Photocatalytic Systems Based on ZnO Produced by Supercritical Antisolvent for Ceftriaxone Degradation

Emerging contaminants are a significant issue in the environment. Photocatalysis is proposed as a solution for the degradation of pollutants contained in wastewater. In this work, ZnO-based photocatalysts have been produced and tested for the photocatalytic degradation of an antibiotic; specifically, ceftriaxone has been used as a model contaminant. Moreover, there is particular interest in combining small-size ZnO particles and beta-cyclodextrin (beta-CD), creating a hybrid photocatalyst. Zinc acetate (ZnAc) (subsequently calcinated into ZnO) and beta-CD particles with a mean diameter of 0.086 and 0.38 mu m, respectively, were obtained using the supercritical antisolvent process (SAS). The produced photocatalysts include combinations of commercial and micronized particles of ZnO and beta-CD and commercial and micronized ZnO. All the samples were characterized through UV-Vis diffuse reflectance spectroscopy (DRS), and the band gap values were calculated. Raman and FT-IR measurements confirmed the presence of ZnO and the existence of functional groups due to the beta-cyclodextrin and ZnO combination in the hybrid photocatalysts. Wide-angle Xray diffraction patterns proved that wurtzite is the main crystalline phase for all hybrid photocatalytic systems. In the photocatalytic degradation tests, it was observed that all the photocatalytic systems exhibited 100% removal efficiency within a few minutes. However, the commercial ZnO/micronized beta-CD hybrid system is the photocatalyst that shows the best performance; in fact, when using this hybrid system, ceftriaxone was entirely degraded in 1 min.