XPS and XAS Study of the Sorption of Hg(II) onto Pyrite

Abstract

Sorption of mercury(II) onto well-characterized samples of pyrite was studied between pH 2 and 12 using X-ray photoelectron spectroscopy for surface analysis and extended X-ray absorption fine structure for surface speciation. In the presence of Hg, the surface oxidation of pyrite was strongly decreased. Even if the sorption capacity of pyrite for Hg was high, the sorption reversibility was possible by adding some strong ligands, such as I-, S2O3 2-, and CN-, to the aqueous phase. Spectroscopic studies showed the absence of Hg(0) and S(−II) and evidenced the formation of a surface complex between S(−I) and Hg(II). At low pH, ternary surface complexes ⋮S-I−Hg−OH or ⋮S-I−Hg−Cl were formed with the following distances: R ⋮ S - Hg = 2.40 Å, R Hg - OH = 2.25 Å, and R Hg - Cl = 2.33 Å if Cl- was present. At high pH, the spectroscopic signals of Hg, S, or Fe decreased, possibly because of the presence at the surface of a solid solution constituted of Fe (hydr)oxides and surface complexes between Hg and both oxides and pyritic sulfur.

Modification of Mackinawite with L-Cysteine: Synthesis, Characterization, and Implications to Mercury Immobilization in Sediment

“…The presence of sulfate is attributed more to the inefficient removal by mackinawite washing during the synthesis process, than the oxidation process. These results are in agreement with those obtained by other researchers (Nesbitt and Muir (1994); Behra et al (2001), Boursiquot et al, 2001;Mullet et al, 2001). For modified mackinawite the identified peaks were centered at 160.3 and 161.2 eV characteristic of (S 2-), 161.8 eV characteristic of (S 2 2-), 163.0 eV characteristic of (S n 2-), and 164.5 characteristic of (S 0 ).…”

Novel Adsorbent-Reactants for Treatment of Ash and Scrubber Pond Effluents

“…Formation of precipitates such as HgS (s) or Hg 2 S (s) could explain the observed behavior. Behra et al (2001) suggested that the following mechanism shown in Equations 4-6 can lead to formation of precipitates in systems with Hg(II) and pyrite. …”

“…However, the Fe(III)-O species produced on the surface could exist as Fe(III) oxyhydroxides and differential charge effects could occur due to the formation of heterogeneous surfaces. The confirmation of these charge effects is important, because these Fe(III) species plays an important role in catalyzing oxidation processes (references given in Behra et al 2001). Behra et al (2001) provided the evidence for existence of charge effects on a pyrite surface after contact with Hg(II) through the investigation of O 1s XPS spectrum.…”

“…The confirmation of these charge effects is important, because these Fe(III) species plays an important role in catalyzing oxidation processes (references given in Behra et al 2001). Behra et al (2001) provided the evidence for existence of charge effects on a pyrite surface after contact with Hg(II) through the investigation of O 1s XPS spectrum. (2000) showed that in addition to the H 2 O peak at 532.6 eV, there is an extra peak located near 535.0 eV that is caused by the sorption of water molecules onto isolated islands of Fe(III) oxyhydroxide, which results in a differential charge effect.…”

Establishment of an Environmental Control Technology Laboratory with a Circulating Fluidized-Bed Combustion System

“…It may be implied that Cl coal , which was found to be a critical factor affecting mercury speciation, did not have a direct effect on mercury adsorption on the fly ash. S coal may have some direct effect on mercury adsorption on the fly ash [43][44] . An alternative possibility is that coal rank, which was positively correlated with Cl coal , may replace the function of Cl coal in the regression model.…”