A molecular dynamics study of the swelling patterns of Na/Cs-montmorillonites and the hydration of interlayer cations

Zhang

et al. 2018

Trans. Tianjin Univ.

Graphene oxide (GO) contains numerous functional groups that facilitate the intercalation of polar solvents. The properties and applications of GO are closely related to its interlayer spacing. We report on the changes in the interlayer spacing of GO after the adsorption of water molecules and the polar organic solvents C 2 H 6 O 2 (EG), C 3 H 7 NO (DMF), C 5 H 9 NO (NMP). Experiments were conducted to investigate the variations in the functional groups and structure of GO after solvent adsorption, and they play a vital role in modeling and verifying the results of molecular dynamics simulation. The most stable GO structures are obtained through molecular dynamics simulation. The expansion of the interlayer spacing of GO after the adsorption of monolayer solvent molecules corresponds to the minimum three-dimensional size of the solvent molecules. The spatial arrangement of solvent molecules also contributes to the changes in interlayer spacing. Most adsorbed molecules are oriented parallel to the carbon plane of GO. However, as additional molecules are adsorbed into the interlaminations of GO, the adsorbed molecules are oriented perpendicular to the carbon plane of GO, and a large space forms between two GO interlayers. In addition, the role of large molecules in increasing interlayer spacing becomes more crucial than that of water molecules in the adsorption of binary solvent systems by GO.

Section: Relationship Between the Interlayer Spacing Of Go And The Sisupporting

confidence: 69%

Effects of Solvent Molecules on the Interlayer Spacing of Graphene Oxide

Zhang

et al. 2018

Trans. Tianjin Univ.

“…During the simulation, the simple point charge (SPC) model was used to represent the interaction of H 2 O [41,42], in which the geometrical structure of these molecules is rigid, the bond length is 1.0 Å and bond angle is 109.5 • [43]. The CLAYFF force field which has been proved to work very well in previous simulation studies about MT was employed to describe the interatomic potential for Na-MT-water systems [44][45][46][47]. The short range van der Waals interaction was calculated based on the atom-based method, and the long-range electrostatic interaction was calculated by the Ewald summation method [48,49].…”

Section: Simulation Parametersmentioning

confidence: 99%

Effect of Crystal Chemistry Properties on the Distribution Characteristics of H2O and Na+ in Na-Montmorillonite Interlayer Space: Molecular Dynamics Simulation Study

et al. 2020

At monolayer hydration state, the spatial distribution of H2O and Na+ in the interlayer of Na-montmorillonite (Na-MT) with different crystal chemistry properties was investigated by the molecular dynamics simulation method. The simulation results show that when layer charge density increases, H2O will move and form hydrogen bonds with O in tetrahedral surfaces (Ot) at a distance of 1.676 ± 0.043 Å. The impact of isomorphic substitution on the relative concentration of H2O depends largely on the layer charge density of Na-MT, when layer charge density is high, H2O move obviously to both sides of Na-MT sheets with the increase of octahedral substitution ratio. Nevertheless, Na+ coordinate with Ot at a distance of 2.38 Å, and the effect of isomorphic substitution ratio on the diffusion of Na+ is opposite to that of H2O. The mobility of both H2O and Na+ decreases with the increase of layer charge density or tetrahedral substitution ratio. The radial distribution function of Na-Ow (O in H2O) shows that the coordination strength between Na+ and Ow decreases with the increase of layer charge density or tetrahedral substitution ratio, and Na+ are hydrated by four H2O at a Van der Waals radius of 2.386 ± 0.004 Å. The research results can provide a theoretical basis for the efficient application of Na-MT at the molecular and atomic levels.

“…When water-based fluids come into contact with the clay minerals in the shale formation, they cause problems like hydration and swelling. When water comes into contact with clay minerals, the negative layers attract water molecules and allow water to adsorb on the interlayer gap. − Swelling of clay can obstruct shale gas production by causing a slew of issues such as particle buildup in the mud, hole collapse, tight holes, drill pipe sticking, pore plugging, reduced permeability, and so on. − Swelling may also lower the diameter of fractures, decreasing the reservoir’s ultimate permeability . Many additives, such as inorganic salts, organic salts, surfactants, amine derivatives, polymers, and others, were added to water-based fluids to prevent these problems.…”

Section: Introductionmentioning

confidence: 99%

Recent Advances in Deep Eutectic Solvents as Shale Swelling Inhibitors: A Comprehensive Review

et al. 2022

Inhibitors have evolved from their primary function of controlling swelling during hydraulic fracturing processes in shale reservoirs. This study provides a comprehensive review of recent deep eutectic solvent (DES) advancements as inhibitors in swelling inhibition techniques. The swelling inhibitory potentials and mechanisms of DESs have been studied analytically and compared to existing conventional inhibitors. The functional effects of concentration, temperature, and types of DES are explored. Data on the effect of DES on rheology, swelling, zeta potential, shale cutting recovery, surface tension, particle size distribution, XRD, and FTIR analyses are presented. Along with preparation procedures, environmental concerns and applications of DESs in several fields are discussed. This study suggests that DESs are preferable swelling inhibitors due to their inhibitory performance, cost-effectiveness, and environmental friendliness. Moreover, this review includes guidelines and recommendations for selecting and designing DES to inhibit swelling more effectively.