Clean Ion-Exchange Technologies. 3. Temperature-Enhanced Conversion of Potassium Chloride and Lime Milk into Potassium Hydroxide on a Carboxylic Ion Exchanger

Abstract

This paper reports the results obtained by studying the ion-exchange synthesis of potassium hydroxide from lime milk and carboxylic resin Lewatit CNP 80 in the K-form. Carboxylic resin has been shown to have several advantages in comparison with, for example, sulfonate ion exchanger, due to its higher selectivity toward Ca2+, which substantially enhances at elevated temperature. The increase of temperature from 293 to 333 K enhances the sorption of Ca2+ versus K+ that allows achieving far higher KOH concentration in the solution phase. The values of equilibrium separation factor, α, for Ca2+−K+ exchange have been determined at 293 and 333 K by varying the equivalent fraction of Ca2+ in the solution phase from 0.04 to 0.7. A remarkable increase of α values has been observed at higher temperatures and at low calcium content in the solution phase. The regeneration of the resin (conversion from Ca- to K-form) has been carried by using the mixtures of potassium chloride and potassium sulfate. The regeneration ...