Modified ilmenite as catalyst for CWPO-Photoassisted process under LED light

Abstract

The influence of the iron chemical nature contained in ilmenite (FeTiO3) upon the activity and stability of these materials as catalysts for CWPO-Photoassisted process under LED light (λ: 405 nm) were evaluated. Raw ilmenite was treated with H2 within the range 25–1000 °C in order to partially reduce iron oxides to Fe(0). The catalysts were characterized by N2 adsorption/desorption, TXRF, XRD and XPS analysis. The co-presence of different iron species (Fe(0), Fe(II) and Fe(III)) along with the light effect over material surface, led to an increase of H2O2 decomposition rate into HO[rad] and, therefore, a higher oxidation rate. In all case, after total H2O2 depletion, a complete phenol degradation and a 95% TOC conversion was reached in batch at pH0 = 3 and 50 °C using the stoichiometric H2O2 dose (14 mol H2O2/mol phenol) and 10 W m−2 LED light. Long-term continuous experiments were carried out to assess the stability and the lifetime of the catalyst. The higher reduction degree led to a higher organic matter mineralization but also to a higher leaching of active phase around 3% of the total iron amount in ilmenite. Nevertheless, catalyst deactivation seems to be related to the oxidation of iron on the catalyst surface.