Comparative study of ZnO photocatalyst samples prepared by different methods

Three different ways of preparation: activation (ZA), precipitation method using two different ingredients (ZP, ZD) were used to obtain nanosize ZnO powders. The photocatalytic activity was tested in the reaction of oxidative discoloration of diazo dye solution. The ZnO nanoparticle powders were obtained and characterized by XRD, IRS, TG - DTA, XPS and BET methods. The XRD analysis of ZnO photocatalysts showed presence of wurtzite ZnO phase, while IRS proves the formation of Zn-O bonds. The specific surface area of the ZnO sample, obtained by the activation method, was higher, compared to the other samples. The photocatalytic properties of the samples were tested in the reaction of oxidative degradation of Reactive Black 5 azo dye in solution. All the three photocatalysts showed high effectiveness in the dye degradation. The best photocatalyst is the activated ZnO powder, prepared by an original patented method. The highest rate constant of degradation of Reactive Black 5 model contaminant is on the ZA sample (33.8 x 10(-3) min(-1)).