Sans study of aggregation of the complexes formed by selected metal cations and P,P'-di(2-ethylhexyl) ethane- and butane-diphosphonic acids

R. Chiarizia, V. Urban, P. Thiyagarajan, A. W. Herlinger

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31 Scopus citations

Abstract

The aggregation of several metal complexes formed during solvent extraction with P,P'-di(2-ethylhexyl) ethanediphosphonic acid, H2DEH[EDP], and by P,P'-di(2-ethylhexyl) butanediphosphonic acid, H2DEH[BuDP], in deuterated toluene, has been investigated by small angle neutron scattering (SANS). With H2DEH[EDP], the extraction of Ca(II), La(III) and U(VI) does not disrupt the cyclic hexameric structure of the ligand in solution. Fe(III) and Th(IV) complexes of H2DEH[EDP], on the other hand, exhibit a very modest tendency to aggregate but only at very high metal loading in the organic phase. With H2DEH[BuDP], the extraction of Ca(II), La(III), U(VI) and Th(IV) is not accompanied by significant aggregation of the metal complexes. The Fe(III)-H2DEH[BuDP] complexes, however, form long cylindrical aggregates similar to those previously observed with P,P'-di(2-ethylhexyl) methanediphosphonic acid, H2DEH[MDP]. The aggregation behavior of the various metal-extractant species is discussed in light of the information obtained from earlier solvent extraction, vapor pressure osmometry, and infrared spectroscopy studies.

Original languageEnglish
Pages (from-to)1171-1194
Number of pages24
JournalSolvent Extraction and Ion Exchange
Volume17
Issue number5
DOIs
StatePublished - 1999
Externally publishedYes

Funding

·Work performed under the auspices of the Office of Basic Energy Science, Divisions of Chemical Science and Material Science, U.S.Department of Energy, under contract number W-31-109-ENG-38. This work was supported by the U.S.Department of Energy, Office of Basic Energy Science under contract W-31-109-ENG-38. The Division of Chemical Science supported one of the authors (R.C.) for the part performed at the Chemistry Division of ANL and the Division of Material Science supported two of the authors (V.U. and P.T.) for the part performed at IPNS. We gratefully acknowledge the technical support provided by D.GWozniak and C. Ku at IPNS. We also thank Ed Huffof the AnalyticalChemistry Division for the ICP-AES analyses, and Ken Nash ofthe Chemistry Divisionfor useful discussions and advice.

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