved in 60mL methanol and marked as solution C. Then, under ultrasonic conditions, solution A is slowly dripped into solution B, stirred for 5min until the solution is mixed evenly, and marked as solution D; then solution C is added to solution D at the same speed, stirred for 40min, and marked as solution E; then 30mg activated carbon is added to solution E and stirred for 1.5 hours. Finally, the product is centrifuged and washed with methanol solution, and washed several times at a speed of 11000 rpm to finally obtain Co-Zn-MOFs@AC. The activated carbon (AC) is any one of wood activated carbon, coal activated carbon, coconut shell activated carbon and biomass activated carbon. In this embodiment, wood activated carbon is selected.

[0040] Example 6

[0041] The preparation method of the bimetallic MOFs impregnated activated carbon adsorbent of this embodiment is as follows:

[0042] When the molar ratio of Co salt to Zn salt is 1:1, 2.184g Co(NO3)2·6H2O is dissolved in 30mL methanol and marked as solution A, 2.232g Zn(NO3)2·6H2O is dissolved in 30mL methanol and marked as solution B, and 2.464g 2-methylimidazole is dissolved in 60mL methanol and marked as solution C. Then, under ultrasonic conditions, solution A is slowly dripped into solution B, stirred for 5min until the solution is mixed evenly, and marked as solution D; then solution C is added to solution D at the same speed, stirred for 30min, and marked as solution E; then 50mg activated carbon is added to solution E and stirred for 2 hours. Finally, the product is centrifuged and washed with methanol solution, and washed several times at a speed of 10,000 rpm to finally obtain Co-Zn-MOFs@AC. The activated carbon (AC) is any one of wood activated carbon, coal activated carbon, coconut shell activated carbon and biomass activated carbon. In this embodiment, coconut shell activated carbon is selected.

[0043] Example 7

[0044] The preparation method of the bimetallic MOFs impregnated activated carbon adsorbent of this embodiment is as follows:

[0045] When the molar ratio of Co salt to Zn salt is 1:1, 2.184g Co(NO3)2·6H2O is dissolved in 30mL methanol and marked as solution A, 2.232g Zn(NO3)2·6H2O is dissolved in 30mL methanol and marked as solution B, and 2.464g 2-methylimidazole is dissolved in 60mL methanol and marked as solution C. Then, under ultrasonic conditions, solution A is slowly dripped into solution B, stirred for 5min until the solution is mixed evenly, and marked as solution D; then solution C is added to solution D at the same speed, stirred for 30min, and marked as solution E; then 60mg activated carbon is added to solution E and stirred for 2 hours. Finally, the product is centrifuged and washed with methanol solution, and washed several times at a speed of 10,000 rpm to finally obtain Co-Zn-MOFs@AC. The activated carbon (AC) is any one of wood activated carbon, coal activated carbon, coconut shell activated carbon and biomass activated carbon. In this embodiment, coconut shell activated carbon is selected.

[0046] The bimetallic MOFs impregnated activated carbon adsorbent prepared in Examples 1-3 was subjected to specific surface area test and gas adsorption test:

[0047] (1) Specific surface area test: At 77K, a physical adsorption instrument was used to conduct N2 adsorption-desorption experiments to determine the BET specific surface area. Before the adsorption experiment, the sample was heated at 80°C for 8h. During the test, the desorption-adsorption of the material to low-temperature N2 was measured, and the isotherm curve of the adsorption amount at different partial pressures was obtained. The slope of the adsorption amount increase was calculated to obtain the BET specific surface area of ​​the material.

[0048] Figure 1 is the N2 adsorption-desorption isotherm of activated carbon powder and Co-Zn-MOFs@AC in Example 1 at 77K, Figure 1 The data show that the Co-Zn-MOFs@AC of Example 1 has a larger specific surface area, and the specific surface area is significantly better than that of activated carbon powder.

[0049] (2) Gas adsorption test: The adsorption equilibrium isotherms of powdered activated carbon and Co-Zn-MOFs@AC adsorbents for toxic gases such as CO2, benzene, and toluene were measured using a static adsorption device at 298.2 K, 323.2 K, and 348.2 K. Before the adsorption measurement, the adsorbent must be evacuated at 423.2 K until no mass loss is observed, and then a certain amount of adsorbent (about 10 g) is carefully loaded into the adsorption cell to reduce the wear of the adhesive and ensure accurate determination of the free volume.

[0050] The test results are shown in Table 1:

[0051] Table 1

[0052]

[0053] The data in Table 1 show that the Co-Zn-MOFs@AC adsorbent of the present invention has excellent adsorption performance. Under the conditions of 298.2K and 5000kPa, the adsorption capacity of AC for CO2 is about 139.0mg·g -1 The adsorption capacity of Co-Zn-MOFs@AC adsorbent for CO2 is as high as 509.6 mg·g -1 , and its specific surface area is as high as 1105.1m 2 ·g -1 ; Under 298.2K conditions, the adsorption capacity of AC for benzene and toluene is approximately 322.53 mg / g and 335.58 mg / g, respectively, while the adsorption capacity of Co-Zn-MOFs@AC adsorbent for benzene and toluene is 518.10 mg / g and 521.38 mg / g, respectively. Therefore, the bimetallic MOFs impregnated activated carbon adsorbent of the present invention can be used in gas adsorption, especially in the adsorption of CO2, benzene and toluene gases. In addition, the Co-Zn-MOFs@AC of the present invention also has the advantages of simple preparation process, low cost and suitability for mass production.

[0054] The above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit the present invention. Although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the purpose and scope of the technical solutions of the present invention, which should be included in the scope of the claims of the present invention. The techniques, shapes, and structural parts not described in detail in the present invention are all known technologies.

Claims

1. Application of bimetallic MOFs impregnated activated carbon adsorbent in gas adsorption, characterized in that: The gas is at least one of CO2, benzene and toluene; The impregnated activated carbon adsorbent is a Co and Zn bimetallic MOFs impregnated activated carbon adsorbent, and the molar ratio of Co and Zn is 1:1; The preparation method of bimetallic MOFs impregnated activated carbon adsorbent comprises the following steps: Adding Co salt solution and Zn salt solution to 2-methylimidazole solution in sequence, stirring and reacting for 20 to 40 minutes at room temperature, adding activated carbon to the obtained reaction solution, stirring for 1.5 to 2.5 hours, centrifuging, washing and drying to obtain a bimetallic MOFs-impregnated activated carbon adsorbent; The mass ratio of the total mass of the Co salt and the Zn salt to the activated carbon is 3.9-4.7:0.01-0.06; The molar ratio of the total mole of the Co salt and the Zn salt to the 2-methylimidazole is 1 to 1.5:1; The centrifugal speed is set to 9000-11000 rpm.

2. The use according to claim 1, characterized in that: The activated carbon is any one of wood activated carbon, coal activated carbon, coconut shell activated carbon and biomass activated carbon.

3. The use according to claim 2, characterized in that: The Co salt is any one of cobalt nitrate, cobalt acetate, cobalt carbonate, cobalt sulfate and cobalt borate, and the Zn salt is any one of zinc nitrate, zinc acetate, zinc carbonate, zinc sulfate and zinc borate.

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