▎ 摘　　要

NOVELTY - Nitrogen-doped hydrothermal carbon/graphene composite film, i.e. amorphous structure lamellar film containing hydroxyl groups, carbonyl groups, ether groups, imino groups, and cyano groups on the surface, the film thickness is 20-80 μm, the distance between the carbon sheets is ID/IGof the Raman spectrum is 0.88-0.95, and the nitrogen content is 3.0-15.06 wt.%. USE - The nitrogen-doped hydrothermal carbon/graphene composite film is useful in adsorption and removal of heavy metal ions in water (claimed). ADVANTAGE - The film has good removal effect on heavy metal ions in wastewater, and has a good industrial application prospect. DETAILED DESCRIPTION - An INDEPENDENT CLAIM is also included for preparing nitrogen-doped hydrothermal carbon/graphene composite film comprising (i) mixing graphene oxide dispersion liquid, waste biomass, nitrogen source and water, ultrasonic treatment to obtain mixed solution, where the waste biomass is pomelo peel or orange peel, (ii) subjecting the mixed solution to hydrothermal reaction at 160-200°C, cooling to obtain nitrogen-doped hydrothermal carbon/graphene composite material, and (iii) vacuum filtering the nitrogen-doped hydrothermal carbon/graphene composite, then freeze-drying to obtain nitrogen-doped hydrothermal carbon/graphene composite film.