Liquid-Liquid Extraction of Germanium(IV) with Trioctylamine from Aqueous Oxalic Acid Solution

Abstract

Extraction behavior of germanium(IV) from aqueous oxalic acid solution with trioctylamine (TOA) in xylene was investigated to determine the composition of a germanium(IV) species in the organic phase, The stoichiometry of the organic germanium (is, ) species was determined by the mole ratio method, the slope ratio method and the continuous variation method. Mole ratios of germanium (IV) to oxalate and oxalatogermanium (IV) complex to TOA were found to be 1: 3 and 1: 2 in all methods, respectively. The component ratios of the extracted germa- nium (IV) species were also investigated with extraction curves of germanium(IV) and oxalate. Component ratios of [oxalate/Ge(IV) ETOA/Ge(IV)] and [oxalate/TOA] in the organic germanium (IV) species were obtained to be 3.0, 2.1 and 1.5, respectively, at a constant mole ratio of 4.0 for [oxalate/Ge(IV)] in the aqueous. The effect of hydrogen ion concentration on the distribution ratio (D) of germanium (IV) was also determined. A slope of the plot of to D vs. pH of the aqueous phase was about 2.0 at the equilibrium. With respect to the effect of TOA concentration the plot of log D vs. log [R₃N]_(O) (R is octyl group) yield a slope of about 2.0. These results suggest that the oxalatogermanium (IV) species is associated with two molecules of R₃NH+. Based on these observations we come to a conclusion that the extracted germanium (IV) species in the organic phase predominantly consists of (R₃NH)₂Ge(C₂O₄)₃.