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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.

The complexation between uranium() and acetate in 1.05 mol kg Ϫ1 NaClO 4 was studied at variable temperatures (25, 35, 45, 55 and 70 ЊC). The formation constants of three successive complexes, UO 2 (OOCCH 3 ) ϩ , UO 2 (OOCCH 3 ) 2 and UO 2 (OOCCH 3 ) 3 Ϫ , and the molar enthalpies of complexation were determined by potentiometry and calorimetry. Extended X-ray Absorption Fine Structure Spectroscopy (EXAFS) provided structural information to identify the coordination modes of the acetate in the complexes in solution, which helped to interpret the trends in the enthalpy and entropy of the complexation. The effect of temperature on the stability of the complexes is discussed in terms of the electrostatic model.

The microstructure, physical characteristics, corrosion behavior, and reactivity of zerovalent iron nanoparticles synthesized on a support (primarily a nonporous, hydrophobic polymer resin) were studied. The remediation of groundwater by zerovalent iron in in situ permeable reactive barriers relies on the redox reaction between metallic iron and a reducible contaminant. Decreasing the size of the iron particles and dispersing them on a support increases the specific surface area of the iron, as well as the ratio of surface to bulk iron atoms, and should thereby increase both the reaction rate and the fraction of iron atoms available for the reaction. Borohydride reduction of aqueous ferrous sulfate gives supported iron nanoparticles, 10−30 nm in diameter, which consist of 85% zerovalent iron by weight. These materials (“ferragels”) are stable in air and have corrosion behavior comparable to iron filings. Interestingly, the presence or absence of a support, as well as the boron remaining from the borohydride reduction process, influences the electrochemical corrosion rate of the composite materials. Supported and unsupported zerovalent iron nanoparticles are superior to iron filings in both terms of initial rates of reduction and total moles of contaminants (Cr(VI), Pb(II), TcO4 -) reduced per mole of iron. The enhanced reactivity and passive corrosion behavior of these materials should make them good candidates for use in permeable reactive barriers.