Pulse-radiolysis study of some unstable complexes of iron

Abstract

Pulse radiolysis of oxygen-containing solutions of ferrous perchlorate in perchloric acid (1 M) enables the formation and disappearanceof a ferrichydroperoxidecomplex, F e 3 + H 0 ~, to be observed. The rate constant for its formation by reaction of Hot radicals with free ferrous ions is 2.1 f0.4 x lo6 M-ls-l in the pH range 0-2.1. The complex disappears in a first-order reaction with a rate constant independent of pH in the range 0-2.1. It exhibits a broad absorption in the region 280-600nm, with &a30 nm = 280f30 M-l cm-l. In the absence of oxygen, a different absorbing species can be seen, attributed to a ferric hydride complex, Fe3+H-. This is formed by the reaction of hydrogen

Critical Review of rate constants for reactions of hydrated electrons, hydrogen atoms and hydroxyl radicals (⋅OH/⋅O− in Aqueous Solution

“…It readily reduces inorganic ions having more positive reduction potentials than itself, but often at slower rates than e aq − . In some cases, in highly acidic solution, it effectively reacts as an oxidant, forming a hydride intermediate which decomposes to molecular hydrogen and the oxidized solute 40,41…”

The Influence of Extracellular Superoxide on Iron Redox Chemistry and Bioavailability to Aquatic Microorganisms

“…In practice, therefore, ${\text{O}}_2^{-*}$ behaves primarily as a reductant or oxidant in natural waters. Early laboratory studies of reactions between aqueous Fe and ${\text{O}}_2^{-*}$ typically used pulse radiolysis to generate ${\text{O}}_2^{-*}$ and UV–visible spectrophotometry to observe the subsequent reactions (Jayson et al, 1969, 1973; Buettner et al, 1983; Bull et al, 1983; Rush and Bielski, 1985). While useful in understanding the chemistry of Fe and ${\text{O}}_2^{-*},$ results from these studies must be applied to environmental systems with caution because the use of high concentrations of both Fe and ${\text{O}}_2^{-*}$ could favor reactions that are not important at lower, environmentally relevant concentrations.…”

The influence of iron on water radiolysis in cement-based materials

“…Reactions (77) and (78) have little impact on the course of the radiolysis in cement media, but may contribute in the capture of a small fraction of the reducing radicals of primary origin in anaerobic environment. The Fe(III) hydride formed in both cases reacts with water (H 3 O + ) and produces dihydrogen [49], as follows: Although radicals H Å and e À aq are very powerful as Fe(III) reducers, the two observed reactions with H Å help to detect a modulation in the reactivity in relation to pH, with the rate constants increasing with the complexation level of Fe(II) [50,51]. As generally observed, the reaction occurs also faster with the base form of antagonistic species [20].…”