A reduced iron production method includes: a reduction-step of producing reduced iron by heating an agglomerate containing iron oxide and carbonaceous reducing agent to reduce the iron oxide and solidifying a product produced by melting the reduced iron; a first-magnetic-separation-step of separating, among granular metallic iron, first slag, and second slag containing more fine-granular metallic iron than the first slag that are contained in the product, at least the granular metallic iron from the first slag by use of a first magnetic separator to separate first slag containing substance and a granular metallic iron containing substance from each other; a second-magnetic-separation-step of separating the second slag from the first slag containing substance or the granular metallic iron containing substance by use of a second magnetic separator having attraction force different from attraction force of the first magnetic separator; and a crushing-step of crushing the second slag.

A method for the treatment of black slag, which contains lime (CaO) or lime-based compounds, and which is generated in an electric furnace that produces steel from scrap, includes indirectly cooling the black slag immediately after the black slag exits from the electric furnace or after collection of the black slag in a cauldron, for a period of time between about 10 minutes and about 45 minutes.

Pyro-hydrometallurgical methods are described to economically and environmentally recover a target metal from iron slag or steel slag. For instance, the method can enable subjecting an iron or steel slag feed to acid-baking with an acid to produce a dried mixture comprising at least one soluble metal salts, then subjecting the dried mixture to water leaching to an aqueous solution comprising an aqueous leachate rich in said target metal and solid residues and subsequently separating the aqueous leachate rich in said target metal from the solid residues. This acid-baking water-leaching method facilitates efficient recovery of target metal compared to conventional methods.