Method for preparing graphene oxide by taking corncob as carbon source

Abstract

The invention relates to a method for preparing graphene oxide by taking corncobs as a carbon source. The method is characterized by comprising the following steps: (1) crushing and sieving the corncobs, adding an HCl solution, stirring, filtering, washing and drying; (2) adding a Fe2O3 catalyst into the powder, grinding and uniformly mixing, transferring into a tubular furnace, and carbonizing in a protective atmosphere to obtain biomass graphite; (3) uniformly mixing sodium nitrate and concentrated sulfuric acid, adding biomass graphite while stirring, adding potassium permanganate, uniformly stirring, reacting at 10-15 DEG C for 1-2 hours, heating to 30-40 DEG C, reacting while stirring for 0.5-1 hour, adding deionized water, continuously stirring at 98 DEG C for 15-30 minutes, adding deionized water to terminate the reaction, adding hydrogen peroxide, filtering while hot, and washing a filter cake with hydrochloric acid and deionized water until the filter cake is neutral; re-dispersing the filter cake into water to form a uniform solution, carrying out ultrasonic stripping treatment, and centrifuging to obtain supernate; the method has the advantages that the prepared graphene oxide has the characteristics of large size and high stripping degree, and a better path is provided for preparing large-size and high-quality graphene.

Description

Technical Field

[0001] The invention belongs to the field of graphene oxide preparation and relates to a method for preparing graphene oxide by taking corn cobs as a carbon source. Background Art

[0002] As an important derivative of graphene, graphene oxide not only has many characteristics of its own, but is also regarded as an important strategic starting point for the graphene industry. There are three main methods for preparing graphene oxide: Brodie method, Staudenmair method and Hummers method. It is worth noting that these methods generally use natural flake graphite as raw material, and then chemically oxidize the surface and edge of the graphite sheet to contain a large number of oxygen-containing groups such as hydroxyl, carboxyl and epoxy, and then peel off to finally obtain graphene oxide. There are generally problems such as carbon source limitation, high production cost, and small size of the obtained graphene oxide.

[0003] my country's annual production of corn cobs is as high as hundreds of millions of tons. As biological straw, corn cobs are often used for burning and cooking or discarded in fields, causing a lot of waste and pollution.

[0004] Patent publication number CN111533111B discloses a method for preparing biomass graphene hydrogen storage materials. The method uses agricultural and forestry waste such as reed straw, water hyacinth, bagasse, wood chips, corn cobs, etc. as raw materials, and adopts a "crushing-carbonization-stripping-defunctionalization" process. However, the prepared graphene is a few-layer graphene, and the quality of the graphene product needs to be further improved. Summary of the invention

[0005] The purpose of the present invention is to make up for the deficiencies of the prior art, improve the quality of graphene oxide, and provide a method for preparing graphene oxide using corn cobs as a carbon source.

[0006] In order to achieve the above object, the technical solution adopted by the present invention is as follows: A method for preparing graphene oxide using corn cobs as a carbon source, characterized by comprising the following steps: (1) Corn cob pretreatment: grind the corn cob into powder with a crusher, sieve to obtain corn cob powder with a mesh size of 80 to 100, add HCl solution to the corn cob powder and stir for 14 to 18 hours, filter, wash, and dry for later use; (2) Carbonization and graphitization: Add 15-20 wt% of Fe2O3 catalyst to the powder obtained by drying, grind and mix well, transfer to a tube furnace, introduce protective gas into the tube furnace for carbonization treatment, and obtain biomass graphite; (3) Acidification and stripping: Sodium nitrate and concentrated sulfuric acid (98%) were mixed evenly at a mass volume ratio of 0.1:5-10 (g / mL), and biomass graphite was added under stirring. After mixing evenly, potassium permanganate was added, and the mass ratio of sodium nitrate: biomass graphite: potassium permanganate was controlled to be 5:1:0.3-0.5. After stirring evenly, the mixture was reacted at 10-15 °C for 1-2 h, and then the temperature was raised to 30-40 °C and the reaction was continued under stirring for 0.5-1 h. After that, deionized water with a volume of 2-4 times that of concentrated sulfuric acid was added, and the reaction liquid temperature was controlled at 98 °C. Stirring was continued for 15-30 min, and then deionized water was added to terminate the reaction. Subsequently, hydrogen peroxide with a mass concentration of 30% was added for oxidation, and the mixture was filtered while hot, and the filter cake was washed with hydrochloric acid solution until there was no SO4 in the filtrate. 2- , and then washed with deionized water until neutral; the obtained filter cake was redispersed in water to form a uniform solution, subjected to ultrasonic stripping treatment, and centrifuged to obtain a supernatant which is an aqueous solution of graphene oxide.

[0007] Furthermore, in step (1), the mass concentration of the HCl solution is 10-20%, and the mass volume ratio of the corn cob powder to the HCl solution is 1:10 (g / mL).

[0008] Furthermore, in step (1), the drying temperature is 90 to 100° C. and the drying time is 24 to 48 hours.

[0009] Furthermore, the carbonization treatment conditions in step (2) are as follows: heating to 600°C at a heating rate of 10°C / min, keeping the temperature for 2-3 hours, then heating to 1100°C at a heating rate of 10°C / min, keeping the temperature for 6-8 hours, and then cooling down to room temperature.

[0010] Furthermore, the protective gas in step (2) is one of nitrogen, argon, and helium, or a mixture of any of them in any proportion.

[0011] Furthermore, the conditions for the ultrasonic stripping treatment in step (3) are: ultrasonic frequency of 30 to 50 kHz, ultrasonic power of 100 to 150 W, and ultrasonic time of 20 to 60 min.

[0012] Furthermore, the centrifugation condition in step (3) is: centrifuge at 4000-6000 r / min for 3-5 min.

[0013] Beneficial effects of the present invention: (1) The present invention uses biomass corn cobs as raw materials to prepare graphene oxide, and adopts a "crushing-carbonization-graphitization-oxidation-stripping" process flow, which solves the problems existing in the previous graphene oxide preparation process, such as carbon source limitation, high production cost, carbon source limitation, and small size of the obtained graphene oxide. It has the advantages of low production cost, abundant raw material sources, high product quality, and good repeatability, and has broad application prospects; (2) The graphene oxide produced by the present invention has the characteristics of large size (up to 2 to 5 microns) and high exfoliation (single layer), which provides a better path for preparing large-size, high-quality graphene. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 A schematic diagram of the process for preparing biomass graphite; Figure 2 This is a photo of the dispersion of graphene oxide in water prepared by the present invention. It can be seen from the figure that the graphene oxide is highly dispersed in water; Figure 3 This is a TEM image of the graphene oxide prepared in the present invention. It can be seen from the figure that the obtained graphene oxide is in a highly exfoliated state and is almost integrated with the background. The middle of the sheet is relatively flat, while the edges and the middle of the graphene sheet have obvious curling and wrinkles, which is mainly caused by the curling and folding of this part. DETAILED DESCRIPTION

[0015] A method for preparing graphene oxide using corn cobs as a carbon source, the specific implementation steps are as follows: Example

[0016] (1) Corncob pretreatment: First, grind the corncob into powder with a crusher, and sieve it with an 80-mesh sieve to obtain corncob powder. Add 5 g of corncob powder into a beaker, add 100 mL of 10% HCl solution, stir for 16 h, filter, wash until neutral, and dry at 90 °C for 30 h for later use; (2) Carbonization and graphitization: 0.675 g of Fe2O3 catalyst was added to 4.5 g of the powder obtained in step (1), and the mixture was ground and mixed, and then transferred into a tubular furnace, and nitrogen protective gas was introduced for carbonization treatment. The carbonization treatment conditions were: heating to 600°C at a heating rate of 10°C / min, keeping the temperature for 2 h, and then heating to 1100°C at a heating rate of 10°C / min, keeping the temperature for 6 h, and then cooling to room temperature to obtain biomass graphite; (3) Acidification and stripping: Take 25 mL of 98% concentrated sulfuric acid and 0.5 g of sodium nitrate and mix them evenly. Add 1.0 g of biomass graphite obtained in step (2) under constant stirring. After mixing evenly, add 0.3 g of potassium permanganate. Control the reaction temperature to 10 °C. After reacting for 2 h, heat it to 35 °C. Continue stirring the reaction for 1 h. Then add 50 mL of deionized water. Control the temperature of the reaction solution to 98 °C. Continue stirring for 15 min. Then add 120 mL of deionized water to terminate the reaction. Add 3 mL of 30% hydrogen peroxide for oxidation. Filter while hot and wash with hydrochloric acid solution (10% mass concentration) until there is no SO4 in the filtrate. 2- , and then washed with deionized water until neutral; the obtained filter cake was redispersed in water to form a uniform solution, and ultrasonic stripping was performed for 20 min, wherein the ultrasonic frequency was 50 KHz and the ultrasonic power was 150 W; then centrifuged at 4000 r / min for 3 min in a centrifuge, and the obtained supernatant was an aqueous solution of graphene oxide. Example

[0017] (1) Corncob pretreatment: First, grind the corncob into powder with a crusher, and sieve it with a 90-mesh sieve to obtain corncob powder. Add 6 g of corncob powder into a beaker, add 120 mL of 20% HCl solution, stir for 15 h, filter, wash until neutral, and dry at 100 °C for 24 h for use; (2) Carbonization and graphitization: add 1 g of Fe2O3 catalyst to 5 g of the powder obtained in step (1), grind and mix well, transfer into a tubular furnace, introduce argon protective gas for carbonization treatment, wherein the carbonization treatment conditions are: increase the temperature to 600°C at a heating rate of 10°C / min, keep the temperature for 2.5 h, then continue to increase the temperature to 1100°C at a heating rate of 10°C / min, keep the temperature for 7 h, and then cool to room temperature to obtain biomass graphite; (3) Acidification and stripping: Take 25 mL of 98% concentrated sulfuric acid and 0.5 g of sodium nitrate and mix them evenly. Add 1.0 g of biomass graphite obtained in step (2) under constant stirring. After mixing evenly, add 0.3 g of potassium permanganate. Control the reaction temperature to 15 °C. After reacting for 1 h, heat it to 35 °C. Continue stirring the reaction for 0.5 h. Then add 50 mL of deionized water. Control the temperature of the reaction solution to 98 °C. Continue stirring for 15 min. Then add 120 mL of deionized water to terminate the reaction. Add 3 mL of 30% hydrogen peroxide for oxidation. Filter while hot and wash with hydrochloric acid solution (mass concentration 20%) until there is no SO4 in the filtrate. 2-, and then washed with deionized water until neutral; the obtained filter cake was redispersed in water to form a uniform solution, and ultrasonic stripping was performed for 20 min, wherein the ultrasonic frequency was 30KHz and the ultrasonic power was 100W; then centrifuged at 5000 r / min for 3 min in a centrifuge, and the obtained supernatant was an aqueous solution of graphene oxide.

Claims

1. A method for preparing graphene oxide using corn cobs as a carbon source, characterized in that The steps include: (1) Corn cob pretreatment: grind the corn cob into powder with a crusher, sieve to obtain corn cob powder with a mesh size of 80 to 100, add HCl solution to the corn cob powder and stir for 14 to 18 hours, filter, wash, and dry for later use; (2) Carbonization and graphitization: Add 15-20 wt% of Fe2O3 catalyst to the powder obtained by drying, grind and mix well, transfer to a tube furnace, introduce protective gas into the tube furnace for carbonization treatment, and obtain biomass graphite; (3) Acidification and stripping: Sodium nitrate and concentrated sulfuric acid are mixed evenly at a mass volume ratio of 0.1:5-10, and biomass graphite is added under stirring. After mixing evenly, potassium permanganate is added, and the mass ratio of sodium nitrate: biomass graphite: potassium permanganate is controlled to be 5:1:0.3-0.

5. After stirring evenly, react at 10-15 °C for 1-2 h, then heat to 30 °C-40 °C and continue stirring for 0.5-1 h, then add deionized water 2-4 times the volume of concentrated sulfuric acid, control the reaction liquid temperature at 98 °C, continue stirring for 15-30 min, then add deionized water to terminate the reaction, and then add 30% mass concentration of hydrogen peroxide for oxidation, filter while hot, and wash the filter cake with hydrochloric acid solution until there is no SO4 in the filtrate. 2- , and then washed with deionized water until neutral; the obtained filter cake was redispersed in water to form a uniform solution, ultrasonically stripped, and centrifuged to obtain a supernatant as an aqueous solution of graphene oxide.

2. A method for preparing graphene oxide using corn cobs as a carbon source according to claim 1, characterized in that: The mass concentration of the HCl solution in step (1) is 10-20%, and the mass volume ratio of the corncob powder to the HCl solution is 1:

10.

3. A method for preparing graphene oxide using corn cobs as a carbon source according to claim 1, characterized in that: The drying temperature in step (1) is 90-100° C. and the drying time is 24-48 hours.

4. The method for preparing graphene oxide using corn cobs as a carbon source according to claim 1, characterized in that: The carbonization treatment conditions in step (2) are as follows: heating to 600°C at a heating rate of 10°C / min, keeping the temperature for 2-3 hours, then heating to 1100°C at a heating rate of 10°C / min, keeping the temperature for 6-8 hours, and then cooling down to room temperature.

5. The method for preparing graphene oxide using corncobs as a carbon source according to claim 1, characterized in that: In step (2), the protective gas is one of nitrogen, argon, and helium, or a mixture of any of them in any proportion.

6. The method for preparing graphene oxide using corn cobs as a carbon source according to claim 1, characterized in that: The conditions for the ultrasonic stripping treatment in step (3) are: ultrasonic frequency of 30 to 50 kHz, ultrasonic power of 100 to 150 W, and ultrasonic time of 20 to 60 min.

7. A method for preparing graphene oxide using corncobs as a carbon source according to any one of claims 1 to 6, characterized in that: The centrifugal conditions in step (3) are: centrifuge at 4000-6000 r / min for 3-5 min.

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