2021 年 21 巻 1 号 p. 12-15
When the aqueous solution is frozen, pure ice is first formed on the frozen interface and solutes and suspended solids are concentrated in the unfrozen part. We will explain the outline of the freeze concentration separation method that uses this phenomenon to be able to recover rare resources, and explain the usefulness of irradiating the frozen interface with ultrasonic waves as a mean to obtain a clean frozen part even if the freezing rate is increased. I introduced that among solutes, substances with a larger diffusion coefficient are more likely to be concentrated and separated.