Comparison of the extraction behavior of metal ions by metal affinity ligands in an organic-aqueous two-phase system and in a liposome system

Hideto Nagami, Hiroshi Umakoshi, Toshinori Shimanouchi, Ryoichi Kuboi, Yoshinari Baba

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The interaction of various metal ions with simple metal affinity ligands, 3-(hexadecylthio)propionic acid (HTP) and 2-(hexadecylthio)benzoic acid (HTB), was investigated in an organic/aqueous two-phase system and in a liposome system. Both ligands exhibited a high silver(I) affinity at low pH in the organic/aqueous two phase system but low selectivity in the extraction of other transition metal ions such as Cu(II), Ni(II), Co(II), Zn(II), Cd(II), and Hg(II) above pH 6. On the other hand, remarkably different behavior for metal adsorption was observed in the liposome system with HTP and HTB. HTB lost the ability to interact with metal ions when modified on the liposome surface. This may be attributed to the formation of a hydrogen bond between the carboxyl group of the HTB and the phosphate group of the phospholipid. The HTP-modified liposome effectively adsorbed metal ions of the zinc family, such as Zn(II) and Cd(II), which could interact with the phosphate group of phospholipid, and also adsorbed those transition metal ions, which could be extracted in the organic/aqueous two-phase system. This may be caused by two functions of the liposome, i.e., a gate function for metal ions at the surface of the HTP-modified liposome and additional stabilization by interaction between Cu(II) and the phosphate group of the phospholipid.

Original languageEnglish
Pages (from-to)159-165
Number of pages7
JournalSolvent Extraction Research and Development
Publication statusPublished - 2004
Externally publishedYes


ASJC Scopus subject areas

  • Chemistry(all)
  • Filtration and Separation
  • Chemical Engineering(all)

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