Molecular self-diffusion in active carbons

Kärger, Jörg; Pfeifer, H.; Vartapetian, R. Sh.; Волощук, А. М.

doi:10.1351/pac198961111875

Cited by 23 publications

(9 citation statements)

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“…We previously observed a maximum in the diffusion coefficient for argon diffusing in both BPL activated carbon and a carbon replicate of Faujasite where the diffusive regime was reached. This behavior has also been observed in both simulations of several LJ fluids in saccharose-derived carbons Coasne et al 2006;Nguyen et al 2006;Coasne et al 2007), as well as experimentally for molecular fluids in zeolites (Brandani et al 1995) and water in activated carbon (Kärger et al 1989).…”

Section: Dynamic Behaviorsupporting

confidence: 71%

Adsorption and diffusion of argon in disordered nanoporous carbons

et al. 2010

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Application-specific optimization of disordered nanoporous carbons remains a formidable challenge due to the difficulty in accurately characterizing their microstructures with current empirical methods. Using molecular simulation techniques, we investigated the adsorptive and diffusive behavior of argon in three models of disordered nanoporous carbons. We found that the structural and morphological differences between these models gave rise to distinct phenomenological properties. The adsorptive behavior of argon in both the low and high pressure regimes was enhanced dramatically in the models with more crystalline microstructures. As for dynamic properties, we found that the adsorbent's structure and energetic topology significantly alters the rates of diffusion as well as the characteristics of the underlying diffusion mechanisms.

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Section: Dynamic Behaviorsupporting

confidence: 71%

Adsorption and diffusion of argon in disordered nanoporous carbons

et al. 2010

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“…This means that 35% of water has the translation diffusion coefficient less than 10 −6 cm 2 /s (limit due to instrumental resolution). Such low water self‐diffusion coefficients were obtained by NMR techniques for water molecules confined in the active carbons micropores less 0.5 nm [ Karger et al , 1989]. Taking into account that in our experiment the pore analysis gave us nearly 23% of water localized in the micropores with average size of 0.5 nm at 283 K, we may conclude that nearly 35% of water adsorbed on soot is immobile already at 283 K due to localization mainly in the soot micropores plus some water (≅12%) inside the supermicropores or adsorbed on the external soot surface.…”

Section: Resultsmentioning

confidence: 99%

Water adsorption and dynamics on kerosene soot under atmospheric conditions

et al. 2002

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[1] Morphology, microstructure and surface chemistry of laboratory made kerosene soot used as an aircraft soot surrogate have been studied to establish the correlation between the porosity and the mechanism of water adsorption on the soot surface. The quasielastic neutron scattering (QENS) technique has been used to characterize the dynamics of water confined in the soot pores network. Spectra above and below the water triple point T m describe the translational and rotational diffusion of water molecules adsorbed in 0.5 nm micropores, 2 nm supermicropores and !2 nm mesopores. Below T m an appreciable amount of liquid water exists in the soot micropores down to the lowest tropospheric temperatures. The depression in freezing temperature is related to the pore dimension. Water confined in the micropores appears to freeze completely only at T below 200 K showing that the nucleation process depends on the specific microporosity. At the saturation plume conditions ffi30% of adsorbed water has been transformed into ice. These results show that, in the upper troposphere, soot particles presenting the above-mentioned properties will contain stable water/ice components inside the pores with 25% of unfrozen water.

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“…The self-diffusion studies of water, benzene and methanol differing by their mechanism of adsorption on AC have been represented in a joint work performed by German and Russian scientists-Pfeifer, Karger, Dubinin, Voloshchuk, Vartapetian in the eighties (Vartapetian et al, 1985(Vartapetian et al, , 1989Dubinin et al, 1988;Karger et al, 1989). In these works the average selfdiffusion coefficients of adsorbed molecules at relative high fillings (1 > > 0.2) were measured.…”

Section: Introductionmentioning

confidence: 99%

Adsorption and Mobility of Water and Benzene Molecules in Carbon and Polymer Adsorbents

Khozina¹,

Vartapetyan²

2005

Adsorption

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The correlation between the adsorption and the mobility of adsorbed molecules was analyzed. The peculiarities of molecular mobility in microporous adsorbents with relatively rigid (active carbons) and non-rigid (polymer super-crosslinked and methacrylate sorbents) structure were studied using pulsed nuclear magnetic resonance (NMR) techniques. It was shown that the translational behavior of water and benzene in pores are connected with the specific adsorption mechanism. The NMR data allowed analyzing the changes of molecular state in the processes of adsorption. Diffusional properties of water molecules in the super-crosslinked polystyrenes and active carbons with relatively rigid framework are similar and differ from that in methacrylate polymer sorbents. Moreover, the results of NM relaxation measurements allowed analyzing the porous structure over the scale of pore sizes, while the scale of the self-diffusion measurements comprises the areas of different porosity. The NMR data agree well with the data of adsorption measurements and complement them.

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Molecular self-diffusion in active carbons

Abstract: Abstract

Cited by 23 publications

References 1 publication

Adsorption and diffusion of argon in disordered nanoporous carbons

Adsorption and diffusion of argon in disordered nanoporous carbons

Water adsorption and dynamics on kerosene soot under atmospheric conditions

Adsorption and Mobility of Water and Benzene Molecules in Carbon and Polymer Adsorbents

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