Modeling Sorption Behavior for Ethanol/Water Mixtures in a Cross-linked Polydimethylsiloxane Membrane Using the Flory-Huggins Equation |
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Authors: | Tzu-Huai Yang Shingjiang Jessie Lue |
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Institution: | Department of Chemical and Materials Engineering , Chang Gung University , Kwei-shan , Taoyuan , Taiwan |
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Abstract: | The sorption behaviors of aqueous ethanol solutions in a polydimethylsiloxane (PDMS) membrane at 25°C were investigated in this study. The sorption isotherms for the ethanol and water binary mixtures were experimentally determined. The water uptake reached a maximum at a concentration of 80 wt% ethanol, and the partial water uptakes were even higher than the pure water solubility for 10–95 wt% ethanol solutions in the PDMS membrane, which implies the presence of a strong synergistic effect due to the ethanol copermeant. The Flory-Huggins equation was utilized to predict the sorption levels at various ethanol/water compositions. The binary Flory-Huggins interaction parameters obtained from pure solvent sorption experiments (χiM ) and the ethanol/water vapor liquid equilibrium data (χ 12) were used in the construction of the model for predicting the partial penetrant solubilities. Using constant χij parameters could not render satisfactory predictions; therefore, concentration-dependent expressions for either χ 12 or χiM were employed to improve the prediction power. We found that constant or concentration dependent χ 12 parameters had little impact on the predicted sorption, whereas the modified concentration-dependent χiM values greatly improved the modeling precision. |
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Keywords: | ethanol/water solutions Flory-Huggins equation polydimethylsiloxane (PDMS) sorption modeling |
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