Qiming Zhuo,Wenli Liu,Hongxiang Xu,He Zhang,Xiaopeng Sun
Attachment behavior is a key component of flotation and has a decisive influence on flotation performance, and the experiment research on the attachment between mineral particles and bubbles still needs further research. In this work, a particle–bubble attachment apparatus and multiple target tracking software were developed. Coal particles were used as the subjects, and the effect of particle properties on the attachment performance was studied from the perspective of the particle group. The particle–bubble attachment experiments indicated that the collision position had an effect on the attachment efficiency, and the attachment efficiency decreased with an increase in the collision angle. The efficiency-weighted attachment angle was proposed to quantitatively describe the attachment performance of coal samples. The efficiency-weighted attachment angle of low-density coal samples was greater than that of high-density coal samples. For particles with different sizes, the efficiency-weighted attachment angle of fine particles was greater than that of coarse particles. Furthermore, SDS weakened the attachment performance between coal particles and bubbles via adsorption on the bubble, and the efficiency-weighted attachment angle decreased as the concentration of the SDS solution increased. CTAB adsorbed on coal particles and bubbles, and the efficiency-weighted attachment angle first increased and then decreased with increasing CTAB concentration.
Surfactant plays a vital role in flotation, especially in the adsorption of particle and bubble surface. From macroscopic to atomic scales, the effects of surfactant on the attachment between coal particles and bubbles were investigated by the induction time measurements, bubble-particle wrap angle measurements, thin liquid films measurements and molecular dynamics (MD) simulation. The three surfactants are Cetyltrimethylammonium bromide (CTAB), Sodium dodecylbenzene sulfonate (SDBS), and Methyl isobutyl carbinol (MIBC). Macroscopically, the coal particles could be more easily attached to a bubble surface in three solutions, particularly in CTAB solution. This was because the speed of thinning and rupture of thin liquid film between coal-particles and bubbles was faster in CTAB solution than that in other solutions. MD simulation findings show that the adsorption of CTAB significantly improves the water molecule migration rate. In addition, the CTAB promotes the attachment efficiency in floatation.
Frothers not only modify gas–liquid interfacial properties, but also alter coal particle surface properties, thereby influencing bubble–coal particle interactions in froth flotation processes. While previous studies have focused on frothers’ effects on gas-liquid interfaces, their impact on coal surface hydrophilicity and coal-bubble interactions remains underexplored. In this study, we measured the bubble–coal interactions using an anthracite coal sample under varying concentrations of MIBC and DF250 frothers during attachment and detachment processes of coal, in combination with surface tension measurement, XPS, FTIR, contact angle measurements, and quantum chemistry calculations. The results demonstrate that both MIBC and DF250 will adsorb on the coal surface and impart hydrophilicity onto it. Increasing frother concentration will render the coal surface more hydrophilic, which will prolong liquid drainage time (t drain ) and enhance the attachment repulsive force (F adr ) during bubble–coal particle attachment. At the same time, this also will decrease the detachment attraction force (F det ) of coal particle. In the examined concentration range, DF250 exhibits more pronounced effects than MIBC, meaning that it is less suitable for coal flotation. For both frothers and in the studied concentration range, F adr consistently exceeds F det , meaning that immediately removal of coal-bubble aggregates from the mixing zone of flotation cell seems to be desirable. In addition, regardless of the presence or absence of frother in water and the structure difference in MIBC and DF250, the contact angle of coal surface should be a good indicator of the strength of coal-bubble interactions.
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