2017 Volume 22 Issue 1_2 Pages 15-19
m-Phenylene diamine-containing compounds were synthesized via a one-pot process and subsequently used as new precipitating agents (PA1 and PA2). The precipitation of Pd and Pt was studied using PA1 and PA2 as metal precipitants. While PA1 exclusively precipitated Pd from a HCl solution containing Pd, Pt, and base metals, PA2 achieved precipitation of both Pd and Pt from the metal-containing HCl solution. Mutual separation of Pd and Pt was achieved by using PA1 and PA2 in the first and second precipitation steps, respectively. Separation tests at varying agent loadings revealed that Pd and Pt were precipitated by forming of an ion-pair composed of a metal chloro-complex anion (i.e., [PdCl4]2－ or [PtCl6]2－) and one precipitating agent molecule (i.e., divalent cation). The stoichiometric ratio of the ion-pairs was in agreement with the atomic ratios estimated from X-ray photoelectron spectroscopy results. Since the precipitation mechanism herein was based on the formation of an ion-pair, the cations of the precipitating agents only recovered Pd and Pt chloro-complex anions when the cations of the base metals were present in the solution. The different hydrophobicities of the precipitating agents enabled mutual separation of Pd and Pt.
