Recovery of rare earth elements from sediments affected by mining activities

Sediments affected by diverse mining activities contain elevated levels of rare earth elements (REEs), yet the feasibility of recovering REEs from these sediments remains unclear. In this study, we reviewed literature on REE-rich sediments impacted by various mining activities and focused on reservoir sediments in southern China affected by ion-adsorption REE mining as a case study. These sediments, formed from the aggregation of suspended colloids and particles transported by streams in mining areas, contained total REEs ranging from 0.13 % to 0.32 %, with most REEs associated with Fe-Mn oxides. Organic acids, particularly EDTA-Na₂, efficiently extracted REEs through ligand complexation. Subsequent purification with (NH₄)₂SO₄, oxalate precipitation, and calcination yielded REE oxides with > 95 % purity and an 89 % recovery rate from sediment to final product. Life cycle assessment and cost-benefit analysis showed that EDTA-Na₂ extraction had significantly lower environmental impacts and economic costs compared to other methods. This study indicates that mining-impacted sediments could serve as viable secondary REE sources, with EDTA salts providing a cost-effective recovery option.