Catalytic Decomposition of Hydrogen Peroxide by Fe(III) in Homogeneous Aqueous Solution: Mechanism and Kinetic Modeling

Abstract

This paper describes a kinetic model for the decomposition of hydrogen peroxide by ferric ion in homogeneous aqueous solution (pH < 3). The reaction was investigated experimentally at 25.0 °C and I ) 0.1 M (HClO 4 /NaClO 4 ), in a completely mixed batch reactor and under a wide range of experimental conditions (1 e pH e 3; 0.2 mM e [H 2 O 2 ] 0 e 1 M; 50 µM e [Fe(III)] 0 e 1 mM; 1 e [H 2 O 2 ] 0 / [Fe(III)] 0 e 5000). The results of this study demonstrated that the rate of decomposition of hydrogen peroxide by Fe-(III) could be predicted very accurately by a kinetic model which takes into account the rapid formation and the slower decomposition of Fe(III)-hydroperoxy complexes (Fe III -(HO 2 ) 2+ and Fe III (OH)(HO 2 ) + ). The rate constant for the unimolecular decomposition of the Fe(III)-hydroperoxy complexes was determined to be 2.7 × 10 -3 s -1 . The use of the kinetic model allows a better understanding of the effects of operational parameters (i.e., pH and [H 2 O 2 ] 0 / [Fe(III)] 0 ) on the complex kinetics of decomposition of H 2 O 2 by Fe(III).

Degradation of diethanolamine by Fenton's reagent combined with biological post-treatment

“…Interestingly, in the case of pH 1 the initial decrease of COD was significant, but no further decrease was observed at longer reaction time. This is in agreement with a very slow reduction of Fe(III) to Fe(II) at pH 1, as reported in the literature [18]. …”

“…In the acidic pH range, hydrogen peroxide in the presence of ferrous ions undergoes a series of redox reaction, of which the main ones are the following [18]:…”

“…Note that R3 competes with other reactions (R2, R4) that scavenge OH • and may lead to loss of the oxidation power in the system [18].…”

“…A higher or lower pH sharply reduces the effectiveness of the Fenton's reaction. At low pH the complexation of Fe(III) with hydrogen peroxide is inhibited, therefore inhibiting the step of H 2 O 2 reduction [18], while at a high pH ferric ions precipitate as ferric hydroxide, which catalyzes the decomposition of hydrogen peroxide.…”

Synthesis of akageneite (beta-FeOOH)/reduced graphene oxide nanocomposites for oxidative decomposition of 2-chlorophenol by Fenton-like reaction

“…From Table S2, where the curve fit results were summarized, the 2-CP oxidation rate at initial pH 4.0 is 2-3 times higher than that at initial pH 9.0. The decrease of the decomposition rate at higher pH was attributed to the precipitation of Fe(III) and the reduction of H 2 O 2 life [36]. With the increase of rGO content, oxidation rates of 2-CP increase exponentially (i.e., oxidation rates of 2-CP for Ak-20 is almost 10 times than that for Ak), implying that the catalytic activity was enhanced by the introduction of rGO.…”