Molecular Simulation Of Pyrithione Zinc Crystallization And Experimental Study On Anti-solvent Jet Crystallization

In this paper,the crystallization process of zinc pyrithione(ZPT)was mainly studied.ZPT particles with different morphologies were prepared by three crystallization methods including cooling crystallization,anti-solvent crystallization and jet crystallization.At the same time,the morphology of ZPT was investigated.The morphology of ZPT was simulated using Materials Studio(MS)software.In the research system of sodium chloride-water-ethanol,anti-solvent jet crystallization method was used to study the regulation of sodium chloride particle size.During the crystallization experiment of ZPT,the ZPT obtained in the cooling crystallization experiment has a large particle size about 300 ?m.The ZPT crystal particles obtained by the anti-solvent method have smaller particle size and the particle size ranges from 5 ?m to 30 ?m,but the particle size distribution is not uniform.The ZPT particles obtained by the jet reaction crystallization experiment have small size and uniform distribution.At the same time,the effect of surfactant on the morphology of ZPT was studied.Scanning electron microscopy results show that the ZPT morphology obtained by anti-solvent method is rod-like structure,the ZPT particles synthesized by jet reaction crystallization are hexagonal prism-like structure and rod-like structure.MS software was used to simulate the morphology of ZPT.Starting from the internal structure of ZPT crystals,the possible morphologies of ZPT in vacuum were simulated by molecular simulation using BFDH model,attachment energy model and equilibrium morphology model,respectively.Since the three theoretical models did not consider the influence of the external environment on the crystal morphology,in this simulation,the ZPT morphology was simulated using the occupancy model.Occupancy model considers both the influence of the solvent and the solute on the crystal surface.The results show that the simulated morphologies are agree with the experimental results.At the same time,the effect of surfactant on the morphology of ZPT was simulated.The simulation results obtained by adding the surfactant in the water molecule layer were consistent with the results of anti-solvent crystallization and jet reaction crystallization experiments.In order to explore the rule of particle size regulated by anti-solvent jet crystallization experiment,sodium chloride was used as model compound,water was used as good solvent and ethanol was used as poor solvent.The anti-solvent jet crystallization method was used to investigate the effect of fast jet mixing on the anti-solvent crystallization process.The effects of temperature,poor solvent/good solvent flow ratio,sodium chloride concentration,and solvent effect on the particle size of sodium chloride were systematically investigated.The experimental results show that the morphology of sodium chloride is cube,and has nothing to do with the research factors.When the experimental temperature is 10°C and 25°C,the particle size and distribution of the sodium chloride product are less different.When the volume flow rate of the poor solvent and the good solvent increases from 1 to 2,the particle size of the product decreases and the distribution becomes narrower,and the flow ratio is further increased to 4 or 6,and the obtained particle size and distribution change little.When the concentration of sodium chloride increased from 19wt% to 23wt%,the particle size of the obtained product becomes smaller,and the particle size distribution becomes narrower.When the solvent effect factor is studied,the total amount of sodium chloride,total water,and total ethanol in the system were not changed,with the decrease of the volume ratio of solvent water in sodium chloride solution and the increase of the volume ratio of ethanol,the particle size of sodium chloride is obviously reduced and the particle size distribution is narrowed.