Disposal Strategy of Ion-Adsorption Rare Earth Elements Low-Level Radioactive Residues: Reduction Emission and Recovery for Aluminum and Uranium by Alkaline and Alkalescent Media

Hindered by the separation among radioactive elements, aluminum (Al), and rare earth elements (REEs), acid methods encounter persistent obstacles in reduction emission of ion-adsorption rare earth elements low-level radioactive residues (IREEs-LRR). This work reported a stepwise strategy for the reduction of emission and recovery of Al and uranium (U) from IREEs-LRR by alkaline and alkalescent media. As one of the main phases, Al(III)-containing compounds of IREEs-LRR were first converted into soluble NaAl(OH)4 with NaOH solution at ordinary pressure. Na2U2O7 and the adsorbed state U(VI), as detected by speciation, were then transformed into soluble uranyl carbonate in a Na2CO3-NaCit solution. The total removal yields of Al and U approached 97 and 94 wt %, respectively, engendering an 84 wt % loss weight of IREEs-LRR. Additionally, the REEs content in the residues increased from 0.88 to 3.6 wt %, while the specific activity of U decreased from 5.6 to 1.9 Bq/g. The mechanism was related to the NaOH-mediated dissociation of Al(III) polymeric complexes coupled with the enhanced dissolving capacity of uranium (U(VI)) complexes in alkalescent medium. This paper provides a novel strategy for reducing residual radioactivity, enriching REEs, and recovering valuable Al and U from IREEs-LRR.