2003 Volume 52 Issue 9 Pages 775-780
The extraction of gallium(III) with 8-quinolinol derivatives (HA), such as 5-(2,2,2-trifluoroethoxymethyl)-8-quinolinol (HFO2Q) and 5-(ethoxymethyl)-8-quinolinol (HO2Q), from a weakly acidic solution into chloroform, was investigated both in the absence and presence of 3,5-dichlorophenol (Hdcp) as a synergist. The acid-dissociation constants of HA in an aqueous solution and the distribution constants of HA between chloroform and water were determined. Although HFO2Q has a trifluoroethoxymethyl group, which is more hydrophobic than an ethoxymethyl group, the distribution constant of HFO2Q was found to be lower than that of HO2Q. HFO2Q exhibited a higher extractability toward gallium(III) than 8-quinolinol and HO2Q. The extractability of gallium(III) with HA was enhanced upon the addition of Hdcp due to the formation of an association complex between Ga(A)3 and Hdcp. The compositions of gallium(III)-HA complexes extracted both in the absence and presence of 3.00×10−4∼3.00×10−2 mol dm−3 Hdcp were assigned to be Ga(A)3 and Ga(A)3•nHdcp (n = 1, 2), respectively. However, the formation of Ga(A)3•2Hdcp was not observed in the HFO2Q system, suggesting that the association of the second Hdcp with Ga(FO2Q)3•Hdcp was interfered by the trifluoroethoxymethyl group of HFO2Q.
