B. Cote et Gp. Demopoulos, NEW 8-HYDROXYQUINOLINE DERIVATIVE EXTRACTANTS FOR PLATINUM-GROUP METALS SEPARATION .3. PT(IV) EXTRACTION EQUILIBRIA AND STRIPPING, Solvent extraction and ion exchange, 12(3), 1994, pp. 517-540
Studies of the extraction equilibria of platinum by chloroform solutio
ns of 7-substituted-8-hydroxyquinoline derivatives from aqueous chlori
de media demonstrated that Pt(IV) is extracted as the ion-pair PtCl62-
(H2Q+)2. The extraction equilibrium constants, log K(ex), were determi
ned to be log K(ex) = 3.48 and 3.62 for TN 1911 (an unsaturated and st
erically-hindered derivative) and TN 2336 (a saturated and sterically-
free derivative) respectively. It was found that PtCl62-(H2Q+)2 exhibi
ts an absorption band at 254.0 nm in chloroform solution. It was shown
that platinum extraction is influenced by both the extractant concent
ration and reagent structure. The individual roles of platinum, proton
and chloride ion concentration were quantified. It was found that pla
tinum extraction is exothermic since metal extraction decreases with t
emperature and an enthalpy change of -39.8 kJ/mole was determined. The
influence of pH on Pt(IV) stripping is also discussed. Finally, the r
espective extraction and stripping isotherms were established.