(424h) Ultrasound-Intensified Crystal Nucleation in Different Solvents: The Role of Solute Diffusion and Solvation Effect

Nucleation rate greatly affects crystallization period and thus has significantly impacts on production efficiency [1]. Nucleation process can be accelerated by changing crystallization environments and applying some outfield intensifying methods [1, 2]. But the joint effect between these common methods remains indistinct. Here, the combined effect of solvent environment and ultrasound intensification on nucleation kinetics is investigated. The discrepancy in the ability of ultrasound to accelerate nucleation in different solvents is discovered, and the key factors affecting the ability are unveiled. Over 1500 nucleation induction time experiments of 3,5-dimethoxybenzoic acid in three solvents environments (ethanol, acetonitrile, acetone) under ultrasonic and non-ultrasonic conditions show that the enhancement on nucleation rate in these solvents by ultrasound ranges from 1% to 116%, which has obvious divergence in different solvents. Furtherly, a series of comparative experiments combined with computational chemistry including molecular dynamics (MD) simulation and density functional theory (DFT) calculation jointly reveal that the enhancement degree is mainly affected by solute diffusion and solvation effect. On the one hand, the weaker the diffusion ability of solute in a certain solvent, the more significant the enhancement effect of ultrasound on the nucleation in such solvent system. On the other hand, solvation effect is the main factor determining the order of nucleation rate in the three solvents. A stronger solvation on solute will make the nucleation more difficult. Therefore, the introduction of ultrasound enhances nucleation in each solvent to varying degrees, but does not change the order of nucleation rate in the three solvents.

[1] R. Prasad, S.V. Dalvi, Chem. Eng. Sci. 226 (2020) 115911.

[2] D. Khamar, J. Zeglinski, D. Mealey, Å.C. Rasmuson, J. Am. Chem. Soc. 136 (2014) 11664-11673.