You are here:
Characterization And Dissolution Properties Of Ruthenium Oxides
Citation:
LUXTON, T. P., M. J. Eick, AND K. G. SCHECKEL. Characterization And Dissolution Properties Of Ruthenium Oxides. JOURNAL OF COLLOID AND INTERFACE SCIENCE. Elsevier BV, AMSTERDAM, Netherlands, 359(1):30-39, (2011).
Impact/Purpose:
The objectives of the current study are to synthesize hydrous ruthenium oxide (RuO2•1.10H2O) via forced hydration and oxidation, and synthesize ruthenium oxide (RuO2) by heat treatment of the hydrous-oxide phase. The resulting solid materials were extensively characterized to determine the chemical formula for the solid material, crystalline structure, surface area and ruthenium oxidation state. The surface charging characteristics, surface acidity constants, and points of zero charge will be determined for the two materials in order to assess chemical reactivity and surface charge in the environmental pH range (3-10). Finally, dissolution studies will be conducted in the presence of hydrochloric acid, sodium hydroxide, oxalate, and ascorbate to determine the dissolution behavior of ruthenium oxides in adverse pH environments and in the presence of metal chelating ligands. Results from the current work will help to establish under what environmental conditions ruthenium oxides can be used as metal oxide sorbent materials.
Description:
Ruthenium oxides (RuO2•1.10H2O and RuO2) have been synthesized by forced hydrolysis and oxidation of ruthenium chloride. The resulting materials were extensively characterized to determine the crystallinity, surface area, and ruthenium oxidation state of the material. Surface charging experiments indicate a large quantity of reactive functional groups for both materials 50 µmol m-2 for RuO2•1.10H2O and 20 µmol m-2 for RuO2 and a decrease in the acidity of the surface functional groups with crystallization of the hydrous oxide. Dissolution studies conducted in acidic and basic pH environments indicate Ru-oxides are insoluble in 0.1 M HCl and slightly soluble in 0.1 M NaOH. Oxalate and ascorbate (5 mM) promoted dissolution of RuO2•1.10H2O demonstrated an increase in dissolution rates with decreasing pH and ligand surface coverage. XPS analysis of the RuO2•1.10H2O surface after ligand promoted dissolution revealed the reduction of Ru(IV) to Ru (III) indicating that both ascorbate and oxalate reductively dissolve RuO2•1.10H2O. Dissolution experiments with RuO2 resulted in dissolution only for 5 mM oxalate at pH 3. Dissolution rates calculated for RuO2•1.10H2O and RuO2 are compared with previously published dissolution rates for iron oxides, demonstrating an order of magnitude decrease in the oxalate and ascorbate promoted dissolution.
