Solar light-facilitated oxytetracycline removal from the aqueous phase utilizing a H2O2/ZnWO4/CaO catalytic system

Abstract

A CaO-supported ZnWO4 nanocomposite (ZnWO4/CaO) was successfully synthesized using a novel hydrothermal method and was characterized by scanning electron microscopy (SEM), tunnelling electron microscopy (TEM), X-ray diffraction (XRD), electron diffraction X-ray (EDX), Fourier transform infrared spectroscopy (FTIR) and UV–visible (UV–vis) spectral analysis. The ZnWO4/CaO composites exhibited rod-like morphologies with variable lengths from 45 nm to 147 nm and diameters from 26 nm to 36 nm. The catalytic efficiency of the synthesized ZnWO4/CaO composites was displayed for the photodegradation of oxytetracycline (OTC) antibiotic from the aqueous phase. The synergistic degradation of OTC was investigated in the presence of H2O2 and ZnWO4/CaO. The rate of photodegradation followed pseudo-first-order kinetics. The antibiotic removal was strongly influenced by the catalyst loading, H2O2 concentration, pH and OTC concentration. Using a solar/H2O2/ZnWO4/CaO catalytic system, 85% COD removal was attained for OTC degradation in 210 min. The oxidative degradation occurred through hydroxyl radicals. The prepared nanocomposites possessed high recyclability and were easily separated from the aqueous solution by a simple sedimentation process.

Keywords

• Supported-ZnWO4
• H2O2
• Enhanced-photocatalysis
• Antibiotic removal
• Kinetics