Mixed Matrix Membranes with Ionic Liquid-Grafted Layered Double Hydroxides: Characterizations and CO<sub>2</sub> Separation Properties
Wei Zheng, Haiyan Jiang, Chaoran Wang, Shaojuan Zeng, Xiaochun Zhang, Xiaochun Zhang, Haifeng Dong, Lu Bai, Xiangping Zhang, Xiangping Zhang
Abstract
Carbon dioxide (CO 2 ) separation plays a vital role in environmental protection and resource reuse. A potential approach to achieving satisfactory CO 2 separation is combining the benefits of ionic liquids (ILs) and membranes. In this work, the IL-LDH nanosheets were obtained by functionalized IL modifying layered double hydroxides (LDH) and used to construct the Pebax/IL-LDH mixed matrix membranes (MMMs). The X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and X-ray photoelectron spectroscopy (XPS) spectra analysis displayed that the IL was successfully grafted to the LDH nanosheets. The characterizations of MMMs showed that the introduction of IL-LDH reduces the crystallinity of the Pebax membrane, and there are hydrogen bond interactions between fillers and Pebax. The IL modification strengthens the membranes with better CO 2 affinity and improves the interfacial compatibility between Pebax and LDH. Meanwhile, the CO 2 -philic nanochannels formed by the slits of IL-LDH nanosheets facilitate CO 2 transport in MMMs. Such inherent properties of the IL and LDH conjunctly contribute to the improvement of the CO 2 separation performance of membranes. The optimum Pebax/IL(20)-LDH MMM has a high CO 2 permeability of ∼388 barrer at 30 °C, which is approximately 2.9 times that of pure Pebax, and the CO 2 /CH 4 selectivity does not change significantly. Besides, the Pebax/IL(20)-LDH MMM exhibited a notable increase in CO 2 permeability as the working temperature increased, ultimately attaining ∼576 barrer at 50 °C.