The dissolution of synthetic Na-boltwoodite in sodium carbonate solutions

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doi: 10.1016/j.gca.2006.06.1553
Authors:Ilton, Eugene S.; Liu, C.; Yantasee, Wassana; Wang, Z.; Moore, Dean A.; Felmy, Andrew R.; Zachara, J. M.
Author Affiliations:Primary:
Pacific Northwest National Laboratory, Chemical Sciences Division, Richland, WA, United States
Volume Title:Geochimica et Cosmochimica Acta
Source:Geochimica et Cosmochimica Acta, 70(19), p.4836-4849. Publisher: Elsevier, New York, NY, International. ISSN: 0016-7037
Publication Date:2006
Note:In English. 26 refs.; illus., incl. 4 tables
Summary:Uranyl silicates such as uranophane and Na-boltwoodite appear to control the solubility of uranium in certain contaminated sediments at the U. S. Department of Energy Hanford site [Liu, C., Zachara, J. M., Qafoku, O., McKinley, J. P., Heald, S. M., Wang, Z. 2004. Dissolution of uranyl microprecipitates in subsurface sediments at Hanford Site, USA. Geochim. Cosmochim. Acta 68, 4519-4537.]. Consequently, the solubility of synthetic Na-boltwoodite, Na(UO2)(SiO3OH) · 1.5H2O, was determined over a wide range of bicarbonate concentrations, from circumneutral to alkaline pH, that are representative of porewater and groundwater compositions at the Hanford site and calcareous environments generally. Experiments were open to air. Results show that Na-boltwoodite dissolution was nearly congruent and its solubility and dissolution kinetics increased with increasing bicarbonate concentration and pH. A consistent set of solubility constants were determined from circumneutral pH (0 added bicarbonate) to alkaline pH (50 mM added bicarbonate). Average log Kosp = 5.86 ± 0.24 or 5.85 ± 0.0.26; using the Pitzer ion-interaction model or Davies equation, respectively. These values are close to the one determined by [Nguyen, S. N., Silva, R. J., Weed, H. C., Andrews, Jr., J. E., 1992. Standard Gibbs free energies of formation at the temperature 303.15K of four uranyl silicates: soddyite, uranophane, sodium boltwoodite, and sodium weeksite. J. Chem. Thermodynamics 24, 359-376.] under very different conditions (pH 4.5, Ar atmosphere). Abstract Copyright (2006) Elsevier, B.V.
Subjects:Alkali metals; Carbonates; Chemical composition; Chemical reactions; Controls; Crystal chemistry; Environmental analysis; Experimental studies; Geochemistry; Ground water; Kinetics; Metals; Models; Nesosilicates; Orthosilicates; PH; Pollution; Remediation; Sediments; Silicates; Sodium; Soil pollution; Soils; Solubility; Solutions; Spectra; Stoichiometry; Synthetic materials; TEM data; Uranophane; Water pollution; Water-rock interaction; X-ray diffraction data; X-ray spectra; Boltwoodite
Record ID:2007116400
Copyright Information:GeoRef, Copyright 2018 American Geosciences Institute. Reference includes data from CAPCAS, Elsevier Scientific Publishers, Amsterdam, Netherlands
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