Analytical Sciences

Abstract − Analytical Sciences, 16(2), 169 (2000).

Large Synergism of 3,5-Dichlorophenol in the Extraction ofGallium(III) with 2-Methyl-8-quinolinol Derivatives
Sung-Yong CHOI and Kousaburo OHASHI
Department of Environmental Sciences, Faculty of Science, Ibaraki University, Mito 310-8512, Japan
The large synergistic effect of 3,5-dichlorophenol (Hdcp) in the extraction of gallium(III) with 2-methyl-8-quinolinolderivatives (HA), such as 2-methyl-8-quinolinol (HMQ), 2-methyl-5-ethoxymethyl-8-quinolinol (HMO2Q), 2-methyl-5-butyloxymethyl-8-quinolinol (HMO4Q), and 2-methyl-5-hexyloxymethyl-8-quinolinol (HMO6Q), from a weakly acidicsolution into heptane and chloroform was investigated. The acid-dissociation constants of HA in an aqueous solution, thedistribution constants of HA between heptane and water, and the association constants between HA and Hdcp in heptanewere determined. The extractability of gallium(III) with HA increased with an increase in the hydrophobicity of HA.The extractability of gallium(III) with HA was remarkably enhanced upon the addition of Hdcp. The synergistic effect ofHdcp was quantitatively evaluated in terms of both a mixed ligand complex formation of Ga(dcp)(A)2 in an aqueousphase and the formation of an association-complex in an organic phase. The mixed-ligand complex formation and theassociation constant were determined at I = 0.1 M (H,Na)ClO4 (1 M = 1 mol dm-3) and 25กร. The compositions ofgallium(III)-HA complexes extracted in both the absence and presence of Hdcp were assigned to be Ga(OH)(A)2 andGa(dcp)(A)2.dcp, respectively. Moreover, the association constants of the synthesized Ga(OH)(MQ)2 with Hdcp inanhydrous chloroform were also determined by FT-IR spectrometry and the association-complexs were to beGa(OH)(MQ)2.mHdcp (m = 1, 2).