On the determination of diffusivity and sorption coefficients using different time-lag models

• Type: Article in International Scientific Journal
• Date: 2003

Authors

Taveira, P (Author) Other; Adélio Mendes (Author) FEUP; Carlos Costa (Author) FEUP

Journal

Title: Journal of Membrane Science

Vol. 221

Pages: 123-133

ISSN: 0376-7388

Publisher: Elsevier

Indexing

ISI Web of Knowledge - 31 Citations

ISI Web of Science

Scopus - 43 Citations

COMPENDEX

Scientific classification

FOS: Engineering and technology > Other engineering and technologies

CORDIS: Physical sciences > Chemistry > Physical chemistry > Surface chemistry ; Technological sciences > Technology > Biotecnology > Downstream processing

Other information

Authenticus ID: P-000-FJ3

DOI: 10.1016/s0376-7388(03)00252-7

Abstract (EN): Different models have been proposed to fit experimental permeation data in order to obtain membrane transport parameters (sorption capacity and solute diffusivity) when using the time-lag method. Depending on the assumptions, their complexity can vary from a simple linear equation to a more complex non-linear partial differential equation. The applicability, limitations and inaccuracies of these different models are discussed. A numerical procedure to solve the time-lag equation in a membrane slab considering permeate pressure build up is presented. This procedure involves the numerical computation of an inverse Laplace transform using a fast Fourier transform. This is applicable to the full range of the experimental permeation data, provided that both sorption and diffusivity coefficients are constant within the experimental pressure range. Due to its simplicity, the linear time-lag equation is the most commonly used model. However, it does not account for permeate pressure build up. It is shown that this leads to errors in the determination of the permeation parameters which increase with the capacitance parameter (related with the volume available for permeation). For values above a certain threshold (eta > 0.05) these errors are above 5%. Emphasis is put on providing a simple and straight forward way to minimise them.

Language: English

Type (Professor's evaluation): Scientific

No. of pages: 11