The Solvent Extraction of Zinc(II) in Sodium Perchlorate-halide Solutions with Trioctylphosphine Oxide

Abstract

Abstract The solvent extraction of zinc(II) in 1m sodium perchlorate ionic media containing chloride, bromide, or iodide ions at 25°C was determined as a function of the halide-ion (X−) concentration by using the zinc-65 tracer. From the extraction data with isopropyltropolone (IPT) in chloroform, the formation of the ZnX+ complex was observed, but the stability constants of these complexes were not large (ZnCl+: β1 is 100.00, ZnBr+: β1 is less than 10−0.5and the formation of ZnI+ is negligible), and the higher complexes were negligible in all cases. The extraction of zinc(II) from these media with methylisobutylketone (MIBK) was not effective, although the extracted species could be identified as ZnX2. The extraction with trioctylphosphine oxide (TOPO) in hexane, on the other hand, was much better than that with MIBK. From the distribution ratio determined as a function of the halide and TOPO concentrations, the extracted species were concluded to be Zn(ClO4)2(TOPO)4, ZnX(ClO4)(TOPO)3, and ZnX2-(TOPO)2. The extraction constants for these species were determined by a graphic analysis of the data, and it was concluded that the extractabilities are larger in the order: iodide>bromide>chloride. From these data, it is clear that, if a suitable and effective neutral extractant is employed, the extractions of the above complexes are possible, even from aqueous solutions in which practically no complex is formed.