(a) Why is it that only sulphide ores are concentrated by froth floatation process ?
or Why is the froth floatation process selected for the concentrated of sulphide ores ?
(b) Which of the following ores can be concentrated by froth floatation method and why ?
` Fe_2O _ 3, ZnS, Al_2O _ 3 `

Explanation

(a) The sulphide ore particles are preferentially wetted by oil, become lighter and thus rise to the surface along with the froth while the gangue particles are preferentially wetted by water, become heavier and thus settle at the bottom of the tank. In this way, sulphide ore particles are separated and hence concentrated from the gangue particles.
(b) Only sulphide ore, i.e., ZnS, is concentrated by froth floatation process.