TRACE ORGANIC CONTAMINANT CONCENTRATION BY FREEZING .3. ICE WASHING

Recovery of organic solutes is improved by ice washing after concentration by freezing from aqueous solution. At comparable freezing rates, -12°C bath temperature, and mixing, 80 rev/min, it was demonstrated that even with ice washing, the organic solute recovery decreased with increased dissolved salt content. A kinetic analysis of the experimental data shows that in complex systems containing both organic and inorganic solutes, the organic recovery does not follow the idealized model relationships derived for normal freezing. The effective distribution coefficient is not constant but varies with fraction frozen. This effect is postulated to be the result of morphological alternation of the forming ice phase with resultant incorporation of solute-rich liquid. Ice washing in such instances can only recover the solute present in the surface film retained when the liquid concentrate is decanted. © 1969.