Strong Enhancement on Fenton Oxidation by Addition of Hydroxylamine to Accelerate the Ferric and Ferrous Iron Cycles

Abstract

The Fenton system generates reactive species with high oxidation potential such as hydroxyl radicals (HO(•)) or ferryl via the reaction between Fe (II) and H₂O₂. However, a number of drawbacks limit its widespread application including the accumulation of Fe (III) and the narrow pH range limits, etc. The aim of this study is to propose a much more efficient Fenton-HA system which is characterized by combining Fenton system with hydroxylamine (NH₂OH), a common reducing agent, to relieve the aforementioned drawbacks, with benzoic acid (BA) as the probe reagent. The presence of NH₂OH in Fenton's reagent accelerated the Fe (III)/Fe (II) redox cycles, leading to relatively steady Fe (II) recovery, thus, increased the pseudo first-order reaction rates and expanded the effective pH range up to 5.7. The HO(•) mechanism was confirmed to be dominating in the Fenton-HA system, and the generation of HO(•) was much faster and the amount of HO(•) formed was higher than that in the classical Fenton system. Furthermore, the major end products of NH₂OH in Fenton-HA system were supposed to be NO₃(-) and N₂O.

Efficient degradation of sulfamethoxazole by the Fe(II)/HSO5− process enhanced by hydroxylamine: Efficiency and mechanism

“…Moreover, the steady-state concentration of Fe(III) could be attributed to dynamic equilibrium of the iron ion circulation given in Eqs. (3)- (5) (Chen et al, 2011;Han et al, 2014). The higher steady-state concentration of Fe(III) in the system with SMX was probably due to the influence of target organics and intermediates on the UV absorption of solution at 300 nm.…”

“…Then increasing HA concentration continuously from 0.4 to 1.0mM, the improvement on the removal of SMX was found to be insignificant. Authors (Chen et al, 2011;Zou et al, 2013) reported that HA could effectively promote the redox cycle of Fe(III) to Fe(II), improve the generation of reactive species and increase the removal of organic pollutants at pH 3.0. However, excess HA could quench the reactive species (e.g., SO4…”

“…4. The interference of HA and PMS on the measurement could be ignored at the experimental concentration (Chen et al, 2011;Zou et al, 2013). However, due to the obvious absorption of SMX and its degradation products at 300 nm, methanol was used to consume the reactive radicals (i.e., SO4 (2) (Brandt and Van Eldik, 1995) and the slow transformation from Fe(III) to Fe(II).…”

“…The slow conversion from Fe(III) back to Fe(II) is considered to be the major drawback of Fe(II)/PMS process (Zou et al, 2013). Chen et al (2011) reported that hydroxylamine (NH2OH, HA) could effectively accelerate the redox cycle of Fe(III) to Fe(II). Owing to the low rate constants with SO4 •- (Neta et al, 1988) and HO • (Buxton et al, 1988), protonated HA can improve the degradation of benzoic acid (Zou et al, 2013), trichloroethylene (Tan et al, 2012), diuron (Wu et al, 2015), and Orange G (Han et al, 2014), as well as reducing the dosage of Fe(II) in Fe(II)/PMS or Fe(II)/PS system.…”

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.…”