Regenerable Electrochemical Spiral Wound Decontamination Cell for Efficient Decontamination of Radionuclides in Water

Water security has become a national priority following the terrorist attacks of September 11, 2001. This project specifically addresses the threat of radionuclide contamination, such as that resulting from a terrorist release of radioactive material into the water supply, but is expected to result in technology that is broadly applicable to other waterborne contaminants. More specifically, this project focuses on cesium-137, a highly water soluble radionuclide that is considered the most likely candidate for use in a radiological dispersal device. We propose a spiral wound electrochemical flow cell for the removal of radionuclides—primarily cesium-137 and secondarily strontium-90—from drinking water. The proposed cell will consist of a flexible electrode sandwich in which one of the electrodes has been plated with nickel hexacyanoferrate (NiHCF), an “electrochemically switchable ion exchange” (ESIX) material. The composite electrode sheet, which also contains a counter electrode and reference electrode for true three-electrode operation, is rolled into a spiral wound cylinder for compactness, throughput, capacity, and ease of manufacture. Contaminated water is fed to one face of the cylinder while holding the potential of the cathode at the designated level to produce clean water at the other end of the rolled electrode. Finally, unlike conventional ion exchange, the ESIX material can be regenerated without using a concentrated regenerant or replacing the ion exchange media; ESIX bed regeneration is achieved through a reversal of the potential on the electrodes. Upon potential reversal, the intercalated cations are eluted into a small volume (e.g., one bed volume) of concentrated waste. The effort builds on our experience with microfluidic NiHCF electrodes, and aims to transition the technology from a microfluidic plate/frame architecture to a large-scale spiral wound form. The objectives are to fabricate and demonstrate an electrochemical filter element, which matches conventional filters’ form factors but produces far less waste and operates far more efficiently than either conventional ion exchange or reverse osmosis.