A quantitative and mechanistic model for the coupling between chemistry and clay hydration

Abstract

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Assessing Diffusion Relaxation of Interlayer Water in Clay Minerals Using a Minimalist Three-Parameter Model

“…This implies that both surface and cation charge–dipole attraction are the origins of clay–water interactions and control water mobility within this nanoconfined region of expandable minerals. Mobility of confined water molecules within the interlayer underpins most of the functional properties of these nanomaterials. , However, how the properties of H 2 O are influenced by their close proximity to the clay-mineral surface itself is still not fully understood, and direct information on the polarization effect on the water molecules dynamics is still missing. − To gain further insight on this question, we used quasi-elastic neutron scattering (QENS) to explore the influence of layer charge resulting from isomorphic substitution within the octahedral sheet of two different types of smectite (dioctahedral Mt and trioctahedral Ht) on diffusion of interlayer water as a function of temperature. To this end, two sodium smectite clay minerals, having the same hydration level, with one water layer in the interlayer space, where Na + is surrounded by 3–3.5 water molecules, were selected for this work, a montmorillonite (Na 0.82 Mg 0.72 Fe 0.4 Si 7.9 Al 2.98 O 20 (OH) 4 , with a layer charge equal to 0.82 e – /unit cell, hereafter Mt) and a hectorite (Na 0.68 Mg 5.42 Li 0.58 Si 7.9 Al 0.1 O 20 (OH) 4 , with a layer charge equal to 0.68 e – /unit cell, hereafter Ht).…”

Effect of Temperature on the Diffusion and Sorption of Cations in Clay Vermiculite

“…These processes significantly affect the amount of water between layers and the distance between layers of clay. 26 …”

“…In humid conditions, interlayer cations can interact with water molecules, forming various complexes depending on their charge and ionic radius. These processes significantly affect the amount of water between layers and the distance between layers of clay …”

“…These processes significantly affect the amount of water between layers and the distance between layers of clay. 26 Clay minerals do not have long-range order due to the small size of the sheet and the peculiarities of their packing, which make it difficult to accurately characterize minerals by experimental methods. Experimental XRD and NMR methods are available to study the effect of cation size and charge on the distances between the basal planes of clay layers.…”

The Impact of Thermal History on Water Adsorption in a Synthetic Nanolayered Silicate with Intercalated Li+ or Na+

“…Water intercalation in swelling clays (also called smectites) is strongly dependent on the nature of the interlayer cation, the layer’s structural charge, temperature, and the surrounding water state (liquid or vapor, and the level of vapor relative humidity). The interlayer cation plays an important role in the water adsorption process, , since water can form different H 2 O–cation complexes depending on the intrinsic charge and ionic radius of the cation, which can significantly change the water adsorption properties. An increase in the layer charge will result in an increase in the number of interlayer cations, but this can also cause a decrease in the interlayer distance and consequently can make the clay material more hydrophobic. , Additionally, it is well established that the dissimilarities in H 2 O uptake and loss between different smectites are related to the manner in which the intercalated cation changes the H-bond network around H 2 O molecules. , …”