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Permeate Flux in Ultrafiltration Processes—Understandings and Misunderstandings

Field, Robert W.; Wu, Jun Jie

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Robert W. Field


Concentration polarization refers to the rapid emergence of concentration gradients at a membrane/solution interface resulting from selective transfer through the membrane. It is distinguishable from fouling in at least two ways: (1) the state of the molecules involved (in solution for concentration polarization, although no longer in solution for fouling); and (2) by the timescale, normally less than a minute for concentration polarization, although generally at least two or more orders of magnitude more for fouling. Thus the phenomenon of flux decline occurring over a timescale of tens of minutes should not be attributed to concentration polarization establishing itself. This distinction and a number of questions surrounding modelling are addressed and clarified. There are two paradigmatic approaches for modelling flux, one uses the overall driving force (in which case allowance for osmotic effects are expressed as additional resistances) and the other uses the net driving force across the separating layer or fouled separating layer, although often the two are unfortunately comingled. In the discussion of flux decline models’ robust approaches for the determination of flux-time relationships, including the integral method of fouling analysis, are discussed and various concepts clarified. The final section emphases that for design purposes, pilot plant data are vital.


Field, R. W., & Wu, J. J. (2022). Permeate Flux in Ultrafiltration Processes—Understandings and Misunderstandings. Membranes, 12(2), Article 187.

Journal Article Type Article
Acceptance Date Jan 29, 2022
Online Publication Date Feb 5, 2022
Publication Date 2022-02
Deposit Date Jul 1, 2022
Publicly Available Date Jul 1, 2022
Journal Membranes
Publisher MDPI
Peer Reviewed Peer Reviewed
Volume 12
Issue 2
Article Number 187


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Copyright Statement
This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

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