Recovery of Pd(II) and Pt(IV) from leach liquors of automotive catalysts with calixarene-based di-n-alkylamino extractants in saturated hydrocarbon diluents

Abstract

The solubilities of eight p-di-n-alkylaminomethylcalix[4]arenes (alkyl: methyl to n-octyl = 1–8) in saturated hydrocarbon diluents commonly used as industrial diluents were investigated. Calixarene-based amino extractants with longer alkyl chains dissolved more readily in the saturated hydrocarbon diluents. Although 8 dissolved in kerosene, 1-decanol had to be added as a “phase modifier’” in order to inhibit the formation of a third phase on the Pd(II) and Pt(IV) extraction systems. The optimal mixing ratio of kerosene with 1-deconol was found to be 5:5 (v/v). Pd(II) and Pt(IV) were effectively recovered from the leach liquors of automotive catalysts using 8 and this kerosene/1-decanol mixed diluent. Furthermore, the results of reusability tests performed using the regenerated organic phase consisting of 8 and the kerosene/1-decanol mixed diluent indicate that Pd(II) and Pt(IV) were extracted at relatively high efficiencies even after five extraction/stripping cycles.