Abstract: The residues arising from industrial processes and from waste disposal which are polluted with heavy metals and/or heavy metal compounds, are subjected to a two-stage reduction process with formation of re-usable metal-containing and silicon-containing alloys. In a first reduction stage, using carbon or carbon-generating means as the reduction means, the compounds of silicon and metals are reduced, which have a standard potential which is greater than that of silicon. Following separation of the reduced metals, the residue obtained, which contains aluminum in oxidized form, is subsequently converted to a salt melt and this salt melt is subjected to a second reduction stage of a fused salt electrolysis, yielding an aluminum and silicon melt. The process is particularly suitable for filter residues from waste incineration plants.