Preparation and characterization of ZrO2-Cr2O3 nanocomposite as a p-n heterojunction by a facile sol-gel method: A kinetic investigation on the removal of p-nitrophenol dye from aqueous media

A series of ZrO2-Cr2O3 nanoparticles, being able to efficiently remove the organic dye of p-nitrophenol in water media, were synthesized and characterized. The as-synthesized nanocomposites were fully characterized utilizing some common characterization techniques like X-ray diffraction (XRD), scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDX), transmission electron microscope (TEM) and infrared spectroscopy (FT-IR). The XRD results confirmed the presence of tetragonal phase of the ZrO2 together with the hexagonal Cr2O3 when the samples were calcined at 600 degrees C. However, at calcination temperature of 900 degrees C, in addition to tetragonal phase, the monoclinic phase is present for ZrO2 while the rhombohedral phase is the only phase for the Cr2O3 dopant. In order to evaluate the photocatalytic efficiencies of the new compounds, a diluted solution of the p-nitrophenol (10 ppm) was applied. During the 100 min from the starting point of the photodegradation process, the UV-Vis spectroscopy was used to follow the process through the maximum absorbance of p-nitrophenol (320 nm). By using the kinetic first order equation for the resulting UV-Vis spectra, the photodegradation rates were calculated for all the samples. Finally, it was proved that the molar percentage of the dopant in zirconia substrate and calcination temperature both are determining factors in rates of the photodegradation process. (C) 2019 Elsevier Ltd. All rights reserved.