Separation of platinum and palladium by liquid surfactant membranes utilizing a novel bi-functional surfactant

摘要

Using a bi-functional surfactant which has abilities both as an emulsifier and a carrier, the separation of platinum and palladium by liquid surfactant membranes (LSMs) has been conducted in a stirred tank. The effects of several operational conditions on the behavior of metal extraction and the emulsion stability in LSMs were systematically studied. The bi-functional surfactant not only stabilized a W/O emulsion in a relatively low concentration but also showed a high extraction ability for platinum. Using the bi-functional surfactant, platinum was extracted quickly and concentrated effectively from an external feed solution into an internal recovery phase of W/O emulsions through a thin liquid membrane. Further, the extraction kinetics of the metals by LSMs containing the bi-functional surfactant was examined. The hydrophobic structure of the surfactants was found to be one of the important factors in ensuring a high extraction rate of metal ions by LSMs. An interfacial reaction model which takes into account the adsorption of the surfactant at the interface has been proposed to evaluate the permeation rate of metals by LSMs. The newly developed surfactant appears to be one of the best surfactants currently available for platinum-group metal extraction by liquid surfactant membranes.