Comprehensive Study on the Mechanism of Sulfating Roasting of Zinc Plant Residue with Iron Sulfates

Abstract

Zinc plant residue (ZPR) is a secondary material generated during hydrometallurgical zinc production that contains considerable contents of valuable elements such as Zn, Cu, Fe, Pb, Cd, Ag, In, Ga, Tl. Zinc, copper and accompanying elements in ZPR are in different minerals, mainly in the ferrites. A promising approach for recycling ZPR is the sulfating roasting using iron sulfates followed by water leaching. In this study, the composition of ZPR and the obtained products were thoroughly investigated by various methods including X-ray diffraction analysis (XRD), chemical phase analysis and Mössbauer spectroscopy. The effect of temperature, amount of iron sulfates and roasting time on the conversion of valuable metals into a water-soluble form was thermodynamically and experimentally studied both using pure ferrites and ZPR. Based on the results of time-resolved XRD analysis and synchronous thermal analysis (STA), a mechanism of the sulfation roasting was elucidated. The rate-controlling step of zinc and copper sulfation process during the ZPR roasting was estimated. The sulfating roasting at 600 °C during 180 min with the optimal Fe2(SO4)3∙9H2O addition followed by water leaching enables to recover 99% Zn and 80.3% Cu, while Fe, Pb, Ag, In, Ga retained almost fully in the residue.

Selective Lead Extraction from Zinc Calcine and Zinc Leaching Residue by Leaching with Monoethanolamine Solvent Systems

“…The leaching optimization for ZC was performed at different leaching times (1, 3, and 6 h) and leaching temperatures [room temperature (RT), 35 and 50 °C] in a water bath. Leaching optimization for ZLR was performed at different leaching times (3,6,12, and 24 h) and leaching temperatures (RT and 100 °C) in a water bath. Additionally, ZLR leaching at 150 °C has been tested in a Flexiwave (Milestone) microwave (MW) system for 15, 30, and 60 min.…”

“…The zinc sulfide concentrate is calcined in a first roasting step and converted into chemically more reactive zinc oxide (ZnO), which is also known as zinc calcine (ZC) . During roasting, some parts of the zinc and other nonferrous metals react with iron impurities to form the challenging-to-dissolve zinc ferrite (ZnFe 2 O 4 ) . Roast–Leach–Electrowin (RLE) is the main metallurgical process that produces more than 95% of the current global zinc supply. , Herein, ZC is leached by sulfuric acid, while other metal impurities remain in the zinc leaching residue (ZLR).…”

Sustainable Management Strategy for Solidification/Stabilization of Zinc Plant Residues (ZPR) by Fly Ash/Clay-Based Geopolymers

“…Currently, approximately 80% of zinc is produced from Sphalerite, a zinc sulfide mineral, by the roasting-leaching-electrowinning (RLE) process, which is a combination of pyrometallurgy and hydrometallurgy [4,5]. The process of the roasting of zinc sulfide concentrates is a substantially cost-effective technology due to its self-sufficiency, a satisfactory removal of harmful impurities for the subsequent electrolysis, and the associated production of sulfuric acid [6]. In the leaching stage with strong hot sulfuric acid, other metals present in the calcine concentrate are also leached in addition to zinc [7].…”

“…In the production of one ton of zinc refined by the RLE process, between 80 and 100 kg of Cadmium Sponge [9] and 40 to 50 kg of Anode Mud are generated [3]. These residues contain considerable amounts of valuable metals, such as zinc, cadmium, copper, and nickel [4,6]. Several studies have investigated the recovery of cadmium and copper from Cadmium Sponge [8,9,[16][17][18] and the recovery of noble metals from Anode Mud [11,19,20].…”

A novel leaching process of zinc ferrite and its application in the treatment of zinc leaching residue

“…For instance, reducing gases including CO and H2 change zinc ferrite into weak acid soluble zinc oxide and magnetically separated iron oxides [7,8]. Roasting by sulphate makes zinc in zinc ferrite be water soluble zinc sulphate [9,10]. However, these ways have no apparent advantages over carbothermal reduction method because the resulting residue or slag demands further safe and effective utilization.…”