Raman analysis of perrhenate and pertechnetate in alkali salts and borosilicate glasses

Abstract

Sodium borosilicate glasses containing rhenium or technetium were fabricated and their vibrational spectra studied using confocal Raman microscopy. Glass spectra were interpreted relative to new high-resolution spectra of pure crystalline NaReO 4 , KReO 4 , NaTcO 4 , and KTcO 4 salts. Spectra of perrhenate and pertechnetate glasses exhibited sharp Raman bands, characteristic of crystalline salt species, superimposed on spectral features of the borosilicate matrix. At low concentrations of added KReO 4 or KTcO 4, the characteristic pertechnetate and perrhenate features are weak, whereas at high additions, sharp peaks from crystal field-splitting and C 4h symmetry dominate glass spectra, clearly indicating ReO 4 À or TcO 4 À is locally coordinated with K and/or Na. Peaks indicative of both K and Na salts are evident in many Raman spectra, with the Na form being favored at high concentrations of the source chemicals, where more K + is available for ion exchange with Na + from the base glass. The observed ion exchange likely occurred within depolymerized channels where nonbridging oxygens create segregation from the glass network in regions containing anions such as ReO 4 À and TcO 4 À as well as excess alkali cations. Although this anion exchange provides evidence of chemical mixing in the glass, it does not prove the added salts were homogeneously incorporated in the glass. The susceptibility to ion exchange from the base glass indicates that long-term immobilization of Tc in borosilicate glass must account for excess charge compensating alkali cations in melt glass formulations. Published 2014. This article is a U. S. Government work and is in the public domain in the USA.Additional supporting information may be found in the online version of this article at the publisher's web site.

Reactions during melting of low-activity waste glasses and their effects on the retention of rhenium as a surrogate for technetium-99

“…Given the projected concentration of 99 Tc in LAW glass at Hanford is~3 ppm mass on average [26]; the solubility of 99 Tc is not a factor in its retention in LAW glass. In addition, the structural role of Re and Tc in glass network was discussed in Goel et al 2013 [27] and Gassman et al 2014 [28].…”

Formation of Technetium Salts in Hanford Low‐Activity Waste Glass

“…The glass was analyzed for 99 Tc by ICP‐MS, technetium speciation by XANES and EXAFS, Raman spectroscopy, and Fe(II)/Fe(III) for indication of the redox conditions in the glass. The data has been previously reported and is not repeated here.…”

Crystal structure, phase transitions and vibrations of H2O molecules in [Ca(H2O)2](ReO4)2

“…The list of the band positions, their relative intensities and tentative assignments are listed in Table 4. The assignments of these vibrations were proposed by comparing their frequencies with the literature data collected for titled compounds and similar ionic aquametal(II) complexes [23,24] and perrhenate complexes [4,24,25]. All characteristic frequencies of H 2 O and ReO 4 -internal modes were identified.…”