Hello,

concentration polarization is a mass transfer related phenomenon that may cause fouling and/or scaling.

Imagine a tangential feed stream passing over a membrane. Subsequently a hydrodynamic boundary layer is formed, that poses a mass transfer resistance. Now mass transfer into the boundary layer occurs via advection. Mass transfer out of it occurs by diffusion back into the bult and advection with the permeate flux out of it. if the solutes are retained by the membrane under consideration, this mass transfer scenario will cause the retained solutes to be concentrated at the membrane surface since transport into the boundary layer (advective) is normally higher than diffusion back into the feed bulk. In case of electrolyte solutions this may cause supersaturation that can lead to crystalization of salts on the membrane (scaling/fouling).

Two helpful references might be:

Sablani, S. S. et al.:Concentration polarization in ultrafiltration and reverse osmosis: a critical review. Desalination 141(2001), pp. 269-289.

Kim & Hoek: Modeling concentration polarization in reverse osmosis process. Desalination 186 (2005), pp. 111-128.

The latter concentrates on modeling but gives a good understanding of the mass transfer phenomena occuring. You can certainly find a lot more references via scopus. There are also a lot of good text books on the subject. Regarding concentration polarization you will find information in any of them, because it is a common phenomenon in membrane filtration processes.

If you need any more information, feel free to contact me.

Best regards

Thank u Andre Rieger sir.....now i got perfect direction, .....

flux reduction that is reversible is. as a rule, due to concentration polarization, whereas an irreversible flux reduction is due to fouling.