Spontaneous crystallization of potassium chloride from aqueous and aqueous-ethanol solutions Part 1: Kinetics and mechanism of the crystallization process

摘要

Kinetics of spontaneous crystallization of potassium chloride from aqueous and aqueous-ethanol solutions were studied. During the crystallization of the salt the electrical conductance and optical transmission of the supersaturated solutions were measured automatically. For monitoring of the total surface of growing potassium chloride crystals at the crystallization the turbidimetric method was used. The growth rate and activation energy of the crystals were determined. The crystal growth rate was proportional to supersaturation. When the volume fraction of ethanol in the solution increased from 0 to 25.76%, the activation energy of the growth process did not change and was about 60 kJ-mol(-1). Aggregation of the crystals was found. The aggregation kinetics of the crystals may be described approximately by the famous Smoluchowski equation for coagulation of colloidal particles. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.