Preparation of 3D BiOI microspheres for highly efficient visible light-induced photocatalytic degradation of tetracycline

Abstract

Semiconductor photocatalysts for pharmaceutical antibiotic wastewater treatment are subject to increasing attention. Herein, BiOI photocatalysts were prepared by a one-step solvothermal method using ethylene glycol (EG) as solvent and their tetracycline (TC) degradation activities under visible light irradiation were compared. Catalyst preparation temperature, time, and pH conditions were optimized, and the catalyst physicochemical properties were characterized. Solution pH was found to have a significant effect on the morphology, electronic structure, and surface exposed facet of BiOI. Catalysts synthesized in the absence of NaOH presented more regular 3D flower-like microspheres, possessed larger surface area, were composed of many small nanosheets predominantly exposing the (001) facet, and showed better photogenerated electron-hole pairs separation efficiency. The optimized BiOI presents superior TC degradation efficiency (73.6%) under visible light irradiation, and recycling experiments indicated that the catalysts have good stability and reusability. The active species were investigated by free radical trapping experiments, revealing that •O2− plays a major role in the photodegradation process. Possible TC degradation pathways are proposed according to mass spectrometry analysis.