Metals extraction with carboxylic acids. II. Effect of temperature on the extraction of Cu,Ni, Co(II), Zn,Fe(III) and Co(III)

The relation between the extraction temperature and the coefficient of distribution of various metals between aqueous phases and kerosene solutions of Versatic acid has been investigated.Using a mathematical procedure, it was established that with increasing temperature the distribution coefficient changes if the composition of the metal-Versatic complex is temperature-dependent. In the case of trivalent iron a reversible increase in distribution coefficient occurs when the temperature is raised. It is suggested that this is due to a reversible depolymerization of the complex. The distribution coefficient of trivalent cobalt also increases with temperature, but here the increase is irreversible, possibly because the number of covalently bound carboxylate groups changes.In general, the distribution coefficient of metals which do not show variations in the composition of their complexes with Versatic, such as Cu, Ni, Co(II) and Zn, does not change appreciably with temperature.