Crystallization of paracetamol from aqueous solutions in a planar oscillatory flow crystallizer: effect of the oscillation conditions on the nucleation kinetics

The isothermal crystallization of paracetamol from aqueous solutions in a planar oscillatory flow crystallizer was used as a model system to study the effect of the oscillation conditions on the nucleation kinetics. The nucleation rate was calculated from the probability distribution of detection times, and the kinetic, A, and thermodynamic, B, parameters were estimated from the classical nucleation theory for several combinations of frequency and amplitude. The low values of A that were obtained, as compared to theoretical estimations, suggest that heterogeneous nucleation should be the dominant nucleation mechanism in this study. The low values of the effective interfacial energy that were obtained from B, as compared to theoretical estimations for homogenous nucleation, also corroborate that hypothesis. A first-order model was formulated to describe the effect of the oscillation conditions on A. A similar model was not formulated for B as it should be independent from the oscillation conditions. A increased as the amplitude increased at both low and high frequencies. Similarly, A also increased as the frequency increased at high amplitudes, but it decreased at low amplitudes. These results enabled the identification of optimal oscillation conditions according to the desired final product properties.