Final KB Qs Module 4: Flotation

Question 1

Draw flotation cell and explain flotation in 3 points.

Answer 1

1. Hydrophilic materials remain in suspension whereas hydrophobic minerals attach to air bubbles and enter the froth phase
2. The hydrohilic gangue minerals are removed as the tailing fraction
3. The mineralised froth overflows and is recovered as the concentrate

Question 2

For multiple flotations in a row show how to find Cumulative recovery.

Answer 2

Question 3

Give cumulative recovery vs time curve.

Answer 3

Question 4

Give the assumed first-order reaction Recovery curve fomula.

Answer 4

R = Rmax * [1 – exp(-kt)]

Rmax which is the maximum theoretical flotation recovery

Question 5

What is entrainment?

Answer 5

Non-selective recovery of particles in water recovered to float product. Water recovered because:
- Flow patterns in mixed/mechanical cells

• in pulp zone carried in water layer and wake behind bubbles
• pushed into froth (“bubble swarm effect”)
• carried through froth in Plateau borders

Question 6

What is entrapment?

Answer 6

Entrapment is when the particles are trapped between other particles in the froth – non selective

Question 7

Draw recovery vs particles size for Strongly hydrophobic, Weakly hydrophobic, Entrained.

Answer 7

Question 8

Name reagents that can be added to the slurry to enhance the separation.

Answer 8

1. Collectors
2. Frothers
3. Activators
4. Depressants
5. pH modifiers

Question 8

Explain Frothers purpose in 2 and how they do it.

Answer 8

1. They preserve the small bubbles produced
2. They enable a stable froth to be formed at the surface

Frothers adsorb onto the surface of the bubbles, modifying the surface properties

Question 9

Draw the classic representation of contact angle and surface tension forces.

Answer 9

Question 10

Explain Collectors what they do and how they do it in 2.

Answer 10

Collectors are added to selectively adsorb onto a mineral surface and increase the hydrophobicity

1. Contains a polar “head” which is hydrophilic (Polar head attaches to the mineral surface)
2. Non-polar hydrocarbon “tail” which is hydrophobic

Question 11

Explain Activators what they do.

Answer 11

An activator adsorbs to the surface of a particle, and induces a high affinity to the collector.

Question 12

Explain Depressants what they do.

Answer 12

Depressants adsorb to the surface of hydrophobic minerals in order to render the surfaces hydrophilic. Therefore, separation of two hydrophobic minerals is enhanced.

Question 13

Explain pH modifiers what they do.

Answer 13

The pH is also a factor in the physical adsorption. Adsorption of cationic surfactants, and consequently
flotation is depressed as pH is increased, and vice versa. This affects the ability of the collector to do his job.

Question 14

Give the Size-by-size recovery formula.

Answer 14

Question 15

For Hydrophobic particles give the 3 size regions and comment.

Answer 15

Medium: high recovery, good selectivity
Fine: low recovery since low collision probability
Coarse: low recovery since low attachment/high detachment probability

Question 16

What is the Collision efficiency formula?

Answer 16

Question 17

Draw the Steps in recovery Collison, attachment, stability (detachment)

Answer 17