Question

Froth floatation process used for concentration of sulphide ores is:
A. It is based on the difference in wettability of different minerals
B. It uses sodium ethyl xanthate (${{C}_{2}}{{H}_{5}}OC{{S}_{2}}Na$) as a collector
C. It uses $NaCN$ as a depressant in the mixture of $ZnS$ and $PbS$ when $ZnS$ forms a soluble complex and $PbS$ forms froth.
D. All the above statements are correct

Answer 1

Froth flotation is defined as a process for selectively separating hydrophobic materials from hydrophilic.The hydrophobicity differences between valuable minerals and waste gangue are increased through the use of surfactants and wetting agents.

Complete step by step answer:
Froth flotation is a process for selectively separating hydrophobic materials from hydrophobic. In this method the advantage is taken of the preferential wetting of the ore by an oil comparative to other oils. Then ethyl xanthate (${{C}_{2}}{{H}_{5}}OC{{S}_{2}}Na$) is added as a collector which attracts the remaining particles of the sulphide ores and binds the sulphide ore and oil mixture together.
During the flotation process of some ores where there are extra unwanted sulphide ores are present some depressants are added to reduce the availability of these ores in suspension. These substances are added which activate or depress the flotation property of the minerals and in turn help in the separation of minerals present in the ore. For example, galena $PbS$ is usually associated with sphalerite $(ZnS)$ and pyrites are depressed using $NaCN$.
So, the correct answer is “Option D”.

Note: In this method the finely ground ore is taken in a tank containing water and 1% of pine oil or turpentine oil.
Then a strong current of air is blown through the suspension in the tank, producing a very heavy froth or foam on the surface of the suspension. The metal sulphide is wetted or attracted by the oil but the gangue particles which are water-loving are not wetted by the oil and the sulphide-oil mixture is then carried to the surface by films of oil. During this process the froth is skimmed off, the gangue settles down on the bottom or remains underneath the froth. The sulphide ores of copper, zinc and lead are concentrated using this method.