Na K-edge XANES spectra of minerals and glasses

Acid transformation of bauxite residue: Conversion of its alkaline characteristics

“…The local ordering around Na (Na is in a tetrahedral position surrounded by one CO3 at 2.701 Å and three O at 2.398 Å in a trigonal pyramid) did not change in residues [64]. Absorption peaks of cancrinite suggested that the chemical speciation of Na in residues was consistent with BR, proving that alkaline cancrinite dominated Na speciation in TBRs, and further confirms that the three acid treatments and gypsum combination did not transform its chemical speciation.…”

Raman and X-ray absorption spectroscopic studies of hydrothermally altered alkali-borosilicate nuclear waste glass

“…However, the energy range scanned at the Na K-edge was wide enough so that EXAFS analyses could be done. Earlier studies [22][23][24][25][26][27][28] characterized the Na environments in some silicate minerals and glasses using XAS. Na XANES data were presented for a variety of crystalline silicates [22,24,27,28]; calculated Na XANES spectra were also presented for a few silicates [22,24], where qualitative similarities were demonstrated between theory and experiment.…”

“…Earlier studies [22][23][24][25][26][27][28] characterized the Na environments in some silicate minerals and glasses using XAS. Na XANES data were presented for a variety of crystalline silicates [22,24,27,28]; calculated Na XANES spectra were also presented for a few silicates [22,24], where qualitative similarities were demonstrated between theory and experiment. Na EXAFS data and analysis results are reported for the local Na environments within a variety of silicate glasses [23,[25][26][27], which generally have average Na-O distances between 2.30 and 2.50 Å with three to five oxygen nearest-neighbors.…”

“…The calculations generally followed the procedure outlined by Neuville et al [22,41], where a Hedin-Lundqvist type exchange potential was used, and the self-consistent potential calculation used a maximum cluster radius of 4.8 Å, while the full multiple-scattering part of the calculation used a maximum radius of 8.0 Å. The calculation that best matched the experimental data used the Z + 1 model [32,41,42], where Mg, instead of Na, was placed at the origin of the cluster, which simulates the excited electronic configuration of the photo-absorber by promoting the core electron to a valence orbital.…”

Na, Mg, Ni and Cs distribution and speciation after long-term alteration of a simulated nuclear waste glass: A micro-XAS/XRF/XRD and wet chemical study

“…The monochromator angle at the 10.3.2 beamline was calibrated using a Ni metal foil (E 0 = 8333 eV). At LUCIA, energy calibration for the beryl crystals was made by matching a NaCl (halite) reference spectrum measured during the beam time to the data of Neuville et al (2004) (E peak_b = 1076.5 eV). For the Si(1 1 1) crystals, the K-edge inflection point of metallic Ag (E 0 = 3351 eV), which was brought on the sample in the form of tiny orientation marks, was used.…”