PURPOSE: To increase the amt. of a soln. treated by an ion exchange resin before the resin requires regeneration by activating the resin having coloring matter adsorbed to the limit of the adsorbing power by stirring with a stirrer or blown inert gas.

CONSTITUTION: At the time when an ion exchange resin packed into a column well adsorbs coloring matter and coloring matter remains in a soln. discharged from the column, the resin in the column is stirred with a stirrer or inert gas blown from the bottom or by back washing with water. The resin is activated to restore the adsorbing performance and the activated resin treats a soln. again without leaving coloring matter. In case of the stirrer, the resin in the column can be stirred by the stirring blade driven by a motor.