The aqueous geochemistry of the rare-earth elements and yttrium

The works performed in the Separation Chemistry Group of the Chemistry Division of Argonne National Laboratory on the transport and separation properties of supported liquid membranes (SLM) are reviewed. The models and equations which describe the permeation through SLMs of metal species are described. These models have been tested with various carriers absorbed on flat-sheet and hollow-fiber SLMs by measuring the permeation of several metal species of hydrometallurgical and nuclear interest. An equation for the separation factor of metal species in SLM processes and examples of separations of metal ions are reported. The possibility of bypassing the single stage character of SLM separations by using multilayer composite SLMs, arranged in series, is also analyzed. Finally, the factors which control the stability of SLMs are briefly discussed.

Separation of Metal Species by Supported Liquid Membranes

U, Np, and Pu LII,III-edge X-ray absorption fine structure (XAFS) spectra were collected for the UO22+, NpO2+, Np4+, and Pu3+ ions as a function of chloride concentration in aqueous solution. At low chloride concentration, the hydration numbers and corresponding bond lengths for the different ions are as follows:  UO22+, N = 5.3, R = 2.41 A; NpO2+, N = 5.0, R = 2.50 A; Np4+, N = 11.2, R = 2.40 A; Pu3+, N = 10.2, R = 2.51 A. As the Cl- concentration increases, inner-sphere Cl- complexation occurs, resulting in a decrease in the hydration numbers and an expansion of the actinide−oxygen (water) bond lengths. The Pu3+ ion shows only a decrease in hydration number (40%) and no inner-sphere Cl- complexation for [Cl-] < 14 M. For concentrations up to 10−14 M Cl-, the average Cl- coordination numbers and bond lengths are as follows:  UO22+, N = 2.6, R = 2.73 A; NpO2+, N = 1.0, R = 2.84 A; Np4+, N = 2.0, R = 2.61 A. Structural changes are observed in the near-edge spectral region as shown by significant changes in...

Investigation of Aquo and Chloro Complexes of UO22+, NpO2+, Np4+, and Pu3+ by X-ray Absorption Fine Structure Spectroscopy

Preface. Acknowledgements. Foreword. I. Introductory material. Introduction Standards, conventions, and contents of tables. II. Tables of selected data. Selected neptunium data. Selected plutonium data. Selected auxiliary data. III. Discussion of neptunium data selection. Elemental neptunium. Neptunium aqua ions. Neptunium oxygen and hydrogen compounds and complexes. Neptunium group 17 (halogen) compounds and complexes. Neptunium group 16 compounds and complexes. Neptunium group 15 compounds and complexes. Neptunium group 14 compounds and complexes. Neptunium group 2 (alkaline-earth) compounds. Neptunium group 1 (alkali) compounds. IV. Discussion of plutonium data selection. Elemental plutonium. Plutonium aqua ions. Plutonium oxygen and hydrogen compounds and complexes. Plutonium group 17 (halogen) compounds and complexes. Plutonium group 16 compounds and complexes. Plutonium group 15 compounds and complexes. Plutonium group 14 compounds and complexes. Plutonium group 2 (alkaline-earth) compounds. Plutonium group 1 (alkali) compounds. Bibliography. List of cited authors. V. Appendices. Discussion of selected references. Ionic strength corrections. Assigned uncertainties. Index.

Chemical thermodynamics of neptunium and plutonium

Kinetics of aqueous phase reactions relevant for atmospheric chemistry.

I. EXTRACTING REAGENTS In the present review, dealing with the kinetics of solvent extraction of metal species, we will consider biphasic systems consisting of: 1. An aqueous electrolyte solution containing a metal cation which, according to the nature and composition of the electrolyte, can exist either as a free (hydrated) ion or as neutral, positively or negatively charged complex species 2. An organic phase which is a solution, in a water-immiscible organic diluent, of an organic molecule called extractant; only organic diluent not exhibiting appreciable extraction properties by themselves will be considered; the extractant will instead be a molecule capable of reacting with the aqueous metal species, transferring them into the organic phase; this reactivity is conferred to the extractant by the presence of a functional group which has binding properties with respect to the metal species; the only purpose of the diluent will then be that of dissolving the extractant and possibly to improve its physica...

R. Chiarizia

Papers

The Kinetics of Metal Solvent Extraction

Extraction selectivity of organic solutions of a cyclic polyether with respect to the alkali cations

A simple purification method for the liquid cation exchanger dinonylnaphthalene sulfonic acid (DNNSA)

Interfacial behaviour of dinonylnaphthalenesulfonic acid at the toluene-HClO4 interface

Liquid ion exchange selectivity of dinonylnaphthalenesulfonic acid (HD) with respect to some lanthanide and actinide ions