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Kinetics of the dissolution of copper metal in some chelating systems under oxygen pressure Milants, Henri Yves Jean

Abstract

An investigation was conducted on the dissolution of copper metal in aqueous solutions of ethylenediamine, glycine, α-alanine and β-alanine, under oxygen pressure. The kinetics of these reactions were investigated over a wide concentration range of the corresponding ionized species. The rate of dissolution of copper, in all solutions, has been found to be independent of the initial copper concentration, the volume of the solution and the area of the copper sample. No intermediate products, i.e., cuprous ions, were observed. Two regions were observed, having different dependence on oxygen pressure. In one, the rate depends on the first power of the oxygen pressure, and is independent of the concentration of the chelating agent. In the other region, the reaction is first order in chelating agent and independent of oxygen pressure. The rate of the reaction in this second region appears to be chemically controlled at the copper surface. The neutral and charged species of the chelating agent were found to have independent rates. These two dissolution reactions were found to be first order with respect to the concentration of the respective complexing species. The mechanism proposed by Halpern previously for the ammonia system was found to be applicable to the systems studied in the present work. The rate constants for each chelating agent have been computed and appear to be related to the stability constants. No steric effect was observed.

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