| There is a need for the improved separation of aromatics from saturated hydrocarbons as well as the removal of aromatics, specifically benzene, from waste streams. Membrane separations are a low energy method of separation which can improve distillation efficiency and reduce energy consumption. Facilitated transport membranes containing Ag(I) have shown large selectivities for the separation of aromatics from saturated hydrocarbons. Membranes which have been used to obtain the previous results are, however, either too expensive (Nafion;Transport experiments were performed using Nafion;Sulfonated porous poly(styrene) ion-exchanged with Ag(I) absorbed organics or water relative to the material's hydrophilic/hydrophobic character resulting from the amount of sulfonation present. No selective absorption due to the presence of the Ag(I) complexing agent was observed and selective transport was not anticipated.;Poly(vinyl alcohol) membranes containing AgNO;Membrane characterization, using scanning electron microscope, SEM, showed that phase separation occurred resulting in an inhomogeneous distribution of Ag(I) in the poly(vinyl alcohol)-Ag(I) membranes, making preparation of thin films and quantitative experiments difficult. Several alternative preparations of poly(vinyl alcohol)-Ag(I) membranes cast with Ag(I) showed similar separation properties compared with the base case poly(vinyl alcohol)-Ag(I) membranes, however, the inhomogeneous distribution of Ag(I) still occurred. A homogeneous PVA-Ag(I) membrane was prepared by freeze-drying. Transport results for this membrane were comparable in selectivity and productivity to the base case PVA-Ag(I) membranes. The selectivity of the freeze-dried PVA-Ag(I) membranes was investigated through absorption experiments and extraction rate experiments. Absorption selectivities were unexpectedly low compared to observed transport selectivities. It appears that benzene as well as cyclohexane diffuse through the Ag(I) polymer matrix at a high, competitive rate. |
