The selectivity of nickel over iron in the lix63-hdnns solvent extraction system

Yulian Zheng, K. Osseo-Asare

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The effects of the aqueous phase pH and the organic phase HDNNS concentration on the distribution coefficients of Ni and Fe in pure HDNNS or mixed LIX63-HDNNS systems have been investigated. With the mixed extractants, there is antagonistic extraction of iron below pH 1.4 whereas synergistic extraction occurs above this pH. At pH 2.5 and a fixed LIX63 concentration, iron distribution increases markedly in comparison with the oxime-free system and goes through a maximum with increase in HDNNS concentration. A similar behavior is shown by nickel at both pH 1.0 and 2.5. The log DFe versus pH plot gives a curve with a slope of two for the LIX63-HDNNS mixed system, which suggests that iron is extracted in the form of a species with an ionic charge of 2, probably Fe(0H)2+. The extracted complexes are proposed as Ni(H2L)3D2 where all three oxime molecules function as bidentate ligands, and Fe(OH)(H2L3D2 where one of the oxime molecules functions as a monodentate ligand. The Ni/Fe selectivity is high at low pH and changes mainly as a result of variations in the nickel distribution coefficient, but it is low at high pH because of the synergistic extraction of iron.

Original languageEnglish (US)
Pages (from-to)825-837
Number of pages13
JournalSolvent Extraction and Ion Exchange
Issue number6
StatePublished - Dec 1 1985

All Science Journal Classification (ASJC) codes

  • General Chemistry
  • General Chemical Engineering


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