Targeted regulation and extraction mechanism of rare earth elements and thorium during the decomposition of rare earth concentrates

来源 ：Science Direct

Thorium management remains a critical challenge in the processing of Bayan Obo mixed rare earth concentrates because conventional high-temperature sulfuric acid roasting requires severe thermal conditions and tends to generate thorium-bearing radioactive residues. In this study, a phosphate-assisted low-temperature roasting-water leaching-sulfuric acid decomposition strategy was proposed to decouple rare earth element extraction from thorium recovery. The key innovation of this process is an immobilization-remobilization regulation route: thorium is first selectively fixed in the water-leaching residue as insoluble phosphate/pyrophosphate species during oxidative roasting and is subsequently converted into soluble sulfate for recovery through a second low-temperature acid decomposition step.