Separation of anionic surfactant in paste form from its aqueous solutions using foam fractionation

Abstract

Foam fractionation is an effective method for the removal and recovery of a surfactant from water. In this work, removal of an anionic surfactant (i.e. sodium dodecylbenzenesulfonate) was studied, at high concentrations, in a batch foam fractionation column. The anionic surfactant could be separated in a solid/paste form near the top of the column by using this process. High surfactant removal from water was achieved for surfactant concentrations varying from approximately near its critical micelle concentration to six times this concentration. The removal efficiency was reduced in the presence of salt (i.e. NaCl). The surfactant separation was enhanced by increasing the air flow rate. The recovery of surfactant was reasonably good. The recovery of water was good as well. The volume of foam and its age played important roles in the separation efficiency and the surfactant recovery. The adsorption of surfactant and the electric charge at the air–water interface were measured and analyzed to explain the separation efficacy. The bubble size increased with increasing air flow rate, and decreased with increasing surfactant and salt concentrations.