Selective Recovery of Zinc from Metallurgical Waste Materials from Processing Zinc and Lead Ores

Abstract

A method for processing of metallurgical waste materials (chemically defined as sulfur-bearing zinc-ferric materials) produced by plants processing zinc ores and their concentrates is proposed. The method proposed is a combination of pyro- and hydrometallurgical treatments of the waste material. The crucial steps in the developed method include: roasting the material at 450 °C to generate sulfur dioxide (SO2), absorption of SO2 in an aqueous system to form sulfuric acid (IV), carbothermic decomposition of zinc ferrite compounds, and leaching of zinc from the roasted material using sulfuric (IV) acid. The method allows one to extract up to 40% of zinc from the waste material and, consequently, to generate a fraction of material with substantially higher content of iron oxides. The proposed method takes advantage of the presence of sulfur in the processed material which upon roasting is converted to sulfuric acid (IV)—a leaching agent for selective extraction of zinc. The properly adjusted pH of the aqueous medium in which the leaching process is carried out is the key factor determining the quantitative and selective separation of zinc. If the amount of sulfur in the processed material is insufficient, it may be supplemented by adding sulfuric acid (VI) to adjust the pH. The method proposed was tested at a laboratory scale and quarter industrial scale using the real samples taken from stockpiles in the vicinity of the plant processing zinc and lead ores in Poland. It may also work for any zinc-ferric materials from various sources.

High-Performance Method of Recovery of Metals from EAF Dust—Processing without Solid Waste

“…Despite low operating costs of equipment and a more favourable energy balance, compared to pyrometallurgical processes, hydrometallurgical methods require great meticulousness and control of many parameters (concentration, pH of the solution) to maintain adequate efficiency of the zinc extraction process. This applies to both acidic (sulphuric acid) and alkaline (soda lye) solutions and does not always allow selective precipitation of the other metals contained in the processed steel dust [22][23][24].…”

Recovery of ZnO from lead-zinc flotation tailings by hydrometallurgical processes: XRD, SEM, and AFM studies

“…The hydrometallurgical route of zinc oxide is primarily based on zinc hydroxide or basic zinc carbonate [5,6]. The common recovery method of oxidized lead and zinc minerals from lead-zinc ores at present is flotation in practice [7 -9].…”

Recovery of Lead and Zinc from Zinc Plant Leach Residues by Concurrent Dissolution-Cementation Using Zero-Valent Aluminum in Chloride Medium

“…By applying a concurrent dissolution and cementation technique, both Pb and Zn were removed using a low concentration of NaCl, and most importantly Pb-the most toxic metal in ZPLRs-was captured and separated before the solid-liquid separation, hence, eliminating the need for extensive washing of the generated residues to remove the inherent residual solution.Metals 2020, 10, 531 2 of 15 generated as a result of more extensive mining, mineral processing, and metal extraction operations by metallurgical processes [5][6][7]. For example, zinc (Zn) metal production via hydrometallurgical processes (i.e., leaching of calcine or zinc oxide minerals followed by electrowinning of Zn) generates huge amounts of zinc plant leach residues (ZPLRs) [8,9], which are stockpiled and often abandoned after closure of mining/processing operations.With the rapid depletion of high-grade ores, ZPLRs are now considered as secondary resources because they still contain substantial amounts of residual Zn, copper (Cu), lead (Pb), and iron (Fe) [10][11][12][13]. From an environmental point of view, ZPLRs are considered hazardous wastes because they contain hazardous heavy metals such as Pb, Cu, and Zn.…”

“…When appropriate, the latter approach is preferred because it is less energy-intensive and generates wastes (e.g., solid residues) that may cause less or no secondary environmental pollution. Numerous studies have been published to process metallurgical wastes using conventional hydrometallurgical processes that follow the sequence of leaching, solid-liquid separation, and recovery of dissolved metals (usually Cu, Pb, and Zn) from pregnant leach solutions [9,11,[20][21][22][23]. Although effective, there are two serious drawbacks of conventional approaches for Pb and Zn extraction-recovery from ZPLRs.…”

“…Metals 2020, 10, 531 2 of 15 generated as a result of more extensive mining, mineral processing, and metal extraction operations by metallurgical processes [5][6][7]. For example, zinc (Zn) metal production via hydrometallurgical processes (i.e., leaching of calcine or zinc oxide minerals followed by electrowinning of Zn) generates huge amounts of zinc plant leach residues (ZPLRs) [8,9], which are stockpiled and often abandoned after closure of mining/processing operations.…”