Extraction kinetics of copper with versatic acid.

Abstract

The extraction kinetics of copper from aqueous ammonium nitrate-ammonia mixture with n-hexane solution of Versatic acid was studied by the single-drop method. The change of extraction rate with concentrations of reactant species, such as copper and hydrogen ions in the continuous phase and Versatic acid in the dispersed phase, respectively, was studied for drop-formation and drop-rise periods. It became clear that the extraction rates during both periods were controlled only by the heterogeneous complex-forming reaction at the drop surface. The heterogeneous reaction rate was found to be proportional to the concentration of copper ion in the aqueous phase, inversely proportional to that of hydrogen ion and independent of that of Versatic acid in the dispersed phase. From the dependency of the reaction rate on the concentration of each reactant species and from the experimental results on the interfacial adsorption properties of Versatic acid, the rate-controlling step of this complex-forming reaction at the drop surface is considered to be as follows. Cu2+aq.+R-ad.→←Cu+ad.