Zinc recovery from purified electric arc furnace dust leach liquors by chemical precipitation

The present work aims at determining the experimental conditions for the recovery of zinc from leach liquors, produced through dilute sulphuric acid leaching of electric arc furnace dust (EAFD), at atmospheric pressure. Zn can be recovered as an easily filterable precipitate. More specifically, zinc was precipitated by 99.5% with the form of a mixed white fine crystalline powder, comprising of hydrozincite (3ΖnCO3.3Zn(OH)2) and zinc carbonate hydroxide hydrate (ZnCO3.3Zn(OH)2.H2O). Zn precipitation was carried out in a pH range of 6.5-7 at 25 °C. The addition of different types of carbonated salts, such as sodium carbonate, sodium bicarbonate or ammonium carbonate, either with the form of suspensions or as solids, was investigated. The produced precipitates were characterized through means of particle size distribution analysis, chemical analysis, X-ray diffraction (XRD), thermogravimetric/differential analyses (TG-DTA) and Fourier transform infrared spectroscopy (FT-IR), whereas their microstructure and morphological characteristics were studied by scanning and transmission electron and microscopy (SEM/TEM). High grade zinc precipitates were obtained, as manganese concentrations did not exceed 1%, whereas traces of Cr, Cu and Pb were also detected.