Interfacial Adsorption of Iron(II)–4,7-Diphenyl-1,10-phenanthroline Complex in Ion-Association Extraction Systems

The interfacial adsorptivity of an iron(II)–4,7-diphenyl-1,10-phenanthroline (DPP) complex in chloroform/aqueous salt solution systems was investigated by means of a high-speed stirring method and interfacial tension measurements. The interfacial spectra observed in the stirred system suggested that the adsorbed species at the interface is the tris-DPP complex. A minor effect of the anion concentration on the adsorptivity suggested that the tris-complex adsorbed as an ion-pair in a 0.1 M anion concentration. The interfacial adsorption of the ion-pair under stirring was analyzed by the Langmuir isotherm. The adsorptivity increased, depending on the counter ions, in the order ClO4−hydration energies of these anions.