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

- Raw ilmenite was treated to evaluate the influence of iron oxidation state.
- The co-presence of different iron oxidation states led to a faster mineralization.
- Phenol total conversion and 95% of TOC removal was reached in all cases.
- Long-term experiments confirmed the stability of these materials.

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 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.

93