Removing dissolved selenium (i.e., selenate and selenite) from water is a challenging wastewater management issue for a range of industries. The rates and extents of dissolved selenate and selenite removal through bench-scale iron electrocoagulation were investigated by focusing on the effects of dissolved oxygen and pH. We combined measurements of the aqueous phase with direct characterization of the resulting solids. At pH 8, the dissolved selenium removal rate and extent were highest at strictly anoxic conditions. At this condition, which was the most reducing one studied, the selenium was mainly transformed to elemental selenium (Se<sup>0</sup>) or selenide as determined by X-ray absorption spectroscopy. During iron electrocoagulation at this condition, a blue-green solid that was probably green rust formed in the suspension. Dissolved selenium removal was better with iron electrocoagulation than with direct addition of chemically-synthesized green-rust or ferrous hydroxide. This comparison suggests that during iron electrocoagulation there is an additional factor contributing to dissolved selenium removal other than just the formation of Fe(II)-containing solids. At pH 6, the rates and the extents of dissolved selenium removal were similar regardless of the oxygen level and were not as high as those achieved at pH 8 at anoxic conditions.

Impact of dissolved oxygen and pH on the extent and products of selenium(VI) removal by iron electrocoagulation

256th National Meeting (2018)

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