Differentiated regulation of mineral interface properties using an eco-friendly polysaccharide depressant for enhanced apatite–dolomite sustainable flotation separation

Abstract

Apatite (Apa) and dolomite (Dol) exhibit convergent interfacial properties, making it difficult to separate them using fatty acid-based flotation collectors alone. In this study, psyllium gum (PG) served as an effective Dol depressant to achieve efficient recovery of Apa, and its selective sorption mechanism was uncovered. Flotation results indicated that in a sodium oleate (NaOl) system, PG has a strong depression effect on Dol but has almost no effect on Apa, which significantly widened the flotation difference between the two. The results of surface property analysis confirmed that there was a strong sorption interaction between PG and Dol, which hindered sorption of NaOl on Dol and markedly weakened Dol's hydrophobicity, whereas the opposite occurred for Apa. The results of spectral analysis further demonstrated that the presence of strong interactions between PG and metal sites (i.e., Mg and Ca) on Dol enhanced its adsorption on the Dol surface compared to that on Apa. EDLVO calculations affirmed that PG increased the electrostatic repulsion of Dol with bubbles and weakened the hydrophobic attraction between them, thereby reducing Dol's adhesion to the bubble surface and suppressing Dol flotation. As a result, PG realized satisfactory separation of Apa and Dol, with 85.74% of Apa being recovered and 86.40% of Dol being removed. Based on these findings, PG can serve as a highly selective flotation depressant for the sustainable clean processing of low-grade phosphate ores to produce phosphate fertilizers.