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

摘要

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 inves-tigated 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 > TI > In at higher acidities, and of TOA in the order Tl > Ga > In. Further the following equilibrium equations were given for the extraction by TBP: GaCl_3(aq) + 2TBP(org) <- -> GaCl_3 centre dot 2TBP(org) ;InCl_3(ag) + 3TBP(org) <- -> InCl_3 centre dot 3TBP(org) ;TlCl_3(aq) + 2TBP(org) <- ->TlCl_3 - 2TBP(org) at low aqueous acidity and TICl_3(aq) = HCl(aq)+ 2TBP(org)<- -> HTlCl_4 centre dot 2TBP(org) at higher acidities, and in addition with increasing the concentration of thallium in aqueous phase TICl_2(aq) + HCl(aq) + 3TBP(org) -><- HTlCl_4 3TBP(org). For the extraction by TOA, MCl_2(aq) + nR_3NHCl(org) -><- (R_3NH)_nMCl_(3+n)(org) where M = Ga, In and Tl. and n = 1 for Ga or Ti 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( ifi) from aqueous solutions at higher acidities bv TOA. Although the extraction efficiency for trivalent 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.