Disclosure of Invention
The invention aims to provide a method for preparing a less-lamellar graphene oxide dispersion liquid by a wet milling oxidation method, which is simple to operate, high in preparation efficiency and less in pollutant generation.
In order to achieve the purpose, the invention adopts the technical scheme that:
the method comprises the following steps: adding 10-20 parts by mass of strong acid into a reactor, controlling the temperature of the system to be 10-20 ℃, adding a mixture of 1-2 parts of graphite powder and 3-5 parts of permanganate into the reactor while stirring, keeping the temperature of the system to be 10-20 ℃ in the feeding process, keeping the temperature to be 10-20 ℃ after feeding is finished, and continuously stirring to obtain a reaction mixture;
step two: transferring the reaction mixture obtained in the first step into a ball milling tank of a ball mill, and carrying out wet ball milling in three stages, wherein the mass ratio of ball materials is 300-400: 1 during ball milling, and the ball milling rotating speed in the first stage is 100-150 r/min; the ball milling rotating speed of the second stage is 300-350 r/min; in the third stage, the ball milling rotation speed is 500-550 r/min, and a ball milling product is obtained after ball milling is completed;
step three: and D, taking out the ball-milled product obtained in the step two, transferring the ball-milled product into a reactor, adding 100-150 parts of water into the reactor while stirring, cooling the product in the reactor to 35-40 ℃, adding 5-10 parts of hydrogen peroxide into the reactor, and finally repeatedly performing centrifugal precipitation and washing on the product until no sulfate radical is detected in the washing liquid by using a barium chloride solution, thereby obtaining the less-lamellar graphene oxide dispersion liquid.
The strong acid in the first step is concentrated sulfuric acid and concentrated phosphoric acid, and the weight ratio of the strong acid to the concentrated phosphoric acid is 10: 2, wherein the mass fraction concentration of the concentrated sulfuric acid is 98 percent, and the mass fraction concentration of the concentrated phosphoric acid is 85 percent.
The granularity of the graphite powder in the step one is 200-400 meshes, and the carbon content is 90-99%.
The permanganate in the step one is one of potassium permanganate, sodium permanganate and lithium permanganate, the granularity is 100 meshes, and the purity is more than 99%.
In the first step, a mixture of 1-2 parts of graphite powder and 3-5 parts of permanganate is added into the reactor within 15-20 minutes, and the continuous stirring time is 0.5-1 hour.
The ball mill in the second step is a planetary ball mill, the grinding balls are composed of stainless steel balls with the diameters of 2mm, 4mm, 6mm, 8mm, 10mm, 12mm and 15mm and the corresponding mass ratio of 10-15: 15-20: 20-25: 25-30: 30-35: 35-40: 40-45, and the ball milling tank is made of nylon materials.
In the second step, the ball milling time of the first stage is 1-1.5 hours, the ball milling time of the second stage is 1.5-2 hours, and the ball milling time of the third stage is 2-2.5 hours.
In the third step, 100-150 parts of water is added into the reactor within 25-30 minutes while stirring, the hydrogen peroxide is industrially pure and has a mass fraction of 30%, the hydrogen peroxide is added into the reactor within 20-25 minutes, and the barium chloride solution has a mass fraction concentration of 25% and is prepared by dissolving analytically pure barium chloride in deionized water.
And in the third step, the operation process of repeated centrifugal precipitation and washing is that 10000-15000 rpm high-speed centrifuge is used for centrifugal precipitation for 3-5 minutes, the lower layer of the centrifuge tube is graphene oxide precipitate, the upper layer of the centrifuge tube is clear liquid, then the clear liquid on the upper layer of the centrifuge tube is poured, deionized water is added into the centrifuge tube to the position of the original clear liquid, the mixture is uniformly stirred by a glass rod, and the operation process of centrifugal precipitation and washing is repeated.
The graphene oxide in the few-lamellar graphene oxide dispersion liquid prepared by the preparation method has less than or equal to 3 graphene oxide lamella layers, the thickness of 1-3 nm, the lamella size of 0.2-1.2 mu m and the specific surface area of 600-900 m2The oxygen content is 25 to 30 percent. High oxidation degree and excellent performance.
Compared with the prior art, the invention has the beneficial effects that:
according to the invention, under the action of friction and shearing force generated during ball milling, the graphite powder is subjected to modified oxidation and dispersion, and the acting force and temperature required by the system can be maintained by regulating and controlling the ball milling rotating speed in the three ball milling stages of the step 2), so that the preparation process only needs to regulate and control the ball milling rotating speed, and the operation is simple; the graphene oxide is prepared by the traditional Hummers method within 23-30 hours, and the method only requires 5-7 hours, so that the reaction time is greatly shortened, and the preparation efficiency is high; according to the invention, a certain temperature can be maintained under the mechanical friction action in the ball milling process and the generated friction heat, the penetration and oxidation of permanganate and the like among graphite flake layers are facilitated, only 10-20 parts of strong acid and 3-5 parts of permanganate are needed for preparing each 1-2 parts of graphene, and compared with the traditional Hummers method which uses 60-80 parts of strong acid and 6-10 parts of permanganate, the dosage of the strong acid and the permanganate is obviously reduced, and sodium nitrate is not needed, so that the raw material is saved, and pollutants such as harmful gas and harmful liquid generated by using the strong acid, the permanganate and nitric acid are reduced; the graphene oxide lamella in the obtained graphene oxide dispersion liquid has smaller thickness and lamella plane size and larger specific surface area than the Hummers method. Meanwhile, compared with the traditional Hummers method, the method has the advantages that the low-temperature reaction temperature is increased from 0-5 ℃ to 20-30 ℃, the operation is convenient, and the cost is reduced; the high-temperature reaction temperature is reduced to 50-60 ℃ from 80-95 ℃, so that the operation is convenient, the cost is reduced, the reaction safety is improved, and the method is suitable for large-area popularization and use.
Detailed Description
The present invention will be described in detail with reference to specific examples.
Example 1:
the method comprises the following steps: according to the following steps: 2, mixing 98% concentrated sulfuric acid and 85% concentrated phosphoric acid by mass to obtain a strong acid solution, adding 10 parts of the strong acid solution by mass into a reactor, controlling the temperature of the system to be 20 ℃, adding a mixture of 1 part of graphite powder with the granularity of 200-400 meshes and the carbon content of 90-99% and 3 parts of sodium permanganate with the granularity of 100 meshes while stirring, keeping the temperature of the system at 20 ℃ in the feeding process, keeping the temperature at 20 ℃ after the feeding is finished, and continuously stirring for 0.5 hour to obtain a reaction mixture;
step two: transferring the reaction mixture obtained in the first step into a nylon ball milling tank of a planetary ball mill, and carrying out wet ball milling in three stages, wherein the mass ratio of ball materials is 300: 1, grinding balls comprise stainless steel balls with the diameters of 2mm, 4mm, 6mm, 8mm, 10mm, 12mm and 15mm and the corresponding mass ratio of 10:15:20:25:30:35:40, the ball milling speed in the first stage is 100 revolutions per minute, and the temperature of a first-stage system is maintained at 20 ℃ by heat generated in the ball milling process; the ball milling speed of the second stage is 300 r/min for 1.5 hours, and the temperature of the second stage system can be maintained at 40 ℃ by the heat generated in the ball milling process; the ball milling rotation speed of the third stage is 500 r/min for 2 hours, the temperature of the system in the third stage can be maintained at 50 ℃ by the heat generated in the ball milling process, and a ball milling product is obtained after the ball milling is finished;
step three: and (3) taking out the ball-milled product obtained in the second step, transferring the ball-milled product into a reactor, adding 100 parts of water into the reactor within 25 minutes while stirring, cooling the product in the reactor to 40 ℃, adding 5 parts of hydrogen peroxide with the mass fraction of 30% into the reactor within 20 minutes, enabling the color of the system to become bright yellow, carrying out centrifugal precipitation for 3-5 minutes by using a 10000-15000 r/min high-speed centrifuge, enabling the lower layer of the centrifuge tube to be graphene oxide precipitate and the upper layer to be clear liquid, pouring the clear liquid on the upper layer of the centrifuge tube, adding deionized water into the centrifuge tube to the position of the original clear liquid, uniformly stirring by using a glass rod, and repeatedly carrying out centrifugal precipitation and washing until the barium chloride solution in the washing liquid can not detect the existence, thus obtaining the less-lamellar graphene oxide sulfate radical dispersion liquid.
The graphene oxide prepared in the embodiment has about 3 graphene oxide sheets, a thickness of 2.98nm and a specific surface area of 610m2Oxygen content 25% per gram.
Example 2:
the method comprises the following steps: according to the following steps: 2, mixing 98% concentrated sulfuric acid and 85% concentrated phosphoric acid by mass to obtain a strong acid solution, adding 18 parts of the strong acid solution into a reactor by mass, controlling the temperature of the system to be 15 ℃, stirring while adding 1 part of graphite powder with the granularity of 200-400 meshes and the carbon content of 90-99% and 3 parts of high-lithium manganate with the granularity of 100 meshes into the reactor within 15 minutes, keeping the temperature of the system to be 15 ℃ in the feeding process, keeping the temperature to be 15 ℃ after feeding, and continuously stirring for 1 hour to obtain a reaction mixture;
step two: transferring the reaction mixture obtained in the first step into a nylon ball milling tank of a planetary ball mill, and carrying out wet ball milling in three stages, wherein the mass ratio of ball materials is 360: 1, grinding balls comprise stainless steel balls with the diameters of 2mm, 4mm, 6mm, 8mm, 10mm, 12mm, 15mm and the corresponding mass ratio of 12:16:21:26:31:36:42, the ball milling speed in the first stage is 150 revolutions per minute, and the temperature of a first-stage system is kept at 25 ℃ by heat generated in the ball milling process; the ball milling speed of the second stage is 310 r/min for 1.5 hours, and the temperature of the second stage system can be maintained at 45 ℃ by the heat generated in the ball milling process; the ball milling rotation speed of the third stage is 500 r/min for 2 hours, the temperature of the system in the third stage can be maintained at 55 ℃ by the heat generated in the ball milling process, and a ball milling product is obtained after the ball milling is finished;
step three: and (2) taking out the ball-milled product obtained in the step two, transferring the ball-milled product into a reactor, adding 150 parts of water into the reactor within 30 minutes while stirring, cooling the product in the reactor to 37 ℃, adding 5 parts of hydrogen peroxide with the mass fraction of 30% into the reactor within 20 minutes, enabling the color of the system to become bright yellow, carrying out centrifugal precipitation for 3-5 minutes by using a 10000-15000 r/min high-speed centrifuge, enabling the lower layer of the centrifuge tube to be graphene oxide precipitate and the upper layer to be clear liquid, pouring the clear liquid on the upper layer of the centrifuge tube, adding deionized water into the centrifuge tube to the position of the original clear liquid, uniformly stirring by using a glass rod, and repeatedly carrying out centrifugal precipitation and washing until the barium chloride solution in the washing liquid can not detect the existence, thus obtaining the less-lamellar graphene oxide sulfate radical dispersion liquid.
The graphene oxide sheet layer prepared in the embodiment is about 2 layers, the thickness is 2.1nm, and the specific surface area is 714m2Oxygen content of 26% per gram.
Example 3:
the method comprises the following steps: according to the following steps: 2, mixing 98% concentrated sulfuric acid and 85% concentrated phosphoric acid by mass to obtain a strong acid solution, adding 20 parts of the strong acid solution into a reactor by mass, controlling the temperature of the system to be 10 ℃, stirring while adding a mixture of 2 parts of graphite powder with the granularity of 200-400 meshes and the carbon content of 90-99% and 5 parts of potassium permanganate with the granularity of 100 meshes into the reactor within 20 minutes, keeping the temperature of the system to be 10 ℃ in the feeding process, keeping the temperature to be 10 ℃ after feeding, and continuing stirring for 1 hour to obtain a reaction mixture;
step two: transferring the reaction mixture obtained in the first step into a nylon ball milling tank of a planetary ball mill, and carrying out wet ball milling in three stages, wherein the mass ratio of ball materials is 400: 1 during ball milling, grinding balls consist of stainless steel balls with the diameters of 2mm, 4mm, 6mm, 8mm, 10mm, 12mm and 15mm and the corresponding mass ratio of 13:18:23:28:33:38:43, the ball milling speed in the first stage is 150 revolutions per minute for 1.5 hours, and the temperature of a system in the first stage is maintained at 30 ℃ by heat generated in the ball milling process; the ball milling speed of the second stage is 320 r/min for 2 hours, and the temperature of the second stage system can be maintained at 48 ℃ by the heat generated in the ball milling process; the ball milling rotation speed of the third stage is 550 revolutions per minute for 2.5 hours, the temperature of the system in the third stage can be maintained at 60 ℃ by the heat generated in the ball milling process, and a ball milling product is obtained after the ball milling is finished;
step three: and (2) taking out the ball-milled product obtained in the step two, transferring the ball-milled product into a reactor, adding 150 parts of water into the reactor within 30 minutes while stirring, cooling the product in the reactor to 35 ℃, adding 10 parts of hydrogen peroxide with the mass fraction of 30% into the reactor within 25 minutes, enabling the color of the system to become bright yellow, carrying out centrifugal precipitation for 3-5 minutes by using a 10000-15000 r/min high-speed centrifuge, enabling the lower layer of the centrifuge tube to be graphene oxide precipitate and the upper layer to be clear liquid, pouring the clear liquid on the upper layer of the centrifuge tube, adding deionized water into the centrifuge tube to the position of the original clear liquid, uniformly stirring by using a glass rod, and repeatedly carrying out centrifugal precipitation and washing until the barium chloride solution in the washing liquid can not detect the existence, thus obtaining the less-lamellar graphene oxide sulfate radical dispersion liquid.
The graphene oxide sheet prepared in the embodiment has about 1 layer, the thickness of 1.03nm and the specific surface area of 882m2(iv)/g, oxygen content 30%.
Example 4:
the method comprises the following steps: according to the following steps: 2, mixing 98% concentrated sulfuric acid and 85% concentrated phosphoric acid by mass to obtain a strong acid solution, adding 13 parts of the strong acid solution by mass into a reactor, controlling the temperature of the system to be 14 ℃, adding a mixture of 1 part of graphite powder with the granularity of 200-400 meshes and the carbon content of 90-99% and 5 parts of sodium permanganate with the granularity of 100 meshes while stirring, keeping the temperature of the system at 14 ℃ in the feeding process, keeping the temperature at 14 ℃ after the feeding is finished, and continuously stirring for 0.5 hour to obtain a reaction mixture;
step two: transferring the reaction mixture obtained in the step one into a nylon ball milling tank of a planetary ball mill, and carrying out wet ball milling in three stages, wherein the ball-material mass ratio is 330: 1, grinding balls are composed of stainless steel balls with the diameters of 2mm, 4mm, 6mm, 8mm, 10mm, 12mm and 15mm and the corresponding mass ratio of 14:19:24:29:34:39:44, the ball milling speed of the first stage is 100 revolutions per minute for 1 hour, and the temperature of a first stage system is maintained at 23 ℃ by heat generated in the ball milling process; the ball milling speed of the second stage is 340 r/min for 2 hours, and the temperature of the second stage system can be maintained at 42 ℃ by the heat generated in the ball milling process; the ball milling speed of the third stage is 500 r/min for 2 hours, the temperature of the system in the third stage can be maintained at 57 ℃ by the heat generated in the ball milling process, and a ball milling product can be obtained after the ball milling is finished;
step three: and (2) taking out the ball-milled product obtained in the step two, transferring the ball-milled product into a reactor, adding 100 parts of water into the reactor within 25 minutes while stirring, cooling the product in the reactor to 38 ℃, adding 10 parts of hydrogen peroxide with the mass fraction of 30% into the reactor within 25 minutes, enabling the color of the system to become bright yellow, carrying out centrifugal precipitation for 3-5 minutes by using a 10000-15000 r/min high-speed centrifuge, enabling the lower layer of the centrifuge tube to be graphene oxide precipitate and the upper layer to be clear liquid, pouring the clear liquid on the upper layer of the centrifuge tube, adding deionized water into the centrifuge tube to the position of the original clear liquid, uniformly stirring by using a glass rod, and repeatedly carrying out centrifugal precipitation and washing until the barium chloride solution in the washing liquid can not detect the existence, thus obtaining the less-lamellar graphene oxide sulfate radical dispersion liquid.
The graphene oxide prepared in the example has about 3 graphene oxide sheets, a thickness of 2.75nm and a specific surface area of 638m2Oxygen content of 28% per gram.
Example 5:
the method comprises the following steps: according to the following steps: 2, mixing 98% concentrated sulfuric acid and 85% concentrated phosphoric acid by mass to obtain a strong acid solution, adding 15 parts of the strong acid solution by mass into a reactor, controlling the temperature of the system to be 12 ℃, adding a mixture of 1.5 parts of graphite powder with the carbon content of 90-99% and 4 parts of potassium permanganate with the granularity of 100 meshes and the purity of more than 99% into the reactor while stirring, keeping the temperature of the system to be 12 ℃ in the feeding process, and continuously stirring for 1 hour to obtain a reaction mixture;
step two: transferring the reaction mixture obtained in the first step into a nylon ball milling tank of a planetary ball mill, and carrying out wet ball milling in three stages, wherein the mass ratio of ball materials is 350: 1 during ball milling, and the grinding balls are prepared from materials with the diameters of 2mm, 4mm, 6mm, 8mm, 10mm, 12mm and 15mm, and the corresponding mass ratio is 15:20:25:30:35: 40:45, wherein the ball milling speed of the first-stage ball milling is 125 r/min for 1.5 hours, and the heat generated in the ball milling process can maintain the temperature of a first-stage system at 28 ℃; the ball milling speed of the second stage is 350 r/min for 1.5 hours, and the temperature of the second stage system can be maintained at 50 ℃ by the heat generated in the ball milling process; the ball milling rotation speed of the third stage is 525 r/min for 2.5 hours, the temperature of the system in the third stage is maintained at 50 ℃ by the heat generated in the ball milling process, and a ball milling product is obtained after the ball milling is finished;
step three: and (3) taking out the ball-milled product obtained in the second step, transferring the ball-milled product into a reactor, adding 125 parts of water into the reactor within 27 minutes while stirring, cooling the product in the reactor to 36 ℃, adding 7 parts of hydrogen peroxide with the mass fraction of 30% into the reactor within 23 minutes, enabling the color of the system to become bright yellow, carrying out centrifugal precipitation for 3-5 minutes by using a 10000-15000 r/min high-speed centrifuge, enabling the lower layer of the centrifuge tube to be graphene oxide precipitate and the upper layer to be clear liquid, pouring the clear liquid on the upper layer of the centrifuge tube, adding deionized water into the centrifuge tube to the position of the original clear liquid, uniformly stirring by using a glass rod, and repeatedly carrying out centrifugal precipitation and washing until the barium chloride solution in the washing liquid can not detect the existence, thus obtaining the less-lamellar graphene oxide sulfate radical dispersion liquid.
The graphene oxide sheet prepared in the embodiment has about 2 layers, the thickness of 2.26nm and the specific surface area of 784m2Oxygen content of 27% per g.
The following table compares the preparation process of the present invention with the conventional Hummers process.