X-Ray Photoelectron Spectroscopic Study of Cobalt(II) and Nickel(II) Sorbed on Hectorite and Montmorillonite

Davison, Nigel; McWhinnie, William R.; Hooper, Alan

doi:10.1346/ccmn.1991.0390103

Cited by 31 publications

(12 citation statements)

References 25 publications

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“…Other XPS studies of Co(II) complexes on ~'-A1203 suggest a correlation between hydrolysis, adsorption, and the formation of aquo-type complexes at low pH and possible formation of a surface precipitate at high pH (Tewari et al, 1972;Tewari and Lee, 1975;Tewari and McIntyre, 1975). Cobalt and Ni sorption on hectorite and montmorillonite studied by XPS (Davison et al, 1991) supported previous results indicating the formation of a hydroxidelike species at high pH and no change in the binding energies of the sorbed species after successive washings, implying strong bonding of the cation to the surface. Electron spin resonance (ESR) has been used to probe surface complexes of Cu 2+ and Mn 2+ on kaolinite (McBride, 1976(McBride, , 1978 and other oxides in situ (McBride et al, 1984;Motschi, 1984;Bleam and McBride, 1985).…”

Section: Spectroscopic Studies Of Sorbed Metal Ionssupporting

confidence: 87%

Molecular Structure and Binding Sites of Cobalt(II) Surface Complexes on Kaolinite from X-Ray Absorption Spectroscopy

O’Day

Parks

Brown

1994

Clays and clay miner.

127

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Abstract--X-ray absorption spectroscopy (XAS) was used to determine the local molecular environment of Co(II) surface complexes sorbed on three different kaolinites at ambient temperature and pressure in contact with an aqueous solution. Interatomic distances and types and numbers of backscattering atoms have been derived from analysis of the extended X-ray absorption fine structure (EXAFS). These data show that, at the lowest amounts of Co uptake on kaolinite (0.20--0.32 ~mol m-2), Co is surrounded by ~60 atoms at 2.04-2.08 A and a small number orAl or Si atoms (N = 0.6-1.5) at two distinct distances, 2.67-2.72 A and 3.38-3.43/~. These results indicate that Co bonds to the kaolinite surface as octahedrally coordinated, bidentate inner-sphere mononuclear complexes at low surface coverages, confirming indirect evidence from solution studies that a fraction of sorbed Co forms strongly bound complexes on kaolinite. In addition to inner-sphere complexes identified by EXAFS spectroscopy, solution studies provide evidence for the presence of weakly bound, outer-sphere Co complexes that cannot be detected directly by EXAFS. One orientation for inner-sphere complexes indicated by XAS is bidentate bonding of Co to oxygen atoms at two A1-O-Si edge sites or an A1-O-Si and AI-OH (inner hydroxyl) edge site, i.e., comersharing between Co octahedra and AI and Si potyhedra. At slightly higher surface sorption densities (0.51-0.57/~mol m-2), the presence of a small number of second-neighbor Co atoms (average Nco < 1) at 3.10-3.13/~ indicates the formation of oxy-or hydroxy-bridged, multinuclear surface complexes in addition to mononuclear complexes. At these surface coverages, Co-Co and Co-AI/Si distances derived from EXAFS are consistent with edge-sharing between Co and AI octahedra on either edges or (001) faces of the aluminol sheet in kaolinite. Multinuclear complexes form on kaolinite at low surface sorption densities equivalent to < 5% coverage by a monolayer of oxygen-ligated Co octahedra over the N2-BET surface area. These spectroscopic results have several implications for macroscopic modeling of metal ion uptake on kaolinite: 1) Primary binding sites on the kaolinite surface at low uptake are edge, non-bridging AI-OH inner hydroxyl sites and edge AI-O-Si bridging oxygen sites, not Si-OH sites typically assumed in sorption models; 2) specific adsorption of Co is via bidentate, inner-sphere complexation; and 3) at slightly higher uptake but still a small fraction of monolayer coverage, formation of Co multinuclear complexes, primarily edge-sharing with A1-OH octahedra, begins to dominate sorption.

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Section: Spectroscopic Studies Of Sorbed Metal Ionssupporting

confidence: 87%

Molecular Structure and Binding Sites of Cobalt(II) Surface Complexes on Kaolinite from X-Ray Absorption Spectroscopy

O’Day

Parks

Brown

1994

Clays and clay miner.

127

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“…The presence of Cu + on the surface of a mineral has been reported many times (Klein et al, 1984;Mosser et al, 1992;Farquhar et al, 1996), but the question of how the Cu is reduced from Cu 2+ is still controversial. A similar reductive behaviour was found in Ni-adsorbed montmorillonite by Davison & McWhinnie (1991). The opinion that Cu 2+ was reduced to Cu + by sputtering of the iongun was widely accepted (Klein et al, 1984;Davison & McWhinnie, 1991;Farquhar et al, 1996).…”

Section: Xps Study For Cu 2+ -Absorbed Palygorskitessupporting

confidence: 64%

A study of adsorption and absorption mechanisms of copper in palygorskite

Cai¹,

Xue²

2008

Clay miner.

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Desorption experiments performed on four Cu-adsorbed palygorskites suggest that the leached Cu2+ ion originates at the surface and/or net-like interstice of the palygorskite fibres. The leached fraction, calculated from the quantities of adsorbed Cu2+ before and after desorption, is <1%. This may indicate that the majority of Cu is in inaccessible structural sites. X-ray diffraction, X-ray photoelectron spectroscopy, Fourier transform infrared (FTIR) spectroscopy and electron spin resonance (ESR) were used to determine the mineralogical character of the Cu-adsorbed palygorskite. Two photoelectron lines at 932.5 and/or 933.7 eV in the narrow scan Cu 2p3/2 spectra show that Cu adsorbed on the surface of palygorskite is in the Cu+ and Cu2+ state. The stretching vibrations of the octahedral cation shift ~3–5 cm–1 towards a greater wavenumber in the FTIR spectra of Cu-adsorbed palygorskite. It can be deduced that the Cu2+ is trapped in the channel of the palygorskite structure. The ESR spectra of the palygorskite give g values of 2.34, 2.12, 2.08 and 2.05, suggesting that some Cu ions cannot be reached by H+. These results confirm that Cu is adsorbed by palygorskite via three possible mechanisms: (1) the Cu is adsorbed onto the surface or in a net-like interstice, and its oxidation states are +1 and +2; (2) Cu forms a complex ion – [Cu(H2O)4]2+ or [Cu(H2O)6]2+, and is trapped in the channel; or (3) Cu enters into the hexagonal channel of the tetrahedral sites or the unoccupied octahedral sites of palygorskite.

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“…This behavior is typical of most montmorillonites. The sorption of various cations by hectorite and montmorillonite is different (Villemure 1990;Davison et al 1991), while some A1-OH polymers had similar preferential adsorption by both (Hsu 1992). Various species, such as metal-oxide pillars and organic or organometallic complexes, have recently been incorporated into the structure of synthetic hectorites to improve the catalytic properties of the products (Luca et al 1991;Barranlt et al 1992;Carrado 1992;Bergaya et al 1993).…”

Section: Introductionmentioning

confidence: 99%

Dissolution of Hectorite in Inorganic Acids

Komadel

1996

Clays and clay miner.

105

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Abstract--The effect of acid type and concentration on the reaction rate and products of dissolution of hectorite in inorganic acids was investigated. The dissolution of hectorite in hydrochloric (HC1), nitric (HNO3) and sulphuric (H2SO4) acids was characterized using quantitative chemical analysis, infrared (IR) and multinuclear MAS NMR spectroscopies. The rate of dissolution increased with acid concentration and decreased in the order HC1 --> HNO 3 > H2SO 4 at the same molar concentration. No differences were found in the reaction products of hectorite treated with the three acids. The rate of Li dissolution was slightly greater than that of Mg at lesser acid concentrations (0.25 M), indicating that protons preferentially attack Li octahedra. The gradual changes in the Si-O IR bands reflects the extent of hectorite dissolution. The analysis of 298i MAS NMR spectra relative peak intensities with dissolution time and acid concentration provided direct dissolution rates for tetrahedral (Q3) Si. After acid dissolution, most Si was bound in a three dimensional framework site (Q4), but a substantial part also occurred in the Si(OSi)3OH (Q31 OH) and Si(OSi)2(OH)2 (Q22OH) environments. These three sites probably occur in a hydrous amorphous silica phase. Both Aliv and Alw rapidly disappeared from 27A1 MAS NMR spectra of the dissolution products with acid treatment. The changes in IR and MAS NMR spectra of hectorite due to acid dissolution are similar to those of montmorillonite.

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X-Ray Photoelectron Spectroscopic Study of Cobalt(II) and Nickel(II) Sorbed on Hectorite and Montmorillonite

Cited by 31 publications

References 25 publications

Molecular Structure and Binding Sites of Cobalt(II) Surface Complexes on Kaolinite from X-Ray Absorption Spectroscopy

Molecular Structure and Binding Sites of Cobalt(II) Surface Complexes on Kaolinite from X-Ray Absorption Spectroscopy

A study of adsorption and absorption mechanisms of copper in palygorskite

Dissolution of Hectorite in Inorganic Acids

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