Desalination of spent ion-exchange resin regeneration solutions by suspension freeze crystallization

Abstract

The aim of this work is to evaluate the desalination of spent ion-exchange resin regeneration solutions by freeze suspension crystallization. The main steps used during freezing experiments are solution cooling followed by seeding to start the nucleation and then sweating in order to increase the purity of the obtained ice crystals. The study has shown that the purity of the ice crystals is highly dependent on the operating conditions. The obtained results have shown that seeding, an increase in stirring speed and a diminution in crystal growth rate lead to higher yields by decreasing the value of total dissolved solids (Si) of ice crystals from 6.34 to 2.59 g/L without a significant effect on the recovered mass (from 220.97 to 202.23 g, respectively). Moreover, adding the sweating step at the end of the process has led to increase the ice purity by melting the impure areas until reaching an Si value of about 0.63 g/L after 5 h of sweating (with a loss of mass of about 13.6%). The effect of the solution salinity was also evaluated and the results showed that freezing process performance decreases with increasing the salinity of spent ion-exchange resin regeneration solutions.