Methods and systems are provided for extracting and utilizing the energy contained in molten slags generated from metal producing operations. The energy is extracted while the slag is contained within a vessel, such as, a slag pot, after the slag has been discharged from a furnace. The energy is accessed by immersing into the slag a thermally stable treatment vessel, such as, a vessel made of graphite, having an internal cavity. The energy from the slag is transmitted by direct contact of the slag with the surface of the treatment vessel. The treatment vessel and slag may be moved relative to each other to overcome the low thermal conductivity of the slag. Any substance placed within the internal cavity is heated without directly contacting the molten slag. The methods and systems provide for high temperature chemical reactions, energy conversions, or transfer operations within the internal cavity.

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.