Effect of supersaturation on crystal size and number of crystals produced in antisolvent crystallization

The antisolvent crystallization of sodium chloride was carried out in batches to observe crystallization phenomena using ethanol as an antisolvent. To decrease high local supersaturation generated by the addition of antisolvent, the authors have proposed a new idea by choosing high ethanol concentration operational conditions. Obtained crystals seemed to be unagglomerated and monodispersed in the optimum range of ethanol concentration. From the observation of nucleation phenomena, it was considered that nucleation induced by the antisolvent addition occurred due to the local supersaturation generated at the boundary of the starting and feed solutions. On the other hand, crystal growth is considered to proceed by the supersaturation generated by sufficient mixing between the starting and feed solutions. Average crystal size increased with the increase of σ_R. The number of produced crystals increased with the increase of the starting solution concentration C. The induction period for nucleation tended to decrease with increase of C and σ_R. Since the number of produced crystals depended on C, nucleation was considered to be influenced by local mixing between the starting and feed solutions.