Zn recovery from steel mill EAF dusts: A two-step biotechnological approach

The growing demand for recycling strategies intended for electric arc furnace (EAF) dusts to recover secondary raw materials calls for innovative approaches that align with environmentally compatible practices. For the recovery of Zn, biogenic sulfuric acid was produced utilizing A. thiooxidans in a reactor in a fed-batch mode. The acid was then used in leaching experiments endeavoring to determine optimal leaching parameters for an efficient Zn extraction while retaining Fe in the dust matrix. At 30 °C, 100 g L−1 pulp density, and at a leaching duration of 10 min, a concentration of 30 g L−1 of Zn equivalent to a leaching efficiency of 76.67 % was found in the leachate while only 0.02 % of the Fe went into solution, indicating a good separation of these two metals. To purify the leaching solution, 48 % Fe was precipitated by adjusting the pH to 3.8 using NaOH. The extraction of Zn from the leachate was then achieved using a microbial electrolysis cell (MEC) with a two-chamber H-cell setup, with the chambers being separated by a proton exchange membrane. The average Zn recovery from the leachate was 99.9 ± 0.1 % and a final Zn purity on the electrode of 99.2 % was achieved.