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EN
The purpose of this study is to explore the collision–attachment law of lepidolite, feldspar and quartz during their interaction with bubbles by particle settlement method and bubble rising method under the action of combined collector. In this study, HQ-330 and dodecylamine were used as combined collector to separate lepidolite, feldspar and quartz by flotation. It also aims to analyse the relationship between collision probability, attachment probability, formation time of three-phase contact line and flotation recovery and the main factors affecting the formation time of three-phase contact line. Experimental results show that when the pH is 7 and the combined collector dosage is 100 mg/L, the separation of lepidolite from feldspar and quartz can be achieved. In the particle settlement experiments, the correlation between collision probability and flotation recovery is low, the correlation between attachment probability and flotation recovery is positive. In the bubble rising experiments, the formation time of three-phase contact line (tTPC) is negatively correlated with flotation recovery, and the combined collector changes tTPC by changing drainage time.
EN
This work is focused on the detailed experimental study of bubble adhesion on a hydrophobic solid surface. The frame rate 16000 fps was used in side view arrangement in order to capture in detail the three-phase contact line expansion and bubble shape changes. Experiments were done in pure water and in solutions of the anionic surfactant sodium dodecyl sulphate in low, medium and high concentrations. It was found out that the rupture of a liquid film is not symmetrical with respect to the vertical axis of the bubble symmetry. This asymmetry of TPC line formation leads to bubble surface oscillations and asymmetry in dynamic contact angles. These dynamic mechanisms are diminished with increasing surfactant concentration. The non-linearity of expansion velocity was also observed. In the case of high bubble surface mobility, the expansion velocity first decreases and after few milliseconds, the second velocity maximum emerges caused by kinetic energy dissipation. In surfactant solutions, the arising Marangoni stresses should be taken into account because the expansion velocity increases in the first moments of TPC line expansion. Existing models, such as hydrodynamic and molecular-kinetic, are not able to incorporate with bubble oscillations in pure liquids as well as the non-monotonic curve of expansion velocity profile in surfactant solutions.
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