The air bubbles generated in the flotation cell are stabilized by the use of surfactants called frothers. It is widely known that the froth is very important to the flotation process, particularly with respect to the size of bubbles and its stability as well as mobility of foam phase; these factors are crucial for the kinetic viability of the process, for the global recovery and for the concentrate grade. Usually, the conventional flotation surfactants are synthetic and have some environmental issues. Thus, there is an increased interest in using the more environmentally friendly bioreagents. It is also known that some microorganisms are able to produce surface-active compounds. The bacteria Rhodococcus opacus in their cellular walls produce a range of proteins and polysaccharides, that by specific procedures can be removed forming bioreagents with characteristics as surfactant that are similar to synthetic reagents used in flotation. These biosurfactants have several advantages over conventional reagents, such as low toxicity and greater compatibility with the environment, biodegradability, and effectiveness in a wide range of temperature and pH. This paper shows a study of the characteristics of flotation froths using biosurfactants produced by the Rhodococcus opacus bacteria and their metabolic by-products, compared to the conventional frothers that are used in mineral flotation. The results look promising because the products that acted as biofrother show the potential to lower the surface tension (down to 48 mN/m) and to produce a large quantity of with small bubbles (1.3 mm Sauter Diameter).
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