Safe and sustainable by design MOF beads for selective entrapment and recovery of rare earth elements

Abstract

We report the development of CA-BNMG-1 composite beads-cellulose acetate macrobeads embedded with nanosized copper imidazolate MOFs (BNMG-1) -engineered via nonsolvent-induced phase separation for the selective recovery of rare earth elements (REEs) from complex aqueous environments. This encapsulation strategy ensures uniform MOF dispersion, enhanced mechanical integrity, and minimized Cu(II) leaching (<1%), fulfilling the Safe and Sustainable by Design (SSbD) criteria. The CA matrix not only mitigates copper toxicity but also enables facile bead handling, recyclability, and scalable deployment in fixed-bed systems. Adsorption studies across a 10-REE standard solution and two simulated waste streams demonstrated significantly improved REE selectivity over pristine BNMG-1. Separation factors (SFs) for Yb(III) over Mn(II), Ni(II), and Na(I) reached 194.5, 325.8, and 339, respectively; Eu(III) showed SFs of 155.5, 260.5, and 271.2. The beads retained over 95% of their uptake capacity across multiple adsorption and single desorption cycles using mild acidic eluents, confirming excellent reusability and structural stability. This work advances a robust, low-toxicity, and scalable REE recovery platform that integrates adsorptive performance with environmental safety. CA-BNMG-1 beads offer a compelling alternative to solvent extraction, with potential for integration into circular economy strategies targeting REE recovery from e-waste, mine tailings, and industrial effluents-addressing both resource security and sustainability challenges.