Kinetic Study for Reactive Red 84 Photo Degradation Using Iron (III) Oxide Nanoparticles in annular reactor

Abstract

Iron oxide nanoparticles (Fe2O3 NPs) were prepared by mixing iron(II) sulfate (FeSO4) and hydrogen peroxide (H2O2) in aqueous solution at pH 3. Fe2O3 NPs are used to degrade Reactive Red-84 (RR-84) azo dye in a glass annular photo-reactor using a white light lamp. The presence of Fe2O3 NPs was verified by HRTEM analyses. Kinetic studies were made varying the reagents concentration and the reaction rate was controlled increasing the concentration of iron ions in comparison with H2O2. Langmuir-Hinshelwood (L-H) kinetic model was performed to analyze heterogeneous catalytic reactions under illumination conditions. The elimination process of azo dye followed the pseudo first-order kinetic according to L-H model. The adsorption process of the azo dye on the catalytic surface was determinant for the dye photodecomposition. The linear expression of the Langmuir adsorption isotherm under darkness was further used to establish the maximum amount of dye adsorbed Qmax=0.80 ± 0.18 mg*mgcatalyst-1 and the adsorption constant kads=0.016 ± 0.004 L*mg-1. The Langmuir-Hinshelwood equilibrium constant for dye adsorption under illumination conditions was KL-H=0.03 ± 0.02 L*mg-1. This similarity with adsorption constants could depict an evidence which suggest that Fe2O3 NPs are presents in Fenton´s reaction (FeSO4/H2O2) interacting as catalysts in the degradation of organic substrates.