Investigation on the Stability of Liquid Surfactant Membrane

In the process of separation of a component from a liquid by liquid surfactant membrane, an emulsion system of W_1/O/W_2 is formed. In this investigation, it is found that the breakage and svelling of this type of emulsion system are affected by the concentration of the surfactant, the applied external shear stress and difference in osmotic pressures of the internal and external aqueous phasses. Their mechanisms are discussed. From the arrangement of surfactant molecules within the liquid film, the following conclusions are obtained. If the concentration of surfactant is too low, the W_1/O emulsion drop will break easily; if the concentration is too high, then the W_1/O emulsion drops will swell easily. The optimum concentration of surfactant in the liquid emulsion membrane can be calculated. Experiments were carried out to measure the factors affecting the percentage breakage and swelling. They are in close agreement with that deduced from proposed mechanism.