XAS study of mercury(II) ions trapped in mercaptan-functionalized mesostructured silicate with a wormhole framework structure.
Directly assembled wormhole mesostructures with high level functionalized mercaptan (MP-HMS) have been shown to be effective mercury(II) (Hg2+) trapping agents. Sorption of Hg2+ onto MP-HMS was investigated using X-ray absorption spectroscopy (XAS) to identify the structural coordination of the adsorbed Hg. Samples with different fractions of mercaptan functionalized groups (i.e., x = 0.1 and 0.5) with various Hg/S molar ratios ranging from 0.05 to 1.4 were investigated. XAS analysis indicates that adsorbed Hg first coordination shell is best fitted with an Hg-O path and an Hg-S path. The Hg-S atomic distance (R(Hg-S)) remained relatively constant while the Hg-S coordination numbers (CN) decreased as Hg/S loading increased. For the Hg-O path, both the CN and the R(Hg-O) increased with increasing Hg loading. XAS results suggest that at low Hg loadings, adsorbed Hg2+ forms mostly monodentate sulfur complexes (-S-Hg-OH) with the sulfur functional groups on the MP-HMS surfaces. At high Hg loadings, the Hg coordination environment is consistent with the formation of a double-layer structure of Hg attached to sulfur binding sites (-S-Hg-O-Hg-OH).
Chen
Chia-Chen
CC
Department of Civil Engineering, University of Texas, Austin, Texas 78712-0273, USA.
McKimmy
Emily J
EJ
Pinnavaia
Thomas J
TJ
Hayes
Kim F
KF
D000327:Adsorption; D002413:Cations, Divalent / Q000737:chemistry; D008628:Mercury / Q000737:chemistry*; D017640:Silicates / Q000737:chemistry*; D013057:Spectrum Analysis / Q000379:methods; D013438:Sulfhydryl Compounds / Q000737:chemistry*; D013455:Sulfur / Q000737:chemistry*; D014965:X-Rays
D002413:Cations, Divalent; D017640:Silicates; D013438:Sulfhydryl Compounds; D013455:Sulfur; D008628:Mercury