Sizing the Fenton’s catalyst

Abstract 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 (FeSO 4 ), and hydrogen peroxide (H 2 O 2 ). In this work, iron oxide (Fe 2 O 3 ) nanoparticles (NPs) were detected in the aqueous mixture of FeSO 4 and H 2 O 2 at pH 2.5 and pH 3. Fe 2 O 3 NPs were also detected mixing Fe 2 (SO 4 ) 3 , FeCl 2 and FeCl 3 with H 2 O 2 . Size distribution of the Fe 2 O 3 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 FeSO 4 /H 2 O 2 and corroborated their nanoparticle size. In the aqueous FeSO 4 /H 2 O 2 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 Fe 2 O 3 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.