▎ 摘　　要

NOVELTY - Reducing graphene oxide comprises adding vitamin C in a solution of graphene oxide, mixing, adding aqueous ammonia, mixing, heating at 90-100 degrees C, incubating, filtering, washing with deionized water until neutralized and drying, to obtain the reduced graphene oxide. USE - The reduced graphene oxide is useful as a waste liquid treatment agent for reducing the chemical oxygen demand of the fermentation waste liquid (claimed). ADVANTAGE - The method: has simple process; easy operation; and is suitable for industrial production. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for (1) preparing graphene oxide solution comprising (a) adding concentrated sulfuric acid in a reactor, adding potassium persulfate and phosphorus pentoxide, stirring, adding graphite powder at 80 degrees C for 6 hours, washing, diluting with distilled water, pump filtering until the residue is neutral, drying the filtrate, to obtain pre-oxidized graphite, (b) adding concentrated sulfuric acid in the reactor, adding sodium nitrate, dissolving completely, adding pre-oxidized graphite, stirring, mixing, to obtain suspension, adding potassium permanganate at 0-20 degrees C and stirring until the suspension turns from black red color to dark green, heating at 32-38 degrees C, adding water and stirring until the suspension turns into purple, heating at 60 degrees C, adding hydrogen peroxide solution, incubating the reaction until the suspension change into bright yellow color, (c) filtering the suspension of the hydrogen peroxide solution, washing with hot water until the residue is neutral, dispersing the residue in the water, centrifuging, ultrasonically treating, removing the black solid precipitate, dialyzing the supernatant for removing the salt impurities and drying, to obtain solid graphene oxide; (2) the reduced graphene oxide is prepared by the above method; and (3) use of the reduced graphene oxide as a waste liquid treatment agent in the process of reducing the chemical oxygen demand (COD) of the fermentation waste liquid.