A New Self-crosslinked Anion Exchange Membrane With Side Chains For Electrodialysis

As an excellent separation and purification techniques, electrodialysis (ED) technology has been widely used in industry and our daily life. Ion exchange membrane (IEM) is a key component in ED equipment. It not only separates the feed solution, but also conducts ions to separate and purify the solution. So the quality of IEM directly determines the ED performance. With the development of industry, ED technology has an increasing requirement for the IEM.Ion exchange membranes for ED equipment should have the following properties: (1) high ion selectivity, (2) high conductivity, (3) proper water uptake. Until now, commercial cation exchange membranes (CEM), like Dupont’s Nafion(?), meet all these requirements and have been widely used as the state-of-the-art IEMs for ED. However, there are no anion exchange membranes can meet all these properties. Electrodialysis equipment should have suitable anion exchange membrane formation. Moreover, the preparation process of anion exchange membranes has two serious problems. On one hand, chlorine ether is used in chlorine methylation process, and it is a highly toxic substance. On another hand, to introduce the quaternary ammonium functional groups on the membrane, we need soak the base membrane in trimethylamine solution. Such process is difficult to control, and the obtained membranes have less stability than the base membranes.In this work, we prepared a novel self-crosslinking anion exchange membrane with side chains. It was developed by the direct reaction of brominated polyphenylene ether (BPPO) and N-4-vinylphenyl-N, N-dimethylamine (VBN). By changing the ratio of BPPO to VBN, a series of self-crosslinking anion exchange membrane with side chains were obtained after a thermal polymerization process. Physicochemical properties of the membranes were tested. In addition, the electrodialysis desalination performance was investigated. The optimal ion exchange capacity of the membrane is 1.8 mmol g"1, the water uptake can be controlled below 25%, the area resistance of the membrane is less than 5 Ω. cm-2, and the transport number is more than 0.97. The desalination result is comparable to the commercial AMX membrane. Such membrane shows good characteristics for application in electrodialysis.