Abstract
The permeability of various organic solvents through a composite dense nonporous membrane comprising a silicon polymer as the active layer was studied to elucidate the transport mechanism under steady-state conditions. The permeability was calculated from the difference in the parameters of the solvent and the membrane polymer, |δ1 – δ2|, and the molecular weight (size) of the solvent, M2; |δ1 – δ2| and M2 would correspond to the solubility and diffusivity, respectively. Generally, the permeability of the different groups of common solvents classified on the bases of their molecular sizes tended to increase with a decrease in |δ1 – δ2|. However, the M2 values of the alkane solvents were inversely proportional to their permeabilities. For a more detailed analysis of the transport mechanism, the regular solution model was used. The permeate flux of the solvent, ln (J2), showed a linear dependence on the mole fraction of the solvent in the membrane phase, ln (X2), and the square of the volume fraction of the solvent in the membrane polymer phase (degree of swelling), Φ22. In the case of the common solvents, ln (J2) showed a linear dependence on the product of the molar volume of the solvent (V2) and the square of the solubility parameter difference (δ1 – δ2)2 at constant pressure and temperature. In the case of the alkane solvents, a good correlation was observed between ln (J2) and V2, as the (δ1 – δ2)2 values were numerically around unity. These results agreed with the conclusions drawn from studies performed using the solution-diffusion model. Thus, this new approach is expected to help in the accurate elucidates of the mechanism of transport of a non aqueous liquid through a composite dense nonporous membrane.
