Cesium separation using electrically switched ion exchange

Electrically switched ion exchange (ESIX) is a separation technology being developed at Pacific Northwest National Laboratory as an alternative to conventional ion exchange for removing metal ions from wastewater. In ESIX, which combines ion exchange and electrochemistry, ion uptake and elution can be controlled directly by modulating the potential of an ion exchange film that has been electrochemically deposited onto an electrode. This paper presents the results of experiments on high surface area electrodes and the development of a flow system for cesium ion separation. Bench-scale flow system studies showed no change in capacity or performance of the ESIX films at a flow rate up to 113 bed volumes/h (BV/h), the maximum flow rate tested, and breakthrough curves supported once-through waste processing. A comparison of results for a stacked five-electrode cell versus a single-electrode cell showed enhanced breakthrough performance. In the stacked configuration, breakthrough began at approximately 120 BV for a feed containing 0.2 ppm cesium at a flow rate of 13 BV/h. A case study for the KE Basin (a spent nuclear fuel storage basin) on the Hanford Site demonstrated that KE Basin wastewater could be processed continuously with minimal waste generation, reduced disposal costs, and lower capital expenditures. (C) 2001 Elsevier Science B.V. All rights reserved.