ZnSO4–TiO2 doped catalyst with higher activity in photocatalytic processes

This study presents the synthesis and activity of ZnSO4–TiO2 coated Raschig rings (RR). The activity of the Zn-doped catalyst (from now on Zn–TiO2/RR) was found to be higher than of the pure Degussa P25 TiO2 during the photodegradation of organic compounds. The most suitable doping level of TiO2 for Zn was 4 mol% noted as Zn (4% mol)–TiO2/RR during the degradation of azo-dye Orange II and of the transparent 2-propanol solutions. The degradation kinetics of the probe molecules was systematically investigated as a function of the catalyst make-up and some of the solution parameters. XPS measurements show Zn 2p3/2 peak positions for Zn–TiO2 sample in the range 1021.58–1022.00 eV. This energy range was observed to be lower than 1022.54 eV recorded for the reference ZnSO4 sample. This shift indicates that the Zn-atoms act as electron acceptors in the Zn-doped TiO2 and may be responsible for the higher catalytic activity observed for the Zn (4% mol)–TiO2/RR compared to the TiO2/RR photocatalyst during Orange II degradation. Insight is given onto the complex oxidation/reduction processes takes place at the interface of Zn–TiO2. The changes occurring in the Zn, TiO2 and S catalyst components are discussed as a function of the time of reaction. The Zn–TiO2 catalyst was characterized by elemental analysis (EA), transmission electron microscopy (TEM), energy dispersive spectroscopy (EDS), confocal microscopy, X-ray photoelectron microscopy (XPS) and X-ray diffraction (XRD).