Kinetics and the effect of electrostatic surface potential on nickel(II) extraction by 2-hydroxy-5-nonylacetophenone oxime (LIX 84) in a micellar phase

The kinetics of extraction and the effect of electrostatic surface potential on the nickel(II)/2-hydroxy-5-nonylacetophenone oxime (HNAPO) extraction system were characterised in a non-ionic micellar system. A two step reaction mechanism between nickel(II) and HNAPO was found to satisfactorily explain the observed kinetics. Simulation of the kinetics of the complexation reaction over a wide range of concentrations provided the rate constants for the proposed mechanism. The addition of a cationic surfactant, dodecyl trimethyl ammonium chloride (DTAC), slowed the reaction kinetics, while the inclusion of an anionic surfactant, sodium dodecyl sulphate (SDS), enhanced the reaction kinetics relative to the non-ionic micellar system. The charge effects on the reaction rate could be successfully modelled based on the electrostatic surface potential generated by the anionic and cationic surfactants.