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The influence of sodium cations content in zeolite Beta crystals of different sizes (between 200 nm and 2 μm) on the adsorption of pollutants (dioxin and polychlorobenzene) is investigated. In this study, protons which balance the negative charge of the zeolitic framework are partially replaced by sodium cations. Chemical, structural and textural analyses performed on the exchanged crystals indicate that the exchange rates reached 75-80 % and that the structure of zeolites is preserved. Adsorptions of pollutants in zeolite Beta samples were successfully carried out using 1,2-dichlorobenzene (gas phase) and 2,3-DiChloroDibenzo- p-Dioxin: 2,3-DCDD (liquid phase) but reveal different behaviors. Indeed, all samples adsorb the same amount (around 7 molecules) of 1,2-dichlorobenzene per unit-cell of zeolite, whereas the dioxin adsorption amounts increase with the amount of sodium cations. Compared to their protonic forms, the dioxin adsorption capacities were multiplied by a factor of 1.3 for the sodium exchanged small crystals (size between 200 nm and 1 μm) and by a factor of 4 for the sodium exchanged microcrystals (size between 1 and 2 μm) for an equilibrium concentration of 2,3-DCDD of 0.5 mmol/L in both cases. [ABSTRACT FROM AUTHOR]

This work focuses on different ways to improve the yield and/or the crystalline quality of EMT/FAU-type zeolite nanocrystal aggregates obtained in the presence of organic additive triethanolamine (TEA). The increase of the amount of aluminum reagent enhances the synthesis yield by a factor of 2.5 without affecting the crystallization rate and the microporous volume. On the other hand, the increase of the thermal treatment time allows to increase the synthesis yield, the crystallization rate and the microporous volume. Furthermore, addition of EMT zeolite seeds into the starting reaction medium improves the crystallization rate and the microporous volume. [ABSTRACT FROM AUTHOR]

The present study demonstrates an optimized procedure for mass production of EMT-type structure zeolite. The introduction of triethanolamine (TEA) in the synthesis gel leads to the formation of larger and agglomerated nanocrystals. The obtained particles can be easily recovered from the reaction medium by filtration and washing without the use of high speed centrifugation. This simple approach paves a new way for energy-efficient synthesis of nanoporous materials for potential industrial applications. [ABSTRACT FROM AUTHOR]