Catalytic enrichment of plasma with hydroxyl radicals in aqueous phase at room temperature

Different iron oxide catalysts supported on mesoporous silica were prepared by several techniques including assembly of pre-synthesized nanoparticles, coprecipitation in the presence of the support or impregnation. Characterization showed that iron oxide nanoparticles were dispersed either at the surface of the SiO2 material or within the pores when prepared by dry impregnation. The catalytic performance of these materials for Fenton chemistry was evaluated through kinetic tests in the presence of coumarin as a radical trap for the quantification of the HO˙ radicals produced. The first tests concerned the production of HO˙ radicals from H2O2 by a Fenton-like reaction. The results show that catalysts prepared by dry impregnation in an ethanolic solution show the highest activity toward the production of HO˙ radicals. These catalysts were also engaged in a reaction without external H2O2 using a cold atmospheric pressure plasma jet treatment with the successful purpose of increasing the production of HO˙ radicals in aqueous solution at room temperature and near-neutral pH. Our best catalysts outperformed others reported in the literature in reactions carried out with soluble species or at acidic pH. Moreover, a synergetic effect between the heterogeneous catalyst and the plasma for HO˙ radical production was highlighted. These radicals could be easily used for biomedical or wastewater treatment applications.