Equilibrium and kinetic studies of the extraction of chelated copper(II) anions with Aliquat 336

The equilibrium and kinetics of solvent extraction of Cu²⁺ from aqueous solutions containing equimolar EDTA with Aliquat 336 in n-decanol and kerosene at 298 K were investigated. The concentrations of Cu²⁺ (8-50 mol m^-3), Cl^- (5-60 mol m^-3), and Aliquat 336 (20-100 mol m^-3) were varied. A semi-empirical model with three parameters was proposed to describe the equilibrium behavior, in which the non-idealities in both aqueous and organic phases were considered. Over the ranges studied, the model agreed reasonably well with the experimental data (standard deviation, 15%). The forward and backward reaction rate constants were determined as (5.31 ± 0.16) × 10^-6 m^9/4 mol^-3/4s^-4 and (2.62 ± 0.09) × 10^-7 s^-1, respectively, at 298 K. An interfacial reaction mechanism was proposed, which revealed that the reaction between the chelated anions and trimeric amine molecules at the interface was rate limiting. The derived rate laws were consistent with the experimental results.