Question

A.What is the role of depressant in the froth floatation process?
B.What is the role of silica in the metallurgy of copper?

Answer 1

Hint:Depressants are used in the separation of the floatation species formed during the froth floatation process. During metallurgy of copper, Silica is used to remove the sulphur impurities that are present in the ore of copper.

Complete step by step solution:
Part A
Froth floatation method is used to separate the required mineral from the mixture by creating froth. The mineral gets separated on this froth. During the process of froth floatation various chemicals are required to be added for the maintenance of proper froth and to increase the quality. The chemicals used are named as: collector, frother, regulator, activator, depressant and pH Modifier.
A depressant or deactivator is a species which increases the action of a collector for one particular mineral but simultaneously decreases the selectivity of formation of froth by any other material. This helps in the formation of froth of only required minerals.
Part B
Silica is used in the smelting of copper during the metallurgy of copper. Smelting is the process of extracting metal from its ores. The concentrated ore is heated with silicon dioxide which is also known as silica in the presence of calcium carbonate. In this way a sulphide ore of copper is formed. Most of the sulphide present gets removed as sulphur dioxide and the rest of the sulphur forms copper sulphide. The pure metal can be obtained by reacting it with oxygen.

Note:
The depressants are classified in two types as: inorganic depressants such as zinc sulphate and organic depressants such as starch. The copper obtained from heating copper sulphide with air is known as blister copper because of its texture. Sulphur dioxide bubbles out leaving such texture.