Pervaporation of benzene/cyclohexane mixtures using ion-exchange membrane containing copper ions

The sorption, diffusion, and pervaporation (PV) properties of benzene/cyclohexane (Bz/Cx) mixtures on cation-exchange membranes containing copper ions (Cu(II)) were investigated. The equilibrium sorption isotherms of pure vapors in the membranes and the partial solubility of binary solutions in the membranes were described using the UNIQUAC model. The sigma(iM) and sigma(Mi) values were 0.978 and 0.591 for Bz, and 0.922 and 0.475 for Cx. The transient regimes of vapor sorption were employed to calculate the concentration-dependent diffusion coefficients. Long's model sufficiently explained the diffusivity of Bz and Cx in the membranes. The pre-exponential factors were similar to3 x 10(-13) m(2)/s and the plasticization factors were 3.0 and 3.6 for Bz and Cx, respectively. Excellent agreement was found with the experimental results applying the solubility and diffusivity data to simulate the pervaporation performance (flux and selectivity) using the modified Maxwell-Stefan equation. The membrane containing Cu(II) demonstrates better facilitating capability for Bz transport than that with Na(l), mainly due to its preferential sorption property toward Bz. Replacing Na(l) with Cu(II) into a Neosepta membrane resulted in better separation efficiency and higher Bz flux throughout the entire Bz concentration range. (C) 2004 Elsevier B.V. All rights reserved.