Palladium(II) extraction from nitric acid solutions byLIX34

Abstract

BACKGROUND: Sulphur-containing reagents are known to extract Pd(II) very efficiently. Among them, 8-(alkarylsulphonamido) quinolines have shown a high extractive ability towards several metal ions. In this work, the distribution equilibria of Pd(II) from nitric acid solutions of 1.0 mol L −1 ionic strength by LIX 34 dissolved in toluene have been studied as a function of both extractant and metal concentration, equilibrium pH and nitrate ion concentration. The effect of the alkyl chain length of the extractant molecule on the extraction of Pd(II) has also been investigated. RESULTS: The extraction of Pd(II) from acidic solutions by LIX 34 is slow but low concentrations of the extractant are required for quantitative extraction. It does not depend on pH in the 1-2.3 range whereas nitrate ion concentration has little influence on the extraction process. The synthesized compound 4-methyl-N-8-quinolinylbenzenesulphonamide, which presents a structure very close to 4-dodecyl-N-8-quinolinylbenzenesulphonamide, which is the active component in LIX 34, shows the same extraction ability towards palladium. CONCLUSIONS: The experimental data have been treated numerically and can be explained by assuming the formation of the complexes PdL 2 (log k 020 = 10.46 ± 0.12) and Pd(NO 3 )L (log k 110 = 4.99 ± 0.18), the former being the predominant species.