A multi-step hydrometallurgical treatment capable of extracting up to 70% of zinc from electric arc furnace dust (EAFD) has been developed and validated by researchers at the Universidad de Sevilla, according to a study published in the Journal of Sustainable Metallurgy in April 2026. The findings carry direct implications for the secondary zinc supply chain at a time when electric arc furnace steelmaking is rapidly expanding its global footprint. EAFD is one of the most zinc-rich industrial residues available at scale.
For every ton of steel produced via the EAF route, approximately 20 kilograms of dust are generated, according to data cited in the study. With global steel production reaching 1,892 million tons in 2023, as reported by the World Steel Association, the volumes of EAFD produced annually represent a significant potential source of secondary zinc. The electric arc furnace route currently accounts for 30% of global steel production and is expected to grow further due to its lower carbon footprint compared to the traditional blast furnace-basic oxygen furnace route.
EAFD samples used in the study, provided by Siderúrgica Sevillana S.A. in Spain, contained an average zinc content of approximately 24 weight percent, underscoring the material's relevance as a secondary zinc feedstock. Despite this potential, recycling rates for EAFD remain low. According to estimates cited by the authors, only 2.5 million tonnes out of a total of 6 million tonnes of EAFD generated globally were being recycled as of a 2009 assessment.
The remainder has historically been consigned to industrial landfills following stabilisation treatment, a practice facing increasingly stringent regulatory restrictions worldwide. The gap between generation and recycling volumes represents a substantial untapped resource for the zinc industry, particularly as primary zinc mining faces ongoing constraints. The process developed by Teresa Miranda, Nieves Iglesias-González, and Pablo Ramírez of the Universidad de Sevilla's Department of Chemical Engineering proceeds in sequential steps designed to maximise zinc recovery while maintaining high selectivity against iron dissolution.
In the first stage, the EAFD is washed at a controlled pH of 10 to remove chlorides, which would otherwise interfere with downstream zinc recovery by electrowinning and could generate dioxin emissions if the material were reintroduced into the furnace. This washing stage requires 27 grams of sulfuric acid per kilogram of EAFD processed. The washed residue is then subjected to selective acidic leaching using sulfuric acid at a pH of 1.5 and 25 degrees Celsius, consuming 500 grams of sulfuric acid per kilogram of EAFD.
Under these conditions, the process achieved zinc extraction yields of up to 70%, consistent with results reported by other research groups using sulfuric acid leaching, while iron dissolution was kept to 8.9%, leaving the iron concentrated in the solid residue for potential reuse in steelmaking. The authors note that the remaining 30% of zinc not extracted is largely associated with franklinite, a zinc iron oxide mineral whose complex crystallographic structure resists mild acid leaching conditions. The researchers highlight that hydrometallurgical approaches such as this one offer lower capital expenditure and lower operating expenditure compared to pyrometallurgical alternatives such as the Waelz kiln process, which is currently the dominant industrial technology for EAFD treatment, owing to reduced energy consumption requirements.
The study does not provide explicit cost estimates or scale-up data, but the authors describe the process as compatible with circular economy principles and note that the zinc recovered in the pregnant leach solution can be valorised through selective precipitation as zinc oxide, subsequently redissolved to produce commercial derivatives such as basic zinc carbonate or electrolytic zinc. Complementing the zinc recovery process, the iron-rich solid residue remaining after acid leaching also contains lead in the form of anglesite, which must be removed before the residue can be safely recirculated into the electric arc furnace. The researchers addressed this through a brine leaching step using sodium chloride solutions, achieving lead extraction rates above 90% under optimal conditions of 20 degrees Celsius, 100 grams per litre of sodium chloride, and pH 3.
The dissolved lead is subsequently fully recovered by precipitation with sodium carbonate, forming insoluble carbonate compounds, while the brine solution is recycled within the process. The resulting iron-rich solid, containing 42.5 weight percent iron and only 0.13 weight percent residual lead, is then suitable for reintroduction into the electric arc furnace. This integrated lead management step is presented by the authors as a key enabler for the full valorisation of EAFD rather than a primary focus of the work.
The study, published in volume 12 of the Journal of Sustainable Metallurgy with DOI 10.1007/s40831-026-01491-2, was conducted with EAFD samples supplied by Siderúrgica Sevillana S.A. and received open access funding from the Universidad de Sevilla and CBUA. The authors declare no conflicts of interest. The research represents a novel application of established hydrometallurgical separation techniques to a persistent challenge in EAFD processing, namely the removal of the anglesite phase that forms after acid leaching and has traditionally limited the reuse of leaching residues in steelmaking.
Source: idus.us.es