Method for producing graphite oxide

1. A method for producing graphite oxide by oxidizing graphite, the method comprising:

oxidizing graphite by adding a permanganate to a liquid mixture containing graphite and sulfuric acid while maintaining the concentration of heptavalent manganese at 1% by mass or less in 100% by mass of the liquid mixture; and

adding the liquid mixture obtained in the oxidation step to water or a hydrogen peroxide solution in an amount of 120% by mass or more for 100% by mass of the liquid mixture obtained in the oxidation to terminate the oxidation step,

wherein a mass ratio of sulfuric acid to graphite is 25 to 60 in the liquid mixture used in a reaction in the oxidation step.

2. The method for producing graphite oxide according to claim 1 , the method further comprising:

purifying graphite oxide obtained in the oxidation step, the purification step comprising the step of allowing a graphite oxide-containing liquid to stand at 30° C. to 90° C. and then separating a supernatant liquid.

3. The method for producing graphite oxide according to claim 1 , the method further comprising:

recovering the sulfuric acid used in the reaction in the oxidation step;

mixing the recovered sulfuric acid with graphite; and

oxidizing graphite by adding an oxidant to a liquid mixture obtained in the mixing step.

4. The method for producing graphite oxide according to claim 1 ,

wherein the total amount of the permanganate added in the oxidation step is 50% to 500% by mass for 100% by mass of the graphite in the liquid mixture used in the reaction in the oxidation step.

5. The method for producing graphite oxide according to claim 1 ,

wherein the oxidation step comprises adding a permanganate while maintaining the temperature variation of the liquid mixture used in the reaction in the oxidation step within 25° C.

6. The method for producing graphite oxide according to claim 1 ,

wherein the graphite used in the reaction in the oxidation step has a Raman spectrum in which the ratio of the peak intensity of the D band to the peak intensity of the G band is 0.4 or less.

7. The method for producing graphite oxide according to claim 1 ,

wherein the graphite used in the reaction in the oxidation step has a spacing of the (002) planes of 3.3 Å or larger and 3.4 Å or smaller determined by X-ray diffraction in crystals.

8. The method for producing graphite oxide according to claim 1 ,

wherein the graphite used in the reaction in the oxidation step has an average particle size of 3 μm or greater and 80 μm or smaller.

9. The method for producing graphite oxide according to claim 1 ,

wherein the graphite used in the reaction in the oxidation step has a specific surface area of 3 m 2 /g or larger and 10 m 2 /g or smaller.

10. The method for producing graphite oxide according to claim 1 ,

wherein the addition step of the liquid mixture comprises adding the liquid mixture obtained in the oxidation step to a hydrogen peroxide solution.

11. The method for producing graphite oxide according to claim 1 ,

wherein the concentration of the hydrogen peroxide solution in the addition step of the liquid mixture is 10% by mass or less.

12. The method for producing graphite oxide according to claim 1 ,

wherein the addition step of the liquid mixture comprises adding the liquid mixture obtained in the oxidation step while maintaining the temperature of the water or the hydrogen peroxide solution at 60° C. or lower.

13. The method for producing graphite oxide according to claim 1 ,

wherein the addition step of the liquid mixture comprises adding the liquid mixture obtained in the oxidation step while maintaining the temperature variation of the water or the hydrogen peroxide solution within 40° C.

14. The method for producing graphite oxide according to claim 2 ,

wherein the graphite oxide-containing liquid is allowed to stand at 30° C. to 90° C. for 0.1 to 24 hours.

15. The method for producing graphite oxide according to claim 2 ,

wherein the ratio between the mass of the graphite used in the oxidation step and the mass of the graphite oxide-containing liquid subjected to the purification step is 0.0001 to 0.05.

16. The method for producing graphite oxide according to claim 3 ,

wherein the oxidant is a permanganate.

17. The method for producing graphite oxide according to claim 16 ,

wherein the sulfuric acid used in the mixing step has a manganese concentration of 10000 ppm or lower.

18. A method for producing reduced graphite oxide by reducing graphite oxide, the method comprising:

oxidizing graphite by adding a permanganate to a liquid mixture containing graphite and sulfuric acid while maintaining the concentration of heptavalent manganese at 1% by mass or less in 100% by mass of the liquid mixture, and adding the liquid mixture obtained in the oxidation step to water or a hydrogen peroxide solution in an amount of 120% by mass or more for 100% by mass of the liquid mixture to terminate the oxidation step

purifying graphite oxide obtained in the oxidation step; and

reducing graphite oxide obtained in the purification step,

wherein the purification step comprises allowing a graphite oxide-containing liquid to stand at 30° C. to 90° C. and then separating a supernatant liquid, and

the mass ratio of sulfuric acid to graphite is 25 to 60 in the liquid mixture used in the reaction in the oxidation step.

19. A method for storing sulfuric acid, the method comprising:

storing sulfuric acid recovered after use in a method for producing graphite oxide by oxidizing graphite by adding a permanganate to a liquid mixture containing graphite and sulfuric acid while maintaining the concentration of heptavalent manganese at 1% by mass or less in 100% by mass of the liquid mixture, and adding the liquid mixture obtained in the oxidation step to water or a hydrogen peroxide solution in an amount of 120% by mass or more for 100% by mass of the liquid mixture to terminate the oxidation step.

wherein the storing method comprises adding graphite to the recovered sulfuric acid and storing them, and

the mass ratio of sulfuric acid to graphite is 25 to 60 in the liquid mixture used in the reaction in the oxidation step.

20. The method for storing sulfuric acid according to claim 19 ,

wherein the storing step comprises maintaining the temperature of a liquid prepared by adding graphite to the recovered sulfuric acid at 20° C. or lower.