Thermodynamic data bases for multivalent elements: An example for ruthenium

Conference · Sun Nov 01 00:00:00 EST 1987

OSTI ID:5752074

Rard, J A

A careful consideration and understanding of fundamental chemistry, thermodynamics, and kinetics is absolutely essential when modeling predominance regions and solubility behavior of elements that exhibit a wide range of valence states. Examples of this are given using the ruthenium-water system at 298.15 K, for which a critically assessed thermochemical data base is available. Ruthenium exhibits the widest range of known aqueous solution valence states. Known solid anhydrous binary oxides of ruthenium are crystalline RuO/sub 2/, RuO/sub 4/, and possibly RuO/sub 3/ (thin film), and known hydroxides/hydrated oxides (all amorphous) are Ru(OH)/sub 3/ . H/sub 2/O, RuO/sub 2/ . 2H/sub 2/O, RuO/sub 2/ . H/sub 2/O, and a poorly characterized Ru(V) hydrous oxide. Although the other oxides, hydroxides, and hydrous oxides are generally obtained as precipitates from aqueous solutions, they are thermodynamically unstable with regard to RuO/sub 2/(cr) formation. Characterized aqueous species of ruthenium include RuO/sub 4/ (which slowly oxidizes water and which dissociates as a weak acid), RuO/sub 4//sup -/ and RuO/sub 4//sup 2 -/ (which probably contain lesser amounts of RuO/sub 3/(OH)/sub 2//sup -/ and RuO/sub 3/(OH)/sub 2//sup 2 -/, respectively, and other species), Ru(OH)/sub 2//sup 2 +/, Ru/sub 4/(OH)/sub 12//sup 4 +/, Ru(OH)/sub 4/, Ru/sup 3 +/, Ru(OH)/sup 2 +/, Ru(OH)/sub 2//sup +/, Ru/sup 2 +/, and some hydroxytetramers with formal ruthenium valences of 3.75 greater than or equal to Z greater than or equal to 2.0. Potential pH diagrams of the predominance regions change significantly with concentration due to polymerization/depolymerization reactions. Failure to consider the known chemistry of ruthenium can yield large differences in predicted solubilities.

• Research Organization: Lawrence Livermore National Lab., CA (USA)
• DOE Contract Number: W-7405-ENG-48
• OSTI ID: 5752074
• Report Number(s): UCRL-96555-Rev.1; CONF-870594-1-Rev.1; ON: DE88004395
• Resource Relation: Conference: International conference on thermodynamics of aqueous systems with industrial applications, Warrenton, VA, USA, 10 May 1987
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
36 MATERIALS SCIENCE
RUTHENIUM
THERMODYNAMICS
AQUEOUS SOLUTIONS
CHEMICAL PROPERTIES
PH VALUE
REACTION KINETICS
SOLUBILITY
VALENCE
DISPERSIONS
ELEMENTS
KINETICS
METALS
MIXTURES
PLATINUM METALS
SOLUTIONS
TRANSITION ELEMENTS
052002* - Nuclear Fuels- Waste Disposal & Storage
360104 - Metals & Alloys- Physical Properties