Selective Extraction of Indium(III) and Gallium(III) with 2-Ethylhexyl Thioglycolate

Abstract

Extraction selectivity of In(III) and Ga(III) was investigated using 2-ethylhexyl thioglycolate (EHTG) with a thiol group and an oxygen atom to recover these metals from zinc refinery residue and waste solar panels. The extraction order with EHTG was Cu(II)>In(III)>Ga(III)>Zn(II), while Al(III) was hardly extracted at all. While In(III) and Ga(III) were not extracted at all with 1-dodecanethiol (DDT) with contains only a thiol group although Zn(II) and Cu(II) were extracted. This indicates that the oxygen atom in the EHTG ester plays an important role in the extraction of these metals. The mutual separation of In(III), Ga(III), Zn(II) and Cu(II) is possible in almost one step with EHTG. The extraction equilibria of In(III) and Ga(III) with EHTG are also discussed. Furthermore, the stripping of In(III) and Ga(III) extracted into the organic phase was achieved using appropriate concentrations of NaOH and acids.