Surfactant-based separation of toxic eosin dye is studied to estimate the potential of micellar enhanced ultrafiltration (MEUF) using cetyl(hexadecyl) pyridinium chloride (CPC) as the cationic surfactant. The optimum feed CPC concentration is found from the experimental results of pure CPC solution in a batch cell. It is in the range of 10-20 kg/m(3) to have a reasonable permeate flux and lower surfactant concentration in the permeate. Selecting 10 kg/m(3) as the feed surfactant concentration, MEUF experiments are conducted to study the retention characteristics of eosin dye in the continuous cross flow system. The effects of operating conditions, i.e., feed dye concentration, operating pressure and cross flow rate on the permeate flux and observed retention of dye are investigated. (c) 2006 Elsevier B.V. All rights reserved.