Removal of Materials from Aqueous Solution by Foam Separation

Abstract

Foam separation can separate and remove dissolved substances from an aqueous solution together with surfactants. When bubbles are introduced into a solution using a device, an adsorption monolayer of surfactant (including amphiphilic substances) is formed at the bubble surface. The bubbles float to the interface while adsorbing substances and become foams. The substances are concentrated with accompanying the drainage progresses during the rise of the foam in the long tube, and the substances in the aqueous solution are separated as foam. The removal mechanism is adsorption between the surfactant and the substance at the gas-liquid interface, and is often based on electrostatic interaction. Regarding the removal of metal ions, it was found that there is a correlation between the size of the hydrophilic group of the surfactant and the crystal ionic radius of the metal ion. Studies of ionic dye removal in foam separation systems have shown that ionic dyes can be removed using surfactants with opposite charges. On the other hand, amphoteric surfactants can remove both anionic and cationic dyes. Finally, I report on a study in which the foam separation method is applied to cleaning organs for the purpose of decellularization.

graphical abstract