Clay mineral weathering and contaminant dynamics in a caustic aqueous system I. Wet chemistry and aging effects

Journal Article · Fri Apr 08 04:00:00 EDT 2005 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/j.gca.2005.04.003· OSTI ID:889546

Choi, Sunkyung; Amistadi, Mary K; Chorover, Jon

Caustic high level radioactive waste induces mineral weathering reactions that can influence the fate of radionuclides released in the vicinity of leaking storage tanks. The uptake and release of CsI and SrII were studied in batch reactors of 2:1 layer-type silicates?illite (Il), vermiculite (Vm) and montmorillonite (Mt)?under geochemical conditions characteristic of leaking tank waste at the Hanford Site in WA (0.05 mAlT, 2 m Na*, 1 m NO3 *, pH *14, Cs and Sr present as co-contaminants). Time series (0 to 369 d) experiments were conducted at 298 K, with initial [Cs]0 and [Sr]0 concentrations from 10*5 to 10*3 mol kg*1. Clay mineral type affected the rates of (1) hydroxide promoted dissolution of Si, Al and Fe, (2) precipitation of secondary solids and (3) uptake of Cs and Sr. Initial Si release to solution followed the order Mt * Vm * Il. An abrupt decrease in soluble Si and/or Al after 33 d for Mt and Vm systems, and after 190 d for Il suspensions was concurrent with accumulation of secondary aluminosilicate precipitates. Strontium uptake exceeded that of Cs in both rate and extent, although sorbed Cs was generally more recalcitrant to subsequent desorption and dissolution. After 369 d reaction time, reacted Il, Vm and Mt solids retained up to 17, 47 and 14 mmol kg*1 (0.18, 0.24 and 0.02 *mol m*2) of Cs, and 0, 27 and 22 mmol kg*1 (0, 0.14 and 0.03 *molm*2) Sr, respectively, which were not removed in subsequent Mg exchange or oxalic acid dissolution reactions. Solubility of Al and Si decreased with initial Cs and Sr concentration in Mt and Il, but not in Vm. High co-contaminant sorption to the Vm clay, therefore, appears to diminish the influence of those ions on mineral transformation rates.

• 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: 889546
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 18 Vol. 69; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

12 MANAGEMENT OF RADIOACTIVE AND NON-RADIOACTIVE WASTES FROM NUCLEAR FACILITIES
AGING
CHEMISTRY
CLAYS
DESORPTION
DISSOLUTION
Environmental Molecular Sciences Laboratory
HYDROXIDES
MONTMORILLONITE
OXALIC ACID
PRECIPITATION
RADIOACTIVE WASTES
RADIOISOTOPES
SOLUBILITY
SORPTION
STRONTIUM
TRANSFORMATIONS
VERMICULITE
WASTES
WEATHERING