The role of the reactive oxygen species and the influence of KBiO3 synthesis method in the photodegradation of methylene blue and ciprofloxacin

Abstract

KBiO3 was synthesized by three methods: chemical substitution, hydrothermal and sonochemical. All reaction products were analyzed by X-ray powder diffraction and reveal that KBiO3 presents a cubic structure. The morphology of each sample was analyzed with scanning electron microscopy (SEM), and the micrographs show particles with cube-like (chemical substitution), spheres-like (sonochemical) and flakes-like (hydrothermal) shape. HR-TEM technique was used to confirm the crystal structure and to determine the particle size of the samples, also it was used to corroborate the morphology. The photocatalytic activity of KBiO3 was evaluated on the reactions of the degradation of methylene blue (MB) and Ciprofloxacin (CPFX). An almost 100% discoloration of MB was reached at 120 min with KBiO3 obtained by the sonochemical method and a 67% degradation of CPFX was obtained by KBiO3 synthesized by the hydrothermal method. These results were associated with the catalyst morphology and organic adsorption on the surface of the catalyst. With the aim for a further understanding of the photocatalytic degradation of MB and CPFX, scavengers such as benzoquinone, isopropanol, and catalase were added to the photocatalytic reaction in order to identify the reactive oxygen species (ROS) involved. It has been found that hydrogen peroxide (H2O2) was the primary oxidizing species for the degradation of MB; meanwhile in the case of the oxidation of CPFX occurred by the presence of the superoxide radical (O 2 −· ).