Kinetics of ferrate(V) decay in aqueous solution. A pulse-radiolysis study

Journal Article · Wed Oct 18 00:00:00 EDT 1989 · Inorganic Chemistry; (USA)

DOI:https://doi.org/10.1021/ic00320a004· OSTI ID:7002924

Rush, J D; Bielski, B H.J. ^[1]

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1. Brookhaven National Lab., Upton, NY (USA)

The kinetic and spectral properties of pentavalent iron derived from pulse-radiolytic reduction of aqueous ferrate(VI) by 2-propanol radicals have been characterized over the pH range 6.3-13. Three forms of iron(V) occur over this pH range, which are represented by the following equilibria: H{sub 2}FeO{sub 4}{sup {minus}} {rightleftharpoons} H{sup +} + HFeO{sub 4}{sup 2{minus}}, pK{sub 2} = 7.5; HFeO{sub 4}{sup 2} {rightleftharpoons} H{sup +} + FeO{sub 4}{sup 3{minus}}, pK{sub 3} = 10.1 The protonated forms of ferrate(V) are unstable due to decomposition by a second-order process that results in the formation of hydrogen peroxide and ferric ions rather than disproportionation. The bimolecular rate constants in 1 mM phosphate/borate buffer at 25{degree}C are k{sub 1}(H{sub 2}FeO{sub 4}{sup {minus}} + H{sub 2}FeO{sub 4}{sup {minus}}) = (9 {plus minus} 2) {times} 10{sup 7} M{sup {minus}1} s{sup {minus}1}, k{sub 2} (H{sub 2}FeO{sub 4}{sup {minus}} + HFeO{sub 4}{sup 2{minus}}) {approx} 3 {times} 10{sup 7}M{sup {minus}1} s{sup {minus}1}, k{sub 3}(HFeO{sub 4}{sup 2{minus}} + HFeO{sub 4}{sup 2{minus}}) {approx} 1.5 {times} 10{sup 7} M{sup {minus}1} s{sup {minus}1}, and k{sub 4} (HFeO{sub 4}{sup 2{minus}} + FeO{sub 4}{sup 3{minus}}) = (1.0 {plus minus} 0.2) {times} 10{sup 7} M{sup {minus}1} s{sup {minus}1}. At higher pH, FeO{sub 4}{sup 3{minus}} decays by a unimolecular process, k{sub f} = 8 {plus minus} 1 s{sup {minus}1}. The very high second-order rates as well as the peroxide product suggest that oxide ligands bound to ferrate(V) may have a much higher degree of free-radical character than does the parent ferrate(VI) ion. 28 refs., 5 figs., 5 tabs.

• DOE Contract Number: AC02-76CH00016
• OSTI ID: 7002924
• Journal Information: Inorganic Chemistry; (USA), Journal Name: Inorganic Chemistry; (USA) Vol. 28:21; ISSN 0020-1669; ISSN INOCA
• Country of Publication: United States
• Language: English

Related Subjects

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEAR CHEMISTRY
400600* -- Radiation Chemistry
ALCOHOLS
AQUEOUS SOLUTIONS
CHEMICAL RADIATION EFFECTS
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
DATA
DECOMPOSITION
DISPERSIONS
ELECTROMAGNETIC RADIATION
ELECTRONS
ELEMENTARY PARTICLES
EXPERIMENTAL DATA
FERMIONS
GAMMA RADIATION
HYDROXY COMPOUNDS
INFORMATION
IONIZING RADIATIONS
IRON COMPLEXES
IRRADIATION
LEPTONS
MIXTURES
NUMERICAL DATA
ORGANIC COMPOUNDS
PROPANOLS
PULSED IRRADIATION
RADIATION CHEMISTRY
RADIATION EFFECTS
RADIATIONS
RADIOLYSIS
SOLUTIONS
TRANSITION ELEMENT COMPLEXES