WATER FILM PROPERTIES ON MINERAL SURFACES IN FLOTATION PROCESSES

This paper presents the properties of hydration layers on mineral surfaces and their importance in the enrichment by flotation processes. Water layers possessing different properties from those in bulk water may be spontaneously formed due to polar and dispersive interactions of the molecules on both hydrophobic and hydrophilic surfaces. The layers of the highest binding energy (per molecule) constitute an energy barrier against the approach of an air bubble, and hence they create a relatively low flotability of even hydrophobic minerals. It is stated that for good flotability the specific properties of vicinal water should be changed to achieve the properties of bulk water. This may be done by the addition of suitable components (collectors) which eliminate polar interactions and reduce the dispersive interactions to 25-35 mJ m-2. The structure and thermodynamic properties of hydration layers formed on hydrophobized mineral surfaces become similar to those in bulk water, and they may be spontaneously disrupted. The work of destruction of such layers becomes comparable to the work of water cohesion. This results in a significant flotability of minerals.