Crystallization of Hydrosodalite Na6[AlSiO4]6(H2O)8 and Tetrahydroborate Sodalite Na8[AlSiO4]6(BH4)2 inside the Openings of Wafer-Thin Steel Mes

Abstract

The zeolitic properties of hydrosodalite Na6[AlSiO4]6(H2O)8 and the reactivity and hydrogen content of tetrahydroborate sodalite Na8[AlSiO4]6(BH4)2 favour both species for future industrial applications. A use in chemical process often efforts a sample preparation in form of membrane-like thin wafers. The present study presents experiments on hydrosodalite as well as BH4-sodalite formation as steel mesh supported thin wafers. Preparation of both sodalite wafers is performerd by the crossover synthesis (CS) from solution to melt flow, first described in [1] [2]. Whereas the space filling of the steel mesh with BH4-sodalite crystals was proved to be a complete close and stable package, hydrosodalite reached only a somewhat weaker quality. Beside the synthesis step, hydrosodalite formation requieres a treatment of the crystal filled mesh at 130°C for 20 h in water to transform the as synthesized hydroxysodalite into hydrosodalite, as known from literature [3] [4] [5]. This leaching procedure was found to be responsible for the obtained loss of quality as demonstrated by a further experiment using a self supported hydrosodalite wafer. Further problems like evolution of pores as a result of the mechanically ripping out the steel inlay from the sample pellets after synthesis have to be solved in future. Nevertheless the results of the present paper are of significance for the development of steel mesh supported hydrosodalite and BH4-sodalite membranes.