渗透汽化膜结构改性及其膜内渗透分子的溶解和扩散行为研究

It is very difficult to solve the trade-off phenomenon between permeance and selectivity in pervaporation membrane. Poly(vinyl alcohol) (PVA) as basic material, perfluorosulfonic acid (PFSA) and silicone hydride compounds as modified materials, PVA/PFSA/Si organic-inorganic hybrid membrane with both high permeance and selectivity will be prepared by sol-gel method, and the trade-off effect in pervaporation is ameliorated. The structure can be controlled and adjusted by changing the preparation conditions, and the relationship between preparation conditions of membrane and its microscopic structure is studied. The coupling way between organic and inorganic components, and the effects of inorganic components on the structure of hybrid membrane are studied by the characterizations of structure and the molecular simulation, thus the formation mechanism of hybrid membrane is determined. Effects of preparation and operation conditions on the pervaporation performance for ester aqueous solutions and multicomponent solutions are investigated, and the relationships between materials, microscopic structure and separation performance of hybrid membrane are discussed. Combined with the structure of hybrid membrane, swelling and sorption experiments and measurements of diffusion coefficients, the solution and diffusion behaviors of binary and multicomponent solutions in hybrid membrane are studied through the modified Flory-Huggins theory and the modified free volume theory, respectively. Based on the solution and diffusion behaviors, the pervaporation separation mechanism of hybrid membrane is revealed, and the modified solution-diffusion model is determined.

渗透汽化膜存在渗透性与分离选择性之间trade-off效应难以解决的瓶颈问题。本项目以聚乙烯醇(PVA)为基本材料，全氟磺酸(PFSA)和硅烷类化合物为改性材料，拟采用溶胶-凝胶法制备兼具高渗透性和高分离选择性的PVA/PFSA/Si有机-无机杂化膜，改善膜的trade-off效应。调整制膜条件，实现成膜过程中微观结构控制，并研究制膜条件与微观结构之间的关系。结合膜结构及分子模拟，考察膜内有机、无机组分结合方式及无机组分对膜结构性能的影响，明确成膜机理。考察制膜条件及操作条件对杂化膜分离酯类及多组分水溶液性能的影响，并探讨膜材料-微观结构-分离性能之间的关系。结合杂化膜结构、溶胀吸附实验及扩散系数测定，分别利用修正Flory-Huggins理论和修正自由体积理论，研究二元及多元组分在杂化膜内的溶解和扩散行为，揭示杂化膜渗透汽化分离机理，并建立相应的溶胀、扩散模型以及改进的溶解-扩散模型。

目前渗透汽化脱水膜的研究较多，但普遍存在渗透通量低、稳定性不高以及分离过程中存在渗透性和分离选择性之间不能同时满足的trade-off 效应等问题。本项目针对渗透汽化膜分离过程中的trade-off效应，以聚乙烯醇(PVA)为基本材料，全氟磺酸(PFSA)为共混改性材料，正硅酸乙酯(TEOS)为无机杂化材料，采用共混法和溶胶-凝胶法对PVA进行双重改性，制备了PVA-TEOS-PFSA有机-无机杂化膜。并通过FTIR、XRD、SEM、接触角、正电子湮灭寿命谱(PALS)等对杂化膜进行了多种表征手段，充分了解其物理化学性能及微观结构。以聚丙烯腈(PAN)超滤膜为底膜，采用涂覆法制备了PVA-TEOS-PFSA/PAN复合膜，应用于乙酸乙酯体系脱水。实验结果表明，复合膜具有较高的渗透通量和分离选择性。同时优选复合膜用于分离乙酸/水(HAc/H2O)、乙酸乙酯/乙醇/水(EAc/EtOH/H2O)、乙酸乙酯/乙酸/乙醇/水(EAc/HAc/EtOH/H2O)等溶液渗透汽化脱水，同样取得较好的分离效果。.为了改善单一无机改性组分容易造成交联不均匀或无机粒子团聚等问题，采用纳米二氧化硅、γ-氨丙基三乙氧基硅氧烷(APTEOS)或γ-缩水甘油醚氧丙基三甲氧基硅烷(GPTMS)等双重无机组分，通过溶胶-凝胶法和共混杂化法改性PVA-PFSA材料，制备了PVA/PFSA/Si有机无机杂化膜(为区别于TEOS改性方法，文中以此为简写)。并采用多种分析手段对杂化膜进行了表征，以了解制备方法、膜组成对杂化膜物理化学性能和微观结构的影响。同样以PAN膜为基膜，采用涂覆法制备了相应的复合膜。考察了杂化膜组成、操作条件等对酯、酸、醇等溶液的分离性能，结果表明两种无机组分改性的PVA/PFSA/Si杂化膜具有良好的渗透汽化分离效果。.研究杂化膜在EAc/H2O、EAc/EtOH/H2O、EAc/HAc/EtOH/H2O溶液中的吸附行为，考察了杂化膜在不同组成溶液中的溶胀度以及对渗透组分的吸附选择性，同时测定并对比了杂化膜在不同溶液中的动态吸附曲线。实验结果表明，在EAc/H2O、EAc/EtOH/H2O、EAc/HAc/EtOH/H2O溶液中，渗透分子在杂化膜中的扩散符合费克扩散。利用全反射傅里叶变换红外光谱仪(ATR-FTIR)研究了渗透分子在PVA/PFSA/Si杂化膜中的扩散行为。