## 3 Results
### Interaction Mechanisms of Collector and Depressants on Fluorite Flotation  
In this paper, the flotation of fluorite, calcite, and quartz and their separation using different depressants and oleic acid as the collector have been studied. The best results were obtained using a mixture of quebracho tree and dextrin white as depressants. To explain the results, a review of the investigations carried out by other authors on fluorite flotation has been conducted. The mechanism of interaction of the collector as the fatty acid in salt-type minerals and the conditions used in their flotation have been widely studied for a long time [5; 36; 37; 38]. Most of these authors agree that the mechanism of interaction of the reagents with the mineral in the flotation process is very complex. The adsorption of the collectors and depressants in the mineral is generally considered to be affected by the pH of the flotation system, which determines the charge on the surface of the particle and, therefore, the type of interaction. In general, coulombic attraction, physical adsorption, chemisorption, and surface precipitation have been suggested as possible mechanisms. However, there is no clear understanding of the interaction of reagents with the mineral, and the results shown by different investigations differ significantly depending on the origin of the minerals [39]. Figure 3: CaCO\({}_{3}\) + MgO\({}_{3}\) (%) on concentrate for cell and column as pH function and type of depressant. More recently, [PERSON] [40] performed a review on the interaction of oleate with non-sulfide minerals using zeta potential. This author concluded that although there are differences of opinion on the actual interaction mechanism, it is accepted that the presence of oleate species causes a reduction in zeta potential and that the suggested mechanisms include chemisorption of various oleate species in solution (oleate anions, ionic dimers or acid-soap complex) in conjunction with physical adsorption, presence of undissociated oleic acid, precipitation of oleate salts, or formation of oleate colloids on the mineral surface. In addition, oleate adsorption could occur through the formation of one or more layers on the mineral surface. [PERSON] and [PERSON] [37] already indicated in their work as a mechanism for adsorption of oleate on fluorite and calcite, the monolayer coverage in the case of calcite and the formation of bilayer in the case of fluorite, followed by a precipitation of calcium soap. [PERSON] et al. [41] study the separation mechanism of fluorite and calcite with oleic acid and conclude that the results of the zeta potential confirm that the chemical adsorption of the collector on the mineral surface provides  
Figure 4: SiO\({}_{2}\) (%) on concentrate for cell and column as pH function and type of depressant. a good recovery of fluorite when the pH is close to 10 and that calcium and oleate ions in the mineral surface react form calcium oleate. Other researchers studied the zeta potential of fluorite as a function of pH in the absence and presence of a collector [4; 6; 42; 43; 4]. At low pH values, a constant positive zeta potential of approximately 20-30 mV was observed. At pH 7, the zeta potential began to decrease, reaching zero at pH values between 7.5 and 8.5. Above pH 8.5, the zeta potential increased in negative value as the pH was increased. The addition of sodium oleate caused the zeta potential of the fluorite to become more negative at the same pH compared to that observed without addition of sodium oleate. The isoelectric point also shifted to lower pH values with an increase in oleate concentration, showing a greater affinity of oleate for the fluorite surface. On the other hand, [PERSON] et al. [44] studied the selective adsorption of tannic acid in calcite and its implication as a depressant in the separation of fluorite using sodium oleate as the collector.