In this study, polydimethylsiloxane (PDMS)‐coated polyethersulfone (PES) composite membrane was prepared for gas separation. “Film casting” and “dip‐coating” techniques were used for producing selective PDMS layer on the surface of the PES support. The effects of coating technique and conditions including coating solution concentration and curing temperature on permselectivity of CO2, CH4, and N2 were investigated. The prepared PES support did not provide any selectivity to the gases. When the concentration of PDMS coating solution was increased, initially permeability of CO2 was rapidly dropped and then gradually reached to an almost constant value. The optimum concentration of coating solution was 5 wt%. Curing temperature showed no pronounced effect on the CO2 permeability and selectivity. In “film casting” method, double coating showed superior permeability and selectivity. However, triple “dip‐coating” was promising. The selectivity of composite membrane prepared by “dip‐coating” was higher than “film casting” method. CO2/N2 and CO2/CH4 selectivity of five sequential dip‐coated composite membranes was 45.5 and 9.3, respectively. POLYM. ENG. SCI., 2013. © 2013 Society of Plastics Engineers

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a b s t r a c tThe influence of naturally occurring monovalent NaCl and divalent Na 2 SO 4 salts with anions at near extremes of Hafmester series on liquid-liquid equilibrium (LLE) of the chemical system of {water + acetone + 1-Hexyl-3-methylimidazolium hexafluorophosphate (HMIMPF 6 ) ionic liquid} was studied. The conditions were 298.2 K, atmospheric pressure of 81.5 kPa and salts mass fractions in initial aqueous solutions of 0.05 and 0.10. Results show that salting-out effect was significant, so that enhancements in the acetone distribution coefficient was achieved within (21.67-35.54)% for NaCl and (51.84-92.37)% for Na 2 SO 4 . The stronger anion activity and the lack of anion exchange with the used ionic liquid can be the reasons for the stronger effect of the latter salt. The consistency of the experimental data were examined with the improved Eisen-Joffe equation. For modeling purpose, the NRTL and UNIQUAC equations were satisfactorily applied to correlate the phase equilibria. In the presence of NaCl and Na 2 SO 4 salts, the root mean square deviations of compositions, for NRTL equation were 0.0346 and 0.0634 and for UNIQUAC equation 0.1093 and 0.0328, respectively.