Photocatalytic degradation of ciprofloxacin using semiconductor derived from heterostructured ZIF-8-based materials

Abstract

The combination of zeolitic imidazolates framework (ZIF) with porous solids with an analogous structure may represent a new class of heterostructured materials with improved properties for application in advanced oxidative processes. In this work, the in situ synthesis of ZIF-8 was carried out in the presence of the sodalite zeolite (SOD) to obtain the heterostructured ZIF-8/SOD. The thermal treatment of the previously formed heterostructure made it possible to obtain a surface enriched with ZnO from the ZIF-8 fraction, with the formation of the ZnO/SOD heterostructure. The formation of ZIF-8 and its derivative ZnO in sodalite was confirmed using different physicochemical techniques, such as PXRD, FTIR, 13C, 27Al and 29Si NMR, SEM, EDS, DRS-UV, TOC, PL, EIS and photocurrent measurements. Specific surface and porosity studies revealed that both heterostructures are composed of a wide range of pore sizes and distributions. Such materials were used as photocatalysts in the degradation of ciprofloxacin antibiotic drug. The ZIF-8/SOD heterostructure showed good photocatalytic capacity; however, superior performance was revealed for that thermally treated material, showing a degradation rate of approximately 98% in 120 min of the assay. Besides pH studies, PL and electrochemical assays indicated the efficient charge separation, while tests to inhibit the reactive species in the photocatalytic process suggested that the contaminant removal process involved a combined effect of both adsorption and photocatalysis, where the superoxide radical is the main specie responsible for the degradation of ciprofloxacin.