(584e) Characterization of Individual Cation and Anion Sorption Related to Salt Transport in Highly Charged Sulfonated Polymers for Desalination Applications

Fundamental studies of salt transport in highly charged sulfonated polymers are necessary in order to optimize the transport properties of these materials for desalination applications. As these materials are non-porous, the solution-diffusion model may be used to describe salt transport. This model states that the permeability of a material to a given penetrant is equal to the product of the penetrant's diffusion coefficient and partition (solubility) coefficient. So, measurement of 2 of these 3 properties allows a full description of transport via the solution-diffusion model. In this work, we combine measured salt partition coefficient data with salt permeability data in order to describe salt transport in terms of permeability, diffusivity, and solubility via the solution-diffusion model.

Highly charged materials, such as sulfonated polymers, contain covalently-bound fixed charge groups. The presence of this fixed charge allows unequal sorption of cations and anions in these materials while still maintaining electroneutrality. Here we have characterized cation and anion sorption in di-sulfonated poly(arylene ether sulfone)s. We have characterized sorption of cations by a polymer ashing technique. This approach allows for direct measurement of cation sorption while avoiding the need to perform an ion-exchange step to measure cation concentration via a desorption experiment. Since anions are not expected to interact electrostatically with the ionomer, sorption of anions can be measured using a desorption technique. The cation and anion sorption results presented here shed light on previously reported differences between transport in acid form and salt form sulfonated polymers. Furthermore, the data presented here are compared to Donnan theory for salt sorption in highly charged materials.