McNair Robert, Cseri Levente, Szekely Gyorgy, Dryfe Robert
Department of Chemical Engineering & Analytical Science, University of Manchester, The Mill, Sackville Street, Manchester, M1 3BB, U.K.
Department of Chemistry, University of Manchester, Oxford Road, Manchester, M13 9PL, U.K.
ACS Appl Polym Mater. 2020 Jul 10;2(7):2946-2956. doi: 10.1021/acsapm.0c00432. Epub 2020 Jun 1.
Membrane capacitive deionization (MCDI) for water desalination is an innovative technique that could help to solve the global water scarcity problem. However, the development of the MCDI field is hindered by the limited choice of ion-exchange membranes. Desalination by MCDI removes the salt (solute) from the water (solvent); this can drastically reduce energy consumption compared to traditional desalination practices such as distillation. Herein, we outline the fabrication and characterization of quaternized anion-exchange membranes (AEMs) based on polymer blends of polyethylenimine (PEI) and polybenzimidazole (PBI) that provides an efficient membrane for MCDI. Flat sheet polymer membranes were prepared by solution casting, heat treatment, and phase inversion, followed by modification to impart anion-exchange character. Scanning electron microscopy (SEM), atomic force microscopy (AFM), nuclear magnetic resonance (NMR), and Fourier-transform infrared (FTIR) spectroscopy were used to characterize the morphology and chemical composition of the membranes. The as-prepared membranes displayed high ion-exchange capacity (IEC), hydrophilicity, permselectivity and low area resistance. Due to the addition of PEI, the high density of quaternary ammonium groups increased the IEC and permselectivity of the membranes, while reducing the area resistance relative to pristine PBI AEMs. Our PEI/PBI membranes were successfully employed in asymmetric MCDI for brackish water desalination and exhibited an increase in both salt adsorption capacity (>3×) and charge efficiency (>2×) relative to membrane-free CDI. The use of quaternized polymer blend membranes could help to achieve greater realization of industrial scale MCDI.
用于水脱盐的膜电容去离子化（MCDI）是一项创新技术，有助于解决全球水资源短缺问题。然而，离子交换膜的选择有限阻碍了MCDI领域的发展。MCDI脱盐是从水中（溶剂）去除盐分（溶质）；与蒸馏等传统脱盐方法相比，这可大幅降低能源消耗。在此，我们概述了基于聚乙烯亚胺（PEI）和聚苯并咪唑（PBI）的聚合物共混物制备的季铵化阴离子交换膜（AEM）的制备与表征，该共混物为MCDI提供了一种高效的膜。通过溶液浇铸、热处理和相转化制备平板聚合物膜，随后进行改性以赋予其阴离子交换特性。使用扫描电子显微镜（SEM）、原子力显微镜（AFM）、核磁共振（NMR）和傅里叶变换红外（FTIR）光谱对膜的形态和化学成分进行表征。所制备的膜表现出高离子交换容量（IEC）、亲水性、选择透过性和低面积电阻。由于添加了PEI，季铵基团的高密度增加了膜的IEC和选择透过性，同时相对于原始PBI AEM降低了面积电阻。我们的PEI/PBI膜成功应用于非对称MCDI用于微咸水脱盐，相对于无膜CDI，其盐吸附容量（>3倍）和电荷效率（>2倍）均有所提高。使用季铵化聚合物共混膜有助于实现MCDI更大规模的工业化应用。
