Degradation pathways of emerging contaminants using TiO2-activated carbon heterostructures in aqueous solution under simulated solar light

Abstract This work deals with the degradation of three emerging contaminants (acetaminophen, ibuprofen and antipyrine) in water under simulated solar light using different catalysts of TiO2/activated carbon heterostructures. The heterostructures, based on anatase phase, were successfully synthesized following three different methods (solvothermal, microwave-assisted and sol-gel), using lignin as carbon precursor. The sol-gel photocatalyst only yielded 50% conversion of acetaminophen and a low mineralization (15%), probably due to the higher crystal and particle sizes and lower surface area of this heterostructure, as a consequence of the higher temperature reached during the heat-treatment included in this synthesis route to achieve anatase crystallization. In contrast, the heterostructure prepared by the microwave-assisted procedure achieved complete conversion after 6 h of reaction. Regarding the contaminants, ibuprofen was the most easily removed, requiring 3 h for complete disappearance, while antipyrine showed the highest resistance to photodegradation, not being completely removed after 6 h. The photocatalytic performance was also evaluated for a mixture of these three pharmaceuticals at different initial pH. The fastest and highest mineralization (ca. 50 %) occurred around neutral pH. The study proposes the oxidation degradation pathways of the three pharmaceuticals under solar-simulated irradiation from the analysis of the reaction intermediates.