Photocatalytic degradation and mineralization of dye pollutants from wastewater under visible light using synthetic CuO-VO2/TiO2 nanotubes/nanosheets

Abstract

CuO-VO 2 /TiO 2 as a new nanocomposite was synthesized through hydrothermal method and identified by various spectroscopic techniques including X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HR-TEM), energy dispersive X-ray analysis (EDX), UV-visible, differential reflectance spectroscopy (DRS), and Mott-Schottky. The presence of nanotubes/nanosheets in the synthesized nanocomposite was confirmed by HR-TEM. The anatase and rutile crystalline forms of TiO 2 were detected by Raman spectroscopy and X-ray diffraction (XRD). XPS analysis confirmed the presence of CuO and VO 2 in the nanocomposite. The surface area and the band-gap energy of the nanocomposite were determined via N 2 adsorption-desorption analysis and DRS. The presence of a p-n junction between TiO 2 (n-type) and CuO/VO 2 (p-type) was confirmed by the Mott-Schottky analysis. The photocatalytic activity of the nanocomposite against methylene blue (MB), methyl orange (MO), and cango red (CR) was studied under visible-light irradiation. The times of degradation for the decomposition of the dyes were 10-25 min. The rate constants of degradation for MB, MO, and CR were calculated as 0.34, 0.090, and 0.155 min -1 , respectively. The catalyst was recovered four times. In addition, the mineralization of the dyes was investigated by chemical oxygen demand (COD). The reaction was performed in the presence of different radical scavengers, and the ÁOH was found to be the predominantly active species in the photodegradation of the dyes.