To provide a method for recovering valuable metal from heavy metal sludge capable of suppressing the generation of harmful gas with small using energy at a low cost.
This method is composed of a 1st stage in which heavy metal sludge contg. nickel and cobalt is dissolved with an acidic agent, thereafter, this dissolution soln. is filtered, and substance which is not dissolved into the acidic soln. is filtered away, by which an extraction original liq. is produced, a 2nd stage in which the extraction original liq. produced by the 1st stage is subjected to alkali treatment, and thereafter, metallic hydroxide precipitated by the alkali treatment is filtered away, by which a raw nickel-cobalt soln. is produced and a 3rd stage in which the crude nickel-cobalt soln. is subjected to reducing treatment and is thereafter subjected to alkali treatment as well, and the precipitated metallic hydroxide is filtered away, by which a pure nickel- cobalt soln. is produced.
MATSUSHITA MASAYUKI
SAEKI CHIKA
