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The flotation of graphite particles in aqueous solutions of inorganic electrolytes was shown to depend on both the nature of the cation/anion pair and the range of the bubble/particle electrostatic interaction. For several electrolytes, as the reduction in the Debye length of the solution approached the decay length of the hydrophobic attraction, then flotation began to occur. Also using earlier reported data, it was possible to relate the flotation to surface tension/electrolyte concentration gradients and bubble coalescence behavior of the different electrolyte solutions. Higher flotation recoveries were attributed to an increased collision probability between the graphite particles, a higher concentration of small noncoalescing bubbles, and an increased stability of the froth. Furthermore, it has also been shown from previous studies that increasing electrolyte concentration causes a decrease in gas solubility. In fact, gas solubility has been shown to be dependent on the hydration entropy of the cation. This phenomenon was explained in terms of competitive utilization of water molecules in the hydration of cations and a consequent loss or gain in gas solubility. Overall, it was shown that a reduction in the electrostatic interactions between particle and bubble assisted flotation. However, in addition, an increase in flotation performance resulted from the inhibition of coalescence of bubbles, which is also linked with dissolved gas concentration gradients (structural differences at the air/solution interfacial region relative to the the bulk electrolyte solution).

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