Animated Solution for Chemistry - Metallurgy: Which one of the following ores is best concentrated by froth-floatation method ?

Froth Floatation

Welcome to one of the most fascinating and visually satisfying processes in metallurgy: the Froth Floatation Method. Imagine you have a massive pile of crushed rock, and hidden within it are tiny, valuable specks of metal ore. How do you separate the treasure from the trash without picking through it by hand? You use bubbles!

The entire froth floatation process hinges on a simple but brilliant concept called preferential wetting. In a large tank, we mix the crushed ore with water and a special oil, typically pine oil.

Here is the secret: the valuable ore particles (specifically sulphide ores) are hydrophobic. They hate water but love oil. On the other hand, the gangue (the worthless earthy impurities) is hydrophilic. It loves water.

When we vigorously agitate this mixture and blow air through it, a thick froth forms at the top. The oil-coated sulphide ore particles cling to these air bubbles and ride them all the way to the surface, creating a mineral-rich foam that can be easily skimmed off. Meanwhile, the water-soaked gangue particles sink heavily to the bottom of the tank. It is an elegant, physics-driven sorting machine!

Now, let's look at the specific ores given in our problem. The golden rule of froth floatation is that it is almost exclusively used for sulphide ores. Let's break down the chemical identities of our options:

1. Magnetite (): This is an oxide ore of iron. Oxide ores are typically concentrated using magnetic separation or hydraulic washing, not froth floatation.

2. Cassiterite (): This is an oxide ore of tin. Again, being an oxide, it does not have the right surface properties to stick to the oil bubbles.

3. Malachite (): This is a carbonate ore of copper. Carbonates also do not respond well to froth floatation.

4. Galena (): Ah, here we go! Galena is lead sulphide. Because it is a sulphide ore, its surface is naturally hydrophobic and perfectly suited to be wetted by pine oil.

Because Galena is the only sulphide ore in the list, it is the undisputed winner. It will beautifully attach to the froth and rise to the top, leaving the impurities behind.

Whenever you see "Froth Floatation" on an exam, your brain should immediately scream "Sulphide Ores!" It is a high-yield, classic concept that rewards you with quick, confident marks.