Role of gel aging in template-free synthesis of micro and nano-crystalline sodalites

A  facile  effective  stirring  aging  at  room  temperature  prior  to  conventional  hydrothermal treatment was employed in the template-free synthesis of micro- and nano-crystalline sodalites with  two  different  initial  gel  compositions.  The  effect  of  initial  Si/Al  molar  ratio,  NaOH concentration and stirring aging time were investigated on the morphology and particle size of the  synthesised  sodalites.  The  results  revealed  that  applying  various  stirring  aging  time  can change  the  proportion  of  the  contaminant  phase  associated  with  sodalite  and  alter  the morphology of the sodalite crystals from wool ball-like consisting of nano-threads to cabbage-like with  nano-leaves,  as well  as  size  distribution  of  nanocrystalline  sodalite. The  size  of  the nanocrystals was in the range of 50-80 nm as observed by FE-SEM and the yield was as high as about 15%.