Aluminium coordination and structural disorder in halloysite and kaolinite by <sup>27</sup>Al NMR spectroscopy

Newman, Roger H.; Childs, C. W.; Churchman, G. Jock

doi:10.1180/claymin.1994.029.3.01

Cited by 43 publications

(15 citation statements)

References 17 publications

(20 reference statements)

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“…The 27A1-MAS-NMR confirms a disorder in kaolinite structure arising as a result of Al-vacancy displacements in the octahedral sheet (Newman et al, 1994). The three spectra of kaolinite samples have a similar shape and no major differences between the kaolinite spectrum and the halloysite spectrum could be detected.…”

Section: Discussionsupporting

confidence: 50%

“…The full-width-at halfmaximum (FWHM) of this line increases from 9.4 ppm for well-ordered kaolinite to 10.00 ppm for halloysite, whereas for poorly-ordered kaolinite it is 10.8 ppm. The increasing FWHM of this resonance is due to a larger distribution of quadropole coupling parameters and isotropic chemical shifts brought by structural disorder that arises primarily as the result of Al-vacancy displacements in the octahedral sheet (Newman et aL, 1994). In addition to the six-coordinated aluminum peak, the spectrum of poorly-ordered kaolinite displays a resonance at --70 ppm attributed to four-coordinated aluminum.…”

Section: Zal-magic Angle Spinning Neutron Magnetic Resonancementioning

confidence: 97%

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Kaolinite to Halloysite-7 Å Transformation in the Kaolin Deposit of São Vicente De Pereira, Portugal

Boboş

Duplay²,

Rocha

et al. 2001

Clays and clay miner.

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Abstract~he transformation of kaolinite to halloysite-7 .~ was identified in the kaolin deposit of S~o Vicente de Pereira (SVP), using X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and transmission electron microscopy (TEM). Both the 02,1 i and 13,13 reflections show changes in the XRD patterns along the kaolinite to halloysite-7 ,~ transition, and the FTIR spectra show changes corresponding to both OH and Si-O-stretching bands and Al-O-Si-bending vibrations. The interlayer water content in the kaolinite structure increases during transition. The two-layer periodicity of well-ordered kaolinite and rolling up of kaolinite plates are observed using hi~h-resolution transmission electron microscopy (HRTEM). Long and short tubes exhibit halloysite-7 A. No structural Fe was found in the kaolinite samples. Analytical electron microscopy (AEM) indicates no substitution of AP § for Si 4+. The Si/A1 ratio shows values of --1 for the kaolinite and rolled kaolinite plates. The 27A1 magic angle spinning neutron magnetic resonance (MAS-NMR) spectra display a resonance centered at -1 ppm, assigned to six-coordinated aluminum. The transformation of kaolinite to halloysite-7 A. is controlled by surface reaction.

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Section: Discussionsupporting

confidence: 50%

Section: Zal-magic Angle Spinning Neutron Magnetic Resonancementioning

confidence: 97%

Kaolinite to Halloysite-7 Å Transformation in the Kaolin Deposit of São Vicente De Pereira, Portugal

Boboş

Duplay²,

Rocha

et al. 2001

Clays and clay miner.

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“…This negative correlation between Fe content and LB contrasts the observation and conclusions of Newman et al (1994). They suggest paramagnetic dipole-dipole interactions between structural Fe and A1 as the main cause for line broadening in halloysites.…”

Section: Nmr Line Broadening Effectscontrasting

confidence: 52%

Effects of Secondary Iron Phases on Kaolinite ²⁷Al MAS NMR Spectra

Schroeder

Pruett²,

Hurst

1998

Clays and clay miner.

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Abstract--Eight kaolinite and 2 halloysite samples were analyzed using 27A1 magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopy, chemical analysis and magnetic susceptibility to understand the effect of isomorphously substituted Fe 3+ and secondary Fe phases on the NMR signal. Known additions of goethite and hematite were made to determine the response of kaolinite 27A1 MAS NMR spectra and sample magnetic susceptibilities.Results from high field (11.7 T) NMR studies show positive correlations between 1) Fe content, 2) magnetic susceptibility and 3) relative intensity of the spinning side band (SSB) to central band (CB) ratio. No correlation is observed between the mass-corrected NMR spectral intensity and Fe content. Comparative high/low field (11.7 T/8.46 T) NMR studies show a decrease in the relative ratio of line broadening with increasing Fe content. Projected trends of known additions of hematite and goethite versus magnetic susceptibility extrapolate back to zero y intercepts that have Fe concentrations higher than actually measured.Absolute intensity observations have negative implications for the use of 27A1 MAS NMR spectroscopy in assessing Fe-ordering in kaolinites. First, high-energy, short (~/6 of ~/2 solutions) pulse sequences do not produce reliable quantitative data needed to assess paramagnetic line-broadening affects caused by different Fe-ordering clustering scenarios. The lack of perfect correlation between SSB/CB, Fe content and magnetic susceptibility indicates that differences exist with respect to 1) the amount of isomorphously substituted Fe, 2) the ordering of the Fe within kaolinite, 3) the concentration of secondary Fe phases and 4) magnetic susceptibility of the secondary Fe assemblage. Variability of line-width ratios at different field strengths indicates an increasing second-order quadrupole effect (SOQE) with increasing Fe. Finally, the difference between the observed Fe content and that predicted from magnetic susceptibility measurements suggest that magnetic domain properties of secondary Fe phases behave differently from Fe domains bound in kaolinite.

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“…Due to the extremely small size of Hal nanotubes, it also had excellent boundaries and surface activity, so that its CEC value increased with decreasing sizes. Bailey (1990) considered Al 3+ substituted Si 4+ cations in the halloysite tetrahedron to produce negative charges [51], however, the 27 Al NMR by Newman et al (1994) [52] indicated that halloysite has similar Al(IV) content as standard kaolinite. This charge was balanced by the interlayer surface hydration exchangeable cations.…”

Section: Cec Analysismentioning

confidence: 99%

Mineralogy and Physico-Chemical Data of Two Newly Discovered Halloysite in China and Their Contrasts with Some Typical Minerals

Ouyang

Zhang

et al. 2018

Minerals

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Abstract:We report in this article the systematical acquisition of physico-chemical parameters for two newly discovered halloysite (Hal) minerals from Shiyan and Tongling in China. As the comparative reference, the data from Hal in Linfen, Chenxi, and the salt lake in Australia (samples were abbreviated as Hal-AU, Hal-SY, Hal-LF, Hal-CX and Hal-TL, respectively) were also investigated using X-ray diffraction (XRD), scanning electronic microscopy (SEM), transmission electron microscopy (TEM), Fourier transformation infrared spectroscopy (FTIR), differential scanning calorimetry-thermogravimetry (DSC-TG), X-ray fluorescence, surface zeta potential measurements and N 2 adsorption-desorption isotherms. The newly found minerals were probably formed in hydrothermal leaching and sedimentary circumstances. The Hal-SY contains 7 Å-halloysite and dickite, while Hal-TL contains 10 Å-halloysite with some alunite (similar with Hal-CX). Other impurities found in the samples include quartz, gibbsite, iron oxide and anatase. All of them showed tubular morphology with diameter in the range of 30-90 nm and a length of 300-2500 nm, while the Hal-SY has the largest inner diameter to about 150 nm. Specific surface areas varied from 26.0~59.0 m 2 ·g −1 . In addition, maximum CEC (cation exchange capacity) of the newly found Hal was about 40 cmol/kg, while that of Hal-AU was relatively low (8 cmol/kg) due to the sedimentary nature of Salt Lake circumstances. The surface charge was predominantly negative over most of the relevant pH range (>2.0). It can be concluded that the different morphology and impurity content of halloysite will greatly affect the surface area, pore volume, and cationic exchange capacity (CEC) of the minerals.

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Aluminium coordination and structural disorder in halloysite and kaolinite by ²⁷Al NMR spectroscopy

Cited by 43 publications

References 17 publications

Kaolinite to Halloysite-7 Å Transformation in the Kaolin Deposit of São Vicente De Pereira, Portugal

Kaolinite to Halloysite-7 Å Transformation in the Kaolin Deposit of São Vicente De Pereira, Portugal

Effects of Secondary Iron Phases on Kaolinite ²⁷Al MAS NMR Spectra

Mineralogy and Physico-Chemical Data of Two Newly Discovered Halloysite in China and Their Contrasts with Some Typical Minerals

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Aluminium coordination and structural disorder in halloysite and kaolinite by 27Al NMR spectroscopy

Cited by 43 publications

References 17 publications

Kaolinite to Halloysite-7 Å Transformation in the Kaolin Deposit of São Vicente De Pereira, Portugal

Kaolinite to Halloysite-7 Å Transformation in the Kaolin Deposit of São Vicente De Pereira, Portugal

Effects of Secondary Iron Phases on Kaolinite 27Al MAS NMR Spectra

Mineralogy and Physico-Chemical Data of Two Newly Discovered Halloysite in China and Their Contrasts with Some Typical Minerals

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Aluminium coordination and structural disorder in halloysite and kaolinite by ²⁷Al NMR spectroscopy

Effects of Secondary Iron Phases on Kaolinite ²⁷Al MAS NMR Spectra