Adsorption Characteristics of Trivalent Rare Earths and Chemical Stability of a Silica-Based Macroporous TODGA Adsorbent in HNO₃ Solution

Abstract

In order to separate trivalent minor actinides (Am and Cm) from high-level liquid waste generated in a nuclear fuel reprocessing process, a silica-based macroporous TODGA (N,N,N′,N′-tetraoctyl-3-oxapentane-1,5-diamide) adsorbent (TODGA/SiO₂-P) was prepared. In this study, the adsorption characteristics of some trivalent rare earths (Y, Nd, and Eu), whose separation behaviors were similar to those of the minor actinides from HNO₃ solution with the TODGA/SiO₂-P adsorbent, and the chemical stability of the adsorbent against the HNO₃ solution were evaluated experimentally. It was found that the adsorbent exhibited a quite strong adsorption especially for Y(III). The standard enthalpy change for the Y(III) adsorption was determined to be −2.5kJ·mol⁻¹ using the van't Hoff equation, which indicates that the adsorption was an exothermic reaction. The results of chemical stability experiments showed that the adsorbent had relatively excellent properties in long-time contact with the HNO₃ solution.

KEYWORDS:

• TODGA/SiO₂-P adsorbent
• trivalent rare earths
• adsorption characteristics
• chemical stability