The process of desalination of aqueous dye-salt solutions by polymeric nanofiltration membranes using commercially available modules was studied.The influence of dye and salt concentration on the salt rejection and flux as well as comparison of individual NF membranes for desalting purpose is presented. Extended Spiegler-Kedem model including Donnan exclusion mechanism and the term of concentration dependence of salt permeability was used for prediction of salt rejection. The experimental results show negative salt rejections during the desalination and the dependence of this phenomenon on premeate.It was also shown that the extended Spiegler-Kedem model including Donnan exclusion mechanism can satisfactorily predict salt rejections even at high concentration typical of desalting process. From among the membranes used in this work membrane PES 10 has been chosen as the most suitable for desalination of the given type of dye.
