Clay Nanopores Research Articles

Correction to “How Electrostatics Influences Hydrodynamic Boundary Conditions: Poiseuille and Electro-Osmostic Flows in Clay Nanopores”

ADVERTISEMENT RETURN TO ISSUEPREVAddition/CorrectionNEXTORIGINAL ARTICLEThis notice is a correctionCorrection to “How Electrostatics Influences Hydrodynamic Boundary Conditions: Poiseuille and Electro-Osmostic Flows in Clay Nanopores”A. Boţan*, V. Marry, B. Rotenberg, P. Turq, and B. NoetingerCite this: J. Phys. Chem. C 2013, 117, 39, 20376Publication Date (Web):September 19, 2013Publication History Published online19 September 2013Published inissue 3 October 2013https://doi.org/10.1021/jp408784cCopyright © 2013 American Chemical SocietyRIGHTS & PERMISSIONSArticle Views295Altmetric-Citations5LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (309 KB) Get e-Alerts Get e-Alerts

Phase Transition of Nanoconfined Water in Clay: Positron Annihilation, Nuclear Magnetic Resonance, and Dielectric Relaxation Studies

The structural and dynamical features associated with the phase behavior of water confined in clay nanopores (2D confined water) are studied using positron annihilation spectroscopy, nuclear magnetic resonance, and dielectric relaxation spectroscopy techniques. We report the experimental evidence of a new phase transition (above the bulk freezing point of water) in nanoconfined water, in addition to a low-temperature transition in supercooled water. The study reveals it to be a structural rearrangement of water molecules associated with modification of hydrogen-bonded network. Evidence also suggests the dynamical arrest/immobilization of water layer near the clay platelet surface (bound water molecules) to be associated with this transition. This transition is a manifestation of the role of surface interaction on the phase behavior of confined liquids.

Modeling Sorption and Diffusion of Organic Sorbate in Hexadecyltrimethylammonium-Modified Clay Nanopores – A Molecular Dynamics Simulation Study

Organoclays are highly sorptive engineered materials that can be used as amendments in barrier systems or geosynthetic liners. The performance of confining and isolating the nonpolar organic contaminants by those barrier/lining systems is essentially controlled by the process of organic contaminant mass transport in nanopores of organoclays. In this article, we use molecular dynamics (MD) simulations to study the sorption and diffusion of organic sorbates in interlayers of sodium montmorillonite and hexadecyltrimethylammonium (HDTMA(+))-modified montmorillonite clays. Simulated system consisted of the clay framework, interlayer organic cation, water, and organic sorbate. Their interactions were addressed by the combined force field of ClayFF, constant-valence force field, and SPC water model. Simulation results indicated that in HDTMA coated clay nanopores, diffusion of nonpolar species benzene was slowed because they were subjected to influence of both the pore wall and the HDTMA surfactant. This suggested the nonpolar organic compound diffusion in organophilic clays can be affected by molecular size of diffusive species, clay pore size, and organic surfactant loading. Additionally, a model that connected the diffusion rate of organic compounds in the bulk organoclay matrix with macropores and nanopores was established. The impact of intercalated organic cations on the diffusion dominated mass transport of organic compounds yielded insight into the prediction of the apparent diffusion behavior of organic compounds in organic-modified clays.

How Electrostatics Influences Hydrodynamic Boundary Conditions: Poiseuille and Electro-osmostic Flows in Clay Nanopores.

We report on a molecular simulation study of the origin of nonslip or slip hydrodynamic boundary conditions in clay nanopores, focusing on the role of electrostatics. We simulate hydrodynamic and electro-osmotic flows and consider both charged (montmorillonite) and uncharged (pyrophyllite) clays. We further use two commonly used force fields to analyze the effect of local interactions, in particular, the effect of the polarity of the surface, in addition to the mere effect of the presence or absence of a net charge and counterions. For the 6 nm pore investigated here, the molecular velocity profile can be well described by continuum hydrodynamics only if (a) proper boundary conditions, with a slip or stagnation length determined from molecular simulation, are taken into account and (b) the ionic density profiles from MD simulations are used in the case of electro-osmotic flow, because the Poisson–Boltzmann equation fails to reproduce the ionic profiles, hence the force acting on the fluid. Among the considered force fields, only CLAYFF predicts a hydrophobic pyrophyllite and hydrophilic montmorillonite, as expected from experimental behavior. The nonslip or slip boundary conditions at clay surfaces strongly depend on electrostatic interactions of water molecules with the surface. The presence of a net charge results in an average electric field experienced by surface water molecules between the charged surface and the condensed layer counterions, which influences their orientation. The charge distribution inside the clay layer determines the polarity of the surface and hence the strength of hydrogen bonds donated by water molecules to surface oxygen atoms.

Hydrodynamics in Clay Nanopores

We report a molecular simulation study of hydrodynamics in clay nanopores, with pore widths ranging from 2 to 9 nm. Understanding mass transfer through clay nanopores is necessary in many contexts such as groundwater hydrology, petroleum and gas reservoir engineering, as well as carbon dioxide sequestration or geological disposal of radioactive waste. Grand-canonical Monte Carlo simulations first allow us to determine the water content in the pores. We then analyze the structure and diffusion of confined water using equilibrium molecular dynamics (MD). Finally, nonequilibrium MD allow us to analyze the hydrodynamic behavior of the confined fluid and assess the relevance of continuum hydrodynamics to describe the flow under a pressure gradient. The Navier–Stokes equation, using the density and viscosity of the bulk fluid, provides a reasonable description of the flow provided that the pore width is larger than 3 nm and that a slip boundary condition is used. We determine a slip length of 2.1 A at the clay ...