DEGRADATION OF OXYTETRACYCLINE VIA PHOTO-FENTON PROCESS AFTER ADSORPTION ON NATURAL AND IRON-MODIFIED MONTMORILLONITE CLAYS

BRACCO, ESTEFANÍA; MARCO BROWN, J.L.; BUTLER, MATÍAS; CANDAL, ROBERTO

Ciudad de México

Congreso; 7th Latin-American Congress of Photocatalysis, Photochemistry and Photobiology; 2021

Engineering Institute at the Universidad Nacional Autónoma de México

In this work, combined adsorption/oxidation treatments were developed aiming to the rapid removal of organic pollutants from water and their subsequent degradation. Bentonite clays were employed as adsorbents, photo-Fenton reactions as oxidation processes and oxytetracycline (OTC) as the model emerging pollutant.The natural clay montmorillonite (MMT) was used as the precursor for the synthesis of iron modified montmorillonite (Fe-MMT). Equilibrium studies were performed to determine the adsorption mechanism of OTC on MMT and Fe-MMT and the maxima adsorption capacity of both materials at different pH values. Afterwards, OTC degradation was analyzed in four different systems, i.e. homogeneous phase, heterogeneous phase with MMT and Fe-MMT at pH 3 and with Fe-MMT at pH 7. Experiments in heterogeneous phase were assayed over suspensions of the clay subject to a previous adsorption step with OTC. Three experiments were carried out for each system: photolysis and photo-Fenton with UVA light, Fenton in the dark. Photo-Fenton blank experiments (without adsorbed OTC) were also made for the heterogeneous systems, in order to assess the contribution of the bentonites.Temporal evolution of total organic carbon (TOC) and hydrogen peroxide in solution was measured whereas OTC and intermediates in solution were studied by means of HPLC-MS. Homogeneous and heterogeneous experiments with the natural clay showed little mineralization although many degradation intermediates could be detected. On the contrary, heterogeneous experiments with Fe-MMT at pH 3 and 7 showed the desorption of OTC from the clay after 30 minutes of treatment, and further mineralization was observed with less intermediates detected.