The Behavior of Indium(III) Complexes in Several Distribution Systems. II. The Extraction of Indium(III) Halide and Thiocyanate Complexes into 4-Methyl-2-Pentanone, 4-Methyl-2-Pentanol, or Nitrobenzene

Abstract

Abstract The solvent extraction of indium(III) from a bromide, iodide, or thiocyanate solution into 4-methyl-2-pentanone(MIBK), 4-methyl-2-pentanol(hexol), or nitrobenzene was determined by using a 114mIn tracer. The extraction was, in general, most effective with MIBK and poorest with nitrobenzene, except from iodide solutions. The extraction with a certain solvent was always better from iodide solutions than from bromide solutions. The extraction from thiocyanate solutions was better than that from iodide solutions in some cases, but it was poorer in other cases, and it was better than that from bromide solutions except with nitrobenzene. Furthermore, it was found that the distribution ratio, determined as a function of the ligand concentration, was always poorer when the aqueous phase contained only the sodium salt of these ligands than when it was 4m Na(X, ClO4) (where X denotes the ligand anion). The extractions from 4m Na(X, C1O4) were analyzed by using the stability constants for the indium complexes with these ligands in the aqueous phase, and the extraction equilibria were determined. From these results, it was concluded that these polar solvents extract not only the uncharged complex, InX3, but also the cationic and/or anionic indium complexes as ion-pairs, with the oppositely charged ions in the background salt, and that, in some cases, the solvent extracts only charged indium species. Thus, the difference in the distribution ratio in the presence and in the absence of the background sodium perchlorate was concluded to be caused not only by the change in the activities due to the change in the total salt concentration, but also by the extraction of ion-pairs of charged indium(III) species, which should be very much enhanced by the presence of the bulk perchlorate.