CN110697697A - Preparation method of nitrated graphene - Google Patents
Preparation method of nitrated graphene Download PDFInfo
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- CN110697697A CN110697697A CN201910942911.9A CN201910942911A CN110697697A CN 110697697 A CN110697697 A CN 110697697A CN 201910942911 A CN201910942911 A CN 201910942911A CN 110697697 A CN110697697 A CN 110697697A
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Abstract
The invention relates to a preparation method of nitrated graphene, and belongs to the technical field of graphene functionalization. Graphite powder is used as a raw material, and KMnO is adopted4And H2O2The combination is used for pretreating graphite powder, then the complete expansion of the micro-expanded graphite powder is ensured through a microwave excitation mode, high-activity graphene with high activity, low oxygen content, good stability and good compatibility is obtained, and when the high-activity graphene is subsequently reacted with mixed acid, the mixed acid is used for carrying out nitration treatment on the high-activity graphene, so that the nitration rate of the nitrated graphene is ensured to be adjustable, and the nitrated graphene with higher nitration rate (up to 50%) is obtained.
Description
Technical Field
The invention discloses a nitrated graphene and a preparation method and application thereof, and belongs to the technical field of graphene functionalization.
Background
Graphene was first discovered in 2004 by Hahm and NovoShowcov, Manchester university, England. The carbon material is a novel carbon material with a single-layer two-dimensional honeycomb lattice structure formed by tightly stacking carbon atoms, and is a basic unit for forming other dimensionality carbon materials, such as zero-dimensional fullerene, one-dimensional carbon nano tubes and three-dimensional graphene. Due to the unique two-dimensional nanostructure of the graphene, the graphene has a large specific surface area, excellent electronic transmission characteristics, electrical conductivity, thermal conductivity and optical properties, and good chemical stability and mechanical properties, and becomes a research hotspot in the fields of chemistry, physics, materials, mechanics, electronics, biology and the like.
The method for carrying out functional treatment by using high-activity graphene is a common graphene application basic research direction at present, and the common graphene application basic research direction at present comprises chemical modification, element doping, inorganic compounding and the like. The chemical modification mainly comprises introduction of a nitrogen-containing group, a sulfur-containing group, a fluorine-containing group, a chlorine-containing group and the like, the functionalized graphene has potential application prospects in the fields of electronics, biology and medicine, for energetic materials, introduction of an energetic functional group (such as nitrated graphene) on the surface of the graphene can develop novel graphene explosives or energetic additives, and development of solid propellant, propellant powder, explosive and ignition powder technologies is promoted.
The existing nitrated graphene is prepared by taking graphite oxide as a raw material, and the digestibility is lower than 15%, so that the use requirement cannot be met.
Disclosure of Invention
The technical problem solved by the invention is as follows: overcomes the defects of the prior art and provides a method for improving the bonding strength of rubber and fiber fabric.
The technical scheme of the invention is as follows:
a preparation method of nitrated graphene comprises the following steps:
(1) dispersing graphite powder in deionized water to obtain graphite powder suspension, and then adding KMnO4And H2O2Mixing the materials according to a certain mass ratio, adding the mixture into the graphite powder suspension, reacting to obtain gray micro-expanded graphite precipitate, washing, filtering and drying the precipitate for multiple times to obtain micro-expanded graphite flakes, and finally expanding the micro-expanded graphite flakes by microwave excitation to obtain high-activity graphene;
(2) dispersing the high-activity graphene into a solvent to obtain a high-activity graphene dispersion liquid;
(3) mixing concentrated nitric acid and another strong protonic acid according to a certain mass ratio to obtain mixed acid;
(4) placing the high-activity graphene dispersion liquid into a container, distilling under reduced pressure to remove a solvent, and then adding the mixed acid into the container to react for a period of time to obtain a nitrated graphene sol;
(5) and filtering the nitrated graphene sol to obtain nitrated graphene gel, and then purifying, washing, filtering and drying the nitrated graphene gel to obtain nitrated graphene powder.
In an optional embodiment, in the step (1), the graphite powder is placed in deionized water for ultrasonic dispersion for 0.5-2 hours to obtain a graphite powder suspension with the mass concentration of 50-70%.
In an alternative embodiment, KMnO is used in step (1)4And H2O2The mass ratio of (1): 2-4: 1, KMnO4And graphite powder in a mass ratio of 1: 5-2: 1.
in an optional embodiment, the microwave excitation frequency in step (1) is 40 kHz-45 kHz, and the time is 3-10 min.
In an alternative embodiment, the solvent in step (2) is at least one of deionized water, absolute ethanol, acetone, acetonitrile, isopropanol and ethyl acetate.
In an optional embodiment, in the step (2), the high-activity graphene is ultrasonically dispersed into the solvent, wherein the ultrasonic power is 800-2000W, the ultrasonic frequency is 20-50 kHz, and the ultrasonic time is 30-200 min.
In an optional embodiment, the volume concentration of the high-activity graphene dispersion liquid in the step (2) is 0.5mg/mL to 12 mg/mL.
In an alternative embodiment, the strong protic acid in step (3) is concentrated phosphoric acid or perchloric acid, and the mass ratio of the concentrated nitric acid to the strong protic acid is 3: 1-10: 1.
in an optional embodiment, in the step (3), the concentrated nitric acid and the strong protonic acid are mixed at 0-30 ℃, and the mixture is stirred for 5-45 min to obtain the mixed acid.
In an optional embodiment, the mass ratio of the mixed acid to the high-activity graphene in the step (4) is 1: 3-5: 1.
in an optional embodiment, the reaction temperature of the mixed acid and the high-activity graphene in the step (4) is 10-40 ℃, and the reaction time is 60-240 min.
In an alternative embodiment, the purification process of step (5) comprises: under the constant pressure of 12-20V, enabling the nitrated graphene sol to flow through a cation exchange membrane at the flow speed of 20-30L/h for electrodialysis treatment, wherein the circulation time during treatment is 3-8 h, the thickness of the cation exchange membrane is 200-400 mu m, the pore diameter is 0.5-1 nm, and the selective transmittance is 95% -98%; and/or
And (3) generating a driving force for the nitrated graphene gel by using a pressure difference of 0.2-0.5 MPa, and filtering the nitrated graphene gel by using a porous membrane with a pore diameter of 1-2 nm.
In an alternative embodiment, the drying in step (5) comprises vacuum drying, freeze drying and supercritical drying.
In an optional embodiment, the vacuum drying temperature is 20-80 ℃, and the drying time is 2-8 h; the freeze drying time is 8-16 h; the supercritical drying time is 3-10 h.
Compared with the prior art, the invention has the beneficial effects that:
the preparation method of the nitrated graphene provided by the embodiment of the invention takes graphite powder as a raw material and KMnO4And H2O2The combination is used for pretreating graphite powder, then the complete expansion of the micro-expanded graphite powder is ensured through a microwave excitation mode, high-activity graphene with high activity, low oxygen content, good stability and good compatibility is obtained, and when the high-activity graphene is subsequently reacted with mixed acid, the mixed acid is used for carrying out nitration treatment on the high-activity graphene, so that the nitration rate of the nitrated graphene is ensured to be adjustable, and the nitrated graphene with higher nitration rate (up to 50%) is obtained.
Drawings
Fig. 1 is an infrared spectrum of graphene prepared in example 4 of the present invention.
Fig. 2 is an X-ray photoelectron spectrum of graphene prepared in example 4 of the present invention.
Fig. 3 is a scanning electron micrograph of graphene prepared in example 4 of the present invention.
Fig. 4 is a raman spectrum of graphene prepared in example 4 of the present invention.
Detailed Description
The invention is further illustrated by the following examples.
The embodiment of the invention provides a preparation method of nitrated graphene, which comprises the following steps:
step (1): dispersing graphite powder in deionized water to obtain graphite powder suspension, and then adding KMnO4And H2O2Mixing the materials according to a certain mass ratio, adding the mixture into the graphite powder suspension, reacting to obtain gray micro-expanded graphite precipitate, washing, filtering and drying the precipitate for multiple times to obtain micro-expanded graphite flakes, and finally expanding the micro-expanded graphite flakes by microwave excitation to obtain high-activity graphene;
specifically, in the embodiment of the invention, the graphite powder with the particle size of 30-60 μm is preferably selected to ensure that the expansion degrees of the micro-expanded graphite are nearly consistent, which is beneficial to the later ultrasonic treatment;
in an optional example, the graphite powder is placed in deionized water for ultrasonic dispersion for 0.5-2 h to obtain a graphite powder suspension with the mass concentration of 50-70%. The expansion degrees of the micro-expansion graphite are nearly consistent, which is beneficial to the ultrasonic treatment in the later period.
In an alternative example, KMnO is used in this step4And H2O2The mass ratio of (1): 2-4: 1, KMnO4And graphite powder in a mass ratio of 1: 5-2: 1. the proportion can ensure that the graphite powder intercalation expands for later expansion treatment. Further, KMnO in this step4And H2O2The reaction time with the graphite powder is preferably 1-2.5 h.
In an optional example, the microwave excitation frequency in the step is 40 kHz-45 kHz, and the time is 3-10 min. Ensuring that the micro-expanded graphene is fully expanded under the microwave excitation action.
Step (2): dispersing the high-activity graphene into a solvent to obtain a high-activity graphene dispersion liquid;
specifically, in the embodiment of the present invention, the solvent is at least one of deionized water, absolute ethyl alcohol, acetone, acetonitrile, isopropanol, and ethyl acetate.
In an optional example, the step of ultrasonically dispersing the high-activity graphene into the solvent is carried out, wherein the ultrasonic power is 800-2000W, the ultrasonic frequency is 20-50 kHz, and the ultrasonic time is 30-200 min. The high-activity graphene prepared by the invention can be efficiently dispersed by the ultrasonic process, so that the volume concentration of the dispersion liquid can reach 12mg/m, and the problem that the conventional graphene is difficult to disperse is avoided; in an alternative example, the volume concentration of the high-activity graphene dispersion liquid is 0.5 mg/mL-12 mg/mL.
And (3): mixing concentrated nitric acid and another strong protonic acid according to a certain mass ratio to obtain mixed acid;
in the embodiment of the present invention, the strong protic acid is preferably concentrated phosphoric acid or perchloric acid, and the mass ratio of the concentrated nitric acid to the strong protic acid is preferably 3: 1-10: 1; by adjusting the ratio of the concentrated nitric acid to the protonic acid, the mixed acid can achieve the nitration effect of the concentrated nitric acid/concentrated sulfuric acid mixed acid, avoid the danger in the process caused by a concentrated nitric acid/concentrated sulfuric acid mixed acid system and reduce the cost.
In an optional embodiment, the concentrated nitric acid and the strong protonic acid are mixed at 0-30 ℃, and the mixture is stirred for 5-45 min to obtain the mixed acid. The method can ensure that the mixed acid is uniformly mixed, can effectively play the synergistic effect of the mixed acid and the mixed acid, and is beneficial to controlling the nitration degree.
And (4): placing the high-activity graphene dispersion liquid into a container, distilling under reduced pressure to remove a solvent, and then adding the mixed acid into the container to react for a period of time to obtain a nitrated graphene sol;
in an optional embodiment, in the step, the reaction temperature of the mixed acid and the high-activity graphene is 10-40 ℃, the reaction time is 60-240 min, and the mass ratio of the mixed acid to the high-activity graphene is 1: 3-5: 1. when the reaction is carried out under the reaction condition, the safety and the reliability of the reaction can be ensured, and the regulation and the control of the digestion degree and the digestion speed are facilitated.
In the embodiment of the invention, the mixed acid is preferably slowly added into the container at a speed of not more than 10-30 mL/min.
And (5): and filtering the nitrated graphene sol to obtain nitrated graphene gel, and then purifying, washing, filtering and drying the nitrated graphene gel to obtain nitrated graphene powder.
Specifically, the purification treatment described in the embodiment of the present invention includes at least one of electrodialysis and molecular membrane filtration. Specifically, under the constant pressure of 12-20V, the nitrated graphene sol flows through a cation exchange membrane at the flow rate of 20-30L/h for electrodialysis treatment, the circulation time during treatment is 3-8 h, the thickness of the cation exchange membrane is 200-400 microns, the pore diameter is 0.5-1 nm, and the selective transmittance is 95-98%; generating a driving force on the nitrated graphene gel by using a pressure difference of 0.2-0.5 MPa, and filtering the nitrated graphene gel by using a porous membrane with the aperture of 1-2 nm; the purification process can ensure that the purity of the nitrated graphene reaches more than 98 percent and is far higher than that of a product purified by a conventional method, so that the influence of impurities in the nitrated graphene on the compatibility of the nitrated graphene and an energetic material is reduced, and the application reliability of the nitrated graphene is improved;
in the embodiment of the invention, the drying comprises vacuum drying, freeze drying and supercritical drying. Wherein the preferable temperature of vacuum drying is 20-80 ℃, and the drying time is 2-8 h; the freeze drying time is preferably 8-16 h; the supercritical drying time is preferably 3-10 h.
The solvent used for washing in the embodiment of the invention is deionized water, absolute ethyl alcohol, acetone, isopropanol and the like. The filtration mode comprises centrifugal separation, suction filtration and the like.
The preparation method of the nitrated graphene provided by the embodiment of the invention takes graphite powder as a raw material and KMnO4And H2O2The method comprises the following steps of pretreating graphite powder in a combined mode, ensuring the complete expansion of the micro-expanded graphite powder in a microwave excitation mode, obtaining high-activity graphene with high activity, low oxygen content, good stability and good compatibility, and carrying out nitration treatment on the high-activity graphene by using mixed acid when the high-activity graphene reacts with mixed acid in the subsequent reaction, thereby ensuring that the nitration rate of the nitrated graphene is adjustable; obtaining the nitrated graphene with higher nitration rate (up to 50 percent).
The nitrated graphene prepared by the embodiment of the invention not only has partial performance characteristics of graphene, but also has energetic characteristics, and can be directly used as energetic substances of solid propellant, propellant powder, explosive, ignition powder and firework, and also can be used as catalysts of energetic materials such as solid propellant, propellant powder, explosive and the like.
The following are several specific examples of the present invention, and the raw materials used in each example are commercially available products.
Example I
Placing graphite powder with the particle size of 45 mu m in a small amount of water for ultrasonic treatment for 0.5h to form a uniform graphite powder suspension with the mass concentration of 50%, and then adding KMnO4And H2O2According to the mass ratio of 1: 2, mixing and adding the mixture into the graphite powder suspension, wherein KMnO is added4Reacting for 2.5 hours to obtain gray micro-expanded graphite precipitate, then washing the precipitate for three times by using deionized water, filtering and drying to obtain micro-expanded graphite flakes, and finally expanding the micro-expanded graphite flakes by using 40kHz microwave excitation for 10min to obtain the high-activity graphene.
Example II
Placing 30 μm graphite powder in a small amount of water, performing ultrasonic treatment for 1.2 hr to form a uniform 60% suspension, and adding KMnO4And H2O2According to the mass ratio of 2:1, mixing and adding into the graphite powder suspension, wherein KMnO is added4The mass ratio of the graphite powder to the graphite powder is 1: 3, reacting for 1.5h to obtain gray slightly-expanded graphite precipitate, washing, filtering and drying the precipitate for multiple times to obtain slightly-expanded graphite flakes, and finally expanding the slightly-expanded graphite flakes by adopting 45kHz microwave excitation for 6min to obtain the high-activity graphene.
Example III
Putting graphite powder with the particle size of 60 mu m into a small amount of water, performing ultrasonic treatment for 2 hours to form a uniform 70% suspension, and then adding KMnO4And H2O2According to the mass ratio of 4: 1, mixing and adding into the graphite powder suspension, wherein KMnO is added4Reacting for 1h for a period of time to obtain gray micro-expanded graphite precipitate, washing the precipitate for multiple times, filtering and drying to obtain micro-expanded graphite flake, and finally adopting 45kAnd (3) expanding the micro-expanded graphite sheet by Hz microwave excitation for 3min to obtain the high-activity graphene.
Preparing nitrated graphene:
example 1:
step 1: putting the high-activity graphene in the embodiment I into absolute ethyl alcohol, putting the absolute ethyl alcohol in an ultrasonic cell crusher with the power of 1000W and 25kHz, and carrying out ultrasonic treatment for 150min to obtain high-activity graphene ethanol dispersion liquid with good dispersity, wherein the concentration of the high-activity graphene ethanol dispersion liquid is 5 mg/mL;
step 2: under the condition of low-temperature circulating water bath, mixing concentrated nitric acid and concentrated phosphoric acid according to a ratio of 5:1, and slowly stirring for 20min at the temperature of 20-25 ℃ to obtain mixed acid;
and step 3: pouring the high-activity graphene ethanol dispersion liquid into a three-neck flask, distilling under reduced pressure to remove ethanol, placing the solution in a low-temperature reaction bath, and then mixing the solution according to a mass ratio of 1: 1 (mixed acid/high-activity graphene) slowly adding the mixed acid into a three-neck flask, and reacting at 25 ℃ for 120min to obtain nitrated graphene sol;
and 4, step 4: carrying out centrifugal separation on the nitrated graphene sol to obtain nitrated graphene gel, then carrying out electrodialysis treatment on the nitrated graphene gel to remove impurity ions mixed in the nitrated graphene gel, wherein the voltage is 16V, the circulation time is 6h when the nitrated graphene sol is treated at the flow rate of 15L/h, the thickness of the cation exchange membrane is 300 mu m, the pore diameter is 0.7nm, and the selective transmittance is 97%; and finally, washing the mixture for 3 times by using absolute ethyl alcohol, carrying out centrifugal separation, and carrying out vacuum drying for 4 hours at 40 ℃ to obtain the nitrated graphene powder.
Graphene performance: purity (mass ratio of nitrated graphene to high-activity graphene to final material): 98.7%, nitration rate: 38.1 percent.
Example 2:
step 1: putting the high-activity graphene in the acetonitrile in the embodiment II, and putting the high-activity graphene in the acetonitrile, and putting the high-activity graphene in an ultrasonic cell crusher with 1500W and 40kHz for ultrasonic treatment for 60min to obtain high-activity graphene acetonitrile dispersion liquid with good dispersity, wherein the concentration of the high-activity graphene acetonitrile dispersion liquid is 2 mg/mL;
step 2: under the condition of low-temperature circulating water bath, the weight ratio of 8: mixing concentrated nitric acid and concentrated sulfuric acid at a ratio of 1, and slowly stirring for 45min at a temperature of 0-5 ℃ to obtain mixed acid;
and step 3: pouring the high-activity graphene acetonitrile dispersion liquid into a three-neck flask, carrying out reduced pressure distillation to remove acetonitrile, placing the obtained product in a low-temperature reaction bath, and then mixing the obtained product in a mass ratio of 2:1 (mixed acid/high-activity graphene) slowly adding the mixed acid into a three-neck flask, and reacting at 10 ℃ for 240min to obtain a nitrated graphene sol;
and 4, step 4: and carrying out suction filtration on the nitrated graphene sol to obtain nitrated graphene gel, then carrying out molecular membrane filtration treatment on the nitrated graphene gel to remove impurity ions mixed in the nitrated graphene gel, wherein the pressure difference is 0.4MPa, the membrane pore diameter is 1.5nm, and finally washing the nitrated graphene gel for multiple times by using deionized water, and carrying out supercritical drying for 6 hours after suction filtration to obtain nitrated graphene powder.
Graphene performance: purity: 98.3%, nitration rate: 23.9 percent.
Example 3:
step 1: putting the high-activity graphene in the isopropanol in the embodiment I, and putting the high-activity graphene in an ultrasonic cell crusher with the power of 800W and 20kHz for ultrasonic treatment for 180min to obtain high-activity graphene isopropanol dispersion liquid with good dispersibility, wherein the concentration of the high-activity graphene isopropanol dispersion liquid is 8 mg/mL;
step 2: under the condition of low-temperature circulating water bath, the weight ratio of 3: mixing concentrated nitric acid and perchloric acid in a ratio of 1, and slowly stirring for 30min at a temperature of 10-15 ℃ to obtain mixed acid;
and step 3: pouring the high-activity graphene isopropanol dispersion liquid into a three-neck flask, carrying out reduced pressure distillation to remove isopropanol, placing the obtained product in a low-temperature reaction bath, and then mixing the obtained product in a mass ratio of 1: 2 (mixed acid/high-activity graphene) slowly adding the mixed acid into the three-neck flask, and reacting at 30 ℃ for 100min to obtain nitrated graphene sol;
and 4, step 4: carrying out suction filtration on the nitrated graphene sol to obtain nitrated graphene gel, then carrying out electrodialysis treatment on the nitrated graphene gel to remove impurity ions mixed in the nitrated graphene gel, wherein the voltage is 20V, the circulation time is 8h when the nitrated graphene sol is treated at the flow rate of 20L/h, the thickness of the cation exchange membrane is 200 mu m, the pore diameter is 0.5nm, and the selective transmittance is 95%; and finally, washing with isopropanol for multiple times, carrying out suction filtration, and carrying out vacuum drying at 80 ℃ for 2h to obtain the nitrated graphene powder.
Graphene performance: purity: 98.7%, nitration rate: 37.8 percent.
Example 4:
step 1: putting the high-activity graphene in the embodiment III into deionized water, and placing the deionized water in a 1200W and 30kHz ultrasonic cell crusher for ultrasonic treatment for 100min to obtain high-activity graphene aqueous dispersion with good dispersibility, wherein the concentration of the high-activity graphene aqueous dispersion is 10 mg/mL;
step 2: under the condition of low-temperature circulating water bath, the weight ratio of 10: mixing concentrated nitric acid and perchloric acid in a ratio of 1, and slowly stirring for 30min at a temperature of 15-20 ℃ to obtain mixed acid;
and step 3: pouring the high-activity graphene aqueous dispersion into a three-neck flask, carrying out reduced pressure distillation to remove water, placing the obtained product in a low-temperature reaction bath, and then mixing the obtained product in a mass ratio of 5:1 (mixed acid/high-activity graphene) slowly adding the mixed acid into a three-neck flask, and reacting at 20 ℃ for 150min to obtain a nitrated graphene sol;
and 4, step 4: carrying out centrifugal separation on the nitrated graphene sol to obtain nitrated graphene gel, then carrying out electrodialysis and molecular membrane filtration treatment on the nitrated graphene gel to remove impurity ions mixed in the nitrated graphene gel, wherein the voltage during electrodialysis is 12V, the circulation time is 3h when the nitrated graphene sol is treated at the flow rate of 20L/h, the thickness of the cation exchange membrane is 200 mu m, the pore diameter is 0.5nm, the selective transmittance is 95%, the pressure difference during molecular membrane filtration is 0.2MPa, and the membrane pore diameter is 2 nm; and finally, washing with deionized water for three times, performing centrifugal separation, and performing freeze drying for 16 hours to obtain the nitrated graphene powder.
Graphene performance: purity: 99.2%, nitration rate: 26.6 percent.
Example 5:
step 1: putting the high-activity graphene in the embodiment I into acetone, putting the acetone into a 2000W and 50kHz ultrasonic cell crusher, and carrying out ultrasonic treatment for 30min to obtain a high-activity graphene allyl ketone dispersion liquid with good dispersibility, wherein the concentration of the dispersion liquid is 6 mg/mL;
step 2: under the condition of low-temperature circulating water bath, the weight ratio of 3: mixing concentrated nitric acid and perchloric acid in a ratio of 1, and slowly stirring for 5min at a temperature of 25-30 ℃ to obtain mixed acid;
and step 3: pouring the high-activity graphite allyl ketone dispersion liquid into a three-neck flask, distilling under reduced pressure to remove acetone, placing the mixture into a low-temperature reaction bath, and then mixing the obtained product according to a mass ratio of 2:1 (mixed acid/high-activity graphene) slowly adding the mixed acid into a three-neck flask, and reacting at 40 ℃ for 60min to obtain a nitrated graphene sol;
and 4, step 4: carrying out suction filtration on the nitrated graphene sol to obtain nitrated graphene gel, then carrying out electrodialysis treatment on the nitrated graphene gel to remove impurity ions mixed in the nitrated graphene gel, wherein the voltage is 16V, the circulation time is 6h when the nitrated graphene sol is treated at the flow rate of 15L/h, the thickness of the cation exchange membrane is 300 mu m, the pore diameter is 0.7nm, and the selective transmittance is 97%; and finally, washing with acetone for multiple times, performing suction filtration, and performing supercritical drying for 3 hours to obtain the nitrated graphene powder.
Graphene performance: purity: 98.6%, nitration rate: 40.2 percent.
Example 6:
step 1: putting the high-activity graphene in the embodiment II into ethyl acetate, putting the high-activity graphene in a 1200W and 30kHz ultrasonic cell crusher, and performing ultrasonic treatment for 100min to obtain high-activity graphene ethyl acetate dispersion liquid with good dispersibility, wherein the concentration of the high-activity graphene ethyl acetate dispersion liquid is 0.5 mg/mL;
step 2: under the condition of low-temperature circulating water bath, the weight ratio of 5:1, mixing concentrated nitric acid and concentrated phosphoric acid, and slowly stirring for 25min at the temperature of 10-15 ℃ to obtain mixed acid;
and step 3: pouring the high-activity graphene ethyl acetate dispersion liquid into a three-neck flask, carrying out reduced pressure distillation to remove ethyl acetate, placing the obtained product in a low-temperature reaction bath, and then mixing the obtained product according to a mass ratio of 1: 3 (mixed acid/high-activity graphene), slowly adding the mixed acid into the three-neck flask, and reacting at 35 ℃ for 80min to obtain nitrated graphene sol;
and 4, step 4: carrying out centrifugal separation on the nitrated graphene sol to obtain nitrated graphene gel, then carrying out electrodialysis on the nitrated graphene gel to remove impurity ions mixed in the nitrated graphene gel, wherein the voltage is 16V, the circulation time is 6h when the nitrated graphene sol is treated at the flow rate of 15L/h, the thickness of the cation exchange membrane is 300 mu m, the pore diameter is 0.7nm, and the selective transmittance is 97%; and finally, washing with deionized water for multiple times, performing suction filtration, and freeze-drying for 12 hours to obtain the nitrated graphene powder.
Graphene performance: purity: 98.5%, nitration rate: 38.9 percent.
Example 7:
step 1: putting the high-activity graphene in the embodiment III into acetonitrile, placing the acetonitrile in an ultrasonic cell crusher with the power of 1000W and the frequency of 25kHz, and carrying out ultrasonic treatment for 150min to obtain high-activity graphene acetonitrile dispersion liquid with good dispersity, wherein the concentration of the high-activity graphene acetonitrile dispersion liquid is 12 mg/mL;
step 2: under the condition of low-temperature circulating water bath, the weight ratio of 7: 1, mixing concentrated nitric acid and concentrated phosphoric acid, and slowly stirring for 40min at the temperature of 5-10 ℃ to obtain mixed acid;
and step 3: pouring the high-activity graphene acetonitrile dispersion liquid into a three-neck flask, carrying out reduced pressure distillation to remove acetonitrile, placing the obtained product in a low-temperature reaction bath, and then mixing the obtained product in a mass ratio of 4: 1 (mixed acid/high-activity graphene) slowly adding the mixed acid into a three-neck flask, and reacting at 25 ℃ for 150min to obtain a nitrated graphene sol;
and 4, step 4: carrying out suction filtration on the nitrated graphene sol to obtain nitrated graphene gel, then carrying out electrodialysis treatment on the nitrated graphene gel to remove impurity ions mixed in the nitrated graphene gel, wherein the voltage is 16V, the circulation time is 6h when the nitrated graphene sol is treated at the flow rate of 15L/h, the thickness of the cation exchange membrane is 300 mu m, the pore diameter is 0.7nm, and the selective transmittance is 97%; and finally, repeatedly washing with acetonitrile, performing suction filtration, and performing supercritical drying for 10 hours to obtain the nitrated graphene powder.
Graphene performance: purity: 98.8%, nitration rate: 41.6 percent.
Example 8:
step 1: putting the high-activity graphene in the acetonitrile in the embodiment II, and putting the high-activity graphene in the acetonitrile, and putting the high-activity graphene in an ultrasonic cell crusher with 1500W and 40kHz for ultrasonic treatment for 60min to obtain high-activity graphene acetonitrile dispersion liquid with good dispersity, wherein the concentration of the high-activity graphene acetonitrile dispersion liquid is 2 mg/mL;
step 2: under the condition of low-temperature circulating water bath, the weight ratio of 8: mixing concentrated nitric acid and concentrated sulfuric acid at a ratio of 1, and slowly stirring for 45min at a temperature of 0-5 ℃ to obtain mixed acid;
and step 3: pouring the high-activity graphene acetonitrile dispersion liquid into a three-neck flask, carrying out reduced pressure distillation to remove acetonitrile, placing the obtained product in a low-temperature reaction bath, and then mixing the obtained product in a mass ratio of 2:1 (mixed acid/high-activity graphene) slowly adding the mixed acid into a three-neck flask, and reacting at 10 ℃ for 240min to obtain a nitrated graphene sol;
and 4, step 4: and carrying out suction filtration on the nitrated graphene sol to obtain nitrated graphene gel, then carrying out molecular membrane filtration treatment on the nitrated graphene gel to remove impurity ions mixed in the nitrated graphene gel, wherein the pressure difference is 0.4MPa, the membrane pore diameter is 1.5nm, and finally washing the nitrated graphene gel for multiple times by using acetonitrile, carrying out suction filtration, and carrying out vacuum drying for 8 hours at 20 ℃ to obtain nitrated graphene powder.
Graphene performance: purity: 98.0%, nitration rate: 25.3 percent.
Example 9:
step 1: putting the high-activity graphene in the embodiment III into deionized water, and placing the deionized water in an ultrasonic cell crusher with 1500W and 40kHz for ultrasonic treatment for 80min to obtain high-activity graphene aqueous dispersion with good dispersibility, wherein the concentration of the high-activity graphene aqueous dispersion is 8 mg/mL;
step 2: under the condition of low-temperature circulating water bath, the weight ratio of 7: 1, mixing concentrated nitric acid and concentrated phosphoric acid, and slowly stirring for 35min at the temperature of 10-15 ℃ to obtain mixed acid;
and step 3: pouring the high-activity graphene aqueous dispersion into a three-neck flask, carrying out reduced pressure distillation to remove water, placing the obtained product in a low-temperature reaction bath, and then mixing the obtained product in a mass ratio of 3: 1 (mixed acid/high-activity graphene) slowly adding the mixed acid into a three-neck flask, and reacting at 20 ℃ for 180min to obtain a nitrated graphene sol;
and 4, step 4: and carrying out centrifugal separation on the nitrated graphene sol to obtain nitrated graphene gel, then carrying out electrodialysis and molecular membrane filtration treatment on the nitrated graphene gel to remove impurity ions mixed in the nitrated graphene gel, and finally carrying out repeated washing and centrifugal separation on the nitrated graphene gel by deionized water and freeze-drying the nitrated graphene gel for 20 hours to obtain nitrated graphene powder.
Graphene performance: purity: 98.9%, nitration rate: 38.8 percent.
Example 10:
step 1: putting the high-activity graphene in the isopropanol in the embodiment II into a 1200W and 30kHz ultrasonic cell crusher, and carrying out ultrasonic treatment for 100min to obtain a high-activity graphene isopropanol dispersion liquid with good dispersibility, wherein the concentration of the high-activity graphene isopropanol dispersion liquid is 3 mg/mL;
step 2: under the condition of low-temperature circulating water bath, the weight ratio of 9: mixing concentrated nitric acid and concentrated sulfuric acid at a ratio of 1, and slowly stirring for 45min at a temperature of 20-30 ℃ to obtain mixed acid;
and step 3: pouring the high-activity graphene isopropanol dispersion liquid into a three-neck flask, carrying out reduced pressure distillation to remove isopropanol, placing the obtained product in a low-temperature reaction bath, and then mixing the obtained product in a mass ratio of 4: 1 (mixed acid/high-activity graphene) slowly adding the mixed acid into a three-neck flask, and reacting at 30 ℃ for 100min to obtain a nitrated graphene sol;
and 4, step 4: and carrying out suction filtration on the nitrated graphene sol to obtain nitrated graphene gel, then carrying out electrodialysis treatment on the nitrated graphene gel to remove impurity ions mixed in the nitrated graphene gel, and finally washing the nitrated graphene gel for multiple times by using isopropanol, carrying out suction filtration, and carrying out vacuum drying for 5 hours at 50 ℃ to obtain nitrated graphene powder.
Graphene performance: purity: 98.3%, nitration rate: 30.8 percent.
Example 11:
step 1: putting the high-activity graphene in the embodiment III into absolute ethyl alcohol, and putting the absolute ethyl alcohol into an ultrasonic cell crusher with the power of 1800W and 45kHz for ultrasonic treatment for 45min to obtain high-activity graphene ethanol dispersion liquid with good dispersity, wherein the concentration of the high-activity graphene ethanol dispersion liquid is 3 mg/mL;
step 2: under the condition of low-temperature circulating water bath, the weight ratio of 6: mixing concentrated nitric acid and perchloric acid in a ratio of 1, and slowly stirring for 45min at a temperature of 0-5 ℃ to obtain mixed acid;
and step 3: pouring the high-activity graphene ethanol dispersion liquid into a three-neck flask, distilling under reduced pressure to remove ethanol, placing the solution in a low-temperature reaction bath, and then mixing the solution according to a mass ratio of 5:1 (mixed acid/high-activity graphene) slowly adding the mixed acid into a three-neck flask, and reacting at 10 ℃ for 240min to obtain a nitrated graphene sol;
and 4, step 4: and carrying out centrifugal separation on the nitrated graphene sol to obtain nitrated graphene gel, then carrying out molecular membrane filtration treatment on the nitrated graphene gel to remove impurity ions mixed in the nitrated graphene gel, and finally washing the nitrated graphene gel for multiple times by using absolute ethyl alcohol, carrying out centrifugal separation, and carrying out supercritical drying for 5 hours to obtain nitrated graphene powder.
Graphene performance: purity: 98.0%, nitration rate: 40.5 percent.
Example 12:
step 1: putting the high-activity graphene in the embodiment II into acetone, and putting the acetone into an ultrasonic cell crusher with 1500W and 40kHz for ultrasonic treatment for 60min to obtain high-activity graphene allyl ketone dispersion liquid with good dispersibility, wherein the concentration of the dispersion liquid is 5 mg/mL;
step 2: under the condition of low-temperature circulating water bath, the weight ratio of 7: 1, mixing concentrated nitric acid and concentrated phosphoric acid, and slowly stirring for 30min at the temperature of 10-15 ℃ to obtain mixed acid;
and step 3: pouring the high-activity graphite allyl ketone dispersion liquid into a three-neck flask, distilling under reduced pressure to remove acetone, placing the mixture into a low-temperature reaction bath, and then mixing the obtained product according to a mass ratio of 4: 1 (mixed acid/high-activity graphene) slowly adding the mixed acid into a three-neck flask, and reacting at 30 ℃ for 100min to obtain a nitrated graphene sol;
and 4, step 4: and carrying out suction filtration on the nitrated graphene sol to obtain nitrated graphene gel, then carrying out molecular membrane filtration treatment on the nitrated graphene gel to remove impurity ions mixed in the nitrated graphene gel, and finally washing the nitrated graphene gel for multiple times by using acetone, carrying out suction filtration, and then carrying out vacuum drying for 6 hours at 40 ℃ to obtain nitrated graphene powder.
Graphene performance: purity: 98.2%, nitration rate: 38.5 percent.
Although the present invention has been described with reference to the preferred embodiments, it is not intended to limit the present invention, and those skilled in the art can make variations and modifications of the present invention without departing from the spirit and scope of the present invention by using the methods and technical contents disclosed above.
Claims (14)
1. A preparation method of nitrated graphene is characterized by comprising the following steps:
(1) dispersing graphite powder in deionized water to obtain graphite powder suspension, and then adding KMnO4And H2O2Mixing the materials according to a certain mass ratio, adding the mixture into the graphite powder suspension, reacting to obtain gray micro-expanded graphite precipitate, washing, filtering and drying the precipitate for multiple times to obtain micro-expanded graphite flakes, and finally expanding the micro-expanded graphite flakes by microwave excitation to obtain high-activity graphene;
(2) dispersing the high-activity graphene into a solvent to obtain a high-activity graphene dispersion liquid;
(3) mixing concentrated nitric acid and another strong protonic acid according to a certain mass ratio to obtain mixed acid;
(4) placing the high-activity graphene dispersion liquid into a container, distilling under reduced pressure to remove a solvent, and then adding the mixed acid into the container to react for a period of time to obtain a nitrated graphene sol;
(5) and filtering the nitrated graphene sol to obtain nitrated graphene gel, and then purifying, washing, filtering and drying the nitrated graphene gel to obtain nitrated graphene powder.
2. The preparation method of nitrated graphene according to claim 1, characterized in that in the step (1), graphite powder is placed in deionized water for ultrasonic dispersion for 0.5 to 2 hours to obtain a graphite powder suspension with a mass concentration of 50 to 70%.
3. The method for preparing nitrated graphene according to claim 1, wherein KMnO is used in step (1)4And H2O2The mass ratio of (1): 2-4: 1, KMnO4And graphite powder in a mass ratio of 1: 5-2: 1.
4. the preparation method of nitrated graphene according to claim 1, characterized in that the microwave excitation frequency in step (1) is 40kHz to 45kHz, and the time is 3 to 10 min.
5. The method for preparing nitrated graphene according to claim 1, wherein the solvent in step (2) is at least one of deionized water, absolute ethyl alcohol, acetone, acetonitrile, isopropanol and ethyl acetate.
6. The preparation method of the nitrated graphene according to claim 1, characterized in that the high-activity graphene is ultrasonically dispersed into the solvent in the step (2), wherein the ultrasonic power is 800-2000W, the ultrasonic frequency is 20-50 kHz, and the ultrasonic time is 30-200 min.
7. The method for preparing nitrated graphene according to claim 1, wherein the volume concentration of the high-activity graphene dispersion liquid in the step (2) is 0.5mg/mL to 12 mg/mL.
8. The method for preparing nitrated graphene according to claim 1, wherein the strong protic acid in step (3) is concentrated phosphoric acid or perchloric acid, and the mass ratio of the concentrated nitric acid to the strong protic acid is 3: 1-10: 1.
9. the preparation method of the nitrated graphene according to claim 1, characterized in that in the step (3), concentrated nitric acid and strong protonic acid are mixed at 0-30 ℃, and the mixture is stirred for 5-45 min to obtain mixed acid.
10. The method for preparing nitrated graphene according to claim 1, wherein the mass ratio of the mixed acid to the high-activity graphene in the step (4) is 1: 3-5: 1.
11. the method for preparing nitrated graphene according to claim 1, wherein the reaction temperature of the mixed acid and the high-activity graphene in the step (4) is 10-40 ℃, and the reaction time is 60-240 min.
12. The method for preparing nitrated graphene according to claim 1, wherein the purification treatment in the step (5) includes:
under the constant pressure of 12-20V, enabling the nitrated graphene sol to flow through a cation exchange membrane at the flow speed of 20-30L/h for electrodialysis treatment, wherein the circulation time during treatment is 3-8 h, the thickness of the cation exchange membrane is 200-400 mu m, the pore diameter is 0.5-1 nm, and the selective transmittance is 95% -98%; and/or
And (3) generating a driving force for the nitrated graphene gel by using a pressure difference of 0.2-0.5 MPa, and filtering the nitrated graphene gel by using a porous membrane with a pore diameter of 1-2 nm.
13. The method for preparing nitrated graphene according to claim 1, wherein the drying in the step (5) includes vacuum drying, freeze drying and supercritical drying.
14. The preparation method of the nitrated graphene according to claim 13, characterized in that the vacuum drying temperature is 20-80 ℃, and the drying time is 2-8 h; the freeze drying time is 8-16 h; the supercritical drying time is 3-10 h.
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