Kinetics of Metal Extraction:Rate Controlling Steps and Experimental Techniques Used to Establish a Design Equation

Abstract

A previously established equation for the rate of extraction of a metal ion from an aqueous into an organic phase is used to conduct a numerical study of its response to changes in the concentrations of reactants and mass transfer coefficients. Results indicate that the rate of extraction can be controlled exclusively by the chemical reaction (chemical regime) or by a combination of mass transfer and chemical parameters (mixed regime). In the mixed regime mass transfer control may occur in either phase or both depending on the relative concentrations of reactasnts and the hydrodynamic conditions of the phases. The hydrodynamic conditions of two laboratory contactors: (i) the quiescent interface cell and (ii) the single drop, are introduced into the design equation as mass transfer coefficients to simulate experimental results obtained with these techniques. The analysis shows that in order to obtain a design equation results obtained with the single drop technique are inconclusive even when the site of the rate controlling reaction is known.