Sonocrystallisation refers to a process that combines together high-intensity ultrasound (HIU) with crystallization. This work presents systematic investigations on sonocrystallisation to elucidate the effects of key variables on sonocrystallisation. We use a continuous flow sonocrystallization apparatus to prepare sodium chloride microparticles from a NaCl-ethanol-water antisolvent system. Data from experiments is used to develop a model that is subsequently used in an optimization step to identify the optimal operating conditions. Through implementing a full factorial experimental design, we investigated the effects of ultrasonic power, antisolvent feed rate, system flowrate and the sonication time on product crystal size. It was found that when the antisolvent feed rate or the ultrasonic power increase, the particle size decreases. This is in contrast to increasing the system flow which results in larger particle sizes. A regression model was produced to map the main effects of different factors as well as their interactions. The model was also used to determine the optimal experimental levels of different factors to minimize the particle size of the product. Furthermore, a high speed camera was used to map the forming bubbles’ motion and distribution revealing that changing the ultrasonic power and the system flow are affecting the bubbles’ motion and distribution.
A second set of experiments investigated the effect of ultrasound on polymorphism of paracetamol. Results indicated that changing the ultrasonic power in the range, or the pulsation regime of application does not have any effect on paracetamol polymorphism, however, it affects the size and shape of paracetamol crystals.