Kinetics of metal oxide dissolution. Reductive dissolution of nickel ferrite by tris(picolinato)vanadium(II)

Abstract

A detailed study of the reductive dissolution of NiFe₂O₄ by V(pic)^– ₃ is reported. The kinetics of the reaction follow a cubic rate law and exhibit a first-order dependence on [V^II], indicating that the rate-determining step involves attack by V(pic)^– ₃ on Fe^III ions at the oxide surface. Dependences on [H⁺] and [free picolinate] are attributed to adsorption of these species at surface sites according to a simple model based on the Langmuir adsorption isotherm. Buffer and surfactant concentration had little effect. Some pitting etc. of the oxide surface occurs as the dissolution proceeds, although there appears also to be some general surface attack. The nature of the surface sites and subsequent steps in the dissolution process are discussed.