Innovative pilot-scale process for sustainable rare earth oxide production from coal byproducts: A comprehensive environmental impact assessment

• Published in: Journal of rare earths 2024-04
• Main Authors: Rabbani, Mohsen, Werner, Joshua, Fahimi, Ario, Vahidi, Ehsan
• Format: Article
• Language: English
• Subjects: Coal by-products; Environmental impacts; Life cycle assessment; Precipitation; Rare earth elements; Rare earth oxide
• ISSN: 1002-0721
• DOI: 10.1016/j.jre.2024.04.004

This study developed a pilot-scale process feeding with two different materials resulting from a column leaching process and acid mine drainage (AMD) streams to recover rare earth elements (REEs). A life cycle assessment (LCA) study was done to evaluate the environmental impacts of rare earth production from deleterious material in the form of highly contaminated leachate (HCL) and low-contaminated leachate (LCL). The results indicate that the main contributors to environmental categories that produce RE-hydroxide stages are NaOH and electricity. Also, oxalic acid, Na2CO3, and hydrochloric acid significantly contribute to the production stage of individual rare earth oxides (REOs), including solvent extraction (SX) and precipitation steps. The HCL route has higher environmental impacts than LCL due to higher chemical/energy and H2SO4 usage, so 468 and 292 kg of carbon dioxide are generated to produce 1 t of individual REOs from HCL and LCL routes, respectively. Moreover, the carbon dioxide emitted from the process, including the RE-hydroxide production, SX, and REOs production, is less than 10 t CO2. A sensitivity analysis was also performed to assess the changeability of the environmental footprints of the main inputs in the SX process, as the main stage has a higher contribution to the whole process. This LCA study is the first step toward understanding the environmental influence of new processing methods to produce REEs from coal by-products through a developed pilot-scale process. An LCA study was done on a pilot-scale process to obtain REOs from coal refuse. The environmental footprints of REOs production via two separate ways were assessed. NaOH, followed by electricity, is the main contributor for RE-hydroxide production. H2SO4 used in heap leaching raises HCL route's environmental impact by 12% on average. Oxalic acid, HCl, and Na2CO3 greatly contribute to individual REOs production stage. [Display omitted] •An LCA study was done on a pilot-scale process to obtain REOs from coal refuse.•The environmental footprints of REOs production via two separate ways were assessed.•NaOH, followed by electricity, was the main contributor for RE-hydroxide production.•H2SO4 use in heap leaching raised HCL route's environmental impact by 12 % on average.•Oxalic acid, HCl, and Na2CO3 greatly contribute to individual REOs production stage.