Sequestration of the tributyl phosphate complex of europium nitrate in the clay hectorite. A 31P NMR study

C. J. Hartzell, S. W. Yang, R. A. Parnell, D. E. Morris

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Abstract

The behaviour of organic complexes of actinides and lanthanides in clays plays an important role in environmental remediation. Application of 31P NMR to distinguish Eu(NO)3)3-complexed tributyl phosphate from uncomplexed tributyl phosphate (TBP) facilitates an understanding of the fate of these species in the clay hectorite. Solution 31P NMR studies show dramatic shifts of -156.0 to -172.9 ppm for Eu(NO3)36H2O dissolved in TBP at TBP:Eu ratios 1:1 to 1:2.5. Pure TBP exhibits 31P chemical shift of -0.3 ppm. Mixtures with higher TBP:Eu ratios display lines progressively downfield of -156.0 ppm, reflecting exchange of complexed and free TBP. The Eu(NO3)3-complexed TBP adsorbed into hectorite displays a 31P chemical shift of -180.7 to -193.8 ppm. Clays adsorbed with solutions that are 3.1, 5:1 and 7:1 TBP:Eu display peaks due to complex as well as peaks in the range -4 to -6 ppm attributed to uncomplexed TBP. No evidence of exchange is observed. Spectra of the TBP-adsorbed clay give a TBP line at -0.7 ppm which changes slightly to --5.0 after exchange with Eu(NO3)3. The Eu(NO3)3-exchanged hectorite displays a line at -17.6 ppm after adsorption of TBP. Neither of the latter two samples show indication of complex formation. The hectorite samples exposed to TBP or the complex display (001) d spacings of 17.9-18.4 A compared to 12.3-12.5 A for hectorite which has not been exposed to TBP.

Original languageEnglish (US)
Pages (from-to)4205-4210
Number of pages6
JournalJournal of physical chemistry
Volume99
Issue number12
DOIs
StatePublished - Jan 1 1995

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ASJC Scopus subject areas

  • Engineering(all)
  • Physical and Theoretical Chemistry

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