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 con ventional ion exchange for removing metal ions from wastewater. In ESIX, wh ich 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 pre sents the results of experiments on high surface area electrodes and the de velopment of a flow system for cesium ion separation. Bench-scale flow syst em 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 comparis on of results for a stacked five-electrode cell versus a single-electrode c ell showed enhanced breakthrough performance. In the stacked configuration, breakthrough began at approximately 120 BV for a feed containing 0.2 ppm c esium at a flow rate of 13 BV/h. A case study for the KE Basin (a spent nuc lear fuel storage basin) on the Hanford Site demonstrated that KE Basin was tewater could be processed continuously with minimal waste generation, redu ced disposal costs, and lower capital expenditures. (C) 2001 Elsevier Scien ce B.V. All rights reserved.