SEQUESTRATION OF THE TRIBUTYL-PHOSPHATE COMPLEX OF EUROPIUM NITRATE IN THE CLAY HECTORITE - A P-31 NMR-STUDY

The behaviour of organic complexes of actinides and lanthanides in cla ys plays an important role in environmental remediation. Application o f P-31 NMR to distinguish Eu(NO3)(3)-complexed tributyl phosphate from uncomplexed tributyl phosphate (TBP) facilitates an understanding of the fate of these species in the clay hectorite. Solution P-31 NMR stu dies show dramatic shifts of -156.0 to -172.9 ppm for Eu(NO3)(3) . 6H( 2)O dissolved in TBP at TBP:Eu ratios 1:1 to 1:2.5. Pure TBP exhibits a P-31 chemical shift of -0.3 ppm. Mixtures with higher TBP:Eu ratios display lines progressively downfield of -156.0 ppm, reflecting exchan ge of complexed and free TBP. The Eu(NO3)(3)-complexed TBP adsorbed in to hectorite displays a P-31 chemical shift of -180.7 to -193.8 ppm. C lays 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 attrib uted 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 sli ghtly 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. Neithe r of the latter two samples show indication of complex formation. The hectorite samples exposed to TBP or the complex display (001) d spacin gs of 17.9-18.4 Angstrom compared to 12.3-12.5 Angstrom for hectorite which has not been exposed to TBP.