Immobilization of 99-Technetium (VII) by Fe(II)-Goethite and Limited Reoxidation

Journal Article · Wed May 04 00:00:00 EDT 2011 · Environmental Science & Technology, 45(11):4904-4913

DOI:https://doi.org/10.1021/es104343p· OSTI ID:1018142

Um, Wooyong; Chang, Hyun-Shik; Icenhower, Jonathan P; Lukens, Wayne W; Serne, R Jeffrey; Qafoku, Nikolla; Westsik, Joseph H; Buck, Edgar C; Steven, Smith C

Synthesized goethite was successfully used with addition of Fe(II) to sequester Tc present in both deionized water and simulated off-gas scrubber waste solutions. Pertechnetate concentration in solution decreased immediately when the pH was raised above 7 by addition of sodium hydroxide. Removal of Tc(VII) from solution occurred most likely as a result of heterogeneous surface-catalyzed reduction to Tc(IV) and subsequent co-precipitation onto the goethite. The final Tc-bearing solid was identified as goethite-dominated Fe(III)-(oxy)hydroxide based on XRD analysis, confirming the widespread observation of its characteristic acicular habit by TEM/SEM images. Analysis of the solid precipitate by XAFS showed that the dominant oxidation state of Tc was Tc(IV) and was in octahedral coordination with Tc-O, Fe-O, and Tc-Fe bond distances that are consistent with direct substitution of Tc for Fe in the goethite structure. In some experiments the final Tc-goethite product was subsequently armored with additional layers of freshly precipitated goethite. Successful incorporation of Tc(IV) within the goethite mineral lattice and subsequent goethite armoring can limit re-oxidation of Tc(IV) and its subsequent release from Tc-goethite waste forms, even when the final product is placed in oxidizing environments that typify shallow waste burial facilities.

• Research Organization: Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
• Sponsoring Organization: USDOE
• DOE Contract Number: AC05-76RL01830
• OSTI ID: 1018142
• Report Number(s): PNNL-SA-72463; 35405; EY7144147
• Journal Information: Environmental Science & Technology, 45(11):4904-4913, Journal Name: Environmental Science & Technology, 45(11):4904-4913 Journal Issue: 11 Vol. 45; ISSN ESTHAG; ISSN 0013-936X
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
Coprecipitation
Environmental Molecular Sciences Laboratory
GOETHITE
Goethite
Hanford Site
LIQUID WASTES
PERTECHNETATES
REMOVAL
SCRUBBERS
SODIUM HYDROXIDES
Technetium
VALENCE
WASTE FORMS
WATER
X-RAY DIFFRACTION
secondary wastes