Flotation Behavior of Different Colored Fluorites Using Sodium Oleate as a Collector

Using sodium oleate (NaOL) as a collector, the flotation characteristics of natural colorless fluorite (CF), green fluorite (GF), and purple fluorite (PF) were investigated through micro-flotation tests, collector adsorption measurements, and surface tension measurement. The micro-flotation results indicated that CF had a much better flotation response than both GF and PF, and had higher floatation recovery. The results demonstrated a considerable discrepancy in the interfacial properties between colorless and colored fluorite, even though all the samples were obtained from the same deposit, holding a similar high purity of CaF2. The adsorption capacity of CF, GF, and PF for NaOL was 2.27, 4.18, and 8.21 × 10−6 mol/g under neutral conditions, respectively. Fourier transform infrared (FT-IR) measurements revealed that the carboxyl groups of NaOL reacted with Ca sites on the surface of fluorites by chemical adsorption. From the zeta potential analyses, PF exhibited a lower positive potential than CF and GF, mainly due to its surface carbonation. In the presence of NaOL, the surface potential of fluorites changed from positive to negative because the NaOL collector had been adsorbed onto the mineral surface and changed their surface potential, which was consistent with the flotation results at different pH values. We found that the floatability of the fluorite samples was influenced by their surface roughness, measured by an atomic force microscope (AFM) and scanning electron microscope (SEM). PF can be floated with adding more reagent dosage than CF and GF to compensate for its higher surface roughness