Activation parameters of ferryl ion reactions in aqueous acid solutions

Abstract

Stock solution of ozone was prepared by bubbling the effluent from an Erwin Sander (V) ozonator through an aqueous HClO 4 solution. Ozone concentrations of (2.5Ϫ3.0) ϫ 10 Ϫ4 M were achieved without any special procedure. The ozone concentration was determined spectrophotometrically at its maximum absorption wavelength, max ϭ 260 nm, using an ApparatusFor the kinetic studies a Hi-Tech SF 51 Stopped-flow spectrophotometer (SFS) with UV and VIS lamps was used. This instrument has a mixing time of about 1 -2 ms, which enables us to measure rate constants in the range of 0.01 -700 s Ϫ1 . Both the ozone and ABSTRACT: The temperature dependence of the oxidation kinetics of Fe 2ϩ by O 3 at pH 0 -3 was studied by stopped-flow technique in the temperature range 5 -40°C. Activation parameters of the reactions involved in formation and decay of the ferryl ion (iron(IV)), FeO 2ϩ are determined. The reaction of Fe 2ϩ ϩ FeO 2ϩ was found to branch into two channels forming iron(III)-dimer, Fe(OH) 2 Fe 4ϩ , and Fe 3ϩ . The yield of the dimer, Fe(OH) 2 Fe 4ϩ , increases with temperature on the expense of the Fe 3ϩ yield. On the basis of the overall rate constant and relative yield of Fe(OH) 2 Fe 4ϩ the activation energy is determined for both channels. The activation parameters of the hydrolysis of the ferryl ion and its reaction with H 2 O 2 were also determined.

The role of transition metal ions on HO<sub>x</sub> radicals in clouds: a numerical evaluation of its impact on multiphase chemistry

“…However, Logager et al (1992) provided final evidence that this reaction between Fe(II) and ozone produces Fe(IV) (the ferryl ion) and oxygen (R16). Rate constants and activation energies for reactions of the ferryl ion with selected inorganic and organic compounds present in atmospheric water have been measured by Jacobsen et al (1997a;1998b) (reactions R2, R12, R15, R27, R18, R24, R27, R28, R36, R37, R38, R39). In all Fe(IV) reactions, Fe(III) is formed.…”

“…The formation of dimer Fe(OH) 2 Fe 4+ is favoured at higher temperature (R19). Afterwards, this species produces also Fe 3+ (R20 and R21) but with a very slow rate (Jacobsen et al, 1997a). For a pH around 3, the ferryl ion plays a role mainly as a temporary OH radical sink whereas for more acidic solution, the ferryl ion is more likely to react as a distinct species (Jacobsen et al, 1998b).…”

Degradation of ibuprofen by a synergistic UV/Fe(III)/Oxone process

“…S3 shows the absorption spectra of Fe 3+ , Fe 2+ , Oxone and Fe 3+ /Oxone solutions. It is known that FeO 2+ exhibits strong absorption at the wavelength of 320 nm [45]. As indicated in Fig.…”

“…S2 also shows the redox potentials of reaction (3) solution are lower than that of the solution containing IBP and Oxone, which is due to the consumption of Oxone and the transformation of Fe 3+ to Fe 2+ . In previous studies, the formation of ferryl-ion (FeO 2+ ) was reported both in traditional Fenton reaction [43,44] and Fe 2+ /O 3 system [45,46]. Fig.…”

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

“…Since the original constant k 35 = 1.3 Â 10 À2 M À1 s À1 corresponds to kinetics of order 2 (FeO 2+ + H 2 O), the equivalent constant for order 1 is obtained by multiplying k 35 by [H 2 O]. In addition, the FeIVðOHÞ 2þ 2 complex symproportionates with the Fe 2+ ion according to two reaction pathways (Reactions (36a) and (36b)) [15,36,37]. It reacts also with H 2 O 2 (Reaction (37)) and with HO 2 and OH radicals (Reactions (38) and (39) …”