Exploring electric arc furnace dust as a new source of rare earth elements: comparative leaching strategies and two-step selective precipitation

The recovery of rare earth elements (REEs) from electric arc furnace dust (EAFD) was investigated through a post-bioleaching process involving leaching and selective precipitation. Due to the low extraction efficiency in the bioleaching process, bio and chemical leaching were performed on the EAFD bioleaching residues using metabolites from Yarrowia lipolytica and Acidithiobacillus thiooxidans , as well as citric and sulfuric acids. Sulfuric acid was the most effective leaching agent, achieving a REEs concentration of 119.6 mg/l under optimized conditions (1 M, 6 h, 30 °C). Precipitation was then employed to recover REEs using oxalic acid and disodium carbonate. Oxalic acid precipitated cerium selectively but removed a significant amount of manganese, limiting its selectivity. A two-step precipitation strategy using disodium carbonate was developed to enhance the purity of REEs. The first step efficiently removed iron and a portion of manganese, while the second step focused on REEs recovery. In this situation, the enrichment factor of the total REEs content reached 148. Speciation modeling with MEDUSA software supported experimental findings and guided the process. This integrated approach demonstrates the feasibility of post-bioleaching REEs recovery from the EAFD, offering insights into process design and metal separation strategies.