Complexation
of Curium(III) with DTPA at 10–70
°C: Comparison with Eu(III)–DTPA in Thermodynamics, Luminescence,
and Coordination Modes
- Publication date
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Abstract
Separation
of trivalent actinides (An(III)) from trivalent lanthanides
(Ln(III)) is a challenging task because of the nearly identical chemical
properties of these groups. Diethylenetriaminepentaacetate (DTPA),
a key reagent used in the TALSPEAK process that effectively separates
An(III) from Ln(III), is believed to play a critical role in the An(III)/Ln(III)
separation. However, the underlying principles for the separation
based on the difference in the complexation of DTPA with An(III) and
Ln(III) remain unclear. In this work, the complexation of DTPA with
Cm(III) at 10–70 °C was investigated by spectrophotometry,
luminescence spectroscopy, and microcalorimetry, in conjunction with
computational methods. The binding strength, the enthalpy of complexation,
the coordination modes, and the luminescence properties are compared
between the Cm(III)–DTPA and Eu(III)–DTPA systems. The
experimental and computational data demonstrated that the difference
between Cm(III) and Eu(III) in the binding strength with DTPA can
be attributed to the stronger covalence bonding between Cm(III) and
the nitrogen donors of DTPA
