Thermal Studies of K2 NiFCN Loaded with some Ions from Radioactive Liquid Waste

Potassium nickel ferrocyanide KNiFCN.3H2O as ion-exchanger and that loaded with either Cd (II) or Cs (I) as ions from radioactive liquid wastes were investigated. The mechanism of loading of the investigated ions on the ion-exchanger was studied using thermal analysis, XRD and IR techniques. The thermal stability of K2NiFCN and that loaded with different ions were studied up to 800 degree C. Results obtained using differential thermal analysis (DTA) and thermogravimetric analysis (TGA) of the prepared K2NiFCN were discussed to establish new data about the ion-exchanger stability conditions. The TGA of the samples showed the occurance of mass loss on three stages, the first stage up to 100 degree C due to dehydration and formation of anhydrous ion-exchanger. The second stage up to 400 degree C was attributed to the decomposition of the ion-exchanger and the final weight loss stage up to 800 degree C have a steady weight loss values and produces solid homogenous mixture of microcrystalline Fe2O3 and NiO having oxides of spinel structure. The thermal decomposition of potassium nickel ferrocyanides occurred at relatively lower temperature comparing with ion-exchanger loading with cadmium or cesium ions. The kinetic of decomposition was evaluated by means of TGA at different rates. Results showed that the decomposition reaction of K2NiFCN was exothermic with an approximate heat output calculated by different models. The activation energies (Ea) for decomposition was determined using Ozawa and Avrami models