UBC Theses and Dissertations
Collector transfer between bubble and particle by collision Yan, Haixing
The adsorption densities of dodecylamine hydrochloride at the quartz-liquid interface and at the bubble-liquid interface were measured in separate experiments using the solution depletion method. The amount of amine removed from solution by gas bubbles was measured by bubbling nitrogen through amine solutions of known concentrations and measuring the amount of amine remaining in solution. The obtained results were compared with the amount of dodecylamine depleted from solution under flotation conditions when three phases (solid, liquid, and gas) were present in the tested system. By analyzing the distribution of amine between the interfaces it was possible to identify the conditions (pH and amine concentration) leading to a transfer of amine between bubbles and quartz as a result of bubble-particle collisions. Two modes of interaction between amine and quartz were identified. In a true solution system (pH 6), it was found the surfactant could be transferred from gas bubbles to quartz particles only when the adsorption density of amine at the quartz-solution interface was relatively low, thus leaving space for additional amine adsorption, and the bubbles and the particles were oppositely charged in the presence of amine. Too high adsorption density, resulting in positively charged particles and bubbles largely prevented the amine transfer process. In a colloidal dispersion of amine (pH 11), the dynamic conditions of the flotation test actually seemed to lead to a lower amount of amine transferred to the froth zone than the theoretical amount calculated from adsorption on quartz and on bubbles. This result was attributed to the weak adhesion of the precipitate to the quartz particles and the detachment of the precipitate from both bubbles and quartz particles as bubbles coalesced and burst in the froth zone. Interaction with quartz and bubbles was further weakened by the lack of electrostatic attraction between the nearly uncharged colloidal precipitate and the negatively charged bubbles and particles. Experimental results supports the bubble transfer hypothesis (Digre and Sandvik, 1968) stating that under flotation conditions the adsorption of collector on solid surfaces is governed, to a large extent, by a transfer of collector from the gas-liquid interface to the solid surface.
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Attribution-NonCommercial-NoDerivatives 4.0 International