Selective depression of pyrochlore and barite using GG/TA combined depressant: Flotation mechanisms and molecular insights

Abstract

This study presents the first investigation into the application of a combined depressant, Gellan gum (GG)/tannic acid (TA), for the selective flotation separation of pyrochlore and barite, using CaCl₂ as an activator and NaOl as a collector. Micro-flotation experiments demonstrated that GG/TA at a 1:1 ratio effectively depressed pyrochlore flotation while maintaining high barite recovery, achieving a pyrochlore recovery of only 0.2 % at a dosage of 6 mg/L. The competitive adsorption mechanism was elucidated through contact angle measurements, zeta potential analysis, Fourier-transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The results revealed that GG/TA preferentially chemo-synergistic adsorbed onto pyrochlore active sites, forming a hydrophilic barrier that impeded NaOl attachment and thus suppressed flotation. In contrast, GG/TA showed minimal physical adsorption on the barite surface, facilitating NaOl adsorption on barite, thereby promoting its hydrophobicity and enhancing flotation selectivity. XPS analysis further identified GG/TA adsorption primarily at Nb and O sites on pyrochlore, whereas adsorption on barite occurred weakly at Ba and O sites. Additionally, frontier molecular orbital (FMO) theory analysis indicated that the functional groups of GG and TA interact with mineral surfaces, influencing their depression behavior. Based on these findings, an adsorption model for the GG/TA depressant in pyrochlore-barite separation was proposed.