▎ 摘　　要

NOVELTY - Photocatalyst is a fluorine-nitrogen co-doped titanium dioxide/graphene composite material is claimed. The composite material comprises 1-10 wt.% graphene, 80-98.8 wt.% titanium dioxide and 0.1-5 wt.% fluorine and 0.1-5 wt.% nitrogen. USE - The photocatalyst is useful in reduction of chromium-containing wastewater (claimed). ADVANTAGE - The photocatalyst: improve utilization of visible light; has certain reducing ability of hexavalent chromium under visible light (more than 420 nm); and titanium dioxide is basically no response under visible light. DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for: (1) preparing photocatalyst, comprising (i) adding graphite oxide into absolute ethyl alcohol, and carrying out ultrasonic dispersion to obtain suspension, (ii) dropping slowly tetrabutyl titanate into the suspension, reacting under stirring condition, adding hydrofluoric acid, stirring uniformly, then transferring mixed solution into a polytetrafluoroethylene liner of stainless steel reaction kettle, and carrying out solvothermal reaction, (iii) taking out the product of the solvent thermal reaction, washing using ethanol, washing using deionized water, then drying to obtain fluorine-doped titanium dioxide/graphene composite material, and (iv) mixing uniformly the fluorine-doped titanium dioxide/graphene composite material and urea, and carrying out high temperature heat treatment to obtain final product; and (2) use of photocatalyst in reduction of chromium-containing wastewater, comprising (a) adding fluorine-nitrogen co-doped titanium dioxide/graphene composite material into waste water containing hexavalent chromium, (b) adding the waste water containing hexavalent chromium obtained in step (a) into a glass container, sealing, where the initial concentration of the waste water containing hexavalent chromium is taken as X, (c) placing the glass container obtained in step (b) into a camera obscura of photo-catalytic reactor, (d) stirring, opening xenon lamp, subjecting the solid-liquid mixture obtained in the step (c) to photocatalysis by irradiating under the xenon lamp, (e) extracting waste water containing hexavalent chromium obtained in step (d), and filtering, (f) taking clear solution, then determining hexavalent chromium concentration by ultraviolet spectrophotometry and taken as yttrium, and (g) calculating the photocatalytic removal rate by using an equation 1-(Y/X)x 100%.