Ultrasound-assisted antisolvent crystallisation of trans-chalcone

Antisolvent crystallisation of trans-chalcone was investigated under both silent and ultrasound (US)-assisted conditions. Solubility, metastable zone width (MSZW), crystal yield, crystal structure, morphology, and particle size and shape distribution were evaluated. The solubility of trans-chalcone at 30 °C decreased as the water mass fraction increased and was correlated using the Jouyban-Acree model. MSZW increased with increasing antisolvent addition rate. Under silent conditions, crystal yield decreased with increasing temperature. Therefore, US-assisted experiments were performed at 30 °C. US was applied after the cloud point to examine its post-nucleation influence on recovery and crystal attributes. The recovery efficiency relative to the maximum attainable yield increased from 71% under silent conditions to 86% at a nominal US power of 30 W, then decreased at higher US powers. PXRD patterns showed no evidence of a major structural transformation, although relative peak intensities varied with US power. The average crystallite size decreased from 44.8 nm under silent conditions to 29.8 nm at 20 W. FESEM images indicated plate-like crystals with US-associated surface irregularities (pits), while image-based particle size and shape analysis (using SOPAT) showed only limited size reduction and negligible change in aspect ratio. These results suggest that post-nucleation US can be used to selectively improve crystal recovery and modify crystal attributes through an optimal choice of operating conditions.