Liquid-Liquid Extraction of Trivalent Gallium, Indium and Thallium from Hydrochloric Acid Solutions by Tributyl Phosphate and Trioctylamine.

Abstract

The extraction of trivalent gallium, indium and thallium from aqueous solutions containing hydrochloric acid and/or lithium chloride by tributyl phosphate (TBP) and trioctylamine (TOA) in benzene has been investigated under different conditions. As the results, it was found that the extraction efficiency for metals of TBP is in the order Tl<Ga<In at low aqueous acidity and Ga<Tl<In at Niger acidities, and of TOA in the order Ti<Ga<In. Further the following equilibrium equations were given for the extraction by TBP: GaCl3(aq)+2TBP(org)=GaCl3·2TBP(org); InCl3(ag)+3TBP(org)=InCl3·3TBP(org); TlCl3(aq)+2TBP(org) TlCl3·2TBP(org) at low aqeuous acidity and TlCl3(aq)+HCl(aq)+2TBP(org)=HTlCl4·2TBP(org) at higher acidities, and in addition with increasing the concentration of thallium in aqueous phase TlCl3(aq)+HCl(aq)+3TBP(org) HTlCl4·3TBP(org). For the extraction by TOA, MCl3(aq)+nR3NHCl(org)=(R3NH)nMC13+n(org) where M=Ga, In and Tl, and n=1 for Ga or Tl and 2 for In, respectively. It was therefore seen that the distribution behaviour by TBP and TOA corresponds to that by TOPO, except for the extraction of thallium (III) from aqueous solutions at higher acidities by TOA. Although the extraction efficiency for trivallent metals of TOA is higher than that of TBP, the characteristic of TOA and TBP appears in the extraction from aqueous solutions at low and higher acidities, respectively.