Biomimetic Phosphatization of Nano Zero-Valent Iron for Thorium Removal and Waste Remediation from Rare Earth Leachates

Abstract

The selective removal of thorium (Th) from rare earth element (REE)-associated mineral leachates is essential for improving REE utilization and mitigating radioactive hazards. However, high concentrations of competing metal ions and the lack of environmentally friendly separation strategies make Th(IV) recovery challenging. Here, we report a biomimetic phosphatization approach using nano zero-valent iron (ZVIbm) and phosphoric acid to construct phosphate-coordinated surfaces for selective Th immobilization. Density functional theory (DFT) calculations reveal that phosphate-induced surface reconstruction enhances Th adsorption through multi-centered Fe-O-P and Th-O-P coordination, enabling charge redistribution and metal ion selectivity. Batch experiments using acidic leachates containing 48.8 mg/L Th(IV) demonstrate over 98.8% recovery efficiency at a low dosage of 0.3 g/L, reaching 99.7% within 3.0 hours. This study provides a green and effective strategy for actinide separation via surface coordination and mineralization chemistry, offering promise for radioactive waste remediation and resource recovery.

Keywords: Radioactive waste remediation, Thorium removal, Biomimetic phosphatization, Rare earth leachates, nZVI