Investigation of industrial waste materials for hydrometallurgical recovery of zinc

Three industrial waste materials were examined in terms of their elemental and phase compositions, leaching behaviour in sulphuric acid solutions followed by solution purification and zinc electrowinning. Two dusts being mixtures of metallic zinc and zinc oxide of various proportions and zinc ash, containing simonkolleite additionally, were used. All materials characterized with high zinc percentages (60-80%). Zinc extraction from the materials was high (89-99% in 25% H2SO4) after short time of leaching. In all cases transfer of zinc ions to the leachate was accompanied by different levels of solution contamination in iron, manganese and chloride ions. Leaching of the materials was an exothermic process. Precipitation purification was carried out by using traditional method (oxidation followed by alkalization with CaCO3). Electrolysis parameters (current efficiency, voltage, energy consumption) were typical for zinc electrowinning, but surface morphology of zinc deposits was affected by chloride ions in the electrolyte.