CN114408906B - 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 is thatRelates to the technical field of new materials, in particular to a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene. Comprising the following steps: 1) Selecting massive natural coal-based graphite and an inert electrode as an anode and a cathode respectively, selecting a fluorine-containing inorganic salt solution as an electrolyte, connecting the two electrodes with a working power supply, and performing electrochemical stripping treatment to obtain a stripped product; 2) Carrying out ultrasonic treatment on the stripped product, taking a suspension of the stripped product, and carrying out solid-liquid separation and drying treatment to obtain partially purified fluorinated graphene oxide powder; 3) Fluorinated graphene oxide powder and NH 4 F, mixing the solutions, and performing 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, water washing and drying treatment to obtain the purified fluorinated graphene. According to the method, the fluorinated graphene can be prepared while the bulk coal-based graphite raw ore is purified, the deashing rate reaches 92.91%, the fluorine content reaches 16.86%, and the product fluorination degree is adjustable.
Description
Technical Field
The invention relates to the technical field of new materials, in particular to a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene.
Background
The coal-based graphite mineral resources in China are scarce, and the reserve of the resources is only about 5280 ten thousand tons. However, graphite resources, particularly coal-based graphite resources, have not been paid much attention for a long time, and have been widely used as coal for sale or applied to low value added products with a low degree of research and development, which causes great waste of coal-based graphite ore resources. Therefore, research on high value-added applications of coal-based graphite resources is urgent.
The purification of the coal-based graphite is the basis for preparing all graphite materials, and is a common problem for restricting the development of the coal-based graphite materials. The coal-based graphite can be widely applied to various fields only after purification, and particularly has high requirements on the purity of the graphite used in the aerospace industry, the nuclear industry and the like, and the purity of the graphite determines the application value of the graphite even up to 99.99 percent. However, the coal-based graphite purification technology in China is relatively backward, and has a great relation with the raw ore property of the coal-based graphite. The impurity mineral part in the coal-based graphite is tightly combined with the graphite in a dip-dyed form or is wrapped in the aggregate, so that the purification difficulty is increased, and the problems of low purification efficiency, such as high energy consumption and high pollution of a high-temperature method, an alkali acid method, a hydrofluoric acid method, a chloridizing roasting method and the like, generally exist in the current industrial purification technology, such as a flotation method.
On the basis of coal-based graphite purification, the coal-based graphite is modified to have higher market prospect and higher economic value. Compared with materials such as graphene, graphene oxide, graphene and the like, the fluorinated graphene has excellent physicochemical properties such as high thermal stability (more than 400 ℃), high dielectric strength (about 10 MV/cm), high C-F bond energy (530 KJ/mol), large band gap width (about 3 eV), strong hydrophobicity, low surface energy and the like due to the existence of fluorine atoms. Currently, many technical means for preparing fluorinated graphene are available, and the preparation methods can be generally divided into two main types, namely a bottom-up method and a top-down method. The method is to prepare the fluorinated graphene by taking graphene or graphene oxide as a raw material, and the raw material graphene or graphene oxide used by the method has high cost, high cost of a fluorinated 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 a certain danger. The top-down method takes graphite fluoride or graphite as a raw material, prepares the graphene fluoride through mechanical stripping or liquid phase stripping and the like, and is more suitable for mass production routes. Compared with graphite fluoride, the method has the advantages that graphite is selected as a raw material to directly prepare the graphite fluoride, and the cost is lower. The related research report of directly preparing the fluorinated graphene by taking graphite as a raw material is less, and the purpose is thatThere are also certain problems before. In 2011, bruna et al (document: synthesis and properties of monolayer graphene oxyfluoride, J.Mater.chem.,2011,21,18730) prepared fluorinated graphene oxide by an electrochemical method using graphite sheets as a raw material and 50% hydrofluoric acid as an electrolyte, wherein the F/O ratio of the product is about 1. However, the method uses hydrofluoric acid with a higher mass fraction than 40% of the hydrofluoric acid sold in the market, and the use of hydrofluoric acid is harmful to the environment and human body. Jeon et al in 2015 (literature: fluorine: edge-Fluorinated Graphene Nanoplatelets as High Performance Electrodes for Dye-Sensitized Solar Cells and Lithium Ion batteries. Adv. Funct. Mater.2015, 25, 1170) selected graphite as a raw material, and a mixed gas of argon/Fluorine was introduced during the mechanical ball milling process to prepare fluorinated graphene. However, the fluorine gas is introduced under the condition of high-speed ball milling, so that the serious safety problem exists, and the fluorine content of the fluorinated graphene obtained by the method is only 3%. In 2018, zhou et al (document: electrochemically Scalable Production of Fluorine-Modified Graphene for Flexible and High-Energy Ionogel-Based microcapacifiers J Am Chem Soc,2018,140 (26)), selected graphite as the anode and a neutral fluorine-containing inorganic salt NaBF 4 、NH 4 BF 4 Or KPF 6 And (3) preparing the fluorinated graphene by using the electrolyte. However, the fluorine content obtained by the method is low, which is only about 3%.
In summary, various existing technical means severely restrict the purification of coal-based graphite and the preparation of fluorinated graphene, so it is urgent to develop an environment-friendly technology for purifying coal-based graphite and a technology for preparing fluorinated graphene with safety, low cost and adjustable fluorine doping amount.
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 environmental pollution caused by strong acid, strong alkali and the like, and can reduce the energy consumption; the ash removal rate of coal-based graphite purification can reach 92.91%, fluorine-doped fluorinated graphene is prepared while coal-based graphite is purified, the fluorine content can reach 16.86%, and the degree of fluorination is adjustable.
In order to achieve 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 massive natural coal-based graphite and an inert electrode as an anode and a cathode respectively, selecting a fluorine-containing inorganic salt solution as an electrolyte, connecting the two electrodes with a working power supply, and performing 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 a suspension liquid of the stripping product to obtain partially purified fluorinated graphene oxide powder;
3) Mixing the fluorinated graphene oxide powder obtained in the step 2) with NH 4 F, mixing the solutions, and performing hydrothermal treatment to obtain a product after the hydrothermal treatment;
4) And 3) naturally cooling the product obtained after the hydrothermal treatment in the step 3), and then carrying out solid-liquid separation, water 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 invention, after electrochemical stripping treatment is carried out on bulk natural coal-based graphite raw ores, a partially purified fluorinated graphene oxide intermediate product with a small amount of fluorine doping can be obtained, the de-ashing rate of the 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 fluorine doping amount can be further improved, the ash removal rate can reach 92.91%, the fluorine content can reach 16.86%, and the oxygen content is obviously 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 a certain influence on the stripping speed; when the concentration is lower than 0.5M, the peeling rate is very slow; on the one hand, when the concentration is higher than 1.5M, the stripping rate is higher, so that the number of layers of stripping products is larger, the nano graphite sheets are mainly used, the content of fewer layers of graphene is smaller, on the other hand, the content of oxygen-containing functional groups in the stripped graphite sheets is lower, and although the fluorine content is increased, the adsorbed fluorine is not a C-F covalent bond. Therefore, the concentration of the fluorine-containing inorganic salt solution in the present invention is selected to be 0.5 to 1.5M.
The invention firstly examines the influence of electrolyte solutions with different concentrations, namely fluorine-containing inorganic salt solutions, on the fluorine content and the oxygen-containing functional group content of intermediate product fluorinated graphene oxide in the electrochemical stripping treatment process. The effect of the hydrothermal treatment on the fluorine and oxygen content of the final product of the fluorinated graphene was then examined. As shown in fig. 1 and 2. Generally, during the electrochemical stripping treatment, as the concentration of the electrolyte decreases, the fluorine content in the fluorinated graphene oxide as an intermediate product gradually decreases and the oxygen-containing functional group content gradually increases.
In 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 NH 4 F、NaF、KF、NaBF 4 、NH 4 BF 4 One or more of the solutions, preferably NH 4 F, solution.
In the present invention, a fluorine-containing inorganic salt solution such as NH 4 F、NaF、KF、NaBF 4 、NH 4 BF 4 One or more of the solutions being electrolyte, preferably NH 4 The solution F is electrolyte. With NH 4 And F, taking the solution as electrolyte, and carrying out electrochemical stripping treatment on the bulk coal-based graphite under the condition of 10V voltage. Under the action of electric field force, fluorine ions in the electrolyte can directionally migrate and intercalate between coal-based graphite layers to form C-F bonds mainly comprising semi-ionic bonds. The water in the electrolyte loses electrons to form hydroxyl and oxygen free radicals, and the active free radicals oxidize the edges of the coal-based graphite to generate hydroxyl, epoxy, carboxyl and other functionsAnd (3) energy groups. At the same time, with the generation of gases such as oxygen, the coal-based graphite expands further, and finally the fluorinated graphene oxide is obtained by stripping. In addition, under the action of an electric field force, graphite grains expand, and impurity minerals wrapped in the graphite aggregate are exposed and separated from the graphite grains, so that the purity of the coal-based graphite is improved. The fluorine content in the product fluorinated graphene oxide decreases as the concentration of the electrolyte decreases, mainly due to the decrease in the number of fluoride ions intercalated between the layers of the coal-based graphite as the concentration of fluoride ions in the electrolyte decreases, resulting in a decrease in the number of C-F bonds. In addition, the content of oxygen-containing functional groups in the intermediate product fluorinated graphene oxide is obviously increased, mainly because the content of water in the electrolyte is increased along with the reduction of the concentration of the electrolyte, hydroxyl groups and oxygen free radicals generated by water decomposition are increased, and the oxidation effect on the edges of the coal-based graphite is enhanced. At 10V operating voltage, as the electrolyte concentration decreases, the product de-ashing rate increases, mainly due to the decrease in electrochemical stripping rate after the electrolyte concentration decreases. Compared with the method that part of coal-based graphite is peeled off under the condition of insufficient expansion under the condition of high electrolyte concentration, the electrochemical peeling can fully expose impurity minerals wrapped in a graphite aggregate and separate the impurity minerals from graphite grains under the condition of low electrolyte concentration.
Further, in step 3), the fluorinated graphene oxide powder is mixed with NH 4 The solid-liquid ratio of the F solution is 0.2-2%.
Further, the NH 4 The concentration of the F solution is 0.2 to 2M, preferably 1 to 2M.
In the invention, NH is in the hydrothermal treatment process 4 The concentration of the F solution has a certain effect on the ash content of the product, since ammonium fluoride can generate hydrofluoric acid during the hydrothermal treatment, which can dissolve impurity minerals. If NH 4 Too low a concentration of F solution can reduce the product deashing rate.
In step 3), the hydrothermal treatment is carried out at the temperature of 120-180 ℃ for 8-36 h. Preferably, the hydrothermal treatment is carried out at a temperature of 140-160 ℃ for 20-24 hours.
In the invention, bulk natural coal-based graphite is selected as a raw material, and after electrochemical stripping treatment, the raw material is subjected to ultrasonic treatment, solid-liquid separation and drying treatment and then is subjected to hydrothermal treatment, wherein NH is used in the hydrothermal treatment process 4 The F solution is 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 portion of the oxygen-containing functional groups in the fluorinated graphene oxide will be reduced and a portion of the oxygen-containing functional groups will be replaced with fluorine atoms to form C-F covalent bonds. In addition, in the hydrothermal treatment process, siO is used as 2 、Al 2 O 3 The impurity minerals mainly including CaO and MgO are further removed, so that the oxygen content in the product is significantly reduced and the fluorine content is increased.
Further, in the step 2), the power of the ultrasonic treatment is 300-600W, and the treatment time is 10-60 min.
Further, in the step 4), the natural cooling is to naturally cool to 25-30 ℃; in the step 2) and the step 4), the temperature of the drying treatment is 50-80 ℃.
Compared with the prior art, the invention has the following advantages:
the invention provides a method for purifying bulk coal-based raw graphite ores and simultaneously preparing fluorinated graphene, wherein the deashing rate can reach 92.91%, the fluorine content can reach 16.86%, and the fluorination degree can be adjusted. According to the invention, bulk coal-based raw graphite ore is selected as a raw material, so that crushing and ore grinding treatment of graphite blocks are avoided, and compared with other purification processes, the energy consumption is greatly reduced. By adjusting the concentration of the electrolyte in the electrochemical treatment process, the controllable adjustment of the fluorine content in the final fluorinated graphene product can be realized. In addition, the method does not need special instruments or gas, is safe and simple to operate and low in cost, and is expected to realize large-scale production.
Drawings
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate the invention and together with the embodiments of the invention, serve to explain the invention. In the drawings:
FIG. 1 shows the law of the change of the fluorine content and the oxygen-containing functional group content in the intermediate product fluorinated graphene oxide according to the change of the concentration of an electrolyte;
FIG. 2 shows the variation law of fluorine content and oxygen content in final product fluorinated graphene after hydrothermal treatment of different intermediate products;
FIG. 3 is XPS spectra of samples after electrochemical and hydrothermal treatments in example 1;
FIG. 4 is the ash content of the samples after electrochemical treatment and after hydrothermal treatment in example 2;
FIG. 5 is an SEM image of the fluorinated graphene product of example 3;
FIG. 6 is a Raman spectrum of the samples after electrochemical treatment and after hydrothermal treatment in example 4.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and fully with reference to the accompanying drawings, in which it is evident that the embodiments described are only some, but not all embodiments of the invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the 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-based graphite and foil electrode are respectively used as anode and cathode, and 0.5M NH is selected 4 F, using the solution as electrolyte, connecting two electrodes with a working power supply by using copper wires, and performing electrochemical stripping treatment under the condition of 10V voltage for 45min to obtain a stripping product;
(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 suspension, carrying out solid-liquid separation in a suction filtration mode, and drying at the temperature of 50 ℃ to obtain fluorinated graphene oxide powder;
(3) 0.1g of fluorinated graphene oxide powder was taken with 50mL of 1MNH 4 F, blending the solution, adding the mixture into a reaction kettle, and performing hydrothermal treatment, wherein the hydrothermal treatment is performed at the temperature of 140 ℃ for 24 hours to obtain a product after the hydrothermal treatment;
(4) Naturally cooling the product after the hydrothermal treatment to 25 ℃, and then carrying out suction filtration, water washing and drying at 50 ℃ to obtain the fluorinated graphene powder.
XPS profiles of samples after electrochemical treatment and after hydrothermal treatment are shown in FIG. 3.
Example 2
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-based graphite and the titanium alloy electrode are respectively used as an anode and a cathode, and 1M NH is selected 4 And F, using the solution as electrolyte, connecting two electrodes with a working power supply by using copper wires, and performing electrochemical stripping treatment under the condition of 10V voltage for 10min to obtain a stripping product.
(2) Carrying out ultrasonic treatment on the stripping product obtained in the step (1) for 10min under 600W power, standing for 30min, taking suspension, carrying out solid-liquid separation in a suction filtration mode, and drying at 80 ℃ to obtain fluorinated graphene oxide powder;
(3) Taking 1g of fluorinated graphene oxide powder and 50mL of 1MNH 4 F, blending the solution, adding the mixture into a reaction kettle, and performing hydrothermal treatment, wherein the hydrothermal treatment is performed at the temperature of 140 ℃ for 24 hours to obtain a product after the hydrothermal treatment;
(4) Naturally cooling the product after the hydrothermal treatment to 30 ℃, and then carrying out suction filtration, water washing and drying at 80 ℃ to obtain the fluorinated graphene powder.
The ash content of the samples after electrochemical treatment and after 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) The block-shaped natural coal-based graphite and the titanium alloy electrode are respectively used as an anode and a cathode, and 1.5M NH is selected 4 F, using the solution as electrolyte, connecting two electrodes with a working power supply by using copper wires, and performing electrochemical stripping treatment under the condition of 10V voltage for 60min to obtain a stripping product;
(2) Carrying out ultrasonic treatment on the stripping product obtained in the step (1) for 20min under 400W power, centrifuging for 5min under the condition of 1000rpm/min to obtain 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) 0.5g of fluorinated graphene oxide powder was taken with 50mL of 2MNH 4 F, blending the solution, adding the mixture into a reaction kettle, and performing hydrothermal treatment, wherein the hydrothermal treatment is performed at the temperature of 140 ℃ for 20 hours to obtain a product after the hydrothermal treatment;
(4) Naturally cooling the product after the hydrothermal treatment to 30 ℃, and carrying out suction filtration, water washing and drying at 50 ℃ to obtain the fluorinated graphene powder.
SEM images of the fluorinated graphene products are shown in fig. 5.
Example 4
The present example provides a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene, wherein the preparation method is the same as that of example 1 except that the hydrothermal treatment in step (3) is performed at 160 ℃ and the reaction time is 8 hours. The Raman spectra of the samples after electrochemical treatment and after hydrothermal treatment are shown in fig. 6, which shows that the structural defects of the products are obviously reduced and the oxygen-containing functional groups are partially removed after the hydrothermal treatment.
Example 5
The present example provides a method for purifying coal-based graphite and simultaneously preparing fluorinated graphene, wherein the preparation method is the same as that of example 1 except that the hydrothermal treatment in step (3) is performed at a temperature of 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 massive natural coal-based graphite and foil electrodes 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 performing 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 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) 0.1g of fluorinated graphene oxide powder was taken with 50mL of 2MNH 4 F, blending the solution, adding the mixture into a reaction kettle, and performing hydrothermal treatment, wherein the hydrothermal treatment is performed at 180 ℃ for 30 hours to obtain a product after the hydrothermal treatment;
(4) Naturally cooling the product after the hydrothermal treatment to 28 ℃, and carrying out suction filtration, water 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 bulk natural coal-based graphite and foil electrodes as an anode and a cathode respectively, selecting 1.2M KF solution as electrolyte, connecting the two electrodes with a working power supply by using copper wires, and performing 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 20min under the power of 500W, standing for 10min, taking suspension, carrying out solid-liquid separation in a suction filtration mode, and drying at 58 ℃ to obtain fluorinated graphene oxide powder;
(3) 0.1g of fluorinated graphene oxide powder was taken with 50mL of 0.2MNH 4 F, blending the solution, adding the mixture into a reaction kettle, and performing hydrothermal treatment, wherein the hydrothermal treatment is performed at the temperature of 150 ℃ for 22 hours to obtain a product after the hydrothermal treatment;
(4) Naturally cooling the product after the hydrothermal treatment to 26 ℃, and carrying out suction filtration, water 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 block-shaped natural coal-based graphite and foil electrode are respectively used as anode and cathode, and 0.8M NaBF is selected 4 The solution is used as electrolyte, two electrodes are connected with a working power supply by using copper wires, electrochemical stripping treatment is carried out under the condition of 10V voltage, and the treatment time is 30min, so that a stripping product is obtained;
(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 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) 0.1g of fluorinated graphene oxide powder was taken with 50mL of 1MNH 4 F, blending the solution, adding the mixture into a reaction kettle, and performing hydrothermal treatment, wherein the hydrothermal treatment is performed at 180 ℃ for 30 hours to obtain a product after the hydrothermal treatment;
(4) Naturally cooling the product after the hydrothermal treatment to 28 ℃, and carrying out suction filtration, water 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-based graphite and foil electrode are respectively used as anode and cathode, and 0.8M NH is selected 4 BF 4 The solution is used as electrolyte, two electrodes are connected with a working power supply by using copper wires, electrochemical stripping treatment is carried out under the condition of 10V voltage, and the treatment time is 30min, so that a stripping product is obtained;
(2) Carrying out ultrasonic treatment on the stripping product obtained in the step (1) for 25min under 480W power, standing for 10min, taking suspension, carrying out solid-liquid separation in a suction filtration mode, and drying at 60 ℃ to obtain fluorinated graphene oxide powder;
(3) 0.1g of fluorinated graphene oxide powder was taken with 50mL of 1MNH 4 F, blending the solution, and adding the mixture into a reaction kettleThe hydrothermal treatment is carried out at 180 ℃ for 30 hours to obtain a product after the hydrothermal treatment;
(4) Naturally cooling the product after the hydrothermal treatment to 28 ℃, and carrying out suction filtration, water washing and drying at 60 ℃ to obtain the fluorinated graphene powder.
Comparative example 1
The comparative example uses natural coal-based graphite powder as a raw material, and carries out hydrothermal treatment directly on the raw material, and the specific steps are as follows:
(1) 0.1g of coal-based graphite powder and 50mL of 1MNH were taken 4 F, blending the solution, adding the mixture into a reaction kettle, and performing hydrothermal treatment, wherein the hydrothermal treatment conditions are as in example 1, and the concrete steps are as follows: the hydrothermal treatment is carried out at the temperature of 140 ℃ for 24 hours to obtain a product after the hydrothermal treatment;
(2) Naturally cooling the product after the hydrothermal treatment to 25 ℃, and then carrying out suction filtration, water washing and drying at 50 ℃ to obtain the fluorinated graphene powder.
Comparative example 2
The comparative example uses natural coal-based graphite powder as a raw material, and carries out hydrothermal treatment directly on the raw material, specifically:
(1) 1g of coal-based graphite powder was mixed with 50mL of 1.5MNH 4 F, blending the solution, adding the mixture into a reaction kettle, and performing hydrothermal treatment under the same conditions as in example 2, wherein the specific conditions are as follows: the hydrothermal treatment is carried out at the temperature of 140 ℃ for 24 hours to obtain a product after the hydrothermal treatment;
(2) Naturally cooling the product after the hydrothermal treatment to 30 ℃, and then carrying out suction filtration, water washing and drying at 80 ℃ to obtain the fluorinated graphene powder.
Comparative example 3
The comparative example uses bulk natural coal-based graphite as a raw material, and only carries out electrochemical treatment, and the electrochemical treatment conditions are the same as those in example 1, specifically:
(1) The block-shaped natural coal-based graphite and foil electrode are respectively used as anode and cathode, and 0.5M NH is selected 4 F, using the solution as electrolyte, connecting two electrodes with a working power supply by using copper wires, and performing electrochemical stripping under the condition of 10V voltageTreating for 45min to obtain a stripping product;
(2) And (3) carrying out ultrasonic treatment on the stripping product obtained in the step (1) for 30min under the power of 300W, standing for 10min, taking suspension, carrying out solid-liquid separation in a suction filtration mode, and drying at the temperature of 50 ℃ to obtain the fluorinated graphene powder.
Comparative example 4
The comparative example uses bulk natural coal-based graphite as a raw material, and only carries out electrochemical treatment, and the electrochemical treatment conditions are the same as those in example 3, specifically:
(1) The block-shaped natural coal-based graphite and the titanium alloy electrode are respectively used as an anode and a cathode, and 1.5M NH is selected 4 F, using the solution as electrolyte, connecting two electrodes with a working power supply by using copper wires, and performing electrochemical stripping treatment under the condition of 10V voltage for 60min to obtain a stripping product;
(2) And (3) carrying out ultrasonic treatment on the stripping product obtained in the step (1) for 20min under 400W power, centrifuging for 5min under the condition of 1000rpm/min to obtain suspension, carrying out solid-liquid separation by a suction filtration mode, and drying at the temperature of 60 ℃ to obtain the 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 and comparative examples of the present invention. Wherein the ash removal rate is determined by thermogravimetric method 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(s) | 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 higher deashing rate, and the purification of the coal-based graphite can be realized by adopting the method. The fluorine content in the product is high, the oxygen content is low, and the fluorinated graphene can be prepared by adopting the method.
Test example 2
The test example examines the influence of the concentration of the electrolyte on the fluorine content and the oxygen-containing functional group content in the intermediate product fluorinated graphene oxide and the influence on the fluorine content and the oxygen content in the final product fluorinated graphene in the electrochemical stripping treatment process.
The test method comprises the following steps: referring to example 1, the electrolyte NH was variously changed 4 The concentration of F solution was the same as in example 1. The effect of different concentrations of electrolyte on the fluorine content and the oxygen-containing functional group content in the intermediate product fluorinated graphene oxide and the effect of the fluorine content and the oxygen content in the final product fluorinated graphene oxide were examined, wherein the fluorine content, the oxygen-containing functional group content and the oxygen content were 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 of the 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, as the concentration of the electrolyte decreases, the content of oxygen-containing functional groups in the intermediate fluorinated graphene oxide increases, so that the fluorocarbon bonds of the final fluorinated graphene product after hydrothermal treatment also increase, and the fluorine content of the product gradually increases.
Finally, it should be noted that: the foregoing description is only a preferred embodiment of the present invention, and the present invention is not limited thereto, but it is to be understood that modifications and equivalents of some of the technical features described in the foregoing embodiments may be made by those skilled in the art, although the present invention has been described in detail with reference to the foregoing embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (9)
1. The method for purifying coal-based graphite and simultaneously preparing fluorinated graphene is characterized by comprising the following steps of:
1) Selecting massive natural coal-based graphite and an inert electrode as an anode and a cathode respectively, selecting a fluorine-containing inorganic salt solution as an electrolyte, connecting the two electrodes with a working power supply, and performing 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 a suspension liquid of the stripping product to obtain partially purified fluorinated graphene oxide powder;
3) Mixing the fluorinated graphene oxide powder obtained in the step 2) with NH 4 F, mixing the solutions, and performing hydrothermal treatment to obtain a product after the hydrothermal treatment;
4) Naturally cooling the product obtained in the step 3), and then carrying out solid-liquid separation, water washing and drying treatment to obtain purified fluorinated graphene;
in the step 1), the concentration of the fluorine-containing inorganic salt solution is 0.5-1.5M, and the fluorine-containing inorganic salt solution is NH 4 F, solution.
2. The method according to claim 1, wherein in step 1), the electrochemical stripping treatment is performed under a voltage of 10V for a period of 10 to 60 minutes.
3. The method according to claim 1 or 2, wherein in step 3) the fluorinated graphene oxide powder is mixed with NH 4 The solid-liquid ratio of the F solution is 0.2-2%.
4. A method according to claim 3, wherein said NH is 4 The concentration of the F solution is 0.2-2M.
5. The method of claim 4, wherein said NH is 4 The concentration of the F solution is 1-2M.
6. The method according to claim 4 or 5, wherein in step 3), the hydrothermal treatment is performed at a temperature of 120 to 180 ℃ for a reaction time of 8 to 36 hours.
7. The method according to claim 6, wherein the hydrothermal treatment is carried out at a temperature of 140 to 160 ℃ for a reaction time of 20 to 24 hours.
8. The method according to any one of claims 1 to 7, wherein in step 2), the power of the ultrasonic treatment is 300 to 600W and the treatment time is 10 to 60min.
9. The method of claim 8, wherein the step of determining the position of the first electrode is performed,
in the step 4), the natural cooling is carried out to 25-30 ℃;
in the step 2) and the step 4), the temperature of the drying treatment is 50-80 ℃.
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