Degradation of the emerging contaminant ibuprofen in water by photo-Fenton

In this study the degradation of the worldwide Non-Steroidal Anti-Inflammatory Drug (NSAID) ibuprofen (IBP) by photo-Fenton reaction by use of solar artificial irradiation was carried out. Non-photocatalytic experiments (complex formation, photolysis and UV/Vis-H₂O₂ oxidation) were executed to evaluate the isolated effects and additional differentiated degradation pathways of IBP. The solar photolysis cleavage of H₂O₂ generates hydroxylated-IBP byproducts without mineralization. Fenton reaction, however promotes hydroxylation with a 10% contamination in form of a mineralization. In contrast photo-Fenton in addition promotes the decarboxylation of IBP and its total depletion is observed. In absence of H₂O₂ a decrease of IBP was observed in the Fe(II)/UV-Vis process due to the complex formation between iron and the IBP-carboxylic moiety. The degradation pathway can be described as an interconnected and successive principal decarboxylation and hydroxylation steps. TOC depletion of 40% was observed in photo-Fenton degradation. The iron-IBP binding was the key-point of the decarboxylation pathway. Both decarboxylation and hydroxylation mechanisms, as individual or parallel process are responsible for IBP removal in Fenton and photo-Fenton systems. An increase in the biodegradability of the final effluent after photo-Fenton treatment was observed. Final BOD₅ of 25 mg L⁻¹ was reached in contrast to the initial BOD₅ shown by the untreated IBP solution (BOD₅ < 1 mg L⁻¹). The increase in the biodegradability of the photo-Fenton degradation byproducts opens the possibility for a complete remediation with a final post-biological treatment.