Multiple solute ultrafiltration models in micellar enhanced ultra filtration (MEUF) have been studied, for experimental results of selective separation of Cu (II) and Co (II) with anionic surfactant, sodium dodecyl sulfate (SDS) and imino diacetic acid (IDA) as chelating agent using synthetic waste water. This model is based on mass balance analysis coupled with the filtration theory, resistance-in-series model and gel polarization model. This model is characterized by the parameters, membrane resistance R-m. membrane permeability P-m, back transport coefficient K-b, K-bi and mass transfer coefficient k(i). These parameters are estimated by using the Levenberg-Marquardt method coupled with the Gauss-Newton algorithm. Due to cross currents caused by the superficial velocity, some solutes are removed from the membrane surface and go into the bulk known as back transport effect. Hence back transport coefficient plays significant role in explaining the extent of micellization. The simulation results show a good agreement with the experimental data of permeate quality and flux. The consideration of negligible gel thickness is suitable for dilute solutions. (C) 2010 Elsevier B.V. All rights reserved.