Elaboration of FAU-type zeolite beads with good mechanical performances for molecular decontamination

FAU-type zeolite beads were formed through an shearer/mixer using organic binder (carboxymethylcellulose (CMC)) or inorganic binder (anhydrous sodium metasilicate (Na₂SiO₃)).

Comparison between leached metakaolin and leached diatomaceous earth as raw materials for the synthesis of ZSM-5

Inexpensive raw materials have been used to prepare ZSM-5 zeolites with SiO₂/Al₂O₃ molar ratios in the range 20 – 40. Kaolin or Bolivian diatomaceous earth was used as aluminosilicate raw materials and sodium hydroxide and n-butylamine were used as mineralizing agents and template. Dealumination of the raw materials by acid leaching made it possible to reach appropriate SiO₂/Al₂O₃ ratios and to reduce the amount of iron and other impurities. After mixing the components and aging, hydrothermal treatment was carried out and the products were recovered The results clearly show for the first time that well-crystallized ZSM-5 can be directly prepared from leached metakaolin or leached diatomaceous earth using sodium hydroxide and n-butylamine as mineralizing agents and template under appropriate synthesis conditions. A longer induction time prior to crystallization was observed for reaction mixtures prepared from leached diatomaceous earth, probably due to slower digestion of the fossilized diatom skeletons as compared with that for microporous leached metakaolin. The use of leached diatomaceous earth allowed higher yield of ZSM-5 crystals within comparable synthesis times. However, low amounts of Mordenite formed, which was related to the high calcium content of diatomaceous earth. Another considerable advantage of diatomaceous earth over kaolin is that diatomaceous earth does not require heat treatment at high temperature for metakaolinization.

Formation of nanostructured, nanocrystalline boron nitride microparticles with diatom-derived 3-D shapes

The first use of diatom frustules as shape-dictating 3-D templates for the syntheses of nanostructured, nanocrystalline micro-particles of a non-oxide ceramic, boron nitride, is demonstrated.