Iron ore beneficiation by flotation is a process used to separate and concentrate iron ore from gangue minerals (unwanted minerals) by exploiting differences in their surface properties. Here’s a detailed breakdown of the process:
1. Principle of Flotation
– Flotation relies on the hydrophobicity (water-repelling nature) of mineral surfaces.
– Iron ore minerals (e.g., hematite, magnetite) can be made hydrophobic using specific reagents, allowing them to attach to air bubbles and float, while hydrophilic gangue (e.g., silica, alumina) sinks.
2. Key Steps in Iron Ore Flotation
# (a) Grinding & Liberation
– Crushed iron ore is ground to fine particles (~100–150 µm) to liberate iron-bearing minerals from gangue.
– Over-grinding should be avoided to prevent slimes formation, which reduces flotation efficiency.
# (b) Conditioning with Reagents
– Collectors: Organic reagents like fatty acids (oleic acid), hydroxamates, or sulfonates selectively coat iron minerals, making them hydrophobic.
– Depressants: Sodium silicate, starch, or dextrin suppress silica/alumina flotation.
– Frothers: Pine oil or MIBC (methyl isobutyl carbinol) stabilize air bubbles for better mineral attachment.
– pH Modifiers: Lime or soda ash adjust pH (typically 7–10 for hematite flotation).
# (c) Froth Flotation
– Air is bubbled through the slurry in flotation cells.
– Hydrophobic iron particles attach to bubbles and rise as froth.
– Froth is skimmed off, while hydrophilic gangue remains in the slurry.
# (d) Concentrate & Tailings Separation
– The floated concentrate is dewatered (using filters or thickeners).
– Tailings (wa
) are discarded or further processed for residual iron recovery.
3. Types of Iron Ore Flotation
– Direct Flotation: Iron minerals float while silicates sink (common for hematite).
– Reverse Flotation: Silica/alumina float while iron sinks (used when gangue is more floatable).
4. Challenges & Solutions
| Challenge | Solution |
|———–|———-|
| Slimes reduce efficiency | Desliming via hydrocyclones |
| Complex mineralogy | Selective reagents & depressants |
|