Very little is known about the transport of aqueous ionic solutions through hydrophobic non-porous nanofiltration membranes. The comparison of well-established aqueous desalination nanofiltration phenomena to silicone-based hydrophobic nanofiltation has not been addressed until now. We investigate the salt permeation and retention in water/methanol mixtures permeating through a silicone-based composite membrane. Its retention behavior is rigorously analyzed and for some aspects compared with a hydrophilic, polyamide-based (Desal DK) membrane. In particular, the retention of NaCI, Lid I and CaCl2 in different MeOH/H2O solutions was investigated. Retentions vary between 10% and 80% depending on the composition from aqueous to methanol solutions. Ion pair formation, i.e. prohibited ion dissociation in the alcoholic solution, correlates with an increase of salt retention. (C) 2014 Elsevier B.V. All rights reserved.