Market Survey on Copper - Indian Bureau of Mines

of frother molecule leads to its adsorption i.e. molecules concentrate in the
surface layer with non-polar groups oriented towards the air and polar group
towards the water. Frothing action is due to the ability of frother to adsorb on
the air-water interface, because of its surface activity and to reduce the surface
tension, thus, stabilising the air bubble. Frother must be to some extent soluble
in water. The acids, amines and alcohols are the most widely used frothers
since they have practically no collection properties.
Pine oil which contains aromatic alcohols has been widely used as
frother in copper ore flotation plants. Cresol (cresylic acid: CH3C6 H4OH) is
also widely used.
A wide range of synthetic frothers, based mainly on high molecular
weight alcohols is now in use in many plants. A typical synthetic frother is
Dowfroth-250, which is being widely used in copper flotation plants.
Combination of two or more frothers is also reported to give better
performance.
iii) Regulators: Regulators or modifiers are widely used in copper ore
flotation to modify the action of collector either by intensifying or reducing its
water repellent effect on the mineral surface. They, thus, make collector action
more selective towards certain minerals. Regulators can be classified as
activators, depressants, dispersants and pH modifiers.
iv) Activators: These reagents modify the mineral surfaces so as to make
them hydrophobic and susceptible to collector action. Activators are generally
soluble salts which ionize in solution and the ions then react with the mineral
surface. Activators are occasionally used in copper flotation. Oxide minerals of
copper like azurite, malachite, etc. sluggishly float with collectors and need
large dosages. Such minerals are activated by use of sodium sulphide or sodium
hydrosulphide. The sodium sulphide should be added in stages and its amount
should be carefully controlled, as excess amount depresses even activated oxide
minerals and also the sulphide minerals.
v) Depressants: Depressants are employed to ensure selective flotation by
rendering certain minerals hydrophilic (water avid), preventing their flotation.
There are many types of depressants and their actions are complex. Cyanides
are widely used in copper-zinc and copper pyrite separation. Sodium cyanide is
more commonly used depressant.
The depressing action of cyanide depends on its concentration, pH value
and length of xanthenes hydrocarbon chain. Depressing effect of cyanide ion
increases with pH. It is maximum (100%) at pH 13 and minimum (0.06%) at
pH