Molten molybdenum-(copper)-iron-sulfur mattes or alloys, obtained for example, by reacting slags or other molybdenum containing oxide residues or waste materials with an iron and/or sulfide reductant, are enriched in molybdenum and copper (if present) by a pyrometallurgical process. The molten matte or alloy material is oxidized to remove sulfur, as sulfur oxides, while varying amounts of iron are converted to iron oxides which separate from the metallics. The oxidation thus enriches the molybdenum and copper content of the remaining alloy. Silica flux may be added during the reaction process to form a fluid slag with the iron oxide which separates from the remaining molybdenum-iron-(copper) material which constitutes the product.

In a method of operating a copper smelting furnace, wherein a ferrous substance containing more than 80 wt. % metallic iron having a specific gravity of 3.0-8.0 and particle diameter of 0.3-15 mm is added to copper smelting slag containing Fe having an oxidation-reduction number of 3+ and to the Fe.sub.3 O.sub.4 in the intermediate layer, thereby deoxidizing the Fe.sub.3 O.sub.4 to FeO, the method reduces the Fe.sub.3 O.sub.4 within the slag layer and the Fe.sub.3 O.sub.4 generated in the intermediate layer between the slag layer and the matte layer. So that their viscosity is reduced and separation rate is increased, thus increasing the yield rate of useful metal, and the problems that originate in the intermediate layer are eliminated.

A method of recovering metals and producing a secondary slag from base metal smelter slag produced by a copper or nickel smelter includes mixing the smelter slag with at least one reducing agent selected from the group consisting of carbon and aluminum, said carbon (if present) being from about 1% to about 10% by weight of the slag and said aluminum (if present) being from about 5 to about 30% by weight of the slag, and with from zero to about 60% calcium oxide by weight of the slag. The mixture is heated above the eutectic melting point thereof directly and to ignition temperature aluminothermically (if aluminum is present as reducing agent) to reduce the iron silicate to ferrosilicon containing substantially all the copper, nickel and cobalt which was in the smelter slag and form a secondary slag comprising at least one compound selected from the group consisting of calcium silicate, calcium aluminate and calcium iron aluminum silicate. The ferrosilicon is then separated from the secondary slag.

Molten molybdenum-copper-iron-sulfur mattes or alloys, obtained, for example, by reacting slags or other copper-molybdenum containing oxide residues or waste materials witn an iron and/or sulfide reductant, are enriched in molybdenum and copper by a pyrometallurgical process. The molten matte or alloy material is first carburized whereupon a copper-rich matte phase separates from the alloy phase and is removed. The molten alloy phase is next treated one or more times by the addition of sulfur or pyrite resulting in the formation of additional copper-rich matte as a separate phase which is separated after each treatment, leaving an alloy of molybdenum and iron of reduced Cu content. Finally the alloy is desulfurized to provide a commercial product.

Process for recovering nickel and nickel-copper from molten smelter-type slags or other highly oxidized sources of nickel and nickel-copper containing 7 to 30 percent by weight of magnetite (Fe.sub.3 O.sub.4). The magnetite in the slag is reduced with carbonaceous materials or other solid reductants such as sulfides, metals or carbides. While the slag is mixed with a fluid cooled, metal-bladed mechanical stirrer, the reductant is reacted with the slag. As a result of stirring the reductant into the slag, the rate of magnetite reduction is highly accelerated. With the reduction, the nickel or nickel-copper (as well as cobalt, if present) separates into a phase as either immiscible metal, a sulfide, or a nickel-copper-iron-sulfide matte, depending upon the initial composition of the slag.