how does a ‘collector’ separate the ore from gangue in the froth floatation process?

Froth flotation is a process for separating minerals from gangue by taking advantage of differences in their hydrophobicity. Hydrophobicity differences between valuable minerals and waste gangue are increased through the use of surfactants and wetting agents. The selective separation of the minerals makes processing complex (that is, mixed) ores economically feasible.
Collectors either chemically bond (chemisorption) on a hydrophobic mineral surface, or adsorb onto the surface in the case of, for example, coal flotation through physisorption. Collectors increase the natural hydrophobicity of the surface, increasing the separability of the hydrophobic and hydrophilic particles.


The hydrophobic and hydrophilic character of the surfaces can be changed using
surfactants. A surfactant which makes the surface hydrophobic, is called a
collector and possess at least one non-polar group. The non-polar group is usually
represented by a hydrocarbon but it may be a fluorocarbon or a siloxane.

Owing to chemical, electrical, or physical attraction between the polar groups and
the surface sites, the collectors adsorb onto the particles with their non-polar
groups oriented towards the bulk solution, thereby imparting hydrophobicity to
the particles.