Photocatalytic performance of TiO₂, CeO₂, ZnO and TiO₂-CeO₂-ZnO in the course of methyl orange dye degradation

Commercial TiO₂, CeO₂, ZnO single oxides and a mixture of them at a mass ratio of 1:1:1 were mechanochemically treated (MCT). CeO₂ was the best commercial sample prior to MCT because of its narrow band gap and high oxygen storage capacity. The powder X-ray diffraction analysis confirmed the existence of TiO₂, CeO₂ and ZnO phases in all MCT samples studied. The determined average crystallite size was in the range of 18 - 19 nm for the single component photocatalysts and of 10 - 15 nm for the ternary system. Following 30 min dark period the adsorption capacity of TiO₂-CeO₂-ZnO-MCT (0.263 mg/g) was the highest among those of the other materials. The behavior of the commercial and MCT photocatalytic materials (TiO₂, CeO₂, ZnO and TiO₂-CeO₂-ZnO) was studied in the course of photocatalytic oxidative degradation of Methyl Orange dye treated as a pollutant. The results obtained in an aqueous solution under UV irradiation showed that ZnO-MCT sample provided the highest photocatalytic effect (81 % conversion) when compared to that of the other MCT materials. The degree of MO dye degradation decreased in the line: CeO₂ (87 %) > ZnO-MCT (81 %) > ZnO (76 %) > CeO₂-MCT (67 %) > TiO₂-CeO₂-ZnO-MCT (63 %) > TiO₂ (61 %) > TiO2-MCT (49 %). Keywords: Methyl Orange, dye, TiO₂, CeO₂, ZnO.