Question

Describe ‘froth floatation process’ for concentration of sulphide ore.

Answer 1

Froth floatation process:

1) Froth floatation process is based on the principle of difference in the wetting properties
of the ore and gangue particles with water and oil.

2)It is used for the extraction of those metals in which the ore particles are preferentially
wetted by oil and gangue by water

3) This method has been used for removing gangue from sulphide ores. eg. Galena (PbS), zinc blende (ZnS), copper pyrites (CuFeS2), etc.

4)In this method, a suspension of the powdered ore is made with water. To this suspension small quantities of collectors and froth stabilizers are added. Collectors (eg. pine oil, eucalyptus oil, fatty acids, xanthates, etc.) enhance non-wettability of the
mineral particles and froth stabilizers (eg. cresols, aniline) help in stabilization of the
froth. The mineral ore particles become wet by oil, while the gangue (impurities) particles by water.

5)In the floatation tank, a current of compressed air is circulated through the water. A
rotating paddle agitates the mixture and draws air into it. As a result, froth is formed
which carries the mineral particles. The froth is light and is skimmed off. It is then
dried for recovery of the ore particles. The gangue material is wetted by water and
settles at the bottom.

6) In the floatation tank, a current of compressed air is circulated through the water. A
rotating paddle agitates the mixture and draws air into it. As a result, froth is formed
which carries the mineral particles. The froth is light and is skimmed off. It is then
dried for recovery of the ore particles. The gangue material is wetted by water and
settles at the bottom.

7)Sometimes, it is possible to separate two sulphide ores by adjusting proportion of oil to
water or by using ‘depressants’. eg. In case of an ore containing ZnS and PbS, the
depressant used is NaCN. It selectively prevents ZnS from coming to the froth but
allows PbS to come wi th the fr oth, whi ch can be further removed.