Poly(vinyl butyral) (PVB) is selected as a promising ethanol-permselective membrane based on the solubility parameter theory; however, it exhibits anomalous water perm-selectivity in practical pervaporation (PV) process. Comprehensive analysis based on experimental and theoretical methods were carried out to explore the inherent mechanism of the anomalous performance. Firstly, sum frequency generation vibrational spectra and contact angle were developed to quantify the surface reconstruction of membrane in air and ethanol, which indicated that hydrophilic hydroxyl tended to expose on membrane surface with ethanol thus improving the membrane affinity to water. Meanwhile, swelling behaviors proved more water would accumulate in the ethanol swollen membrane. Furthermore, theoretical analysis in terms of sorption and diffusion process, based on the UNIFAC-FV model and Fujita free-volume theory, confirmed the mechanism of anomalous phenomenon of PVB membrane. The comprehensive investigation was expected to provide insights into the basic separation mechanism of PV process.

中文翻译：

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醇溶性聚乙烯醇缩丁醛膜渗透汽化回收乙醇异常现象综合分析

基于溶解度参数理论，聚乙烯醇缩丁醛（PVB）被选为有前景的乙醇选择性渗透膜；然而，它在实际渗透蒸发 (PV) 过程中表现出异常的水渗透选择性。基于实验和理论方法进行综合分析，探索异常性能的内在机制。首先，开发和频产生振动光谱和接触角来量化膜在空气和乙醇中的表面重建，这表明亲水性羟基倾向于暴露在乙醇的膜表面，从而提高膜对水的亲和力。同时，溶胀行为证明乙醇溶胀膜中会积聚更多的水。此外，在吸附和扩散过程方面的理论分析，基于UNIFAC-FV模型和Fujita自由体积理论，证实了PVB膜异常现象的机理。综合调查有望提供对光伏过程基本分离机制的见解。