Synthesis, characterization and application of GO-ZnO photocatalyst for the enhanced degradation of azole fungicides: Performance, activation of oxidants, transformation products and toxicity

The aim of this research report was the synthesis, characterization and application of a GO-ZnO photocatalyst for the enhanced degradation of two azole fungicides, fluconazole and voriconazole. The nanocomposite was prepared using a hydrothermal method, whereas its characterization included the utilization of XRD, SEM and FTIR. Regarding the photocatalytic activity, experiments revealed that GO-ZnO was highly effective against fluconazole, achieving 79.7 % removal at catalyst dosage of 100 mg/L and treatment time of 60 min. Additionally, the experiments proved a positive correlation between the catalyst’s concentration and removal efficiencies, while the investigation of pH effect showed that the original pH value of the deionized water constituted the optimal condition for the degradation. Moreover, the activation of commonly used oxidants, namely H 2 O 2 and S 2 O 8 2- , was also investigated. The findings showed that addition of H 2 O 2 didn’t influence the removal capacity of the nanocomposite, while the addition of S 2 O 8 2- caused an enhanced decomposition. Finally, mineralization of the mixture of the two antifungals indicated that a significant number of transformation products were produced during the treatment. These data prompted further investigation of the subject in order to elucidate their chemical structures and toxicity. A total of 12 photodegradation products were identified using HRMS analysis. • A GO-ZnO material with an enhanced photocatalytic performance was developed using a hydrothermal method • Photocatalytic treatment achieved 79 % and 81.1 % removal of fluconazole and voriconazole within 60 min • The addition of persulfate ions in the suspension caused an enhanced degradation of fluconazole • Regarding transformation products, a total number of 12 TPs were identified