Effect of operating parameters on pure and mixed gas permeation properties of a synthesized composite PDMS/PA membrane

Abstract

A composite polydimethylsiloxane (PDMS)/polyamide (PA) membrane was synthesized and sorption, diffusion and permeation of C 3H 8, CH 4 and H 2 were studied both in pure and mixed gas experiments. Pure gas experiments showed that, increasing transmembrane pressure increases solubility, permeability and diffusivity coefficients of heavier gases, C 3H 8, while does not affect or slightly decreases those of lighter ones, CH 4 and H 2. Exactly opposite behavior was observed in mixed gas experiments (with the exception of C 3H 8 and CH 4 solubility) due to the competitive sorption and diffusion in the plasticized polymer matrix. Temperature was realized to induce similar effects on permeation properties of pure and mixed gases. As expected, in rubbery membranes such as PDMS, permeability values of more condensable gases decrease with increasing temperature, whereas those of permanent gases increase. Parameters indicating linear pressure dependence (slopes m, n and q) and Van’t Hoff–Arrhenius type temperature dependence (activation energies E p , Δ H s and E d ) of permeability, solubility and diffusivity coefficients in both pure and mixed gas experiments were estimated and discussed thoroughly. In the case of mixed gas experiments, increasing C 3H 8 concentration in the feed led to increasing solubilities, permeabilities and diffusivities of all the components due to the C 3H 8-induced swelling of the PDMS film. Experimental results demonstrated ability of the synthesized PDMS/PA membrane for separation of organic vapors from permanent gases.