Iron Oxide and Metal Ferrite Nanocatalysts: Insights into the Generation of Free Radicals

GALLO-CORDOVA, ALVARO; N. NUÑEZ; C. DÍAZ-UFANO; B. CORRALES; J,G, OVEGERO; S. VEINTEMILLAS-VERDAGUER; R.D. ZYSLER; E. LIMA JR.; G.F. GOYA; E.L. WINKLER; M.P. MORALES

Granada

Congreso; International Conference on Magnetic Fluids 2023 - ICMF23; 2023

Universidad de Granada

Magnetic iron oxide nanoparticles (MNPs) are able to act as catalytic agents in Fenton and Haber-Weiss reactions. The peroxidase-like activity at the surface of the MNPs results in the decomposition of H2O2 into highly oxidative reactive oxygen species (ROS) such as hydroxyl (•OH) and hydroperoxyl radicals (•OOH) [1]. Depending on the MNPs nature, coating and oxidation state, it is possible to induce the generation of one or another free radical. In this work, ROS production with iron oxide (Fe3O4) and metal ferrite (MFe2O4, M= Co, Mn, Zn) nanoparticles was analyzed through electron paramagnetic resonance (EPR) and in the degradation process of acid orange 8 (AO8) as a model compound. Different sized MNPs (8 and 15 nm) were synthesized by a highly reproducible microwave-assisted procedure in polyol [2]. Selected samples underwent an oxidation treatment to form maghemite nanoparticles (γ-Fe2O3). As prepared samples were stable in aqueous suspensions thanks to polyol rests, while one was stabilized with citric acid (CA).EPR assays (Figure 1) proved that ROS production increases when decreasing particle size due to a larger surface area. The nature of the metal ferrite can increase the •OH or •OOH depending on the doped metal. For example, MnFe2O4 exhibited higher amount of •OOH than γ-Fe2O3, non-oxidized Fe3O4 showed the greatest concentration of •OH, and the presence of Zn reduced significantly ROS production. Lastly, citric acid coating reduced the amount of ROS produced in comparison to polyol coated MNPs.The reactivity of the radicals produced by MnFe2O4 (•OOH) compared to the ones produced by Fe3O4 (•OH) was tested by degrading AO8 aqueous solutions (100 ppm) in the presence of H2O2 (0.3 M). Both radicals were able to successfully decompose the organic matter, but with the •OH radicals in a much faster manner. In general, MNPs reactivity can be tuned considering the size, doping and coating leading to efficient nanocatalysts for environmental remediation.