CN114408906A - Method for purifying coal-based graphite and simultaneously preparing fluorinated graphene - Google Patents
Method for purifying coal-based graphite and simultaneously preparing fluorinated graphene Download PDFInfo
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Abstract
The invention relates to the technical field of new materials, in particular to a method for purifying coal-series graphite and simultaneously preparing fluorinated graphene. The method comprises the following steps: 1) selecting blocky natural coal-based graphite and an inert electrode as an anode and a cathode respectively, selecting a fluorine-containing inorganic salt solution as electrolyte, connecting the two electrodes with a working power supply, and carrying out electrochemical stripping treatment to obtain a stripped product; 2) carrying out ultrasonic treatment on the stripped product, and carrying out solid-liquid separation and drying treatment on the suspension to obtain partially purified fluorinated graphene oxide powder; 3) mixing fluorinated graphene oxide powder and NH4Mixing the solutions F, and carrying out hydrothermal treatment to obtain a product after the hydrothermal treatment; 4) and naturally cooling the product after the hydrothermal treatment, and then carrying out solid-liquid separation, washing and drying treatment to obtain the purified fluorinated graphene. The invention can be used for matching the massive coal-series graphiteThe raw ore is purified and the fluorinated graphene is prepared, the ash removal rate reaches 92.91%, the fluorine content reaches 16.86%, and the fluorination degree of the product is adjustable.
Description
Technical Field
The invention relates to the technical field of new materials, in particular to a method for purifying coal-series graphite and simultaneously preparing fluorinated graphene.
Background
The coal-series graphite mineral resources in China are scarce, and the resource reserves are found to be only 5280 ten thousand tons. However, for a long time, graphite resources, especially coal-based graphite resources, have not been paid much attention, and the degree of research and development is low, and the graphite resources are generally sold as coal or applied to low-added-value products, which causes great waste of coal-based graphite ore resources. Therefore, research on high-added-value application of the coal-based graphite resource is urgent.
The purification of the coal-based graphite is the basis for preparing all graphite materials and is a common problem which restricts the development of the coal-based graphite materials. The coal-based graphite can be widely applied to various fields only after being purified, and particularly has high requirements on the purity of the used graphite in the aerospace industry, the nuclear industry and the like, even up to 99.99 percent, and the purity of the graphite determines the application value of the graphite. However, the purification technology of coal-based graphite in China is relatively backward, and the purification technology has a great relationship with the properties of raw ores of the coal-based graphite. The impurity mineral part in the coal-series graphite is tightly combined with the graphite in a dip-dyeing state or is wrapped in the aggregate, so that the purification difficulty is increased, and the problems of low purification efficiency of the existing industrialized purification technology such as a flotation method generally exist, such as high energy consumption and high pollution of a high-temperature method, an alkali-acid method, a hydrofluoric acid method, a chlorination roasting method and the like.
On the basis of purifying the coal-based graphite, the coal-based graphite can have higher market prospect and higher economic value only by modifying the coal-based graphite. Compared with materials such as graphene, graphene oxide and graphene, the fluorinated graphene is fluorinated due to the existence of fluorine atomsGraphene has excellent physicochemical properties such as high thermal stability (greater than 400 ℃), high dielectric strength (about 10MV/cm), high C — F bond binding energy (530KJ/mol), large band gap width (about 3eV), strong hydrophobicity, low surface energy, and the like. At present, there are many technical means for preparing fluorinated graphene, and they can be generally classified into two categories, namely "bottom-up" method and "top-down" method. The bottom-up method is to prepare fluorinated graphene by taking graphene or graphene oxide as a raw material, and the method has the advantages of high cost of the raw material graphene or graphene oxide, high cost of a fluorination reagent, difficult obtainment and high toxicity. In addition, if the graphene is prepared by using gas-phase direct fluorination, the process has high requirements on reaction equipment and has certain dangerousness. The 'top-down' method is to prepare the fluorinated graphene by taking the fluorinated graphite or graphite as a raw material through mechanical stripping or liquid phase stripping and the like, and is more suitable for batch production routes. Compared with graphite fluoride, graphite is selected as a raw material to directly prepare the fluorinated graphene, so that the cost is lower. Related research reports for directly preparing fluorinated graphene by taking graphite as a raw material are few, and certain problems exist at present. In 2011, Bruna et al (documents: Synthesis and Properties of monolayer graphene oxyfluoride, J.Mater.chem.,2011,21,18730) prepared fluorinated graphene oxide by an electrochemical method by using graphite sheets as raw materials and 50% hydrofluoric acid as an electrolyte, and the F/O ratio of the product is about 1. However, the hydrofluoric acid used in this method is high in mass fraction, not 40% of the commercially available hydrofluoric acid, and moreover, the use of hydrofluoric acid is harmful to both the environment and the human body. Jeon et al (document: Fluorine: Edge-Fluorinated Graphene nanoplates as High Performance Electrodes for Dye-Sensitized Solar Cells and Lithium Ion batteries. adv. function. Mater.2015, 25, 1170) used graphite as a raw material, and mixed gas of argon gas/Fluorine gas was introduced during mechanical ball milling to prepare the Fluorinated Graphene. However, the introduction of fluorine gas under high-speed ball milling conditions has serious safety problems, and the fluorine content of the fluorinated graphene obtained by the method is only 3%. 2018, Zhou et al (literature: electrochemical Scalable Production of Fluorine-Modified Graphene for flexibility and High-Ener)J Am Chem Soc,2018,140(26),8198-4、NH4BF4Or KPF6And (4) preparing the fluorinated graphene as an electrolyte. However, the fluorine content prepared by the method is low and is only about 3%.
In conclusion, the purification of coal-based graphite and the preparation of fluorinated graphene are severely restricted by various conventional technical means, so that the development of an environment-friendly technology for purifying coal-based graphite and a safe, low-cost and fluorine-doping-amount-adjustable technology for preparing fluorinated graphene is urgent.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene. The method avoids the problem of environmental pollution caused by using strong acid, strong alkali and the like, and can reduce energy consumption; the ash removal rate of the coal-based graphite purification can reach 92.91%, the fluorine-doped fluorinated graphene is prepared while the coal-based graphite is purified, the fluorine content can reach 16.86%, and the degree of fluorination can be adjusted.
In order to realize the purpose of the invention, the invention adopts the following technical scheme:
a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene, wherein the method comprises the following steps:
1) selecting blocky natural coal-based graphite and an inert electrode as an anode and a cathode respectively, selecting a fluorine-containing inorganic salt solution as electrolyte, connecting the two electrodes with a working power supply, and carrying out electrochemical stripping treatment to obtain a stripped product;
2) carrying out ultrasonic treatment on the stripping product obtained in the step 1), and carrying out solid-liquid separation and drying treatment on the suspension to obtain partially purified fluorinated graphene oxide powder;
3) mixing the fluorinated graphene oxide powder obtained in the step 2) with NH4Mixing the solutions F, and carrying out hydrothermal treatment to obtain a product after the hydrothermal treatment;
4) naturally cooling the product obtained in the step 3) after the hydrothermal treatment, and then performing solid-liquid separation, washing and drying treatment to obtain the purified fluorinated graphene.
The invention provides a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene. According to the method, after electrochemical stripping treatment is carried out on massive natural coal-series graphite raw ores, a partially purified fluorinated graphene oxide intermediate product with a small amount of fluorine impurities can be obtained, the deliming rate of the intermediate product can reach more than 50%, and the fluorine content can reach more than 5%. After the intermediate product is further subjected to hydrothermal treatment, the purification effect and the fluorine doping amount can be further improved, the deashing rate can reach 92.91%, the fluorine content can reach 16.86%, and the oxygen content is remarkably reduced to below 7.70%, so that the fluorinated graphene is obtained. In addition, the scheme can realize the regulation and control of the fluorine content in the fluorinated graphene sample.
Further, in the step 1), the concentration of the fluorine-containing inorganic salt solution is 0.5-1.5M.
In the invention, the concentration of the fluorine-containing inorganic salt solution has certain influence on the stripping speed; when the concentration is less than 0.5M, the peeling rate is very slow; when the concentration is higher than 1.5M, on one hand, the stripping rate is higher, so that the number of stripped products is larger, the nano graphite sheet is taken as the main part, and the few-layer graphene content is lower, and on the other hand, the stripped graphite sheet has lower oxygen-containing functional group content, and the fluorine content is increased, but the adsorbed fluorine is mainly fluorine, and is not a C-F covalent bond. Therefore, the concentration of the fluorine-containing inorganic salt solution is selected to be 0.5-1.5M.
The invention firstly inspects the influence of electrolyte with different concentrations, namely fluorine-containing inorganic salt solution, on the fluorine content and the oxygen-containing functional group content of the intermediate fluorinated graphene oxide in the electrochemical stripping treatment process. Then, the influence of the hydrothermal treatment on the fluorine content and the oxygen content of the final product fluorinated graphene is examined. As shown in fig. 1 and 2. Generally, during the electrochemical stripping treatment, when the concentration of the electrolyte is reduced, the fluorine content in the intermediate fluorinated graphene oxide is gradually reduced, and the oxygen-containing functional group content is gradually increased.
Further, in the step 1), the electrochemical stripping treatment is performed under the condition of 10V voltage, and the treatment time is 10-60 min.
Further, the fluorine-containing inorganic salt solution is NH4F、NaF、KF、NaBF4、NH4BF4One or more of the solutions, preferably NH4And F, solution.
In the present invention, a fluorine-containing inorganic salt solution such as NH is used4F、NaF、KF、NaBF4、NH4BF4One or more of the solutions is/are electrolyte, preferably NH4The solution F is electrolyte. By NH4And performing electrochemical stripping treatment on the massive coal-based graphite by using the solution F as an electrolyte under the condition of 10V voltage. Under the action of electric field force, fluorine ions in the electrolyte can be directionally transferred and inserted into the coal-based graphite layers to form C-F bonds mainly comprising semi-ionic bonds. Water in the electrolyte loses electrons to form hydroxyl and oxygen radicals, and the active radicals oxidize the edge of the coal-based graphite to generate functional groups such as hydroxyl, epoxy, carboxyl and the like. Meanwhile, with the generation of gases such as oxygen, the coal-based graphite further expands, and finally the fluorinated graphene oxide is prepared by stripping. In addition, under the action of electric field force, the graphite crystal grains expand, so that impurity minerals wrapped in the graphite aggregate are exposed and separated from the graphite crystal grains, and the purity of the coal-based graphite is improved. The fluorine content in the fluorinated graphene oxide product is reduced along with the reduction of the concentration of the electrolyte, and the fluorine ions inserted into the coal-based graphite layers are reduced along with the reduction of the concentration of the fluorine ions in the electrolyte, so that the formed C-F bonds are reduced. In addition, the content of oxygen-containing functional groups in the intermediate fluorinated graphene oxide is remarkably increased, mainly because the water content in the electrolyte is increased along with the decrease of the concentration of the electrolyte, and the hydroxyl and oxygen free radicals generated by water decomposition are increased, so that the oxidation effect on the edge of the coal-based graphite is enhanced. At 10V operating voltage, as the electrolyte concentration decreases, the product deliming rate increases, mainly due to the electrochemical stripping rate decreasing after the electrolyte concentration decreases. Compared with partial coal-based graphite under high electrolyte concentrationThe graphite particles are peeled off without sufficient expansion, and under the condition of low electrolyte concentration, the impurity minerals wrapped in the graphite aggregate can be fully exposed by electrochemical peeling and separated from the graphite grains.
Further, in step 3), fluorinating graphene oxide powder and NH4The solid-liquid ratio of the F solution is 0.2-2%.
Further, said NH4The concentration of the F solution is 0.2-2M, preferably 1-2M.
In the present invention, NH is generated during the hydrothermal treatment4The concentration of the F solution has an effect on the ash content of the product, since ammonium fluoride can generate hydrofluoric acid during hydrothermal treatment, which can dissolve impurity minerals. If NH4The concentration of the F solution is too low, so that the product deashing rate is reduced.
Further, in the step 3), the hydrothermal treatment is carried out at 120-180 ℃, and the reaction time is 8-36 h. Preferably, the hydrothermal treatment is carried out at the temperature of 140-160 ℃, and the reaction time is 20-24 h.
According to the invention, blocky natural coal-series graphite is selected as a raw material, is subjected to electrochemical stripping treatment, is subjected to ultrasonic treatment, solid-liquid separation and drying treatment, and is subjected to hydrothermal treatment, wherein NH is used in the hydrothermal treatment process4The solution F is used as a medium, the concentration of the solution is 0.2-2M, the preferable concentration is 1-2M, the reaction temperature is 120-180 ℃, the preferable reaction temperature is 140-160 ℃, and the reaction time is 8-36 h, and the preferable reaction time is 20-24 h. After hydrothermal treatment, the fluorine content and the deashing rate in the product are obviously improved, and the oxygen content is obviously reduced. This is because under hydrothermal conditions, a part of oxygen-containing functional groups in the fluorinated graphene oxide will be reduced, and a part of the oxygen-containing functional groups will be substituted by fluorine atoms to form a C — F covalent bond. In addition, during the hydrothermal treatment, SiO is used2、Al2O3Since impurity minerals such as CaO and MgO are further removed, the oxygen content in the product is significantly reduced and the fluorine content is increased.
Further, in the step 2), the power of ultrasonic treatment is 300-600W, and the treatment time is 10-60 min.
Further, in the step 4), the natural cooling is to be carried out to 25-30 ℃; in the step 2) and the step 4), the drying temperature is 50-80 ℃.
Compared with the prior art, the invention has the following advantages:
the invention provides a method for purifying bulk coal-series graphite raw ore and simultaneously preparing fluorinated graphene, wherein the deashing rate can reach 92.91%, the fluorine content can reach 16.86%, and the degree of fluorination can be adjusted. The invention selects the block coal-series graphite raw ore as the raw material, firstly avoids the crushing and ore grinding treatment of the graphite block, and greatly reduces the energy consumption compared with other purification processes. By adjusting the concentration of the electrolyte in the electrochemical treatment process, the fluorine content in the final fluorinated graphene product can be controllably adjusted. In addition, the method does not need special instruments or gas, is safe and simple to operate, has low cost and is expected to realize large-scale production.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the principles of the invention and not to limit the invention. In the drawings:
FIG. 1 is a graph showing the change law of fluorine content and oxygen-containing functional group content in intermediate fluorinated graphene oxide according to the change of electrolyte concentration;
FIG. 2 is a diagram showing the change rule of fluorine content and oxygen content in the final product fluorinated graphene after different intermediate products are subjected to hydrothermal treatment;
FIG. 3 is an XPS spectrum of samples after electrochemical treatment and after hydrothermal treatment in example 1;
FIG. 4 is the ash content of the samples after electrochemical and hydrothermal treatment in example 2;
FIG. 5 is an SEM image of a fluorinated graphene product of example 3;
fig. 6 is a Raman spectrum of the sample after electrochemical treatment and after hydrothermal treatment in example 4.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without any inventive step based on the embodiments of the present invention, are within the scope of the present invention.
Example 1
The embodiment provides a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene, which comprises the following steps:
(1) the block-shaped natural coal-series graphite and the foil electrode are respectively used as an anode and a cathode, and 0.5M NH is selected4The solution F is used as electrolyte, two electrodes are connected with a working power supply through copper wires, electrochemical stripping treatment is carried out under the condition of 10V voltage, the treatment time is 45min, and a stripping product is obtained;
(2) carrying out ultrasonic treatment on the stripping product obtained in the step (1) for 30min under the power of 300W, standing for 10min, taking the suspension, carrying out solid-liquid separation in a suction filtration mode, and drying at 50 ℃ to obtain fluorinated graphene oxide powder;
(3) taking 0.1g of fluorinated graphene oxide powder and 50mL of 1MNH4Blending the solution F, adding the blended solution F into a reaction kettle for hydrothermal treatment, wherein the hydrothermal treatment is carried out at the temperature of 140 ℃ for 24 hours to obtain a product after the hydrothermal treatment;
(4) and naturally cooling the product after the hydrothermal treatment to 25 ℃, and then performing suction filtration, washing and drying at 50 ℃ to obtain the fluorinated graphene powder.
XPS spectra of the samples after electrochemical and hydrothermal treatment are shown in figure 3.
Example 2
The embodiment provides a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene, which comprises the following steps:
(1) selecting blocky natural coal-series graphite and a titanium alloy electrode as an anode and a cathode respectively, and selecting 1M NH4The solution F is used as electrolyte, two electrodes are connected with a working power supply by using copper wires, and electricity is performed under the condition of 10V voltageAnd (5) carrying out chemical stripping treatment for 10min to obtain a stripped product.
(2) Carrying out ultrasonic treatment on the stripped product obtained in the step (1) for 10min under the power of 600W, standing for 30min, taking the suspension, carrying out solid-liquid separation in a suction filtration mode, and drying at the temperature of 80 ℃ to obtain fluorinated graphene oxide powder;
(3) 1g of fluorinated graphene oxide powder and 50mL of 1MNH are taken4Blending the solution F, adding the blended solution F into a reaction kettle for hydrothermal treatment, wherein the hydrothermal treatment is carried out at the temperature of 140 ℃ for 24 hours to obtain a product after the hydrothermal treatment;
(4) and naturally cooling the product after the hydrothermal treatment to 30 ℃, and then performing suction filtration, washing and drying at 80 ℃ to obtain the fluorinated graphene powder.
The ash content of the samples after electrochemical and hydrothermal treatment is shown in fig. 4.
Example 3
The embodiment provides a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene, which comprises the following steps:
(1) selecting blocky natural coal-series graphite and a titanium alloy electrode as an anode and a cathode respectively, and selecting 1.5M NH4The solution F is used as electrolyte, two electrodes are connected with a working power supply through copper wires, electrochemical stripping treatment is carried out under the condition of 10V voltage, the treatment time is 60min, and stripping products are obtained;
(2) carrying out ultrasonic treatment on the stripping product obtained in the step (1) for 20min under the power of 400W, then centrifuging for 5min under the condition of 1000rpm/min to obtain a suspension, carrying out solid-liquid separation in a suction filtration mode, and drying at the temperature of 60 ℃ to obtain fluorinated graphene oxide powder;
(3) taking 0.5g of fluorinated graphene oxide powder and 50mL of 2MNH4Blending the solution F, adding the blended solution F into a reaction kettle for hydrothermal treatment, wherein the hydrothermal treatment is carried out at the temperature of 140 ℃ for 20 hours to obtain a product after the hydrothermal treatment;
(4) and naturally cooling the product after the hydrothermal treatment to 30 ℃, and then performing suction filtration, washing and drying at 50 ℃ to obtain the fluorinated graphene powder.
The SEM image of the fluorinated graphene product is shown in fig. 5.
Example 4
This example provides a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene, which is the same as example 1 except that the hydrothermal treatment in step (3) is performed at 160 ℃ and the reaction time is 8 hours. Raman spectra of samples after electrochemical treatment and hydrothermal treatment are shown in FIG. 6, which shows that structural defects of the product are remarkably reduced and oxygen-containing functional groups are partially removed through the hydrothermal treatment.
Example 5
This example provides a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene, which is the same as example 1 except that the hydrothermal treatment in step (3) is performed at 120 ℃ and the reaction time is 36 hours.
Example 6
The embodiment provides a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene, which comprises the following steps:
(1) selecting blocky natural coal-based graphite and a foil electrode as an anode and a cathode respectively, selecting 0.8M NaF solution as electrolyte, connecting the two electrodes with a working power supply by using copper wires, and carrying out electrochemical stripping treatment under the condition of 10V voltage for 30min to obtain a stripped product;
(2) carrying out ultrasonic treatment on the stripping product obtained in the step (1) for 60min under the power of 450W, standing for 10min, taking the suspension, carrying out solid-liquid separation in a suction filtration mode, and drying at the temperature of 60 ℃ to obtain fluorinated graphene oxide powder;
(3) taking 0.1g of fluorinated graphene oxide powder and 50mL of 2MNH4Blending the solution F, adding the blended solution F into a reaction kettle for hydrothermal treatment, wherein the hydrothermal treatment is carried out at the temperature of 180 ℃ for 30 hours to obtain a product after the hydrothermal treatment;
(4) and naturally cooling the product after the hydrothermal treatment to 28 ℃, and then performing suction filtration, washing and drying at 60 ℃ to obtain the fluorinated graphene powder.
Example 7
The embodiment provides a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene, which comprises the following steps:
(1) selecting blocky natural coal-based graphite and a foil electrode as an anode and a cathode respectively, selecting a 1.2M KF solution as an electrolyte, connecting the two electrodes with a working power supply by using copper wires, and carrying out electrochemical stripping treatment under the condition of 10V voltage for 30min to obtain a stripping product;
(2) carrying out ultrasonic treatment on the stripped product obtained in the step (1) for 20min under the power of 500W, standing for 10min, taking the suspension, carrying out solid-liquid separation in a suction filtration mode, and drying at the temperature of 58 ℃ to obtain fluorinated graphene oxide powder;
(3) taking 0.1g of fluorinated graphene oxide powder and 50mL of 0.2MNH4Blending the solution F, adding the blended solution F into a reaction kettle for hydrothermal treatment, wherein the hydrothermal treatment is carried out at the temperature of 150 ℃ for 22 hours to obtain a product after the hydrothermal treatment;
(4) and naturally cooling the product after the hydrothermal treatment to 26 ℃, and then performing suction filtration, washing and drying at 58 ℃ to obtain the fluorinated graphene powder.
Example 8
The embodiment provides a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene, which comprises the following steps:
(1) the method selects blocky natural coal-series graphite and a foil electrode as an anode and a cathode respectively, and selects 0.8M NaBF4The solution is used as electrolyte, two electrodes are connected with a working power supply by using copper wires, and electrochemical stripping treatment is carried out under the condition of 10V voltage for 30min to obtain a stripping product;
(2) carrying out ultrasonic treatment on the stripping product obtained in the step (1) for 60min under the power of 450W, standing for 10min, taking the suspension, carrying out solid-liquid separation in a suction filtration mode, and drying at the temperature of 60 ℃ to obtain fluorinated graphene oxide powder;
(3) taking 0.1g of fluorinated graphene oxide powder and 50mL of 1MNH4Blending the solution F, adding the blended solution F into a reaction kettle for hydrothermal treatment, wherein the hydrothermal treatment is carried out at the temperature of 180 ℃ for 30 hours to obtain a product after the hydrothermal treatment;
(4) and naturally cooling the product after the hydrothermal treatment to 28 ℃, and then performing suction filtration, washing and drying at 60 ℃ to obtain the fluorinated graphene powder.
Example 9
The embodiment provides a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene, which comprises the following steps:
(1) the block-shaped natural coal-series graphite and the foil electrode are respectively used as an anode and a cathode, and 0.8M NH is selected4BF4The solution is used as electrolyte, two electrodes are connected with a working power supply by using copper wires, and electrochemical stripping treatment is carried out under the condition of 10V voltage for 30min to obtain a stripping product;
(2) carrying out ultrasonic treatment on the stripping product obtained in the step (1) for 25min under 480W power, standing for 10min, taking the suspension, carrying out solid-liquid separation in a suction filtration mode, and drying at 60 ℃ to obtain fluorinated graphene oxide powder;
(3) taking 0.1g of fluorinated graphene oxide powder and 50mL of 1MNH4Blending the solution F, adding the blended solution F into a reaction kettle for hydrothermal treatment, wherein the hydrothermal treatment is carried out at the temperature of 180 ℃ for 30 hours to obtain a product after the hydrothermal treatment;
(4) and naturally cooling the product after the hydrothermal treatment to 28 ℃, and then performing suction filtration, washing and drying at 60 ℃ to obtain the fluorinated graphene powder.
Comparative example 1
The comparative example uses natural coal-series graphite powder as a raw material, and directly carries out hydrothermal treatment on the raw material, and specifically comprises the following steps:
(1) taking 0.1g of coal-series graphite powder and 50mL of 1MNH4And blending the solution F, adding the blended solution F into a reaction kettle, and carrying out hydrothermal treatment under the same hydrothermal treatment conditions as those in example 1, wherein the hydrothermal treatment conditions are as follows: carrying out hydrothermal treatment at the temperature of 140 ℃ for 24 hours to obtain a product after the hydrothermal treatment;
(2) and naturally cooling the product after the hydrothermal treatment to 25 ℃, and then performing suction filtration, washing and drying at 50 ℃ to obtain the fluorinated graphene powder.
Comparative example 2
The comparative example selects natural coal-series graphite powder as a raw material, and directly carries out hydrothermal treatment on the natural coal-series graphite powder, and specifically comprises the following steps:
(1) 1g of coal-based graphite powder and 50mL of 1.5MNH4And blending the solution F, adding the blended solution F into a reaction kettle, and carrying out hydrothermal treatment under the same hydrothermal treatment conditions as those in example 2, wherein the hydrothermal treatment conditions are as follows: carrying out hydrothermal treatment at the temperature of 140 ℃ for 24 hours to obtain a product after the hydrothermal treatment;
(2) and naturally cooling the product after the hydrothermal treatment to 30 ℃, and then performing suction filtration, washing and drying at 80 ℃ to obtain the fluorinated graphene powder.
Comparative example 3
The comparative example uses blocky natural coal-series graphite as a raw material, only carries out electrochemical treatment, and the conditions of the electrochemical treatment are the same as those of the example 1, and specifically comprises the following steps:
(1) the block-shaped natural coal-series graphite and the foil electrode are respectively used as an anode and a cathode, and 0.5M NH is selected4The solution F is used as electrolyte, two electrodes are connected with a working power supply through copper wires, electrochemical stripping treatment is carried out under the condition of 10V voltage, the treatment time is 45min, and a stripping product is obtained;
(2) and (2) carrying out ultrasonic treatment on the stripping product obtained in the step (1) for 30min under the power of 300W, standing for 10min, taking the suspension, carrying out solid-liquid separation in a suction filtration mode, and drying at 50 ℃ to obtain the fluorinated graphene powder.
Comparative example 4
The comparative example uses blocky natural coal-series graphite as a raw material, only carries out electrochemical treatment, and the conditions of the electrochemical treatment are the same as those of example 3, and specifically comprises the following steps:
(1) selecting blocky natural coal-series graphite and a titanium alloy electrode as an anode and a cathode respectively, and selecting 1.5M NH4The solution F is used as electrolyte, two electrodes are connected with a working power supply through copper wires, electrochemical stripping treatment is carried out under the condition of 10V voltage, the treatment time is 60min, and stripping products are obtained;
(2) and (2) carrying out ultrasonic treatment on the stripping product obtained in the step (1) for 20min under the power of 400W, then centrifuging for 5min under the condition of 1000rpm/min to obtain a suspension, carrying out solid-liquid separation in a suction filtration mode, and drying at the temperature of 60 ℃ to obtain fluorinated graphene powder.
Test example 1
The present test example examined the deashing rate, fluorine content and oxygen content of the final products obtained in the examples of the present invention and the comparative examples. Wherein the deashing rate is determined by thermogravimetry, and the fluorine content and the oxygen content are determined by X-ray photoelectron spectroscopy.
The results are shown in Table 1:
TABLE 1
| Product of | Deashing rate (%) | Fluorine content (%) | Oxygen content (%) |
| Example 1 | 92.91 | 16.86 | 5.40 |
| Example 2 | 83.50 | 12.10 | 6.80 |
| Example 3 | 89.91 | 8.89 | 7.70 |
| Example 4 | 86.19 | 14.77 | 5.80 |
| Example 5 | 86.83 | 15.77 | 5.60 |
| Example 6 | 87.22 | 15.91 | 5.23 |
| Example 7 | 80.17 | 12.89 | 7.49 |
| Example 8 | 87.20 | 16.33 | 5.17 |
| Example 9 | 84.43 | 15.32 | 6.91 |
| Comparative example 1 | 60.21 | 1.71 | 9.72 |
| Comparative example 2 | 73.53 | 1.63 | 10.11 |
| Comparative example 3 | 33.91 | 2.02 | 32.30 |
| Comparative example 4 | 39.80 | 3.52 | 23.70 |
The test results show that the product has high deashing rate, and the method can realize the purification of the coal-series graphite. The fluorine content in the product is high, the oxygen content is low, and the fluorinated graphene can be prepared by the method.
Test example 2
In the test example, the influence of the concentration of the electrolyte on the fluorine content and the oxygen-containing functional group content in the intermediate fluorinated graphene oxide and the influence on the fluorine content and the oxygen content in the final fluorinated graphene oxide in the electrochemical stripping treatment process are examined.
The test method comprises the following steps: reference example 1, with different modification of the electrolyte NH4The concentration of the F solution was the same as that in example 1. And (3) examining the influence of electrolytes with different concentrations on the fluorine content and the oxygen-containing functional group content in the intermediate fluorinated graphene oxide and the fluorine content and the oxygen content in the final fluorinated graphene oxide, wherein the fluorine content, the oxygen-containing functional group content and the oxygen content are determined by X-ray photoelectron spectroscopy.
The test results are shown in fig. 1 and 2.
The results show that: the fluorine content of the final product fluorinated graphene after the hydrothermal treatment can be regulated and controlled by changing the concentration of the electrolyte in the electrochemical stripping treatment process. Generally, in the electrochemical stripping treatment process, as the concentration of the electrolyte is reduced, the content of oxygen-containing functional groups in the intermediate fluorinated graphene oxide increases, so that the carbon-fluorine bonds of the final product fluorinated graphene after the hydrothermal treatment also increase, and the content of fluorine in the product gradually increases.
Finally, it should be noted that: although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that changes may be made in the embodiments and/or equivalents thereof without departing from the spirit and scope of the invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for purifying coal-based graphite and simultaneously preparing fluorinated graphene is characterized by comprising the following steps:
1) selecting blocky natural coal-based graphite and an inert electrode as an anode and a cathode respectively, selecting a fluorine-containing inorganic salt solution as electrolyte, connecting the two electrodes with a working power supply, and carrying out electrochemical stripping treatment to obtain a stripped product;
2) carrying out ultrasonic treatment on the stripping product obtained in the step 1), and carrying out solid-liquid separation and drying treatment on the suspension to obtain partially purified fluorinated graphene oxide powder;
3) mixing the fluorinated graphene oxide powder obtained in the step 2) with NH4Mixing the solutions F, and carrying out hydrothermal treatment to obtain a product after the hydrothermal treatment;
4) naturally cooling the product obtained in the step 3) after the hydrothermal treatment, and then performing solid-liquid separation, washing and drying treatment to obtain the purified fluorinated graphene.
2. The method according to claim 1, wherein the concentration of the fluorine-containing inorganic salt solution in the step 1) is 0.5 to 1.5M.
3. The method according to claim 2, wherein in the step 1), the electrochemical stripping treatment is performed under a voltage of 10V for a treatment time of 10-60 min.
4. The method according to claim 2 or 3, wherein the fluorine-containing inorganic salt solution is NH4F、NaF、KF、NaBF4、NH4BF4One or more of the solutions; preferably NH4And F, solution.
5. The method according to any one of claims 1 to 4, wherein in step 3), the fluorinated graphene oxide powder is mixed with NH4The solid-liquid ratio of the F solution is 0.2-2%.
6. The method of claim 5, wherein said NH is4The concentration of the F solution is 0.2-2M; preferably 1-2M.
7. The method according to claim 5 or 6, wherein in the step 3), the hydrothermal treatment is carried out at a temperature of 120-180 ℃ and a reaction time of 8-36 h.
8. The method according to claim 7, wherein the hydrothermal treatment is carried out at a temperature of 140-160 ℃ for 20-24 hours.
9. The method according to any one of claims 1 to 8, wherein in the step 2), the power of the ultrasonic treatment is 300 to 600W, and the treatment time is 10 to 60 min.
10. The method of claim 9,
in the step 4), naturally cooling to 25-30 ℃;
in the step 2) and the step 4), the drying temperature is 50-80 ℃.
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