Determination of the crystal growth mechanism of KCl in ethanol-water system

The mechanism of crystal growth of KCI in ethanol-water system is studied b y Nielsen's map-model, and the growth rate is estimated by the induction ti me (nucleation rate, growth rate) function in a salting-out ctystallization system. in the experiments, the induction time and the: particle size dist ribution of the final product were measured, and the solid-liquid interfaci al tension was calculated from the induction period data. The map of rate c ontrol of crystal-growth for the KCl-ethanol-water salting out system was c onstructed by taking into consideration that the liquid-vapour interfacial tension varied with the variation of the ethanol concentration, and, as a c onsequence, the solid-liquid interfacial tension varied as well. As a resul t, diffusion controlled crystal growth was obtained as a rate-determining s tep for supersaturation ratios 0.01 < 0.45. For determining the crystal gro wth rate, the nucleation rate was estimated from the experimental average p article number and induction period, applying the assumption that all nucle i were born during the induction period. The results, obtained by using lin ear and non-linear regressions, have appeared to be in good agreement with the data published in the literature. (C) 1999 Elsevier Science B.V. All ri ghts reserved.