Innovative composites based on an amorphous-carbon matrix containing a second phase ZnO oxide and/or highly dispersed Zn metallic were synthesized via a modified Pechini route, in which a partial pyrolysis method was reached. Studies of adsorption in the dark and the photocatalytic activity for the cationic azo-dye, basic blue 41, and degradation were carried out. X-ray diffraction patterns for the carbon matrix and its composite with Zn show characteristics of the amorphous carbon. The infrared in the mid region of the composite prepared with ZnO and Zn exhibit vibrational bands related to bonds zinc oxide. The surface pH of the material is the main factor responsible for the adsorption of the azo-dye, but the contribution of mesopores favored the diffusion of molecules from the bulk of solution to the pore framework. Esters-like functional groups on the surface of carbons hinder the adsorption of the azo-dye. When Zn is embedded within amorphous carbon the photocatalytic activity of the composites showed up to 2.4 higher than neat ZnO. The enhancement in the photocatalytic activity and stability of C/ZnO/Zn and C/Zn composites is discussed in terms of a protector effect by the carbon layers inserted in composites. Carbon layers are responsible to inhibit the lixiviation of ZnO particles along irradiation.
Keywords: amorphous carbon; basic blue 41; carbon/ZnO composites; lixiviation; photocatalytic degradation; solar irradiation.