Apparatus and method for refining alkaline solution

摘要

An electrolytic bath is divided into an anodic chamber and a cathodic chamber by a cation-exchange membrane. A base alkaline solution of high impurity concentration is supplied into the anodic chamber from a tank of a base material as well as a circulating anolyte overflowed from the anodic chamber is supplied and circulated from an anode circulating tank, and NaOH solution of low impurity concentration is supplied and circulated into the cathodic chamber through a tank of a refined solution. The concentration of the circulating anolyte is detected, and based on this detected value the supplying amount of the base NaOH solution is controlled and electrolysis is performed. Thus, the concentration of NaOH solution in the anodic chamber is kept stable, and the refined NaOH solution of low impurity concentration can be obtained in the cathodic chamber.