The Solvent Extraction of Iron(III) in Perchlorate Solutions Containing Chloride or Bromide Ions with 2-Thenoyltrifluoroacetone and Trioctylphosphine Oxide

Abstract

Abstract Iron(III) in aqueous solutions, in which [H+]=1.0m, [Na+]=3.0m, and [L−]+[ClO4−]=4.0m, where L− is a chloride or bromide ion, was extracted with thenoyltrifluoroacetone (TTA) in carbon tetrachloride or with trioctylphosphine oxide (TOPO) in hexane. From the TTA extraction, it was concluded that iron(III) formed the first and the second complexes with both chloride (β1=100.88 and β2=100.80) andbromide (β1=10−0.10 and β2=100.00) ions in the aqueous phase. The distribution data of iron(III) with TOPO were then explained in terms of the extraction of the ion-pairs, Fe(ClO4)3, FeL(ClO4)2, and FeL2(ClO4), by using these stability constants. When the aqueous phase contained only chloride or bromide ions, and no perchlorate ion, the increase in the extraction with the increase in the halide ion concentration was much larger than that observed when the aqueous phase contained both halide and perchlorate ions. From the determination of the extraction of hydrogen ions and halide ions with TOPO, the extracted species in the absence of a perchlorate ion were identified as FeL3 and/or HFeL4. It was concluded that the difference in the extraction of iron(III) when a perchlorate ion was present and when it was absent is mainly caused by (i) the extraction of perchloric acid, which combines with TOPO in the organic phase and interferes with the extraction of the iron(III) halide complexes, and (ii) the extraction of iron(III) species containing one or more perchlorate ions which are large enough to be extractable with TOPO in the organic phase.