Selenate (SeO42-) is one of the main impurities in wastewater from flue gas desulfurization. This compound is difficult to be removed from wastewater. Furthermore, it is economically difficult to lower the selenate concentration into the 10-20 μg/L range of wastewater effluent guidelines. The ability to dose Fe(II) to reactors using electrodes and applied voltages can allow electrocoaguation to be simpler and less labor-intensive technology than other approaches. By controlling aeration, voltage, or pH, electrocoagulation can produce diverse conditions of dissolved Fe(II) concentrations and a range of Fe(II)- and Fe(III)-containing solids. Different solids could induce reduction or adsorption of selenate on their surfaces or substitution of selenate into their structures, consequently transforming selenate into less harmful forms. We performed selenate removal experiments in a 1 L-batch reactor over a range of pH and dissolved oxygen conditions. The current was controlled to be 72 ± 2 mA, and treatment times of up to 40 minutes were studied. Total and dissolved iron species (e.g., Fe2+; Fe3+) concentrations were measured by a Ferrozine method. Dissolved selenium species (selenate and selenite) were measured with ion chromatography. The results reveal that at oxic conditions that resulted in the formation of iron oxides that some selenate removal was accomplished through adsorption and that this adsorption was greater at lower pH. Keywords: Selenate, Flue Gas, Iron Electrocoagulation, Iron Matters, Adsorption

Iron electrocoagulation for treatment of selenium in wastewater from flue gas desulfurization

251st National Meeting (2016)

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