▎ 摘　　要

NOVELTY - Environment-friendly preparation of graphene sheet includes ice bath reacting concentrated sulfuric acid, adding graphite powder and potassium permanganate, water bath heating, and adding deionized water and hydrogen peroxide to obtain golden yellow mixture; centrifuging, adding precipitate with hydrochloric acid, centrifuging, removing supernatant, dropping with barium chloride solution and repeating steps until no more white barium sulfate is generated and precipitate is sulfate-free; and adding deionized water, centrifuging, and repeating steps until supernatant and precipitate are neutral. USE - Method for environment-friendly preparation of graphene sheet (claimed). ADVANTAGE - The method is simple and environment-friendly, and solves equipment requirements and long preparation time problems. DETAILED DESCRIPTION - Environment-friendly preparation of graphene sheet comprises: (A) adding 98% concentrated sulfuric acid into container, placing into ice bath, stirring, sequentially adding graphite powder and potassium permanganate when temperature reaches 0-10 degrees C, and stirring for 2-4 hours; placing container into water bath, heating to 15-25 degrees C, stirring for 2-4 hours, adding deionized water, and increasing temperature to 90-95 degrees C while stirring for 30-60 minutes; and adding 10-30 wt.% hydrogen peroxide, continuously stirring until bubbles appears forming golden yellow mixture; (B) placing into centrifuge bottle, centrifuging to obtain first supernatant and first precipitate, removing first supernatant, adding first precipitate with 1-6 wt.% hydrochloric acid, stirring for 5-30 minutes, centrifuging to obtain second supernatant and second precipitate, removing second supernatant, and dropping with 1-5 mol/L barium chloride solution until white barium sulfate is generated; adding second precipitate with 1-6 wt.% dilute hydrochloric acid, stirring for 5-30 minutes, centrifuging to obtain third supernatant and third precipitate, removing third supernatant, and dropping 1-5 mol/L barium chloride solution until white barium sulfate is generated; adding third precipitate with 1-6 wt.% dilute hydrochloric acid, stirring for 5-30 minutes, centrifuging to obtain fourth supernatant and fourth precipitate, removing fourth supernatant, and dropping 1-5 mol/L barium chloride solution until white barium sulfate is generated; and repeating above steps until no more white barium sulfate is generated and no more sulfate present in precipitate; (C) adding with deionized water, stirring for 5-30 minutes, centrifuging, adding deionized water when precipitate is sulfate-free, stirring for 5-30 minutes, centrifuging, adding deionized water when precipitate is sulfate-free, stirring for 5-30 minutes, centrifuging, repeating steps until supernatant and precipitate are neutral; (D) adding neutral precipitate with deionized water, stirring for 5-30 minutes, pouring into vacuum freeze dryer, and freeze-drying to obtain graphene oxide powder; (E) adding deionized water at solid-liquid ratio of 1 g:0.5-2 L, ultrasonically dispersing for 1-5 hours to obtain graphene oxide dispersion; (F) adding ascorbic acid, heating to 40-60 degrees C for 0.5-4 hours, freezing to - 10 degrees C to - 3 degrees C for 6-12 hours, heating to 70-90 degrees C for 0.5-4 hours, and ultrasonically cooling for 10-30 minutes to obtain graphene suspension; and (G) filtering through 0.22-0.45 mu m membrane filter, soaking in deionized water for 12-24 hours, drying, and peeling filter cake as graphene sheet from filter. The graphite and concentrated sulfuric acid has solid-liquid ratio of 1 g:20-30 mL. The graphite powder and potassium permanganate has ratio of 1:3-8. The graphite powder and deionized water has solid-liquid ratio of 1 g:100-200 mL. The graphite and hydrogen peroxide has solid-liquid ratio of 1 g:10-30 mL. The dilute hydrochloric acid and graphite has solid-liquid ratio of 60-100 mL:1 g. The deionized water and graphite has solid-liquid ratio of 60-100 mL:1 g. The deionized water and graphite has liquid-solid ratio of 1 g:60-100 mL. The ascorbic acid and graphene oxide has mass ratio of 1:0.5-4.