The Thermal Performance of Hexacyanoferrates

Ion exchange resins are used in the nuclear industry to trap and remove radioactive caesium from power station spent fuel cooling ponds. Natural zeolites such as clinoptilolite, chabazite and mordenite including other organic ion exchanges such as sodium titantates, titanosilicates and hexacyanoferrates have been extensively studied for use in the nuclear industry. This report develops an understanding of the thermal performance of hexacyanoferrates and addresses the concern that cyanide may be produced on heating. TGA/MS analyses were conducted on four different materials: 1. potassium hexacyanoferrate 2. Cs Treat 3. KNiFCPAN 4. Sodium nickelhexacyanoferrate In air, decomposition leads to the generation of CO2, NOx and H20 with little or no HCN observed. In the absence of air, decomposition generates HCN in addition to gases like CO, CO2, NH3 and NOx. The amount of HCN generated depends on the type of hexacyanoferrate, the temperature and whether the carrier gas is dry or wet. It should be noted that hexacyanoferrates are inherently unsafe at high temperatures be it in anaerobic or aerobic conditions. In anaerobic conditions, HCN, NH3 and CO are released and in aerobic conditions noxious gases like NOx are produced. Therefore, no matter what conditions they are stored in, they remain potentially dangerous in case of an accidental release.