Synthesis, characterization and efficient photocatalytic activity of novel Ca/ZnO-Al2O3 nanomaterial

Abstract

In this paper Ca/ZnO-Al2O heterojunction photocatalysts was prepared in two steps. First, Zn-Al-CO3 layered double hydroxides (LDH) precursor was synthesized by co-precipitation method. Second, Ca at various content (1, 3 and 5 wt%) was incorporated on LDH structure using solid state reaction at 500 °C. Samples were characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM) coupled with energy dispersive X-ray analysis (EDX) and UV–vis diffuse reflectance spectroscopy (UV–vis DRS). The photocatalytic activity of the catalysts was evaluated in the degradation of caffeine as a model of pharmaceutical pollutants in aqueous solutions under UV irradiation. The Ca-doped ZnO-Al2O3 materials showed significantly higher photocatalytic activity compared to undoped, pure ZnO and standard Degussa P-25 titanium dioxide. This behavior was attributed to increased adsorption capacity, crystallinity of the catalysts and surface morphology. The maximum degradation rate (98.5 ± 0.5%) was obtained in 70 min by 5%Ca-ZnO-Al2O3 photocatalyst. Furthermore, the effect of different parameters such as irradiation time, photocatalyst amount, caffeine concentration, initial pH and reuse on the resulting photocatalytic activity was investigated. The photocatalytic degradation of caffeine was increased with an increase in the Ca-loaded amounts. This work demonstrates that the prepared Ca doped ZnO-Al2O3 nanoparticles are promising material for the photocatalytic degradation of pharmaceuticals pollutants.