Processing of a Zinc Leach Residue by a Non-Fossil Reductant

Minna Rämä*, Lassi Klemettinen*, Marja Rinne, Pekka Taskinen, Radosław Markus Michallik, Justin Salminen, Ari Jokilaakso

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

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The suitability of a non-fossil reductant in high-temperature treatment of a zinc leach residue was studied in laboratory-scale experiments. The pyrometallurgical experiments carried out at temperatures of 1200-1350 °C consisted of melting the residue under an oxidizing atmosphere to produce an intermediate, desulfurized slag, which was further cleaned of metals such as Zn, Pb, Cu, and Ag, using renewable biochar as a reductant. The aim was to recover valuable metals and produce a clean, stable slag for use as construction material, for example. The first experiments indicated that biochar is a viable alternative to fossil-based metallurgical coke. The capabilities of biochar as a reductant were studied in more detail after optimizing the processing temperature at 1300 °C and modifying the experimental arrangement by adding rapid quenching of the sample (to a solid state in less than 5 s) to the procedure. Modifying the slag viscosity by adding 5-10 wt % MgO was found to enhance the slag cleaning significantly. With an addition of 10 wt % MgO, the target Zn concentration in slag (Zn < 1 wt %) was reached after as little as 10 min of reduction, and the Pb concentration was also decreased relatively close to the target value (Pb < 0.03 wt %). With an addition of 0-5 wt % MgO, the target Zn and Pb levels were not reached within 10 min, but with longer treatment times of 30-60 min, 5 wt % of MgO was enough to decrease the Zn content in slag sufficiently. The lowest Pb concentration achieved with an addition of 5 wt % MgO was 0.09 wt % after a 60 min reduction time.

Original languageEnglish
Pages (from-to)21450–21463
Number of pages14
JournalACS Omega
Issue number24
Early online date5 Jun 2023
Publication statusPublished - 20 Jun 2023
MoE publication typeA1 Journal article-refereed


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