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Yuanzhi Tang
Graduate Student
Geosciences Department
Lab: 217 ESS Building
Stony Brook University
Stony Brook, NY 11794-2100
B.S. Peking University
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Sorption of Metal Ions onto Mineral Surfaces Pretreated by Inorganic Ligands
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One of the ongoing concerns in environmental studies is the migration of heavy metals, e.g., Ni, Co, Cu, Zn as
well as radionuclides such as uranium, in the natural environment. Sorption of these contaminants from aqueous
systems to mineral surfaces plays an important role in controlling their mobility and bioavailability.
The presence of other organic or inorganic ligands may strongly influence the speciation of these heavy
metal ions, and therefore their uptake behaviors by mineral surfaces. My research goal is to identify the
basic mechanism(s) of how pre-treatment of mineral surfaces with ligands having a high affinity for binding
with metal ions would affect or potentially enhance the sorption of metal ions onto mineral surfaces. In the
present study I carry batch experiments, as well as spectroscopic studies, to reveal the uptake of U(VI),
including local coordination and sorption mechanism, on aluminum oxide with and without pre-treatment
by arsenate. Results from this work will provide predictive information of radionuclide mobility in complex
natural systems. Knowledge gained by examining the role of pre-treatment of mineral surfaces may also
have applications to the selection and design of permeable reactive barriers, which can be used in
removing dissolved uranyl from contaminated sites.
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Application of Synchrotron Techniques in Characterizing Chemical Speciation of
Heterogeneous Soil and Sediment Samples
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Synchrotron-based bulk and micro X-ray techniques (XRF, XRD, EXAFS and XANES) have been widely used to
characterize the spatial distribution and chemical speciation of heterogeneous soil and sediment
samples. Information such as element co-associations, concentrations, mineral phase of particular
particles, and oxidation state and local coordination structure of individual elements associated with
these particles. My current projects focusing on the chemical speciation of 1) high-Cr/Ni soils from
northern California and 2) sediment samples containing high concentrations of heavy metals,
especially Pb, collected from suburb and downtown New Orleans in the aftermath of Hurricane
Katrina. Studies were carried on the raw bulk samples as well as the solid residues of the
soil/sediments after leaching in simulated body fluids. Results from these studies have been
correlated with investigations of production of reactive oxygen species, and provide information
on the role of different mineral phases in governing the distribution of metal species, as well as
their chemical speciation and bioaccessibility.
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