Retention Mechanisms in Nanofil Tration

摘要

Nanofiltration is a pressure-driven membrane separation process that falls in between reverse osmosis an ultrafiltration in its separation characteristics. In general, even low molecular weight organics and multivalent ions are highly retained, while monovalent ions are retained to a smaller extent. Nanofiltration can be sued as well for the production of drinking water, as for the treatment of process and waste waters. The mechanism ofr separation can be ecplained in terms of charge effects and/or size effects. Experimental evidence is given for several salt solutions and saccharide solutions. Three comercial nanofiltration membranes are sued. The resuts are interpreted qualitaively by the Donnan exclusion mechanism, which takes the charge effects into account. The steric hindrance pore model is used to determine the membrane pore radii. To predict the results for multicomponent mixutures quantitatively the extended nerntst-Planck model could be used.