Oxidation of thiocyanate by iron(V) in alkaline medium
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abstract
The oxidation of thiocyanate (SCN -) by iron(V) (Fe(V)) was studied as a function of pH in alkaline solutions by a premix pulse radiolysis technique. The reaction precedes via a two-electron oxidation, which converts Fe(V) to Fe(III). The rates decrease with an increase in pH. The reactivity of diprotonated Fe(V) species, H2FeO4- with SCN - could account for the decease in rate with increasing pH. The oxidation of thiocyanate by iron(V) (Fe(V)) was studied as a function of pH in alkaline solutions by a premix pulse radiolysis technique. The rates decrease with an increase in pH. The rate law for the oxidation of SCN - by Fe(V) was obtained as -d[Fe(V)]/dt = k 10{[H +] 2/([H +] 2 + K 2[H +] + K 2K 3)}[Fe(V)][SCN -], where k 10 = 5.72 0.19 10 6 M -1 s -1, pK 2 = 7.2, and pK 3 = 10.1. The reaction precedes via a two-electron oxidation, which converts Fe(V) to Fe(III). Thiocyanate reacts approximately 10 3 faster with iron(V) than does with iron(VI). 2004 Elsevier B.V. All rights reserved.