Question

The process involved in metallurgy are the concentration of the ore, isolation of the metal from its concentrated ore and purification of the metal.

a) Froth floatation method is an ore concentration method. What is the principle behind the process?

b) What is the role of limestone (CaCO₃) in the extraction of iron?

c) Monds process is used for refining of Ni and Van Arkel method is used for refining Zr (Zirconium). Write one similarity between these processes.

Answer 1

a) The principle behind froth floatation is adsorption. The ore particles are preferentially wetted by the oil and are carried to the surface by the froth. The gangue material wetted by water sinks to of the tank. The froth is light and is skimmed off.

b) Inside the blastfumace lime stone is decomposed to CaO which acts as a basic flux and removes the silicate impurity (acidic gangue) of the ore as calcium silicate slag. The slag is in molten state and separates our from iron.

CaCO₃ \(\overset{Heat}{\longrightarrow}\) CaO+CO₂

CaO+SiO₂ → CaSiO₃

c) Vapour phase refining techniques. The metal is converted into its volatile compound and collected elsewhere. It is then deèomposed to give pure metal.