Abstract
Along with the accompanying theory article, we experimentally investigate the effect of the depletion attraction force on the flotation of malachite. While varying the concentration of the depletion agent (polyethylene glycol), three different systems are studied: pure malachite, pure silica and a 1:1 mass ratio of malachite and silica binary system. We find that the recovery increases significantly as the concentration of the depletion reagents increases for all three systems. However, the recovery suddenly decreases in a certain concentration range, which corresponds to the onset of the decreased surface tension when high concentrations of the depletion agent are used. The decreased surface tension of the air/water interface suggests that the recovery rate is lowered due to the adsorption of the depletion agent to the bubble surface, acting as a polymer brush. We also perform experiments in the presence of a small amount of a collector, sodium oleate. An extremely small amount of the collector (10−10–10−5 M) leads to the increase in the overall recovery, which eventually reaches nearly 100 percent. Nevertheless, the grade worsens as the depletant provides the force to silica particles as well as target malachite particles.
Highlights
In the field of mineral processing, froth flotation has been the most widely used technique to improve the quality of low-grade minerals [1,2,3,4,5,6]
We study the effect of depletion attraction on the flotation of malachite in the presence of low concentrations of sodium oleate
Malachite shows higher floatability than silica over all concentrations of polyethylene glycol (PEG); this results from the differences in an electrostatic force of malachite and silica to the bubble because identical depletion force is expected to be present for both minerals at the same PEG concentration [1]
Summary
In the field of mineral processing, froth flotation has been the most widely used technique to improve the quality of low-grade minerals [1,2,3,4,5,6] During this process, a collector is used to impart hydrophobicity to desired mineral particles; these hydrophobic particles are better attached onto the surface of a bubble, leaving undesired particles in the bulk solution. Several groups have attempted to find environmentally friendly collectors [14,15,16,17,18,19]. In this regard, collector-less flotation would be the best option if shown to be feasible. Several groups have investigated the flotation behavior of sulfide minerals without collectors (e.g., galena (PbS), pyrite (FeS2 ), arsenopyrite
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