Atomic-level studies of the depletion in reactive sites during clay mineral dissolution

Sanders, Rebecca L.; Washton, Nancy M.; Mueller, Karl T.

doi:10.1016/j.gca.2012.05.038

Cited by 7 publications

(4 citation statements)

References 59 publications

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“…However, the reliability of the BET surface area normalized dissolution rates may be questioned, as it has been reported in the literature that BET areas of swelling clays like SAz are heavily dependent on the outgassing procedure and may evolve significantly during the dissolution process . The degassing or drying procedure prior to BET measurements is likely to form large aggregates with a reduced apparent surface area which is in contrast to the appearance of the clay particles in dilute solutions where individual clay layers are dominant . Thus, in the evaluation of the applicability of these calcined clay minerals as SCM's in cementitious systems, the raw dissolution rates may be more reliable as opposed to the surface‐normalized dissolution rates.…”

Section: Resultsmentioning

confidence: 99%

“…58 The degassing or drying procedure prior to BET measurements is likely to form large aggregates with a reduced apparent surface area which is in contrast to the appearance of the clay particles in dilute solutions where individual clay layers are dominant. 59 Thus, in the evaluation of the applicability of these calcined clay minerals as SCM's in cementitious systems, the raw dissolution rates may be more reliable as opposed to the surface-normalized dissolution rates. It is also noted that for the comparison of the dissolution rates obtained here and the pozzolanic reactivity data reported earlier, 30 it should be taken into account that the dissolution experiments were performed for the 20-100 μm fraction of particles whereas the reactivity tests used the 20-40 μm fraction.…”

Section: Si Almentioning

confidence: 99%

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

Garg

2019

J Am Ceram Soc

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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.

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Section: Resultsmentioning

confidence: 99%

Section: Si Almentioning

confidence: 99%

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

Garg

2019

J Am Ceram Soc

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“…Most of these studies often involved solid-state NMR (SSNMR) techniques with compounds irreversibly bound on clay surfaces [21,43,44]. For instance, 29 Si NMR combined with cross polarization ( 1 H- 29 Si) under magic angle spinning (CP-MAS) was used to investigate the binding of Fig.…”

Section: Introductionmentioning

confidence: 99%

“…Importantly, in environmental science, a range of interactions exists in soil such that a single NMR experiments will yield only a piece of the puzzle. Therefore, in order to fully understand the dynamics of the system, it is important to perform a range of different NMR experiments, allowing for a better view of the system involved chemicals on clay surfaces [42][43][44]. Importantly, SSNMR techniques require that molecules to be bound tightly on the surface and the samples have to be dry.…”

Section: Introductionmentioning

confidence: 99%

Water-mediated NOE: a promising tool for interrogating interfacial clay–xenobiotic interactions

Soong

Botana

Wang

et al. 2017

Chem. Biol. Technol. Agric.

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Background:The sorption of anthropogenic compounds on clay minerals is a complex molecular process with important implications for the fate of agrochemicals and organic pollutants in the environment. Results:The present study illustrates the use of a water-mediated NOE approach to study clay binding interactions. This method exploits the interfacial water layer on clay surfaces as a hydrogen reservoir for magnetization transfer. The interactions of four different xenobiotics with clay suspension were investigated through this method to demonstrate its capability to screen for the clay-xenobiotic molecular affinity. Further, based onthe NOE build-up rates, epitope map of clay-xenobiotic interactions can be generated, explaining theorientation and mechanism of the interactions. Conclusions:The water-mediated NOE approach has the potential to reveal key insights into the role that interfacial water plays in the binding process, providing a better understanding of the partitioning of anthropogenic compounds from bulk water into aqueous clay suspensions.

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Clay Minerals

Mueller

Sanders

Washton

1996

eMagRes

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Atomic-level studies of the depletion in reactive sites during clay mineral dissolution

Cited by 7 publications

References 59 publications

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

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

Water-mediated NOE: a promising tool for interrogating interfacial clay–xenobiotic interactions

Clay Minerals

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