▎ 摘　　要

NOVELTY - A mixture of concentrated sulfuric acid and phosphoric acid is poured into reactor with stirrer and heater. Potassium permanganate is added to kettle, and concentrated sulfuric acid is added and stirred. Natural graphite is added to mixture and stirred, to obtain oxidized graphene-containing viscous liquid which is diluted with deionized water. Hydrogen peroxide is added and precipitated. The graphene oxide suspension is purified, provided into cellulose filter membrane, and washed. The aqueous graphene oxide is freeze-dried and heat-reduced, to obtain graphene powder. USE - Preparation of graphene (claimed). ADVANTAGE - The method enables economical and environmentally-friendly preparation of graphene having high quality and yield and excellent compatibility and agglomeration resistance, without using toxic material. DETAILED DESCRIPTION - Concentrated sulfuric acid and phosphoric acid are placed in refrigerator at -20 degrees C to 10 degrees C for 8-12 hours. The mixture of concentrated sulfuric acid and phosphoric acid is removed, poured to 10-150 L reactor with stirrer and heater. The concentrated sulfuric acid has concentration of 98 wt.%. The concentrated phosphoric acid has concentration of 97 wt.%. The volume ratio of concentrated sulfuric acid and concentrated phosphoric acid is 8-10:1. Potassium permanganate is added to kettle, and concentrated sulfuric acid is added to 0.0l-0.125 g potassium permanganate, and stirred for 5-10 minutes. The speed of stirrer is 100-200 rpm. Natural graphite is added to mixture and stirred at 100-200 rpm for 2-3 hours. The mass ratio of potassium permanganate and natural graphite is 1:0.1-0.125. The temperature inside reactor is increased to 50-70 degrees C, stirred for 18-24 hours, and heating is stopped. The reaction mixture is cooled to room temperature, to obtain oxidized graphene-containing viscous liquid. The oxidized graphene-containing viscous liquid is diluted with deionized water, to obtain suspension of graphene oxide. The volume ratio of oxidized graphene-containing viscous liquid and deionized water is 1:5-10. Hydrogen peroxide is added until the color of graphene oxide suspension turns bright yellow. The mixture is maintained still for 5-24 hours, and precipitated to form lower layer containing graphene oxide suspension. The graphene oxide suspension is removed and purified. The aqueous graphene oxide is provided into cellulose filter membrane, and washed with deionized water until the aqueous graphene oxide has pH value of 6-7. The aqueous graphene oxide is freeze-dried, to obtain graphene oxide powder. The graphene oxide powder is heat-reduced at 400-600 degrees C in a furnace under argon atmosphere for 2-4 hours, to obtain graphene powder.