LAUSR

Abstract Cobalt extraction by Cyanex 272, Bis(2,4,4-trimethylpentyl)phosphinic acid, (HR) in micellar solution has been shown to be a two-step reversible reaction and the reaction rate constants for the forward and reverse reactions have been obtained. In this investigation the influence of the addition of anionic surfactants, Sodium Dodecyl Sulphate (SDS), on the rate of extraction of cobalt from the aqueous phase by Cyanex 272 in the micelle phase was investigated. The anion surfactant (SDS) was found to increase the rate of extraction. This could be mainly ascribed to the increase in the local concentration of cobalt at the interface generated by the electrostatic surface potential with added surfactant. The effect of charge on the reaction rate has been modelled based on the electrostatic surface potential generated by the added surfactant.