Use of a Novel Bio-Nano-IX Process to Remove SeO<sub>4</sub><sup>2–</sup> or Se(VI) from Contaminated Water in the Presence of Competing Sulfate (SO<sub>4</sub><sup>2–</sup>)
Hao Chen, Chelsey S. Shepsko, Arup K. SenGupta
Abstract
Removal of trace concentrations of selenium, mostly present as selenate or SeO42–, from contaminated water and wastewater or SO42– presents a formidable challenge that remains unsolved. A new hybrid bio-nano-ix process presented here provides a synergy where selenate (SeO42–) is first biologically reduced first to selenite (HSeO3–) under a relatively mild anoxic condition without producing H2S. Selenite, thus produced, is a relatively strong ligand and has a much higher sorption affinity for hybrid anion exchangers (HAIX-NanoFe) than competing sulfate anions. Extensive laboratory studies provided convincing evidence that the two-step bio-nano-ix process—a fixed-film biological unit followed by a HAIX-NanoFe sorption column—may very selectively remove Se(VI) or SeO42– in the presence of competing sulfate. HAIX-NanoFe is also amenable to efficient regeneration and reuses without any loss of selenite sorption capacity for multiple cycles. The sorbed selenium could thus be concentrated and recovered, thus posing no environmental threat of future contamination.