Question

How do we separate two sulphide ores by Froth Floatation method?

Answer 1

1. Froth floatation method is a technique which is used in order to physically separate the particles of interest from a liquid phase. This technique is based on the difference in ability of air bubbles to adhere selectively to the surface of the particles which is based on their hydrophobicity.
2. Firstly, the ore is crushed and added to water to form slurry. Then, a collector is added, which is oil, it attaches to the surface of the minerals and adds to the property of repelling water to those minerals. When air jets are forced, air bubbles are formed. The air bubbles rise to the surface and have mineral particles sticking to them. This is known as froth.
3. For the separation of two sulphide ores, the proportion of oil and water taken can be adjusted or depressants can be added.
4. Depressants such as $\mathrm{NaCN}$ are used. If an ore contains $\mathrm{ZnS}$ and $\mathrm{PbS}$ then $\mathrm{NaCN}$ is added during the process. $\mathrm{ZnS}$ forms a complex with $\mathrm{NaCN}$ preventing it from coming into a froth. But $\mathrm{PbS}$ is allowed to come into the froth and that’s how it gets separated.