Frothers and Flotation Froth

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Abstract
Good flotation frothers have branched hydrocarbon radicals and form loosely packed gaseous films at the liquid/gas interface. Their hydrophile-lipophile properties must be properly balanced and for most good frothers the HLB values are close to 6. This allows them to co-operate actively with the adsorbed collector in the moment of particle-to-bubble attachment. Increasing molecular weight at roughly the same HLB values makes frothers more powerful while those with lower molecular weight are more selective. Frothers are known to reduce the induction time and hence make the flotation process more kinctically favourable. This attachment process is now seen as one of the important mass transfer processes that determine flotation kinetics. The other two mechanisms, non-selective mechanical entrainmcnl and dropback from the froth to the slurry depend critically on the properties of the frother and froth stability in mechanical cells. In flotation columns, these two other mechanisms are not so important since the froth stability in this latter case is mostly determined by wash water.