Solvent extraction of noble metals by formazans-I Comparative study on the extractability of Pt(IV), Pd(II) and Ag(I) by formazans combined with a liquid anion-exchanger.
The extraction properties of ion-pairs composed of quaternary ammonium cations and a sulphonated formazan were compared with those of an unsulphonated formazan, for various solvent media. In dichloromethane the combined system behaves as a "coloured anion-exchanger", with displacement of the sulphonated formazan, whereas in toluene Pd(II) and Ag(I) are extracted as the metal formazan chelates from aqueous medium. The rates of extraction are remarkably higher than with the simple extractants. Because of the higher stability only the simple chelating extraction systems afford satisfactory separation of Pd(II) from excess of Pt(IV) and of Ag(I) from Cu(II). The extracted metals can be stripped and the extractant regenerated.
Grote
M
M
Fachbereich Chemie und Chemietechnik, "Angewandte Chemie", Universität-GH Paderborn, Warburger Strasse 100, D-4790 Paderborn, Bundesrepublik Deutschland.
Hüppe
U
U
Kettrup
A
A