High-charge Micas Research Articles

Novel acidic solids from high charge Na-micas by mild hydrothermal treatment

A new meso-porous structure with a significant increment in the acidity and surface area has been developed from a novel family of swelling brittle micas – Na- n-Mica ( n = 2, 3 and 4), where n is the layer charge per unit cell – for the first time. The uncommon high charge micas with up to four interlayer cations per unit cell have been synthesized following the “NaCl melt method”, and treated with an aluminium aqueous solution in a Teflon vessel closed in a stainless steel reactor at 150 °C for 48 h. The diffusion of aluminium hydroxide complexes into the bidimensional galleries of the silicate has been successfully achieved in the three samples avoiding any pre-swelling step, and confirmed by XRD. After hydrothermal treatment, inherent acidic sites located in the tetrahedral layer of those swelling micas become accessible by the formation of a partially delaminated-intercalated structure, creating a new interesting family of highly acidic materials. Finally, thermal stability of the acidic centres, and textural properties of the synthesized samples after calcination have been also tested.

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

AbstractChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract, please click on HTML or PDF.

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.