Enhancing quartz-amine flotation with oily bubbles

Oily bubble flotation is an improved flotation method that uses air bubbles covered with a thin film of oil. This method increases the hydrophobicity and inertia of the bubbles while reducing the probability of particle detachment from the bubbles. However, the studies on the oily bubble flotation of materials containing naturally hydrophilic minerals are quite limited in the literature. Furthermore, fundamental studies demonstrating the effect of oils on bubble-particle and bubble-bubble interactions in the presence of frothers and ionic collectors are crucial for revealing the synergistic effects of these reagents and thus maximizing the flotation performance. Therefore, this study focuses on investigating the effect of oily bubbles on the quartz-amine flotation. For this purpose, micro-flotation experiments, measurements of bubble-particle attachment time, and bubble coalescence time were carried out. Background In flotation, selectively rendered hydrophobic minerals attach to the bubbles and are separated from hydrophilic minerals. The flotation behavior of a single mineral is commonly investigated by micro-flotation (MF) experiments. In flotation, hydrophobic particles should attach to bubbles within a limited bubble-particle attachment time (BPAT). The particle’s floatability increases with decreasing BPAT. If two bubbles collide and remain in contact for a certain bubble coalescence time (BCT), they coalesce. This is detrimental to bubble-particle interaction; thus, efforts are being made to increase the BCT. Methodology The MF and BPAT experiments were conducted with analytical-grade quartz at 212 × 38 μm (99.4 percent SiO2, Merck, USA). Dodecyl amine hydrochloride (DAH) (98 percent CH3(CH2)11NH2·HCl, TCI, Japan) and methyl isobutyl carbinol (MIBC) (98 percent (CH3)2CHCH2CH(OH)CH3, Merck, USA) were used as a collector and frother, respectively. Meanwhile, the oily bubbles were generated using pure kerosene (Sigma-Aldrich, USA). The MF experiments were performed using a 200-cm3 MF cell with a frit pore size of 10 to 16 μm in the presence of 10 ppm MIBC at a 50 cm3/min nitrogen (N2) flow rate and at a natural pH of approximately 6.0 for two minutes. In the oily bubble flotation experiments, the oily bubbles were generated by passing the N2 gas through a kerosene emulsion, prepared by ultrasonic emulsification (100 cm3, 20 kHz, 150 W, 1 min) (HD 3200, Bandelin, Germany), placed in a chamber located beneath the frit. For the BPAT measurements, a small amount of the DAH-conditioned suspension was transferred to the measurement cell of the induction timer (BKT-100, Bratton Engineering, Littleton, MA, USA) to form a particle bed. The bubble (2 mm), formed at the end of the capillary tube of the device, was brought into contact with the particle bed for a predetermined contact time (1 to 1,000 ms) and then detached. The particles were observed to attach to the bubble surface. The probability of bubble-particle attachment was calculated using 20 measurements taken under each condition, and the BPAT time was defined as the time when 50 percent attachment occurred. In the experiments with oily bubbles, quartz particles were dispersed in the presence of kerosene emulsion conditioned with DAH before the BPAT measurements. For this purpose, BCT measurements were performed using a modified version of the induction timer. A glass cell containing a capillary glass tube filled with the relevant reagent solution was placed under the capillary glass tube of the device. Two opposing bubbles were formed at the ends of each glass tube, and the upper tube moved downwards to ensure that the bubbles remained in contact for the adjusted contact time. The measurements taken at various reagent concentrations and contact times revealed the bubble coalescence, and the time at which 50 percent coalescence occurred was defined as BCT. Fig. 1 (a) Flotation recovery, (b) bubble-particle attachment probability of quartzand (c-d) bubble coalescence probability at the given conditions. Results and discussion Figure 1a shows that the flotation recovery increased with kerosene concentration and reached a plateau at 100 ppm kerosene. In oily bubble flotation, kerosene molecules surrounding the oily bubbles bind to the hydrocarbon tails of the DAH molecules on the particle surface, increasing the particle collection efficiency of the bubbles, and thus the flotation efficiency (Fig 1a). At high DAH concentrations, quartz is highly hydrophobic, and the positive effect of kerosene on flotation is less. As shown in Fig. 1b, in the presence of oily bubbles, the probability of bubble-particle attachment increased significantly with kerosene concentration. As the three-phase contact line spreads faster on the particle surface in the presence of oil compared to air, bubble-particle attachment occurs more rapidly in the presence of oily bubbles than in conventional bubbles. The BCT measurement results in Fig. 1c showed that at 1.0 × 10−5 mol/dm3 DAH concentration, where bubble coalescence was completely inhibited, the BCT decreased to 3 ms when 100 ppm kerosene was added. Meanwhile, MIBC was much more effective in inhibiting bubble coalescence. When 100 ppm kerosene was added to a 10 ppm MIBC solution, where bubble coalescence was completely inhibited, the BCT was 750 ms, as seen in Fig. 1d. Conclusions Quartz-amine flotation can be improved by oily bubble flotation depending on kerosene concentration. Quartz particles attached faster to oily bubbles than to conventional bubbles. Oily bubbles were more prone to coalescence than conventional bubbles. The synergetic effect between kerosene and other flotation reagents should be considered, and reagent concentrations should be optimized for successful flotation. Funding This work was supported by the Scientific Research Projects Coordination Unit of Istanbul University – Cerrahpasa, grant number FYL-2022-36821. Open-access funding for the full-text paper was provided by the Scientific and Technological Research Council of Türkiye (TÜBITAK). References A list of all references is available in the full paper.

Enhancing quartz-amine flotation with oily bubbles

Authored by: Sercan Erbas, Can Gungoren, Saleban Mohamed Muse, Mert Terzi, Ismail Demir, Ilgin Kursun and Orhan Ozdemir

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