(372k) Impact of Wafer Chemistry on Electrodeionization Removal and Selectivity

Electrodeionization (EDI) removes ions using electricity as the driving force. As ions get transported from the dilute to concentrate chambers, the concentration in the dilute decreases, which increases the internal resistance for ion removal, resulting in a process limitation. To overcome that issue, a mixture so-called wafer is used in the dilute chambers. Wafers include ion exchange beads whose function is to interact with the ions in the solution, guided by the functional groups on the beads’ surface. It is known that although the commercial ion exchange beads are good exchangers, their selectivity needs to be enhanced to meet the requirements of specific ion removal processes.

Previous studies have shown that material modification with various crown ether molecules has resulted in increased ionic selectivity of different ionic species based on the size of the crown molecules present in the system. For instance, 15-crown-5 ethers have been shown to complex with sodium. For this study, a multi-ion solution was run on a 1-wafer EDI using wafers produced with different cation and anion exchange beads to better understand the impact of different wafer chemistries on the ion removal process. Included in the cation exchange beads were those that had been modified with crown ethers.

The different combinations of beads had a high impact on ion removal, and the modifications of cation exchange beads resulted in an increase in the wafers’ selectivity by at least 10%.