AN ELECTROCHEMICAL MODEL FOR REDUCTION OF MNO2 WITH FE2+ IONS

The reduction kinetics of MnO2 by Fe2+ ions in acidic solution have be en studied. The effects of stirring rate, particle size, temperature, Fe2+ and H+ concentrations have been investigated. Diffusional resista nces are negligible above 900 r.p.m. and the rate is controlled by ele ctrochemical reaction. A mixed-potential model developed to describe m etallic corrosion has been used in combination with the shrinking core model to explain the reaction kinetics. The overall reaction has been written in terms of cathodic and anodic half-cell reactions. The Tafe l equation has been used as a starting point to derive a rate equation . A value of 0.5 has been obtained for charge transfer coefficients, w hich implies the existence of symmetrical charge barriers. The kinetic s of the cathodic reduction reaction are first order with respect to t he proton concentration.