Degradation of selected agricultural pesticides by photosensitized and Fenton-like processes

EDUARDO A. GATICA; JOSÉ NATERA; WALTER A. MASSAD

Anales de la Asociación de Química Argentina

AQA

Lugar: Buenos Aires; Año: 2020

2545-8655

This paper presents the study of the degradation of pollutants (Q) through the use of sustainable methods. Different herbicides and an antiparasitic belonging to different chemical families were investigated: Isoxaflutole (IXF), Oxyfluorfen (OXF) and Niclosamide (NSD, antiparasitic). Photodegradation was performed using direct and sensitized photolysis in the presence of Riboflavin (Rf). Rf, normally present in natural waters, is a photosensitizer that absorbs in the visible region of the spectrum and that, in the presence of visible radiation, generates reactive oxygen species such as singlet oxygen and superoxide radical anion. In addition, the degradation of these compounds by Fenton and photo-Fenton processes was studied. These processes are characterized by the generation of the hydroxyl radical (HO●) in aqueous solution, which is a highly oxidizing spice capable of mineralizing organic compounds. Using Rf as a photosensitizer the herbicides do not degrade, but NSD does. IXF, OXF and NSD were degraded by the HO● generated by photo-Fenton and the photoproducts generated during the photolysis were detected by HPLC-UV-Vis. In the case of IXF, the possible chemical structures of the photoproducts were determined using HPLC-MS / MS. The general results suggest that natural photodegradation, using visible radiation and photosensitization, is a possible degradative pathway for NSD, but not for herbicides. The rest of the compounds studied are degraded by direct photoirradiation, with a low quantum yield value and by Photo-Fenton with a good degradation rate.