Sorption of mercuric ion by synthetic nanocrystalline mackinawite (FeS).
Iron sulfides are known to be efficient scavengers of heavy metals. In this study, Hg(II) sorption was investigated using synthetic nanocrystalline mackinawite (a disordered phase) as a function of initial Hg(II) concentration [Hg(II)]0, initial FeS concentration [FeS]0, total chloride concentration CIT, and pH. Hg(II) sorption mechanisms are dependent on relative concentrations of [Hg(II)]0 and [FeS]0 (the molar ratio of [Hg(II)0/[FeS]0). When the molar ratio of [Hg(II)]0/[FeS]o is as low as 0.05, adsorption is mainly responsible for Hg(II) removal, with its contribution to the overall sorption increasing at lower Cl(T). As the molar ratio increases, the adsorption capacity becomes saturated, resulting in precipitation of a sparingly soluble HgS(s). XRD analysis indicates formation of metacinnabar (beta-HgS). Concurrently with HgS(s) precipitation, the released Fe(II) from FeS(s) is resorbed by adsorption at acidic pH and either adsorption or precipitation as Fe (hydr)-oxides at neutral to basic pH. Subsequently, the Fe precipitate formed at neutral to basic pH serves as an adsorbent for Hg(II). Under the conditions where either adsorption or HgS(s) precipitation is dominant, more than 99% of [Hg(II)]0 is immobilized. When the molar ratio of [Hg(II)]0/[FeS]0 exceeds 1, the sulfide concentration is no longer sufficient for HgS(s) precipitation, and formation of chloride salts (Hg2Cl2 at acidic pH and HgCl2 x 3HgO at basic pH) occurs.
Jeong
Hoon Y
HY
Department of Civil and Environmental Engineering, University of Michigan, Ann Arbor, Michigan 48109, USA.
Klaue
Bjorn
B
Blum
Joel D
JD
Hayes
Kim F
KF
D000042:Absorption; D000327:Adsorption; D002712:Chlorides / Q000737:chemistry; D004784:Environmental Monitoring / Q000379:methods*; D005296:Ferrous Compounds / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000032:analysis*; D007501:Iron / Q000737:chemistry*; D008628:Mercury / Q000032:analysis*; D008956:Models, Chemical; D015233:Models, Statistical; D053758:Nanoparticles / Q000032:analysis*; D013440:Sulfides / Q000737:chemistry*; D014961:X-Ray Diffraction
D002712:Chlorides; D005296:Ferrous Compounds; D007477:Ions; D013440:Sulfides; D007501:Iron; D008628:Mercury; C022597:ferrous sulfide