Kinetic studies on the reaction of sodium hexa‐cyanoferrate(II) complex with peroxydisulfate anion

The oxidation of Na 4 Fe(CN) 6 complex by S 2 O   8 2−anion was found to follow an outer‐sphere electron transfer mechanism. We firstly carried out the reaction at pH=1. The specific rate constants of the reaction, k ox , are (8.1±0.07)×10 −2 and (4.3±0.1)×10 −2 mol −1 ·L·s −1 at μ=1.0 mol·L −1 NaClO 4 , T =298 K for pH=1 (0.1 mol·L −1 HCl0 4 ) and 8, respectively. The activation parameters, obtained by measuring the rate constants of oxidation 283–303 K, were Δ H ≠ =(69.0±5.6) kJ·mol −1 , ΔS ≠ =(−0.34±0.041)×10 2 J·mol −1 ·K −1 at pH=l and Δ H ≠ =(41.3±5.5) kJ·mol −1 , ΔS ≠ =(−1.27±0.33)×10 2 J·mol −1 ·K −1 at pH=8, respectively. The cyclic voltammetry of Fe(CN)   3−/4− 6shows that the oxidation is a one‐electron reversible redox process with E 1/2 values of 0.55 and 0.46 V vs. normal hydrogen electrode at μ=1.0 mol·L −1 LiClO 4 , for pH=1 and pH=8 (Tris). respectively. The kinetic results were discussed on the basis of Marcus theory.