Growth kinetics of potassium chloride II—Water–ethanol systems

The growth and dissolution kinetics of potassium chloride in water+ethanol solutions were studied in a pilot-scale fluidized bed crystallizer. The experiments were carried out for different contents of ethanol in the solution and the results interpreted in terms of the thermodynamic driving force. The results thus obtained were compared to data from pure aqueous solutions, showing that for the same driving force the growth and dissolution rates of KCl decrease, as the concentration of ethanol augments. The observed decay of the KCl dissolution rates was interpreted in terms of the reduction of the diffusivity of the ionic salt in the mixed solvents.Independent of the ethanol's content, the growth rates were found to be of first order with respect to the thermodynamic driving force. It was also inferred from the experimental results that the alcohol, besides decreasing the diffusion in volume, hinders the integration of the solute in the crystalline lattice. The latter effect may be ascribed to a blocking effect exerted by the large organic molecules that accumulate in the adsorption layer.