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Film Model Approximation for Multicomponent Adsorption (2000)

Carta, Giorgio ; Lewus, Rebecca Karst

Springer

Adsorption 6 (2000), S. 5-13

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ISSN: 1572-8757

Keywords: multicomponent adsorption ; diffusion ; Maxwell-Stefan model ; linear driving force approximation ; Langmuir isotherm

Source: Springer Online Journal Archives 1860-2000

Topics: Chemistry and Pharmacology , Physics , Process Engineering, Biotechnology, Nutrition Technology

Notes: Abstract An approximate rate equation based on a film-model representation of diffusional mass transfer is developed to describe the kinetics of multicomponent adsorption. The model describes mass transfer as a pseudo-steady state diffusion process through a flat film of thickness equal to one fifth of the particle radius. Starting with an irreversible thermodynamics description of multicomponent diffusion, the flux relationships are integrated across the film yielding analytical expressions for the rate of mass transfer in a multicomponent adsorption system, when adsorption equilibria are described by the extended Langmuir isotherm. The new approximate rate equation can be conveniently used in the numerical simulation of adsorption systems with concentration-dependent micropore or surface diffusivity, and describes the effects of diffusional flux coupling. Results of accuracy comparable with that obtained when using the classical linear-driving-force approximation for systems with constant diffusivities are obtained with this new rate equation for both batch and fixed-bed adsorption calculations. A generalization of the approach based on the Gibbs adsorption isotherm describes mass transfer rates in terms of the spreading-pressure gradient and provides an extension to other multicomponent isotherm forms.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1023/A:1008927713530

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Fatty acid esterification using nylon-immobilized lipase (1995)

Zaidi, Ahmed ; Gainer, John L. ; Carta, Giorgio

New York, NY [u.a.] : Wiley-Blackwell

Biotechnology and Bioengineering 48 (1995), S. 601-605

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ISSN: 0006-3592

Keywords: lipase ; enzyme immobilization ; esterification ; fatty acid ; n-hexane ; Chemistry ; Biochemistry and Biotechnology

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology

Notes: The esterification of a long-chain fatty acid was conducted using a nylon-immobilized lipase from Candida cylindracea in a nearly anhydrous, nonpolar organic medium, hexane. Butyl laurate was produced from lauric acid and n-butanol at a maximum initial reaction rate of 37 mmol/h. g immobilized enzyme when the substrates were present in equimolar amounts at an initial concentration of 0.5 mol/L. Lower rates were obtained using nonstoichiometric amounts of the substrates. The rate of reaction increased with temperature, reaching a maximum between 35 and 45°C and decreasing sharply at higher temperatures. © 1995 John Wiley & Sons, Inc.

Additional Material: 6 Ill.