The modeling of a gas mixture permeating through a polymeric membrane can be achieved by the combination of a mass transfer model with a thermodynamic model. In this study, three model combinations, i.e., the combination of Fick's law with Henry's law (F‐H), that of Fick's law with the UNIQUAC equation (F‐U), and that of the Maxwell‐Stefan equation with the UNIQUAC equation (MS‐U), were solved by iteration computer procedure to predict the separation performance of both binary and ternary gas mixtures permeating through a polydimethylsiloxane membrane. The predicted results were analyzed in detail and compared with experimental results. It was found that there are remarkable differences among the considered model combinations in predicting separation performance, and these differences tend to become larger with increasing solubility. Among the three considered model combinations, MS‐U gives the prediction closest to the experimental results. Its advantage over the other two model combinations should be due to the proper estimation of the permeate solubility by the UNIQUAC equation and the reasonable consideration of mass transfer resistance by the Maxwell‐Stefan equation.
The recovery or capture of one or more components from gas mixture by membrane separation has become a research focus in recent years. This study investigates the gas-membrane solution equilibrium, for which Henry's law is not applicable if the gas phase is a mixture. This problem can be solved by using UNIQUAC model to calculate the activity coefficient of gas dissolved in the membrane. A method was proposed in this study to obtain the gas-membrane interaction parameter for UNIQUAC model. By the experiments of gas permeation through polydimethylsiloxane PDMS membrane, the solubility coefficients of some gases (N 2 , CO 2 , CH 4) were measured. Through non-linear fitting UNIQUAC model to the experimental results from this study and in literature (H 2 , O 2 , C 3 H 8), the gas-membrane interaction parameters for these gases were obtained. Based on these parameters, the activity coefficients of the dissolved gas were calculated by UNIQUAC model, and their values agree well with the experimental data. These results confirm the feasibility and effectiveness of the proposed method, which makes it possible to better predict gas-membrane solution equilibrium.
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