Liquid-Liquid Extraction of Trivalent Gallium, Indium and Thallium from Hydrochloric Acid Solutions by Trioctyl Phosphine Oxide.

Abstract

The extraction of trivalent gallium, indium and thallium from aqueous solutions containing hydrochloric acid and/or lithium chloride by trioctyl phosphine oxide (TOPO) in benzene has been investigated under different conditions. The organic extracts are also examined by infrared spectroscopy. As the results, it is found that although the extraction efficiency for metals of TOPO is in the order Tl>Ga>In, these extractions are expressed as the following equilibrium equations: GaCl3 (aq) + TOPO (org) GaCl3·TOPO (org); InCl3 (aq) + 2TOPO (org)-IInCl3·2TOPO (org); TlCl3 (aq) + 2TOPO (org)-ITlCl3·2TOPO (org) at low aqueous acidity, and TlCl3 (aq) + HCl (aq) + 2TOPO (org)-I HTlCl4-E2TOPO (org) at higher acidity. The extracted species consist of the complexes GaCl3·2TOPO, InCl3·2TOPO, Tl2CL6·4TOPO and H2Tl2CL8·4TOPO. By applying the trial and error method of least-squares analysis to the equilibrium equations for these extraction systems, the stability constants of the aqueous chloro complexes of trivalent gallium, indium and thallium have been determined.