Sizing the Fenton's catalyst

Historically Fenton's reaction, under darkness or illumination conditions, is considered a homogeneous process. The most important feature of Fenton's reagent is related to its preparation due to it is an effective catalyst just using iron(II) ions, from specifically iron(II) sulfate salt (FeSO4), and hydrogen peroxide (H2O2). In this work, iron oxide (Fe2O3) nanoparticles (NPs) were detected in the aqueous mixture of FeSO4 and H2O2 at pH 2.5 and pH 3. Fe2O3 NPs were also detected mixing Fe-2(SO4)(3), FeCl2 and FeCl3 with H2O2. Size distribution of the Fe2O3 NPs was measured by Dynamic Light Scattering (DLS) particles analyzers. High Resolution Transmission Electron Microscopy (HR-TEM) and X-Ray Diffraction (XRD) analyses confirmed the presence of different iron oxide phases in the mixture of FeSO4/H2O2 and corroborated their nanoparticle size. In the aqueous FeSO4/H2O2 system, at pH 3, free iron ions concentration was measured by Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) analysis showing a concentration of 3.1*10(-6) M and by Cyclic Voltammetry (CV) the free iron ions concentration detected was 4.4*10(-6) M. Under Fenton's conditions, pH 2.5 and pH 3, these Fe2O3 NPs degraded and photodegraded two pesticides, three textile-dyes and a derived phenol compound. UV-vis Spectroscopy and Chemical Oxygen Demand (COD) analyses determined the degradation level of the pollutants. The obtained results suggest that Fenton's reaction should be considered as a heterogeneous catalytic process. (C) 2017 Elsevier B.V. All rights reserved.