Kinetic evidence for the redox cycling of manganese(II,III) in the presence of –ON(NO)SO3– in aqueous media

Abstract

Redox cycling of Mn^II/III in the presence of ^–ON(NO)SO₃^– in the absence and presence of oxygen was studied by following the increase and decrease of Mn^III spectrophotometrically as a function of [^–ON(NO)SO₃^–], [Mn^III], [Mn^II] and pH. The autoxidation reaction exhibits typical autocatalytic behaviour in which the induction period depends on the concentrations of Mn^III and ^–ON(NO)SO₃^–. Under acidic conditions the reaction does not take place in the absence of Mn^III or O₂. The concentrations of O₂, Mn^II and ^–ON(NO)SO₃^– determine whether only oxidation of Mn^II to Mn^III, or reduction of Mn^III to Mn^II, or both in one or two redox cycles is observed. Preliminary simulations of some of the observed kinetic traces are presented.