Ferrate(VI) Oxidation of Aqueous Phenol:  Kinetics and Mechanism

Abstract

Kinetic and thermodynamic parameters for ferrate(VI) oxidation of phenol have been measured in isotopic solvents, H 2 O and D 2 O, using ambient and high-pressure stopped-flow UV-visible spectroscopy. An increase (fast stage) and then a decrease (slow stage) in absorbance at 400 nm are observed when potassium ferrate (K 2 FeO 4 ) and aqueous phenol solutions are mixed rapidly. This suggests that small amounts of unstable intermediate 4,4′-biphenoquinone are produced during this redox process. An electron paramagnetic resonance signal for the reaction mixture of ferrate and phenol trapped by spin-trap R-(4-pyridyl-1-oxide)-N-tertbutylnitrone indicates a radical reaction pathway. Gas chromatographic/mass spectrometric measurements show p-benzoquinone is a major organic product, and the red ferric thiocyanate complex formed from addition of potassium thiocyanate to the spent reaction solution indicates that Fe(VI) is reduced to Fe(III). Activation enthalpy, entropy, and volume changes have been determined. There is a primary isotope effect for the formation of the intermediate (fast stage), k fast (H 2 O)/k fast (D 2 O) ) 2.4 ( 0.6. Because the phenol hydroxylic hydrogen is deuterated in D 2 O, this isotope effect suggests that a hydrogen bond is formed in the transition state.

Ferrate(VI) in the Treatment of Wastewaters: A New Generation Green Chemical

“…It was further, supported by the EPR studies, showed that (24)) [46]. (24) Further, the two-electron transfer mechanism of Fe(VI) was proposed for the degradation of several nitrogen containing compounds [47][48][49].…”

Ferrate(VI) oxidation of tetrabromobisphenol A in comparison with bisphenol A

“…3. Initially, Fe(VI) oxidizes the phenol moiety of TBBPA by one electron transfer generating a phenoxyl radical and Fe(V) as the first step (Rush et al, 1995;Huang et al, 2001;Li et al, 2008;Yang et al, 2011b). The phenoxy radical is stabilized by electron resonance within the phenol ring and forms radical R1, which supported by the calculation of charge distribution and spin densities via molecular modeling (Lin et al, 2009;Feng et al, 2013;Pang et al, 2014).…”

A study of the preparation and reactivity of potassium ferrate

“…In this analysis, colloidal ferric oxide interference is minimized by a 385 nm baseline correction (Licht et al, 2001). Other reaction species such as iron(II) and iron(III) phosphate have no interference at 510 nm (Huang et al, 2001). BPA concentration was determined by using a high performance liquid chromatograph, with a high pressure pump (Spectrasystem HPLC P4000), a UV detector (UV 6000LP), and an auto sampler (AS3000).…”