The reasons that the foaming agent can stabilize the the foam in the?flotation process: in the slurry, the foaming agent molecules will be absorbed on the gas - liquid interface with a certain orientation and the non-polar group heads toward the air, namely the inside of the bubble. The polar group heads toward the water and attracts water molecules. Therefore, the foaming agent molecules is possible to reduce the flow rate and evaporation speed of the aqueous layer of the bubble walls , thus preventing the rupture of the bubble wall. After the alignment of the foaming agent molecules in the bubble surface, when the contact and collision of two bubbles occur, there will be the two layers of foaming agent molecules and their polar group hydration layer in the middle, so the bubbles are difficult to mergers. The small bubbles are easily to be preserved and the small bubbles are more resistant to external vibration than large bubbles, having stronger stability. Another main reason that the foaming agent enables the stability of the bubbles is that the foaming agent enables the the surface of the bubble to have elasticity, just like the elastic rubber film.
When the bubble is subjected to vibration or external force, the bubble will be suddenly deformed, if the surface of the bubbles has no foaming agent molecules, it will cause the thinning and rupture of the bubble wall. However, when the bubble surface has the foaming agent molecules, the directional alignment of the foaming agent molecule will reduce the surface tension and the bubble is deformed by external force, the foam wall interface is also increased, which will reduce the molecular concentration of the foaming agent on the surface of the bubble layer. And the surface tension of the gas-liquid interface is significantly increased, the increase of the surface tension, on the one hand, is conducive to restrain the gas molecules inside the bubbles to rush out; on the other hand, it will make the bubble generate a large shrinkage force to overcome the external force that cause the rupture of the bubble. Therefore, the usage of the foaming agent in the flotation concentrator enables the stability of the bubble.
