Elevated concentrations of selenium in food and water are associated with a number of diseases and adverse health effects. The most common forms of selenium in water are selenite, (Se (IV), selenium in the +4 oxidation state) and selenate (Se (VI), selenium in the +6 oxidation state).  The objective of this work was to model the sorption of the two selenium oxyanions on iron-modified zeolites. The ability of iron-modified zeolites to bind selenium oxyanions was modeled using the triple layer surface complexation model (TLM) as a function of selenium concentration, ionic strength, and pH. Batch experiments conducted as a function of selenium concentration, pH, and ionic strength can be simulated by the model accurately. The sorption results are consistent with a different sorption mechanism for the two anions, namely that selenite binds as an inner-sphere complex and selenate as an outer-sphere complex. These mechanisms are reflected in the surface complexes used to model selenium sorption using the geochemical code HYDRAQL. The single sorption binding constants for selenite and selenate were obtained by optimizing the modeling results using the constraints of multiple data sets obtained as a function of pH, selenium concentration, and ionic strength. Given that in most surface waters selenium is encountered most frequently as selenate, these results have significant implications for the transport of selenium in the environment and for the remediation of waters and groundwaters contaminated with selenium.

Surface complexation modeling of selenium sorption on iron-modified zeolites

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.