Salt splitting using ceramic membranes

Inorganic ceramic membranes for salt splitting of radioactively contaminated sodium salt solutions are being developed for treating U.S. Department of Energy tank wastes. The process consists of electrochemical separation of sodium ions from the salt solution using sodium(Na) Super Ion Conductors (NaSICON) membranes. In contrast to conventional organic-based bipolar or ion exchange membranes used in salt splitting, NaSICON membranes are resistant to gamma/beta radiation and are highly selective for sodium ions. Potential applications include 1) caustic recycle for sludge leaching, regeneration of ion exchange resins, inhibition of corrosion in carbon steel tanks, or retrieval of tank wastes; 2) pH adjustment and reduction of competing cations to enhance cesium ion exchange processes; 3) sodium reduction in high-level waste sludges; and 4) sodium removal from acidic wastes to facilitate calcining. Initial experiments with dysprosium-based NaSICON membranes have demonstrated the feasibility of the process.