The Use of XAFS to Distinguish between Inner- and Outer-Sphere Lead Adsorption Complexes on Montmorillonite

Strawn, Daniel G.; Sparks, Donald L.

doi:10.1006/jcis.1999.6330

Cited by 258 publications

(189 citation statements)

References 36 publications

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“…While numerous XAS studies of Pb adsorption to soil minerals exist (25)(26)(27), little information was available on the adsorption of Pb onto SOM. Cadmium formed a variety of complexes being 4-coordinate with thiols, and 4-and 6-coordinate with O/N ligands (28).…”

Section: Nmr Spectra and Elementalmentioning

confidence: 99%

Effects of Copper, Lead, and Cadmium on the Sorption of 2,4,6-Trichlorophenol Onto and Desorption from Wheat Ash and Two Commercial Humic Acids

Wang

Shan

Feng

et al. 2009

Environ. Sci. Technol.

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The effects of copper (Cu 2+ ), lead (Pb 2+ ), and cadmium (Cd 2+ ) on the sorption of 2,4,6-trichlorophenol (TCP) to and desorption from wheat ash and two commercial humic acids were studied. Copper and Pb 2+ diminished the sorption of TCP onto all adsorbents, and made desorption of TCP less hysteretic from ash and German humic acids (GeHA), but more hysteretic from Tianjin humic acids (TJHA). Cadmium had little effect on TCP sorption and desorption. Fourier-transform infra red (FTIR) and X-ray absorption spectroscopy (XAS) in conjunction with fluorescence quenching studies provided insights into the mechanisms of TCP sorption and desorption as affected by Cu 2+ and Pb 2+ , indicating that complexation of Cu 2+ and Pb 2+ was likely via carboxylic, hydroxylic and phenolic groups of ash, TJHA and GeHA, and that theses same functional groups also reacted with TCP during sorption. In contrast, Cd, a "soft acid", had no effect on the adsorption of TCP. Hydration shells of dense water around adsorbed Cu 2+ and Pb 2+ ions may also compete with TCP for available surface area. Fluorescence quenching of pyrene verified that for TJHA, Cu 2+ and Pb 2+ promoted the formation of supramolecular associations with interior hydrophobic regions separated from aqueous surroundings by exterior hydrophilic layers.

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Section: Nmr Spectra and Elementalmentioning

confidence: 99%

Effects of Copper, Lead, and Cadmium on the Sorption of 2,4,6-Trichlorophenol Onto and Desorption from Wheat Ash and Two Commercial Humic Acids

Wang

Shan

Feng

et al. 2009

Environ. Sci. Technol.

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“…For layer silicates, however, irreversible or non-exchangeable metal sorption may be via several mecha nisms. On such materials, reaction may occur at clay edge sites (McBride, 1989;Pardo, 2000;Strawn and Sparks, 1999), as occlusion into cavities/deformities on planar sur faces (Nakhone, 1997), and as fixation in interlayer positions of 2:1 phyllosilicates. This last mechanism is a possibility when the selectivity exhibited by the interlayer for a metal iondCa, Cd, and Pb in this studydis much larger than the se lectivity of the interlayer for the extracting ion (Na in this study) (Sposito et al, 1983).…”

Section: Mechanisms Of Metal Sorptionmentioning

confidence: 99%

Sequential sorption of lead and cadmium in three tropical soils

Appel

Lena

Rhue

et al. 2008

Environmental Pollution

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The sorption and desorption of Pb and Cd in tropical soils is strongly influenced by the order in which these metals enter the soil environment. AbstractIt is important to examine mechanisms of Pb and Cd sorption in soils to understand their bioavailability. The ability of three tropical soils to retain Pb, Cd, and Ca was evaluated. The objectives of this study were to (1) determine the extent to which soil sorption sites are metal specific, (2) investigate the nature of reactions between metals and soil surfaces, and (3) identify how metals compete for sorption sites when they are introduced to soils sequentially or concurrently. Lead was shown to be much less exchangeable than Cd and inhibited Cd sorption. Cadmium had little effect on Pb sorption, though both Ca and Cd inhibited the adsorption of Pb at exchange sites. Lead appears to more readily undergo innersphere surface complexation with soil surface functional groups than either Cd or Ca. Thus, regardless of when Pb is introduced to a soil, it should be less labile than Cd.

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“…Clay minerals, such as montmorillonite, are potential adsorbents for heavy metals as they have a large specific surface area and a high cation-exchange capacity. X-ray absorption fine structure spectroscopic study indicated that the formation of inner-and outer-sphere complexes is responsible for the adsorption of Pb onto montmorillonite, and the adsorption of Pb depended on ionic strength and pH [20].…”

Section: Introductionmentioning

confidence: 99%

Effect of lead on the sorption of phenol onto montmorillonites and organo-montmorillonites

Yan

Shan

Wen

et al. 2007

Journal of Colloid and Interface Science

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The effect of lead (Pb) on the sorption of phenol onto montmorillonite-based sorbents was studied using a batch equilibration method when phenol and Pb were sorbed simultaneously and either Pb or phenol was previously sorbed. The sorbents were Na + -, Ca 2+ -, hexadecyl trimethylammonium (HDTMA)-Na + -, and HDTMA-Ca 2+ -montmorillonites. Pb diminished the sorption of phenol largely onto Na + -or Ca 2+ -montmorillonites, while phenol had little effect on the sorption of Pb onto all sorbents. Pb had no effect on the sorption of phenol onto HDTMA-Na + -or HDTMA-Ca 2+ -montmorillonites either. The sorption capacity of phenol followed the order HDTMA-Na + -> HDTMA-Ca 2+ -> Na + -> Ca 2+ -montmorillonites. The pseudo-second-order equation described the kinetics of phenol sorption well. Sorption isotherms of phenol followed the Freundlich equation. Phenol sorption on HDTMA-Na + -and HDTMA-Ca 2+ -montmorillonites was linear, while that on Na + -and Ca 2+ -montmorillonites was nonlinear.

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The Use of XAFS to Distinguish between Inner- and Outer-Sphere Lead Adsorption Complexes on Montmorillonite

Cited by 258 publications

References 36 publications

Effects of Copper, Lead, and Cadmium on the Sorption of 2,4,6-Trichlorophenol Onto and Desorption from Wheat Ash and Two Commercial Humic Acids

Effects of Copper, Lead, and Cadmium on the Sorption of 2,4,6-Trichlorophenol Onto and Desorption from Wheat Ash and Two Commercial Humic Acids

Sequential sorption of lead and cadmium in three tropical soils

Effect of lead on the sorption of phenol onto montmorillonites and organo-montmorillonites

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