The manner which recovers cerium nitrate ammonium from the etching foul solution which includes cerium nitrate ammonium.

摘要

PROBLEM TO BE SOLVED: To recover cerium nitrate ammonium from a cerium nitrate ammonium-containing etching waste solution after use for an etching stage at a high purity by a simple method.;SOLUTION: The etching waste solution is evaporated and concentrated in a pressure-reduced evaporator 1 to precipitate the crystals of cerium nitrate ammonium, and the crystals are separately recovered from the solution. On the other hand, the separation solution freed from the crystals is mixed into the etching waste solution in the evaporator, and a part of the mixed solution or a part of the separation solution is blown out of the system. Thus, the exceeding of the concentration of impurities in the solution within the evaporator from a fixed prescribed value is prevented.;COPYRIGHT: (C)2004,JPO