X-ray absorption spectroscopy of Co(II) sorption complexes on quartz (α-SiO2) and rutile (TiO2)

O’Day, Peggy A.; Chisholm-Brause, Catherine J.; Towle, Steven N.; Parks, George S.; Brown, Gordon E.

doi:10.1016/0016-7037(96)00114-7

Cited by 112 publications

(121 citation statements)

References 65 publications

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“…One might expect systems in which weakly bound sorbate species are formed to "promote" polymerization and/or precipitation because the adsorption edge is delayed to higher pH and higher adion concentration. Another question prompted by the XAFS study of O'Day et al (8), which focuses on the mechanism of Co(II) sorption on ␣-SiO 2 and rutile, addresses the effects on sorption products of structural mismatch between surface cation-oxygen polyhedra and the coordination polyhedra of the solution species. To more fully understand surface reactivity and the transformation or growth of surface clusters, we need to compare the types of sorption complexes formed on different metal-oxide surfaces at both low and high surface coverages of a given metal cation and as a function of contact time between aqueous solution and substrate.…”

Section: Introductionmentioning

confidence: 99%

“…Mechanistic information of this type for various sorbate-sorbent systems has been provided by spectroscopic and imaging methods, for example, X-ray absorption fine structure (XAFS) (1)(2)(3)(4)(5)(6)(7)(8)(9), electron paramagnetic resonance (EPR) (10 -23), and transmission electron microscopy (9,24). However, spectroscopic studies that involve systematic comparison of the effect of substrates on the geometry of sorption complexes for a given cation have focused on intermediate to high surface concentration ranges, where multinuclear complexes and precipitates dominate (2,3,5,8,9,25,26). Thus, there is relatively little knowledge about the type of sorption complexes formed under conditions in which monomeric or dimeric surface complexes are predicted to predominate.…”

Section: Introductionmentioning

confidence: 99%

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XAFS Spectroscopy Study of Cu(II) Sorption on Amorphous SiO2and γ-Al2O3: Effect of Substrate and Time on Sorption Complexes

Cheah

Brown

Parks

1998

Journal of Colloid and Interface Science

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

XAFS Spectroscopy Study of Cu(II) Sorption on Amorphous SiO2and γ-Al2O3: Effect of Substrate and Time on Sorption Complexes

Cheah

Brown

Parks

1998

Journal of Colloid and Interface Science

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“…In none of these experiments was evidence found for oxidation or reduction of the sorbate ion during or after XAFS data collection, as indicated by the lack of energy shifts in the edge positions, extended x-ray absorption fine structure (EXAFS)-derived metal-oxygen bond lengths, and x-ray photoelectron spectroscopy measurements. XAFS data analysis procedures used for the powdered sorption samples are described in Bargar et al (38,39) and O'Day et al (58). XAFS spectroscopic analysis of the natural soil and mine waste samples containing As, Se, and Pb was carried out by using the experimental and data analysis procedures described in Foster et al (59,60), Pickering et al (61), and Ostergren et al (62), for As, Se, and Pb, respectively.…”

Section: Experimental Approachmentioning

confidence: 99%

Mineral surfaces and bioavailability of heavy metals: A molecular-scale perspective

Brown

Foster

Ostergren

1999

Proc. Natl. Acad. Sci. U.S.A.

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300

167

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There is a continual influx of heavy metal contaminants and pollutants into the biosphere from both natural and anthropogenic sources. A complex variety of abiotic and biotic processes affects their speciation and distribution, including adsorption onto and desorption from mineral surfaces, incorporation in precipitates or coprecipitates, release through the dissolution of minerals, and interactions with plants and microbes. Some of these processes can effectively isolate heavy metals from the biosphere, whereas others cause their release or transformation to different species that may be more (or less) bioavailable and/or toxic to organisms. Here we focus on abiotic adsorption and precipitation or coprecipitation processes involving the common heavy metal contaminant lead and the metalloids arsenic and selenium in mine tailings and contaminated soils. We have used extremely intense x-rays from synchrotron sources and a structure-sensitive method known as x-ray absorption fine structure (XAFS) spectroscopy to determine the molecular-level speciation of these elements at concentrations of 50 to several thousand ppm in the contaminated environmental samples as well as in synthetic sorption samples. Our XAFS studies of As and Pb in the mine tailings show that up to 50% of these contaminants in the samples studied may be present as adsorbed species on mineral surfaces, which makes them potentially more bioavailable than when present in sparingly soluble solid phases. Our XAFS studies of Se(VI) sorption on Fe 2؉ -containing sulfates show that this element undergoes redox reactions that transform it into less bioavailable and less toxic species. This type of information on molecular-level speciation of heavy metal and metalloid contaminants in various environmental settings is needed to prioritize remediation efforts and to assess their potential hazard to humans and other organisms.

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“…The rutile phase has been more extensively studied than the two others and several microscopic studies were carried out under ultra-high vacuum (UHV) conditions and 3 with preliminary treatments (Ar + -ion bombardment, irradiation, high temperature), allowing a detailed knowledge of some selected crystallographic faces at the atomic level in terms of relaxation, reconstruction and defects [6][7][8][9][10][11][12]. Then, many metal and metal oxide overlayer growth [13][14][15][16][17][18], organic and inorganic molecule adsorptions [19][20][21][22][23][24][25][26], have also been studied and the surface chemistry on this phase was abundantly investigated. Among the low index faces naturally present in the rutile phase powder, the (110) face was found as the most stable one [27,28] and thus has been much more studied than the others.…”

Section: Introductionmentioning

confidence: 99%

Combined investigation of water sorption on TiO2 rutile (110) single crystal face: XPS vs. periodic DFT

et al. 2007

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XPS and periodic DFT calculations have been used to investigate water sorption on the TiO 2 rutile (110) face. Two sets of XPS spectra were collected on the TiO 2 (110) single crystal 2 clean and previously exposed to water: the first set with photoelectrons collected in a direction parallel to the normal to the surface; and the second set with the sample tilted by 70°, respectively. This tilting procedure promotes the signals from surface species and reveals that the first hydration layer is strongly coordinated to the surface and also that, despite the fact that the spectra were recorded under ultra-high vacuum, water molecules subsist in upper hydration layers. In addition, periodic DFT calculations were performed to investigate the water adsorption process to determine if molecular and/or dissociative adsorption takes place.The first step of the theoretical part was the optimisation of a dry surface model and then the investigation of water adsorption. The calculated molecular water adsorption energies are consistent with previously published experimental data and it appears that even though it is slightly less stable, the dissociative water sorption can also take place. This assumption was considered, in a second step, on a larger surface model where molecular and dissociated water molecules were adsorbed together with different ratio. It was found that, due to hydrogen bonding stabilisation, molecular and dissociated water molecules can coexist on the surface if the ratio of dissociated water molecules is less than ≈ 33 %. These results are consistent with previous experimental works giving a 10-25 % range.

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X-ray absorption spectroscopy of Co(II) sorption complexes on quartz (α-SiO2) and rutile (TiO2)

Cited by 112 publications

References 65 publications

XAFS Spectroscopy Study of Cu(II) Sorption on Amorphous SiO2and γ-Al2O3: Effect of Substrate and Time on Sorption Complexes

XAFS Spectroscopy Study of Cu(II) Sorption on Amorphous SiO2and γ-Al2O3: Effect of Substrate and Time on Sorption Complexes

Mineral surfaces and bioavailability of heavy metals: A molecular-scale perspective

Combined investigation of water sorption on TiO2 rutile (110) single crystal face: XPS vs. periodic DFT

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