Imogolite, a Hydrated Aluminium Silicate of Tubular Structure

Cradwick, P. D.; Farmer, V. C.; Russell, J. D.; Masson, C. R.; Wada, Kōji; Yoshinaga, Naganori

doi:10.1038/physci240187a0

Cited by 339 publications

(401 citation statements)

References 8 publications

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“…In addition, the number and shape of the two main XANES edge maxima indicate similar Alv~ environments in imogolite and allophanes, regardless of their A1/Si ratios. These data agree with the model of Parfitt and Henmi (1980) in which Al-rich allophane and imogolite have close structure, the former being only more disordered at long-range distance, as the latter has a long-range structure with a repeat distance of 8.40/~ along the tube axis (Cradwick et al, 1972). The A1-K XANES spectra of the imogolite and allophanes, which yield two resolved main components and a maximum position near 1568 eV, are close to those in pyrophyllite and dioctahedral smectites and suggest that A1 vI occupies only one octahedral site in these short-range ordered compounds.…”

Section: Resultssupporting

confidence: 80%

“…This variation has been quantified as explained above, as the average energy position and width of the four components used in the fitting procedure show small standard deviations (Table 5). In imogolite, aluminum only occurs as AI w. This is in agreement with the structure of imogolite based on C2oh symmetry (Cradwick et al, 1972). In allophanes, we estimated the AlW/A1 '~ ratio (Table 5) by reference to the imogolite spectrum (AlW/A1 t~ = 0).…”

Section: Al-k-edge Xanessupporting

confidence: 63%

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²⁷Al Mas NMR and Aluminum X-Ray Absorption Near Edge Structure Study of Imogolite and Allophanes

Ildefonse

Kirkpatrick

Montez

et al. 1994

Clays and clay miner.

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Abstract--This paper compares the results of 27A1 nuclear magnetic resonance spectroscopy (NMR) and AI-K-edge X-ray Absorption Near Edge Structure (XANES) of natural imogolite and allophanes and some crystaUine reference minerals. All soil allophanes studied contain 4-coordinated A1 (AlIV). The highest relative proportion of A1TM, 21% of the total AI, was found in Si-rich allophane. This value is close to that found in spring allophanes, which were previously considered to be different from soil allophanes. For a quantitative determination of the AlXV/Alt~ ratio, NMR is more reliable than XANES, because of the sensitivity of the chemical shift to low A1TM concentrations, but XANES may be used even if paramagnetic impurities (mostly Fe) are present. Al-K XANES also yields more information than NMR on the local environment of A1 vi and especially site multiplicity. AI w XANES of imogolite and allophanes are similar regardless of the AI/Si ratio. They yield two well-resolved resonances with maxima near 1568 and 1570 eV, which indicates the presence of a unique A1 vt site by comparison with crystalline references. The presence of only one A1 w site indicates that imogolite and allophanes have an octahedral sheet with a structure similar to 2/1 dioctahedral phyllosilicates but different from gibbsite or kaolinite, previously considered as structural analogues. The 27AltV MAS NMR peak maxima of allophanes are between 58.6 and 59.8 ppm, in the range observed for crystalline and amorphous framework aluminosilicates, and less positive than those of sheet silicates, which are typically in the range 65-75 ppm. 27A1-H 1 CPMAS NMR spectra suggest that both A1TM and A1 vI have A1-O-H linkages.

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Section: Resultssupporting

confidence: 80%

Section: Al-k-edge Xanessupporting

confidence: 63%

²⁷Al Mas NMR and Aluminum X-Ray Absorption Near Edge Structure Study of Imogolite and Allophanes

Ildefonse

Kirkpatrick

Montez

et al. 1994

Clays and clay miner.

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“…It is possible that reactive Si-OH groups are associated with defects in the imogolite structure. In any case, the model of Cradwick et al (1972) suggests that negatively charged sites will be present inside the imogolite tubes.…”

Section: Nature Of Titratable Sites In Imogolite and Allophanementioning

confidence: 99%

Adsorption of Cations on Imogolite and their Effect on Surface Charge Characteristics

Harsh

Traina

Boyle

et al. 1992

Clays and clay miner.

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Abstract--Noncrystalline aluminosilicates termed allophane and imogolite are common constituents of spodosols, soils derived from volcanic ash, and many inceptisols. The surface charge characteristics of their synthetic analogues may be used to better understand their ion retention properties. In this study, we determined the point of zero salt effect (PZSE) by potentiometric titration of allophanes with A1/Si ratios of 1.12, 1.52, and 2.04 and of imogolite with an A1/Si ratio of 2.02. We also used microelectrophoresis to determine the point of zero charge (PZC) at the particle shear plane for the same materials in C1 solutions of Li, Na, Cs, and tetramethyl ammonium. The PZSE decreased with decreasing A1/Si ratio for the allophanes, but the imogolite PZSE was much lower than that of the allophane with 2.04 A1/Si. The PZC was always higher than the PZSE of the same material, especially for imogolite. The results are best explained if cations reside within the hollow tubes ofimogolite. This conclusion is supported by a fluorescence study that showed that only quenchers smaller than the inner diameter of the imogolite tube could fully quench Ce-imogolite.

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“…7 It is known to be composed of neutral tubes (the details of the structure of these tubes are, however, not understood). 8 Another aluminosilicate which can be viewed as belonging to the tube group, since it has an aluminosilicate ion that can be considered to be tubular, is bavenite, Ca 4 Be 2 Al 2 SiO 2 6 (OH) 2 .9-11…”

Section: 5mentioning

confidence: 99%

Synthesis of the tube silicate litidionite and structural relationships between it and some other silicates

Hefter¹,

Kenney²

1982

Inorg. Chem.

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Imogolite, a Hydrated Aluminium Silicate of Tubular Structure

Cited by 339 publications

References 8 publications

²⁷Al Mas NMR and Aluminum X-Ray Absorption Near Edge Structure Study of Imogolite and Allophanes

²⁷Al Mas NMR and Aluminum X-Ray Absorption Near Edge Structure Study of Imogolite and Allophanes

Adsorption of Cations on Imogolite and their Effect on Surface Charge Characteristics

Synthesis of the tube silicate litidionite and structural relationships between it and some other silicates

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Imogolite, a Hydrated Aluminium Silicate of Tubular Structure

Cited by 339 publications

References 8 publications

27Al Mas NMR and Aluminum X-Ray Absorption Near Edge Structure Study of Imogolite and Allophanes

27Al Mas NMR and Aluminum X-Ray Absorption Near Edge Structure Study of Imogolite and Allophanes

Adsorption of Cations on Imogolite and their Effect on Surface Charge Characteristics

Synthesis of the tube silicate litidionite and structural relationships between it and some other silicates

Contact Info

Product

Resources

About

²⁷Al Mas NMR and Aluminum X-Ray Absorption Near Edge Structure Study of Imogolite and Allophanes

²⁷Al Mas NMR and Aluminum X-Ray Absorption Near Edge Structure Study of Imogolite and Allophanes