Extraction and separation of palladium(II), platinum(IV), gold(III) and rhodium(III) using piperidine-based extractants

Extraction of palladium(II) from hydrochloric acid media with novel piperidine-based extractants N-decylpiperidine (P-C10), N-dodecylpiperidine (P-C12), N-tetradecylpiperidine (P-C14) and N-hexadecylpiperidine (P-C16) has been investigated. Over 90% of palladium(II) from 0.1 M HCl solution can be effectively extracted with P-C12, P-C14 and P-C16 in toluene and the extraction equilibrium is achieved after 10 min. Increase in HCl concentration has a negative effect on the effectiveness of palladium(II) extraction. From among the examined stripping solutions the most effective are 0.5 M aqueous solution of ammonia and 0.1 M thiourea in 1 M HCl. The percentage of palladium(II) stripped from loaded organic phase (P-C12) reached nearly 100%. Also the selectivity of palladium(II) extraction over rhodium(III), platinum(IV) and gold(III) with the synthesized N-dodecylpiperidine (P-C12) has been investigated. The selectivity of extraction of palladium(II) over rhodium(III) from 0.1 and 3 M HCl with P-C12 was the best. Separation of palladium(II) from platinum(IV) or gold(III) is not so effective and it depends upon the acidity of aqueous solution. N-dodecylpiperidine also shows the extraction ability towards examined noble metal ions in the following order Au(III) > Pd(II) ~ Pt(IV) > > Rh(III) from 0.1 M HCl and Au(III) > Pt(IV) > Pd(II) > > Rh(III) from 3 M HCl. Palladium(II), platinum(IV) and gold(III) can be successfully separated through stripping from the loaded organic phase.