WO2019109337A1 - 一种类石墨微晶碳纳米材料及其制备方法和应用 - Google Patents

一种类石墨微晶碳纳米材料及其制备方法和应用 Download PDF

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WO2019109337A1
WO2019109337A1 PCT/CN2017/115233 CN2017115233W WO2019109337A1 WO 2019109337 A1 WO2019109337 A1 WO 2019109337A1 CN 2017115233 W CN2017115233 W CN 2017115233W WO 2019109337 A1 WO2019109337 A1 WO 2019109337A1
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graphite
carbon
solution
microcrystalline
carbon nanomaterial
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PCT/CN2017/115233
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English (en)
French (fr)
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左宋林
苗萌
赵允洋
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南京林业大学
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Priority to EP17934109.4A priority Critical patent/EP3572375B1/en
Priority to US16/307,508 priority patent/US11103850B2/en
Priority to JP2019509534A priority patent/JP6762417B2/ja
Priority to PCT/CN2017/115233 priority patent/WO2019109337A1/zh
Priority to CN201780002578.2A priority patent/CN108235703B/zh
Publication of WO2019109337A1 publication Critical patent/WO2019109337A1/zh

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    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
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    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
    • B01J20/00—Solid sorbent compositions or filter aid compositions; Sorbents for chromatography; Processes for preparing, regenerating or reactivating thereof
    • B01J20/30—Processes for preparing, regenerating, or reactivating
    • B01J20/3085—Chemical treatments not covered by groups B01J20/3007 - B01J20/3078
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
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    • C01P2006/40—Electric properties

Definitions

  • the invention relates to the technical field of carbon nano materials, in particular to a graphite-like microcrystalline carbon nano material and a preparation method and application thereof.
  • Carbon nanomaterial refers to a carbon material having at least one dimension of less than 100 nm.
  • Carbon nanomaterials mainly include four types: graphene, carbon nanotubes, carbon nanofibers, and carbon nanospheres.
  • the unique structural characteristics of carbon nanomaterials make them have unusual physical, chemical and mechanical properties. They are considered to be one-dimensional conductors, super-strong composite materials, super-hard materials, hydrogen storage materials, catalysts, catalyst carriers, and high-efficiency adsorption. It has broad application prospects in the fields of agents and absorbing materials, and has been highly valued by researchers.
  • Charcoal, bamboo charcoal, shell charcoal, and conventional carbon materials such as activated carbon and carbon black prepared by their activation are graphite-like microcrystalline carbons, that is, the basic structural unit constituting them is graphite-like crystallites, and its structure is shown in Fig. 1 The figure shows.
  • Graphite-like crystallites refer to crystallites similar in structure to graphite, which are formed by stacking several layers of hexagonal carbon mesh planes in an approximately parallel manner. Graphite-like crystallites range in size from a few nanometers to tens of nanometers, and the size of graphite-like crystallites in charcoal and activated carbon is typically at the level of a few nanometers.
  • nanometer-sized carbon quantum dots capable of generating fluorescence can be prepared by etching an activated carbon and a carbon black surface at a certain temperature using an oxidizing agent such as concentrated nitric acid.
  • an oxidizing agent such as concentrated nitric acid.
  • the invention provides a graphite-like microcrystalline carbon nano material and a preparation method and application thereof.
  • the invention obtains a carbon nanomaterial based on a graphite-like crystallite.
  • the present invention provides a graphite microcrystalline carbon nanomaterial comprising, in terms of 100 parts by mass, 50 to 60 parts of carbon, 30 to 45 parts of oxygen and 1 to 3 parts of hydrogen in a chemical composition;
  • the structural unit of the crystalline carbon nanomaterial is graphite-like crystallite;
  • the graphite-like microcrystalline carbon nanomaterial has a particle diameter of 5 to 10 nm; and
  • the graphite-like microcrystalline carbon nanomaterial is a non-fluorescent carbon nanomaterial.
  • the graphite-like microcrystalline carbon nanomaterial has a thickness of ⁇ 1.5 nm.
  • the graphite-like microcrystalline carbon nano material is a polar carbon nano material.
  • the graphite-like microcrystalline carbon nanomaterial is dispersed in an acidic aqueous solution, an alkaline aqueous solution, and a neutral aqueous solution.
  • the graphite-like microcrystalline carbon nanomaterial contains a carboxyl group, a carbonyl group, a hydroxyl group and an ether group.
  • the invention also provides a preparation method of the graphite-like microcrystalline carbon nano material of the above technical solution, comprising the following steps:
  • the oxidizing agent solution comprising a mixed solution of a first acid and a second acid;
  • One acid is nitric acid and the second acid is perchloric acid or sulfuric acid;
  • the fine suspension obtained in the step (4) is subjected to moisture removal to obtain a graphite-like microcrystalline carbon nanomaterial.
  • the mass ratio of the graphite-like microcrystalline carbon to the oxidant solution is 1 g: (20 to 50) mL;
  • the molar ratio of the first acid to the second acid in the oxidizing agent solution is (0.5 to 2): 1;
  • the oxidizing agent solution is obtained by mixing a first acid solution and a second acid solution, wherein the first acid solution has a mass concentration of 65 to 68%, and the second acid solution has a mass concentration of 70 to 72%;
  • the volume ratio of the monoacid solution to the second acid solution is 1: (0.5 to 2.5).
  • the power of the microwave heating in the step (1) is 500 to 1000 W.
  • the temperature of the microwave heating in the step (1) is 75 to 110 ° C; and the microwave heating time is 10 to 150 min.
  • the graphite-like microcrystalline carbon material in the step (1) comprises one or more of charcoal, bamboo charcoal, shell charcoal, wood activated carbon, nutshell activated carbon, bamboo activated carbon and coal activated carbon.
  • the number of ultrafiltrations in the step (3) is based on the conductivity of the filtrate obtained by ultrafiltration, and when the conductivity of the filtrate obtained by the ultrafiltration reaches 20 us/cm or less, ultrafiltration carry out.
  • the ultrafiltration membrane for ultrafiltration in the step (3) has a molecular weight cut off of 1000 Da.
  • the ultrafiltration after the step (3) further obtains a filtrate; further comprising sequentially concentrating, dialysis and drying the filtrate to obtain fluorescent carbon nanoparticles; and the fluorescent carbon nanoparticles.
  • the particle size is 1 to 3 nm.
  • the separation in the step (4) is centrifugal separation; the number of centrifugation is at least 3 times, and the time of each centrifugation is 10 minutes; the rotation speed of each centrifugation is independently 4000 to 8000 rpm.
  • the micron-sized carbon particles are further obtained after the centrifugal separation of the step (4).
  • the removal of moisture in the step (5) is followed by concentration and drying.
  • the invention provides the graphite-like microcrystalline carbon nano material prepared by the above-mentioned technical solution or the graphite-like microcrystalline carbon nano material prepared by the preparation method described above as a metal ion adsorbent.
  • the invention also provides the application of the graphite-like microcrystalline carbon nano material prepared by the above-mentioned technical solution or the graphite-like microcrystalline carbon nano material prepared by the preparation method of the above technical solution in preparing a carbon nano film.
  • the present invention provides a graphite microcrystalline carbon nanomaterial comprising, in terms of 100 parts by mass, 50 to 60 parts of carbon, 30 to 45 parts of oxygen and 1 to 3 parts of hydrogen in a chemical composition;
  • the crystalline carbon nanomaterial is based on a graphite-like crystallite;
  • the graphite-like microcrystalline carbon nanomaterial has a particle diameter of 5 to 10 nm; and
  • the graphite-like microcrystalline carbon nanomaterial is a non-fluorescent carbon nanomaterial.
  • the invention provides a carbon nanomaterial based on graphite-like crystallites.
  • the invention also provides a method for preparing a graphite microcrystalline carbon nano material, mixing an oxidant solution with a graphite-like microcrystalline carbon, and then heating and oxidizing to obtain an oxidizing solution; wherein the oxidizing agent solution comprises a first acid and a second a mixed solution of acid; the first acid is nitric acid, the second acid is perchloric acid or sulfuric acid; adjusting the pH of the obtained oxidizing solution to 3-8, obtaining a pre-filtration system, and then performing ultrafiltration washing to obtain a suspension The obtained suspension is separated, sequentially subjected to rotary evaporation and dried to obtain a graphite-like microcrystalline carbon nanomaterial.
  • the preparation method provided by the invention adopts the oxidant solution to oxidize the graphite-like microcrystalline carbon under microwave heating, selectively oxidizes and etches the amorphous carbon connected between the graphite-like crystallites, and realizes Dissociation of graphite-like microcrystalline carbon, obtaining carbon nanomaterials with graphite-like crystallites as structural units, avoiding layer-by-layer surface etching of microcrystalline carbon, and improving Preparation efficiency.
  • FIG. 1 is a schematic view showing the oxidizing solution dissociating graphite-like microcrystalline carbon of the oxidizing agent solution of the present invention, wherein a is a graphite-like crystallite, b is a substance connecting graphite-like crystallites, and c is an oxidizing agent solution;
  • Example 2 is an X-ray photoelectron spectroscopy chart of the graphite-like microcrystalline carbon nanomaterial prepared in Example 1 of the present invention
  • FIG. 3 is a fitting diagram of oxygen atom binding energy of an X-ray photoelectron spectroscopy chart of the graphite-like microcrystalline carbon nanomaterial prepared in Example 1 of the present invention
  • Example 4 is an infrared spectrum diagram of a graphite-like microcrystalline carbon nanomaterial prepared in Example 1 of the present invention
  • Example 5 is an atomic force micrograph of a graphite-like microcrystalline carbon nanomaterial prepared in Example 1 of the present invention
  • Example 6 is a graph showing a thickness dimension of an atomic force microscope photograph of a graphite-like microcrystalline carbon nanomaterial prepared in Example 1 of the present invention
  • Example 7 is a TEM image of a graphite-like microcrystalline carbon nanomaterial prepared in Example 1 of the present invention.
  • Example 8 is a view showing a dispersion state of a graphite-like microcrystalline carbon nanomaterial prepared in Example 1 of the present invention in water and methanol;
  • Example 9 is an SEM image of a micron-sized carbon material prepared in Example 1 of the present invention.
  • Example 10 is a TEM image of the fluorescent carbon nanomaterial prepared in Example 1 of the present invention.
  • Example 11 is a dimensional statistical diagram of the fluorescent carbon nanomaterial prepared in Example 1 of the present invention.
  • Example 12 is a fluorescent photograph of a fluorescent carbon nanomaterial prepared in Example 1 of the present invention.
  • Figure 13 is a SEM image of a self-assembled carbon nanofilm of L-CNPs prepared according to the present invention.
  • the present invention provides a graphite microcrystalline carbon nanomaterial comprising, in terms of chemical composition, 50 to 60 parts of carbon, 30 to 45 parts of oxygen and 1 to 3 parts of hydrogen, based on 100 parts by mass.
  • the graphite-like microcrystalline carbon material comprises 50 to 60 parts of carbon, preferably 51 to 55 parts, based on 100 parts by mass of the graphite-like microcrystalline carbon material.
  • the graphite-like microcrystalline carbon material comprises 30 to 45 parts of oxygen, preferably 32 to 40 parts, more preferably 35 to 38 parts, based on 100 parts by mass of the graphite-like microcrystalline carbon material.
  • the graphite-like microcrystalline carbon material comprises 1 to 3 parts of hydrogen, preferably 1.5 to 2.5 parts, and more preferably 2 parts, based on 100 parts by mass of the graphite-like microcrystalline carbon material.
  • the structural unit of the graphite-like microcrystalline carbon nanomaterial is graphite-like crystallite; the graphite-like microcrystalline carbon nanomaterial has a particle diameter of 5 to 10 nm, preferably 6 to 8 nm, and more preferably 6.5. ⁇ 7nm.
  • the thickness of the graphite-like microcrystalline carbon nanomaterial is preferably ⁇ 1.5 nm, preferably ⁇ 1.2 nm.
  • the graphite-like microcrystalline carbon nanomaterial is preferably a polar carbon nanomaterial; the graphite-like microcrystalline carbon nanomaterial can be dispersed in an acidic aqueous solution, a neutral aqueous solution, and an alkaline aqueous solution;
  • the dispersing amount of the microcrystalline carbon nanomaterial in neutral and alkaline water is preferably 40-100 mg/L or more, further preferably 50-80 mg/L; and the dispersion amount of the graphite-like microcrystalline carbon nano material in acidic water reaches 1 mg. /L.
  • the graphite-like microcrystalline carbon nanomaterial cannot be dispersed in a strong polar solvent, for example, cannot be dispersed in methanol or ethanol.
  • the surface of the graphite-like microcrystalline carbon nanomaterial is rich in surface functional groups and has a relatively strong polarity.
  • the graphite-like microcrystalline carbon nanomaterial preferably contains a carboxyl group, a carbonyl group, a hydroxyl group, and an ether group.
  • the graphite-like microcrystalline carbon nanomaterial is a non-fluorescent carbon nanomaterial and has no fluorescence.
  • the invention also provides a preparation method of the graphite-like microcrystalline carbon nano material of the above technical solution, comprising the following steps:
  • the oxidizing agent solution comprising a mixed solution of a first acid and a second acid;
  • the acid is nitric acid and the second acid is perchloric acid or sulfuric acid;
  • the fine suspension obtained in the step (4) is subjected to moisture removal to obtain a graphite-like microcrystalline carbon nanomaterial.
  • the oxidant solution is mixed with the graphite-like microcrystalline carbon material, and the oxidation reaction is carried out under microwave heating to obtain an oxidizing solution.
  • the mass ratio of the graphite-like microcrystalline carbon to the oxidizing agent solution is preferably 1 g: (10 to 40) mL, more preferably 1 g: (15 to 35) mL, and still more preferably 1 g: ( 20 to 30) mL.
  • the oxidizing agent solution includes a mixed solution of a first acid and a second acid; the first acid is nitric acid, and the second acid is perchloric acid or sulfuric acid.
  • the molar ratio of the first acid to the second acid in the oxidizing agent solution is preferably (0.5 to 2): 1, more preferably (0.8 to 1.5): 1, more preferably (1.0 to 1.2): 1.
  • the oxidizing agent solution is preferably obtained by mixing a first acid solution and a secondary solution, and the mass concentration of the first acid solution is preferably 65 to 68%, further preferably 66 to 67%; the second acid The mass concentration of the solution is preferably 70 to 72%, and more preferably 71 to 71.5%.
  • the oxidant solution can penetrate into the interior of the graphite-like microcrystalline carbon without layer-by-layer etching on the surface of the raw material, thereby facilitating the realization of amorphous carbon in the graphite-like microcrystalline carbon in a short time.
  • the oxidative etching causes dissociation of the graphite-like microcrystalline carbon in a short time, and improves the yield and preparation efficiency of the carbon nanomaterial.
  • the graphite-like microcrystalline carbon material preferably comprises biomass carbon, and further preferably comprises one or more of charcoal, bamboo charcoal, nut shell charcoal, wood activated carbon, shell activated carbon, bamboo activated carbon and coal activated carbon.
  • the preparation method of the graphite-like microcrystalline carbon material preferably comprises: carbonizing the biomass material to obtain graphite-like micro Crystal charcoal.
  • the present invention has no special requirements for the specific embodiment of the carbonization, and the biomass carbonization method well known to those skilled in the art can be used.
  • the method for preparing the graphite-like microcrystalline carbon material preferably comprises: activating the biomass raw material to obtain a graphite-like microcrystalline carbon. .
  • the present invention has no special requirements on the preparation method of the activated carbon, and the biomass activation method well known to those skilled in the art can be used.
  • the present invention has no special requirement for the mixing mode of the oxidizing agent solution and the graphite-like microcrystalline carbon material, and the material mixing method well known in the art can be used.
  • the mixed solution in the present invention is subjected to an oxidation reaction under microwave heating to obtain an oxidizing solution.
  • the microwave heating power is preferably 500 to 800 W, more preferably 550 to 750 W; the microwave heating temperature is preferably 75 to 110 ° C, further preferably 80 to 100 ° C; The time is preferably from 10 to 150 min, more preferably from 20 to 120 min, still more preferably from 30 to 60 min.
  • the present invention has no special requirement for the form of the microwave heating, and the microwave heating method well known to those skilled in the art can be used; in the embodiment of the invention, the microwave heating is completed in the microwave synthesizer.
  • the mixed liquid solution realizes the oxidation process of the graphite-like microcrystalline carbon raw material under heating conditions.
  • Graphite-like crystallite The amorphous carbon of the graphite-like crystallites in the carbonaceous raw material is oxidized and etched, and the amorphous carbon which is connected between the graphite-like crystallites is selectively oxidized and etched, and the graphite-like microcrystalline carbon is dissociated.
  • a graphite-like microcrystalline carbon nanomaterial is obtained without layer-by-layer etching of the raw material.
  • a is a graphite-like microcrystalline structural unit
  • b is a substance for connecting graphite-like crystallites
  • c is an oxidizing agent solution.
  • the oxidation reaction is preferably carried out under agitation; the present invention has no particular requirement for the specific embodiment of the agitation to achieve sufficient contact between the graphite-like microcrystalline carbon and the oxidant solution.
  • the present invention preferably cools the oxidized product to room temperature to obtain an oxidizing solution.
  • the present invention has no special requirements for the specific embodiment of the cooling, and a cooling cooling method well known to those skilled in the art can be used.
  • the present invention adjusts the pH of the oxidizing solution obtained by the oxidation reaction to 3 to 8, to obtain a pre-filtration system.
  • the pH adjusting agent is preferably an alkaline solution, and more preferably ammonia water, potassium hydroxide solution or sodium hydroxide solution.
  • the alkaline solution is neutralized with the acid remaining after the oxidation reaction to prevent corrosion of the filter container by the strongly acidic and strongly oxidizing solution.
  • the present invention has no special requirement on the mass concentration and the amount of the alkaline solution, so that the pre-filtration system of the target pH value can be obtained; in the present invention, the pH of the pre-filtration system is 3-8, preferably 6 to 7.
  • the present invention pre-filters the obtained pre-filtration system to obtain a suspension.
  • the number of times of the ultrafiltration is preferably at least one time, and the number of times of the ultrafiltration is preferably based on the conductivity of the filtrate obtained by ultrafiltration, and the conductivity of the filtrate obtained by the ultrafiltration. When it is less than 20us/cm, ultrafiltration is completed.
  • the present invention has no particular requirements for the manner in which the conductivity of the filtrate is tested, and is well known to those skilled in the art.
  • the ultrafiltration membrane for ultrafiltration preferably has a molecular weight cut off of 10,000 Da; the present invention has no particular requirement for the specific source of the ultrafiltration membrane, and a commercially available product of an ultrafiltration membrane well known to those skilled in the art is used. Just fine.
  • the ultrafiltration washing preferably flows the prefiltration system through the ultrafiltration membrane to obtain a filtrate and a retentate; when the filtrate is not colorless and transparent, the conductivity is not lowered to
  • the ultrafiltration membrane is continuously used to carry out ultrafiltration washing on the retentate to obtain a filtrate and a retentate; the ultrafiltration membrane is used to ultrafilter the retentate obtained by continuous washing until the next filtration
  • the conductivity of the liquid is below 20 us/cm, and the filtrate is colorless and transparent at this time.
  • the retentate remaining in the ultrafiltration cup is a suspension.
  • the filtrate is obtained after the ultrafiltration, and the present invention preferably further comprises sequentially concentrating, dialysis and drying the filtrate to obtain fluorescent carbon nanoparticles.
  • the method of concentration is preferably a rotary distillation concentration; the present invention has no special requirement for the manner of the rotary evaporation concentration, and a rotary evaporation concentration method well known to those skilled in the art may be employed.
  • the present invention preferably collects the filtrate obtained by each ultrafiltration washing for the concentration.
  • the obtained concentrate is preferably dialyzed to remove the salt in the concentrate to obtain a purified concentrate.
  • the dialysis membrane for dialysis preferably has a molecular weight cut off of 500 Da.
  • the purified concentrate is preferably dried to obtain fluorescent carbon nanoparticles.
  • the drying is preferably freeze-drying; the present invention has no particular requirement for the specific embodiment of the freeze-drying, and a freeze-drying method well known to those skilled in the art may be employed.
  • the fluorescent carbon nanoparticles preferably have a particle diameter of 1 to 3 nm.
  • the suspension is obtained after the ultrafiltration, and the suspension is separated in the present invention to obtain a fine suspension.
  • the ultrafiltration removes the coarser carbon particles to obtain a suspension containing fine carbon particles, that is, a fine suspension.
  • the separation is preferably centrifugal separation.
  • the number of times of centrifugation is preferably It is at least 3 times, more preferably 4 to 8 times, still more preferably 5 to 6 times; and the time for each centrifugation is preferably 10 minutes.
  • the number of revolutions per centrifugation is independently preferably from 4,000 to 8,000 rpm, further preferably from 4,200 to 8,000 rpm, and more preferably from 5,000 to 6,000 rpm.
  • the separation achieves separation of the micron-sized carbon particles in the suspension from the suspension, thereby obtaining a suspension of carbon particles and micron-sized carbon particles.
  • the obtained fine suspension is subjected to moisture removal to obtain a graphite-like microcrystalline carbon nanomaterial.
  • the present invention has no special requirement for the manner of removing the moisture, and a method capable of removing moisture can be used as known to those skilled in the art.
  • the removal of the moisture is preferably carried out sequentially by concentration and drying; the concentration is further preferably concentrated by rotary evaporation; the drying is preferably heat drying or freeze drying.
  • the pressure of the freeze-drying is preferably 15 Pa or less; and the temperature of the heat drying is preferably 110 °C.
  • the dried material obtained after drying is a graphite-like microcrystalline carbon nanomaterial.
  • the graphite-like microcrystalline carbon material is oxidized to obtain three types of carbon materials: micron-sized carbon materials (CMP), graphite-like microcrystalline carbon materials (L-CNPs), and fluorescent carbon nanomaterials (S). -CNPs); micron-sized carbon materials (CMP) are large-sized carbon particles obtained by centrifugation in a suspension obtained by ultrafiltration of a liquid after oxidation reaction; graphite-like microcrystalline carbon materials (L-CNPs) are ultrafiltered The obtained suspension is separated after the CMP suspension is obtained by drying; the fluorescent carbon nanomaterials (S-CNPs) are obtained by concentrating dialysis and drying the filtrate obtained by ultrafiltration after the oxidation reaction.
  • CMP micron-sized carbon materials
  • L-CNPs graphite-like microcrystalline carbon materials
  • S fluorescent carbon nanomaterials
  • L-CNPs do not have the property of fluorescence, while S-CNPs can fluoresce, the size of S-CNPs is smaller than that of L-CNPs, and the graphite-like microcrystalline carbon raw material carbon also generates carbon dioxide and other gases after being oxidized by the oxidant. This allows for the observation of very pronounced gas product production during the preparation process.
  • the reaction form of the raw material carbon is oxidized as follows: raw material carbon ⁇ MCC+S-CNP+L-CNP+Gaseous products.
  • the invention also provides the application of the graphite-like microcrystalline carbon nano material of the above technical solution as a metal ion adsorbent.
  • the metal ion is preferably copper ion and/or lead ion.
  • the present invention has no special requirements for the application of the graphite-like microcrystalline carbon nanomaterial as a metal ion adsorbent, and an embodiment well known to those skilled in the art can be used.
  • the invention applies the graphite-like microcrystalline carbon nano material to a metal salt solution to realize adsorption of metal ions by the graphite-like microcrystalline carbon nano material, and obtains a metal-carbon nano composite material.
  • the invention also provides the application of the graphite-like microcrystalline carbon nano material of the above technical solution in preparing a carbon nano film.
  • the application of the graphite-like microcrystalline carbon nanomaterial in the preparation of the carbon nano film is preferably self-assembly of the graphite-like microcrystalline carbon nano material into a carbon nano film; the thickness of the carbon nano film is preferably 5 ⁇ 100nm.
  • the reaction solution was cooled to room temperature, and an alkaline solution was added to neutralize the acid solution until the pH of the solution reached 5.
  • the pH-adjusted reaction solution was transferred to an ultrafiltration cup, and the reaction product was subjected to ultrafiltration washing using an ultrafiltration membrane having a molecular weight cut off of 1000 Da until the filtrate became colorless and transparent and the electrical conductivity was less than 20 us/cm. .
  • the suspension in the ultrafiltration cup was repeatedly centrifuged three times in a centrifuge at 4000 rpm for 10 minutes to remove large particles, and the large particles obtained by centrifugation were collected, that is, micron-sized particles (CMP);
  • CMP micron-sized particles
  • the ultrafiltration washing process is collected as a whole, used for rotary evaporation, and then dialyzed to remove the salt in the concentrated filtrate, and finally freeze-dried to obtain small-sized fluorescent carbon nanoparticles (S-CNPs);
  • S-CNPs small-sized fluorescent carbon nanoparticles
  • the centrifuged suspension is subjected to rotary evaporation concentration, and then lyophilized or dried by heating to remove water to obtain graphite-like microcrystalline carbon nanoparticles (L-CNPs).
  • the prepared graphite-like microcrystalline carbon nanoparticles were analyzed by X-ray photoelectron spectroscopy. The test results are shown in Fig. 2; the carbon spectrum fitting analysis of X-ray photoelectron spectroscopy of graphite-like microcrystalline carbon nanomaterials is shown in Fig. 3. Shown. 2 and FIG. 3, the prepared graphite-like microcrystalline carbon nanoparticles are rich in carboxyl groups, carbonyl groups and C-O single bonds.
  • the prepared graphite-like microcrystalline carbon nanoparticles were analyzed by infrared spectroscopy, and the test results are shown in FIG. 4 .
  • the prepared graphite-like microcrystalline carbon nanoparticles contain a strong aromatic ring skeleton vibration peak (1590 cm -1 ), and contain a strong carbonyl vibration peak (1735 cm -1 ), and a stretching vibration peak of the hydroxyl group. (1398cm -1 ). It is shown that the obtained graphite-like microcrystalline carbon nanoparticles contain a large amount of a carboxyl group, a carbonyl group and a hydroxyl group.
  • the prepared graphite-like microcrystalline carbon nanoparticles were subjected to atomic force microscopic analysis, and atomic force micrographs are shown in Fig. 5; statistical analysis was carried out according to the measured particle thickness dimensions in the atomic force micrograph to obtain graphite-like microcrystalline carbon nanoparticles. Size data, as shown in 6. As can be seen from Fig. 6, the prepared carbon nanoparticles have a thickness of not more than 1.5 nm, which is consistent with the graphite-like crystallites usually composed of several layers of hexagonal carbon network planes.
  • the L-CNPs obtained by the present invention have a size of 5 to 10 nm and a thickness of less than 1.5 nm. Moreover, between the micron-sized carbon particles and the L-CNPs below 10 nm, almost no carbon particles having a size between micrometers and 10 nanometers are found, regardless of the reaction temperature and reaction time, even less than 30. At the minute reaction time, there were also no particles sized between micrometers and 10 nanometers. Therefore, it can be confirmed that in the reaction process, carbon particles smaller than 10 nm in size are not formed by surface layer-by-layer etching, but L-CNPs are formed mainly by breaking the connection between the graphite-like crystallites. Carbon particle product (except gas reactants). Moreover, the yield of L-CNPs can reach more than 40%, which is sufficient to show that the L-CNPs are oxides derived from the basic structural unit type graphite crystallites of microcrystalline carbon.
  • the prepared graphite-like microcrystalline carbon nanoparticles were subjected to transmission electron microscopic analysis, and the results are shown in FIG. As can be seen from FIG. 7, the size of the graphite-like microcrystalline carbon nanoparticles prepared is between about 5 and 10 nanometers.
  • the prepared graphite-like microcrystalline carbon nanoparticles were subjected to dispersibility analysis, and the dispersed state in water was as shown in a of FIG. 8; the graphite-like microcrystalline carbon nanoparticles were dispersed in water and allowed to stand for 2 months.
  • the dispersion state of the graphite-like microcrystalline carbon nanoparticles in methanol is as shown in c in Fig. 8. It can be seen from FIG. 8 that the prepared graphite-like microcrystalline carbon nanoparticles can be well dispersed in water to form a suspension, and can be stably existed; but cannot be dispersed in a methanol solvent. It is indicated that the prepared graphite-like microcrystalline carbon nanoparticles have rich surface functional groups and strong polarity.
  • the prepared fluorescent carbon nanoparticles were subjected to transmission electron microscopic analysis. As a result, as shown in Fig. 10, statistical analysis of particle size distribution was carried out for transmission electron microscopic analysis, and the results are shown in Fig. 11. As can be seen in conjunction with Figures 10 and 11, the size of the carbon nanoparticles is less than 3 nm.
  • the prepared fluorescent nanoparticles were subjected to fluorescence analysis, and the test results are shown in Fig. 12. As is apparent from Fig. 12, the nanoparticles were fluorescent.
  • the preparation of the carbon material was carried out in the same manner as in Example 1 except that the stirring reaction under microwave heating was carried out for 30 minutes.
  • the preparation of the carbon material was carried out in the same manner as in Example 1 except that the stirring reaction under microwave heating was carried out for 10 minutes.
  • the preparation of the carbon material was carried out in the same manner as in Example 1 except that the stirring reaction time under microwave heating was 90 min.
  • the preparation of the carbon material was carried out in the same manner as in Example 1 except that the stirring reaction time under microwave heating was 120 min.
  • CMP micron-sized particles
  • S-CNPs fluorescent carbon nanoparticles
  • L-CNPs graphite-like microcrystalline carbon nanoparticles
  • the conversion rate of carbon atoms in the raw material carbon it can be seen from Table 1 that after the raw material carbon is oxidized for 30 minutes, the carbon atoms in the raw material are mainly converted into L-CNPs and gas products, and the amount of larger particles CMP and the smallest size particles S-CNPs. Rarely, the nano-carbon material of L-CNPs accounts for 50% of the carbon atom conversion rate of the raw material carbon (oxidation time is 30 min), and the conversion rate can reach 30% even when the oxidation time is 120 min.
  • the prepared carbon nanomaterials of L-CNPs contain 53 to 55%, 34 to 35.3% of oxygen content, and have a hydrogen content of more than 2.0%, indicating that L-CNPs contain a large amount of oxygen. group.
  • the carbon, oxygen, nitrogen and hydrogen contents of the prepared L-CNPs remain substantially unchanged.
  • the ratio of C:O:H of the L-CNPs prepared at different oxidation times is basically unchanged, which indicates that the L-CNPs prepared from the same raw material carbon have the same chemical composition and structure, and the particle size.
  • the size is basically the same. Because if the particle size is reduced, it will inevitably cause a significant change in the proportion of C:O elements.
  • L-CNPs are carbon nanomaterials based on graphite-like crystallites.
  • nitric acid and perchloric acid according to the ratio of the amount of the substance to 1:1, mixing the nitric acid solution and the perchloric acid solution according to a volume ratio of 1:1.1, and preparing an oxidizing agent solution, wherein the mass concentration of the nitric acid solution is 65%.
  • the mass concentration of the perchloric acid solution was 70%.
  • the reaction solution was cooled to room temperature, and an alkaline solution was added to neutralize the acid solution until the pH of the solution reached 5.
  • the pH-adjusted reaction solution was transferred to an ultrafiltration cup, and the reaction product was subjected to ultrafiltration washing using an ultrafiltration membrane having a molecular weight cut off of 1000 Da until the filtrate became colorless and transparent and the electrical conductivity was less than 20 us/cm. .
  • the suspension in the ultrafiltration cup was repeatedly centrifuged three times in a centrifuge at 4000 rpm for 10 minutes to remove large particles, and the large particles obtained by centrifugation were collected, which were micron-sized particles; each ultrafiltration was washed.
  • the process filtrate is collected and integrated for rotary evaporation, and then the salt is removed by dialysis to remove the salt in the concentrated filtrate.
  • the small-sized fluorescent carbon nanoparticles are obtained by lyophilization; the suspension after centrifugation is rotated. The mixture is evaporated to a concentration, and then lyophilized or dried by heating to remove water to obtain carbon nanoparticles.
  • the preparation of the carbon material was carried out in the same manner as in Example 6 except that the temperature at the microwave heating was 80 °C.
  • the preparation of the carbon material was carried out in the same manner as in Example 6 except that the temperature at the microwave heating was 90 °C.
  • the preparation of the carbon material was carried out in the same manner as in Example 6 except that the temperature at the microwave heating was 100 °C.
  • CMP micron-sized particles
  • S-CNPs fluorescent carbon nanoparticles
  • L-CNPs graphite-like microcrystalline carbon nanoparticles
  • the reaction solution was cooled to room temperature, and an alkaline solution was added to neutralize the acid solution until the pH of the solution reached 5.
  • the pH-adjusted reaction solution was transferred to an ultrafiltration cup, and the reaction product was subjected to ultrafiltration washing using an ultrafiltration membrane having a molecular weight cut off of 1000 Da until the filtrate became colorless and transparent and the electrical conductivity was less than 20 us/cm. .
  • the suspension in the ultrafiltration cup was repeatedly centrifuged three times in a centrifuge at 4000 rpm for 10 minutes to remove large particles, and the large particles obtained by centrifugation were collected, which were micron-sized particles; each ultrafiltration was washed.
  • the process filtrate is collected and integrated for rotary evaporation, and then the salt is removed by dialysis to remove the salt in the concentrated filtrate.
  • the small-sized fluorescent carbon nanoparticles are obtained by lyophilization; the suspension after centrifugation is rotated. The mixture is evaporated to a concentration, and then lyophilized or dried by heating to remove water to obtain carbon nanoparticles.
  • the preparation of the carbon material was carried out in the same manner as in Example 11 except that the ratio of the amount of the nitric acid to the perchloric acid in the oxidizing agent solution was 1:1.
  • the preparation of the carbon material was carried out in the same manner as in Example 11 except that the ratio of the amount of the nitric acid to the perchloric acid in the preparation of the oxidizing agent solution was 2:1.
  • the yields of micron-sized particles (CMP), fluorescent carbon nanoparticles (S-CNPs) and graphite-like microcrystalline carbon nanoparticles (L-CNPs) prepared in Examples 10 to 12 were respectively tested and calculated.
  • the mass of carbon atoms in the product / the mass of carbon atoms in the raw material carbon, the yield of carbon atoms in the raw materials converted to various products at different reaction times are obtained, and the results are shown in Table 5.
  • Table 5 the ratio of the two acids in the mixed acid significantly affects the oxidation of the carbon and the yield of various products.
  • the ratio of the amounts of the two acids is 1:1
  • the yield of L-CNPs is the highest, reaching 68.4%
  • the carbon atoms contained therein account for 40.5% of the carbon atoms of the raw carbon.
  • the reaction solution was cooled to room temperature, and an alkaline solution was added to neutralize the acid solution until the pH of the solution reached 5.
  • the pH-adjusted reaction solution was transferred to an ultrafiltration cup, and the reaction product was subjected to ultrafiltration washing using an ultrafiltration membrane having a molecular weight cut off of 1000 Da until the filtrate became colorless and transparent and the electrical conductivity was less than 20 us/cm. .
  • the suspension in the ultrafiltration cup was repeatedly centrifuged three times in a centrifuge at 4000 rpm for 10 minutes to remove large particles, and the large particles obtained by centrifugation were collected, which were micron-sized particles; each ultrafiltration was washed.
  • the process filtrate is collected and integrated for rotary evaporation, and then the salt is removed by dialysis to remove the salt in the concentrated filtrate.
  • the small-sized fluorescent carbon nanoparticles are obtained by lyophilization; the suspension after centrifugation is rotated. The mixture is evaporated to a concentration, and then lyophilized or dried by heating to remove water to obtain carbon nanoparticles.
  • Example 13 The preparation of the carbon material was carried out in the same manner as in Example 13 except that the coconut shell activated carbon used in Example 11 was replaced with a wood charcoal.
  • Example 13 The preparation of the carbon material was carried out in the same manner as in Example 13 except that the coconut shell activated carbon used in Example 11 was replaced with fir activated carbon.
  • L-CNP with a yield of more than 40% can be prepared by using different activated carbons and carbonized materials.
  • a mixture of 65% by mass of nitric acid and 95% of sulfuric acid in a ratio of the amount of the substance was 1:1.
  • the reaction solution was cooled to room temperature, and an alkaline solution was added to neutralize the acid solution until the pH of the solution reached 5. Will adjust the pH
  • the reaction solution was transferred to an ultrafiltration cup, and the reaction product was subjected to ultrafiltration washing using an ultrafiltration membrane having a molecular weight cut off of 1000 Da until the filtrate became colorless and transparent and the electrical conductivity was less than 20 us/cm.
  • the suspension in the ultrafiltration cup was repeatedly centrifuged three times in a centrifuge at 4000 rpm for 10 minutes to remove large particles, and the large particles obtained by centrifugation were collected, which were micron-sized particles; each ultrafiltration was washed.
  • the process filtrate is collected and integrated for rotary evaporation, and then the salt is removed by dialysis to remove the salt in the concentrated filtrate.
  • the small-sized fluorescent carbon nanoparticles are obtained by lyophilization; the suspension after centrifugation is rotated. The mixture is evaporated to a concentration, and then lyophilized or dried by heating to remove water to obtain carbon nanoparticles.
  • the obtained CMP was 0.186 g
  • L-CNPs was 2.474 g
  • S-CNPs was 0.045 g.
  • the carbon, oxygen and hydrogen contents of the obtained L-CNPs were 56.8%, 29.4% and 1.03%, respectively.
  • the graphite-like microcrystalline carbon nanoparticles prepared in Examples 2 to 16 were analyzed by infrared spectroscopy, and the test results were consistent with those in FIG. 4 . It is also clear that the obtained graphite-like microcrystalline carbon nanoparticles contain a large amount of a carboxyl group, a carbonyl group, and a hydroxyl group.
  • the prepared graphite-like microcrystalline carbon nanoparticles were subjected to atomic force microscopic analysis, and statistically analyzed according to the measured particle size in the atomic force micrograph, and the thickness of the graphite-like microcrystalline carbon nanoparticles was not more than 1.5 nm.
  • Graphite-like crystallites are generally composed of several layers of hexagonal carbon network planes.
  • the present invention provides a kind of graphite microcrystalline carbon nano material and a preparation method thereof, and the invention obtains a carbon nano material with graphite-like crystallite as a structural unit.
  • the preparation method provided by the invention can realize the oxidative etching of the graphite-like microcrystalline carbon by using an oxidizing agent solution under microwave heating conditions for only 10 to 100 minutes, thereby achieving selective oxidation etching and connection.
  • the amorphous carbon between the graphite-like crystallites dissociates to obtain the graphite-like microcrystalline carbon nanomaterial, which eliminates the need for layer-by-layer etching of the raw material, thereby improving the preparation efficiency, which is far lower than that in the prior art in order to complete the oxidation etching. Time-consuming time of more than 10 hours.
  • the pH of the mixture was adjusted to 6.9 with a 5 mol/L sodium hydroxide solution and a nitric acid solution, and the volume of the added sodium hydroxide solution and the nitric acid solution was measured using a graduated cylinder, and the volume difference before and after the addition was the amount of addition.
  • the total volume of the added liquid is reported as V a (mL).
  • the centrifuge tube containing the mixture was placed in a constant temperature oscillating bed, and kept at a constant temperature of 25 ° C for 24 hours, and the oscillation rate was 150 times per minute.
  • the mixture was centrifuged (3000 r/min), and the supernatant was filtered using a 220 nm nylon filter.
  • the concentration of Pb 2+ in the filtrate was measured by atomic absorption spectrometry as the equilibrium concentration after adsorption, and recorded as C. e (mg/L).
  • the graphite-like microcrystalline carbon nanomaterial provided by the invention has a high adsorption amount to the lead ions in the solution, especially in the high concentration metal ion solution, the graphite-like carbon nano material provided by the invention.
  • the amount of lead ion adsorbed is 10 times that of its own mass, almost 10 times that of ordinary adsorbent materials.
  • the pH of the mixture was adjusted to 4.6 with a 5 mol/L sodium hydroxide solution and a nitric acid solution, and the volume of the added sodium hydroxide solution and the nitric acid solution was measured using a graduated cylinder, and the volume difference before and after the addition was the amount of addition.
  • the total volume of the added liquid is reported as V a (mL).
  • the centrifuge tube containing the mixture was placed in a constant temperature oscillating bed, and kept at a constant temperature of 25 ° C for 24 hours, and the oscillation rate was 150 times per minute.
  • the mixture was centrifuged (3000 r/min), and the supernatant was filtered using a 220 nm nylon filter.
  • the concentration of Cu 2+ in the filtrate was measured by atomic absorption spectrometry, and the equilibrium concentration after adsorption was recorded as C. e (mg/L).
  • the graphite-like microcrystalline carbon nanomaterial provided by the present invention is also very high for copper ions in solution.
  • the amount of adsorption It is much higher than the adsorption amount of porous carbon materials such as activated carbon, and they are usually only a few tens of mg/g; quite or slightly better than the adsorption amount of copper ions such as graphene oxide.
  • Example 19 The solid carbon nanomaterial obtained by freeze-drying L-CNPs was in the form of a sheet having a width of several tens of micrometers or more, but the thickness was only about 100 nanometers.
  • the results of scanning electron microscopy analysis are shown in FIG. It is shown that these graphite-like microcrystalline carbon nanomaterials dispersed in aqueous solution have the tendency of self-loading into nano-films in the process of losing water, and have potential application for making carbon nano-films.

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Abstract

提供一种类石墨微晶碳纳米材料及其制备方法和应用。该类石墨微晶碳纳米材料是以类石墨微晶为结构单元的碳纳米材料，以100份质量计，在化学组成上包括50~60份的碳，30~50份的氧和1~3份的氢；尺寸为5~10nm；属于非荧光性碳纳米材料。该制备方法包括采用氧化剂溶液对类石墨微晶质炭进行选择性氧化，刻蚀掉连接于类石墨微晶之间的无定形炭，实现解离类石墨微晶质炭的目的，得到类石墨微晶碳纳米材料。其可用于金属离子吸附剂或制备碳纳米薄膜。

Description

一种类石墨微晶碳纳米材料及其制备方法和应用 技术领域
本发明涉及碳纳米材料技术领域，尤其涉及一种类石墨微晶碳纳米材料及其制备方法和应用。
背景技术
碳纳米材料是指至少有一维小于100nm的碳材料。碳纳米材料主要包括四种类型：石墨烯，碳纳米管，碳纳米纤维，碳纳米球。碳纳米材料独特的结构特征，使其具有不同寻常的物理、化学和机械性能等，被认为在一维传导器、超强复合材料、超硬材料、储氢材料、催化剂、催化剂载体、高效吸附剂以及吸波材料等领域中具有广阔的应用前景，受到研究者的高度重视。
木炭、竹炭、果壳炭以及由它们活化制备的活性炭、炭黑等传统炭材料，都是类石墨微晶质炭，即构成它们的基本结构单元是类石墨微晶，其结构见图1左图所示。类石墨微晶是指与石墨结构类似的微晶，是由几层六角形碳网平面以近似平行的方式堆积而成。类石墨微晶的尺寸在几个纳米到几十个纳米之间，木炭和活性炭中类石墨微晶的尺寸通常在几个纳米水平。
对于类石墨微晶质炭，可以采用机械研磨的方法将其减少至几百纳米或几十纳米尺寸，其能耗非常高，且研磨过程中无法控制其颗粒尺寸与形貌。或者使用浓硝酸等氧化剂，在一定温度下采用长时间刻蚀活性炭和炭黑表面的方法制备几个纳米大小的能产生荧光的碳量子点。但这些方法都无法实现解离类石墨微晶质炭，制备出以类石墨微晶作为结构基础的碳纳米材料。
发明内容
本发明提供一种类石墨微晶碳纳米材料及其制备方法和应用。本发明得到了以类石墨微晶为结构基础的碳纳米材料。
为了解决上述技术问题，本发明公开了以下技术方案：
本发明提供了一种类石墨微晶碳纳米材料，以100份质量计，在化学组成上包括50～60份的碳，30～45份的氧和1～3份的氢；所述类石墨微晶碳纳米材料的结构单元为类石墨微晶；所述类石墨微晶碳纳米材料的粒径为5～10nm；所述类石墨微晶碳纳米材料为非荧光性碳纳米材料。
优选的，所述类石墨微晶碳纳米材料的厚度≤1.5nm。
优选的，所述类石墨微晶碳纳米材料为极性碳纳米材料。
优选的，所述类石墨微晶碳纳米材料在酸性水溶液、碱性水溶液和中性水溶液中进行分散。
优选的，所述类石墨微晶碳纳米材料含有羧基、羰基、羟基和醚基。
本发明还提供了上述技术方案所述类石墨微晶碳纳米材料的制备方法，包含如下步骤：
(1)将类石墨微晶质炭原料与氧化剂溶液混合，在微波加热条件下，进行氧化反应，得到氧化料液；所述氧化剂溶液包括第一酸和第二酸的混合溶液；所述第一酸为硝酸，所述第二酸为高氯酸或硫酸；
(2)调节所述步骤(1)得到的氧化料液的pH值至3～8；得到预过滤体系；
(3)将所述步骤(2)得到的预过滤体系进行超滤，得到悬浮液和滤出液；
(4)将所述步骤(3)得到的悬浮液进行分离，得到细密悬浮液；
(5)对所述步骤(4)得到的细密悬浮液进行水分的去除，得到类石墨微晶碳纳米材料。
优选的，所述类石墨微晶质炭的质量和氧化剂溶液的体积比为1g：(20～50)mL；
所述氧化剂溶液中第一酸和第二酸的摩尔比为(0.5～2)：1；
所述氧化剂溶液由第一酸溶液和第二酸溶液混合得到，所述第一酸溶液的质量浓度为65～68％，所述第二酸溶液的质量浓度为70～72％；所述第一酸溶液和第二酸溶液的体积比为1：(0.5～2.5)。
优选的，所述步骤(1)中微波加热的功率为500～1000W。
优选的，所述步骤(1)中微波加热的温度为75～110℃；所述微波加热时间为10～150min。
优选的，所述步骤(1)中类石墨微晶质炭原料包括木炭、竹炭、果壳炭、木质活性炭、果壳活性炭、竹活性炭和煤质活性炭中的一种或多种。
优选的，所述步骤(3)中超滤的次数以超滤得到的滤出液的电导率为准，当所述超滤得到的滤出液的电导率达到20us/cm以下时，超滤完成。
优选的，所述步骤(3)中超滤用超滤膜的截留分子量为1000Da。
优选的，所述步骤(3)的超滤后还得到滤出液；还包括对所述滤出液依次进行浓缩、透析和干燥，得到荧光性碳纳米颗粒；所述荧光性碳纳米颗粒的粒径为1～3nm。
优选的，所述步骤(4)中分离为离心分离；所述离心分离的次数至少为3次，每次离心分离的时间为10min；每次离心分离的转速独立地在4000～8000rpm。
优选的，所述步骤(4)的离心分离后还得到微米级炭颗粒。
优选的，所述步骤(5)中的水分的去除为依次进行浓缩和干燥。
本发明提供了上述技术方案所述类石墨微晶碳纳米材料或上述技术方案所述制备方法制备的类石墨微晶碳纳米材料作为金属离子吸附剂的应用。
本发明还提供了上述技术方案所述类石墨微晶碳纳米材料或上述技术方案所述制备方法制备的类石墨微晶碳纳米材料在制备碳纳米薄膜中的应用。
本发明提供了一种类石墨微晶碳纳米材料，以100质量份计，在化学组成上包括50～60份的碳，30～45份的氧和1～3份的氢；所述类石墨微晶碳纳米材料是以类石墨微晶作为结构基础；所述类石墨微晶碳纳米材料的粒径为5～10nm；所述类石墨微晶碳纳米材料为非荧光性碳纳米材料。本发明提供了一种以类石墨微晶为结构基础的碳纳米材料。
本发明还提供了一种类石墨微晶碳纳米材料的制备方法，将氧化剂溶液与类石墨微晶质炭混合，然后加热进行氧化，得到氧化料液；其中，氧化剂溶液包括第一酸和第二酸的混合溶液；第一酸为硝酸，第二酸为高氯酸或硫酸；调节所得到的氧化料液的pH值至3～8，得到预过滤体系后，进行超滤洗涤，得到悬浮液；再将所得到的悬浮液依次进行分离、旋蒸浓缩和干燥，得到类石墨微晶碳纳米材料。本发明提供的制备方法，采用所述氧化剂溶液在微波加热条件下对类石墨微晶质炭进行氧化，有选择性地氧化刻蚀掉连接于类石墨微晶之间的无定形炭，实现了类石墨微晶质炭的解离，得到类石墨微晶为结构单元的碳纳米材料，避免了对微晶质炭的逐层表面刻蚀，提高了 制备效率。
说明书附图
图1为本发明氧化剂溶液氧化解离类石墨微晶质炭的示意图，其中，a为类石墨微晶，b为连接类石墨微晶的物质，c为氧化剂溶液；
图2为本发明实施例1制备得到的类石墨微晶碳纳米材料的X射线光电子能谱图；
图3为本发明实施例1制备得到的类石墨微晶碳纳米材料的X射线光电子能谱图的氧原子结合能的拟合图；
图4为本发明实施例1制备得到的类石墨微晶碳纳米材料的红外光谱图；
图5为本发明实施例1制备得到的类石墨微晶碳纳米材料的原子力显微照片；
图6为本发明实施例1制备得到的类石墨微晶碳纳米材料的原子力显微镜照片图片的厚度尺寸统计曲线图；
图7为本发明实施例1制备得到的类石墨微晶碳纳米材料的TEM图；
图8为本发明实施例1制备得到的类石墨微晶碳纳米材料在水和甲醇中的分散状态图；
图9为本发明实施例1制备得到的微米级碳材料的SEM图；
图10为本发明实施例1制备得到的荧光性碳纳米材料的TEM图；
图11为本发明实施例1制备得到的荧光性碳纳米材料的尺寸统计图；
图12为本发明实施例1制备得到的荧光性碳纳米材料的荧光照片；
图13为本发明制备得到的L-CNPs自组装成的碳纳米薄膜的SEM图。
具体实施方式
本发明提供了一种类石墨微晶碳纳米材料，以100份质量计，在化学组成上，包括50～60份的碳，30～45份的氧和1～3份的氢。在本发明中，以所述类石墨微晶碳材料总质量100份计，所述类石墨微晶碳材料包括50～60份的碳，优选为51～55份。在本发明中，以所述类石墨微晶碳材料总质量100份计，所述类石墨微晶碳材料包括30～45份氧，优选为32～40份，进一步优选为35～38份。在本发明中，以所述类石墨微晶碳材料总质量100份计，所述类石墨微晶碳材料包括1～3份的氢，优选为1.5～2.5份，进一步优选为2份。
在本发明中，所述类石墨微晶碳纳米材料的结构单元为类石墨微晶；所述类石墨微晶碳纳米材料的粒径为5～10nm，优选为6～8nm，进一步优选为6.5～7nm。在本发明中，所述类石墨微晶碳纳米材料的厚度优选≤1.5nm，优选≤1.2nm。
在本发明中，所述类石墨微晶碳纳米材料优选为极性碳纳米材料；所述类石墨微晶碳纳米材料能够分散于酸性水溶液、中性水溶液和碱性水溶液中；所述类石墨微晶碳纳米材料在中性和碱性水中的分散量优选达到40～100mg/L以上，进一步优选为50～80mg/L；所述类石墨微晶碳纳米材料在酸性水中的分散量达到1mg/L。在本发明中，所述类石墨微晶碳纳米材料不能分散于强极性溶剂中，例如不能分散于甲醇或乙醇中。
在本发明中，所述类石墨微晶碳纳米材料表面含有丰富的表面官能团，极性较强。在本发明中，所述类石墨微晶碳纳米材料优选含有羧基、羰基、羟基和醚基。
在本发明中，所述类石墨微晶碳纳米材料为非荧光性碳纳米材料，没有荧光性。
本发明还提供了上述技术方案所述类石墨微晶碳纳米材料的制备方法，包含如下步骤：
(1)将氧化剂溶液与类石墨微晶质炭原料混合，在加热条件下，进行氧化反应，得到氧化料液；所述氧化剂溶液包括第一酸和第二酸的混合溶液；所述第一酸为硝酸，所述第二酸为高氯酸或硫酸；
(2)调节所述步骤(1)得到的氧化料液的pH值至3～8；得到预过滤体系；
(3)将所述步骤(2)得到的预过滤体系进行超滤，得到悬浮液和滤出液；
(4)将所述步骤(3)得到的悬浮液进行分离，得到细密悬浮液；
(5)将所述步骤(4)得到的细密悬浮液进行水分的去除，得到类石墨微晶碳纳米材料。
本发明将氧化剂溶液与类石墨微晶质炭原料混合，在微波加热条件下，进行氧化反应，得到氧化料液。
在本发明中，所述类石墨微晶质炭的质量和氧化剂溶液的体积比优选为1g：(10～40)mL，进一步优选为1g：(15～35)mL，更优选为1g：(20～30)mL。
在本发明中，所述氧化剂溶液包括第一酸和第二酸的混合溶液；所述第一酸为硝酸，所述第二酸为高氯酸或硫酸。在本发明中，所述氧化剂溶液中第一酸和第二酸的摩尔比优选为(0.5～2)：1，进一步优选为(0.8～1.5)：1，更优选为(1.0～1.2)：1。在本发明中，所述氧化剂溶液优选由第一酸溶液和辅溶液混合得到，所述第一酸溶液的质量浓度优选为65～68％，进一步优选为66～67％；所述第二酸溶液的质量浓度优选为70～72％，进一步优选为71～71.5％。在本发明中，所述氧化剂溶液能够渗透到类石墨微晶质炭的内部，无需在原料表面逐层氧化逐层刻蚀，便于在短时间内实现对类石墨微晶质炭中无定形炭的氧化刻蚀，从而在短时间内导致类石墨微晶质炭的解离，提高碳纳米材料的得率和制备效率。
在本发明中，所述类石墨微晶质炭原料优选包括生物质炭，进一步优选包括木炭、竹炭、果壳炭、木质活性炭、果壳活性炭、竹活性炭和煤质活性炭中的一种或多种。在本发明中，当所述类石墨微晶质炭原料为木炭、竹炭或果壳炭时，所述类石墨微晶质炭原料的制备方法优选包括：将生物质原料进行炭化得到类石墨微晶质炭。本发明对所述炭化的具体实施方式没有特殊要求，采用本领域技术人员所熟知的生物质炭化方式即可。当所述类石墨微晶质炭原料为木质活性炭、果壳活性炭或竹活性炭时，所述类石墨微晶质炭原料的制备方法优选包括：将生物质原料进行活化得到类石墨微晶质炭。本发明对所述活性炭的制备方式没有特殊要求，采用本领域技术人员所熟知的生物质活化方式即可。
本发明对所述氧化剂溶液与类石墨微晶质炭原料的混合方式没有特殊要求，采用本领域所熟知的物料混合方式即可。
所述混合后，本发明将所述混合后的料液在微波加热条件下，进行氧化反应，得到氧化料液。在本发明中，所述微波加热的功率优选为500～800W，进一步优选为550～750W；所述微波加热的温度优选为75～110℃，进一步优选为80～100℃；所述微波加热的时间优选为10～150min，进一步优选为20～120min，更优选为30～60min。本发明对所述微波加热的提供形式没有特殊要求，采用本领域技术人员所熟知的微波加热方式即可；在本发明的实施例中，所述微波加热在微波合成仪中完成。
如图1氧化剂溶液氧化解离类石墨微晶质炭的示意图所示，在本发明中，所述混合后的料液在加热条件下实现对类石墨微晶质炭原料的氧化过程，将所述类石墨微晶 质炭原料中连接类石墨微晶的无定形碳氧化刻蚀掉，实现了有选择性地氧化刻蚀掉连接于类石墨微晶之间的无定形炭，解离类石墨微晶质炭，得到类石墨微晶碳纳米材料，无需对原料进行逐层刻蚀。图1中，a为类石墨微晶结构单元，b为连接类石墨微晶的物质，c为氧化剂溶液。
在本发明中，所述氧化反应优选在搅拌条件下进行；本发明对所述搅拌的具体实施方式没有特殊要求，以能实现类石墨微晶质炭和氧化剂溶液的充分接触即可。
所述氧化反应后，本发明优选将所述氧化后的产物冷却至室温，得到氧化料液。本发明对所述冷却的具体实施方式没有特殊要求，采用本领域技术人员所熟知的降温冷却方式即可。
得到氧化料液后，本发明调节所述氧化反应得到的氧化料液的pH值至3～8，得到预过滤体系。在本发明中，所述pH值的调节剂优选为碱性溶液，进一步优选为氨水、氢氧化钾溶液或氢氧化钠溶液。在本发明中，所述碱性溶液与所述氧化反应后剩余的酸发生中和反应，防止强酸性和具有强氧化性的溶液对过滤容器的腐蚀。本发明对所述碱性溶液的质量浓度和用量没有特殊要求，以能得到目标pH值的预过滤体系即可；在本发明中，所述预过滤体系的pH值为3～8，优选为6～7。
得到预过滤体系后，本发明将所述得到的预过滤体系进行超滤，得到悬浮液。在本发明中，所述超滤的次数优选至少为一次，所述超滤的次数优选以超滤得到的滤出液的电导率为准，当所述超滤得到的滤出液的电导率低于20us/cm时，超滤完成。本发明对所述滤出液电导率的测试方式没有特殊要求，采用本领域技术人员所熟知的即可。在本发明中，所述超滤用超滤膜的截留分子量优选为10000Da；本发明对所述超滤膜的具体来源没有特殊要求，采用本领域技术人员所熟知的超滤膜的市售商品即可。在本发明中，所述超滤洗涤优选为将所述预过滤体系流经所述超滤膜，得到滤出液和截留液；当所述滤出液并非无色透明且电导率未降低至20us/cm以下时，继续采用所述超滤膜对截留液进行超滤洗涤，得到滤出液和截留液；采用所述超滤膜对不断洗涤得到的截留液进行超滤，直至当次滤出液电导率在20us/cm以下为止，此时滤出液是无色透明的。在本发明中，当超滤完毕后，保留在超滤杯的截留液为悬浮液。
所述超滤后得到滤出液，本发明优选还包括对所述滤出液依次进行浓缩、透析和干燥，得到荧光性碳纳米颗粒。在本发明中，所述浓缩的方式优选为旋蒸浓缩；本发明对所述旋蒸浓缩的方式没有特殊要求，采用本领域技术人员所熟知的旋蒸浓缩方式即可。当所述超滤洗涤的次数不止一次时，本发明优选收集每次超滤洗涤得到的滤出液，用于所述浓缩。
所述浓缩后，本发明优选将所得到的浓缩液进行透析，去除浓缩液中的盐分，得到提纯浓缩液。在本发明中，所述透析用透析膜的截留分子量优选为500Da。
本发明优选对所述提纯浓缩液进行干燥，得到荧光性碳纳米颗粒。在本发明中，所述干燥优选为冷冻干燥；本发明对所述冷冻干燥的具体实施方式没有特殊要求，采用本领域技术人员所熟知的冷冻干燥方式即可。在本发明中，所述荧光性碳纳米颗粒的粒径优选为1～3nm。
所述超滤后得到悬浮液，本发明将所述悬浮液进行分离，得到细密悬浮液。在本发明中，所述超滤除去较粗的炭颗粒，得到含有细小炭颗粒的悬浮液，即为细密悬浮液。在本发明中，所述分离优选为离心分离。在本发明中，所述离心分离的次数优选 至少为3次，进一步优选为4～8次，更优选为5～6次；每次离心分离的时间优选为10min。在本发明中，每次离心分离的转速独立地优选在4000～8000rpm，进一步优选为4200～8000rpm，更优选为5000～6000rpm。在本发明中，所述分离实现所述悬浮液中微米级碳颗粒从悬浮液中分离，从而得到炭颗粒的悬浮液和微米级碳颗粒。
本发明对所述得到的细密悬浮液进行水分去除，得到类石墨微晶碳纳米材料。本发明对所述水分的去除方式没有特殊要求，采用本领域技术人员所熟知的能够实现水分的去除的方式即可。在本发明中，所述水分的去除优选为依次进行浓缩和干燥；所述浓缩进一步优选为旋蒸浓缩；所述干燥优选为加热干燥或冷冻干燥。在本发明的实施例中，所述冷冻干燥的压力优选在15Pa以下；所述加热干燥的温度优选为110℃。在本发明中，所述干燥后得到的干燥料即类石墨微晶碳纳米材料。
在本发明中，所述类石墨微晶质炭原料被氧化后得到三类碳材料：微米级碳材料(CMP)，类石墨微晶碳材料(L-CNPs)以及荧光性碳纳米材料(S-CNPs)；微米级碳材料(CMP)是从氧化反应后的料液超滤得到的悬浮液中离心分离得到的大尺寸炭颗粒；类石墨微晶碳材料(L-CNPs)是将超滤得到的悬浮液分离出CMP后的悬浮液经干燥后得到；荧光性碳纳米材料(S-CNPs)是通过氧化反应后对超滤得到的滤出液经浓缩透析和干燥得到。其中L-CNPs不具有发生荧光的性质，而S-CNPs能够发生荧光，S-CNPs的尺寸比L-CNPs小；并且类石墨微晶质炭原料炭在被氧化剂氧化后还产生了二氧化碳等气体，这在制备过程中能观察非常明显的气体产物产生。原料炭被氧化的反应形式如下：原料炭→MCC+S-CNP+L-CNP+Gaseous products。
本发明还提供了上述技术方案所述类石墨微晶碳纳米材料作为金属离子吸附剂的应用。在本发明中，所述金属离子优选为铜离子和/或铅离子。本发明对所述类石墨微晶碳纳米材料作为金属离子吸附剂的应用方式没有特殊要求，采用本领域技术人员所熟知的实施方式即可。
本发明将所述类石墨微晶碳纳米材料投加到金属盐溶液中，实现类石墨微晶碳纳米材料对金属离子的吸附，得到金属-碳纳米复合材料。
本发明还提供了上述技术方案所述类石墨微晶碳纳米材料在制备碳纳米薄膜中的应用。在本发明中，所述类石墨微晶碳纳米材料在制备碳纳米薄膜中的应用优选为所述类石墨微晶碳纳米材料自组装成碳纳米薄膜；所述碳纳米薄膜的厚度优选为5～100nm。
下面结合实施例对本发明提供的类石墨微晶碳纳米材料及其制备方法和应用进行详细的说明，但是不能把它们理解为对本发明保护范围的限定。
实施例1
将硝酸与高氯酸按照物质的量之比为1：1的比例混合，将酸A溶液与酸B溶液按照体积比1:1.1混合配制氧化剂溶液，其中硝酸溶液的质量浓度为65％，高氯酸溶液的质量浓度为70％。
将4.00g的60～80目的椰壳活性炭与100mL的氧化剂溶液混合，将混合液放入微波合成仪中，在微波功率为500W下加热至100℃，搅拌反应60min后停止加热；
将反应液冷却至室温，加入碱性溶液中和酸液至溶液的pH值达到5。将调好pH的反应液转移至超滤杯中，使用截留分子量为1000Da的超滤膜对反应物进行超滤洗涤，直至滤出液变为无色透明且电导率低于20us/cm时为止。
将超滤杯中的悬浮液在转速4000rpm的离心机中重复离心分离3次，每次10min，除去大的颗粒，收集离心分离得到的大颗粒，即为微米级颗粒(CMP)；将每次超滤洗涤过程滤出液收集为一体，用于旋蒸浓缩，然后透析除去浓缩的滤出液中盐分，最后经冷冻干燥后得到小粒径的荧光性碳纳米颗粒(S-CNPs)；将离心分离后的悬浮液进行旋蒸浓缩，然后冷冻干燥或加热干燥的方式除去水分，得到类石墨微晶碳纳米颗粒(L-CNPs)。
对制备得到的类石墨微晶碳纳米颗粒进行X射线光电子能谱分析，测试结果如图2所示；类石墨微晶碳纳米材料的X射线光电子能谱的碳谱拟合分析图如图3所示。由图2和图3可知，制备得到的类石墨微晶碳纳米颗粒含有丰富的羧基、羰基与C-O单键。
将制备得到的类石墨微晶碳纳米颗粒进行红外光谱分析，测试结果如图4所示。
由图4可知，制备得到的类石墨微晶碳纳米颗粒含有较强的芳环骨架振动峰(1590cm-1)，而且含有较强的羰基振动峰(1735cm-1)，以及羟基的伸缩振动峰(1398cm-1)。表明，得到的类石墨微晶碳纳米颗粒中含有大量的羧基、羰基以及羟基。
将制备得到的类石墨微晶碳纳米颗粒进行原子力显微分析，原子力显微照片如5所示；根据测得的原子力显微照片中颗粒厚度尺寸进行统计分析，得到类石墨微晶碳纳米颗粒的尺寸数据，如6所示。由图6可知，所制备的碳纳米颗粒的厚度尺寸不超过1.5纳米，与类石墨微晶通常由几层六角形碳网平面所构成一致。
本发明得到的L-CNPs的大小尺寸为5～10纳米宽，厚度小于1.5纳米。并且，在微米级炭颗粒与10纳米以下的L-CNPs之间，几乎没有发现任何尺寸在微米与10纳米之间的炭颗粒，不管是在哪种反应温度和反应时间下，即使是小于30分钟反应时间下，也没有尺寸在微米与10纳米颗粒之间的颗粒。因此，可以肯定，在反应过程中，不是通过表面逐层刻蚀达到制备出小于10纳米尺寸的炭颗粒，而是通过断开类石墨微晶之间的连接，形成了L-CNPs为主要的炭颗粒产物(除气体反应物外)。而且，L-CNPs的得率能够达到40％以上，足以说明其L-CNPs是来源于微晶质炭的基本结构单位类石墨微晶的氧化物。
将制备得到的类石墨微晶碳纳米颗粒进行透射电子显微分析，结果如图7所示。由图7可知，所制备的类石墨微晶碳纳米颗粒的尺寸在5～10纳米左右之间。
将制备得到的类石墨微晶碳纳米颗粒进行分散性分析，在水中的分散状态如图8中的a所示；将类石墨微晶碳纳米颗粒分散于水中，静置2个月后的状态如图8中的b所示；类石墨微晶碳纳米颗粒在甲醇中的分散状态如图8中c所示。由图8可知，制备得到的类石墨微晶碳纳米颗粒可以很好的分散在水中，形成悬浮液，并且能够稳定存在；但不能分散在甲醇溶剂中。表明，制备得到的类石墨微晶碳纳米颗粒表面含有丰富的表面官能团，极性较强。
对制备得到的微米级碳颗粒进行扫描电镜扫描，结果如图9所示；由图9可知，碳颗粒的尺寸在微米级水平。
对制备得到的荧光性碳纳米颗粒进行透射电子显微分析，结果如图10所示，针对透射电子显微分析进行粒径分布统计分析，结果如11所示。结合图10和图11可知，该碳纳米颗粒的尺寸小于3nm。对制备得到的荧光性纳米颗粒进行荧光分析，测试结果如图12所示，由图12可知，该纳米颗粒具有荧光性。
实施例2
按照实施例1的方式进行碳材料的制备，区别在于，在微波加热条件下的搅拌反应的时间30min。
实施例3
按照实施例1的方式进行碳材料的制备，区别在于，在微波加热条件下的搅拌反应的时间10min。
实施例4
按照实施例1的方式进行碳材料的制备，区别在于，在微波加热条件下的搅拌反应的时间90min。
实施例5
按照实施例1的方式进行碳材料的制备，区别在于，在微波加热条件下的搅拌反应的时间120min。
分别将实施例1～5制备得到的微米级颗粒(CMP)、荧光性碳纳米颗粒(S-CNPs)和类石墨微晶碳纳米颗粒(L-CNPs)产率进行测试计算，产率＝产物的质量/原料炭的质量，得到不同反应时间下，三种产物的产率，结果如表1所示。
分别将实施例1～5制备得到的微米级颗粒(CMP)、荧光性碳纳米颗粒(S-CNPs)和类石墨微晶碳纳米颗粒(L-CNPs)的得率进行测试计算，得率＝产物中碳原子的质量/原料炭中碳原子的质量，得到不同反应时间下，原料中碳原子转换为各类产物的得率，结果如表1所示。
表1 实施例1～5中三种产物的产率以及原料中碳原子转换为各类产物的得率数值
Figure PCTCN2017115233-appb-000001
由表1可知，当反应时间延长到30分钟时，尤其是10分钟到30分钟之间，L-CNPs产物的得率急剧增大，达到77.85％，而CMP的得率急剧减少，S-CNP的得率很低，几乎可以忽略不计。即原料炭在氧化过程中，除生成了气体产物外，主要得到了L-CNPs。这说明，原料炭的氧化不是通过表面刻蚀，逐渐减少炭颗粒粒径直至10纳米以下的；而是通过选择性氧化连接微晶的无定形炭，使大的炭颗粒解体，释放出以类石墨微晶 为基础的碳纳米材料，即L-CNPs。
根据原料炭中碳原子的转化率，由表1可知，原料炭氧化30分钟后，原料中的碳原子主要转化为L-CNPs和气体产物，较大颗粒CMP和最小尺寸颗粒S-CNPs的量很少，L-CNPs的纳米炭材料占原料炭的碳原子转化率可以达到50％(氧化时间为30min)，即使在氧化时间为120min的情况下，其转化率也能达到30％。因此，很明显，在很短的氧化时间里，就可以制备得到大量的L-CNPs纳米颗粒；而且，可以看出，当氧化时间从10min延长到30min时，原料炭能够非常快速地解离成纳米颗粒L-CNPs。这说明氧化剂渗透到炭结构内部，在短时间内氧化刻蚀掉连接类石墨微晶的无定形炭，从而在短时间内导致类石墨微晶炭的解离。
分别对实施例1～5制备得到的类石墨微晶碳纳米颗粒(L-CNPs)进行元素分析，结果如表2所示。
表2 实施例1～5制备得到的类石墨微晶碳纳米颗粒的元素含量
Figure PCTCN2017115233-appb-000002
由表2可知，所制备的L-CNPs新型碳纳米材料含有53～55％，34～35.3％的氧含量，且有大于2.0％的氢元素含量，说明L-CNPs中含有大量的含氧基团。不管氧化时间长短，所制备的L-CNPs的碳元素、氧元素、氮元素和氢元素含量基本保持不变。这表明在不同氧化时间下所制备的L-CNPs的C:O:H的比值基本不变，这充分说明由同一种原料炭所制备的L-CNPs具有相同的化学组成与结构，而且粒径大小也基本保持不变。因为如果粒径减少，必然引起C:O元素的比例发生较明显变化。这也进一步说明，L-CNPs是基于类石墨微晶得到的碳纳米材料。
实施例6
将硝酸与高氯酸按照物质的量之比为1：1的比例混合，将硝酸溶液与高氯酸溶液按照体积比1:1.1，混合配制氧化剂溶液，其中硝酸溶液的质量浓度为65％，高氯酸溶液的的质量浓度为70％。
将4.00g的椰壳活性炭与100mL的氧化剂溶液混合，将混合液放入微波合成仪中，在微波功率为500W下加热至70℃，搅拌反应60min后停止加热，得到反应液；
将反应液冷却至室温，加入碱性溶液中和酸液至溶液的pH值达到5。将调好pH的反应液转移至超滤杯中，使用截留分子量为1000Da的超滤膜对反应物进行超滤洗涤，直至滤出液变为无色透明且电导率低于20us/cm时为止。
将超滤杯中的悬浮液在转速4000rpm的离心机中重复离心分离3次，每次10min，除去大的颗粒，收集离心分离得到的大颗粒，即为微米级颗粒；将每次超滤洗涤过程滤出液收集为一体，用于旋蒸浓缩，然后透析除去浓缩的滤出液中盐分，最后经冷冻干燥后得到小粒径的荧光性碳纳米颗粒；将离心分离后的悬浮液进行旋蒸浓缩，然后冷冻干燥或加热干燥的方式除去水分，得到碳纳米颗粒。
实施例7
按照实施例6的方式进行碳材料的制备，区别在于，在微波加热的温度为80℃。
实施例8
按照实施例6的方式进行碳材料的制备，区别在于，在微波加热的温度为90℃。
实施例9
按照实施例6的方式进行碳材料的制备，区别在于，在微波加热的温度为100℃。
分别将实施例6～9制备得到的微米级颗粒(CMP)、荧光性碳纳米颗粒(S-CNPs)和类石墨微晶碳纳米颗粒(L-CNPs)产率进行测试计算，产率＝产物的质量/原料炭的质量，得到不同反应时间下，三种产物的得率，结果如表3所述。
分别将实施例6～9制备得到的微米级颗粒(CMP)、荧光性碳纳米颗粒(S-CNPs)和类石墨微晶碳纳米颗粒(L-CNPs)的得率进行测试计算，得率＝产物中碳原子的质量/原料炭中碳原子的质量，得到不同反应时间下，原料中碳原子转换为各类产物的得率，结果如表3所示。
表3 实施例6～9中三种产物的产率以及原料中碳原子转换为各类产物的得率数值
Figure PCTCN2017115233-appb-000003
从表3可以看出，当温度低于70℃时，氧化反应仅仅发生在炭的表面，氧化反应不能得到纳米尺寸的炭颗粒。当温度上升到80℃时，开始获得大于10％的L-CNP，但没有发现S-CNP，此时，原料炭颗粒基本还没有破裂，主要以微米级的炭颗粒存在。90℃下，L-CNP碳纳米材料获得了77％的得率，超过了其它任何产物的得率。从碳原子的转化率来看，原料中有44％的碳原子转化为L-CNP。随着氧化温度的进一步升高，L-CNP的得率减少，S-CNP有所增多。
分别对实施例6～9制备得到的类石墨微晶碳纳米颗粒(L-CNPs)进行元素分析，结果如表4所示。
表4 实施例6～9制备得到的类石墨微晶碳纳米颗粒的元素分析结果
Figure PCTCN2017115233-appb-000004
Figure PCTCN2017115233-appb-000005
与表2相似，在不同反应温度下所制备的L-CNP的碳、氧、氢和氮元素含量都基本相似，表明在不同温度下所制备的L-CNP的C:O:H的比值基本不变，再一次说明由同一种原料炭所制备的L-CNP具有高度相似的化学组成与结构，而且粒径大小也基本保持不变。
实施例10
将硝酸与高氯酸按照物质的量之比为1:2的比例混合，将硝酸溶液与高氯酸溶液按照体积比1:2.2混合配制氧化剂溶液，其中硝酸溶液的质量浓度为65％，高氯酸的质量浓度为70％。
将4.00g的椰壳活性炭与100mL的氧化剂溶液混合，将混合液放入微波合成仪中，在微波功率为500W下加热至100℃，搅拌反应60min后停止加热。
将反应液冷却至室温，加入碱性溶液中和酸液至溶液的pH值达到5。将调好pH的反应液转移至超滤杯中，使用截留分子量为1000Da的超滤膜对反应物进行超滤洗涤，直至滤出液变为无色透明且电导率低于20us/cm时为止。
将超滤杯中的悬浮液在转速4000rpm的离心机中重复离心分离3次，每次10min，除去大的颗粒，收集离心分离得到的大颗粒，即为微米级颗粒；将每次超滤洗涤过程滤出液收集为一体，用于旋蒸浓缩，然后透析除去浓缩的滤出液中盐分，最后经冷冻干燥后得到小粒径的荧光性碳纳米颗粒；将离心分离后的悬浮液进行旋蒸浓缩，然后冷冻干燥或加热干燥的方式除去水分，得到碳纳米颗粒。
实施例11
按照实施例11的方式进行碳材料的制备，区别在于，氧化剂溶液中硝酸与高氯酸的物质的量之比为1:1。
实施例12
按照实施例11的方式进行碳材料的制备，区别在于，氧化剂溶液制备中硝酸与高氯酸的物质的量之比为2:1。
分别将实施例10～12制备得到的微米级颗粒(CMP)、荧光性碳纳米颗粒(S-CNPs)和类石墨微晶碳纳米颗粒(L-CNPs)的得率进行测试计算，得率＝产物中碳原子的质量/原料炭中碳原子的质量，得到不同反应时间下，原料中碳原子转换为各类产物的得率，结果如表5所示。由表5可知，混合酸中两种酸的比值明显影响炭的氧化和各种产物的得率。当两种酸的物质的量的比值为1:1时，L-CNPs的得率最高，达到68.4％，其所含的碳原子占原料炭的碳原子的40.5％。
表5 实施例10～12中原料中碳原子转换为各类产物的得率数值
Figure PCTCN2017115233-appb-000006
Figure PCTCN2017115233-appb-000007
分别对实施例10～12制备得到的类石墨微晶碳纳米颗粒(L-CNPs)进行元素分析，结果如表6所示。
表6 实施例10～12制备得到的类石墨微晶碳纳米颗粒的元素分析结果
Figure PCTCN2017115233-appb-000008
由表6可知，不同混酸所制备的L-CNP的碳元素、氧元素、氮元素和氢元素差别不大。并与不同反应时间和反应温度下制备的L-CNP具有相似的元素含量，进一步表明它们具有相似的结构，来源相同，都是类石墨微晶的氧化衍生物。
实施例13
将硝酸与高氯酸按照物质的量之比为1：1的比例混合，将硝酸溶液与高氯酸溶液按照体积比1:1.1混合配制氧化剂溶液，其中硝酸溶液的质量浓度为65％，高氯酸的质量浓度为70％。
将4.00g的60～80目的椰壳活性炭与100mL的氧化剂溶液混合，将混合液放入微波合成仪中，在微波功率为500W下加热至100℃，搅拌反应60min后停止加热；
将反应液冷却至室温，加入碱性溶液中和酸液至溶液的pH值达到5。将调好pH的反应液转移至超滤杯中，使用截留分子量为1000Da的超滤膜对反应物进行超滤洗涤，直至滤出液变为无色透明且电导率低于20us/cm时为止。
将超滤杯中的悬浮液在转速4000rpm的离心机中重复离心分离3次，每次10min，除去大的颗粒，收集离心分离得到的大颗粒，即为微米级颗粒；将每次超滤洗涤过程滤出液收集为一体，用于旋蒸浓缩，然后透析除去浓缩的滤出液中盐分，最后经冷冻干燥后得到小粒径的荧光性碳纳米颗粒；将离心分离后的悬浮液进行旋蒸浓缩，然后冷冻干燥或加热干燥的方式除去水分，得到碳纳米颗粒。
实施例14
按照实施例13的方式进行碳材料的制备，区别在于，将实施例11中所用的椰壳活性炭替换为木质炭化料。
实施例15
按照实施例13的方式进行碳材料的制备，区别在于，将实施例11中所用的椰壳活性炭替换为杉木活性炭。
分别将实施例13～15制备得到的微米级颗粒(CMP)、荧光性碳纳米颗粒(S-CNPs) 和类石墨微晶碳纳米颗粒(L-CNPs)产率进行测试计算，产率＝产物的质量/原料炭的质量，得到不同反应时间下，三种产物的得率，结果如表7所示。
分别将实施例13～15制备得到的微米级颗粒(CMP)、荧光性碳纳米颗粒(S-CNPs)和类石墨微晶碳纳米颗粒(L-CNPs)的得率进行测试计算，得率＝产物中碳原子的质量/原料炭中碳原子的质量，得到不同反应时间下，原料中碳原子转换为各类产物的得率，结果如表7所示。
表7 实施例13～15中三种产物的产率以及原料中碳原子转换为各类产物的得率数值
Figure PCTCN2017115233-appb-000009
由表7可知，采用不同的活性炭与炭化料都可以制备得到得率超过40％的L-CNP。
分别对实施例13～15制备得到的类石墨微晶碳纳米颗粒(L-CNPs)进行元素分析，结果如表8所示。
表8 实施例13～15制备得到的类石墨微晶碳纳米颗粒的元素分析结果
Figure PCTCN2017115233-appb-000010
从表8可以看出，不同原料所制备的L-CNP的元素含量差别明显。而前面的实施例都是采用同一种原料炭，它在不同的温度、两种酸的用量以及反应时间所制备的L-CNP几乎都具有相同的碳、氧元素含量。这是由于不同原料炭中的类石墨微晶结构有差异造成。这进一步证明了L-CNP是来源于类石墨微晶。
实施例16
将质量百分比65％硝酸与95％的硫酸按照物质的量之比为1：1的比例混合。
将4.00g的椰壳活性炭与100mL的混酸溶液混合，将混合液放入微波合成仪中，在微波功率为500W条件下加热至100℃，搅拌反应30min后停止加热，得到反应液；
将反应液冷却至室温，加入碱性溶液中和酸液至溶液的pH值达到5。将调好pH 的反应液转移至超滤杯中，使用截留分子量为1000Da的超滤膜对反应物进行超滤洗涤，直至滤出液变为无色透明且电导率低于20us/cm时为止。
将超滤杯中的悬浮液在转速4000rpm的离心机中重复离心分离3次，每次10min，除去大的颗粒，收集离心分离得到的大颗粒，即为微米级颗粒；将每次超滤洗涤过程滤出液收集为一体，用于旋蒸浓缩，然后透析除去浓缩的滤出液中盐分，最后经冷冻干燥后得到小粒径的荧光性碳纳米颗粒；将离心分离后的悬浮液进行旋蒸浓缩，然后冷冻干燥或加热干燥的方式除去水分，得到碳纳米颗粒。
得到的CMP为0.186g,L-CNPs为2.474g,S-CNPs为0.045g。制得的L-CNPs的碳、氧、氢元素含量分别为56.8％，29.4％和1.03％。
分别对实施例2～16制备得到类石墨微晶碳纳米材料进行X射线光电子能谱分析，测试结果与实施例1测试结果一致，可知，制备得到的类石墨微晶碳纳米颗粒含有丰富的羧基、羰基与C-O单键，其中C-C含量占71.86％，C-O为12.82％，C＝O为1.65％，COO为13.67％。
分别对实施例2～16制备得到的类石墨微晶碳纳米颗粒进行红外光谱分析，测试结果与图4一致。同样能够明确，得到的类石墨微晶碳纳米颗粒中含有大量的羧基、羰基以及羟基。
将制备得到的类石墨微晶碳纳米颗粒进行原子力显微分析，并根据测得的原子力显微照片中颗粒尺寸进行统计分析，得到类石墨微晶碳纳米颗粒的厚度尺寸不超过1.5纳米，与类石墨微晶通常由几层层六角形碳网平面所构成一致。
并对实施例2～16制备得到的类石墨微晶碳纳米颗粒进行透射电子显微分析，可知，制备得到的类石墨微晶碳纳米颗粒的尺寸在5～10纳米左右之间。
对实施例2～16制备得到的类石墨微晶碳纳米颗粒进行分散性分析，可知能够分散于水中，并能稳定存在，但不能分散于甲醇中。
由以上实施例可知，本发明提供了一种类石墨微晶碳纳米材料及其制备方法，本发明得到了以类石墨微晶为结构单元的碳纳米材料。本发明提供的制备方法，采用氧化剂溶液在微波加热条件下仅需要10～100min的氧化时间即可实现对类石墨微晶质炭进行氧化刻蚀，实现了有选择性地氧化刻蚀掉连接于类石墨微晶之间的无定形炭，解离得到类石墨微晶碳纳米材料，无需对原料进行逐层刻蚀，提高了制备效率，远低于现有技术中为了完成氧化刻蚀的耗时10小时以上的耗时时间。
实施例17
分别配制浓度为0.00125mol/L，0.0025mol/L，0.005mol/L，0.01mol/L，0.02mol/L，0.04mol/L，0.08mol/L的硝酸铅溶液，并用原子吸收光谱仪测定Pb2+的准确浓度，作为Pb2+初始浓度，记为Ci(mg/mL)。
依次量取25mL上述不同浓度的硝酸铅溶液，并分别装入单独的离心管中，然后每个离心管中加入25mg L-CNPs并使之混合均匀。
用5mol/L的氢氧化钠溶液和硝酸溶液调节混合物的pH值为6.9，加入的氢氧化钠溶液和硝酸溶液体积使用量筒计量，加入前后的体积差即为加入量。加入液体的总体积记为Va(mL)。
将盛有混合物的离心管置于恒温震荡床内，保持25℃恒温震荡24h，震荡速率为每分钟震荡150次。
震荡结束后对混合物进行离心(3000r/min)，并使用220nm的尼龙滤头对上清液进行过滤，使用原子吸收光谱仪测定滤液的Pb2+的浓度，作为吸附后的平衡浓度，记为Ce(mg/L)。
每个初始浓度下，当L-CNPs对Pb2+的吸附达到平衡后的吸附量Qe(mg/g)按照以下公式计算：Qe＝1000(25Ci-Ce(25+Va))/25，吸附效果如表9所示。
表9 实施例17中L-CNPs对Pb2+的吸附效果数据
初始浓度mg/L 平衡浓度mg/L 吸附量mg/g
16560.0 4592.0 11279.2
8352.0 3447.2 4604.0
4244.0 2117.2 2045.6
1944.4 603.0 1325.6
972.6 59.2 912.6
471.3 0 471.3
由表9可知，本发明提供的类石墨微晶碳纳米材料对溶液中的铅离子都有很高的吸附量，尤其是在高浓度的金属离子溶液中，本发明提供的类石墨碳纳米材料对铅离子的吸附量达到本身质量的10倍之多，几乎是普通吸附材料的10倍之多。
实施例18
分别配制浓度为0.00125mol/L，0.0025mol/L，0.005mol/L，0.01mol/L，0.02mol/L，0.04mol/L，0.08mol/L的硝酸铜溶液，并用原子吸收光谱仪测定Cu2+的准确浓度，作为Cu2+初始浓度，记为Ci(mg/mL)。
依次量取25mL上述不同浓度的硝酸铜溶液，并分别装入单独的离心管中，然后每个离心管中加入25mg L-CNPs并使之混合均匀。
用5mol/L的氢氧化钠溶液和硝酸溶液调节混合物的PH值为4.6，加入的氢氧化钠溶液和硝酸溶液体积使用量筒计量，加入前后的体积差即为加入量。加入液体的总体积记为Va(mL)。
将盛有混合物的离心管置于恒温震荡床内，保持25℃恒温震荡24h，震荡速率为每分钟震荡150次。
震荡结束后对混合物进行离心(3000r/min)，并使用220nm的尼龙滤头对上清液进行过滤，使用原子吸收光谱仪测定滤液的Cu2+的浓度，作为吸附后的平衡浓度，记为Ce(mg/L)。
每个初始浓度下，当L-CNPs对Cu2+的吸附达到平衡后的吸附量Qe(mg/g)按照以下公式计算：Qe＝1000(25Ci-Ce(25+Va))/25，吸附效果如表10所示。
表10 实施例18中L-CNPs对Cu2+的吸附效果数据
初始浓度mg/L 平衡浓度mg/L 吸附量mg/g
5201.6 4585.6 472.8
2612.8 2372.8 160.4
1346.4 1173.6 153.2
627.4 483.4 135.8
306.6 172.4 133.0
153.0 24.4 128.6
由表11可知，本发明提供的类石墨微晶碳纳米材料对溶液中的铜离子也具有很高 的吸附量。大大高于活性炭等多孔炭材料的吸附量，它们通常只有几十mg/g；相当或稍优于氧化石墨烯等对铜离子的吸附量。
实施例19将L-CNPs冷冻干燥得到的碳纳米材料固体呈现出片状，该片状的宽度尺寸可以达到几十微米以上，但其厚度则只有100纳米左右，扫描电镜分析结果如图13所示，表明这些分散在水溶液的类石墨微晶碳纳米材料，在失去水的过程中具有自助装成纳米薄膜的趋势，具有制作碳纳米薄膜的应用潜力。
对比例1
将硝酸与高氯酸按照物质的量之比为1：1的比例混合，将酸A溶液与酸B溶液按照体积比1:1.1混合配制氧化剂溶液，其中硝酸溶液的质量浓度为65％，高氯酸溶液的质量浓度为70％。
将4.00g的60～80目的椰壳活性炭与100mL的氧化剂溶液混合，采用油浴的方式将混合液加热至100℃，搅拌反应30min后停止加热；以下的操作与实施例2完全相同。
从4.00g椰壳炭得到CMP3.865g,L-CNPs为0.003g,S-CNPs为0.000g。对比实施例2和对比例1可以看出，油浴的加热方式几乎不能制备得到L-CNPs，不能解离类石墨微晶质炭制备得到本发明所述的类石墨微晶碳纳米材料。即在油浴加热条件下，这些混合的氧化性溶液不能解离类石墨微晶质炭材料。
以上实施例的说明只是用于帮助理解本发明的方法及其核心思想。应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以对本发明进行若干改进和修饰，这些改进和修饰也落入本发明权利要求的保护范围内。对这些实施例的多种修改对本领域的专业技术人员来说是显而易见的，本文中所定义的一般原理可以在不脱离本发明的精神或范围的情况下在其它实施例中实现。因此，本发明将不会被限制于本文所示的这些实施例，而是要符合与本文所公开的原理和新颖特点相一致的最宽的范围。

Claims (18)

  1. 一种类石墨微晶碳纳米材料，以100份质量计，在化学组成上包括50～60份的碳，30～45份的氧和1～3份的氢；所述类石墨微晶碳纳米材料的结构单元为类石墨微晶；所述类石墨微晶碳纳米材料的粒径为5～10nm；所述类石墨微晶碳纳米材料为非荧光性碳纳米材料。
  2. 根据权利要求1所述的类石墨微晶碳纳米材料，其特征在于，所述类石墨微晶碳纳米材料的厚度≤1.5nm。
  3. 根据权利要求1或2所述的类石墨微晶碳纳米材料，其特征在于，所述类石墨微晶碳纳米材料为极性碳纳米材料。
  4. 根据权利要求3所述的类石墨微晶碳纳米材料，其特征在于，所述类石墨微晶碳纳米材料在酸性水溶液、碱性水溶液和中性水溶液中进行分散。
  5. 根据权利要求3所述的类石墨微晶碳纳米材料，其特征在于，所述类石墨微晶碳纳米材料含有羧基、羰基、羟基和醚基。
  6. 权利要求1～5任一项所述类石墨微晶碳纳米材料的制备方法，包含如下步骤：
    (1)将氧化剂溶液与类石墨微晶质炭原料混合，在微波加热条件下，进行氧化，得到氧化料液；所述氧化剂溶液包括第一酸和第二酸的混合溶液；所述第一酸为硝酸，所述第二酸为高氯酸或硫酸；
    (2)调节所述步骤(1)得到的氧化料液的pH值至3～8；得到预过滤体系；
    (3)将所述步骤(2)得到的预过滤体系进行超滤，得到悬浮液和滤出液；
    (4)将所述步骤(3)得到的悬浮液进行分离，得到细密悬浮液；
    (5)将所述步骤(4)得到的细密悬浮液进行水分的去除，得到类石墨微晶碳纳米材料。
  7. 根据权利要求6所述的制备方法，其特征在于，所述步骤(1)中类石墨微晶质炭原料的质量和氧化剂溶液的体积比为1g：(20～50)mL；
    所述氧化剂溶液中第一酸和第二酸的摩尔比为(0.5～2)：1；
    所述氧化剂溶液由第一酸溶液和第二酸溶液混合得到，所述第一酸溶液的质量浓度为65～68％，所述第二酸溶液的质量浓度为70～72％；所述第一酸溶液和第二酸溶液的体积比为1：(0.5～2.5)。
  8. 根据权利要求6所述的制备方法，其特征在于，所述步骤(1)中微波加热的功率为500～1000W。
  9. 根据权利要求6所述的制备方法，其特征在于，所述步骤(1)中微波加热的温度为75～110℃；所述微波加热的时间为10～150min。
  10. 根据权利要求6所述的制备方法，其特征在于，所述步骤(1)中类石墨微晶质炭原料包括木炭、竹炭、果壳炭、木质活性炭、果壳活性炭、竹活性炭和煤质活性炭中的一种或多种。
  11. 根据权利要求6所述的制备方法，其特征在于，所述步骤(3)中超滤的次数以超滤得到的滤出液的电导率为准，当所述超滤得到的滤出液的电导率达到20us/cm以下时，超滤完成。
  12. 根据权利要求6或11所述的制备方法，其特征在于，所述步骤(3)中超滤用超滤膜的截留分子量为1000Da。
  13. 根据权利要求6或11所述的制备方法，其特征在于，所述步骤(3)的超滤后还得到滤出液；还包括对所述滤出液依次进行浓缩、透析和干燥，得到荧光性碳纳米颗粒；所述荧光性碳纳米颗粒的粒径为1～3nm。
  14. 根据权利要求6所述的制备方法，其特征在于，所述步骤(4)中分离为离心分离；所述离心分离的次数至少为3次，每次离心分离的时间为10min；每次离心分离的转速独立地在4000～8000rpm。
  15. 根据权利要求6或14所述的制备方法，其特征在于，所述步骤(4)的分离后还得到微米级碳颗粒。
  16. 根据权利要求6所述的制备方法，其特征在于，所述步骤(5)中的水分的去除为依次进行浓缩和干燥。
  17. 权利要求1～5任一项所述类石墨微晶碳纳米材料或权利要求6～16任意一项所述制备方法制备的类石墨微晶碳纳米材料作为金属离子吸附剂的应用。
  18. 权利要求1～5任一项所述类石墨微晶碳纳米材料或权利要求6～16任意一项所述制备方法制备的类石墨微晶碳纳米材料在制备碳纳米薄膜中的应用。
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