Photocatalytic removal of acid blue from aqueous solutions by G/ZnO composites under visible light radiation

Azo dyes are widely used in industrial processes and the effluents from these industries contain remaining dyes that affect water quality and become a threat to public health, since azo dyes or their metabolites (e.g., aromatic amines) are highly toxic and potentially carcinogenic. The photocatalytic oxidation is a promising method for decomposition of organic dyes. In this paper, in order to enhance the photocatalytic activity of ZnO, graphene (G) was loaded on ZnO to modify. The G/ZnO composites were prepared by an impregnation method and the photocatalytic activity of composites was evaluated by photodegradation of acid blue under visible light irradiation. The removal of acid blue was carried out in a glass beaker containing 100 mL acid blue aqueous (15 ppm) and 300 ppm of photocatalyst. The acid blue concentration in the solution was determined using a UV-Visible spectrophotometer. The degree of decolorization of acid blue solution by ZnO and G/ZnO composites with different mass ratio of graphene is shown in Graphical Abstract. It is clear that all of the photocatalysts modified by graphene exhibited higher photocatalytic activity than those of pure ZnO and G(10%wt)/ZnO showed the highest activity (photodegradation 55%). The introduction of graphene could increase light absorption, accelerate the absorption of the dye and inhibit the recombination of photoinduced electron–hole pairs and hence, improve the photocatalytic efficiency.