Catalytic wet peroxide oxidation of cosmetic wastewaters with Fe-bearing catalysts

Catalysts based on Fe supported on γ-Al2O3 and active carbon (AC) have been prepared and tested for catalytic wet peroxide oxidation (CWPO) of cosmetic wastewaters. The catalysts were characterized by TXRF, XPS, XRD, SEM, elemental chemical analysis, Mössbauer spectroscopy and 77 K N2 adsorption–desorption. The catalytic performance was monitored in terms of COD, TOC and H2O2 conversions. The possible leaching of iron from the catalyst was also checked. The influence of the catalysts preparation conditions (calcination temperature and Fe content) as well as the operating temperature in the oxidation process has been studied with the purpose of optimization. Working at 85 °C with a Fe/γ-Al2O3 catalyst calcined at 300 °C and with 4% Fe content, a remarkable COD reduction (around 85%) has been reached. However, lower temperatures are sufficient to fulfill the locally allowable limit of COD for industrial wastewaters discharge into the municipal sewer system. A substantial improvement of biodegradability (BOD5/COD ratio) was observed. Thus, CWPO could be effectively applied whether as a treatment itself or as a pre-treatment addressed to improve subsequent biodegradability of these wastewaters. The Fe/γ-Al2O3 catalyst showed a reasonable stability, a relatively low decrease of activity (15%) being observed after three successive runs.