Influence of salt on nanozeolite-Y particles size synthesized under organic template-free condition

Zeolite-Y is one of the preferred micro-sized zeolite commonly used as a catalyst and for adsorption and separation. The size and shape of zeolite crystals have great influence on their properties therefore the synthesis of nano-size zeolite-Y has received much attention with straightforward methodology. In the present study, nano-sized zeolite-Y crystals were synthesized by the clear-solution (CS) and dense-gel (DG) methods in the presence of alkali metal chloride salt (i.e. NaCl) under organic template-free condition. The influence of the salt on the growth of nano zeolite-Y crystal size and morphology was studied systematically by varying the NaCl concentration. Depending on the method selected for synthesis (CS or DG), the growth of nano-size crystals was affected by the addition of NaCl content. In the CS method, the size of zeolite-Y crystals was found to decrease from 120 nm to 60 nm with an increase of salt content which signify the influence of salt in hindering diffusion of nutrients to the crystal nuclei in a homogeneous starting gel. Whereas, the spherical aggregates of well-shaped nanocrystals were formed with an increase of crystal size in the case of DG method. This is attributed to the suppression of the rate of crystal dissolution in dense-gel system upon introduction of salt ions. The nano-size zeolite-Y synthesized by both methods exhibited comparatively higher water adsorption capacity (15.4 ± 0.38–16.2 ± 0.41 mmol/g) than commercially available micro-size zeolite-Y (12.9 mmol/g) which can be attributed to the contribution of the meso/macropores arising from the inter-crystal voids. Hence, the synthesized nano-size zeolite-Y can be considered as promising adsorbents for water adsorption applications.