Palladium(II) extraction and extractant adsorption at a liquid/liquid interface

Interfacial tension isotherms were determined for individual palladium(II) extractants and interpreted. The following extractants were considered: 4-alkylphenylamines containing from 6 to 14 carbon atoms in the alkyl group, dihexylsulfide, 2-hydroxyethyldecyl sulfide and its partly fluorinated derivative, decylnicotiniate and N,N-dihexylpyridine-3-carboxamide. 4-Alkylphenylamines exhibited significantly stronger interfacial activity than did the other extractants. They adsorbed at the hydrocarbon/water interfaces already at concentrations 10(-5) M and permit to decrease the interfacial tension to 5 mN m(-1). As a result, they can be used as a phase transfer catalyst to increase the rate of palladium(II) extraction with other extractants. When used alone, the initial rate of extraction increases with the extractant increasing hydrophobicity, thus in the order of increased interfacial activity.