Frothing agents

Schaum-bestflndigkeit, /. foam-holding capacity. -bier, n. foaming beer, -bildner, m. frothing agent, foamer. -bildtmg. /. formation of foam or froth, -blaae, /. bubble, -brecher, m. foam breaker, froth killer, schaumen, v.i. froth, foam (of wine, etc.) sparkle, fizz (of soap) lather. — v.t. skim, scum. 

Flux blankets may be made from zinc ammonium chloride or from ammonium chloride plus frothing agents such as glycerin, tallow or sawdust. These thicken the blanket and lower the surface temperature thus reducing the volatilisation losses of ammonium chloride and the amount of fume which is generated. 

Froth-flotation processes are used extensively for the separation of finely divided solids. Separation depends on differences in the surface properties of the materials. The particles are suspended in an aerated liquid (usually water), and air bubbles adhere preferentially to the particles of one component and bring them to the surface. Frothing agents are used so that the separated material is held on the surface as a froth and can be removed. 

Frothing Agents are intended to stabilize the particle (mineral)-air mixture (foam) at the surface of the flotation tank. Alkyl or amyl alcohols in the C5 to C12 range are typical frothers. They lower ysv which is beneficial to the stability of the foam to some extent collectors and frothers may counteract in their effects so that compromise conditions must be selected. 

The separation of a mixture using flotation methods depends on differences in the surface properties of the materials involved. If the mixture is suspended in an aerated liquid, the gas bubbles will tend to adhere preferentially to one of the constituents-the one which is more difficult to wet by the liquid-and its effective density may be reduced to such an extent that it will rise to the surface. If a suitable frothing agent is added to the liquid, the particles are held in the surface by means of the froth until they can be discharged over a weir. Froth flotation is widely used in the metallurgical industries where, in general, the ore is difficult to wet and the residual earth is readily wetted. Both the theory and practical application of froth flotation are discussed by Clarke and Wilson 44. ... 

A continuous drip of a small amount of diesel oil (typically less than 1 ml/minute) into the oxidation tank solution aids in separation of sulfur into die froth, as well as producing a thick, easy to remove froth. Sometimes diesel oil addition leads to over-frothing, however, and silicone or ocenal must be added as anti-frothing agents. 

FLOTATION. A method of separating minerals from waste rock nr solids of different kinds by agitating the pulverized mixture of solids with water, oil. and special chemicals that cause preferential welling of solid panicles of certain types by the oil. while other kinds are not wet. The unwelled particles arc carried to the surface by the air bubbles and thus separated from the wetted particles A frothing agent is also used to stabilize the bubbles In Ihe form of a froth that can be easily separated from the body of the liquid (froth flotation). Do not confuse with floatation. 

The principal source of zinc is zinc sulfide or zinc blende. This ore occurs mainly in Australia, Canada and the US. The zinc ore is first concentrated by a process called froth flotation. The crushed ore is fed into tanks of water containing a chemical frothing agent. Air is blown through so that the whole mixture froths up. The rock particles become soaked with water and sink to the bottom of the tank. However, the zinc sulfide particles, into which the water cannot soak, are carried to the top of the tank by the air bubbles and are skimmed off and dried. This ore now contains 55-75% of zinc sulfide. The zinc sulfide is then heated very strongly in a current of air in a furnace (Figure 10.16) to convert it to the oxide ... 

The wetting properties of the particles play a crucial role in flotation. We have already discussed the equilibrium position of a particle in the water-air interface (Section 7.2.2). The higher the contact angle the more stably a particle is attached to the bubble (Eq. 7.19) and the more likely it will be incorporated into the froth. Some minerals naturally have a hydrophobic surface and thus a high flotation efficiency. For other minerals surfactants are used to improve the separation. These are called collectors, which adsorb selectively on the mineral and render its surface hydrophobic. Activators support the collectors. Depressants reduce the collector s effect. Frothing agents increase the stability of the foam. 

To fight fire, use foam, CO2, dry chemical. Used as an odorant, disinfectant, solvent, wetting agent, and frothing agent. 

Frothing agent for adhesives based on natural latex, to be used in fabric/fabric lamination (shoe material). 

Frothing agent for dispersions, allows minimal add-on of finishing liquids, gives foam with optimal stability. 

Frothing agent produces high blow ratio microbubble foam with a proper balance of wetting penetration and stability... 

One example of the way in which an ore can be purified is the froth flotation method used with ores of copper, zinc, and some other metals. In this method, impure ore taken from the ground is first ground into a powder and then mixed with water and a frothing agent such as pine oil. Then a stream of air is blown through the mixture, causing it to bubble and froth. In the frothing process, impurities such as sand and rock are wetted by the water and sink to the bottom of the container. The metal ore does not adsoib water but does adsorb the pine oil. The oil-coated ore floats to the top of the mixture, where it can be skimmed off. 

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