Types of Frothers
All of the frothers presently in use are organic heteropolar compounds. The non-polar organic radical repels water (like that of the flotation collector molecule), while the polar portion attracts water. Until a few years ago, the polar portion of substancially all commercial frothers was a hydroxyl (OH) group, and the hydrocarbon (non-polar) group contained 5-10 carbon atoms. These frothers included:
Amyl Alcohol C5H11OH
Cresol CH3C6H4OH in cresylic acid
Terpineol C10H17OH in pine oil
In such compounds, equilibrium is secured if the molecules are oriented at bubble walls with the polar end adherind to the water phase and the non-polar end turned toward gas phase. Consequently, frother molecules concentrate at liquid-air interfaces, as shown in Figure 4.
Figure 4 – Liquid-Air Interfaces for Frother Molecules
The distribution of frother molecules in the surface layer of water gives that zone the required elasticity to enable the rising bubbles to burst through the top layer of water and emerge at the air-water interface intact and unbroken. If a compound has too limited a solubility in water, it will tend to concentrate as a molecular film at the surface, and the will not be enough molecules within the surface layer to provide the desired elasticity.
Before the development of DOWFROTH 250-D frother, it was generally believed that if a compound had to great a solubility in water, it would be dispersed throughout the bulk of the water and would not concentrate near the air-liquid interface as required. Most early frothing theories had accepted that premise.
However, that premise was proven false in 1951, when the Dow Chemical Company introduced a completely water-solubre frother, designated DOWFROTH 250-D. This product – a poly-propylene glycol ether – is not only an extremely selective frother, but is usually effective at lower concentrations than those required for other “standard” frothing agents. A more detailed discussion of DOWFROTH 250-D appears in the bulletin “DOWFROTH Frothers” Form No. 192-819-1181, available from your Dow salesperson or nearest Dow sales office.
A need to modify the previously mentioned frother theory is evident. The non-polar portion of the molecule is evident. The non-polar portion of the molecule of DOWFROTH 250-D is unique in that it contains hydrophilic oxygen atoms as well as the usual carbon and hydrogen atoms. Apparently the number and location of the oxygen atoms help to solubilize the “non-polar” portion of the molecule. This concept envisages that many of the molecules lie in a flat rather than a perpendicular position at an air-liquid interface, and account for the low concentrations needed to produce a stable the low concentrations needed to produce a stable froth. Extension of this idea of hydrophilic oxygen atoms in the non-polar portion of the frother molecules would account increased selectivity due to less inter-action with the polar collector molecules and with the actual mineral surfaces.
The introduction of this product in 1950-1951 had special significance to the mining industry. It marked the first appearance of a significantly new type of flotation agent having wide application with sulfide minerals.
Since the introduction of DOWFROTH 250-D, the product line has expanded to include several chemical types. The principal products are:
DOWFROTH 200-D DOWFROTH 1263-D
DOWFROTH 250-D DOWFROTH 1400-D
DOWFROTH 1012-D
The present line is sufficient to ensure that a proper frother is available for the great majority of flotation operations. Other products will be produced if a need is demonstrated. These products are discussed in specific detail in the Dow bulletin “DOWFROTH Frothers” Form No. 192-819-1181.
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