Fe-Solid Phase Transformations in the Sediments under Hyperalkaline and Saline Conditions.
(S02-qafoku599035-poster)
Authors:
N.P. Qafoku* - Battelle-Pacific Northwest National Laboratory C.C. Ainsworth - Battelle-Pacific Northwest National Laboratory R. Kukkadapu - Battelle-Pacific Northwest National Laboratory A. Dohnalkova - Battelle-Pacific Northwest National Laboratory O.S. Qafoku* - Battelle-Pacific Northwest National Laboratory
Abstract:
Significant amounts of Al-rich, hyperalkaline and saline high-level nuclear waste fluids (HLWF) leaked into the sediments of the Hanford vadose zone. Because of the importance of Fe in these geochemical systems (Fe is a redox sensitive element and may also participate in the formation of secondary solid phases), our objective was to investigate Fe fate in the Hanford sediments contacted with fluids similar to HLWF. Metal and glass-free systems were used to conduct batch and column experiments at 50 0C under CO2 and O2 free conditions. Results showed that Fe was released into the aqueous phase because of the base-induced dissolution of Fe-bearing soil minerals, such as biotite, smectite, and chlorite. The apparent aqueous Fe concentration increased with base concentration and decreased with Al concentration in the contacting solution. Fe precipitation most likely followed a different pathway from that of Si and Al which together form cancrinite and/or sodalite. The formation of hematite and goethite in the post-treatment sediments was suggested from the microscopic (SEM and TEM) and spectroscopic (Mossbauer spectroscopy) analyses, as well as from modeling with GMIN, which is a chemical equilibrium model that uses the free-energy minimization approach and Pitzer equations to calculate the excess energy in high ionic strength aqueous electrolyte solutions.
Speaker Information: Nikolla Qafoku, Battelle-Pacific Northwest National Laboratory, 902 Battelle Blvd.
P.O. Box 999 MSIN: K3-61, Richland, WA 99352; Phone: (509) 375-4364; E-mail: [email protected]
Session Information: Wednesday, November 5, 2003, 1:00 PM-4:00 PM Presentation Start: 1:00 PM (Poster Board Number: 1625)