Froth flotation, based on chemical phenomena occurring at the interfaces including solid/water and air/water, becomes an efficient means of separating heterogeneous mixtures of finely subdivided solids with bubbles floating and is widely used within the primary mineral and chemical industries. In the process of froth flotation, collectors are always used to adjust the hydrophobicity of mineral surface through selective adsorption. Nowadays, most of soluble salts, especially potash, are produced through froth flotation. Although the flotation systems of soluble salts are complicated in the actual production, they are mainly comprised of salt crystal, collector, bubbles and saturated salt solution with high ionic strength. Actually, the soluble salt flotation is the results of the interaction among these four components. Thus, lots of researches about flotation mechanism of soluble salts focus on these interactions. This paper summarizes the recent progress in the flotation mechanism of soluble salts with high ionic strength. The solution chemistry of soluble salts, colloidal properties of collector in saturated salt solution, adsorption behaviors of collectors on surface of salt crystal, interfacial properties of salt crystal/saturated salt solution and the role of bubbles in the froth flotation are reviewed emphatically. Finally, the trend for future research on flotation mechanism of soluble salts is also prospected.

Contents
1 Introduction
2 Solution chemistry of soluble salts
2.1 Structure of hydrated ions
2.2 Viscosity
3 Properties of collector in solution with high ionic strength
3.1 Krafft point
3.2 Surface activity and aggregation behaviors
4 Selective adsorption of collector
5 Interfacial properties of mineral crystal/saturated salt solution in high ionic strength environment
5.1 Surface charge of crystal surface
5.2 Wetting characteristics of crystal surface
6 The role of bubbles in flotation system with high ionic strength
7 Conclusion