Removal of selenite from water using a synthetic dithiolate: an experimental and quantum chemical investigation.
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.
Department of Chemistry, University of Kentucky , Lexington, Kentucky 40506-0055, United States.
Daniel
D
Burriss
Wenli
W
Zou
Dieter
D
Cremer
John
J
Walrod
David
D
Atwood
D003543:Cysteamine / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry; D015394:Molecular Structure; D010795:Phthalic Acids / Q000138:chemical synthesis / Q000737:chemistry*; D011789:Quantum Theory; D020887:Selenious Acid / Q000737:chemistry / Q000302:isolation & purification*; D014867:Water / Q000737:chemistry*
D010795:Phthalic Acids; C000596849:dithiol N,N'-bis(2-mercaptoethyl)isophthalamide; D014867:Water; D003543:Cysteamine; D020887:Selenious Acid