Mineralogical Characterization and Flotation Properties of Rare-earth in Refractory Iron Tailings Subjected to Hydrogen-based Mineral Phase Transformation.

Hydrogen-based mineral phase transformation (HMPT) technology has proven effective in separating iron and enriching rare earths from Bayan Obo refractory ores. However, further investigation is required to understand the phase composition and floatability of rare earths after HMPT due to their phase changes. This study investigates the mineralogical characteristics and separation of rare earths from HMPT-treated iron tailings. Process mineralogy studies using BPMA and XRD analyses identified the main valuable minerals in the tailings, including rare earth oxides (9.15%), monazite (5.31%) and fluorite (23.52%). The study also discussed the effects of mineral liberation and intergrowth of gangue minerals on flotation performance. Flotation tests achieved an REO grade of 74.12% with a recovery of 34.17% in open circuit flotation, while closed circuit flotation yielded an REO grade of 60.27% with a recovery of 73%. TEM and SEM-EDS results indicated that while monazite remained stable during the HMPT process, bastnaesite was transformed into Ce7O12 and CeF3, which increased collector consumption. Despite this, the HMPT process did not significantly affect rare earths flotation. Fluorite enrichment in the tailings indicates further recovery potential. HMPT combined with magnetic separation and flotation provides an efficient method for the recovery of rare earths, iron and fluorite from Bayan Obo ores.