Abstract
Extraction equilibria of palladium (II) from acidic chloride media were studied at 303 K to examine the potential use of three kinds of xanthine derivatives (=RN), caffeine, theophylline, and theobromine, as selective extractants. Xanthine derivatives have exhibited high selectivity for palladium (II) over copper (II) and platinum (IV) . The extraction reaction of palladium (II) was elucidated by examining effects of hydrochloric acid, chloride ion, hydrogen ion, and extractant concentration as PdCl2+2RN ⇔ PdCl2 (RN) 2 for caffeine, theophylline, and theobromine derivatives Using the xanthine derivatives, palladium (II) was extracted selectively from mixtures containing the 25-fold amounts of copper (II) or platinum (IV) . In addition, it was easy to strip the palladium (II) extracted with the xanthine derivatives using an ammonia or thiourea solution.The stripping percentage of palladium (II) was more than 60% using single batchwise processing.
