Separation of Pd(II) and Pt(IV) from hydrochloric acid solutions by solvent extraction with Cyanex 301 and LIX 63

Abstract

In conventional solvent extraction processes, Pt(IV) and Pd(II) are separated by selective stripping from the loaded amines. Solvent extraction experiments were done to find extraction conditions to selectively extract Pd(II) over Pt(IV) from HCl solutions in the concentration range from 0.5 to 9 M. For this purpose, cationic, neutral and amines were employed to investigate the extraction behavior of the two metals from the single solution. LIX 63 and Cyanex 301 showed a selectivity for Pd(II) over Pt(IV) in the HCl concentration ranges tested in this work. The extraction percentage of Pd(II) by LIX 63 was greatly reduced as HCl concentration was higher than 7 M, while Pd(II) was completely extracted by Cyanex 301 even from 9 M HCl solution. FT-IR spectra of fresh and loaded Cyanex 301 showed that strong interaction occurred between Pd(II) complex and the PS bond in Cyanex 301. Therefore, it was very difficult to strip Pd(II) from the loaded Cyanex 301. The separation behavior of Pd(II) and Pt(IV) was compared between Cyanex 301 and LIX 63. Although the separation factor by Cyanex 301 was a little higher than that by LIX 63, LIX 63 was recommended as a suitable extractant for the selective extraction of Pd(II) over Pt(IV) owing to the ease of stripping of Pd(II) from the loaded LIX 63.