Froth flotation

Forth Flotation

1. Froth F lotation

2. Presented By: M. Ali Mohsin (MME-16-04)

3. Flotation Flotation is a selective process and can be used to achieve specific separation from complex ores such as lead-zinc copper-zinc etc Flotation is the most important and versatile mineral processing technique.

4. Principle Of Flotation Flotation is a physico-chemical separation process that utilizes the difference in surface properties of the valuable minerals and the unwanted minerals. This process commences with comminution . The ore is ground to fine powder and wetted with water to form a slurry.

5. Separation mechanisms The process of separation of mineral includes three important mechanisms which are : True flotation, i.e. selective attachment to air bubbles. Entrainment in the water which passes through the froth. Aggregation, i.e. physical entrapment between the particles attached to air bubbles in froth. True flotation dominates the recovery of valuable minerals and the other two decide the separation efficiency between the valuable and the gangue.

6. Ways of flotation There are two ways of flotation: Direct flotation Reverse flotation Direct flotation in which the mineral is attached to the froth and the gangue remains in the tailing. Reverse flotation in which the gangue is attached to the froth and the minerals remains in the tailing.

7. Classification of minerals Polar Non-polar All minerals are classified into polar or non-polar types according to their surface characteristics. Since water is a polar molecule, polar mineral surfaces tend to be hydrophilic. Whereas, nonpolar mineral surfaces tend to be hydrophobic. The goal is to make the mineral surface hydrophobic so the minerals will attach to the bubbles in the froth.

8. Collectors Frothers These are organic compounds used for enhancing the hydrophobicities of the selected minerals, by adsorption of its molecules or ions to the mineral surface and reducing the stability of the hydrated surface separating the mineral surface and air bubbles. Frothers are added to stabilize bubble formation in the pulp phase, to create a reasonably stable froth to allow selective drainage from the froth of entrained gangue

9. Regulators Activators Regulators, or modifiers, are used extensively in flotation to modify the action of the collector, either by intensifying or by reducing its water-repellent effect on the mineral surface. These reagents activates the mineral surface towards the action of the collectors, by altering their chemical properties. Thus, they are referred as the friends of collectors.

10. Depressants pH Modifiers These reagents deactivate the mineral surface towards the action of collectors, by altering their chemical properties. Hence, they are referred as the enemies of the collectors. There are mainly two categories of depressants, Inorganic (e.g. sodium cyanide, zinc sulphate etc.) Organic (or polymeric e.g. starch, tannin etc.) The selectivity in floatation process is dependent on delicate balance between the reagent concentration and the pH. This pH factor is modified with the help of the substances called pH Modifiers. Alkalinity in solution is maintained by the addition of lime and sodium carbonate. Sulphurous and sulpuric acids are used to lower the pH