Method of recovering metals and producing a secondary slag from base metal smelter slag

A method of recovering metals and producing a secondary slag from base metal smelter slag, said smelter slag comprising at least one heavy metal selected from the group consisting of copper, nickel and cobalt and also comprising iron silicate and other metallic compounds and elements including (by weight):

• from about 10% to about 50% SiO.sub.2,
• from about 0% to about 10% Al.sub.2 O.sub.3,
• from about 25% to about 50% Fe,
• from about 0% to about 20% CaO,
• from about 0% to about 15% MgO,
• from about 0% to about 15% Cu,
• from about 0% to about 15% Ni,
• from about 0% to about 7% Co,
• from about 0.2% to about 3% S
• said method comprising:
• mixing the smelter slag with at least one reducing agent containing aluminum, said aluminum being from about 2% to about 35% by weight of the slag, and up to about 70% calcium oxide by weight of the slag, heating the mixture aluminothermically above the melting point to reduce the smelter slag to a metal alloy containing iron, and said at least one heavy metal which was in the smelter slag and thereby also producing a secondary slag containing at least one compound selected from the group consisting of calcium silicate, calcium aluminiate, fused alumina and calcium iron aluminum silicate, and separating the alloy from the secondary slag.