Extraction of Mn and Sr from electrolytic zinc slime using SO2-containing flue gas as reductant

In the zinc production industry using Mn-rich zinc ore, substantial quantities of anodic slime are generated during electrolytic zinc production, containing ∼ 40 % Mn and ∼ 3 % Pb. While a valuable secondary resource, this material poses environmental risks as solid waste. Conventional reductive leaching methods rely on costly reductants and generate high carbon emissions. This study introduces a process utilizing flue gas from zinc plants as a reductant, achieving 92 % Mn leaching efficiency while simultaneously extracting 25 % Sr and fixing 92 % SO 2 as sulfate in solution. Kinetic analysis shows a mixed control model with an activation energy of 13.83 kJ/mol, with reaction rates further enhanced by optimizing gas inlet design. The MnSO 4 -rich leachate is processed into battery-grade MnSO 4 powder, and Sr is recovered as SrCO 3 , suitable for use as an additive in electrolytic zinc processes. Additionally, NaOH consumption for flue gas desulfurization decreases significantly from 2.14 kg to 0.17 kg per Nm 3 . Economic evaluation indicates reagent costs represent only 2 % of the total value of MnSO 4 and SrCO 3 products, offering a sustainable pathway for anodic slime utilization and SO 2 mitigation in zinc smelting.