1989 Volume 38 Issue 12 Pages 701-706
The suppression of extraction of micro-elements with an extractable macro-elements was investigated. The separation of micro-elements (ca. 10-4 M) was carried out based on the phenomena explained as common ions effect. Cadmium and zinc were used as the macro-elements. The maximum suppression effect was observed with 0.09 M Cd(II) and 0.5 M Zn(II) in 3.5 M HCl solution. Tributylphosphate (TBP) was used as an extraction solvent. Zinc and cadmium are extracted as chloro metal-acid complexes (H2ZnCl4 and H2CdCl4), which dissociated in the TBP phase after extraction from HCl solution. When the chloro metal-acid complexes formed with micro-elements also dissociated in the organic phase, the extraction of micro-elements was suppressed by macro-elements, while undissociated acid complexes were not suppressed. Therefore, the former can be separated from the latter. The dissociation of chloro metal-acid complexes was observed by measurement of specific conductivity in the organic phase. Sb(III), Ga(III), Mo(VI) and Fe(III) were extracted with 5 ml of TBP from 3.0 M HCl solution, separated from V(V) and Cu(II) remained in aqueous phase (25 ml) by addition of Cd(II) as macro-element. On the other hand, Zr(IV) was separated from Co(II) under conditions of 7 M HCl solution and 0.18 M Cd(II).
