Hydrometallurgical Recovery of Zinc from Industrial Waste

Hydrometallurgical recovery of zinc from industrial waste employs aqueous chemistry to extract zinc from by-products of steelmaking and other metallurgical processes such as electric arc furnace dust, basic oxygen furnace sludge and pickling residues. The process typically involves leaching of zinc-bearing materials in acidic or alkaline media, followed by separation of impurities through neutralisation, precipitation or solvent extraction. The resulting pregnant leach solution is then subjected to electrowinning or precipitation to produce high-purity metallic zinc. This approach reduces reliance on primary ore resources, mitigates environmental impacts from hazardous waste streams and supports circular economy objectives by recycling secondary materials back into production chains. Key challenges include selective dissolution of refractory compounds such as zinc ferrite, control of co-extracted iron and other base metals, and optimisation of reagent consumption and energy use. Advances in process design and integration are driving improvements in recovery efficiency, zinc product purity and valorisation of by-product residues.

Research from Nature Portfolio

One recent study describes an integrated hydrometallurgical route for a zinc oxide ore that combines optimised sulphuric acid leaching with sequential impurity removal and solvent extraction. Under central composite design conditions, an acid concentration around 22 % and a moderate temperature of 45 °C yielded a pregnant leach solution containing over 35 g L⁻¹ zinc alongside manageable levels of iron and manganese. Iron was precipitated prior to extraction, and di(2-ethylhexyl)phosphoric acid was employed to selectively capture zinc in two stages. The system achieved an overall zinc recovery of approximately 71 %, producing a purified solution suitable for electrowinning without roasting or calcination steps. This methodology exemplifies how novel leaching and separation sequences can enhance zinc extraction while reducing conventional thermal pre-treatments.

Hydrometallurgical Recovery of Zinc from Industrial Waste publication trend

The graph below shows the total number of articles in hydrometallurgical recovery of zinc from industrial waste across all publications each year (not limited to Nature Index journals).

Technical terms

Electric arc furnace dust (EAFD): Fine particulate residue from steel furnaces containing high concentrations of zinc, iron oxides and chlorides.

Leaching: Chemical process of dissolving metal species from solid waste into an aqueous phase for recovery.

Solvent extraction (SX): Technique using an organic phase to selectively remove and concentrate metal ions from aqueous solutions.

Electrowinning: Electrochemical deposition method to recover pure metals from solution onto cathodes.

Zinc ferrite (ZnFe₂O₄): Refractory compound commonly present in slags and dust that resists standard leaching agents.

Pregnant leach solution (PLS): Metal-rich aqueous solution obtained after the leaching stage, prior to purification and recovery steps.

References

1. Hydrometallurgical Processes for the Recovery of Metals from Steel Industry By-Products: A Critical Review. Journal of Sustainable Metallurgy (2020).
2. Leaching and solvent extraction purification of zinc from Mehdiabad complex oxide ore. Scientific Reports (2021).
3. Comparison of reduction kinetics of Fe2O3, ZnOFe2O3 and ZnO with hydrogen (H2) and carbon monoxide (CO). International Journal of Hydrogen Energy (2024).
4. Recovery of Pb and Zn from a citrate leach liquor of a roasted EAF dust using precipitation and solvent extraction. Separation and Purification Technology (2020).
5. Recovery of Zinc and Iron from Steel Mill Dust—An Overview of Available Technologies. Materials (2022).