Dissolution kinetics of calcined kaolinite and montmorillonite in alkaline conditions: Evidence for reactive Al(V) sites

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Dissolution kinetics of calcined kaolinite and montmorillonite in alkaline conditions : Evidence for reactive Al(V) sites. / Garg, Nishant; Skibsted, Jørgen.

In: Journal of the American Ceramic Society, Vol. 102, No. 12, 12.2019, p. 7720-7734.

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Garg, Nishant ; Skibsted, Jørgen. / Dissolution kinetics of calcined kaolinite and montmorillonite in alkaline conditions : Evidence for reactive Al(V) sites. In: Journal of the American Ceramic Society. 2019 ; Vol. 102, No. 12. pp. 7720-7734.

Bibtex

@article{0693a7566a36431c8b0f6adc88e58a24,
title = "Dissolution kinetics of calcined kaolinite and montmorillonite in alkaline conditions: Evidence for reactive Al(V) sites",
abstract = "Calcined clays are attracting significant research attention because of their potential to partially replace CO2-intensive portland cement. This potential depends largely on their reactivity, especially dissolution under alkaline conditions. Identification and characterization of reactive sites in these amorphous calcined clays has so far not been reported. Here, we investigate kaolinite (1:1 clay) and montmorillonite (2:1 clay) calcined at different temperatures under alkaline conditions (0.1 mol/L NaOH). Solution compositions are determined in batch dissolution experiments, whereas 27Al and 29Si MAS and CP/MAS NMR are used to investigate the structure of the undissolved residues to identify sites that are reactive and undergo preferential dissolution. The highest Si and Al dissolution rates for kaolinite are observed for calcination at 700°C, corresponding to the temperature of optimum reactivity, whereas the rates decrease and become increasingly incongruent at higher temperatures. The Si and Al dissolution rates for optimally calcined kaolinite are 4 and 12 times larger than the corresponding rates for optimally calcined montmorillonite, in accord with the much higher reactivity of calcined kaolinite compared to calcined 2:1 clays. This superior performance of kaolinite is explained by novel 27Al NMR results, which show strong evidence for preferential dissolution of highly reactive pentahedral aluminum sites.",
keywords = "ACTIVATION, BASE-LINE, GLASS, HYDROLYSIS, LEACHED LAYERS, METAKAOLIN, PH, POZZOLANIC ACTIVITY, SILICATE MINERALS, SOCIETY SOURCE CLAYS, dissolution, kaolinite, montmorillonite, pentahedral aluminum, solid-state NMR",
author = "Nishant Garg and J{\o}rgen Skibsted",
year = "2019",
month = dec,
doi = "10.1111/jace.16663",
language = "English",
volume = "102",
pages = "7720--7734",
journal = "Journal of the American Ceramic Society",
issn = "0002-7820",
publisher = "Wiley-Blackwell Publishing",
number = "12",

}

RIS

TY - JOUR

T1 - Dissolution kinetics of calcined kaolinite and montmorillonite in alkaline conditions

T2 - Evidence for reactive Al(V) sites

AU - Garg, Nishant

AU - Skibsted, Jørgen

PY - 2019/12

Y1 - 2019/12

N2 - Calcined clays are attracting significant research attention because of their potential to partially replace CO2-intensive portland cement. This potential depends largely on their reactivity, especially dissolution under alkaline conditions. Identification and characterization of reactive sites in these amorphous calcined clays has so far not been reported. Here, we investigate kaolinite (1:1 clay) and montmorillonite (2:1 clay) calcined at different temperatures under alkaline conditions (0.1 mol/L NaOH). Solution compositions are determined in batch dissolution experiments, whereas 27Al and 29Si MAS and CP/MAS NMR are used to investigate the structure of the undissolved residues to identify sites that are reactive and undergo preferential dissolution. The highest Si and Al dissolution rates for kaolinite are observed for calcination at 700°C, corresponding to the temperature of optimum reactivity, whereas the rates decrease and become increasingly incongruent at higher temperatures. The Si and Al dissolution rates for optimally calcined kaolinite are 4 and 12 times larger than the corresponding rates for optimally calcined montmorillonite, in accord with the much higher reactivity of calcined kaolinite compared to calcined 2:1 clays. This superior performance of kaolinite is explained by novel 27Al NMR results, which show strong evidence for preferential dissolution of highly reactive pentahedral aluminum sites.

AB - Calcined clays are attracting significant research attention because of their potential to partially replace CO2-intensive portland cement. This potential depends largely on their reactivity, especially dissolution under alkaline conditions. Identification and characterization of reactive sites in these amorphous calcined clays has so far not been reported. Here, we investigate kaolinite (1:1 clay) and montmorillonite (2:1 clay) calcined at different temperatures under alkaline conditions (0.1 mol/L NaOH). Solution compositions are determined in batch dissolution experiments, whereas 27Al and 29Si MAS and CP/MAS NMR are used to investigate the structure of the undissolved residues to identify sites that are reactive and undergo preferential dissolution. The highest Si and Al dissolution rates for kaolinite are observed for calcination at 700°C, corresponding to the temperature of optimum reactivity, whereas the rates decrease and become increasingly incongruent at higher temperatures. The Si and Al dissolution rates for optimally calcined kaolinite are 4 and 12 times larger than the corresponding rates for optimally calcined montmorillonite, in accord with the much higher reactivity of calcined kaolinite compared to calcined 2:1 clays. This superior performance of kaolinite is explained by novel 27Al NMR results, which show strong evidence for preferential dissolution of highly reactive pentahedral aluminum sites.

KW - ACTIVATION

KW - BASE-LINE

KW - GLASS

KW - HYDROLYSIS

KW - LEACHED LAYERS

KW - METAKAOLIN

KW - PH

KW - POZZOLANIC ACTIVITY

KW - SILICATE MINERALS

KW - SOCIETY SOURCE CLAYS

KW - dissolution

KW - kaolinite

KW - montmorillonite

KW - pentahedral aluminum

KW - solid-state NMR

UR - http://www.scopus.com/inward/record.url?scp=85068474564&partnerID=8YFLogxK

U2 - 10.1111/jace.16663

DO - 10.1111/jace.16663

M3 - Journal article

AN - SCOPUS:85068474564

VL - 102

SP - 7720

EP - 7734

JO - Journal of the American Ceramic Society

JF - Journal of the American Ceramic Society

SN - 0002-7820

IS - 12

ER -