Selective Leaching of Rare Earth Elements from Ion-Adsorption Rare Earth Tailings: A Synergy between CeO₂ Reduction and Fe/Mn Stabilization

Abstract

The increasing demand for rare earth elements (REEs) motivates the development of novel strategies for cost-effective REE recovery from secondary sources, especially rare earth tailings. The biggest challenges in recovering REEs from ion-adsorption rare earth tailings are incomplete extraction of cerium (Ce) and the coleaching of iron (Fe) and manganese (Mn). Here, a synergistic process between reduction and stabilization was proposed by innovatively using elemental sulfur (S) as reductant for converting insoluble CeO 2 into soluble Ce 2 (SO 4 ) 3 and transforming Fe and Mn oxides into inert FeFe 2 O 4 and MnFe 2 O 4 spinel minerals. After the calcination at 400 °C, 97.0% of Ce can be dissolved using a diluted sulfuric acid, along with only 3.67% of Fe and 23.3% of Mn leached out. Thermodynamic analysis reveals that CeO 2 was indirectly reduced by the intermediates MnSO 4 and FeS in the system. Density functional theory calculations indicated that Fe(II) and Mn(II) shared similar outer electron arrangements and coordination environments, favoring Mn(II) over Ce(III) as a replacement for Fe(II) in the FeO 6 octahedral structure of FeFe 2 O 4 . Further investigation on the leaching process suggested that 0.5 mol L −1 H 2 SO 4 is sufficient for the recovery of REEs (97.0%). This research provides a promising strategy to selectively recover REEs from mining tailings or secondary sources via controlling the mineral phase transformation.

Insights into the Selective Transformation of Ceria Sulfation and Iron/Manganese Mineralization for Enhancing the Selective Recovery of Rare Earth Elements

“…The results obtained from in situ XPS spectra agreed with the XRD patterns of the solid residues obtained from the magnetic separation after residue sulfation (Figure C), in which magnetite (FeFe 2 O 4 ) and jacobsite (MnFe 2 O 4 ) were indexed. Previous research also reported the shorter bond lengths of Fe–O (2.05 Å) and Mn–O (2.01 Å) in the octahedral sites of FeFe 2 O 4 and MnFe 2 O 4 , respectively, than Ce–O (2.18 Å) of CeFe 2 O 4 after the geometry optimization, indicating that the generation of Fe/Mn spinel is energetically favorable than CeFe 2 O 4 in the system …”

Fast Screening of Coal Fly Ash with Potential for Rare Earth Element Recovery by Electron Paramagnetic Resonance Spectroscopy

“…In addition, the aluminosilicates in Al-rich CFAs may also host REYs. Another possibility is that, to some extent, Mn­(II) can also form hydroxides or oxides of ferromanganese with the EPR spectral feature of type (c) to adsorb or complex REYs. − …”

Wyzwania i możliwości odzysku w gospodarce odpadami podczas procesów wydobycia i wzbogacania rud zawierających uran i tor – przegląd

“…These can create environmental risks if not managed properly. Overall, the recovery of REEs and other nuclear raw materials from waste is an important area of research due to the increasing demand for these elements and the potential environmental risks associated with their disposal (kursun et al 2018;Xiong et al 2019;Reynier et al 2021;Altıner et al 2021;zhou et al 2021;Guo et al 2022;Aziman et al 2023). These research investigations can also be evaluated in terms of sustainable development and feasibility.…”