A special-shaped porous biomass-based nano-activated carbon-graphene composite adsorption material

Abstract

The present invention discloses a special-shaped porous biomass-based nano-activated carbon-graphene composite adsorption material. A carbonized and activated biomass carbon source and graphene oxide are dispersed in a solvent to obtain a mixed solution, and a binder is added thereto. The mixed solution is used as a liquid target and subjected to pulsed laser irradiation under continuous stirring to ablate the liquid target. After the ablation, the material is centrifuged and washed to obtain a special-shaped porous biomass-based nano-activated carbon-graphene composite adsorption material. The preparation process of the present invention is simple, and only laser irradiation / ablation technology is required to obtain a graphene and activated carbon composite adsorption material with good performance; and in the prepared special-shaped porous biomass-based nano-activated carbon-graphene composite adsorption material, the activated carbon and graphene are tightly combined and uniformly dispersed on the graphene, and the morphology and size of the activated carbon can be controlled.

Description

Technical Field

[0001] The present invention relates to the technical field of carbon dioxide adsorption, and in particular to a special-shaped porous biomass-based nano-activated carbon-graphene composite adsorption material. Background Art

[0002] As a typical adsorption material, activated carbon has the characteristics of high specific surface area, stable physical and chemical stability, good environmental compatibility and abundant raw material sources. At the same time, compared with MOF materials, activated carbon has a good pore size distribution. Therefore, it is considered to be one of the most promising gas adsorption materials.

[0003] Application of activated carbon as an adsorbent in the field of gas adsorption. Activated carbon was first discovered to be used to adsorb CO2 gas. Since the CO2 gas molecule has a small diameter and is within the micropore size range (<2nm), studies have found that most activated carbon used for CO2 gas adsorption has a micro-mesoporous structure. Li et al. (2019) used pitted jujube slices as raw materials, first carbonized them and then activated them with KOH, and obtained a specific surface area of 3337m 2 / g of activated carbon with a hierarchical pore structure, the adsorption capacity of CO2 was 4.36mmol / g and 6.4mmol / g at 25°C, 1 atm, and 0°C, 1 bar, respectively. Heteroatom doping of porous carbon materials can increase the adsorption capacity of CO2. Studies have shown (Sevilla et al., 2012) that the presence of nitrogen-containing functional groups can provide alkaline sites, which are beneficial for the adsorption of acidic gases such as CO2. In summary, the unique structure of activated carbon can not only be used to capture the greenhouse gas CO2, but also adsorb CH4, H2, and other gases.

[0004] Graphene is a two-dimensional material formed by sp2 hybridization of carbon. It possesses enormous specific surface area and adsorption properties. However, due to strong π-π bonds and van der Waals forces between graphene sheets, irreversible aggregation occurs, significantly reducing the specific surface area and, consequently, the active surface area. In recent years, graphene has been loaded onto biochar or activated carbon to enhance conductivity and specific surface area, significantly improving the performance of these materials. For example, patent application number 202111223120.4 discloses an activated carbon / graphene composite material, its preparation method, and its application, and patent application number 201811337744.7 discloses a graphene / activated carbon composite material and its preparation method. These patents all prepare activated carbon-graphene composite materials to enhance adsorption properties. However, their preparation methods are complex, and the resulting graphene is of low purity. The resulting graphene sheets exhibit numerous structural defects, are prone to wrinkling and folding, and contain numerous oxygen-containing groups, which compromise the excellent properties of graphene. Summary of the Invention

[0005] In response to the above-mentioned existing technologies, the present invention aims to provide a shaped porous biomass-based nano-activated carbon-graphene composite adsorption material. The present invention has a simple preparation process, requiring only laser irradiation / ablation techniques to produce a graphene and activated carbon composite adsorption material with excellent performance. Furthermore, the activated carbon and graphene in the prepared shaped porous biomass-based nano-activated carbon-graphene composite adsorption material are tightly bonded and evenly dispersed on the graphene. Furthermore, the morphology and size of the activated carbon can be controlled.

[0006] To achieve the above object, the present invention adopts the following technical solutions:

[0007] The first aspect of the present invention provides a method for preparing a heterogeneous porous biomass-based nano-activated carbon-graphene composite adsorption material, the preparation method comprising:

[0008] The carbonized and activated biomass carbon source and graphene oxide are dispersed in a solvent to obtain a mixed solution, and a binder is added thereto. The mixed solution is used as a liquid target and subjected to pulsed laser irradiation under continuous stirring to ablate the liquid target. After the ablation, the target is centrifuged and washed to obtain a special-shaped porous biomass-based nano-activated carbon-graphene composite adsorption material.

[0009] Preferably, the carbonized activated biomass carbon source is prepared by the following method:

[0010] (1) mixing a biomass-based carbon source with a concentrated sulfuric acid solution and performing a hydrothermal reaction;

[0011] (2) The product after the hydrothermal reaction is washed and dried, and then mixed with an activator and subjected to high-temperature carbonization treatment to obtain a carbonized and activated biomass carbon source.

[0012] Preferably, in step (1), the material-liquid ratio of the biomass-based carbon source to the concentrated sulfuric acid solution is 1:0.2-2; and the biomass carbon source is straw, corn cobs, fallen leaves or coconut shells.

[0013] Preferably, in step (1), the temperature of the hydrothermal reaction is 100° C. to 200° C., and the time of the hydrothermal reaction is 3 h to 8 h.

[0014] Preferably, in step (2), the activator is KOH, NaOH, NaHCO3 or ZnO; and the mass ratio of the product after the hydrothermal reaction to the activator is 1:1 to 4.

[0015] Preferably, in step (2), the high-temperature carbonization is carried out in a protective atmosphere, the temperature of the high-temperature carbonization is 600°C to 900°C, the heating rate is 1-15°C / min, and the holding time is 1h to 4h.

[0016] Preferably, the mass ratio of the biomass carbon source after carbonization and activation to graphene oxide is 0.5-20%:80-100%; the solvent is deionized water, anhydrous ethanol or DMF; the concentration of graphene oxide in the solvent is 0.5-1 mg / mL; the binder is CuSO4, Na2HAsO4 or NaOCl, and the mass ratio of the biomass carbon source after carbonization and activation to the binder is: 5-1:1.

[0017] Preferably, the conditions of the pulsed laser irradiation are: laser wavelength of 248nm to 1064nm, frequency of 1 to 30Hz, energy density of 0.1 to 10J pulse -1 cm -2 , irradiation time is 10 to 200 minutes.

[0018] The second aspect of the present invention provides a heterogeneous porous biomass-based nano-activated carbon-graphene composite adsorption material prepared by the above preparation method.

[0019] The third aspect of the present invention provides the use of a special-shaped porous biomass-based nano-activated carbon-graphene composite adsorption material in the adsorption of carbon dioxide, volatile organic compounds, and water vapor.

[0020] Beneficial effects of the present invention:

[0021] (1) The preparation process of the present invention only requires laser irradiation / ablation technology to obtain a graphene and activated carbon composite adsorption material with good performance, which solves the shortcomings of traditional methods for preparing composite materials, such as high instrument requirements, low yield and complex operation; the activated carbon is tightly combined with the graphene and evenly dispersed on the graphene, and the morphology and size of the activated carbon can be controlled.

[0022] (2) The nano-activated carbon material prepared by the method of the present invention uses a biomass-based carbon source, which not only increases the added value of the carbon source but is also very environmentally friendly. The prepared activated carbon has a shaped porous structure and can effectively adsorb specific gas components based on its molecular structure. It has good thermal stability and excellent hydrophilicity.

[0023] (3) The nano-activated carbon adsorption material prepared by the present invention has a high specific surface area, a controllable pore size distribution structure, and stable physical and chemical properties, and can effectively solve the interference of gases with complex components. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 : Scanning electron microscopy image of the product after carbonization and activation;

[0025] Figure 2 : Scanning electron microscope image of the product after composite with graphene. DETAILED DESCRIPTION

[0026] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of the present application. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those skilled in the art to which the present application belongs.

[0027] In order to enable those skilled in the art to more clearly understand the technical solution of the present application, the technical solution of the present application will be described in detail below with reference to specific embodiments.

[0028] The test materials used in the examples of the present invention are all conventional test materials in the art and can be purchased through commercial channels.

[0029] Example 1

[0030] (1) Straw was mixed with concentrated sulfuric acid solution at a material-liquid ratio of 1:1 and subjected to hydrothermal reaction at 150 °C for 5.5 h.

[0031] (2) The product after the hydrothermal reaction was washed with deionized water to a pH of 7.0, dried, and mixed with KOH at a mass ratio of 1:2.5. The temperature was raised to 750°C at a rate of 10°C / min in high-purity nitrogen and subjected to high-temperature carbonization activation treatment for 2.5 hours.

[0032] (3) The carbonized activated product and graphene oxide were ultrasonically dispersed in 100 mL of deionized water at a mass ratio of 10:90. After mixing evenly, 2 mg of CuSO₄ reagent was added and stirred to dissolve. The concentration of graphene oxide used was 0.5 mg / mL as determined by Fourier transform infrared spectroscopy.

[0033] The mixed solution was used as a liquid target. Under continuous stirring by a magnetic stirrer, the liquid target was irradiated / ablated by a pulsed laser. The working conditions of the laser were: a laser with a wavelength of 1064 nm, a frequency of 15 Hz, and an energy density of 5 J pulses. -1 cm -2 The irradiation time is 100 min. After the reaction is completed, centrifugal washing is performed to obtain the heteromorphic porous biomass-based nano-activated carbon / graphene composite adsorption material.

[0034] Example 2

[0035] (1) Corn cobs were mixed with concentrated sulfuric acid solution at a material-liquid ratio of 1:0.2 and subjected to hydrothermal reaction at 200 °C for 3 h.

[0036] (2) The product after the hydrothermal reaction was washed with deionized water to a pH of 7.0, dried, and mixed with NaOH at a mass ratio of 1:1. The temperature was raised to 900°C in high-purity argon at a rate of 15°C / min and subjected to high-temperature carbonization activation treatment for 1 hour.

[0037] (3) The carbonized activated product and graphene oxide were ultrasonically dispersed into 100 mL of DMF solution at a mass ratio of 0.5:99.5. After mixing evenly, 0.5 mg of NaOCl was added and stirred to dissolve. The concentration of graphene oxide used was 1.0 mg / mL as determined by Fourier transform infrared spectrometer. The mixed solution was used as a liquid target. Under continuous stirring by a magnetic stirrer, the liquid target was irradiated / ablated by pulsed laser. The working conditions of the laser were: a laser with a wavelength of 248 nm, a frequency of 30 Hz, and an energy density of 10 J pulse. -1 cm -2 The irradiation time is 10 min. After the reaction is completed, centrifugal washing can be performed to obtain the heteromorphic porous biomass-based nano-activated carbon / graphene composite adsorption material.

[0038] Example 3

[0039] (1) Coconut shell and concentrated sulfuric acid solution were mixed at a material-liquid ratio of 1:2 and subjected to hydrothermal reaction at 100 °C for 8 h.

[0040] (2) The product after the hydrothermal reaction was washed with deionized water to a pH of 7.0, dried, and mixed with ZnO at a mass ratio of 1:4. The temperature was raised to 600°C at a rate of 1°C / min in high-purity argon and subjected to high-temperature carbonization activation treatment for 4 hours.

[0041] (3) The carbonized activated product and graphene oxide were ultrasonically dispersed in 100 mL of anhydrous ethanol at a mass ratio of 20:80. After mixing evenly, 10 mg of Na2HAsO4 was added and stirred to dissolve. The concentration of graphene oxide used was detected by Fourier transform infrared spectrometer to be 0.8 mg / ml. The above mixed solution was used as a liquid target. Under continuous stirring of a magnetic stirrer, the liquid target was irradiated / ablated by pulsed laser. The working conditions of the laser were: a laser with a wavelength of 1064 nm, a frequency of 1 Hz, and an energy density of 10 J pulse. -1 cm -2 The irradiation time is 200 min. After the reaction is completed, centrifugal washing is performed to obtain the heteromorphic porous biomass-based nano-activated carbon / graphene composite adsorption material.

[0042] Comparative Example 1

[0043] (1) Straw was mixed with concentrated sulfuric acid solution at a material-liquid ratio of 1:1 and subjected to hydrothermal reaction at 150 °C for 5.5 h.

[0044] (2) The product after the hydrothermal reaction was washed with deionized water to a pH of 7.0, dried, and mixed with KOH at a mass ratio of 1:2.5. The temperature was raised to 750°C at a rate of 10°C / min in high-purity nitrogen and subjected to high-temperature carbonization activation treatment for 2.5 hours.

[0045] (3) 5.55 mg of the carbonized activated product was ultrasonically dispersed into 100 mL of deionized water. The mixed solution was used as a liquid target. Under continuous stirring by a magnetic stirrer, the liquid target was irradiated / ablated by a pulsed laser. The working conditions of the laser were: a laser with a wavelength of 1064 nm, a frequency of 15 Hz, and an energy density of 5 J pulses. -1 cm -2 The irradiation time is 100 min. After the reaction is completed, the porous biomass-based nano-activated carbon adsorption material can be obtained by centrifugal washing.

[0046] Comparative Example 2

[0047] 50 mg of graphene oxide was ultrasonically dispersed in 100 mL of deionized water. Fourier transform infrared spectroscopy was used to determine the graphene concentration to be 0.5 mg / mL. The mixed solution was used as a liquid target and, under continuous stirring with a magnetic stirrer, was irradiated / ablated by a pulsed laser. The laser operating conditions were: a 1064 nm wavelength laser, a 15 Hz frequency, and an energy density of 5 J pulses. -1 cm -2 The irradiation time is 100 min. After the reaction is completed, the graphene composite adsorption material can be obtained by centrifugal washing.

[0048] Comparative Example 3

[0049] (1) Straw was mixed with concentrated sulfuric acid solution at a material-liquid ratio of 1:1 and subjected to hydrothermal reaction at 150 °C for 5.5 h.

[0050] (2) The product after the hydrothermal reaction was washed with deionized water to a pH of 7.0, dried, and mixed with KOH at a mass ratio of 1:2.5. The temperature was raised to 750°C at a rate of 10°C / min in high-purity nitrogen and subjected to high-temperature carbonization activation treatment for 2.5 hours.

[0051] (3) Ultrasonic dispersion of 5.55 mg of the carbonized activated product into 100 mL of deionized water was performed, and after uniform mixing, 2 mg of CuSO4 reagent was added and stirred to dissolve. The mixed solution was used as a liquid target. Under continuous stirring by a magnetic stirrer, the liquid target was irradiated / ablated by pulsed laser. The working conditions of the laser were: a laser with a wavelength of 1064 nm, a frequency of 15 Hz, and an energy density of 5 J pulses. -1 cm -2 The irradiation time is 100 min. After the reaction is completed, the porous biomass-based nano-activated carbon adsorption material can be obtained by centrifugal washing.

[0052] Comparative Example 4

[0053] 50mg of graphene oxide was ultrasonically dispersed in 100mL of deionized water. After mixing thoroughly, 2mg of CuSO4 reagent was added and stirred to dissolve. The graphene concentration used was 0.5mg / ml as determined by Fourier transform infrared spectroscopy. The mixed solution was used as a liquid target and, under continuous stirring with a magnetic stirrer, was irradiated / ablated by pulsed laser. The laser operating conditions were: a 1064nm wavelength laser, a 15Hz frequency, and an energy density of 5J pulses. -1 cm -2 The irradiation time is 100 min. After the reaction is completed, the graphene composite adsorption material can be obtained by centrifugal washing.

[0054] Comparative Example 5

[0055] (1) Straw was mixed with concentrated sulfuric acid solution at a material-liquid ratio of 1:1 and subjected to hydrothermal reaction at 150 °C for 5.5 h.

[0056] (2) The product after the hydrothermal reaction was washed with deionized water to a pH of 7.0, dried, and mixed with KOH at a mass ratio of 1:2.5. The temperature was raised to 750°C at a rate of 10°C / min in high-purity nitrogen and subjected to high-temperature carbonization activation treatment for 2.5 hours.

[0057] (3) The carbonized activated product and graphene oxide were ultrasonically dispersed into 100 mL of deionized water at a mass ratio of 10:90. The concentration of graphene oxide used was 0.5 mg / mL as determined by Fourier transform infrared spectroscopy. The mixed solution was used as a liquid target and was continuously stirred by a magnetic stirrer. The liquid target was irradiated / ablated by a pulsed laser. The working conditions of the laser were: a laser with a wavelength of 1064 nm, a frequency of 15 Hz, and an energy density of 5 J pulses. -1 cm -2 The irradiation time is 100 min. After the reaction is completed, centrifugal washing is performed to obtain the heteromorphic porous biomass-based nano-activated carbon / graphene composite adsorption material.

[0058] Test Example 1

[0059] The adsorption performance of a material is generally quantitatively characterized by the water vapor adsorption isotherm at room temperature, using the static adsorption method of a saturated salt solution in a closed container. The static adsorption test for water vapor is performed under certain concentration (or pressure) and temperature conditions, measuring the adsorption capacity when equilibrium is reached between the adsorbent material and water vapor after prolonged, full contact.

[0060] The single component water vapor adsorption isotherm was tested using the 3Flex three-station full-function multi-purpose adsorption instrument produced by Micromeritics of the United States. The instrument is based on the "static capacity method" isothermal adsorption principle and uses a 29-bit A / D conversion sensor, which can measure relative pressures as low as 10 -9The adsorption isotherm of Pa was prepared using a high-precision vapor volatilization preparation device. The specific test steps are as follows: First, 0.1g of the adsorbent prepared in Examples 1 to 3 and Comparative Examples 1 to 5 was weighed and placed in a sample tube. The sample tube was pretreated by vacuum degassing at 473K for 7 hours to remove small impurity molecules on the solid surface and in the pores. The pretreated adsorbent was then moved to the analysis station. The pressure measurement range (0.1Pa to 500Pa), adsorption temperature (298K, 308K, and 318K), adsorbed gas (water vapor), and test point were set. The temperature was controlled using a circulating water bath. Finally, the absorption capacity of each adsorbent was measured. The results are shown in Table 1.

[0061] Table 1 Absorption

[0062]

[0063] It can be seen from Table 1 that the adsorption amounts of Examples 1 to 3 are much higher than those of Comparative Examples 1 to 5, indicating that the adsorption effect of the irregular porous biomass-based nano-activated carbon / graphene composite adsorption material obtained by the binder and laser ablation is significantly improved.

[0064] Test Example 2

[0065] Prepare cylindrical containers of the same volume (with openings at both ends of the container), fill each container with the adsorbent prepared in Examples 1 to 3 and Comparative Examples 1 to 5, so that the volume of the adsorbent in each container is the same, and introduce a 300 mg / m 3 The trichloroethane discharged from the other end was measured, and the results are shown in Table 2.

[0066] Table 2 Content of trichloroethane

[0067]

[0068] It can be seen from Table 2 that the adsorbents prepared in Examples 1 to 3 can effectively adsorb trichloroethane and achieve efficient adsorption of VOCs.

[0069] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A method for preparing a special-shaped porous biomass-based nano-activated carbon-graphene composite adsorption material, characterized in that: The preparation method is: The carbonized and activated biomass carbon source and graphene oxide are dispersed in a solvent to obtain a mixed solution, a binder is added, and the mixed solution is used as a liquid target. Under continuous stirring, pulsed laser irradiation is performed to ablate the liquid target. After the ablation, centrifugal washing is performed to obtain a special-shaped porous biomass-based nano-activated carbon-graphene composite adsorption material; The binder is CuSO4, Na2HAsO4 or NaOCl.

2. The preparation method according to claim 1, characterized in that The carbonized and activated biomass carbon source is prepared by the following method: (1) Mixing a biomass-based carbon source with a concentrated sulfuric acid solution and performing a hydrothermal reaction; (2) The product after the hydrothermal reaction is washed and dried, then mixed with an activator and subjected to high-temperature carbonization treatment to obtain a carbonized and activated biomass carbon source.

3. The preparation method according to claim 2, characterized in that In step (1), the material-liquid ratio of the biomass-based carbon source to the concentrated sulfuric acid solution is 1:0.2~2; the biomass-based carbon source is straw, corn cobs, fallen leaves or coconut shells.

4. The preparation method according to claim 2, characterized in that In step (1), the temperature of the hydrothermal reaction is 100° C. to 200° C., and the time of the hydrothermal reaction is 3 h to 8 h.

5. The preparation method according to claim 2, characterized in that In step (2), the activator is KOH, NaOH, NaHCO3 or ZnO; the mass ratio of the product after the hydrothermal reaction to the activator is 1:1~4.

6. The preparation method according to claim 2, characterized in that In step (2), the high-temperature carbonization is carried out in a protective atmosphere, the temperature of the high-temperature carbonization is 600°C to 900°C, the heating rate is 1-15°C / min, and the holding time is 1h to 4h.

7. The preparation method according to claim 1, characterized in that The mass ratio of the carbonized and activated biomass carbon source to the graphene oxide is 0.5-20%:80-100%; the solvent is deionized water, anhydrous ethanol or DMF; the concentration of the graphene oxide in the solvent is 0.5 mg / mL-1 mg / mL; and the mass ratio of the carbonized and activated biomass carbon source to the binder is 5-1:

1.

8. The preparation method according to claim 1, characterized in that The conditions of the pulsed laser irradiation are: laser wavelength of 248 nm to 1064 nm, frequency of 1 to 30 Hz, energy density of 0.1 to 10 J pulse -1 cm -2 , irradiation time is 10 to 200 min.

9. The irregular porous biomass-based nano-activated carbon-graphene composite adsorption material prepared by the preparation method according to any one of claims 1 to 8.

10. Use of the irregularly shaped porous biomass-based nano-activated carbon-graphene composite adsorption material according to claim 9 in the adsorption of carbon dioxide, volatile organic compounds, and water vapor.

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