This work reports on the effective sequestration of Eu(III) ions from aqueous solutions using three types of metal-organic frameworks (MOFs) constructed from benzene-1,3,5-tricarboxylic acid (H₃BTC) linker and Ca²⁺, Cu²⁺, or Al³⁺ metal nodes. The MOFs possessed an exceptionally high Eu adsorption capacity of 635 (91% removal), 642 (92% removal), and 628 mg g⁻¹ (90% removal) for Cu-BTC, Ca-BTC, and Al-BTC, respectively, at pH 7 for an initial Eu concentration of 350 mg L⁻¹. The MOFs were hydrolytically stable and possessed a high Eu adsorption capacity in a wide pH range of 4–8. While the pseudo-second-order model explained the adsorption kinetics, the adsorption process followed the Langmuir-Freundlich isotherms. The analysis confirmed that the Eu adsorption process was governed by chemical interactions between the carboxylic acid/carboxylate group and Eu(III) ions via complexation or ion exchange mechanism. A multi-metal adsorption study confirmed a preferential adsorption behaviour for trivalent lanthanides over divalent cations due to comparatively stronger interactions between Ln³⁺ ions and carboxylate groups. The XPS findings suggested Eu−OOC and Eu(OH)₃ formed over the MOFs' surface after Eu adsorption. These MOFs were effectively regenerated for multiple cycles using 0.1 mol L⁻¹ EDTA solution. Thus, the study demonstrated low-cost MOFs with superior regeneration capabilities for the capture of Eu(III) ions from waste solutions.

https://doi.org/10.1016/j.jece.2023.110084