Recovering Rare Earth Elements from Mining Effluent via Synergistic Angstrom-Scale Confinement and Phosphate-Mediated Coordination in MXene Membranes

Abstract Recovering rare earth elements (REEs) from complex aqueous streams is essential for advancing sustainable resource recovery but remains hindered by low REE concentrations and strong competition with impurity ions. Herein, we introduce a biomimetic MXene membrane that integrates phosphate-based molecular recognition with angstrom-level control of interlayer spacing to achieve the selective and continuous recovery of REEs from wastewaters. By intercalating aminophosphonic molecules within Ti3C2Tx layers, the membrane precisely tunes the nanochannel size and establishes coordinatively active oxygen sites that preferentially bind trivalent lanthanides under nanoconfinement. Such a design enables a synergistic mechanism in which steric exclusion and ligand–metal coordination coregulate ion transport, leading to markedly improved selectivity toward REE recovery. The optimized 2-AEP-M membrane exhibited a Ca2+/Dy3+ selectivity of 243.47 in simulated solutions and 130.69 in actual REE mining wastewater. After membrane separation and subsequent precipitation and calcination, REEs constituted 90.2% of the quantified cationic species in the recovered solid products. Experimental and computational analyses reveal that phosphate groups promote Dy3+ coordination, underpinning the observed ion discrimination. The membrane also demonstrates antiswelling stability and antibacterial properties, supporting its potential for long-term deployment. This work integrates chemical affinity with angstrom-confined transport, offering a platform for precise ion separation and sustainable REE recovery.