Significance of ion interactions in flotation in saline and brine solutions

There is anecdotal evidence for the significant effects of salt ions on the flotation separation of coal and minerals using process water of high salt content. Examples include flotation of soluble salt minerals such as potash, trona and borax in brine solutions, and coal flotation in saline water. Although some of the effects are expected, some do not seem to be encompassed by classical theories of colloid science. Several experimental and modelling techniques for determining solution viscosity and surface tension, bubble-particle attachment time, contact angle, atomic force microscopy, sum-frequency vibrational spectroscopy and molecular dynamics simulation have been used to provide further information on air-solution and solid-solution interfacial phenomena, especially the interfacial water structure due to the presence of dissolved ions. These studies indicate that the ion specific effect is the most significant factor influencing flotation in saline and brine solutions.