Effects of ultrasonic irradiation on crystallization and structural properties of EMT-type zeolite nanocrystals

• Nanosized EMT zeolites are formed from rice husk ash under ultrasonic irradiation.
• The effects of ultrasonic waves in nanosized EMT zeolite synthesis are studied.
• Ultrasound induces rapid crystal growth and produces high zeolite yield.
• Smaller zeolite nanocrystals with high crystallinity and large defect sites are obtained.
• Improved surface hydrophilicity of crystals is beneficial for water sorption applications.

Synthesis of EMT zeolite nanocrystals from rice husk ash biomass (RHA) under continuous ultrasonic irradiation is reported. The aging, nucleation and crystallization stages of EMT zeolite in the system were monitored at ambient temperature, and compared with the conventional hydrothermal method. It was found that ultrasonic wave induced rapid crystal growth of the nanosized EMT zeolite. Complete crystallization of EMT nanocrystals was achieved within 24 h which was much faster than conventional hydrothermal synthesis (36 h). Furthermore, XRD and TEM analyses revealed that more nuclei were formed during the nucleation stage, allowing the preparation of smaller zeolite nanocrystals with high crystallinity. The results also showed that sonocrystallization produced EMT zeolite with high yield (ca. 80%). The ultrasound-prepared EMT nanocrystals were also found to have high porosity and high hydrophilicity, making the material promising for water sorption applications including vapor sensing, heat pump and adsorption technologies.

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