Model for surface diffusion in liquid‐phase adsorption

Miyabe, Kanji; Takeuchi, Shigeya

doi:10.1002/aic.690431112

Cited by 28 publications

(20 citation statements)

References 29 publications

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“…Previously, ,− we analyzed the correlation between D s and the parameters of the retention process, i.e., K and Q st , and developed the restricted diffusion model as an approximation of the mechanism of surface diffusion. Surface diffusion was regarded as molecular diffusion restricted by the adsorptive interactions between the adsorbate molecules and the surface of the adsorbent.…”

Section: Resultsmentioning

confidence: 99%

Thermodynamic Characteristics of Surface Diffusion in Reversed-Phase Liquid Chromatography

and

Guiochon

1999

J. Phys. Chem. B

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The thermodynamic properties of surface diffusion in reversed-phase liquid chromatography (RPLC) were analyzed in connection with the thermodynamics of surface diffusion in gas chromatography systems and of phase equilibrium in RPLC. The results suggest that the activation energy of surface diffusion in RPLC consists of only two contributions, corresponding to a hole-making and a bond-breaking process. The former is close to the activation energy of the mobile phase viscosity; the latter is correlated with the isosteric heat of adsorption (Q st ), by a numerical coefficient between 0.5 and 0.6. The validity of these results was proved by the analysis of correlations between the surface diffusion coefficient (D s ) and the adsorption equilibrium constant (linear free energy relation), between D s and the boiling point of the sample components, and between the ratio of D s to the molecular diffusivity and Q st . These results support a restricted diffusion model, proposed earlier as an approximation of the mass transfer mechanism of surface diffusion. The restricted diffusion model provides consistent interpretations for the intrinsic thermodynamic properties of surface diffusion in RPLC.

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Section: Resultsmentioning

confidence: 99%

Thermodynamic Characteristics of Surface Diffusion in Reversed-Phase Liquid Chromatography

and

Guiochon

1999

J. Phys. Chem. B

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“…However, it allows the increasing trend in diffusivities with increasing concentrations to be explained. Recently, Miyabe and Takeuchi have discussed the dependence of surface diffusivities or temperature and concentration, as a function of isotherm type . For a Langmuir-type isotherm, the concentration dependence of surface diffusivity is interpreted in terms of change (d ln C e /d ln q ), independently of the adsorption potential, while for a Freundlich-type isotherm, surface diffusivities vary with the isosteric heat of adsorption, but independently of the change in the logarithmic slope of the adsorption isotherms (d ln C e /d ln q ).…”

Section: Resultsmentioning

confidence: 99%

Chitosan Sorbents for Platinum Sorption from Dilute Solutions

Guibal

Larkin

Vincent

et al. 1999

Ind. Eng. Chem. Res.

133

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Chitosan has proved efficient at removing platinum in dilute effluents. The maximum uptake capacity reaches 300 mg g-1 (almost 1.5 mmol g-1). The optimum pH for sorption is pH 2. A glutaraldehyde cross-linking pretreatment is necessary to stabilize the biopolymer in acidic solutions. Sorption isotherms have been studied as a function of pH, sorbent particle size, and the cross-linking ratio. Surprisingly, the extent of the cross-linking (determined by the concentration of the cross-linking agent in the treatment bath) has no significant influence on uptake capacity. Competitor anions such as chloride or nitrate induce a large decrease in the sorption efficiency. Sorption kinetics show also that uptake rate is not significantly changed by increasing either the cross-linking ratio or the particle size of the sorbent. Mass transfer rates are significantly affected by the initial platinum concentration and by the conditioning of the biopolymer. Gel-bead conditioning appears to reduce the sorption rate. While for molybdate and vanadate ions, mass transfer was governed by intraparticle mass transfer, for platinum, both external and intraparticle diffusion control the uptake rate. In contrast with the former ions, platinum does not form polynuclear hydrolyzed species, which are responsible for steric hindrance of diffusion into the polymer network.

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“…A consistent interpretation was provided for both temperature and concentration dependence of D s in various liquid-phase adsorption systems, such as the Langmuir, Freundlich, and Jossens type adsorption. Irrespective of the type of adsorption systems, the dependence of D s on q could be interpreted by taking into account the variation of both the logarithmic slope of an adsorption isotherm, d ln c/d ln q, and adsorption potential, E ap (Miyabe and Takeuchi, 1997b). It was also demonstrated that the various correlations between E s and Q st could be quantitatively explained by the model (Miyabe and Takeuchi, 1997a).…”

Section: Introductionmentioning

confidence: 99%

Surface Diffusion of Alkylbenzenes on Octadecylsilyl−Silica Gel

Miyabe

Takeuchi

1998

Ind. Eng. Chem. Res.

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Surface diffusion phenomena of alkylbenzenes in reversed-phase liquid chromatography (RP-LC) using an octadecylsilyl-silica gel and methanol/water (70/30, v/v) were analyzed on the basis of a restricted molecular diffusion model, in which surface diffusion coefficient, D s , was correlated with molecular diffusivity, D m , by introducing a restriction energy, E r . The average ratio of E r to isosteric heat of adsorption Q st , γ, in RP-LC was about 0.3. It was also indicated that γ at different temperatures could be represented as a linear function of the reciprocal of -Q st when a linear free-energy relation held and an enthalpy-entropy compensation for adsorption equilibrium was established. An estimation procedure of D s was proposed on the basis of the results. It was demonstrated that D s at a given temperature could be calculated with an error of less than about 10% from only one datum of the adsorption equilibrium constant.

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Model for surface diffusion in liquid‐phase adsorption

Cited by 28 publications

References 29 publications

Thermodynamic Characteristics of Surface Diffusion in Reversed-Phase Liquid Chromatography

Thermodynamic Characteristics of Surface Diffusion in Reversed-Phase Liquid Chromatography

Chitosan Sorbents for Platinum Sorption from Dilute Solutions

Surface Diffusion of Alkylbenzenes on Octadecylsilyl−Silica Gel

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