Photodegradation of Ciprofloxacin-Zinc Complexes Produced at the Interface of ZnO and Cu-Doped ZnO Crystals

Abstract

Ciprofloxacin hydrochloride (CIPRO) is considered an emerging pollutant in aquatic environments with the capacity to disseminate antibiotic resistance. Considering the pro-oxidant potential of ZnO and Cu-doped ZnO (Cu-ZnO) wurtzite crystals, the potential Ciprofloxacin photodegradation by these materials was investigated. CIPRO titration with ZnO and Cu-ZnO promoted the formation of zinc complexes and ~4% antibiotic adsorption. The carboxylic groups of CIPRO can complex Zn2+ by promoting the nanoetching of ZnO and Cu-ZnO crystallite surfaces. The alkaline interfaces provided by ZnO create a microenvironment favorable for Zn2+ chelation by CIPRO carboxylates. The photodegradation degree was similar for CIPRO and CIPRO-Zn under UV light, as revealed by UV-visible spectroscopy and FTIR. Therefore, the ZnO and Cu-ZnO crystals contributed to the formation of CIPRO-Zn rather than the photo-oxidative degradation of the antibiotic. Considering that CIPRO-Zn chelates disfavor bacterial selection for resistance, the treatment of CIPRO-contaminated effluents with ZnO and Cu-ZnO can facilitate desirable metal chelation without impairing photodegradation.