TY - JOUR
T1 - Microbial reduction of chlorite and uranium followed by air oxidation
AU - Zhang, Gengxin
AU - Burgos, William D.
AU - Senko, John M.
AU - Bishop, Michael E.
AU - Dong, Hailiang
AU - Boyanov, Maxim I.
AU - Kemner, Kenneth M.
N1 - Funding Information:
This research was supported by the Subsurface Biogeochemical Research (SBR) Program, Office of Science (BER), U.S. Department of Energy (DOE) grant no. DE-SC0005333 to The Pennsylvania State University, and by the National Science Foundation under grant no. CHE-0431328 . ANL contributions were supported, in part, by the ANL Subsurface Science Scientific Focus Area project, which is part of the SBR Program of BER, U.S. DOE under contract DE-AC02-06CH11357. Use of the MRCAT/EnviroCAT sector at the Advanced Photon Source (APS) was supported by the U.S. DOE, Office of Science and the MRCAT/EnviroCAT member institutions. We thank S. D. Kelly, B. Ravel, and the MRCAT/EnviroCAT staff for assistance with XAS data collection at the MRCAT/EnviroCAT. Use of the APS was supported by the U.S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under contract DE-AC02-06CH11357.
PY - 2011/4/22
Y1 - 2011/4/22
N2 - To evaluate the stability of biogenic nanoparticulate U(IV) in the presence of an Fe(II)-rich iron-bearing phyllosilicate, we examined the reduction of structural Fe(III) in chlorite CCa-2 and uranium(VI) by Shewanella oneidensis MR-1, and the reoxidation of these minerals (after pasteurization) via the introduction of oxygen. Bioreduction experiments were conducted with combinations of chlorite, U(VI), and anthraquinone-2,6-disulfonate (AQDS). Abiotic experiments were conducted to quantify the reduction of U(VI) by chemically-reduced chlorite-associated Fe(II), the oxidation of nanoparticulate U(IV) by unaltered structural Fe(III) in chlorite, and the sorption of U(VI) to chlorite, to elucidate interactions between U(VI)/U(IV) and Fe(II)/Fe(III)-chlorite. Solids were characterized by X-ray diffraction, scanning electron microscopy, and X-ray absorption spectroscopy to confirm Fe and U reduction and reoxidation. U(VI) enhanced the reduction of structural Fe(III) in chlorite and nanoparticulate U(IV) was oxidized by structural Fe(III) in chlorite, demonstrating that U served as an effective electron shuttle from S. oneidensis MR-1 to chlorite-Fe(III). Abiotic reduction of U(VI) by chlorite-associated Fe(II) was very slow compared to biological U(VI) reduction. The rate of nanoparticulate U(IV) oxidation by dissolved oxygen increased in the presence of chlorite-associated Fe(II), but the extent of U(IV) oxidation decreased as compared to no-chlorite controls. In identical experiments conducted with bioreduced suspensions of nanoparticulate U(IV) and nontronite (another iron-bearing phyllosilicate), the rate of U(IV) oxidation by dissolved oxygen increased in the presence of nontronite-associated Fe(II). In summary, we found that structural Fe(III) in chlorite delayed the onset of U(VI) loss from solution, while chlorite-associated Fe(II) enhanced the oxidation rate of U(IV) by dissolved oxygen, indicating that chlorite-associated Fe(II) could not protect nanoparticulate U(IV) from oxygen intrusion but instead increased the oxidation rate of U(IV).
AB - To evaluate the stability of biogenic nanoparticulate U(IV) in the presence of an Fe(II)-rich iron-bearing phyllosilicate, we examined the reduction of structural Fe(III) in chlorite CCa-2 and uranium(VI) by Shewanella oneidensis MR-1, and the reoxidation of these minerals (after pasteurization) via the introduction of oxygen. Bioreduction experiments were conducted with combinations of chlorite, U(VI), and anthraquinone-2,6-disulfonate (AQDS). Abiotic experiments were conducted to quantify the reduction of U(VI) by chemically-reduced chlorite-associated Fe(II), the oxidation of nanoparticulate U(IV) by unaltered structural Fe(III) in chlorite, and the sorption of U(VI) to chlorite, to elucidate interactions between U(VI)/U(IV) and Fe(II)/Fe(III)-chlorite. Solids were characterized by X-ray diffraction, scanning electron microscopy, and X-ray absorption spectroscopy to confirm Fe and U reduction and reoxidation. U(VI) enhanced the reduction of structural Fe(III) in chlorite and nanoparticulate U(IV) was oxidized by structural Fe(III) in chlorite, demonstrating that U served as an effective electron shuttle from S. oneidensis MR-1 to chlorite-Fe(III). Abiotic reduction of U(VI) by chlorite-associated Fe(II) was very slow compared to biological U(VI) reduction. The rate of nanoparticulate U(IV) oxidation by dissolved oxygen increased in the presence of chlorite-associated Fe(II), but the extent of U(IV) oxidation decreased as compared to no-chlorite controls. In identical experiments conducted with bioreduced suspensions of nanoparticulate U(IV) and nontronite (another iron-bearing phyllosilicate), the rate of U(IV) oxidation by dissolved oxygen increased in the presence of nontronite-associated Fe(II). In summary, we found that structural Fe(III) in chlorite delayed the onset of U(VI) loss from solution, while chlorite-associated Fe(II) enhanced the oxidation rate of U(IV) by dissolved oxygen, indicating that chlorite-associated Fe(II) could not protect nanoparticulate U(IV) from oxygen intrusion but instead increased the oxidation rate of U(IV).
UR - http://www.scopus.com/inward/record.url?scp=79953287544&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=79953287544&partnerID=8YFLogxK
U2 - 10.1016/j.chemgeo.2011.01.021
DO - 10.1016/j.chemgeo.2011.01.021
M3 - Article
AN - SCOPUS:79953287544
SN - 0009-2541
VL - 283
SP - 242
EP - 250
JO - Chemical Geology
JF - Chemical Geology
IS - 3-4
ER -