Local Structure Analysis of Strontium Sorption to Hydrous Manganese Oxide

Characterization of Sorbed Strontium on Monosodium Titanate

“…Some of the EXAFS studies that have characterized the environment of sorbed Sr 2+ on hydrous oxides of Fe and Mn observe a metal in the second coordination shell. 16,17 Because a metal was found in the second coordination environment, these studies refer to the nature of the sorption as being due to the ion exchange of hydrated Sr 2+ (Note: This conclusion is not consistent with the previous section that describes ion exchange in the strict sense. 16,17 These studies also report that they could fit Sr or Fe in the second shell over a range of surface Sr 2+ loadings and hence, these data present great confusion and about the quality of the XAFS data and the data analyses.…”

“…16,17 Because a metal was found in the second coordination environment, these studies refer to the nature of the sorption as being due to the ion exchange of hydrated Sr 2+ (Note: This conclusion is not consistent with the previous section that describes ion exchange in the strict sense. 16,17 These studies also report that they could fit Sr or Fe in the second shell over a range of surface Sr 2+ loadings and hence, these data present great confusion and about the quality of the XAFS data and the data analyses. 21 In contrast, other sorption studies with Sr 2+ sorbed on the FeOOH (goethite) do not observe a metal in the second coordination shell and conclude that outer sphere adsorption is operative.…”

“…10,11,12,13,14,15 Strontium K-edge XANES and XAFS techniques have been applied to study the bonding environment of sorbed, solution and solid phase Sr 2+ species. 16,17,18,19,20 Strontium-XANES studies have been performed with Sr 2+ -rich carbonates and Sr 2+ -containing silicates and the interpretations of spectra from sample treatments are generally qualitative. 20 This is because solution and solid phase Sr 2+ species are typically present in the +II oxidation state and large energy shifts for the XANES edge of Sr 2+ are usually not observed.…”

“…O'Day et al (2000) and others have included a third cumulant term (C3) in their fits for first shell Sr-O interactions to account for anharmonicity among light backscattering atoms Sr and O in aqueous environments. 16,17,18,19 For our studies, we will compare the results of our first shell Sr-O fits with and without the C3 term. It is our opinion that the reports that have excluded the C3 term during the data analyses are in error.…”

Mechanisms of Strontium and Uranium Removal from High-Level Radioactive Waste Simulant Solutions by the Sorbent Monosodium Titanate

“…7 Researchers have studied the local structural environments of sorbed Sr and sorbed U(VI) on a variety of surfaces using X-ray based techniques. 9,10,11,12,13,14,15,16,17,18,19,20,21,22 Most of these studies examined with naturally-occurring minerals under solution conditions relevant to geologic surface and subsurface environments. The Sr K-edge X-ray absorption fine-structure (XAFS) spectroscopic techniques have also been used to study the bonding environment of sorbed Sr 2+ species on metal oxides.…”