TY - JOUR
T1 - Dynamics and Mechanisms of Mn(II), Co(II), Ni(II), Zn(II), and Cd(II) Sorption onto Green Rust Sulfate
AU - Alam, Khondaker M.N.
AU - Elzinga, Evert J.
N1 - Funding Information: This research was supported by the U.S. National Science Foundation through Grant CHE-1904981. The authors acknowledge the Argonne National Laboratory for use of Beamline 12BM at the Advanced Photon Source, a US Department of Energy Office of Science User Facility operated for the DOE office of Science by Argonne National Laboratory under Contract DE-AC02-06CH11357. The work also used beamline 6BM of the National Synchrotron Light Source II, a US Department of Energy Office of Science User Facility operated for the DOE Office of Science by Brookhaven National Laboratory under Contract No. DE-SC0012704. The authors thank Sungsik Lee and Benjamin Reinhart (APS 12BM) and Bruce Ravel (NSLS-II 6BM) for assistance with XAS data collection. They further thank Associate Editor Daniel Giammar and two anonymous reviewers for their helpful comments that improved this paper. Publisher Copyright: © 2023 American Chemical Society. All rights reserved.
PY - 2023/6/6
Y1 - 2023/6/6
N2 - Batch kinetic experiments are combined with X-ray absorption spectroscopy (XAS) to compare the sorption of Mn(II), Co(II), Ni(II), Zn(II), and Cd(II) with sulfated green rust (GR) in anoxic pre-equilibrated suspensions at pH 8 over a timespan of 1 h to 1 week. The XAS data suggest that all five divalent metals coordinate at Fe(II) sites of the GR sorbent, whereas the batch results show that GR exhibits bimodal sorption behavior, with fast but limited uptake of Mn(II) and Cd(II) and much more extensive sorption of Co(II), Ni(II), and Zn(II) that continues throughout the entire experimental timeframe. We attribute these observations to differences in the affinity and extent of divalent metal substitution in Fe(II) sites of the GR lattice as controlled by ionic size. Divalent metals smaller than Fe(II) [i.e., Co(II), Ni(II), and Zn(II)] are readily accommodated and undergo coprecipitation during GR dissolution-reprecipitation. In contrast, divalent metals larger than Fe(II) [i.e., Mn(II) and Cd(II)] have a low affinity for substitution and remain coordinated at the surface following limited exchange with Fe(II)(s)at GR particle edges. These results imply that GR may strongly affect the solubility of Co(II), Ni(II), and Zn(II) in reducing geochemical systems but will have little impact on the retention of Cd(II) and Mn(II).
AB - Batch kinetic experiments are combined with X-ray absorption spectroscopy (XAS) to compare the sorption of Mn(II), Co(II), Ni(II), Zn(II), and Cd(II) with sulfated green rust (GR) in anoxic pre-equilibrated suspensions at pH 8 over a timespan of 1 h to 1 week. The XAS data suggest that all five divalent metals coordinate at Fe(II) sites of the GR sorbent, whereas the batch results show that GR exhibits bimodal sorption behavior, with fast but limited uptake of Mn(II) and Cd(II) and much more extensive sorption of Co(II), Ni(II), and Zn(II) that continues throughout the entire experimental timeframe. We attribute these observations to differences in the affinity and extent of divalent metal substitution in Fe(II) sites of the GR lattice as controlled by ionic size. Divalent metals smaller than Fe(II) [i.e., Co(II), Ni(II), and Zn(II)] are readily accommodated and undergo coprecipitation during GR dissolution-reprecipitation. In contrast, divalent metals larger than Fe(II) [i.e., Mn(II) and Cd(II)] have a low affinity for substitution and remain coordinated at the surface following limited exchange with Fe(II)(s)at GR particle edges. These results imply that GR may strongly affect the solubility of Co(II), Ni(II), and Zn(II) in reducing geochemical systems but will have little impact on the retention of Cd(II) and Mn(II).
KW - X-ray absorption spectroscopy
KW - coprecipitation
KW - green rust
KW - sorption
KW - substitution
KW - trace metals
UR - http://www.scopus.com/inward/record.url?scp=85162211990&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85162211990&partnerID=8YFLogxK
U2 - 10.1021/acs.est.3c01584
DO - 10.1021/acs.est.3c01584
M3 - Article
C2 - 37221677
SN - 0013-936X
VL - 57
SP - 8396
EP - 8405
JO - Environmental Science and Technology
JF - Environmental Science and Technology
IS - 22
ER -