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

Abstract

Comparative adsorption behaviors of Eu(III) and Am(III) on thorium phosphate diphosphate (TPD), i.e., Th4(PO4)4P2O7, 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 (≡S3Am/Eu) and two ISCs (≡(XO)2Am/EuNO3 and ≡(YO)2Am/EuNO3) 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.

Exploring the Sorption Mechanism of Ni(II) on Illite: Batch Sorption, Modelling, EXAFS and Extraction Investigations

“…Ni(II) sorption decreased with the increase in ionic strength below pH 8.0. This suggested that IE or OSCs were dominant mechanisms in the low pH range because both are very sensitive to the ionic strength 36 . No significant difference was observed at different ionic strength conditions above pH 8.0.…”

Insight into the adsorption of europium(III) on muscovite and phlogopite: Effects of pH, electrolytes, humic substances and mica structures

“…Europium(III), i.e., Eu(III), is commonly considered as a chemical analogue for trivalent lanthanides (Ln) and actinides (An) due to the similar electronic and bonding properties (Takahashi et al, 1998a;Bradbury et al, 2002;Stumpf et al, 2002;Pan et al, 2017). As such, the retention of Eu(III) on various potential barriers has been extensively investigated to provide fundamental data concerning the performance assessment of HLW repositories and the remediation of radioactive contaminations (Fan et al, 2015; J o u r n a l P r e -p r o o f Fukushi et al, 2013;Jin et al, 2014;Pan et al, 2017;Qiu et al, 2018). It was reported that pH, ionic strength and NOMs largely influenced Eu(III) adsorption on muscovite, bentonite, illite, montmorillonite, granite, soil, etc.…”