Q.Explain the purification of sulphide ore by Froth floatation method.

Froth flotation is the standard concentration method for sulphide ores.

Froth flotation works because sulphide-ore particles are preferentially wetted by an oil/collector (e.g. pine oil, xanthates) and NOT by water, while the gangue (impurities) is wetted by water. When air is blown through a suspension of the finely powdered ore in water containing a collector and a frothing agent, the sulphide particles stick to the rising air bubbles and are carried up as froth, which is skimmed off; the water-wetted gangue settles at the bottom. This selective-wetting behaviour is characteristic of sulphide ores (e.g. galena $PbS$, zinc blende $ZnS$, copper pyrites $CuFeS_2$), whic …

Froth flotation is used to concentrate sulphide ores by exploiting the difference in wettability of the ore particles and the gangue.

Apparatus/diagram description (labelled parts):

• A flotation cell/tank containing a suspension of finely powdered ore in water.
• A small quantity of pine oil (or other collector such as xanthates) is added, which coats/wets the sulphide ore particles preferentially, making them water-repelling (hydrophobic); the gangue particles remain water-wetted (hydrophilic).
• Air is blown/agitated vigorously into the mixture through a rotating paddle/impeller (or an air jet), generating a froth of fine air bubbles.
• The hydrophobic ore particles attach themselves to the air bubbles and are carried upward, forming a stable mineral-rich froth layer at the surface of the tank.
• The froth (carrying the concentrated sulphide ore) is continuously skimmed/overflowed off the top of the cell and collected. …

Sulphide ores are concentrated by the froth floatation process, which exploits the preferential wetting of sulphide particles by oil.

Sulphide ore particles are preferentially wetted by oil (they are hydrophobic), while the gangue is wetted by water. In froth floatation, the powdered ore is agitated with water, pine oil, and air; the sulphide particles cling to the oily froth and float to the top, where they are skimmed off, separating them from the gangue.

• Gravity separation suits denser oxide ores. …

Sulphide ores are concentrated by the froth flotation method, which exploits the preferential wetting of sulphide particles by oil/pine oil (and by frothing agents) over water.

In froth flotation, the finely powdered sulphide ore is mixed with water and a small amount of pine oil/collector (e.g. xanthates), then agitated with air. The sulphide ore particles are preferentially wetted by the oil and stick to the air bubbles, rising to the surface as a stable froth that is skimmed off. The gangue (impurity, e.g. silica), being preferentially wetted by water, settles at the bottom.

…

Sulphide ores are concentrated by the froth floatation process, which exploits the preferential wetting of sulphide particles by oil.

The froth floatation process is used to concentrate sulphide ores (e.g. galena PbS, zinc blende ZnS, copper pyrites). The finely ground ore is suspended in water with pine oil (collector) and air is blown through. The sulphide ore particles are preferentially wetted by the oil and rise up with the froth, while the gangue (wetted by wate …

In the froth flotation process, sodium cyanide (NaCN) acts as a depressant — it selectively holds back one sulphide (ZnS) so that another sulphide (PbS) can be concentrated first. The correct alternative is therefore (c) depressant.

Froth flotation is used to concentrate sulphide ores. The finely powdered ore is suspended in water with a little oil, and air is blown through so that the water-repellent mineral particles rise with the froth. Different reagents play different roles:

• Collectors (e.g. pine oil, fatty acids, xanthates) — make the desired mineral particles water-repellent (hydrophobic) so they attach to the air bubbles and rise as froth.
• Froth stabilisers (e.g. cresols, aniline) — stabilise the froth so that it does not collapse too soon.
• Depressants — selectively prevent one sulphide mineral from forming froth so that it stays behind in the gangue. …

Froth flotation works precisely because sulphide-ore particles are oil-loving (not water-loving), a property gangue particles lack.

Sulphide ore particles have a natural surface affinity for oil (they are preferentially wetted by oil rather than water), while the gangue (impurity) particles are preferentially wetted by water. In froth flotation, the powdered ore is agitated in water with a pine-oil/collector; sulphide mineral particles get coated with oil and stick to the air bubbles, rising to the surface as a stable froth, which is skimmed off, while the water-wetted gangue settles at the bottom. Since this method relies specifically on differential wettability by oil vs water — a property characteristic of sulphide minerals — froth flotation is uniquely …