Dissolution of cobalt ferrites by thioglycolic acid

Abstract

The dissolution of cobalt ferrites Co_xFe_3–xO₄ by thioglycolic acid involves the chemisorption of thioglycolate anion onto Fe^III ions of the solid, followed by an electron transfer from the ligand to the metal ion and subsequent release of Fe^II. Kinetic data suggest that two adjacent Fe^III–L sites evolve to two Fe^II+L₂. Substitution of Co^II for Fe^II does not bring about any noticeable change in the kinetics for x < 0.6. For larger values of x, the early mechanism of dissolution changes, suggesting that electron hopping within the octahedral sites may produce a chain dissolution of Fe^II for each single original electron transfer from thioglycolate. Rate data in the presence of exogenous Fe^II are also discussed.