Non-Fickian adsorption rate behaviour of some carbon molecular sieves

LaCava, A.I.; Koss, V. A.; Wickens, Denys A

doi:10.1016/0950-4214(89)80003-9

Cited by 57 publications

(45 citation statements)

References 10 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…Assuming that the surface concentration of a vapor is constant and that the diffusion is controlled by the concentration gradient through the particle, the kinetic of diffusion can be expressed (LaCava et al 1989) by the empirical diffusion equation. where M t is the vapor uptake at time t, M e is the equilibrium vapor uptake, K is adsorbate-adsorbent interaction coefficient and n is the diffusional exponent.…”

Section: Empirical Diffusion Modelmentioning

confidence: 99%

Isotherms, kinetics and thermodynamics for adsorption of pyridine vapors on modified activated carbons

2015

View full text Add to dashboard Cite

The adsorption isotherms of pyridine have been determined gravimetrically on different samples of granulated, fibrous and spherical activated carbons. Several chemical treatments such as oxidation, degassing and impregnation have been carried out on as-received activated carbon cloth (ACC) so as to modify the surface characteristics of the activated carbon. The porous and chemical structure of modified and unmodified activated carbons has been characterised by XRD, TGA-DTG, SEM and pore size distribution techniques. The adsorption increases on oxidation while decreases on degassing which can be correlated to increase and decrease in the concentration of surface oxygen groups. Loading with Ag ? and Cu 2? increases the adsorption of pyridine compared with the unloaded sample while loading with Cr 6? decreases the adsorption of these vapors. The adsorption-desorption branches of pyridine vapors on metal impregnated do not meet even at zero relative vapor pressure indicating the chemisorption or other specific interactions. The adsorption kinetics data has been examined using the linear driving force and empirical diffusion models. The initial decrease in isosteric enthalpy of adsorption for modified and unmodified ACC indicates the effect of surface heterogeneity and later increase indicates the influence of lateral interactions between adsorbate molecules. The results suggest that the adsorption of pyridine involves the physisorption as well as specific interactions with carbon oxygen functional groups and metal complexes present on the carbon surface.

show abstract

Section: Empirical Diffusion Modelmentioning

confidence: 99%

Isotherms, kinetics and thermodynamics for adsorption of pyridine vapors on modified activated carbons

2015

View full text Add to dashboard Cite

show abstract

“…The magnitude of the activation energy for micropore diffusion, derived from the temperature dependence of the diffusivity, can be as large as the isosteric heat of adsorption [29]. The characteristics of transport through the pore mouth barrier include a nonFickian uptake which is often described by a linear driving force model [8][9][10][11][12]. The rate constant derived from the linear driving force model displays an Arrhenius temperature dependence which yields an activation energy that is greater than the isosteric heat of adsorption [15][16][17].…”

Section: Transport Kineticsmentioning

confidence: 99%

“…There have been a variety of studies which identify the transport of species into the micrograin which generally obeys a Fickian diffusion process for homogeneous materials [7]. Several studies have shown that the pore mouth creates a barrier to penetration which generates a resistance in series with the micropore diffusion process through the grains [8][9][10][11][12]. Small molecules experience only a small activation energy for transport through this barrier as is exemplified by carbon dioxide transport in CMS [13].…”

Section: Introductionmentioning

confidence: 99%

Adsorption equilibrium and transport kinetics for a range of probe gases in Takeda 3A carbon molecular sieve

Rutherford

Coons

2005

Journal of Colloid and Interface Science

View full text Add to dashboard Cite

“…Pressure was measured continuously using a Datametrics pressure transducer and recorded with a HewlettPackard data-acquisition system (Koss et al, 1986;LaCava et al, 1989b). At 25°C the oxygen and nitrogen monolayer capacity is 1.8 X kmol/kg CMS, and the adsorption and desorption kinetic constants are, respectively, 7.684 x lo-, m3/kmol s and 0.0176 L/s for oxygen, and 3 .…”

Section: Model Equationsmentioning

confidence: 99%

“…The rate of uptake of gases by non-Fickian carbon molecular sieves is described in terms of the slit-potential rate model (LaCava et al, 1989b), which considers the slit-cavity structure of the carbon molecular sieve. Under certain conditions, the Langmuir adsorption rate expression is a good approximation to the slit-potential-rate model, and it is used in the present work.…”

Section: Theoretical Modelmentioning

confidence: 99%

High‐purity Nitrogen by pressure‐swing adsorption

Shirley¹,

Lemcoff²

1997

AIChE Journal

View full text Add to dashboard Cite

The separation of air for nitrogen production can be cam'ed out by pressure-swing adsorption over a carbon molecular sieve. The separation is kinetically based since the equilibrium adsorption of both oxygen and nitrogen is vety similar, but the oxygen is adsorbed faster. Several theoretical and experimental studies have been reported, but mainly dealing with nitrogen purities below 99.9%. The objective of this article is to study experimentally the effect of different process variables on the performance of a rate-induced PSA process in the high-purity region. The effect of cycle time on both the yield and the specifc product per unit cycle become more significant as the purity increases. On the other hand, the specifc feed per unit cycle is almost insensitive to product purity, particularly as the cycle time increases. These results agree vety well with predictions from a theoretical model.

show abstract

Non-Fickian adsorption rate behaviour of some carbon molecular sieves

Cited by 57 publications

References 10 publications

Isotherms, kinetics and thermodynamics for adsorption of pyridine vapors on modified activated carbons

Isotherms, kinetics and thermodynamics for adsorption of pyridine vapors on modified activated carbons

Adsorption equilibrium and transport kinetics for a range of probe gases in Takeda 3A carbon molecular sieve

High‐purity Nitrogen by pressure‐swing adsorption

Contact Info

Product

Resources

About