New insights into synergistic mechanism of oleic acid-kerosene in enhancing hydrophobic agglomeration of fine rhodochrosite

Enhanced flotation of rhodochrosite fines via hydrophobic agglomeration offers a viable strategy for utilizing manganese carbonate ores and minimizing electrolytic manganese residue. Understanding the mechanism of hydrophobic modifiers is essential for controlling agglomeration behavior. This study investigated the synergistic effect of oleic acid (OA) and kerosene in enhancing rhodochrosite agglomeration through analysis of agglomerates properties, interfacial wettability, adsorption behavior, and interaction forces. The results show that kerosene alone exhibits negligible agglomeration effects on rhodochrosite at a lower concentration of 0.03 wt%, due to the weak adhesion and easy detachment of oil droplets on particles under shear. As kerosene increases to 0.3 wt%, coverage of oil droplets on rhodochrosite increases. However, the limited deformability and the greater critical coalescence force of oil droplets in aqueous solution result in weak agglomeration. Interestingly, agglomerates become larger and more compact with addition of OA-emulsified kerosene, mainly attributed to the dual significant enhancement of rhodochrosite hydrophobicity and bridging effect of oil droplets between particles. Hydrophobic association between OA nonpolar tail and kerosene, along with the strong adsorption of its polar head onto rhodochrosite, results in the improved deformability and spreading of oil droplets, further enhancing rhodochrosite hydrophobicity. Furthermore, changes in OA concentration at the oil–water interface during collision cause tension gradient, inducing stable oil bridges at lower critical coalescence forces. As a result, the co-effect of OA and kerosene enhances rhodochrosite agglomeration. This study offers fundamental insights into the synergistic mechanism of OA and kerosene in promoting the agglomeration of rhodochrosite and other fine particles.