4. Flotation practice

In industries froth flotation is a continuous process involving a regular flow of feed pulp and separation of minerals into the regular respective product streams. The major elements of flotation operations are:


#### 4.1 Importance of reagent conditioning

As the choice of specific reagent for a given ore is difficult and challenging, so is the selection of quantity, mode and time of addition of the reagents. The selection of reagent quantity does not pose much problem as a more or less precise reagent type and quantity for a specific ore system are available through reagent manufacturers and practising personnel. Whether the total quantity is to be added at different stages is a matter of difficult choice and is to be based upon carefully laboratory investigation regarding the case of floatability of minerals.

Adsorption of surfactant is in direct correlation with the solid-water-air interfaces as the main role of surfactants is to modify the properties of interfaces for increased adsorption of reagents and enhanced flotation process. Modified starches and blended polymers can be better alternatives to normal starches due to their higher solubility and better flocculation action.

#### 4.2 Applications of flotation other than mineral industries

Application of flotation has been envisaged in other areas besides mineral engineering. Some of the examples are:

3.3.3 Dispersants

Table 2.

Modifying agents

Frothers All iron

Surfactants and Detergents

oxides, silica, alumina, phosphorus

Direct and reverse iron ore flotation

3.3.4 pH regulators

and acids.

22

These are used to minimize the deleterious effect of undesired slime coating

Reagents Application Classification Composition Functioning process

1:2 Mass ratio of 4:1 ether monoamine to nonylphenol

The reagents are used as undiluted and also prepared as solution in H2O

Slurry Dry

5–10% solution 10% solution Solution Solution of 0.30–0.80 kg/ton Solution of 0.5–1.2 kg/ton

hydrophobicity Decreased surface tension at liquid-gas interface and reduce froth depth

Provides most viscous, stable froth, have collecting action Less viscous but stable froth, have collecting

Fine, fragile froth; inert

pH regulator; disperses gangue slimes Activates silica with fatty acid collectors Disperses siliceous gangue slimes; Fragile froth Depress iron-bearing

action

to rubber Slightly stable froth Slightly stable froths Fine-textured froth; frequently used with ores containing slimes

minerals

ether amine

etheramine

fatty alcohol

collectors

250, DF 450 5. Fuel oil

7. MIBC

Ca(OH)2 2. Soda ash, NaOH Caustic soda, NaOH Sulphuric acid, H2SO4 3. Ca2+ (CaCl2), Mg2+ (MgCl2)

4. Na2SiO3 5. Starch, dextrin

gum, PAM

Reagent types used in mineral oxide industries (specifically for iron ores).

6. Aliphatic alcohols,

1. Lime (CaO) or slaked lime

Quebracho, tannic acid, gaur

with fatty acids 2. Fatty acids (anionic collectors) and amphoteric

4. Non-phenol ethoxylated with ethylene oxide and

5. Mixture of amine and hydrochloric acid

6. N-dodecyl ethylene diamine (mixture of 1-bromododecane, ethanol and ethylenediamine 7. Mixture of primary ether monoamine, oxyethylated nonylphenol and oxyethylated

1. Non-polar oils emulsified

1. Pine oil (alpha-terpineol) 2. Cresylic 'acid' (cresols) 3. Polypropylene glycols 4. DF (Dow Froth) 200, DF

The pH regulators help in maintaining adequate pH of the pulp, which determines the selective separation of minerals. These are achieved by variety of bases

(Tables 2 and 3), e.g. sodium silicate and sodium metasilicate.

