Question

Which of the following statements is correct about the role of collectors added during the froth floatation process?
A.Collectors enhance the non-wettability of ore particles.
B.Collectors enhance the wettability of gangue particles.
C.Collectors help in separating two sulphide ores present in the mixture.
D.Collectors help ore particles to settle down below the froth.

Answer 1

Hint: Froth floatation process is a method of concentration of the ore. The principle of the froth floatation process is based on the preferential wettability of mineral particles by oils and gangue particles by water. Pine oils are usually used as collectors in this process. Depressants like NaCN are used to separate the two sulphide ores.

Complete step by step answer:
Removal of unwanted particles of gangue from the ore is known as the concentration of the ore. It is also known as dressing or benefaction of the ore. The Froth floatation process is a method of concentration of sulphide ores.
First, the powdered ore is mixed with water and a suspension is made. This is followed by the addition of collectors and froth stabilizers.
Examples of collectors used in the process are pine oils, fatty acids, and xanthates. Froth stabilizers used are cresol and aniline. They stabilize the froth. So, Collectors enhance the non-wettability of the ore particles. Hence, statement (A) is correct but statement (B) is not correct.
Froth is formed by agitating the above mixture using a rotating paddle. The mineral particles get attached to the froth. This floats on top of the water and is skimmed off. Therefore, statement (D) is incorrect.
Separation of two sulphide ores is possible by using depressants and not collectors. Depressants selectively prevent one of the sulphide ores from coming to the froth while allowing the other. If the separation is between ZnS and PbS, NaCN is used as the depressant. It prevents ZnS from coming to the froth. Hence, statement (C) is incorrect.
Therefore, the correct answer is (A).


Note:
The froth floatation process selectively separates the hydrophobic minerals from the hydrophilic gangue particles. Some minerals have naturally hydrophobic surfaces and do not require the addition of collectors.
Collectors are not to be confused with activators. Activators are called the friends of collectors. They activate the mineral surface towards the action of collectors.