**4. Classification of adsorptive bubble separation method and classification**

### **4.1 Collectors and mechanism of action**

When the particles of interest (colligend) do not have surface active properties of their own, they are made effective surface active or collected by adding to the collectors in an adsorptive bubble separation process. Ionic surfactant travels to the surface of gas bubbles increasing through the liquid during ion flotation, and the surface becomes charged [8]. The oppositely charged substance of interest (Colligend) adsorbs to the bubble interface as a counter ion, forming an electrical double layer. Because of the foam's high surface area to liquid volume ratio, the liquid that emerges from its breakdown is much more concentrated in the ion than the original solution. The colligend should be specific for the interface of a charged surfactant. Surfactant molecules have two parts: one is hydrophobic, while the other is hydrophilic. The hydrophilic portion comes outside, while the hydrophobic part stays within. The hydrophilic component was applied to the substance of interest and taken away at the foam bubble interface (**Figure 1**).

Enantiomeric mixtures are separated using chiral collectors. These chiral molecules are known to interact with analytes in a variety of ways, including ligand exchanged interactions, hydrophobic inclusion complexation, and hydrogenbonding interactions. Colligend must be used as a foaming agent so chiral collectors are not foaming agents. Enantioselectivity can be caused by a disparity in the chiral collector's and two enantiomers' reaction mechanism.

**Figure 1.**

*Classification of adsorptive bubble separation method classification.*
