Development of quantifying supersaturation to determine the effect of the anti-solvent on precipitation in liquid-liquid interfacial crystallization

Crystallization has been used in various industries to separate solid materials from solutions. The transition from the liquid phase to the solid phase occurs because the solubility decreases upon cooling, evaporation, and the addition of anti-solvents. Properties of solid materials are generally controlled by changing the driving force or supersaturation, which can be freely changed by operating factors such as the cooling rate and addition rate of anti-solvent. Recently, spherical crystallization has been developed as a new process for creating functional partides. In spherical crystallization, counter-diffusion between anti-solvent and water increases supersaturation and promotes crystallization. However, the supersaturation during spherical crystallization is particularly difficult to control because quantifying the rate of mass transfer between two liquids is difficult. The present work proposes a calculation method for quantifying the supersaturation in spherical crystallization. NaCl and glycine crystals were prepared with organic solvents, and the amount of precipitation was measured. The effect of the anti-solvent on the amount of precipitation was investigated. These results revealed that the amount of NaCl and glycine precipitation can be described by the supersaturation distribution inside the droplets in comparison with numerical calculations. (C) 2020 Elsevier B.V. All rights reserved.