Atomistic-Scale Energetic Heterogeneity on a Membrane Surface.

Knowing the energetic topology of a surface is important, especially with regard to membrane fouling. In this study, molecular computations were carried out to determine the energetic topology of a polyvinylidene fluoride (PVDF) membrane with different surface wettability and three representative probe molecules (namely argon, carbon dioxide and water) of different sizes and natures. Among the probe molecules, water has the strongest interaction with the PVDF surface, followed by carbon dioxide and then argon.

Enantiomeric Separation of Racemic Mixtures Using Chiral-Selective and Organic-Solvent-Resistant Thin-Film Composite Membranes.

Membrane-based chiral separation has emerged as a promising method for the efficient separation of chiral molecules. Ideally, the membranes should be able to achieve good enantioselectivity, while maintaining high stability in harsh solvents. However, engineering membranes for chiral molecular separation in harsh organic solvent environments is still a big challenge.

Microscopic insights into water adsorption in carbon nanopores - the role of acidic and basic functional groups and their configurations.

Functional groups (FGs) in porous carbon play a pivotal role in water adsorption by nucleating water clusters followed by their coalescence, the process in which precursors are used for filling the confined space typically in the reduced pressure range of 0.3-0.8.

Competitive and Synergistic Adsorption of Mixtures of Polar and Nonpolar Gases in Carbonaceous Nanopores.

Most adsorption applications involve mixtures, yet accurate predictions of the adsorption of mixtures remain challenging, in part due to the inability to account for the interplay between adsorbate-adsorbate and adsorbate-adsorbent interactions. This study involves a comprehensive Monte Carlo simulation of the adsorption of two groups of mixtures (namely, supercritical and subcritical ones) in carbon nanopores and quantifies Henry's constants, isotherms, energetics, and density distributions in the pores. When interadsorbate interactions are negligible (e.

The physisorption mechanism of SO on graphitized carbon.

Sulfur dioxide (SO2) in flue gases emitted from fossil fuel power plants dramatically reduces the CO2 capture efficiency via adsorption, which is due to the potential reaction of SO2 with basic functional groups on the adsorbent. Physisorption rather than chemisorption is preferred, because adsorbents can be more easily regenerated by either reducing the pressure or increasing the temperature. Carbon is a suitable adsorbent for SO2 capture and widely used, and therefore it is important to study SO2 adsorption onto carbon with the Monte Carlo simulation to provide microscopic details to demarcate the roles of the basal plane of the graphene layer and the functional groups in adsorption.

A simulation study of the low temperature phase diagram of the methane monolayer on graphite: a test of potential energy functions.

We have used molecular simulation with two intermolecular potential models, TraPPE-UA and TraPPE-EH, the latter of which accounts for the tetrahedral shape, to study the effects of shape on methane adsorption on graphite. Both models give good descriptions of the vapour-liquid equilibria in the bulk phase, but adsorption on graphite is better described by the TraPPE-EH model. Molecular configurations in the monolayer, show the variation with temperature of the registry sites for the carbon and hydrogen atoms of the methane molecules.

On the canonical isotherms for bulk fluid, surface adsorption and adsorption in pores: A common thread.

Kinetic Monte Carlo simulated isotherms calculated in the canonical ensemble, at temperatures below the critical temperature, for bulk fluid, surface adsorption and adsorption in a confined space, show a van der Waals (vdW) loop with a vertical phase transition between the rarefied and dense spinodal points at the co-existence chemical potential, µ. Microscopic examination of the state points on this loop reveals features that are common to these systems. At state points with chemical potentials greater than μ the microscopic configurations show clusters, which coalesce to form two co-existing phases along the vertical section of the loop (the coexistence line).

On the growth of argon clusters on a weak adsorbent decorated with patches.

Much attention has been paid to understanding the clustering mechanism of water adsorbed on carbonaceous adsorbents. Adsorbed water forms clusters around strong sites, such as functional groups and surface defects, and these clusters then coalesce if the strong sites are sufficiently close to each other. Simulations of water adsorption are notoriously time consuming because of the slow relaxation of the strongly-directional hydrogen bonds.

The role of adsorbate size on adsorption of Ne and Xe on graphite.

We have carried out an extensive grand canonical Monte Carlo simulation to investigate the adsorption of neon and xenon on graphite. The adsorbate collision diameters of neon and xenon are smaller and greater respectively, than the commensurate graphite lattice spacing λ=3×3R30 of 0.426 nm.

Water adsorption on carbon - A review.

Water adsorption on carbonaceous materials has been studied increasingly in the recent years, not only because of its impact on many industrial processes, but also motivated by a desire to understand, at a fundamental level, the distinctive character of directional interactions between water molecules, and between water molecules and other polar groups, such as the functional groups (FGs) at the surfaces of graphene layers. This paper presents an extensive review of recent experimental and theoretical work on water adsorption on various carbonaceous materials, with the aim of gaining a better understanding of how water adsorption in carbonaceous materials relates to the concentration of FGs, their topology (arrangement of the groups) and the structure of the confined space in porous carbons. Arising from this review we are able to propose mechanisms for water adsorption in carbonaceous materials as the adsorbate density increases.

A GCMC simulation and experimental study of krypton adsorption/desorption hysteresis on a graphite surface.

Adsorption isotherms and isosteric heats of krypton on a highly graphitized carbon black, Carbopack F, have been studied with a combination of Monte Carlo simulation and high-resolution experiments at 77K and 87K. Our investigation sheds light on the microscopic origin of the experimentally observed, horizontal hysteresis loop in the first layer, and the vertical hysteresis-loop in the second layer, and is found to be in agreement with our recent Monte Carlo simulation study (Diao et al., 2015).