Controlled synthesis of palygorskite/Bi5O7I hybrid microspheres with high efficient photodegradation of antibiotics

Abstract

Step-scheme (S-scheme) heterojunction is novel developed and has been demonstrated to be an efficient strategy to boost charge separation for the semiconductors with staggered band structure. Herein, 1D protonated palygorskite (denoted as Pal) nanofibers were introduced into Bi5O7I (denoted as BOI) nanosheets to fabricate 1D-2D Pal/BOI microspheres via a facile coprecipitation and calcination route. Series of characterization methods were employed to explore the structural composition, morphology and optical properties. The as-obtained 20 % Pal/BOI composite microspheres exhibited superior photocatalytic performance in the degradation of tetracycline hydrochloride (TCH) and ciprofloxacin (CIP) under simulated sunlight irradiation, which is 2.7 and 2.6 times higher than that of pristine Bi5O7I, respectively. In addition, photoelectrochemical characterizations were adopted to unveil the photocatalytic mechanism. The results demonstrated that the tight contact interface, hierarchical structure, improved optical response capbility and S-scheme heterojunction could efficiently accelerate spatial charge separation and migration, thus improving the photocatalytic activity. What’s more, the palygorskite played a vital role in the system to enlarge specific surface area, accelerate the charge separation and shorten charge transfer path under solar light irradiation. Such heterogeneous photocatalyst design strategy between bismuth-rich bismuth oxyhalides and natural clay might provide new insights for treating pharmaceutical wastewater.