Analytical Sciences

Selective Extraction of Palladium(II) with Theophylline Derivatives

Katsuya KAIKAKE and Yoshinari BABA

Department of Applied Chemistry, Faculty of Engineering, Miyazaki University, 1-1 Gakuenkibanadainishi, Miyazaki 889-2192, Japan

Theophylline derivatives with some kinds of alkyl chains were synthesized and used in extraction experiments involving metal ions. Theophylline derivatives have exhibited a high selectivity for palladium over other precious metals and base metals. The extraction of palladium from acidic chloride media has been investigated using theophylline derivatives (= (RN)_org) as extractants. Palladium(II) was found to be extracted with 7-octyltheophylline according to the following reaction: PdCl₂ + (2RN)_org < = > (PdCl₂(RN)₂)_org. The extraction equilibrium constant was determined to be K = 2.67 x 10⁸ (mol dm^-3)^-2. In addition, the stripping of palladium was performed to an extent of 100% by a single batchwise treatment with a 1.0 mol dm^-3 ammonia solution. The stoichiometric relation in the extraction of palladium was supported by an analysis using mass spectrometry.

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