膜科学与技术

醋酸纤维素/MOF混合基质膜的水/盐传输

作者：尤蒙，孙玉绣，许飞，高鑫，孟建强

单位： 1. 天津工业大学分离膜与膜过程国家重点实验室，天津 300387； 2. 天津工业大学材料科学与工程学院，天津 300387； 3. 天津工业大学化学与化工学院, 天津 300387

关键词：混合基质膜；溶解-扩散理论；传输性能；选择性；反渗透

出版年,卷(期):页码： 2021,41(3):77-88

摘要：

金属有机框架（MOFs）是一种近几年发展起来的一种具有规整孔结构的无机纳米粒子，在膜分离方面表现出很大应用前景。其中，MOF在水处理方面应用最成功的例子就是聚酰胺薄层复合纳米膜（TFN）的制备。在聚酰胺层中加入MOF无机粒子，可以实现通量和截留的协同优化。但是由于聚酰胺层各向异性，不均一，很薄（< 500 nm），难于表征其传质性质，因此MOF改善反渗透膜性能的机理尚不清楚。我们以溶解-扩散理论为基础，选择可以制成均质膜的三醋酸纤维素（CTA）为原膜，研究加入MOF粒子（UiO-66, MIL-101 和ZIF-8）对其水/盐传输的影响。研究发现，MOF的加入能够提高混合基质膜的密度和玻璃化转变温度（Tg），这主要是因为MOF和CTA链之间的物理相互作用使聚合物链吸附在MOF表面，导致聚合物链运动受到限制。同时，MOF破坏CTA链的堆积，降低了其结晶度。与原膜相比，添加MOF粒子对膜的水和盐吸收影响比较小，但明显降低了其对于盐的扩散和渗透，这主要归因于膜致密化和MOF与水合盐离子之间的相互作用。因此，MOF的加入在一定程度上可以提高膜的水/盐选择性。总之，MOF粒子的加入主要是通过明显降低盐离子的扩散而提高了CTA的水/盐选择性。

Metal organic frameworks (MOFs) is one of the inorganic nanoparticles with regular pore structure and has recently drawn tremendous attention for the water treatment applications. One of the most successful applications is the fabrication of polyamide thin-film nanocomposite (TFN) membrane, which illustrated advantageous combination of water flux and salt rejection. However, the mechanisms of the improved desalination for TFN membrane are still unknown due to the anisotropy, uneven and very thin polyamide layer. We selected cellulose triacetate (CTA) as the base membrane and MOFs (UiO-66, MIL-101 and ZIF-8) as inorganic fillers to prepare the mixed matrix membranes for studying the effect of MOF on the water/salt transport properties based on the solution-diffusion theory. The addition of MOF increased the Tg and membrane density, which was due to the physical interaction between CTA chains and the MOF decreasing the flexibility of CTA chains. The MOFs destroyed the CTA chain packing and decreased its crystallinity. Compared to the CTA membrane, the adding of MOF showed small effect on the water and salt sorption, but greatly decreased the salt diffusivity and permeability, which was due to the membrane densification and interaction of salt ions with MOFs. As a result, the selectivity of the MOF/CTA increased. In all, the adding of MOF significantly increased the water/salt permeation selectivity by suppressing salt diffusion.

尤蒙1990-），女，河北石家庄，博士生，从事反渗透膜以及聚合物膜传质机理研究，

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