Removal of Selenite from Water Using a Synthetic Dithiolate: An Experimental and Quantum Chemical Investigation

Abstract

Combination of the dithiol N,N'-bis(2-mercaptoethyl)isophthalamide, abbreviated as BDTH2 and as 1, with excess H2SeO3 in aqueous acidic (pH ≈ 1) conditions resulted in precipitation of BDT(S-Se-S) (6), with a (77)Se NMR chemical shift of δ = 675 ppm, and oxidized BDT. When the reaction is conducted under basic conditions Se(IV) is reduced to red Se(0) and oxidized 1. No reaction takes place between 1 and selenate (Se(VI)) under acidic or basic conditions. Compound 6 is stable in air but decomposes to red Se(0) and the disulfide BDT(S-S) (9) with heating and in basic solutions. Mechanisms and energetics of the reactions leading to 6 in aqueous solution were unraveled by extensive calculations at the ωB97X-D/aug-cc-pVTZ-PP level of theory. NMR chemical shift calculations with the gauge-independent atomic orbital (GIAO) method for dimethyl sulfoxide as solvent confirm the generation of 6 (calculated δ value = 677 ppm). These results define the conditions and limitations of using 1 for the removal of selenite from wastewaters. Compound 6 is a rare example of a bidentate selenium dithiolate and provides insight into biological selenium toxicity.

Efficient selenate removal by zero-valent iron in the presence of weak magnetic field

“…(1) and (2) [24]. Selenite is a softer base than selenate [25] and thus has smaller resistance to electron transfer and is more reactive with Fe 0 [26].…”

Thiol Reduction of Arsenite and Selenite: DFT Modeling of the Pathways to an As–Se Bond

“…The low barriers for these two steps are consistent with experimental rates observed by Kice. 78 Recently, Burriss et al 81 have suggested that a cyclic compound similar to 7 could rearrange to shift the oxygen to a sulfur center or transfer the oxygen between a sulfur and selenium center (Se−O−S). The related species MeSSe-O-SMe is 3.3 kcal/mol less stable than 7 suggesting that the release of ring strain may be important to Burriss's species.…”