Intensification of the Fenton Process by Increasing the Temperature

Abstract

The effect of temperature on the Fenton process has been studied within the range of 25−130 °C using phenol (100 mg/L) as target compound, 10 mg/L Fe2+, and a dose of H2O2 corresponding to the theoretical stoichiometric amount (500 mg/L) for mineralization. The TOC reduction was considerably improved as temperature increased. Whereas at 25 °C the TOC decreased less than 28%, a reduction of almost 80% was achieved at 90 °C. Beyond this temperature no significant improvement of mineralization was observed, although the rate of the process was considerably enhanced. Increasing the temperature leads to a more efficient consumption of H2O2 which indicates an enhanced iron-catalyzed H2O2 decomposition into radicals as temperature increases rather than the generally accepted thermal breakdown of H2O2 into O2 and H2O. Therefore, working at a temperature well above the ambient provides a way of intensifying the Fenton process since it allows a significant improvement of the oxidation rate and the mineralization percentage with reduced H2O2 and Fe2+ doses. Furthermore it would not represent a serious drawback in the case of many industrial wastewaters which may be already at that temperature. Besides, partial recovery of heat from the treated off-stream would always allow saving energy. The TOC time-evolution was well described by a kinetic model based on TOC lumps with apparent activation energy values in the range of 30−50 kJ/mol.

Preparation of magnetite-based catalysts and their application in heterogeneous Fenton oxidation – A review

“…It has to be highlighted the potential of magnetite as CWPO catalyst under the testing conditions due to its high activity and remarkable stability. Moreover, the mineralization percentage achieved was even higher than the obtained upon homogeneous Fenton oxidation under similar working conditions [27].…”

“…A slight decrease of catalytic activity was observed upon three consecutive runs, which was attributed to small leaching of iron from the solid. Despite the fact that several magnetic minerals have shown to be fairly stable in the process, the degradation rates observed are still far from those of homogeneous Fenton oxidation under similar operating conditions [27]. With the aim of improving the activity of the catalysts and thus, increasing the oxidation rate, the effect of including other metals into the magnetite structure by isomorphic substitution of Fe has been studied by several authors [37-39, 57, 58] were directly related to the amount of iron leached, which decreased upon the three successive runs (13, 6 and 4 mg L -1 measured in the liquid phase).…”

“…(1-2)), being commonly used 1 part of iron per 4-25 parts of hydrogen peroxide (w/w) [24], while the optimum dose of oxidant is frequently the stoichiometric amount for complete oxidation, namely mineralization [25,26]. Although most of the works dealing with Fenton oxidation have been carried out at mild conditions, Zazo et al, (2011) [27] have recently demonstrated that increasing the temperature, up to 120 ºC, clearly improves both the oxidation rate and the degree of mineralization of the pollutants. The Fenton effluent is finally neutralized with NaOH, and thus iron complexes precipitates as Fe(OH) 3 .…”

Triclosan breakdown by Fenton-like oxidation

“…All the acids were mineralized except oxalic which showed to be refractory to Fenton oxidation even at those higher temperatures. Zazo et al [40] reported that oxalic acid can be mineralized upon Fenton oxidation at around 100°C. Fig.…”

Enhancement of Fenton oxidation for removing organic matter from hypersaline solution by accelerating ferric system with hydroxylamine hydrochloride and benzoquinone

“…Currently, many technologies have been developed to improve Fenton oxidation for removing organic contaminants from aqueous solutions, such as photo-assisted (Al Momani et al, 2006;Kusic et al, 2006;Lau et al, 2002), microwave-enhanced (Liu et al, 2013;Yang et al, 2009), heating (Pliego et al, 2012;Zazo et al, 2011), and quinone (Chen and Pignatello, 1997;Gomez-Toribio et al, 2009) and hydroxylamine hydrochloride (HA) (Chen et al, 2011) redox cycling. As mentioned above, a major drawback of the Fenton system has been the accumulation and hydrolysisprecipitation of ferric ions, which could further slow down the whole Fenton process.…”