Comparative adsorption of Eu(iii) and Am(iii) on TPD

Comparative adsorption behaviors of Eu( iii ) and Am( iii ) on thorium phosphate diphosphate (TPD), i.e. , Th 4 (PO 4 ) 4 P 2 O 7 , have been studied using a batch approach and surface complexation model (SCM) in this study. The results showed that Eu( iii ) and Am( iii ) adsorption increased to a large extent with the increase in TPD dose. Strong pH-dependence was observed in both Eu( iii ) and Am( iii ) adsorption processes, suggesting that inner-sphere complexes (ISCs) were possibly responsible for the adsorption of Eu( iii ) and Am( iii ). Meanwhile, the adsorption of Eu( iii ) and Am( iii ) decreased to a different extent with the increase in ion strength, which was possibly related to outer-sphere complexes and/or ion exchange. In the presence of fulvic acid (FA), the adsorption of Eu( iii ) and Am( iii ) showed high enhancement mainly due to the ternary surface complexes of TPD-FA-Eu 3+ and TPD-FA-Am 3+ . The SCM showed that one ion exchange (&z.tbd;S 3 Am/Eu) and two ISCs (&z.tbd;(XO) 2 Am/EuNO 3 and &z.tbd;(YO) 2 Am/EuNO 3 ) seemed more reasonable to quantitatively describe the adsorption edges of both Eu( iii ) and Am( iii ). Our findings obviously showed that Eu( iii ) could be a good analogue to study actinide behaviors in practical terms. However, it should be kept in mind that there are still obvious differences between the characteristics of Eu( iii ) and Am( iii ) in some special cases, for instance, the complex ability with organic matter and adsorption affinity to a solid surface. Comparative adsorption behaviors of Eu( iii ) and Am( iii ) on thorium phosphate diphosphate (TPD), i.e. , Th 4 (PO 4 ) 4 P 2 O 7 , have been studied using a batch approach and surface complexation model (SCM) in this study.