Thermochromatographic volatility studies of actinide oxides

These surprising and controversial reports motivated us to study the volatility of oxidic actinide species in trace amounts in the O2-H2O(g)/SiO2(s) system by thermochromatography. The enhanced volatility of trioxides in a moist atmosphere due to formation of volatile oxide hydroxides in reactions with water as established for uranium and the group 6 elements is indicative of the oxidation of PuO2 to the trioxide, the more so as M(IV)O2 and M(V)2O5 oxides do not form volatile oxide hydroxides. Trace amounts of Mo and W have shown an analogous behavior in gas chromatographic experiments in silica glass columns which are governed by the surface reactions dissociative adsorption and associative desorption. In the present work the actinides Th through Am were studied. Th and Pa oxides were considered as reference oxides of actinides having a maximal oxidation state of +4 or +5, respectively, uranium as a reference actinide reacting to the volatile UO2(OH)2(g). (orig.)