| abstract |
In the reactor 20, the used alkaline permanganate etching solution 12 is accommodated, and an alkaline earth metal hydroxide 14 such as calcium hydroxide is added to the reactor, the liquid in the reactor is stirred, and the filter 28 is used to The liquid is discharged from the side or upper end, and the precipitate 26 adhering to the filter is scraped off, and the precipitate containing poorly soluble or insoluble matter accumulated in the bottom of the reaction tank without passing through the filter is discharged from the reaction tank. |