Efficiency and Mechanism of Palladium(II) Extraction from Chloride Media with N-Hexadecylpiperidinium Chloride

摘要

N-hexadecylpiperidinium chloride ([PIP16]Cl) has been synthesized and examined as a reagent for extractive recovery of palladium(II) from hydrochloric acid solutions. The effect of the contact time between the two phases, temperature and the concentration of palladium(II) ions, the extractant and HCl, were also evaluated. The anion-exchange mechanism of palladium(II) extraction with [PIP16]Cl was confirmed by Job's method, UV-VIS, IR and H-1 NMR analysis. The extraction of palladium(II) from 0.1 mol center dot L-1 HCl solution with [PIP16]Cl in toluene was very effective and amounted to almost 100%. Increases in both HCl and NaCl concentrations and increasing temperature had negative effects on the effectiveness of palladium(II) extraction. [PIP16]Cl also exhibited selectivity to extraction of palladium(II) over some other metals: rhodium(III), iron(III), aluminium(III), copper(II) and lead(II). From among the examined stripping solutions the most effective were 0.5 mol center dot L-1 aqueous solution of ammonia and 0.1 mol center dot L-1 thiourea in 0.1 or 1 mol center dot L-1 HCl. The percentage of palladium(II) stripped from loaded organic phase reached nearly 100%. The feasibility of regeneration of [PIP16]Cl and its reuse in subsequent extractions was also investigated.