JRP CALL information
Supported By

European Commission

Short description of the work
The determination of complexation constants by traditional methods such as solvent extraction, potentiometry, spectrophotometry, and calorimetry can be quite time consuming, labor intensive, and typically require work with larger quantities of materials. Methods that minimize the time, effort, and use of hazardous and/or radioactive materials are more cost-effective, and improve safety. This project is focused on developing a different approach for determining complexation constants that is much more rapid than the more established methods, and that requires minimal volume of solution. In this work, capillary electrophoresis (CE) is used to correlate mobilities of metal-ligand complexes with solution conditions, including ligand concentration.
For this initial visit, we investigated the complexation constants between alpha-hydroxyisobutyric acid (HIBA) and actinides of various oxidation states in solvent media composed of water and methanol. CE was coupled with inductively coupled plasma mass spectrometry (CE-ICP-MS). CE-ICP-MS allows for the rapid, simultaneous detection of elements in solution matrices, such as the 10% (v/v) methanol media used in these experiments. The actinides used in the experiments were curium (III), plutonium (IV), neptunium (V), and uranium (VI). We were able to determine that mobilities of the actinides decreased with an increasing concentration of the ligand. This behavior indicates that the speciation of the each actinide is changing as the mobility is dependent on both the size and charge of the analyte. As the ligand concentration is increased, the prevalence of higher order species is increased, which in turn decreases the charge on the overall actinide-ligand complex as well as increasing the size of the complex.

The main goal of this work is to use the experimental data collected at INE to estimate stability constants in this mixed aqueous-methanol system. The experimental results are currently being evaluated for the estimation of the stability constants between the indicated actinides and HIBA.

Main visitor contact data
Name: Kevin Bennett
Organisation: Washington State University

JRP Identification
JRP nr: TALI-C03-04
JRP title: Rapid estimation of actinide complexation constants in mixed solvent media
JRP scope: Scope 1: Actinide separation chemistry

Visited Associated Pooled Facility
Visited APF during the stay: KIT-INE - Laboratories
Name of the APF Contact Person: Thorsten Schäfer

Other APF and organisation involved in the JRP
Other organisations involved: Washington State University (Dr. Sue Clark)
Other APF involved in the project:

Description of the work done at the associated pooled facility
Start date of the stay: 1/7/2015
End date of the stay: 2/10/2015
Quantity of access: 25
Access Unit: Days