Freeze-thawing as a path to concentrate aqueous solution

Phenol-dye aqueous ternary solutions were employed as model eutectic solution, and concentration phenomena during freezing and thawing were investigated. The freeze-concentration level during freezing step and the concentration profiles of the melt fractions during thawing step were examined. It was found that the present freezing conditions did not effectively separate the solutes from frozen zone. Phenol component was slightly concentrated in the top frozen layer though the dye was almost equivalently distributed in the frozen domain. However, the concentrations of melt fractions obtained during thawing step were clearly higher than the concentration level of the frozen domains. Approximately 50% of the both solutes could be recovered from the initial 30% of the melt fraction. It was suggested that concentration behaviour during thawing would be controlled by thawing condition as explained by the kinetics of mass transfer of solutes in the frozen domain and at the frozen interface.