Trace Metal Speciation by Capillary Electrophoresis Hyphenated to Inductively Coupled Plasma Mass Spectrometry: Sulfate and Chloride Complexes of Np(V) and Pu(V)

Abstract

In the framework of nuclear waste disposal, it is very important to well understand the behavior of actinides in the presence of the common environmental inorganic ligands such as sulfate and chloride. In this work, the AnO2SO4(-) and AnO2Cl 1-1 complexes have been evidenced by capillary electrophoresis-inductively coupled plasma mass spectrometry (CE-ICPMS) in perchlorate/chloride and in perchlorate/sulfate media for An = Np and Pu. Their binding constants have been measured: log beta(PuO2SO4(-))(0) = 1.30 +/- 0.11, log beta(PuO2Cl)(1 M NaCl) = -(0.40 +/- 0.07), log beta(NpO2SO4(-))(0) = 1.34 +/- 0.12, and log beta(NpO2Cl)(1 M NaCl) = -(0.40 +/- 0.07). These results are consistent with published values for Np(V). They confirm the expected analogy between Np(V) and Pu(V) for the weak bonding with chloride ligand, log10 beta(PuO2Cl) approximately = log10 beta(NpO2Cl), attributed to mainly electrostatic interactions. Conversely, a slight shift is observed for the bonding with sulfate ligand, log10 beta(NpO2SO4(-)) > log10 beta(PuO2SO4(-)), indicating that some covalency might stabilize the sulfate complexes.

Actinide oxalate complexes formation as a function of temperature by capillary electrophoresis coupled with inductively coupled plasma mass spectrometry

“…The pentavalent actinides (Np, and Pu) present similar values as expected between actinide at the same oxidation state [16,41].…”

“…U(VI), Np(V) and Am(III) stock solutions were used after conversion into the appropriate medium. The pentavalent plutonium was prepared according to a particular procedure described elsewhere [16]. The sample was then dissolved in 1.5 mL of S1 solution and 0.2 L of pure DMF was added to the sample.…”

Interaction of uranyl with Se(IV) and Se(VI) in aqueous acid solutions by means of capillary electrophoresis

“…where F is the Faraday constant, estimation of complex species mobility is possible [13]. An uncertainty of 725% is considered for the calculation of complex species mobility [13].…”

“…An uncertainty of 725% is considered for the calculation of complex species mobility [13]. The values of individual ion mobilities used for calculation and complex species mobilities estimated with Eqs.…”

“…The total expression for the second constant is: For experimental data fitting, two models were considered: (i) only equilibrium (13) takes place (formation only complex species with metal ion/ligand ratio 1:1) and (ii) two equilibria (13) and (15) occur (formation of two complex species with metal ion/ligand ratio 1:1 and 1:2). With the use of Eq.…”