Synergistic Impact of Turkey Red Oil and Sodium Oleate on the Separation of Dolomite from Apatite

Dolomite and apatite exhibit very similar surface chemical properties, while conventional fatty acid collectors show limited selectivity between them, making their efficient separation in phosphate rock flotation a persistent challenge. In this study, a mixed collector system (RF-25), composed mainly of sodium oleate (NaOL) and turkey red oil (TRO), was designed to enhance the separation of dolomite from apatite via reverse flotation. Micro-flotation experiments indicated that the optimal separation performance was obtained at pH 5, with an H 3 PO 4 concentration of 8 × 10 –4 mol L –1 and a NaOL:TRO ratio of 4:1. Under these conditions, when the collector concentration was 60 mg L –1, the recovery rates of dolomite and apatite differed by 90.09 percentage points. The results of mixed-mineral flotation further demonstrated the effectiveness of RF-25, where P 2 O 5 recovery reached 95.71% while MgO recovery was reduced to 19.79%. Surface characterization analyses provided insight into the improved selectivity mechanism. TOC and contact angle measurements showed that RF-25 preferentially adsorbed onto dolomite, significantly increasing its surface hydrophobicity compared with that of apatite. FTIR and XPS results further confirmed that a more continuous and complete adsorption layer formed on the dolomite surface, whereas only weak adsorption occurred on apatite. Zeta potential measurements were consistent with these findings, indicating a more pronounced surface modification of dolomite after treatment with RF-25. Overall, the mixed collector enhanced the difference in interfacial properties between dolomite and apatite, thereby improving flotation selectivity. This work demonstrated that RF-25 provided an effective strategy for the selective removal of Mg-bearing gangue minerals in phosphate rock flotation.