Extraction mechanism, behavior and stripping of Pd(II) by pyridinium-based ionic liquid from hydrochloric acid medium

The hexadecylpyridinium chloride/chloroform system was employed for the Pd(II) extraction from hydrochloric acid medium. The effects of extraction time and material concentrations were examined for Pd(II) extraction. The anion-exchange mechanism of Pd(II) extraction by [Hpy]Cl was confirmed by Job's method, UV-Vis, infrared spectrum and H-1 NMR analysis. Thermodynamic parameters of the Pd(II) extraction reaction were obtained from the thermodynamics analysis, which illustrates that higher temperatures show a negative effect on the Pd(II) extraction. When the mole ratio of [Hpy]Cl to Pd(II) is above 4, the Pd(II) extraction yield (E%) is almost 100%. It also has high selectivity over some metals (Cu(II), Co(II),Ni(II), Fe(III), Al(III) and Sn(IV)). Moreover, oxalate is explored as a reducing agent for [Hpy](+)(2)[PdCl4](2-) complexes, by which Pd(II) is stripped in the form of palladium powders and [Hpy]Cl also can be recycled. Therefore, the method is an efficient, effective and highly selective approach to extract Pd(II) and recover metal palladium. (C) 2014 Elsevier B.V. All rights reserved.