2025 年 32 巻 1 号 p. 31-41
In this study, a new extractant has been developed for mutual separation of Cu(II) / Fe(III) and Cd(II) / Zn(II) from acidic media. These metals are mainly discharged from smelting and refining processes of copper, zinc, and lead. However, the mutual separation of these metals is difficult due to their similar chemical properties. In order to separate these metals, isooctyl thioglycolate (IOTG) which has carbonyl and thiol groups was proposed as a new extractant. Furthermore, 1-dodecanethiol (DOTH) with only a thiol group was used for comparison. We found that IOTG in toluene can selectively separate Cu(II) over Fe(III) and Cd(II) over Zn(II). We paid attention to the selective extraction of Cd(II) with high toxicity and examined the extraction equilibria of Zn(II) and Cd(II) in detail. These extraction equilibria are determined by the conventional slope analysis method from 1 M aqueous ammonium nitrate solution. It was found that the selective extraction of Cd(II) over Zn(II) is due to the formation of the binuclear Cd(II) complexes while Zn(II) is extracted as the mononuclear complex. Furthermore, the stripping of Cd(II) and Zn(II) extracted into the organic phase was achieved using appropriate concentrations of various acids.
