Phosphate-Functionalized Zero-Valent Iron for Efficient Separation of Europium from Acidic Associated Mineral Wastewater

The hydrometallurgical processing of associated radioactive minerals inevitably produces acidic wastewater containing europium (Eu ³⁺ ), a critical rare-earth element whose co-occurrence with radionuclides complicates separation and recovery. Here, a zero-acid separation strategy is developed using phosphorylation-engineered zero-valent iron (P–ZVI _bm ), which integrates corrosion resistance with selective coordination reactivity. Phosphate functionalization transforms Fe ⁰ surfaces into chemically stable Fe–O–P frameworks, creating multidentate active sites that drive inner-sphere Eu ³⁺ complexation and interfacial Eu–phosphate precipitation. Combined experimental and DFT analyses reveal that the Fe–O–P interface facilitates strong chemisorption through hybrid Eu–O–P bonding (E _ad up to − 14.7 eV) and electron transfer between Eu 4f/5d and O 2p orbitals, while suppressing Fe⁰ dissolution. In real mine wastewater containing multiple rare-earth and transition metal ions, P–ZVI _bm achieves high Eu ³ ⁺ selectivity, stability, and recyclability, maintaining over 85.0% removal efficiency after H ₃ PO ₄ cycles. This study establishes a zero-acid, phosphate-mediated adsorption–precipitation mechanism for rare-earth recovery, offering a scalable route for sustainable treatment and valorization of radioactive metallurgical effluents within green process metallurgy.