Abstract
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 1H NMR analysis. The extraction of palladium(II) from 0.1 mol·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·L−1 aqueous solution of ammonia and 0.1 mol·L−1 thiourea in 0.1 or 1 mol·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.
Highlights
Demand for precious metals such as palladium(II), platinum(IV), gold(III) and rhodium(III) is still high as they are widely used in the automotive, chemical, electrical, glass, petroleum, jewelry, medical and biomedical industries
The aim of our study is to examine the extraction capabilities of the synthesized [PIP16]Cl for palladium(II) ions from hydrochloric acid solutions of various concentrations
The extent of palladium(II) extraction from 0.1 mol·L−1 HCl amounted to nearly 100%, while from 8 mol·L−1 HCl it decreased to approximately 10% (Fig. 2a)
Summary
Demand for precious metals such as palladium(II), platinum(IV), gold(III) and rhodium(III) is still high as they are widely used in the automotive, chemical, electrical, glass, petroleum, jewelry, medical and biomedical industries. As the natural resources of these metals are limited and depleting, the effective recycling of spent materials containing these precious metals, e.g. waste electronic and electrical equipment, is required. Journal of Solution Chemistry (2020) 49:486–503 used for the recovery of precious metals from natural and secondary raw materials [2,3,4,5]. Solvent extraction is one of the methods commonly used for recovery of metals from aqueous solutions. A perfect extractant should show the following characteristics [6, 7]:
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