Studies on the Enrichment Feasibility of Rare Earth-Bearing Minerals in Mine Tailings

Abstract

This study aimed to investigate the potential of enrichment of rare-earth-bearing minerals in historic mine tailing using the froth flotation process. Characterization studies indicated that tailings contained 11,000 ppm of rare earth elements (REEs). The major mineral in the tailings was apatite at ~84%, which was associated with iron oxides (~16%). TESCAN’s integrated mineral analysis (TIMA) showed that monazite was the main REE mineral, and 69% of monazite was locked in apatite grains. Characterization studies suggested that the separation of REEs-bearing apatite from iron oxides is possible using froth flotation, wherein apatite was floated and iron oxides were depressed. Zeta potential experiments were conducted to understand the behavior of the main minerals in the feed when selected depressants of iron oxides were added. Depressants included corn starch, sodium metasilicates, polyacrylamide (PAM), hybrid polyacrylamide (HyPAM), and chitosan. Zeta potential results suggested that chitosan and polyacrylamide-based polymers had the strongest adsorption on magnetite at pH 7 and pH 9, respectively, as indicated by the large shift in the zeta potential of magnetite suspensions. Flotation results were consistent with zeta potential findings and showed that Hy-PAM and chitosan had the best depression efficiency of iron oxides at pH 9 and pH 7, respectively.