Diffusion model accompanied with aqueous homogeneous reaction in hollow fiber membrane extractor.

Abstract

A kinetic study of the solvent extraction of palladium (II) with 3,3-Diethylthietane (DETE) from aqueous chloride media was conducted at 303 K using a hollow fiber membrane extractor, together with a study of the interfacial adsorption and distribution equilibria of DETE between the organic and aqueous phases. From the equilibrium studies, it was found that DETE was not interfacially active but was highly soluble in the aqueous phase. From the kinetic study, the apparent reaction orders of the extraction rate were determined experimentally from the concentration dependencies of the extraction rate on hydrogen ion, palladium (II), chloride ion and DETE, respectively. From both the equilibrium and kinetic studies, the extraction rates could be reasonably explained by a combination of a diffusion model and the homogeneous reaction kinetics in the aqueous phase, taking into account the velocity distributions of the aqueous and organic phases through the inner and outer sides of a hollow fiber. The diffusional effect of each species on the extraction rates in the hollow fiber membrane extractor was determined. Furthermore, we confirmed the utility of the membrane extractor as an experimental apparatus for studying kinetics as well as of the proposed diffusion model for developing membrane extractors using hollow fiber modules.