JP2972524B

PURPOSE:To successively precipitate the lead and zinc in an incinerated ash as the sulfides and to fractionally recover the lead and zinc efficiently by supplying sodium sulfide to a soln. containing eluted heavy metals from the ash and regulating the pH of the soln. CONSTITUTION:The incinerated ash of refuse, etc., is mixed with hydrochloric acid to elute the heavy metals from the ash, and solid is separated from liq. to prepare the soln. of the heavy metals. Sodium sulfide or gaseous hydrogen sulfide is supplied while agitating the soln., and the pH is regulated to 0.4-1.2 to precipitate lead as the sulfide, which is separated and recovered. Sodium sulfide or gaseous hydrogen sulfide is then supplied to the soln. separated from the precipitate, and the pH is regulated to >=2 to precipitate the zinc as the sulfide, which is separated and recovered. Consequently, lead and zinc are fractionally separated from the incinerated ash efficiently, and the waste water generated in the recovery is made harmless.