Development of a multistaged foam fractionation column

Surface active materials stabilise foam by adsorption at the gas/liquid interface. In foam fractionation, the foam is condensed to give a “foamate” liquid rich in surfactant. We have developed equipment and a process able to supply a number of stages of separation, working with an inert stripping gas. We have tested this with aqueous surfactant, and also with a surfactant which extracts and concentrates an organic solute. The measured liquid compositions are in good agreement with a model which describes the equilibrium using an adsorption isotherm, and which makes a mass balance for each stage in the column. The effect of liquid reflux is shown to be important. Possible applications of this process are in the fields of water purification and the recovery of components such as proteins from solution.