Palladium(II) extraction by pyridinecarboxylic acid esters

The commercial extractant Acorga CLX-50 and model individual di-2-ethylhexyl-pyridine-3,5-dicarboxylate and 2-ethylhexyl pyridine-3-carboxylate in toluene were used for palladium(II) extraction from aqueous HCl solutions. The studies of extraction rate and equilibrium were carried out in systems containing palladium(II) ions in 3.0, 0.1, and 0.1 M HCl in the presence of 0.5 M sodium chloride and 0.1 M HCl in the presence of 0.1 - 6.0 M lithium chloride and 0.1 M HCl in the presence 0.1 - 3.5 M sodium nitrate. The examined extractants can efficiently extract palladium(II) from aqueous hydrochloric acid and nitrate solutions. The extraction is slow and equilibrium is obtained after 2 hours. The best extraction of palladium(II) is observed from 0.1 M HCl solution in the presence 3.5 M sodium nitrate. A spontaneous transfer of palladium (II) to the toluene phase without any phase mixing is also observed. (author)