Hydrothermal Reactivity of Na-n-Micas (n = 2, 3, 4)

High charge mica samples, with layer charge values between 2 and 4, have been synthesized via the sodium chloride melt procedure, and their hydrothermal reactivities for the formation of lutetium disilicate have been evaluated. Characterization of the synthesized micas, through a combination of techniques that inform of both the long and the short range order of the solids, indicates a progressive incorporation of aluminum in the tetrahedral sheet as the layer charge increases. Hydrothermal treatment of the synthesized samples causes the reaction between the lanthanide ions in the solution and the tetrahedral silicate species from the micas to form a new crystalline lanthanide disilicate phase. Those samples with higher layer charge show the higher reactivity, in accordance with our initial hypothesis. In conclusion, these samples have a novel and attractive application through a new reaction mechanism, of special relevance for the storage of high activity radioactive waste.