Fabrication of hydrophilic cation exchange membrane with improved stability for electrodialysis: An excellent anti-scaling performance

A novel preparation method of cation exchange membranes (CEM), based on sulfonated materials with low sulfonation degree (DS), has been proposed in previous studies. For the preparation of CEMs, these studies have provided an approach with low cost, environment-friendly technology, and ideal properties, and proved the value and feasibility of the new method. Based on this, more work remained to be done to further modify the properties of CEMs prepared with this method. One purpose of this study, which was for the basic needs of good CEM practicability, was to improve CEM stability based on sulfonated polyether sulfone (SPES). This purpose was achieved satisfactorily by the proper design, and proved forcefully by stability testing, including thermostability, mechanical stability, and resistance to acid and base, etc. The other purpose, which was designed due to the special membrane surfaces, was to investigate CEM anti-scaling properties during electrodialysis (ED) processes. Compared with commercial CEMs, one clear different characteristic of CEM prepared by this method was flatter and smoother membrane surfaces, which should be an advantage for anti-scaling of salts during an ED process. From this, experiment of the second part was designed to specifically explore anti-scaling factors, but an unexpected result obtained. It was the higher hydrophilicity of these CEMs rather than their smoother surface that played an important role in anti-scaling behavior. The obtained result should be an innovative and significant discovery of this work. It will directly impact on anti-scaling research of both CEM and anion exchange membranes (AEMs). Hence, this work was a meaningful bridge for expanding previous research of CEM preparation into anti-scaling applications of ion exchange membranes.