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.
ASJC Scopus subject areas
- General Engineering
- Physical and Theoretical Chemistry