The Use of Liquid Phase Adsorption Isotherms for Characterization of Activated Carbons

Ismadji, Suryadi; Bhatia, Suresh K.

doi:10.1006/jcis.2001.7863

Cited by 10 publications

(6 citation statements)

References 25 publications

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“…For most porous materials it may be expected that the coordination number, N , is about 3 or 4, which is consistent with percolation theory characterisations of slit pore carbons. − For uniform networks, one expects a tortuosity of 6 when N = 3 and 5 when N = 4, following eq . However, this will be modified by the presence of a nonuniform PSD because of the short-circuiting effect of pores with high conductance.…”

Section: Resultsmentioning

confidence: 99%

Modeling Pure Gas Permeation in Nanoporous Materials and Membranes

Bhatia

2010

Langmuir

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The low-pressure transport of simple fluids in nanopores and in disordered nanoporous networks is analyzed, using a recent oscillator model theory from the author's laboratory, considering the trajectories of molecules moving in the potential energy field of the fluid-pore wall interaction. The scaling behavior of the single-pore theory is discussed, and it is shown that the Knudsen model provides an upper bound to the diffusivity scaled with the pore radius. The single-pore theory is shown to apply well to ordered materials and successfully interprets recent literature data on the variation of permeability with diffusant molecular size for a DDR zeolite membrane. A peak in permeability is seen at a pore-size-dependent molecular size because of the opposing effects of equilibrium and transport. Application to disordered pore networks is also presented on the basis of a hybrid correlated random walk effective medium theory imbedding the oscillator model at the single-pore level, and a rigorous expression for the tortuosity is derived from the theory. A rich variety of behavior is predicted for the tortuosity, which can increase or decrease with increasing extent of pore size nonuniformity as well as with changes in temperature because the diffusing species preferentially flows through more conducting pores. Weakly adsorbing gases such as helium are seen to have a higher tortuosity than more strongly adsorbing ones. The predicted values of tortuosity are shown to be in line with those obtained from the interpretation of recent experimental mesoporous membrane transport data and are in the range of 5-10 whereas those extracted using the Knudsen model are unrealistically high, in the range of 10-20.

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Section: Resultsmentioning

confidence: 99%

Modeling Pure Gas Permeation in Nanoporous Materials and Membranes

Bhatia

2010

Langmuir

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“…Prior to predicting binary isotherms the fitted parameters for single-component adsorption of ethyl propionate, ethyl butyrate, and ethyl isovalerate were obtained by two different Ž . methods Ismadji and Bhatia, 2001a . The first method used a normalized bimodal gamma function as the pore-size distri-Ž .…”

Section: Prediction Of Binary Isothermsmentioning

confidence: 99%

“…Qualitatively, the interaction forces between the adsorbate molecules and the pore walls become stronger as the critical molecular size of the compound increases. For the three esters used in this study, the critical molecular sizes of the esters follows the order, ethyl isovaler-Ž ate )ethyl butyrate )ethyl propionate Ismadji and Bhatia, . 2001a .…”

Section: Prediction Of Binary Isothermsmentioning

confidence: 99%

Effect of pore‐network connectivity on multicomponent adsorption of large molecules

Ismadji¹,

Bhatia²

2003

AIChE Journal

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“…It is worth mentioning that the percolation theory interpretation of the nitrogen adsorption–desorption isotherms suggests the network connectivity . There are also many other methods which provide other values for the coordination number (see, e.g …”

Section: Resultsmentioning

confidence: 99%

“…[39,40] There are also many other methods which provide other values for the coordination number (see, e.g. [41,42] ). It can be concluded that the coordination number cannot be regarded as a correlating parameter.…”

Section: Effects Of Coordination Numbermentioning

confidence: 99%

Pore network simulation for diffusion through a porous membrane: A comparison between Knudsen and Oscillator models

2013

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Low density permeations of some gases (He, H2, N2, CH4, CO2 and CF4) through micro‐ and mesocarboneous pores were investigated using Knudsen and Oscillator models. Lennard‐Jones model in single layer pores was used to simulate the gas–solid interactions in the Oscillator model. The effects of the pore radius as well as the molecular size and the temperature on the pore diffusivity and the activation energy were studied. The Monte Carlo simulation was then performed to calculate the permeability of these gases in three‐dimensional cubic networks of different connectivities (2.5–6) and different pore size distributions (ra = 2.74 and 6.95 nm). It was shown that for networks with larger pores there is a minor difference between the two models, while a large discrepancy exists in networks with fine pores. Both models tend to have the same permeability as the coordination number decreases. To investigate the accuracy of the models, the simulation results were compared with the experimental selectivities of some pure gases in two different membranes extracted from the literature. It was shown that the Oscillator model can better predict the experimental data in the membranes of smaller pores (i.e. ra = 2.74 nm). However, both models were comparable in membranes of larger pores (ra = 6.95 nm). The capability of the models to predict the activation energy of the diffusion was also studied.

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The Use of Liquid Phase Adsorption Isotherms for Characterization of Activated Carbons

Cited by 10 publications

References 25 publications

Modeling Pure Gas Permeation in Nanoporous Materials and Membranes

Modeling Pure Gas Permeation in Nanoporous Materials and Membranes

Effect of pore‐network connectivity on multicomponent adsorption of large molecules

Pore network simulation for diffusion through a porous membrane: A comparison between Knudsen and Oscillator models

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