Anti-solvent effect of crystallization by feeding ethanol after and during microwave radiation

摘要

Crystallization in microwave systems has been extensively investigated because of its advantages of high yields, polymorph selectivity, rapid growth, and production of nanocrystals and mono-disperse crystals [1-3]. Homogeneous heating and induction heating arising from the rotation of polar molecules occurs during crystallization; however, the mechanism remains unclear. Consequently, it is difficult to determine the operating conditions required to obtain a desired crystal size distribution (CSD). Recently, we observed nanoparticle behavior in situ under microwave radiation in order to clarify the microwave effect at the nano level [4]. Temporary aggregation of nanoparticles caused by microwave radiation was observed and the possibility of nucleation induction by instantaneous irradiation in saturated solutions was demonstrated. Anti-solvent crystallization is widely used to obtain fine crystals and a rapid growth rate [5-7]. Accordingly, we combined the anti-solvent effect and microwave radiation to achieve a stable crystallization process. Sodium chloride crystals were produced in aqueous solutions under microwave radiation in order to understand how to control and predict the CSD. In our previous study [8], important factors, such as microwave power, stirring speed, and anti-solvent concentration in the suspension system, has been investigated to elucidate the process of anti-solvent crystallization. In this study, feeding rate of anti-solvent was varied, and persistence of microwave effect before the feeding was investigated.