Thermodynamic data of compounds and complexes of U, Np, Pu and Am with selected organic ligands

Abstract

A comprehensive literature review of thermodynamic data for compounds and complexes of actinides with oxalate, citrate, ethylenediaminetetraacetate (edta) and a-isosaccharinate has been carried out within the scope of the Thermodynamic Data Base project of the Organisation for Economic Co-operation and Development e Nuclear Energy Agency (OECD/NEA). Reliable values could be selected mainly for Am(III), Np(V) and U(VI) complexes, whereas serious data gaps were found for the tetravalent actinides. The redox states U(III), U(V), Pu(V), Am(V), Np(VI), Pu(VI) and Am(VI) are unstable in the presence of the selected organic ligands. Missing or unreliable data in these unstable redox states are of no importance from the viewpoint of application in environmental modelling studies. To cite this article: W.

Effect of Temperature on the Complexation of Uranium(VI) with Fluoride in Aqueous Solutions

“…ϑ is the ratio of the values of molality to molarity for the specific ionic medium and varies for different media and concentrations. For 1.0 mol·dm -3 NaClO 4 , logϑ is about 0.02 [24].…”

“…The SIT approach is originated from the Brφnsted-Guggenheim-Scatchard model [25, 26,27] and used to calculate the equilibrium constants at zero ionic strength [2,3,24]. For reactions 1 -4, the equilibrium constants at I = 0 (log β 0 ) are related to log β at other ionic strengths by the following equation:…”

“…where ΔZ for temperatures below 200 o C [24]. Besides, the values of (∂ε/∂T) p for the reactants and products may balance out each other so that Δε for many reactions remains approximately constant up to 100 o C [28,29].…”

Understanding the Solution Behavior of Minor Actinides in the Presence of EDTA4–, Carbonate, and Hydroxide Ligands

“…[1][2][3][4] Trivalent actinides behave as hard cations, and predominantly participate in ionic bonding with ligands that contain hard donor groups. 5 In the environment, polyaminocarboxylate donors can exist within humic substances, which are formed from the decomposition of organic matter.…”

Complexation of Lanthanides with Nitrate at Variable Temperatures: Thermodynamics and Coordination Modes

“…Even for 25 o C, thermodynamic parameters other than stability constants, e.g., enthalpy of complexation, are rarely available. 1,3,4,5 It is known that nitrate is a weak complexant for metal cations in aqueous solutions.…”