Ion exchange membranes (IEMs) are widely used in water purification applications, such as reverse osmosis and electrodialysis and are also applied for energy generation applications, such as fuel cells or reverse electrodialysis. IEMs are composed of charged polymers that contain charged moieties bound to the polymer backbone. The presence of these charged groups has significant impact on ion and water transport through these materials and allows for selective permeation of ionic species, making them attractive for the separations required for water and energy applications. However, a major limitation of commercial IEMs is that they are made from brittle cross-linked polyelectrolytes, supported in thick (e.g., 100-600 µm) impermeable membrane support structures to have sufficient mechanical strength in operation. These meshes are hydrophobic and cannot transport ions or water, thereby significantly reducing overall membrane performance. Recently, in the biomedical literature so-called double network hydrogels have been synthesized and exhibit exceptional strength and toughness, making them attractive for use as cartilage replacement. However, they have not yet been explored as IEMs. We have applied these concepts to IEM synthesis and have constructed prototype super-tough IEMs. We have started to characterize their basic membrane and transport properties and have results for water uptake, charge content, salt permeability, and water permeability for several prototypes. Our findings show that the prototype materials exhibit nearly no selectivity for water over salt or vice versa due to the remarkably high water content of these materials. We are currently testing new synthetic conditions to reduce the water content, while maintaining a double network structure, and some preliminary results are available. The key goal of this study is to develop robust IEMs, that do not require membrane support structures and exhibit both highly selective and rapid transport.<br/>

Developing super-tough ion exchange membranes for water and energy applications

2019 Fall National Meeting

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