Lead and zinc selective precipitation from leach electric arc furnace dust solutions

Abstract

Electric-arc furnace (EAF) dust is considered a hazardous industrial waste. In this work, chemical and mineralogical investigations of EAF dust from Siderúrgica Rio-Grandense (RS, Brazil) were performed. The elements aluminum, calcium, lead, cadmium, chromium, magnesium, manganese, nickel, potassium, silicon, sodium, tin, iron, zinc, sulphur, oxygen, and carbon were found in EAF dust. The concentration of zinc and iron showed an average value of approximately 20% (weight basis) and these elements are mainly present as ZnO.Fe2O3 (zinc ferrite) and ZnO (zincite) mineralogical phases. Also, EAF dusts were submitted to an integrated hydrometallurgical process composed by a hydrolyzed step, followed by a fusion step and a strong alkaline leaching. A subsequent chemical precipitation was carried out in order to promote selective separation of zinc and lead from the leach solution. Sodium sulphide was successfully employed as precipitant agent. When the weight ratio of sodium sulphide to lead was around 2.0, lead could be selectively extracted from leach solution. After lead precipitation without zinc concomitant loss, a weight ratio of sodium sulphide to zinc of around 3.0 was used to precipitate all zinc. Thus, EAF dust has a great potential to be used as a source of metals extraction due to its rich chemical composition and also for the viability of the proposed selective separation process.