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Title: The effect of calcium on aqueous uranium(VI) speciation and adsorption to ferrihydrite and quartz

Abstract

Recent studies of uranium(VI) geochemistry have focused on the potentially important role of the aqueous species, CaUO 2(CO 3) 3 2- and Ca 2UO 2(CO 3) 3 0(aq), on inhibition of microbial reduction and uranium(VI) aqueous speciation in contaminated groundwater. However, to our knowledge, there have been no direct studies of the effects of these species on U(VI) adsorption by mineral phases. The sorption of U(VI) on quartz and ferrihydrite was investigated in NaNO 3 solutions equilibrated with either ambient air (430 ppm CO 2) or 2% CO 2 in the presence of 0, 1.8, or 8.9 mM Ca 2+. Under conditions where the Ca 2UO 2(CO 3) 3 0(aq) species predominates U(VI) aqueous speciation, the presence of Ca in solution lowered U(VI) adsorption on quartz from 77% in the absence of Ca to 42% and 10% at Ca concentrations of 1.8 and 8.9 mM, respectively. U(VI) adsorption to ferrihydrite decreased from 83% in the absence of Ca to 57% in the presence of 1.8 mM Ca. Surface complexation model predictions that included the formation constant for aqueous Ca 2UO 2(CO 3) 3 0(aq) accurately simulated the effect of Ca 2+ on U(VI) sorption onto quartz and ferrihydrite within themore » thermodynamic uncertainty of the stability constant value. This study confirms that Ca 2+ can have a significant impact on the aqueous speciation of U(VI), and consequently, on the sorption and mobility of U(VI) in aquifers.« less

Authors:
; ;
Publication Date:
Research Org.:
Pacific Northwest National Lab. (PNNL), Richland, WA (United States)
Sponsoring Org.:
USDOE
OSTI Identifier:
944778
Report Number(s):
PNNL-SA-44029
Journal ID: ISSN 0016-7037; GCACAK; KP1504010; TRN: US200902%%946
DOE Contract Number:  
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Geochimica et Cosmochimica Acta; Journal Volume: 70; Journal Issue: 6
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; ADSORPTION; AIR; AQUIFERS; CALCIUM; GEOCHEMISTRY; QUARTZ; SORPTION; STABILITY; THERMODYNAMICS

Citation Formats

Fox, Patricia M, Davis, James A, and Zachara, John M. The effect of calcium on aqueous uranium(VI) speciation and adsorption to ferrihydrite and quartz. United States: N. p., 2006. Web. doi:10.1016/j.gca.2005.11.027.
Fox, Patricia M, Davis, James A, & Zachara, John M. The effect of calcium on aqueous uranium(VI) speciation and adsorption to ferrihydrite and quartz. United States. doi:10.1016/j.gca.2005.11.027.
Fox, Patricia M, Davis, James A, and Zachara, John M. Mon . "The effect of calcium on aqueous uranium(VI) speciation and adsorption to ferrihydrite and quartz". United States. doi:10.1016/j.gca.2005.11.027.
@article{osti_944778,
title = {The effect of calcium on aqueous uranium(VI) speciation and adsorption to ferrihydrite and quartz},
author = {Fox, Patricia M and Davis, James A and Zachara, John M},
abstractNote = {Recent studies of uranium(VI) geochemistry have focused on the potentially important role of the aqueous species, CaUO2(CO3)32- and Ca2UO2(CO3)30(aq), on inhibition of microbial reduction and uranium(VI) aqueous speciation in contaminated groundwater. However, to our knowledge, there have been no direct studies of the effects of these species on U(VI) adsorption by mineral phases. The sorption of U(VI) on quartz and ferrihydrite was investigated in NaNO3 solutions equilibrated with either ambient air (430 ppm CO2) or 2% CO2 in the presence of 0, 1.8, or 8.9 mM Ca2+. Under conditions where the Ca2UO2(CO3)30(aq) species predominates U(VI) aqueous speciation, the presence of Ca in solution lowered U(VI) adsorption on quartz from 77% in the absence of Ca to 42% and 10% at Ca concentrations of 1.8 and 8.9 mM, respectively. U(VI) adsorption to ferrihydrite decreased from 83% in the absence of Ca to 57% in the presence of 1.8 mM Ca. Surface complexation model predictions that included the formation constant for aqueous Ca2UO2(CO3)30(aq) accurately simulated the effect of Ca2+ on U(VI) sorption onto quartz and ferrihydrite within the thermodynamic uncertainty of the stability constant value. This study confirms that Ca2+ can have a significant impact on the aqueous speciation of U(VI), and consequently, on the sorption and mobility of U(VI) in aquifers.},
doi = {10.1016/j.gca.2005.11.027},
journal = {Geochimica et Cosmochimica Acta},
number = 6,
volume = 70,
place = {United States},
year = {Mon Jan 30 00:00:00 EST 2006},
month = {Mon Jan 30 00:00:00 EST 2006}
}