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Membrane Water Treatment Volume 4, Number 2, April 2013 , pages 127-142 DOI: https://doi.org/10.12989/mwt.2013.4.2.127 |
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Dehydration and pore swelling effects on the transfer of PEG through NF membranes |
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Aurelie Escoda, Saliha Bouranene, Patrick Fievet, Sebastien Deon and Anthony Szymczyk
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| Abstract | ||
| In order to investigate the significance of \"salting-out\" and \"pore swelling\" effects on the nanofiltration of neutral solutes, rejection properties of two NF ceramic and polymeric membranes were studied with single polyethyleneglycol (PEG) solution and mixed PEG/inorganic electrolyte solutions. For both membranes, the rejection rate of PEG was found to decrease significantly in the presence of ions. In the case of the ceramic membrane (rigid pores), this phenomenon was imputed to the sole partial dehydration of PEG molecules induced by the surrounding ions. This assumption was confirmed by the lowering of the PEG rejection rates which followed the Hofmeister series. Experimental data were used to compute the resulting decrease in the Stokes radius of PEG molecules in the presence of the various salts. Concerning the polymeric membrane, the decrease in the rejection rate was found to be systematically higher than for the ceramic membrane. The additional decrease was then ascribed to the swelling of the pores. The experimental data of rejection rates were then used to compute the variation in the mean pore radius in the presence of the various salts. The pore swelling phenomenon due to accumulation of counterions inside pores was supported by electrokinetic charge density measurements. | ||
| Key Words | ||
| dehydration; salting-out; hofmeister effects; pore swelling; nanofiltration; ceramic membrane; organic membrane; salts; streaming potential | ||
| Address | ||
| Aurelie Escoda, Patrick Fievet and Sebastien Deon: Institut UTINAM, Universite de Franche-Comte, 25030 Besancon cedex, France; Saliha Bouranene: Universite Mohamed Cherif Messaadia, Souk-Ahras, 41000, Algerie; Anthony Szymczyk: Universite de Rennes, Institut des Sciences Chimiques de Rennes, 35042 France | ||