Kinetics of dissolution of metal powders and metal oxides

Current approaches to study of the kinetics of the dissolution of metallic powders and metal oxides are discussed. The applicability of the various kinetic equations to the rate of a topochemical reaction is discussed. It is determined by features of the appearance and growth of the nuclei of the solid product, by the change in the size of the interface of the solid phases, and by the effect of the reaction product. For the case of the kinetics of reaction of copper, nickel, cobalt, zinc, cadmium, and lead powders and their oxides with aqueous and nonaqueous solutions of ammonium salts it was shown that the conditions of formation, the properties, and the behavior of the product layer formed on the surface of the reacting particle can have a determining effect on the kinetics and mechanism of the reaction. The results from the kinetic experiment are examined in terms of a model described by the generalized topochemical equation =1 – exp(–ktⁿ) and also a model based on an analysis of the reaction rate constants at various sections of the kinetic curve. Correlations were established between the coefficient n in the generalized topochemical equation and also the rate constant and density or solubility of the reaction product formed on the surface of the reacting particle.Translated from Teoreticheskaya i Éksperimental'naya Khimiya, Vol. 31, No. 5, pp. 284–297, September–October, 1995.