In the froth flotation process, how can zinc sulphide and lead sulphide be separated?

a. Using collectors.

b. Adjusting the proportion of oil to water.

c. Using depressants.                                          

d. Using froth stabilizers.

Choose the correct option:
1. (a, b)
2. (b, c)
3. (c, d)
4. (a, d)

HINT: It adjust  the proportional of oil to water.
Froth floatation method is used to extract metal from sulphide ore. ZnS and PbS can be separated by using depressant and adjusting the proportion of oil to water.
Depressant used for this purpose is NaCN. It selectively prevents ZnS from coming to the froth.
The reaction is : ZnS + 4NaCN  Na2[Zn(CN)4] (Soluble complex) + Na2S
Hence, (b) and (c) are correct choices.