▎ 摘　　要

NOVELTY - Preparation of graphene composite material involves: (1) adding graphene and a surfactant to ethanol, ultrasonically processing for 1 hour to obtain a uniformly dispersed graphene suspension, adding a thickener, ultrasonically processing for 40 minutes to obtain a graphene-dispersed mixed solution, heating in a water bath at 75 degrees C for 4-6 hours, stirring, and evaporating to remove a large amount of ethanol until the slurry becomes a paste; (2) drawing three-dimensional graphene composite structure to be printed and inputting into a three-dimensional printer; (3) adding the paste slurry to the printer, and printing the graphene composite material using direct writing-type three-dimensional printing; and (4) freeze-drying the finished product in a freeze dryer for 24 hours. USE - The method is useful for preparing graphene composite material used for purifying sewage (all claimed). ADVANTAGE - The method provides graphene composite material, which can be easily recycled and processed after adsorbing and purifying sewage. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are included for the following: (1) a device for purifying sewage, which comprises a large tank, which is divided into an upper tank and a lower tank, a water inlet arranged at the upper end of the upper tank, an outlet pipe located at the bottom of the lower tank, a stirrer provided in the center of the upper tank, a bolted grille placed at the water outlet of the upper tank, a baffle plate controlled by a timing switch arranged below the grill, a layer of filter screen, and conical protective cover. The graphene composite material is placed inside as an adsorbent for sewage treatment. The bottom of the lower tank and the upper tank are both funnel-shaped. The gap of the grille is 0.8-1 cm. The layer of filter screen fixed by the graphene composite material is provided at the connection between the bottom of the lower tank and the outlet pipe. The conical protective cover is arranged above the filter screen. The symmetrical four ends of the bottom of the protective cover are supported by four hard PVC; and (2) purification of the sewage, which involves (1) pouring the sewage into the upper tank and stirring to make the sewage and the graphene composite material fully contact and react, (2) opening the water outlet in the middle of the upper and lower tanks, so that the sewage after the stirring reaction flows into the lower tank, and (3) filtering the reacted sewage through the graphene composite filter screen of the lower tank, and discharging through the water outlet pipe.