TY - JOUR
T1 - Redox-driven dissolution of clay minerals by uranium under high pressure CO2 conditions
AU - Liu, Yan
AU - Luan, Fubo
AU - Burgos, William D.
N1 - Funding Information:
This technical effort was performed in support of the US DOE National Energy Technology Laboratory's on-going research in CO 2 -capture under the RES contract DE-FE-0004000 . This project was funded by NETL through a support contract with URS Energy & Construction, Inc. The views and opinions of the authors expressed herein do not necessarily state or reflect those of the US government.
PY - 2014/9/15
Y1 - 2014/9/15
N2 - Geologic sequestration of supercritical CO2 is one technology proposed to mitigate global warming. Increased acidity of brine due to CO2 injection could lead to mineral dissolution of cap rock and well seals and mobilization of contaminants (e.g., U, Pb, As). In this study we examined the dissolution of nontronite NAu-2, an Fe(III)-rich clay mineral, and partially-reduced nontronite (R-NAu-2) in a synthetic brine (0.33M Na2SO4) under high pressure CO2 conditions (PT=9.66bar, PCO2≥8.66bar CO2, T=20°C) and in 1.40M H3PO4-0.50M H2SO4. Uranyl(VI) or biogenic uraninite(IV) was added as a redox-active contaminant and reaction kinetics were measured over a 15d period. Unaltered nontronite [3.4% Fe(II)] dissolved very little under high pressure CO2 conditions. However, chemically-reduced nontronite [48% Fe(II)] dissolved more rapidly (half-life of 78.4d under high pressure CO2 conditions, 17.8h in H3PO4-H2SO4). Structural Fe(II) in reduced nontronite [R-NAu-2 Fe(II)] was preferentially dissolved compared to structural Fe(III) in unaltered nontronite [NAu-2 Fe(III)]. No redox reactions were observed between R-NAu-2 Fe(II) and U(VI). In contrast, uraninite was oxidized by NAu-2 Fe(III) faster and to a greater extent under high pressure CO2 conditions as compared to ambient pressure conditions (PT=1.0bar, 95:5% N2:H2). Redox reactions between uraninite and NAu-2 Fe(III) enhanced the dissolution of both clay and U, indicative of potential risks associated with geologic carbon sequestration.
AB - Geologic sequestration of supercritical CO2 is one technology proposed to mitigate global warming. Increased acidity of brine due to CO2 injection could lead to mineral dissolution of cap rock and well seals and mobilization of contaminants (e.g., U, Pb, As). In this study we examined the dissolution of nontronite NAu-2, an Fe(III)-rich clay mineral, and partially-reduced nontronite (R-NAu-2) in a synthetic brine (0.33M Na2SO4) under high pressure CO2 conditions (PT=9.66bar, PCO2≥8.66bar CO2, T=20°C) and in 1.40M H3PO4-0.50M H2SO4. Uranyl(VI) or biogenic uraninite(IV) was added as a redox-active contaminant and reaction kinetics were measured over a 15d period. Unaltered nontronite [3.4% Fe(II)] dissolved very little under high pressure CO2 conditions. However, chemically-reduced nontronite [48% Fe(II)] dissolved more rapidly (half-life of 78.4d under high pressure CO2 conditions, 17.8h in H3PO4-H2SO4). Structural Fe(II) in reduced nontronite [R-NAu-2 Fe(II)] was preferentially dissolved compared to structural Fe(III) in unaltered nontronite [NAu-2 Fe(III)]. No redox reactions were observed between R-NAu-2 Fe(II) and U(VI). In contrast, uraninite was oxidized by NAu-2 Fe(III) faster and to a greater extent under high pressure CO2 conditions as compared to ambient pressure conditions (PT=1.0bar, 95:5% N2:H2). Redox reactions between uraninite and NAu-2 Fe(III) enhanced the dissolution of both clay and U, indicative of potential risks associated with geologic carbon sequestration.
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U2 - 10.1016/j.chemgeo.2014.06.009
DO - 10.1016/j.chemgeo.2014.06.009
M3 - Article
AN - SCOPUS:84903794875
SN - 0009-2541
VL - 383
SP - 100
EP - 106
JO - Chemical Geology
JF - Chemical Geology
ER -