Degradation of dipyrone and its main intermediates by solar AOPs: Identification of intermediate products and toxicity assessment

In this study, two solar advanced oxidation processes, heterogeneous photocatalysis with TiO2 and homogeneous photocatalysis by photo-Fenton, carried out at pilot-plant scale using compound parabolic collectors are proposed for the elimination of dipyrone and its metabolites in water. The two treatments are compared on the basis of their kinetics (parent compound and TOC), formation of degradation products (as determined by ionic chromatography, GC/MS and LC/TOF-MS), and toxicity (as evaluated by Vibrio fischeri bacteria). Photo-Fenton was more efficient than TiO2, but without any relevant difference between the degradation products formed or toxicity. A degradation pathway is proposed, carboxylic acids being the main intermediates prior to mineralisation. Decrease in toxicity during treatment is also shown.