Photodegradation of Ciprofloxacin-Zinc Complexes Produced at the Interface of ZnO and Cu-Doped ZnO Crystals
Aryane Tofanello, Elisângela Belleti, Adrianne M. M. Brito, Iseli L. Nantes
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.