ANS:B - wetting characteristics

wetting characteristics

Explanation:

Froth flotation separates ore particles based on their different surface properties, specifically their wetting characteristics, allowing hydrophobic particles to attach to air bubbles and float, while hydrophilic particles sink. Wetting characteristics refer to how a material interacts with a liquid, particularly regarding its ability to be wetted (or not wetted) by that liquid. This property is crucial in processes like froth flotation. Here’s a breakdown:

1. Hydrophobic vs. Hydrophilic

• Hydrophobic Materials: These do not readily interact with water and resist wetting. In froth flotation, hydrophobic ore particles attach to air bubbles and float to the surface.
• Hydrophilic Materials: These easily interact with water and are wetted by it. Hydrophilic particles tend to sink in the flotation process.

2. Surface Tension and Contact Angle

• Surface Tension: The cohesive force between liquid molecules affects how a liquid interacts with solid surfaces. Lower surface tension can improve the wetting of hydrophobic materials.
• Contact Angle: This is the angle formed at the liquid-solid interface. A smaller contact angle indicates better wetting, while a larger contact angle indicates hydrophobicity. For effective flotation, hydrophobic particles typically have higher contact angles.

3. Role in Froth Flotation

• Selective Separation: By modifying the surface properties of ore particles (often using surfactants), flotation can selectively separate valuable minerals from gangue based on their wetting characteristics.
• Bubble Attachment: Hydrophobic particles adhere to air bubbles and rise to the surface, forming a froth, while hydrophilic particles remain in the slurry.

Summary

Wetting characteristics are essential in processes like froth flotation, where the ability of ore particles to be hydrophobic or hydrophilic determines their separation. This property is manipulated to enhance the efficiency of mineral extraction and recovery.