Adsorption of Water Vapor on a Graphitized Carbon Black

Easton, E. Bradley; Machin, William D.

doi:10.1006/jcis.2000.7116

Cited by 43 publications

(52 citation statements)

References 14 publications

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“…Usually such states are not accessible in experiments because bulk condensation occurs without any metastability. A notable exception is work by Easton and Machin [15] for water in graphitized carbon black where special precautions were taken to delay water condensation in the sample cell. In our system the bulk region is comparable in size to the pore space and bulk condensation is nucleated as soon as the pore is filled with liquid.…”

Section: Static Behaviormentioning

confidence: 99%

“…In our system the bulk region is comparable in size to the pore space and bulk condensation is nucleated as soon as the pore is filled with liquid. Presumably this did not happen in the Easton and Machin [15] experiment because of the small size of the porous material sample relative to the bulk region of the sample cell. In studying desorption we switched the bulk over to vapor once the bulk saturation state is reached.…”

Section: Static Behaviormentioning

confidence: 99%

“…In a recent paper one of us discussed the link between wetting, pore condensation and hysteresis for a lattice gas model of fluid in slit a pore [36]. A key effect here is that in adsorption from a vapor at sub-critical temperatures, low density states may persist up to and beyond the bulk saturation pressure, as has been seen in experiments on water adsorbed in graphitized carbon black [15], even though the equilibrium vaporliquid transition lies below bulk saturation. Our calculations reveal the nature of the processes involved during pore filling for a partial wetting system.…”

Section: Introductionmentioning

confidence: 99%

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Modeling Relaxation Processes for Fluids in Porous Materials Using Dynamic Mean Field Theory: An Application to Partial Wetting

Edison

Monson

2009

J Low Temp Phys

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We review a recently developed dynamic mean field theory for fluids confined in porous materials and apply it to a case where the solid-fluid interactions lead to partial wetting on a planar surface. The theory describes the evolution of the density distribution for a fluid in a pore that has contact with the bulk during a quench in the bulk chemical potential. In this way the dynamics of adsorption and desorption can be studied. By focusing on partial wetting situation we can investigate influence of a weaker surface field on the mechanisms of capillary condensation and desorption. We have studied the dynamics of pore filling in a quench of the chemical potential between two states either side of the pore filling step, tracking the density distributions during the process. The pore filling process features an asymmetric density distribution where a liquid droplet appears on one of the walls. The droplet spreads and grows in size and this is followed by the appearance of a liquid bridge between the pore walls (for longer pores two liquid bridges are seen). The density distributions obtained in the dynamics resemble those obtained from static mean field theory in the canonical ensemble for an infinite pore without contact with the bulk.

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Section: Static Behaviormentioning

confidence: 99%

Section: Static Behaviormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Modeling Relaxation Processes for Fluids in Porous Materials Using Dynamic Mean Field Theory: An Application to Partial Wetting

Edison

Monson

2009

J Low Temp Phys

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“…, 1946) and on NC-1 (data of Pierce et al, 1949) Harkins and co-workers (1946) and Pierce and co-workers (1949) studied water adsorption on (presumably) non-porous graphite and found that the isotherms were typical of those expected for graphitized carbon (Figure 15b). The distinction between adsorption on a surface and in a pore can be seen at the onset of adsorption which, for a highly graphitized surface, does not occur until the pressure is close to the saturation vapour pressure (or even beyond, Easton and Machin, 2000). By contrast, adsorption in porous carbons begins at a lower pressure, which can be attributed either to the larger concentration of functional groups or to the nucleation of clusters from water trapped in very small pores (Nguyen and Bhatia, 2011) and the ease with which clusters can grow and merge due to the proximity of the pore walls (Emmett et al, 1948).…”

Section: Water Adsorptionmentioning

confidence: 99%

The interplay between molecular layering and clustering in adsorption of gases on graphitized thermal carbon black – Spill-over phenomenon and the important role of strong sites

Tan

Zeng

et al. 2015

Journal of Colloid and Interface Science

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We analyse in detail our experimental data, our simulation results and data from the literature, for the adsorption of argon, nitrogen, carbon dioxide, methanol, ammonia and water on graphitized carbon black (GTCB), and show that there are two mechanisms of adsorption at play, and that their interplay governs how different gases adsorb on the surface by either: (1) molecular layering on the basal plane or (2) clustering around very strong sites on the adsorbate whose affinity is much greater than that of the basal plane or the functional groups. Depending on the concentration of the very strong sites or the functional groups, the temperature and the relative strength of the three interactions, (a) fluid-strong sites (fine crevices and functional group) (F-SS), (b) fluid-basal plane (FB) and (c) fluid-fluid (FF), the uptake of adsorbate tends to be dominated by one mechanism. However, there are conditions (temperature and adsorbate) where two mechanisms can both govern the uptake. For simple gases, like argon, nitrogen and carbon dioxide, adsorption proceeds by molecular layering on the basal plane of graphene, but for water which represents an extreme case of a polar molecule, clustering around the strong sites or the functional groups at the edges of the graphene layers is the major mechanism of adsorption and there is little or no adsorption on the basal planes because the F-SS and FF interactions are far stronger than the FB interaction. For adsorptives with lower polarity, exemplified by methanol or ammonia, the adsorption mechanism switches from clustering to layering in the order: ammonia, methanol; and we suggest that the bridging between these two mechanisms is a molecular spill-over phenomenon, which has not been previously proposed in the literature in the context of physical adsorption.

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“…The adsorption experiments of Easton and Machin 134 for water on highly graphitized thermal carbon black show that adsorption does not occur at pressures lower than the saturation vapour pressure 134 because, like ammonia, the dispersion interaction between water and basal plane is very weak. This is confirmed by a number of simulation studies of water on basal graphite surfaces 110,135,136 .…”

Section: Adsorption Of Other Adsorbates On Gtcbmentioning

confidence: 98%

Fundamental study of adsorption and desorption process in porous materials with functional groups

Zeng¹

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Adsorption is used in industries for gas separation and purification because of its less energy intensive than other traditional separation processes, such as distillation and gas absorption.However, its effective application depends on the theoretical understanding of the underlying phenomena of adsorption of molecules in porous solid adsorbents. With the advances in molecular simulation techniques, investigation into the microscopic mechanisms of adsorption phenomena can be realized and this will lead to a development of an unambiguo us approach for the characterization of porous solids. This is the aim of this project to understand adsorption and desorption mechanisms in porous materials, especially porous carbons with functional groups because they are not fully studied in the literature.One of the significant points of this thesis is the development of a novel molecular model for porous carbon. Graphitized thermal carbon black (GTCB) was used as model adsorbent modelled as a composite of basal plane of graphene layers with crevices (ultrafine micropores) and oxygen functional groups attached at the edges of the graphene layers. This model was used in adsorption of various gases, and was validated with high resolution experimental data and theoretically analysed with simulation results obtained with a grand canonical Monte Carlo simulation.Excellent agreement between the experimental data and the simulation results has led us to derive the structural properties of GTCB and the nature of the functional group. Furthermore, the experimental Henry constant and the isosteric heat at zero loading (in the region of very low loadings) are described correctly with the Monte Carlo integration of the Boltzmann factor of the pairwise interaction between an adsorbate molecule and the porous carbon. It was found that adsorbate dominantly adsorbs in the fine crevices at very low loadings because of the enhancement of the solid-fluid potential energy, followed by adsorption on the basal plane of graphene layers. This is the case for non-polar fluids, such as argon and nitrogen. On the other hand, polar fluids, such as ammonia and water, the dominance of the functional group in adsorption is manifested, especially water.This novel model for carbon can be extended to describe practical porous carbons containing both micropores (for adsorptive capacity) and mesopores (for transport). Adsorption in mesopores is associated with capillary condensation and evaporation, and the se are commonly used in the literature to derive the mesopore size distribution. For this determination to be realized, the fundamental understanding of condensation and evaporation must be understood, and this is the second objective of this thesis. We chose graphitic slit pores to model the mesopore, and investigated the effects of various parameters on the capillary condensation and evaporation. Grand ii canonical Monte Carlo technique is used to obtain the isotherm and the isosteric heat, and we particularly investigate the mechanisms of adsorpti...

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Adsorption of Water Vapor on a Graphitized Carbon Black

Cited by 43 publications

References 14 publications

Modeling Relaxation Processes for Fluids in Porous Materials Using Dynamic Mean Field Theory: An Application to Partial Wetting

Modeling Relaxation Processes for Fluids in Porous Materials Using Dynamic Mean Field Theory: An Application to Partial Wetting

The interplay between molecular layering and clustering in adsorption of gases on graphitized thermal carbon black – Spill-over phenomenon and the important role of strong sites

Fundamental study of adsorption and desorption process in porous materials with functional groups

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