Formation and morphology of asymmetric NaCl particles precipitated at the liquid-liquid interface

摘要

Asymmetric particles of NaCl and KC1 crystals have been obtained by using a crystallization method.The particles were produced by precipitation at the solution-1-butanol interface.The two solvents are essentially immiscible,but have slight mutual diffusion.When the aqueous solution contacts with 1-butanol,the interfacial area becomes supersaturated,resulting in nucleation and particle growth in the interfacial zone.The asymmetric particles featured a stepped surface on the side in contact with 1-butanol.The other surfaces in contact with the aqueous phase were a flat cubic structure.Precipitated NaCl particles showed very clear asymmetric structure.However,some of KC1 particles had less well-defined structures.This is due to the high diffusion rate of hydrated K ions and the fast diffusion results in a supersaturated state around the interface.This situation can be explained by a model of crystal growth based on solute clusters in supersaturated solutions.