Flotation reagents-fronther and modifiers

In flotation beneficiation plant, main euipments are important such as ball mill, flotation machine, crushing machine etc. And the flotation reagents are also important for flotation process, the reagents used in flotation are usually divided into three classes:
Collectors: organic chemicals which make the surface hydrophobic and hence the mineral is capable of being collected in the process.
Frothers: organic chemicals which reduce the surface tension of the water to stabilize the bubbles into a froth layer at the top of the flotation cell to make concentrate removal easier.
Modifiers: organic or inorganic chemicals used to modify the slurry conditions to enhance the difference in surface chemistry between the valuable and gangue minerals.
Let’s introduce frothers and modifiers in this article
Frothers
Frothers are surfactants, usually organic heteropolar compounds such as alcohols or
polyglycol ethers. Due to the heteropolar nature, the frother adsorbs at the air/water interface and as a result, lowers the water surface tension. This has the effect of producing smaller bubbles and more importantly it stabilises the froth when it reaches the top of the slurry. If the bubbles burst when they reach the air/water surface then any minerals they carry will drop back into the slurry forming a scum at the surface. The prime role of the frother is to stabilise the froth formed at the interface long enough for the concentrate to be removed from the flotation machine. Once removed from the cell, the froth must break to allow the mineral particles to be re-pulped for further processing.
The effect of frother concentration on the surface tension of water is an initial rapid drop in
surface tension before leveling out to a constant minimum value. The optimum frother
concentration is not the amount which gives the minimum surface tension but in the region
where the surface tension is capable of rapid change with concentration. This is the region of greatest froth stability.
When the thin liquid film at the bubble wall experiences an external stress and stretches
locally, the increase in surface area produces a local decrease in surfactant concentration. This in turn increases the surface tension momentarily to allow the thin film to recover without rupturing. If there is no change in surface tension with local film thinning, for example if the liquid is pure or the frother concentration is in excess then the froth will be unstable. For excess frother concentration, all that will happen is the formation of very small bubbles which burst on reaching the pulp surface.
Frothers commonly used include natural chemicals like pine oil, cresylie acid and synthetic reagents such as methyl isabutyl carbinol (MIBC) and polyglycol ethers. Ideally frothers should possess little or no collecting properties and vice versa so that both functions can be controlled separately.
Modifiers
This class of reagents covers all chemicals whose principal function is neither collecting nor frothing. These may be further divided into depressants, activators and pHregulators.
A depressant is any chemical which inhibits or prevents the adsorption of a collector by a
mineral particle and thereby prevents its flotation. An activator prepares the mineral surface to enhance the adsorption of the collector. pH regulators adjust the pulp pH to give optimum performance for a particular reagent and mineral ore. The common pH regulators are lime, soda ash and sulphuric acid.
Other reagents that may be used in specific cases include dispersants for removing clay
slimes from mineral surfaces sxAprecipitants for removing interfering ions from solution.
The main use of these modifying agents is in the differential flotation of a mixed ore. That
is the successive removal of two or more valuable minerals from each other by flotation. For example the separation of each copper, lead, zinc and iron sulphides from a single ore is selective flotation whereas the flotation of the combined sulphides from the gangue is referred to as bulk flotation.
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Sinoninetechnology team

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