支撑层对硅橡胶复合膜渗透汽化分离性能的影响

引言 为了扩大渗透汽化技术的应用领域,科研工作者需要进一步增强渗透汽化膜的分离性能.从工业化的观点而言,用于实际应用的渗透汽化膜大多是复合膜,它由选择层(或分离层)和支撑层组成.一般认为,选择层决定着复合膜的选择性和通量,支撑层起支撑和机械稳定作用.Nijhuis1]在从甲苯-水体系中分离甲苯的过程中对均质膜和以聚砜为支撑层的复合膜的分离性能进行了比较;Sturken2]分别用聚醚酰亚胺和聚偏氟乙烯为支撑层的硅橡胶膜从二氯乙烷-水体系中提取二氯乙烷,他们得到了相同的结论:支撑层的影响可以忽略.然而Scholz3],Heinzelmann4],Rautenbach5],Borges6],Vankelecom7],Farooq8],Lipnizki9]等均在各自研究中发现,由于基膜和分离层的物理化学性质以及制膜方法等众多因素的存在使得支撑层在一定程度上影响复合膜的分离性能;Feng10]对均质硅橡胶膜和有微孔支撑层的硅橡胶复合膜的分离性能进行了比较,发现均质硅橡胶膜优先透过异丙醇,而有微孔亲水性支撑层的硅橡胶复合膜则优先透过水,这表明在一定的情况下,支撑层甚至起主导作用并能够决定复合膜的分离性能.因此,通过系统研究以不同多孔材料为支撑层的复合膜对有机物-水溶液的分离性能的影响,能够找到最优的复合膜支撑层,从而能够提高复合膜的分离性能.然而,至今关于支撑层对渗透汽化膜分离性能影响的系统研究仍相当少.

Influence of support layer of composite PDMS membranes on performance of hydrophobic pervaporation

Three types of composite PDMS membranes were prepared by using PAN, CA, and PVDF as support materials and used to separate ethanol from aqueous solution by pervaporation. The experimental results evidently demonstrated that the support layer had a significant impact on the flux and selectivity of composite PDMS membranes. The effect of the average pore size of supports on the performance of composite PDMS membranes was complex, and depended on many factors such as the physico-chemical properties of skin layers or supports and the preparation methods of composite membranes. The total flux of ethanol-water mixture through each composite PDMS membrane increased with increasing temperature. In contrast, the relation between selectivity and temperature was different due to increasing feed concentration, the flux through each composite PDMS membrane various supports. With increased quickly while the selectivity decreased. All these observation would be helpful to provide a guideline for the selection of an optimum support layer.