Increased Degradation Capacity of Methylene Blue Dye Using Mg-doped ZnO Nanoparticles Decorated by Ag0 Nanoparticles

Photocatalytic activity has been widely used for the treatment of organic effluents, mainly those generated by textile industries. Zinc oxide is widely investigated for this application due to its low cost, non-toxicity and high efficiency. In this work, the photocatalytic properties of ZnO:xMg (x = 1 mol.%, 2 mol.%, 4 mol.% and 8 mol.%) decorated with Ag0 were investigated against methylene blue dye (MB). Initially, the nanostructures of ZnO:xMg were produced by the microwave-assisted hydrothermal method, and the nanoparticles of Ag0 were deposited by ultraviolet (UV) photoreduction. The structural characteristics of the powders were determined by x-ray diffraction, the morphologies were investigated by field emission scanning electron microscopy (FE-SEM) and the optical absorbance of the photocatalysts was characterized by the diffuse reflectance spectra [UV–visible light (UV–Vis)]. The photocatalytic properties were estimated by degradation of MB, and the capacity for reuse of the powders was estimated by application in three consecutive cycles. Undoped ZnO powders reduced 84% of MB concentration, while the ZnO:8%Mg sample reduced 97% of it, indicating that doping with Mg2+ is efficient in increasing the degradation capacity of ZnO against MB degradation. The deposition of metallic silver nanoparticles on the ZnO surface considerably increases the photocatalytic efficiency, in which after 18 min, the 8%Mg sample completely degraded the MB. The reuse tests showed that the powders maintain their photocatalytic activity after three cycles and can be used for such application without generating secondary residues.