This paper reports the flux, retention and stability of nanofiltration (NF)
membranes with aqueous and organic solvents, and three selected solutes ha
ving the same molecular weight of 350 Da: Orange II, Safranine O and Solven
t Blue 35. It appears that the nominal manufacturer-specified molecular wei
ght cut-off is only valid for predicting the rejection in aqueous solutions
, and that the retention in organic solvents either for molecules of the sa
me molecular weight or even for the same molecule is unpredictable and depe
nds on the specific solvent. It was found that solute retention in organic
solvents is lower than in aqueous solution, and that the solvent has signif
icant influence on the retention. These interesting results were not due to
membrane deterioration in the presence of organic solvents for any of the
membranes studied in this work. (C) 2001 Elsevier Science B.V. All rights r
eserved.