Nanostructured CeO2 as catalysts for different AOPs based in the application of ozone and simulated solar radiation

Two CeO2 catalysts with different morphology (nanocubes and nanorods) were synthetized by hydrothermal treatment, characterized by TEM, XRD, N-2 adsorption-desorption isotherms, XPS and DR-UV-vis spectroscopy and examined for different AOPs (photocatalytic oxidation, catalytic and photocatalytic ozonation) using simulated solar radiation (lambda > 300 nm) or visible radiation (lambda > 390 nm) from a Xe lamp, and DEET as target compound. Neither significant DEET removal nor mineralization was achieved by solar photocatalysis and the catalysts did not show an important beneficial effect during catalytic ozonation. The best results were obtained in photocatalytic ozonation process being nanorods more active under visible radiation according to its lower band gap energy whereas nanocubes presented the highest intrinsic photocatalytic activity under visible and solar radiation. Photocatalytic ozonation of DEET with CeO2 catalysts proceeds through a complex reaction mechanism that involves at least ozone-direct reaction that triggers a radical chain mechanism, indirect ozone reactions, ozone photolytic and photocatalytic decomposition and hydrogen peroxide formation-decomposition. (C) 2016 Elsevier B.V. All rights reserved.