Photolysis and photocatalysis of the non-steroidal anti-inflammatory drug Nimesulide under simulated solar irradiation: Kinetic studies, transformation products and toxicity assessment
Koltsakidou, Î‘; Katsiloulis, C.; Î•vgenidou, Î•; Lambropoulou, D.A.
Science of the Total Environment 689: 245-257
ISSN/ISBN: 1879-1026 PMID: 31271990 DOI: 10.1016/j.scitotenv.2019.06.172
In this study, the degradation of Nimesulide (NIM), a non-steroidal anti-inflammatory drug, using photolysis, heterogeneous (TiO2 in dispersion) and homogeneous (photo-Fenton reactant) photocatalysis, under simulated solar light (SSL) radiation, was investigated. Various parameters affecting the degradation rate of the target compound during the applied processes were optimized. The efficiency of all treatments used (direct photolysis; TiÎŸ2/SSL; TiÎŸ2/Î—2ÎŸ2/SSL; TiÎŸ2/S2ÎŸ82-/SSL; Fe3+/H2O2/SSL; Fe3+/S2O82-/SSL and [Fe(C2O4)3]3-/H2O2/SSL) was evaluated by means of initial reaction rate and mineralization. Moreover, the generated transformation products (TPs) by each basic process (photolysis; TiÎŸ2/SSL and Fe3+/H2O2/SSL) were identified, using liquid chromatography coupled to high resolution mass spectrometry, and their formation kinetic profiles were given. The main transformation routes of NIM were hydroxylation and fragmentation, for all three treatments applied. Finally, toxicity measurements were conducted using Microtox bioassay in order to evaluate the potential risk of NIM and its TPs to aqueous organisms. Although, the acute toxicity increased during the first stages of treatment the final outcome lead to very low toxicity levels even within 60â€¯min of TiO2/SSL treatment. Concluding, the obtained results suggest that the photocatalytic degradation of NIM can lead to its complete elimination and simultaneously to the detoxification of the solution.