Facile construction of novel direct solid-state Z-scheme AgI/BiOBr photocatalysts for highly effective removal of ciprofloxacin under visible light exposure: Mineralization efficiency and mechanisms.

A novel Z-scheme AgI/BiOBr hybrid photocatalyst was successfully synthesized by a solvothermal-precipitation method, and its photocatalytic activity was evaluated by the degradation of ciprofloxacin (CIP, a typical antibiotic). The crystallization, morphology, photo-response, surface structure and electrochemical properties of the as-obtained photocatalyst were characterized by XRD, XPS, SEM, TEM, BET, UV-Vis absorption spectroscopy and photoluminescence spectra (PL) measurements, respectively. The optimized AgI(20 wt%)/BiOBr composite exhibited a remarkable photocatalytic activity and a rapid degradation ability for CIP with a removal efficiency of 90.9% in 1 h, which was considerably better than those of pure BiOBr (58.6%) and pure AgI (4.6%) alone as well as their simple mixtures (31.4%) under the same conditions, suggesting an synergistic effect in the hybrid materials. Meanwhile, CIP was efficiently mineralized, as revealed by a total organic carbon (TOC) removal efficiency of ca. 90% within 2 h, which was further confirmed by the 3D EEMs measurement. The reactive species trapping and electron spin resonance (ESR) experiments demonstrated that O2-, h+ and OH all participated in the CIP photodegradation process. The photocatalytic mechanism of AgI/BiOBr composites could be rationally explained by considering the Z-scheme structure, resulting in the higher redox potential and more efficient separation of charge carriers. Moreover, the wider photo-response range induced by the photosensitization of AgI also contributed to the superior photocatalytic activity of the hybrid materials. This work reports a novel method for the facile preparation of Z-scheme AgI/BiOBr hybrid photocatalyst and provides an effective methodology for the mineralization of CIP.