Oxidation of ferrous ions by perhydroxyl radicals

Abstract

The rate of the reaction between H02 radicals and Fe2+ is dependent on temperature, the rate constant at 20°C being 9.1 f0.4 x lo5 M-' s-I (1.2 2 0.05 x lo6 M-' s-I at 25°C) and the activation energy 10.0+ 1.0 kcal mol-' (42 kJ mol-I). The initial reaction product is considered to be an outer-sphere complex between Fe3+ and HO;. This hydroperoxide complex appears to react with Fe2+ in a fast reversible reaction to give a bridge compound. The absorption spectra of the two complexes have been measured. The molar extinction coefficients at 450 nm are 140f: 50 M-* cm-' and 1240rf: 100 M-I cm-l, respectively. The equilibrium constant for the formation of the bridge compound varies from 22 k 2 M-' at 20°C to 37.5 rf: 0.5 M-I at 40°C. The hydroperoxide complex dissociates unimolecularly with a rate constant at 20 or 25°C of 1.8 & 0.1 x lo3 s-l, activation energy 2.1 k 0.2 kcal mol-l. The bridge compound dissociates unimolecularly with a rate constant at 20°C of 1.8k0.1 x lo4 s-I (2.5rf:O.l x lo4 s-I at 25"C), activation energy 11.4f 1.1 kcal mo1-'. The final product of the whole reaction is the hydrated ferric ion.

Oxidation processes of aromatic sulfides by hydroxyl radicals in colloidal solution of TiO2 during pulse radiolysis

“…The Cl À is oxidized at the formation rate constant (k c ) of 4.3 Â 10 9 M À1 s À1 and the resulting Cl ÅÀ 2 indicates the absorption spectrum with a maximum peak at 340 nm [16]. In order to exclude the effects of Cl ÅÀ 2 on the kinetics analysis, we subsequently dialyzed the sample solutions ([Cl À ] ¼ 1 Â 10 À4 M).…”

Chemical Dosimetry System for γ-Ray Irradiation Based on the Formation of Phenol from Aqueous Benzene Solutions

“…The reaction rate constants for chloride ions, determined by a radiochemical method, were reported to be 3 -4.3 × 10 9 M -1 s -1 . 21,22 Arakaki et al, however, have pointed out that the reverse reaction between chloride ions and hydroxyl radicals is also fast. 23 They determined the experimental net reaction rate constant of chloride ions and hydroxyl radicals to be 2.7 × 10 7 M -1 s -1 using a photochemical steady-state method.…”

Evidence for a second kind of trapped electron in some deuterated aqueous glasses at low temperatures. A pulse radiolysis study

“…This is probably due to C1.-; A, , , , , for C12-in aqueous solution at room temperature is 340 nrn (12). However there could be a contribution from ClOH-, which has a A, , , at 350 nm in aqueous solution at room temperature (12).…”