Selective Extraction of Zinc from Zinc Ferrite
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Selective Extraction of Zinc from Zinc Ferrite Vivek Kashyap 1
&
Patrick Taylor 1
Received: 15 July 2020 / Accepted: 11 September 2020 # Society for Mining, Metallurgy & Exploration Inc. 2020
Abstract The presence of iron in sphalerite induces the formation of zinc ferrite (ZF) during roasting. Zinc refinery residues (ZRR) and electric arc furnace dust (EAFD) contain a significant amount of zinc ferrite and are difficult to treat. According to the literature, up to 71% ZF has been found to be present in ZRR. The dissolution of zinc ferrite is inefficient even in aqua regia. The Waelz process is an existing process to recover zinc from electric arc furnace dust by reduction using carbon monoxide followed by the volatilization of zinc. In this study, zinc was selectively extracted from zinc ferrite by partial reduction of zinc ferrite at relatively low temperature followed by leaching in dilute sulfuric acid (20 g/L). Pure zinc ferrite samples were partially reduced to zinc oxide and magnetite by using H2 gas as a reductant. The presence of magnetite and zinc oxide was confirmed by X-ray diffraction (XRD) technique. A maximum of 95% zinc extraction was achieved after leaching with sulfuric acid on the reacted samples. The paper also discusses the effect of time, temperature, and concentration of H2 in the reducing gas on the extraction of zinc and iron from ZF. Keywords Reduction roasting . Dilute acid leaching . Zinc ferrite . Zinc refinery residue . Zinc extraction
1 Introduction Zinc refinery residues (ZRR) have been the focus of studies related to the recovery of trace elements such as gallium, germanium, and indium. In addition to these trace elements, it can also be a potential source of zinc as the zinc content usually varies from 15 to 30% in ZRR [1–3]. Also, some ZRR have been deemed hazardous due to high mercury (Hg) content [4]. The authors stated that 2000–3000 tons of hazardous ZRR is being produced annually from Danxia smelter alone in China. Processing of ZRR is difficult primarily due to the presence of zinc ferrite (ZF). Zinc ferrite constitutes one of the major phases in ZRR. The presence of iron in sphalerite induces the formation of zinc ferrite during roasting [5]. ZF (ZnFe2O4) and zinc metasilicate (ZnSiO3) were recognized as the major phase constituents in ZRR [2]. The phase composition of zinc residues estimated by chemical phase analysis yielded 71.16% of zinc ferrite [3]. ZF is also one of the primary phases in electric arc furnace dust (EAFD), which is a residue generated from the steel industry. The presence of zinc ferrite in these residues makes the extraction of zinc and iron
* Vivek Kashyap [email protected] 1
Colorado School of Mines, Golden, CO, USA
difficult as most of the zinc is present in the form of zinc ferrite. Zinc ferrite has been found as the major component of EAFD in several studies [6–8]. In the year 2000, 700,000 to 800,000 tons of EAFD were being generated in the USA per year [9]. As reported in the year 2010, the global annual production of EAFD is
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