Controllable synthesis of sodalite submicron crystals and microspheres from palygorskite clay using a two-step approach

Sodalite submicron crystals and microspheres were successfully synthesized from natural palygorskite clay through a two-step approach by varying the synthetic parameters. The effects of initial NaOH concentration, SiO2/Al2O3 molar ratio, and aluminium source on the morphology and particle size of synthetic sodalite were investigated, as well as the formation scheme of synthetic sodalite. Experimental results showed that the alkalinity of the synthesis gel controlled by initial NaOH concentration and SiO2/Al2O3 molar ratio was a critical factor for the formation of sodalite crystals and microspheres. Sodalite crystals could be synthesized at high initial NaOH concentration and SiO2/Al2O3 molar ratio, however, low initial NaOH concentration and SiO2/Al2O3 molar ratio were beneficial for the formation of sodalite microspheres via submicron crystal aggregation.