Removal of antifungal agents fluconazole and voriconazole in aquatic media by homogeneous and heterogeneous photocatalytic applications: Efficiency, optimization and transformation products
Pericles Parthenidis, Athanasia Faka, Nicolina Aristidou, Εleni Εvgenidou, Dimitra A. Lambropoulou
Abstract
This research details the photocatalytic degradation of fluconazole and voriconazole by UV/Fe 2+ /H 2 O 2 , UV/Fe 2+ /S 2 O 8 2− and TiO 2 -based processes, examining the effect of various operating parameters like the catalyst dosage, concentration of oxidants, the impact of UV-light and matrix. Moreover, the extend of mineralization and identification of the main transformation products were also investigated. Regarding heterogeneous photocatalysis, UV/TiO 2 process was able to eliminate completely the compounds within 60 min of treatment. Additionally, the combination of TiO 2 with exogenous oxidants (H 2 O 2 , S 2 O 8 2− ) significantly improved the photodegradation rates of the two compounds as reflected in the kinetic parameters. Regarding homogeneous photocatalysis, the experiments revealed that both Fe 2+ /H 2 O 2 and Fe 2+ /S 2 O 8 2− can succeed exceptional efficiencies when the catalytic reactions are being enhanced by a UV light. The optimization study included the investigation of the effect of initial concentration of ferrous ions (Fe 2+ ), the effect of the oxidants, the matrix effect and the influence of UV-light. Under optimum conditions ([Fe 2+ ] = 0.25 mg/L [H 2 O 2 ] = 2.9 mM, pH = 3) and treatment time of 60 min, the reduction percentages of fluconazole and voriconazole were 69.9 % and 96.52 % respectively. Considering decomposition in a real wastewater matrix, the results showed that higher treatment times are required while heterogenous photocatalysis appears to be more effective in voriconazole's removal. Furthermore, the main transformation products of the compounds were identified using LC-Orbitrap. The undertaking revealed that the degradation of the pollutants proceeded through hydroxylation, oxidation, dealkylation and defluorination. Finaly, TOC measurements showed that heterogenous photocatalysis exhibited higher efficiency in mineralizing both target antifungals. • Degradation of fluconazole and voriconazole was studied using TiO 2 -based and Fenton applications • The processes proved to be quite effective against the mixture of the pharmaceuticals • The effect of various parameters such as the concentration of catalyst, oxidants and UV-light was studied • Six photodegradation products were identified in UV/TiO 2 process