Zinc electrowinning from flue dusts at a secondary copper smelter and connected adhesion problems of the metal deposits

The secondary copper smelter “Metallhütte Carl Fahlbusch” (MCF), Rastatt, Federal Republic of Germany is discussed, with particular consideration of the MCF zinc electrowinning process from low-grade, chloride-containing flue dusts. The investigations performed were focussed on the adhesion of zinc deposits on the aluminium cathodes. With laboratory tests using the tankhouse electrolyte and an apparatus for measuring the adhesion force, the influence of the electrolyte impurities lead, cadmium, cobalt, nickel, tin and antimony on the adhesion behaviour and on the current efficiency have been determined. Field tests to affect the adhesion of the zinc deposits on aluminium cathodes by dip pretreatment of the cathodes with glue or sodium resinate reveal that with only small sodium resinate additions in the dipping bath better stripping can be achieved.