Kinetics of the essential oil hydrodistillation from sweet flag ( <i>Acorus calamus</i> ) rhizomes: comparison of basic models

Abstract Background This study investigated the hydrodistillation process for extracting essential oil from sweet flag ( Acorus calamus ) rhizomes. The primary objectives were to evaluate the influence of the water‐to‐rhizome ratio on both the yield and chemical composition of the essential oil and to model the extraction kinetics. Results The water‐to‐rhizome ratio was found to significantly influence the yield of essential oil, with the highest yield (1.36 ±0.01%) obtained at a ratio of 11:1. However, variations in this ratio did not result in significant changes in the chemical composition of the oil. A first‐order kinetic model was identified as the most suitable for describing the hydrodistillation process, offering simplicity and strong agreement with experimental data. Conclusion The kinetic profile revealed a rapid initial increase in yield, corresponding to the washing phase — where readily accessible oil on the surface is removed—followed by a slower ‘diffusion’ phase, during which the essential oil gradually diffuses from the rhizome matrix into the distillate. © 2025 Society of Chemical Industry (SCI).