In the environment, the sequestration and release of many toxic elements (e.g., Se and As) are often controlled by sorption to hydrous ferric oxides such as ferrihydrite, which is ubiquitous and can have a strong affinity for toxic elements. Tellurium (Te) is a metalloid, which can be more toxic than Se and As in some forms, that may be present in historic mine tailings and is increasingly used in high-tech applications, leading to its geographic distribution and increased potential for human exposure. Relatively little is known about the environmental behavior of Te, but it is anticipated that sorption of Te oxyanions will play an important role in the fate of Te released to pore waters by telluride mineral weathering. The goal of the present study is to investigate the affinity of Te oxyanions for ferrihydrite and surface complex geometry as a function of Te oxidation state [i.e., Te(IV) and Te(VI)], Te and ferrihydrite concentration, pH, ionic strength, and time. Geochemical modeling suggests Te oxyanions will have a strong affinity for ferrihydrite. Previous studies suggest that both Te(IV) and Te(VI) sorb via an inner sphere mechanism in contrast to other group 6A element Se. Modeling was performed in PHREEQC using thermodynamic data and linear free energy relationships (LFER) similar to previous studies of other elements. Preliminary experiments demonstrate that the LFER substantially underpredicts the affinity of Te oxyanions and that an increase in the binding constants (K) of up to K+3 is required to fit the model to experimental data. X-ray absorption spectroscopy was also used to determine the geometry of the Te sorption complex. The results from this project lend insight into the fate and transport of potential Te contaminants.

Examination of tellurium oxyanion sorption to ferrihydrite and characterization of sorption complex geometry

251st National Meeting (2016)

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